Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

74 files changed, 33942 insertions, 0 deletions

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
new file mode 100644
index 000000000..32e35a858
--- /dev/null
+++ b/drivers/xen/Kconfig
@@ -0,0 +1,369 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menu "Xen driver support"
+	depends on XEN
+
+config XEN_BALLOON
+	bool "Xen memory balloon driver"
+	default y
+	help
+	  The balloon driver allows the Xen domain to request more memory from
+	  the system to expand the domain's memory allocation, or alternatively
+	  return unneeded memory to the system.
+
+config XEN_BALLOON_MEMORY_HOTPLUG
+	bool "Memory hotplug support for Xen balloon driver"
+	depends on XEN_BALLOON && MEMORY_HOTPLUG
+	default y
+	help
+	  Memory hotplug support for Xen balloon driver allows expanding memory
+	  available for the system above limit declared at system startup.
+	  It is very useful on critical systems which require long
+	  run without rebooting.
+
+	  It's also very useful for non PV domains to obtain unpopulated physical
+	  memory ranges to use in order to map foreign memory or grants.
+
+	  Memory could be hotplugged in following steps:
+
+	    1) target domain: ensure that memory auto online policy is in
+	       effect by checking /sys/devices/system/memory/auto_online_blocks
+	       file (should be 'online').
+
+	    2) control domain: xl mem-max <target-domain> <maxmem>
+	       where <maxmem> is >= requested memory size,
+
+	    3) control domain: xl mem-set <target-domain> <memory>
+	       where <memory> is requested memory size; alternatively memory
+	       could be added by writing proper value to
+	       /sys/devices/system/xen_memory/xen_memory0/target or
+	       /sys/devices/system/xen_memory/xen_memory0/target_kb on the
+	       target domain.
+
+	  Alternatively, if memory auto onlining was not requested at step 1
+	  the newly added memory can be manually onlined in the target domain
+	  by doing the following:
+
+		for i in /sys/devices/system/memory/memory*/state; do \
+		  [ "`cat "$i"`" = offline ] && echo online > "$i"; done
+
+	  or by adding the following line to udev rules:
+
+	  SUBSYSTEM=="memory", ACTION=="add", RUN+="/bin/sh -c '[ -f /sys$devpath/state ] && echo online > /sys$devpath/state'"
+
+config XEN_MEMORY_HOTPLUG_LIMIT
+	int "Hotplugged memory limit (in GiB) for a PV guest"
+	default 512
+	depends on XEN_HAVE_PVMMU
+	depends on MEMORY_HOTPLUG
+	help
+	  Maximum amount of memory (in GiB) that a PV guest can be
+	  expanded to when using memory hotplug.
+
+	  A PV guest can have more memory than this limit if is
+	  started with a larger maximum.
+
+	  This value is used to allocate enough space in internal
+	  tables needed for physical memory administration.
+
+config XEN_SCRUB_PAGES_DEFAULT
+	bool "Scrub pages before returning them to system by default"
+	depends on XEN_BALLOON
+	default y
+	help
+	  Scrub pages before returning them to the system for reuse by
+	  other domains.  This makes sure that any confidential data
+	  is not accidentally visible to other domains.  It is more
+	  secure, but slightly less efficient. This can be controlled with
+	  xen_scrub_pages=0 parameter and
+	  /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
+	  This option only sets the default value.
+
+	  If in doubt, say yes.
+
+config XEN_DEV_EVTCHN
+	tristate "Xen /dev/xen/evtchn device"
+	default y
+	help
+	  The evtchn driver allows a userspace process to trigger event
+	  channels and to receive notification of an event channel
+	  firing.
+	  If in doubt, say yes.
+
+config XEN_BACKEND
+	bool "Backend driver support"
+	default XEN_DOM0
+	help
+	  Support for backend device drivers that provide I/O services
+	  to other virtual machines.
+
+config XENFS
+	tristate "Xen filesystem"
+	select XEN_PRIVCMD
+	default y
+	help
+	  The xen filesystem provides a way for domains to share
+	  information with each other and with the hypervisor.
+	  For example, by reading and writing the "xenbus" file, guests
+	  may pass arbitrary information to the initial domain.
+	  If in doubt, say yes.
+
+config XEN_COMPAT_XENFS
+	bool "Create compatibility mount point /proc/xen"
+	depends on XENFS
+	default y
+	help
+	  The old xenstore userspace tools expect to find "xenbus"
+	  under /proc/xen, but "xenbus" is now found at the root of the
+	  xenfs filesystem.  Selecting this causes the kernel to create
+	  the compatibility mount point /proc/xen if it is running on
+	  a xen platform.
+	  If in doubt, say yes.
+
+config XEN_SYS_HYPERVISOR
+	bool "Create xen entries under /sys/hypervisor"
+	depends on SYSFS
+	select SYS_HYPERVISOR
+	default y
+	help
+	  Create entries under /sys/hypervisor describing the Xen
+	  hypervisor environment.  When running native or in another
+	  virtual environment, /sys/hypervisor will still be present,
+	  but will have no xen contents.
+
+config XEN_XENBUS_FRONTEND
+	tristate
+
+config XEN_GNTDEV
+	tristate "userspace grant access device driver"
+	depends on XEN
+	default m
+	select MMU_NOTIFIER
+	select FIND_NORMAL_PAGE
+	help
+	  Allows userspace processes to use grants.
+
+config XEN_GNTDEV_DMABUF
+	bool "Add support for dma-buf grant access device driver extension"
+	depends on XEN_GNTDEV && XEN_GRANT_DMA_ALLOC
+	select DMA_SHARED_BUFFER
+	help
+	  Allows userspace processes and kernel modules to use Xen backed
+	  dma-buf implementation. With this extension grant references to
+	  the pages of an imported dma-buf can be exported for other domain
+	  use and grant references coming from a foreign domain can be
+	  converted into a local dma-buf for local export.
+
+config XEN_GRANT_DEV_ALLOC
+	tristate "User-space grant reference allocator driver"
+	depends on XEN
+	default m
+	help
+	  Allows userspace processes to create pages with access granted
+	  to other domains. This can be used to implement frontend drivers
+	  or as part of an inter-domain shared memory channel.
+
+config XEN_GRANT_DMA_ALLOC
+	bool "Allow allocating DMA capable buffers with grant reference module"
+	depends on XEN && HAS_DMA
+	help
+	  Extends grant table module API to allow allocating DMA capable
+	  buffers and mapping foreign grant references on top of it.
+	  The resulting buffer is similar to one allocated by the balloon
+	  driver in that proper memory reservation is made by
+	  ({increase|decrease}_reservation and VA mappings are updated if
+	  needed).
+	  This is useful for sharing foreign buffers with HW drivers which
+	  cannot work with scattered buffers provided by the balloon driver,
+	  but require DMAable memory instead.
+
+config SWIOTLB_XEN
+	def_bool y
+	depends on ARCH_HAS_DMA_OPS
+	depends on XEN_PV || ARM || ARM64
+	select SWIOTLB
+
+config XEN_PCI_STUB
+	bool
+
+config XEN_PCIDEV_STUB
+	tristate "Xen PCI-device stub driver"
+	depends on PCI && !X86 && XEN
+	depends on XEN_BACKEND
+	select XEN_PCI_STUB
+	default m
+	help
+	  The PCI device stub driver provides limited version of the PCI
+	  device backend driver without para-virtualized support for guests.
+	  If you select this to be a module, you will need to make sure no
+	  other driver has bound to the device(s) you want to make visible to
+	  other guests.
+
+	  The "hide" parameter (only applicable if backend driver is compiled
+	  into the kernel) allows you to bind the PCI devices to this module
+	  from the default device drivers. The argument is the list of PCI BDFs:
+	  xen-pciback.hide=(03:00.0)(04:00.0)
+
+	  If in doubt, say m.
+
+config XEN_PCIDEV_BACKEND
+	tristate "Xen PCI-device backend driver"
+	depends on PCI && X86 && XEN
+	depends on XEN_BACKEND
+	select XEN_PCI_STUB
+	default m
+	help
+	  The PCI device backend driver allows the kernel to export arbitrary
+	  PCI devices to other guests. If you select this to be a module, you
+	  will need to make sure no other driver has bound to the device(s)
+	  you want to make visible to other guests.
+
+	  The parameter "passthrough" allows you specify how you want the PCI
+	  devices to appear in the guest. You can choose the default (0) where
+	  PCI topology starts at 00.00.0, or (1) for passthrough if you want
+	  the PCI devices topology appear the same as in the host.
+
+	  The "hide" parameter (only applicable if backend driver is compiled
+	  into the kernel) allows you to bind the PCI devices to this module
+	  from the default device drivers. The argument is the list of PCI BDFs:
+	  xen-pciback.hide=(03:00.0)(04:00.0)
+
+	  If in doubt, say m.
+
+config XEN_PVCALLS_FRONTEND
+	tristate "XEN PV Calls frontend driver"
+	depends on INET && XEN
+	select XEN_XENBUS_FRONTEND
+	help
+	  Experimental frontend for the Xen PV Calls protocol
+	  (https://xenbits.xen.org/docs/unstable/misc/pvcalls.html). It
+	  sends a small set of POSIX calls to the backend, which
+	  implements them.
+
+config XEN_PVCALLS_BACKEND
+	tristate "XEN PV Calls backend driver"
+	depends on INET && XEN && XEN_BACKEND
+	help
+	  Experimental backend for the Xen PV Calls protocol
+	  (https://xenbits.xen.org/docs/unstable/misc/pvcalls.html). It
+	  allows PV Calls frontends to send POSIX calls to the backend,
+	  which implements them.
+
+	  If in doubt, say n.
+
+config XEN_SCSI_BACKEND
+	tristate "XEN SCSI backend driver"
+	depends on XEN && XEN_BACKEND && TARGET_CORE
+	help
+	  The SCSI backend driver allows the kernel to export its SCSI Devices
+	  to other guests via a high-performance shared-memory interface.
+	  Only needed for systems running as XEN driver domains (e.g. Dom0) and
+	  if guests need generic access to SCSI devices.
+
+config XEN_PRIVCMD
+	tristate "Xen hypercall passthrough driver"
+	depends on XEN
+	default m
+	help
+	  The hypercall passthrough driver allows privileged user programs to
+	  perform Xen hypercalls. This driver is normally required for systems
+	  running as Dom0 to perform privileged operations, but in some
+	  disaggregated Xen setups this driver might be needed for other
+	  domains, too.
+
+config XEN_PRIVCMD_EVENTFD
+	bool "Xen Ioeventfd and irqfd support"
+	depends on XEN_PRIVCMD && XEN_VIRTIO && EVENTFD
+	help
+	  Using the ioeventfd / irqfd mechanism a virtio backend running in a
+	  daemon can speed up interrupt delivery from / to a guest.
+
+config XEN_ACPI_PROCESSOR
+	tristate "Xen ACPI processor"
+	depends on XEN && XEN_DOM0 && X86 && ACPI_PROCESSOR && CPU_FREQ
+	default m
+	help
+	  This ACPI processor uploads Power Management information to the Xen
+	  hypervisor.
+
+	  To do that the driver parses the Power Management data and uploads
+	  said information to the Xen hypervisor. Then the Xen hypervisor can
+	  select the proper Cx and Pxx states. It also registers itself as the
+	  SMM so that other drivers (such as ACPI cpufreq scaling driver) will
+	  not load.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called xen_acpi_processor  If you do not know what to choose, select
+	  M here. If the CPUFREQ drivers are built in, select Y here.
+
+config XEN_MCE_LOG
+	bool "Xen platform mcelog"
+	depends on XEN_PV_DOM0 && X86_MCE
+	help
+	  Allow kernel fetching MCE error from Xen platform and
+	  converting it into Linux mcelog format for mcelog tools
+
+config XEN_HAVE_PVMMU
+	bool
+
+config XEN_EFI
+	def_bool y
+	depends on (ARM || ARM64 || X86_64) && EFI
+
+config XEN_ACPI
+	def_bool y
+	depends on X86 && ACPI
+
+config XEN_SYMS
+	bool "Xen symbols"
+	depends on X86 && XEN_DOM0 && XENFS
+	default y if KALLSYMS
+	help
+	  Exports hypervisor symbols (along with their types and addresses) via
+	  /proc/xen/xensyms file, similar to /proc/kallsyms
+
+config XEN_HAVE_VPMU
+	bool
+
+config XEN_FRONT_PGDIR_SHBUF
+	tristate
+
+config XEN_UNPOPULATED_ALLOC
+	bool "Use unpopulated memory ranges for guest mappings"
+	depends on ZONE_DEVICE
+	default XEN_BACKEND || XEN_GNTDEV || XEN_DOM0
+	help
+	  Use unpopulated memory ranges in order to create mappings for guest
+	  memory regions, including grant maps and foreign pages. This avoids
+	  having to balloon out RAM regions in order to obtain physical memory
+	  space to create such mappings.
+
+config XEN_GRANT_DMA_IOMMU
+	bool
+	select IOMMU_API
+
+config XEN_GRANT_DMA_OPS
+	bool
+
+config XEN_VIRTIO
+	bool "Xen virtio support"
+	depends on ARCH_HAS_DMA_OPS
+	depends on VIRTIO
+	select XEN_GRANT_DMA_OPS
+	select XEN_GRANT_DMA_IOMMU if OF
+	help
+	  Enable virtio support for running as Xen guest. Depending on the
+	  guest type this will require special support on the backend side
+	  (qemu or kernel, depending on the virtio device types used).
+
+	  If in doubt, say n.
+
+config XEN_VIRTIO_FORCE_GRANT
+	bool "Require Xen virtio support to use grants"
+	depends on XEN_VIRTIO
+	help
+	  Require virtio for Xen guests to use grant mappings.
+	  This will avoid the need to give the backend the right to map all
+	  of the guest memory. This will need support on the backend side
+	  (e.g. qemu or kernel, depending on the virtio device types used).
+
+endmenu
diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
new file mode 100644
index 000000000..6ce2e2a52
--- /dev/null
+++ b/drivers/xen/Makefile
@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_HOTPLUG_CPU)		+= cpu_hotplug.o
+obj-y	+= grant-table.o features.o balloon.o manage.o time.o
+obj-y	+= mem-reservation.o
+obj-y	+= xlate_mmu.o
+obj-y	+= events/
+obj-y	+= xenbus/
+
+CFLAGS_features.o			:= -fno-stack-protector
+
+dom0-$(CONFIG_ARM64) += arm-device.o
+dom0-$(CONFIG_PCI) += pci.o
+dom0-$(CONFIG_USB_SUPPORT) += dbgp.o
+dom0-$(CONFIG_XEN_ACPI) += acpi.o $(xen-pad-y)
+xen-pad-$(CONFIG_X86) += xen-acpi-pad.o
+dom0-$(CONFIG_X86) += pcpu.o
+obj-$(CONFIG_XEN_DOM0)			+= $(dom0-y)
+obj-$(CONFIG_BLOCK)			+= biomerge.o
+obj-$(CONFIG_XEN_BALLOON)		+= xen-balloon.o
+obj-$(CONFIG_XEN_DEV_EVTCHN)		+= xen-evtchn.o
+obj-$(CONFIG_XEN_GNTDEV)		+= xen-gntdev.o
+obj-$(CONFIG_XEN_GRANT_DEV_ALLOC)	+= xen-gntalloc.o
+obj-$(CONFIG_XENFS)			+= xenfs/
+obj-$(CONFIG_XEN_SYS_HYPERVISOR)	+= sys-hypervisor.o
+obj-$(CONFIG_XEN_PVHVM_GUEST)		+= platform-pci.o
+obj-$(CONFIG_SWIOTLB_XEN)		+= swiotlb-xen.o
+obj-$(CONFIG_XEN_MCE_LOG)		+= mcelog.o
+obj-$(CONFIG_XEN_PCI_STUB)	        += xen-pciback/
+obj-$(CONFIG_XEN_PRIVCMD)		+= xen-privcmd.o
+obj-$(CONFIG_XEN_ACPI_PROCESSOR)	+= xen-acpi-processor.o
+obj-$(CONFIG_XEN_EFI)			+= efi.o
+obj-$(CONFIG_XEN_SCSI_BACKEND)		+= xen-scsiback.o
+obj-$(CONFIG_XEN_PVCALLS_BACKEND)	+= pvcalls-back.o
+obj-$(CONFIG_XEN_PVCALLS_FRONTEND)	+= pvcalls-front.o
+xen-evtchn-y				:= evtchn.o
+xen-gntdev-y				:= gntdev.o
+xen-gntdev-$(CONFIG_XEN_GNTDEV_DMABUF)	+= gntdev-dmabuf.o
+xen-gntalloc-y				:= gntalloc.o
+xen-privcmd-y				:= privcmd.o privcmd-buf.o
+obj-$(CONFIG_XEN_FRONT_PGDIR_SHBUF)	+= xen-front-pgdir-shbuf.o
+obj-$(CONFIG_XEN_UNPOPULATED_ALLOC)	+= unpopulated-alloc.o
+obj-$(CONFIG_XEN_GRANT_DMA_OPS)		+= grant-dma-ops.o
+obj-$(CONFIG_XEN_GRANT_DMA_IOMMU)	+= grant-dma-iommu.o
diff --git a/drivers/xen/acpi.c b/drivers/xen/acpi.c
new file mode 100644
index 000000000..eab28cfe9
--- /dev/null
+++ b/drivers/xen/acpi.c
@@ -0,0 +1,152 @@
+/******************************************************************************
+ * acpi.c
+ * acpi file for domain 0 kernel
+ *
+ * Copyright (c) 2011 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
+ * Copyright (c) 2011 Yu Ke ke.yu@intel.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <linux/pci.h>
+#include <xen/acpi.h>
+#include <xen/interface/platform.h>
+#include <asm/xen/hypercall.h>
+#include <asm/xen/hypervisor.h>
+
+static int xen_acpi_notify_hypervisor_state(u8 sleep_state,
+					    u32 val_a, u32 val_b,
+					    bool extended)
+{
+	unsigned int bits = extended ? 8 : 16;
+
+	struct xen_platform_op op = {
+		.cmd = XENPF_enter_acpi_sleep,
+		.interface_version = XENPF_INTERFACE_VERSION,
+		.u.enter_acpi_sleep = {
+			.val_a = (u16)val_a,
+			.val_b = (u16)val_b,
+			.sleep_state = sleep_state,
+			.flags = extended ? XENPF_ACPI_SLEEP_EXTENDED : 0,
+		},
+	};
+
+	if (WARN((val_a & (~0 << bits)) || (val_b & (~0 << bits)),
+		 "Using more than %u bits of sleep control values %#x/%#x!"
+		 "Email xen-devel@lists.xen.org - Thank you.\n", \
+		 bits, val_a, val_b))
+		return -1;
+
+	HYPERVISOR_platform_op(&op);
+	return 1;
+}
+
+int xen_acpi_notify_hypervisor_sleep(u8 sleep_state,
+				     u32 pm1a_cnt, u32 pm1b_cnt)
+{
+	return xen_acpi_notify_hypervisor_state(sleep_state, pm1a_cnt,
+						pm1b_cnt, false);
+}
+
+int xen_acpi_notify_hypervisor_extended_sleep(u8 sleep_state,
+				     u32 val_a, u32 val_b)
+{
+	return xen_acpi_notify_hypervisor_state(sleep_state, val_a,
+						val_b, true);
+}
+
+struct acpi_prt_entry {
+	struct acpi_pci_id      id;
+	u8                      pin;
+	acpi_handle             link;
+	u32                     index;
+};
+
+int xen_acpi_get_gsi_info(struct pci_dev *dev,
+						  int *gsi_out,
+						  int *trigger_out,
+						  int *polarity_out)
+{
+	u32 gsi;
+	u8 pin;
+	struct acpi_prt_entry *entry;
+	int trigger = ACPI_LEVEL_SENSITIVE;
+	int ret, polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ?
+				      ACPI_ACTIVE_HIGH : ACPI_ACTIVE_LOW;
+
+	if (!dev || !gsi_out || !trigger_out || !polarity_out)
+		return -EINVAL;
+
+	pin = dev->pin;
+	if (!pin)
+		return -EINVAL;
+
+	entry = acpi_pci_irq_lookup(dev, pin);
+	if (entry) {
+		ret = 0;
+		if (entry->link)
+			ret = acpi_pci_link_allocate_irq(entry->link,
+							 entry->index,
+							 &trigger, &polarity,
+							 NULL, &gsi);
+		else
+			gsi = entry->index;
+	} else
+		ret = -ENODEV;
+
+	if (ret < 0)
+		return -EINVAL;
+
+	*gsi_out = gsi;
+	*trigger_out = trigger;
+	*polarity_out = polarity;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_acpi_get_gsi_info);
+
+static get_gsi_from_sbdf_t get_gsi_from_sbdf;
+static DEFINE_RWLOCK(get_gsi_from_sbdf_lock);
+
+void xen_acpi_register_get_gsi_func(get_gsi_from_sbdf_t func)
+{
+	write_lock(&get_gsi_from_sbdf_lock);
+	get_gsi_from_sbdf = func;
+	write_unlock(&get_gsi_from_sbdf_lock);
+}
+EXPORT_SYMBOL_GPL(xen_acpi_register_get_gsi_func);
+
+int xen_acpi_get_gsi_from_sbdf(u32 sbdf)
+{
+	int ret = -EOPNOTSUPP;
+
+	read_lock(&get_gsi_from_sbdf_lock);
+	if (get_gsi_from_sbdf)
+		ret = get_gsi_from_sbdf(sbdf);
+	read_unlock(&get_gsi_from_sbdf_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xen_acpi_get_gsi_from_sbdf);
diff --git a/drivers/xen/arm-device.c b/drivers/xen/arm-device.c
new file mode 100644
index 000000000..7bc0fc400
--- /dev/null
+++ b/drivers/xen/arm-device.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015, Linaro Limited, Shannon Zhao
+ */
+
+#include <linux/platform_device.h>
+#include <linux/acpi.h>
+#include <xen/xen.h>
+#include <xen/page.h>
+#include <xen/interface/memory.h>
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+
+static int xen_unmap_device_mmio(const struct resource *resources,
+				 unsigned int count)
+{
+	unsigned int i, j, nr;
+	int rc = 0;
+	const struct resource *r;
+	struct xen_remove_from_physmap xrp;
+
+	for (i = 0; i < count; i++) {
+		r = &resources[i];
+		nr = DIV_ROUND_UP(resource_size(r), XEN_PAGE_SIZE);
+		if ((resource_type(r) != IORESOURCE_MEM) || (nr == 0))
+			continue;
+
+		for (j = 0; j < nr; j++) {
+			xrp.domid = DOMID_SELF;
+			xrp.gpfn = XEN_PFN_DOWN(r->start) + j;
+			rc = HYPERVISOR_memory_op(XENMEM_remove_from_physmap,
+						  &xrp);
+			if (rc)
+				return rc;
+		}
+	}
+
+	return rc;
+}
+
+static int xen_map_device_mmio(const struct resource *resources,
+			       unsigned int count)
+{
+	unsigned int i, j, nr;
+	int rc = 0;
+	const struct resource *r;
+	xen_pfn_t *gpfns;
+	xen_ulong_t *idxs;
+	int *errs;
+
+	for (i = 0; i < count; i++) {
+		struct xen_add_to_physmap_range xatp = {
+			.domid = DOMID_SELF,
+			.space = XENMAPSPACE_dev_mmio
+		};
+
+		r = &resources[i];
+		nr = DIV_ROUND_UP(resource_size(r), XEN_PAGE_SIZE);
+		if ((resource_type(r) != IORESOURCE_MEM) || (nr == 0))
+			continue;
+
+		gpfns = kzalloc_objs(xen_pfn_t, nr);
+		idxs = kzalloc_objs(xen_ulong_t, nr);
+		errs = kzalloc_objs(int, nr);
+		if (!gpfns || !idxs || !errs) {
+			kfree(gpfns);
+			kfree(idxs);
+			kfree(errs);
+			rc = -ENOMEM;
+			goto unmap;
+		}
+
+		for (j = 0; j < nr; j++) {
+			/*
+			 * The regions are always mapped 1:1 to DOM0 and this is
+			 * fine because the memory map for DOM0 is the same as
+			 * the host (except for the RAM).
+			 */
+			gpfns[j] = XEN_PFN_DOWN(r->start) + j;
+			idxs[j] = XEN_PFN_DOWN(r->start) + j;
+		}
+
+		xatp.size = nr;
+
+		set_xen_guest_handle(xatp.gpfns, gpfns);
+		set_xen_guest_handle(xatp.idxs, idxs);
+		set_xen_guest_handle(xatp.errs, errs);
+
+		rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap_range, &xatp);
+		kfree(gpfns);
+		kfree(idxs);
+		kfree(errs);
+		if (rc)
+			goto unmap;
+	}
+
+	return rc;
+
+unmap:
+	xen_unmap_device_mmio(resources, i);
+	return rc;
+}
+
+static int xen_platform_notifier(struct notifier_block *nb,
+				 unsigned long action, void *data)
+{
+	struct platform_device *pdev = to_platform_device(data);
+	int r = 0;
+
+	if (pdev->num_resources == 0 || pdev->resource == NULL)
+		return NOTIFY_OK;
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		r = xen_map_device_mmio(pdev->resource, pdev->num_resources);
+		break;
+	case BUS_NOTIFY_DEL_DEVICE:
+		r = xen_unmap_device_mmio(pdev->resource, pdev->num_resources);
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+	if (r)
+		dev_err(&pdev->dev, "Platform: Failed to %s device %s MMIO!\n",
+			action == BUS_NOTIFY_ADD_DEVICE ? "map" :
+			(action == BUS_NOTIFY_DEL_DEVICE ? "unmap" : "?"),
+			pdev->name);
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block platform_device_nb = {
+	.notifier_call = xen_platform_notifier,
+};
+
+static int __init register_xen_platform_notifier(void)
+{
+	if (!xen_initial_domain() || acpi_disabled)
+		return 0;
+
+	return bus_register_notifier(&platform_bus_type, &platform_device_nb);
+}
+
+arch_initcall(register_xen_platform_notifier);
+
+#ifdef CONFIG_ARM_AMBA
+#include <linux/amba/bus.h>
+
+static int xen_amba_notifier(struct notifier_block *nb,
+			     unsigned long action, void *data)
+{
+	struct amba_device *adev = to_amba_device(data);
+	int r = 0;
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		r = xen_map_device_mmio(&adev->res, 1);
+		break;
+	case BUS_NOTIFY_DEL_DEVICE:
+		r = xen_unmap_device_mmio(&adev->res, 1);
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+	if (r)
+		dev_err(&adev->dev, "AMBA: Failed to %s device %s MMIO!\n",
+			action == BUS_NOTIFY_ADD_DEVICE ? "map" :
+			(action == BUS_NOTIFY_DEL_DEVICE ? "unmap" : "?"),
+			adev->dev.init_name);
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block amba_device_nb = {
+	.notifier_call = xen_amba_notifier,
+};
+
+static int __init register_xen_amba_notifier(void)
+{
+	if (!xen_initial_domain() || acpi_disabled)
+		return 0;
+
+	return bus_register_notifier(&amba_bustype, &amba_device_nb);
+}
+
+arch_initcall(register_xen_amba_notifier);
+#endif
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
new file mode 100644
index 000000000..e7f74ea7c
--- /dev/null
+++ b/drivers/xen/balloon.c
@@ -0,0 +1,833 @@
+/******************************************************************************
+ * Xen balloon driver - enables returning/claiming memory to/from Xen.
+ *
+ * Copyright (c) 2003, B Dragovic
+ * Copyright (c) 2003-2004, M Williamson, K Fraser
+ * Copyright (c) 2005 Dan M. Smith, IBM Corporation
+ * Copyright (c) 2010 Daniel Kiper
+ *
+ * Memory hotplug support was written by Daniel Kiper. Work on
+ * it was sponsored by Google under Google Summer of Code 2010
+ * program. Jeremy Fitzhardinge from Citrix was the mentor for
+ * this project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/cpu.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/cred.h>
+#include <linux/errno.h>
+#include <linux/freezer.h>
+#include <linux/kthread.h>
+#include <linux/mm.h>
+#include <linux/memblock.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/gfp.h>
+#include <linux/notifier.h>
+#include <linux/memory.h>
+#include <linux/memory_hotplug.h>
+#include <linux/percpu-defs.h>
+#include <linux/slab.h>
+#include <linux/sysctl.h>
+#include <linux/moduleparam.h>
+#include <linux/jiffies.h>
+
+#include <asm/page.h>
+#include <asm/tlb.h>
+
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+
+#include <xen/xen.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/memory.h>
+#include <xen/balloon.h>
+#include <xen/features.h>
+#include <xen/page.h>
+#include <xen/mem-reservation.h>
+
+#undef MODULE_PARAM_PREFIX
+#define MODULE_PARAM_PREFIX "xen."
+
+static uint __read_mostly balloon_boot_timeout = 180;
+module_param(balloon_boot_timeout, uint, 0444);
+
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+static int xen_hotplug_unpopulated;
+
+static const struct ctl_table balloon_table[] = {
+	{
+		.procname	= "hotplug_unpopulated",
+		.data		= &xen_hotplug_unpopulated,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1         = SYSCTL_ZERO,
+		.extra2         = SYSCTL_ONE,
+	},
+};
+
+#else
+#define xen_hotplug_unpopulated 0
+#endif
+
+/*
+ * Use one extent per PAGE_SIZE to avoid to break down the page into
+ * multiple frame.
+ */
+#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
+
+/*
+ * balloon_thread() state:
+ *
+ * BP_DONE: done or nothing to do,
+ * BP_WAIT: wait to be rescheduled,
+ * BP_EAGAIN: error, go to sleep,
+ * BP_ECANCELED: error, balloon operation canceled.
+ */
+
+static enum bp_state {
+	BP_DONE,
+	BP_WAIT,
+	BP_EAGAIN,
+	BP_ECANCELED
+} balloon_state = BP_DONE;
+
+/* Main waiting point for xen-balloon thread. */
+static DECLARE_WAIT_QUEUE_HEAD(balloon_thread_wq);
+
+static DEFINE_MUTEX(balloon_mutex);
+
+struct balloon_stats balloon_stats;
+EXPORT_SYMBOL_GPL(balloon_stats);
+
+/* We increase/decrease in batches which fit in a page */
+static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
+
+
+/* List of ballooned pages, threaded through the mem_map array. */
+static LIST_HEAD(ballooned_pages);
+static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
+
+/* When ballooning out (allocating memory to return to Xen) we don't really
+   want the kernel to try too hard since that can trigger the oom killer. */
+#define GFP_BALLOON \
+	(GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
+
+/* balloon_append: add the given page to the balloon. */
+static void balloon_append(struct page *page)
+{
+	if (!PageOffline(page))
+		__SetPageOffline(page);
+
+	/* Lowmem is re-populated first, so highmem pages go at list tail. */
+	if (PageHighMem(page)) {
+		list_add_tail(&page->lru, &ballooned_pages);
+		balloon_stats.balloon_high++;
+	} else {
+		list_add(&page->lru, &ballooned_pages);
+		balloon_stats.balloon_low++;
+	}
+	inc_node_page_state(page, NR_BALLOON_PAGES);
+
+	wake_up(&balloon_wq);
+}
+
+/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
+static struct page *balloon_retrieve(bool require_lowmem)
+{
+	struct page *page;
+
+	if (list_empty(&ballooned_pages))
+		return NULL;
+
+	page = list_entry(ballooned_pages.next, struct page, lru);
+	if (require_lowmem && PageHighMem(page))
+		return NULL;
+	list_del(&page->lru);
+
+	if (PageHighMem(page))
+		balloon_stats.balloon_high--;
+	else
+		balloon_stats.balloon_low--;
+
+	__ClearPageOffline(page);
+	dec_node_page_state(page, NR_BALLOON_PAGES);
+
+	return page;
+}
+
+static struct page *balloon_next_page(struct page *page)
+{
+	struct list_head *next = page->lru.next;
+	if (next == &ballooned_pages)
+		return NULL;
+	return list_entry(next, struct page, lru);
+}
+
+static void update_schedule(void)
+{
+	if (balloon_state == BP_WAIT || balloon_state == BP_ECANCELED)
+		return;
+
+	if (balloon_state == BP_DONE) {
+		balloon_stats.schedule_delay = 1;
+		balloon_stats.retry_count = 1;
+		return;
+	}
+
+	++balloon_stats.retry_count;
+
+	if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
+			balloon_stats.retry_count > balloon_stats.max_retry_count) {
+		balloon_stats.schedule_delay = 1;
+		balloon_stats.retry_count = 1;
+		balloon_state = BP_ECANCELED;
+		return;
+	}
+
+	balloon_stats.schedule_delay <<= 1;
+
+	if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
+		balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
+
+	balloon_state = BP_EAGAIN;
+}
+
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+static void release_memory_resource(struct resource *resource)
+{
+	if (!resource)
+		return;
+
+	/*
+	 * No need to reset region to identity mapped since we now
+	 * know that no I/O can be in this region
+	 */
+	release_resource(resource);
+	kfree(resource);
+}
+
+static struct resource *additional_memory_resource(phys_addr_t size)
+{
+	struct resource *res;
+	int ret;
+
+	res = kzalloc_obj(*res);
+	if (!res)
+		return NULL;
+
+	res->name = "System RAM";
+	res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+
+	ret = allocate_resource(&iomem_resource, res,
+				size, 0, -1,
+				PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
+	if (ret < 0) {
+		pr_err("Cannot allocate new System RAM resource\n");
+		kfree(res);
+		return NULL;
+	}
+
+	return res;
+}
+
+static enum bp_state reserve_additional_memory(void)
+{
+	long credit;
+	struct resource *resource;
+	int nid, rc;
+	unsigned long balloon_hotplug;
+
+	credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
+		- balloon_stats.total_pages;
+
+	/*
+	 * Already hotplugged enough pages?  Wait for them to be
+	 * onlined.
+	 */
+	if (credit <= 0)
+		return BP_WAIT;
+
+	balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
+
+	resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
+	if (!resource)
+		goto err;
+
+	nid = memory_add_physaddr_to_nid(resource->start);
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+	/*
+	 * We don't support PV MMU when Linux and Xen is using
+	 * different page granularity.
+	 */
+	BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
+        /*
+         * add_memory() will build page tables for the new memory so
+         * the p2m must contain invalid entries so the correct
+         * non-present PTEs will be written.
+         *
+         * If a failure occurs, the original (identity) p2m entries
+         * are not restored since this region is now known not to
+         * conflict with any devices.
+         */ 
+	if (xen_pv_domain()) {
+		unsigned long pfn, i;
+
+		pfn = PFN_DOWN(resource->start);
+		for (i = 0; i < balloon_hotplug; i++) {
+			if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
+				pr_warn("set_phys_to_machine() failed, no memory added\n");
+				goto err;
+			}
+                }
+	}
+#endif
+
+	/*
+	 * add_memory_resource() will call online_pages() which in its turn
+	 * will call xen_online_page() callback causing deadlock if we don't
+	 * release balloon_mutex here. Unlocking here is safe because the
+	 * callers drop the mutex before trying again.
+	 */
+	mutex_unlock(&balloon_mutex);
+	/* add_memory_resource() requires the device_hotplug lock */
+	lock_device_hotplug();
+	rc = add_memory_resource(nid, resource, MHP_MERGE_RESOURCE);
+	unlock_device_hotplug();
+	mutex_lock(&balloon_mutex);
+
+	if (rc) {
+		pr_warn("Cannot add additional memory (%i)\n", rc);
+		goto err;
+	}
+
+	balloon_stats.total_pages += balloon_hotplug;
+
+	return BP_WAIT;
+  err:
+	release_memory_resource(resource);
+	return BP_ECANCELED;
+}
+
+static void xen_online_page(struct page *page, unsigned int order)
+{
+	unsigned long i, size = (1 << order);
+	unsigned long start_pfn = page_to_pfn(page);
+	struct page *p;
+
+	pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn);
+	mutex_lock(&balloon_mutex);
+	for (i = 0; i < size; i++) {
+		p = pfn_to_page(start_pfn + i);
+		balloon_append(p);
+	}
+	mutex_unlock(&balloon_mutex);
+}
+
+static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
+{
+	if (val == MEM_ONLINE)
+		wake_up(&balloon_thread_wq);
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block xen_memory_nb = {
+	.notifier_call = xen_memory_notifier,
+	.priority = 0
+};
+#else
+static enum bp_state reserve_additional_memory(void)
+{
+	balloon_stats.target_pages = balloon_stats.current_pages +
+				     balloon_stats.target_unpopulated;
+	return BP_ECANCELED;
+}
+#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
+
+static long current_credit(void)
+{
+	return balloon_stats.target_pages - balloon_stats.current_pages;
+}
+
+static bool balloon_is_inflated(void)
+{
+	return balloon_stats.balloon_low || balloon_stats.balloon_high;
+}
+
+static enum bp_state increase_reservation(unsigned long nr_pages)
+{
+	int rc;
+	unsigned long i;
+	struct page   *page;
+
+	if (nr_pages > ARRAY_SIZE(frame_list))
+		nr_pages = ARRAY_SIZE(frame_list);
+
+	page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
+	for (i = 0; i < nr_pages; i++) {
+		if (!page) {
+			nr_pages = i;
+			break;
+		}
+
+		frame_list[i] = page_to_xen_pfn(page);
+		page = balloon_next_page(page);
+	}
+
+	rc = xenmem_reservation_increase(nr_pages, frame_list);
+	if (rc <= 0)
+		return BP_EAGAIN;
+
+	for (i = 0; i < rc; i++) {
+		page = balloon_retrieve(false);
+		BUG_ON(page == NULL);
+
+		xenmem_reservation_va_mapping_update(1, &page, &frame_list[i]);
+
+		/*
+		 * Relinquish the page back to the allocator. Note that
+		 * some pages, including ones added via xen_online_page(), might
+		 * not be marked reserved; free_reserved_page() will handle that.
+		 */
+		free_reserved_page(page);
+	}
+
+	balloon_stats.current_pages += rc;
+
+	return BP_DONE;
+}
+
+static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
+{
+	enum bp_state state = BP_DONE;
+	unsigned long i;
+	struct page *page, *tmp;
+	int ret;
+	LIST_HEAD(pages);
+
+	if (nr_pages > ARRAY_SIZE(frame_list))
+		nr_pages = ARRAY_SIZE(frame_list);
+
+	for (i = 0; i < nr_pages; i++) {
+		page = alloc_page(gfp);
+		if (page == NULL) {
+			nr_pages = i;
+			state = BP_EAGAIN;
+			break;
+		}
+		adjust_managed_page_count(page, -1);
+		xenmem_reservation_scrub_page(page);
+		list_add(&page->lru, &pages);
+	}
+
+	/*
+	 * Ensure that ballooned highmem pages don't have kmaps.
+	 *
+	 * Do this before changing the p2m as kmap_flush_unused()
+	 * reads PTEs to obtain pages (and hence needs the original
+	 * p2m entry).
+	 */
+	kmap_flush_unused();
+
+	/*
+	 * Setup the frame, update direct mapping, invalidate P2M,
+	 * and add to balloon.
+	 */
+	i = 0;
+	list_for_each_entry_safe(page, tmp, &pages, lru) {
+		frame_list[i++] = xen_page_to_gfn(page);
+
+		xenmem_reservation_va_mapping_reset(1, &page);
+
+		list_del(&page->lru);
+
+		balloon_append(page);
+	}
+
+	flush_tlb_all();
+
+	ret = xenmem_reservation_decrease(nr_pages, frame_list);
+	BUG_ON(ret != nr_pages);
+
+	balloon_stats.current_pages -= nr_pages;
+
+	return state;
+}
+
+/*
+ * Stop waiting if either state is BP_DONE and ballooning action is
+ * needed, or if the credit has changed while state is not BP_DONE.
+ */
+static bool balloon_thread_cond(long credit)
+{
+	if (balloon_state == BP_DONE)
+		credit = 0;
+
+	return current_credit() != credit || kthread_should_stop();
+}
+
+/*
+ * As this is a kthread it is guaranteed to run as a single instance only.
+ * We may of course race updates of the target counts (which are protected
+ * by the balloon lock), or with changes to the Xen hard limit, but we will
+ * recover from these in time.
+ */
+static int balloon_thread(void *unused)
+{
+	long credit;
+	unsigned long timeout;
+
+	set_freezable();
+	for (;;) {
+		switch (balloon_state) {
+		case BP_DONE:
+		case BP_ECANCELED:
+			timeout = 3600 * HZ;
+			break;
+		case BP_EAGAIN:
+			timeout = balloon_stats.schedule_delay * HZ;
+			break;
+		case BP_WAIT:
+			timeout = HZ;
+			break;
+		}
+
+		credit = current_credit();
+
+		wait_event_freezable_timeout(balloon_thread_wq,
+			balloon_thread_cond(credit), timeout);
+
+		if (kthread_should_stop())
+			return 0;
+
+		mutex_lock(&balloon_mutex);
+
+		credit = current_credit();
+
+		if (credit > 0) {
+			if (balloon_is_inflated())
+				balloon_state = increase_reservation(credit);
+			else
+				balloon_state = reserve_additional_memory();
+		}
+
+		if (credit < 0) {
+			long n_pages;
+
+			n_pages = min(-credit, si_mem_available());
+			balloon_state = decrease_reservation(n_pages,
+							     GFP_BALLOON);
+			if (balloon_state == BP_DONE && n_pages != -credit &&
+			    n_pages < totalreserve_pages)
+				balloon_state = BP_EAGAIN;
+		}
+
+		update_schedule();
+
+		mutex_unlock(&balloon_mutex);
+
+		cond_resched();
+	}
+}
+
+/* Resets the Xen limit, sets new target, and kicks off processing. */
+void balloon_set_new_target(unsigned long target)
+{
+	/* No need for lock. Not read-modify-write updates. */
+	balloon_stats.target_pages = target;
+	wake_up(&balloon_thread_wq);
+}
+EXPORT_SYMBOL_GPL(balloon_set_new_target);
+
+static int add_ballooned_pages(unsigned int nr_pages)
+{
+	enum bp_state st;
+
+	if (xen_hotplug_unpopulated) {
+		st = reserve_additional_memory();
+		if (st != BP_ECANCELED) {
+			int rc;
+
+			mutex_unlock(&balloon_mutex);
+			rc = wait_event_interruptible(balloon_wq,
+				   !list_empty(&ballooned_pages));
+			mutex_lock(&balloon_mutex);
+			return rc ? -ENOMEM : 0;
+		}
+	}
+
+	if (si_mem_available() < nr_pages)
+		return -ENOMEM;
+
+	st = decrease_reservation(nr_pages, GFP_USER);
+	if (st != BP_DONE)
+		return -ENOMEM;
+
+	return 0;
+}
+
+/**
+ * xen_alloc_ballooned_pages - get pages that have been ballooned out
+ * @nr_pages: Number of pages to get
+ * @pages: pages returned
+ * @return 0 on success, error otherwise
+ */
+int xen_alloc_ballooned_pages(unsigned int nr_pages, struct page **pages)
+{
+	unsigned int pgno = 0;
+	struct page *page;
+	int ret;
+
+	mutex_lock(&balloon_mutex);
+
+	balloon_stats.target_unpopulated += nr_pages;
+
+	while (pgno < nr_pages) {
+		page = balloon_retrieve(true);
+		if (page) {
+			pages[pgno++] = page;
+#ifdef CONFIG_XEN_HAVE_PVMMU
+			/*
+			 * We don't support PV MMU when Linux and Xen is using
+			 * different page granularity.
+			 */
+			BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
+			if (xen_pv_domain()) {
+				ret = xen_alloc_p2m_entry(page_to_pfn(page));
+				if (ret < 0)
+					goto out_undo;
+			}
+#endif
+		} else {
+			ret = add_ballooned_pages(nr_pages - pgno);
+			if (ret < 0)
+				goto out_undo;
+		}
+	}
+	mutex_unlock(&balloon_mutex);
+	return 0;
+ out_undo:
+	mutex_unlock(&balloon_mutex);
+	xen_free_ballooned_pages(pgno, pages);
+	/*
+	 * NB: xen_free_ballooned_pages will only subtract pgno pages, but since
+	 * target_unpopulated is incremented with nr_pages at the start we need
+	 * to remove the remaining ones also, or accounting will be screwed.
+	 */
+	balloon_stats.target_unpopulated -= nr_pages - pgno;
+	return ret;
+}
+EXPORT_SYMBOL(xen_alloc_ballooned_pages);
+
+/**
+ * xen_free_ballooned_pages - return pages retrieved with get_ballooned_pages
+ * @nr_pages: Number of pages
+ * @pages: pages to return
+ */
+void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages)
+{
+	unsigned int i;
+
+	mutex_lock(&balloon_mutex);
+
+	for (i = 0; i < nr_pages; i++) {
+		if (pages[i])
+			balloon_append(pages[i]);
+	}
+
+	balloon_stats.target_unpopulated -= nr_pages;
+
+	/* The balloon may be too large now. Shrink it if needed. */
+	if (current_credit())
+		wake_up(&balloon_thread_wq);
+
+	mutex_unlock(&balloon_mutex);
+}
+EXPORT_SYMBOL(xen_free_ballooned_pages);
+
+static int __init balloon_add_regions(bool append)
+{
+	unsigned long start_pfn, pages;
+	unsigned long pfn, extra_pfn_end;
+	unsigned int i;
+
+	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
+		pages = xen_extra_mem[i].n_pfns;
+		if (!pages)
+			continue;
+
+		start_pfn = xen_extra_mem[i].start_pfn;
+
+		/*
+		 * If the amount of usable memory has been limited (e.g., with
+		 * the 'mem' command line parameter), don't add pages beyond
+		 * this limit.
+		 */
+		extra_pfn_end = min(max_pfn, start_pfn + pages);
+
+		for (pfn = start_pfn; pfn < extra_pfn_end; pfn++)
+			balloon_append(pfn_to_page(pfn));
+
+		/*
+		 * There are two different use-cases depending on how the
+		 * initial memory target is fetched.  For PVH dom0 and PV the
+		 * target is usually set to reflect the domain assigned memory,
+		 * and hence extra regions need adding.
+		 *
+		 * OTOH for HVM and PVH domU the target is set to the amount of
+		 * RAM reported in the memory map, and hence extra regions need
+		 * subtracting to reflect the real memory usage.
+		 */
+		pages = extra_pfn_end - start_pfn;
+		if (append) {
+			balloon_stats.total_pages += pages;
+		} else if (pages >= balloon_stats.current_pages ||
+		           pages >= balloon_stats.target_pages) {
+			WARN(1, "Extra pages underflow current target");
+			return -ERANGE;
+		} else {
+			balloon_stats.current_pages -= pages;
+			balloon_stats.target_pages -= pages;
+		}
+	}
+
+	return 0;
+}
+
+static int __init balloon_init(void)
+{
+	struct task_struct *task;
+	long current_pages = 0;
+	domid_t domid = DOMID_SELF;
+	bool append = true;
+	int rc;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	pr_info("Initialising balloon driver\n");
+
+	if (xen_initial_domain())
+		current_pages = HYPERVISOR_memory_op(XENMEM_current_reservation,
+		                                     &domid);
+	if (current_pages <= 0) {
+		if (xen_pv_domain()) {
+			if (xen_released_pages >= xen_start_info->nr_pages)
+				goto underflow;
+			current_pages = min(xen_start_info->nr_pages -
+			                    xen_released_pages, max_pfn);
+		} else {
+			if (xen_unpopulated_pages >= get_num_physpages())
+				goto underflow;
+			append = false;
+			current_pages = get_num_physpages() -
+			                xen_unpopulated_pages;
+		}
+	}
+
+	balloon_stats.current_pages = current_pages;
+	balloon_stats.target_pages  = balloon_stats.current_pages;
+	balloon_stats.balloon_low   = 0;
+	balloon_stats.balloon_high  = 0;
+	balloon_stats.total_pages   = balloon_stats.current_pages;
+
+	balloon_stats.schedule_delay = 1;
+	balloon_stats.max_schedule_delay = 32;
+	balloon_stats.retry_count = 1;
+	balloon_stats.max_retry_count = 4;
+
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+	set_online_page_callback(&xen_online_page);
+	register_memory_notifier(&xen_memory_nb);
+	register_sysctl_init("xen/balloon", balloon_table);
+#endif
+
+	rc = balloon_add_regions(append);
+	if (rc)
+		return rc;
+
+	task = kthread_run(balloon_thread, NULL, "xen-balloon");
+	if (IS_ERR(task)) {
+		pr_err("xen-balloon thread could not be started, ballooning will not work!\n");
+		return PTR_ERR(task);
+	}
+
+	/* Init the xen-balloon driver. */
+	xen_balloon_init();
+
+	return 0;
+
+ underflow:
+	WARN(1, "Released pages underflow current target");
+	return -ERANGE;
+}
+subsys_initcall(balloon_init);
+
+static int __init balloon_wait_finish(void)
+{
+	long credit, last_credit = 0;
+	unsigned long last_changed = 0;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	/* PV guests don't need to wait. */
+	if (xen_pv_domain() || !current_credit())
+		return 0;
+
+	pr_notice("Waiting for initial ballooning down having finished.\n");
+
+	while ((credit = current_credit()) < 0) {
+		if (credit != last_credit) {
+			last_changed = jiffies;
+			last_credit = credit;
+		}
+		if (balloon_state == BP_ECANCELED) {
+			pr_warn_once("Initial ballooning failed, %ld pages need to be freed.\n",
+				     -credit);
+			if (time_is_before_eq_jiffies(last_changed + HZ * balloon_boot_timeout))
+				panic("Initial ballooning failed!\n");
+		}
+
+		schedule_timeout_interruptible(HZ / 10);
+	}
+
+	pr_notice("Initial ballooning down finished.\n");
+
+	return 0;
+}
+late_initcall_sync(balloon_wait_finish);
diff --git a/drivers/xen/biomerge.c b/drivers/xen/biomerge.c
new file mode 100644
index 000000000..05a286d24
--- /dev/null
+++ b/drivers/xen/biomerge.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bio.h>
+#include <linux/export.h>
+#include <xen/xen.h>
+#include <xen/page.h>
+
+/* check if @page can be merged with 'vec1' */
+bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
+			       const struct page *page)
+{
+#if XEN_PAGE_SIZE == PAGE_SIZE
+	unsigned long bfn1 = pfn_to_bfn(page_to_pfn(vec1->bv_page));
+	unsigned long bfn2 = pfn_to_bfn(page_to_pfn(page));
+
+	return bfn1 + PFN_DOWN(vec1->bv_offset + vec1->bv_len) == bfn2;
+#else
+	/*
+	 * XXX: Add support for merging bio_vec when using different page
+	 * size in Xen and Linux.
+	 */
+	return false;
+#endif
+}
diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
new file mode 100644
index 000000000..b96b11e2b
--- /dev/null
+++ b/drivers/xen/cpu_hotplug.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/notifier.h>
+
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+
+#include <asm/xen/hypervisor.h>
+#include <asm/cpu.h>
+
+static void enable_hotplug_cpu(int cpu)
+{
+	if (!cpu_present(cpu))
+		xen_arch_register_cpu(cpu);
+
+	set_cpu_present(cpu, true);
+}
+
+static void disable_hotplug_cpu(int cpu)
+{
+	if (!cpu_is_hotpluggable(cpu))
+		return;
+	lock_device_hotplug();
+	if (cpu_online(cpu))
+		device_offline(get_cpu_device(cpu));
+	if (!cpu_online(cpu) && cpu_present(cpu)) {
+		xen_arch_unregister_cpu(cpu);
+		set_cpu_present(cpu, false);
+	}
+	unlock_device_hotplug();
+}
+
+static int vcpu_online(unsigned int cpu)
+{
+	int err;
+	char dir[16], state[16];
+
+	sprintf(dir, "cpu/%u", cpu);
+	err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
+	if (err != 1) {
+		if (!xen_initial_domain())
+			pr_err("Unable to read cpu state\n");
+		return err;
+	}
+
+	if (strcmp(state, "online") == 0)
+		return 1;
+	else if (strcmp(state, "offline") == 0)
+		return 0;
+
+	pr_err("unknown state(%s) on CPU%d\n", state, cpu);
+	return -EINVAL;
+}
+static void vcpu_hotplug(unsigned int cpu)
+{
+	if (cpu >= nr_cpu_ids || !cpu_possible(cpu))
+		return;
+
+	switch (vcpu_online(cpu)) {
+	case 1:
+		enable_hotplug_cpu(cpu);
+		break;
+	case 0:
+		disable_hotplug_cpu(cpu);
+		break;
+	default:
+		break;
+	}
+}
+
+static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
+				      const char *path, const char *token)
+{
+	unsigned int cpu;
+	char *cpustr;
+
+	cpustr = strstr(path, "cpu/");
+	if (cpustr != NULL) {
+		sscanf(cpustr, "cpu/%u", &cpu);
+		vcpu_hotplug(cpu);
+	}
+}
+
+static int setup_cpu_watcher(struct notifier_block *notifier,
+			      unsigned long event, void *data)
+{
+	int cpu;
+	static struct xenbus_watch cpu_watch = {
+		.node = "cpu",
+		.callback = handle_vcpu_hotplug_event};
+
+	(void)register_xenbus_watch(&cpu_watch);
+
+	for_each_possible_cpu(cpu) {
+		if (vcpu_online(cpu) == 0)
+			disable_hotplug_cpu(cpu);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static int __init setup_vcpu_hotplug_event(void)
+{
+	static struct notifier_block xsn_cpu = {
+		.notifier_call = setup_cpu_watcher };
+
+#ifdef CONFIG_X86
+	if (!xen_pv_domain() && !xen_pvh_domain())
+#else
+	if (!xen_domain())
+#endif
+		return -ENODEV;
+
+	register_xenstore_notifier(&xsn_cpu);
+
+	return 0;
+}
+
+late_initcall(setup_vcpu_hotplug_event);
+
diff --git a/drivers/xen/dbgp.c b/drivers/xen/dbgp.c
new file mode 100644
index 000000000..cfb5de31d
--- /dev/null
+++ b/drivers/xen/dbgp.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/pci.h>
+#include <linux/usb.h>
+#include <linux/usb/ehci_def.h>
+#include <linux/usb/hcd.h>
+#include <asm/xen/hypercall.h>
+#include <xen/interface/physdev.h>
+#include <xen/xen.h>
+
+static int xen_dbgp_op(struct usb_hcd *hcd, int op)
+{
+#ifdef CONFIG_PCI
+	const struct device *ctrlr = hcd_to_bus(hcd)->controller;
+#endif
+	struct physdev_dbgp_op dbgp;
+
+	if (!xen_initial_domain())
+		return 0;
+
+	dbgp.op = op;
+
+#ifdef CONFIG_PCI
+	if (dev_is_pci(ctrlr)) {
+		const struct pci_dev *pdev = to_pci_dev(ctrlr);
+
+		dbgp.u.pci.seg = pci_domain_nr(pdev->bus);
+		dbgp.u.pci.bus = pdev->bus->number;
+		dbgp.u.pci.devfn = pdev->devfn;
+		dbgp.bus = PHYSDEVOP_DBGP_BUS_PCI;
+	} else
+#endif
+		dbgp.bus = PHYSDEVOP_DBGP_BUS_UNKNOWN;
+
+	return HYPERVISOR_physdev_op(PHYSDEVOP_dbgp_op, &dbgp);
+}
+
+int xen_dbgp_reset_prep(struct usb_hcd *hcd)
+{
+	return xen_dbgp_op(hcd, PHYSDEVOP_DBGP_RESET_PREPARE);
+}
+
+int xen_dbgp_external_startup(struct usb_hcd *hcd)
+{
+	return xen_dbgp_op(hcd, PHYSDEVOP_DBGP_RESET_DONE);
+}
+
+#ifndef CONFIG_EARLY_PRINTK_DBGP
+#include <linux/export.h>
+EXPORT_SYMBOL_GPL(xen_dbgp_reset_prep);
+EXPORT_SYMBOL_GPL(xen_dbgp_external_startup);
+#endif
diff --git a/drivers/xen/efi.c b/drivers/xen/efi.c
new file mode 100644
index 000000000..fb321cd64
--- /dev/null
+++ b/drivers/xen/efi.c
@@ -0,0 +1,355 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * EFI support for Xen.
+ *
+ * Copyright (C) 1999 VA Linux Systems
+ * Copyright (C) 1999 Walt Drummond <drummond@valinux.com>
+ * Copyright (C) 1999-2002 Hewlett-Packard Co.
+ *	David Mosberger-Tang <davidm@hpl.hp.com>
+ *	Stephane Eranian <eranian@hpl.hp.com>
+ * Copyright (C) 2005-2008 Intel Co.
+ *	Fenghua Yu <fenghua.yu@intel.com>
+ *	Bibo Mao <bibo.mao@intel.com>
+ *	Chandramouli Narayanan <mouli@linux.intel.com>
+ *	Huang Ying <ying.huang@intel.com>
+ * Copyright (C) 2011 Novell Co.
+ *	Jan Beulich <JBeulich@suse.com>
+ * Copyright (C) 2011-2012 Oracle Co.
+ *	Liang Tang <liang.tang@oracle.com>
+ * Copyright (c) 2014 Oracle Co., Daniel Kiper
+ */
+
+#include <linux/bug.h>
+#include <linux/efi.h>
+#include <linux/init.h>
+#include <linux/string.h>
+
+#include <xen/interface/xen.h>
+#include <xen/interface/platform.h>
+#include <xen/page.h>
+#include <xen/xen.h>
+#include <xen/xen-ops.h>
+
+#include <asm/page.h>
+
+#include <asm/xen/hypercall.h>
+
+#define INIT_EFI_OP(name) \
+	{.cmd = XENPF_efi_runtime_call, \
+	 .u.efi_runtime_call.function = XEN_EFI_##name, \
+	 .u.efi_runtime_call.misc = 0}
+
+#define efi_data(op)	(op.u.efi_runtime_call)
+
+static efi_status_t xen_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
+{
+	struct xen_platform_op op = INIT_EFI_OP(get_time);
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	if (tm) {
+		BUILD_BUG_ON(sizeof(*tm) != sizeof(efi_data(op).u.get_time.time));
+		memcpy(tm, &efi_data(op).u.get_time.time, sizeof(*tm));
+	}
+
+	if (tc) {
+		tc->resolution = efi_data(op).u.get_time.resolution;
+		tc->accuracy = efi_data(op).u.get_time.accuracy;
+		tc->sets_to_zero = !!(efi_data(op).misc &
+				      XEN_EFI_GET_TIME_SET_CLEARS_NS);
+	}
+
+	return efi_data(op).status;
+}
+
+static efi_status_t xen_efi_set_time(efi_time_t *tm)
+{
+	struct xen_platform_op op = INIT_EFI_OP(set_time);
+
+	BUILD_BUG_ON(sizeof(*tm) != sizeof(efi_data(op).u.set_time));
+	memcpy(&efi_data(op).u.set_time, tm, sizeof(*tm));
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	return efi_data(op).status;
+}
+
+static efi_status_t xen_efi_get_wakeup_time(efi_bool_t *enabled,
+					    efi_bool_t *pending,
+					    efi_time_t *tm)
+{
+	struct xen_platform_op op = INIT_EFI_OP(get_wakeup_time);
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	if (tm) {
+		BUILD_BUG_ON(sizeof(*tm) != sizeof(efi_data(op).u.get_wakeup_time));
+		memcpy(tm, &efi_data(op).u.get_wakeup_time, sizeof(*tm));
+	}
+
+	if (enabled)
+		*enabled = !!(efi_data(op).misc & XEN_EFI_GET_WAKEUP_TIME_ENABLED);
+
+	if (pending)
+		*pending = !!(efi_data(op).misc & XEN_EFI_GET_WAKEUP_TIME_PENDING);
+
+	return efi_data(op).status;
+}
+
+static efi_status_t xen_efi_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm)
+{
+	struct xen_platform_op op = INIT_EFI_OP(set_wakeup_time);
+
+	BUILD_BUG_ON(sizeof(*tm) != sizeof(efi_data(op).u.set_wakeup_time));
+	if (enabled)
+		efi_data(op).misc = XEN_EFI_SET_WAKEUP_TIME_ENABLE;
+	if (tm)
+		memcpy(&efi_data(op).u.set_wakeup_time, tm, sizeof(*tm));
+	else
+		efi_data(op).misc |= XEN_EFI_SET_WAKEUP_TIME_ENABLE_ONLY;
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	return efi_data(op).status;
+}
+
+static efi_status_t xen_efi_get_variable(efi_char16_t *name, efi_guid_t *vendor,
+					 u32 *attr, unsigned long *data_size,
+					 void *data)
+{
+	struct xen_platform_op op = INIT_EFI_OP(get_variable);
+
+	set_xen_guest_handle(efi_data(op).u.get_variable.name, name);
+	BUILD_BUG_ON(sizeof(*vendor) !=
+		     sizeof(efi_data(op).u.get_variable.vendor_guid));
+	memcpy(&efi_data(op).u.get_variable.vendor_guid, vendor, sizeof(*vendor));
+	efi_data(op).u.get_variable.size = *data_size;
+	set_xen_guest_handle(efi_data(op).u.get_variable.data, data);
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	*data_size = efi_data(op).u.get_variable.size;
+	if (attr)
+		*attr = efi_data(op).misc;
+
+	return efi_data(op).status;
+}
+
+static efi_status_t xen_efi_get_next_variable(unsigned long *name_size,
+					      efi_char16_t *name,
+					      efi_guid_t *vendor)
+{
+	struct xen_platform_op op = INIT_EFI_OP(get_next_variable_name);
+
+	efi_data(op).u.get_next_variable_name.size = *name_size;
+	set_xen_guest_handle(efi_data(op).u.get_next_variable_name.name, name);
+	BUILD_BUG_ON(sizeof(*vendor) !=
+		     sizeof(efi_data(op).u.get_next_variable_name.vendor_guid));
+	memcpy(&efi_data(op).u.get_next_variable_name.vendor_guid, vendor,
+	       sizeof(*vendor));
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	*name_size = efi_data(op).u.get_next_variable_name.size;
+	memcpy(vendor, &efi_data(op).u.get_next_variable_name.vendor_guid,
+	       sizeof(*vendor));
+
+	return efi_data(op).status;
+}
+
+static efi_status_t xen_efi_set_variable(efi_char16_t *name, efi_guid_t *vendor,
+					 u32 attr, unsigned long data_size,
+					 void *data)
+{
+	struct xen_platform_op op = INIT_EFI_OP(set_variable);
+
+	set_xen_guest_handle(efi_data(op).u.set_variable.name, name);
+	efi_data(op).misc = attr;
+	BUILD_BUG_ON(sizeof(*vendor) !=
+		     sizeof(efi_data(op).u.set_variable.vendor_guid));
+	memcpy(&efi_data(op).u.set_variable.vendor_guid, vendor, sizeof(*vendor));
+	efi_data(op).u.set_variable.size = data_size;
+	set_xen_guest_handle(efi_data(op).u.set_variable.data, data);
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	return efi_data(op).status;
+}
+
+static efi_status_t xen_efi_query_variable_info(u32 attr, u64 *storage_space,
+						u64 *remaining_space,
+						u64 *max_variable_size)
+{
+	struct xen_platform_op op = INIT_EFI_OP(query_variable_info);
+
+	if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
+		return EFI_UNSUPPORTED;
+
+	efi_data(op).u.query_variable_info.attr = attr;
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	*storage_space = efi_data(op).u.query_variable_info.max_store_size;
+	*remaining_space = efi_data(op).u.query_variable_info.remain_store_size;
+	*max_variable_size = efi_data(op).u.query_variable_info.max_size;
+
+	return efi_data(op).status;
+}
+
+static efi_status_t xen_efi_get_next_high_mono_count(u32 *count)
+{
+	struct xen_platform_op op = INIT_EFI_OP(get_next_high_monotonic_count);
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	*count = efi_data(op).misc;
+
+	return efi_data(op).status;
+}
+
+static efi_status_t xen_efi_update_capsule(efi_capsule_header_t **capsules,
+				unsigned long count, unsigned long sg_list)
+{
+	struct xen_platform_op op = INIT_EFI_OP(update_capsule);
+
+	if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
+		return EFI_UNSUPPORTED;
+
+	set_xen_guest_handle(efi_data(op).u.update_capsule.capsule_header_array,
+			     capsules);
+	efi_data(op).u.update_capsule.capsule_count = count;
+	efi_data(op).u.update_capsule.sg_list = sg_list;
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	return efi_data(op).status;
+}
+
+static efi_status_t xen_efi_query_capsule_caps(efi_capsule_header_t **capsules,
+			unsigned long count, u64 *max_size, int *reset_type)
+{
+	struct xen_platform_op op = INIT_EFI_OP(query_capsule_capabilities);
+
+	if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
+		return EFI_UNSUPPORTED;
+
+	set_xen_guest_handle(efi_data(op).u.query_capsule_capabilities.capsule_header_array,
+					capsules);
+	efi_data(op).u.query_capsule_capabilities.capsule_count = count;
+
+	if (HYPERVISOR_platform_op(&op) < 0)
+		return EFI_UNSUPPORTED;
+
+	*max_size = efi_data(op).u.query_capsule_capabilities.max_capsule_size;
+	*reset_type = efi_data(op).u.query_capsule_capabilities.reset_type;
+
+	return efi_data(op).status;
+}
+
+static void xen_efi_reset_system(int reset_type, efi_status_t status,
+				 unsigned long data_size, efi_char16_t *data)
+{
+	switch (reset_type) {
+	case EFI_RESET_COLD:
+	case EFI_RESET_WARM:
+		xen_reboot(SHUTDOWN_reboot);
+		break;
+	case EFI_RESET_SHUTDOWN:
+		xen_reboot(SHUTDOWN_poweroff);
+		break;
+	default:
+		BUG();
+	}
+}
+
+/*
+ * Set XEN EFI runtime services function pointers. Other fields of struct efi,
+ * e.g. efi.systab, will be set like normal EFI.
+ */
+void __init xen_efi_runtime_setup(void)
+{
+	efi.get_time			= xen_efi_get_time;
+	efi.set_time			= xen_efi_set_time;
+	efi.get_wakeup_time		= xen_efi_get_wakeup_time;
+	efi.set_wakeup_time		= xen_efi_set_wakeup_time;
+	efi.get_variable		= xen_efi_get_variable;
+	efi.get_next_variable		= xen_efi_get_next_variable;
+	efi.set_variable		= xen_efi_set_variable;
+	efi.set_variable_nonblocking	= xen_efi_set_variable;
+	efi.query_variable_info		= xen_efi_query_variable_info;
+	efi.query_variable_info_nonblocking = xen_efi_query_variable_info;
+	efi.update_capsule		= xen_efi_update_capsule;
+	efi.query_capsule_caps		= xen_efi_query_capsule_caps;
+	efi.get_next_high_mono_count	= xen_efi_get_next_high_mono_count;
+	efi.reset_system		= xen_efi_reset_system;
+}
+
+int efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md)
+{
+	static_assert(XEN_PAGE_SHIFT == EFI_PAGE_SHIFT,
+	              "Mismatch between EFI_PAGE_SHIFT and XEN_PAGE_SHIFT");
+	struct xen_platform_op op;
+	union xenpf_efi_info *info = &op.u.firmware_info.u.efi_info;
+	int rc;
+
+	if (!efi_enabled(EFI_PARAVIRT) || efi_enabled(EFI_MEMMAP))
+		return __efi_mem_desc_lookup(phys_addr, out_md);
+	phys_addr &= ~(u64)(EFI_PAGE_SIZE - 1);
+	op = (struct xen_platform_op) {
+		.cmd = XENPF_firmware_info,
+		.u.firmware_info = {
+			.type = XEN_FW_EFI_INFO,
+			.index = XEN_FW_EFI_MEM_INFO,
+			.u.efi_info.mem.addr = phys_addr,
+			.u.efi_info.mem.size = U64_MAX - phys_addr,
+		},
+	};
+
+	rc = HYPERVISOR_platform_op(&op);
+	if (rc) {
+		pr_warn("Failed to lookup header 0x%llx in Xen memory map: error %d\n",
+		        phys_addr, rc);
+	}
+
+	out_md->phys_addr	= info->mem.addr;
+	out_md->num_pages	= info->mem.size >> EFI_PAGE_SHIFT;
+	out_md->type    	= info->mem.type;
+	out_md->attribute	= info->mem.attr;
+
+	return 0;
+}
+
+bool __init xen_efi_config_table_is_usable(const efi_guid_t *guid,
+                                           unsigned long table)
+{
+	efi_memory_desc_t md;
+	int rc;
+
+	if (!efi_enabled(EFI_PARAVIRT))
+		return true;
+
+	rc = efi_mem_desc_lookup(table, &md);
+	if (rc)
+		return false;
+
+	switch (md.type) {
+	case EFI_RUNTIME_SERVICES_CODE:
+	case EFI_RUNTIME_SERVICES_DATA:
+	case EFI_ACPI_RECLAIM_MEMORY:
+	case EFI_ACPI_MEMORY_NVS:
+	case EFI_RESERVED_TYPE:
+		return true;
+	default:
+		return false;
+	}
+}
diff --git a/drivers/xen/events/Makefile b/drivers/xen/events/Makefile
new file mode 100644
index 000000000..92508d9a6
--- /dev/null
+++ b/drivers/xen/events/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-y += events.o
+
+events-y += events_base.o
+events-y += events_2l.o
+events-y += events_fifo.o
diff --git a/drivers/xen/events/events_2l.c b/drivers/xen/events/events_2l.c
new file mode 100644
index 000000000..e3585330c
--- /dev/null
+++ b/drivers/xen/events/events_2l.c
@@ -0,0 +1,384 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Xen event channels (2-level ABI)
+ *
+ * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/linkage.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+
+#include <asm/sync_bitops.h>
+#include <asm/xen/hypercall.h>
+#include <asm/xen/hypervisor.h>
+
+#include <xen/xen.h>
+#include <xen/xen-ops.h>
+#include <xen/events.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/event_channel.h>
+
+#include "events_internal.h"
+
+/*
+ * Note sizeof(xen_ulong_t) can be more than sizeof(unsigned long). Be
+ * careful to only use bitops which allow for this (e.g
+ * test_bit/find_first_bit and friends but not __ffs) and to pass
+ * BITS_PER_EVTCHN_WORD as the bitmask length.
+ */
+#define BITS_PER_EVTCHN_WORD (sizeof(xen_ulong_t)*8)
+/*
+ * Make a bitmask (i.e. unsigned long *) of a xen_ulong_t
+ * array. Primarily to avoid long lines (hence the terse name).
+ */
+#define BM(x) (unsigned long *)(x)
+/* Find the first set bit in a evtchn mask */
+#define EVTCHN_FIRST_BIT(w) find_first_bit(BM(&(w)), BITS_PER_EVTCHN_WORD)
+
+#define EVTCHN_MASK_SIZE (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)
+
+static DEFINE_PER_CPU(xen_ulong_t [EVTCHN_MASK_SIZE], cpu_evtchn_mask);
+
+static unsigned evtchn_2l_max_channels(void)
+{
+	return EVTCHN_2L_NR_CHANNELS;
+}
+
+static void evtchn_2l_remove(evtchn_port_t evtchn, unsigned int cpu)
+{
+	clear_bit(evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
+}
+
+static void evtchn_2l_bind_to_cpu(evtchn_port_t evtchn, unsigned int cpu,
+				  unsigned int old_cpu)
+{
+	clear_bit(evtchn, BM(per_cpu(cpu_evtchn_mask, old_cpu)));
+	set_bit(evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
+}
+
+static void evtchn_2l_clear_pending(evtchn_port_t port)
+{
+	struct shared_info *s = HYPERVISOR_shared_info;
+	sync_clear_bit(port, BM(&s->evtchn_pending[0]));
+}
+
+static void evtchn_2l_set_pending(evtchn_port_t port)
+{
+	struct shared_info *s = HYPERVISOR_shared_info;
+	sync_set_bit(port, BM(&s->evtchn_pending[0]));
+}
+
+static bool evtchn_2l_is_pending(evtchn_port_t port)
+{
+	struct shared_info *s = HYPERVISOR_shared_info;
+	return sync_test_bit(port, BM(&s->evtchn_pending[0]));
+}
+
+static void evtchn_2l_mask(evtchn_port_t port)
+{
+	struct shared_info *s = HYPERVISOR_shared_info;
+	sync_set_bit(port, BM(&s->evtchn_mask[0]));
+}
+
+static void evtchn_2l_unmask(evtchn_port_t port)
+{
+	struct shared_info *s = HYPERVISOR_shared_info;
+	unsigned int cpu = get_cpu();
+	int do_hypercall = 0, evtchn_pending = 0;
+
+	BUG_ON(!irqs_disabled());
+
+	smp_wmb();	/* All writes before unmask must be visible. */
+
+	if (unlikely((cpu != cpu_from_evtchn(port))))
+		do_hypercall = 1;
+	else {
+		/*
+		 * Need to clear the mask before checking pending to
+		 * avoid a race with an event becoming pending.
+		 *
+		 * EVTCHNOP_unmask will only trigger an upcall if the
+		 * mask bit was set, so if a hypercall is needed
+		 * remask the event.
+		 */
+		sync_clear_bit(port, BM(&s->evtchn_mask[0]));
+		evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));
+
+		if (unlikely(evtchn_pending && xen_hvm_domain())) {
+			sync_set_bit(port, BM(&s->evtchn_mask[0]));
+			do_hypercall = 1;
+		}
+	}
+
+	/* Slow path (hypercall) if this is a non-local port or if this is
+	 * an hvm domain and an event is pending (hvm domains don't have
+	 * their own implementation of irq_enable). */
+	if (do_hypercall) {
+		struct evtchn_unmask unmask = { .port = port };
+		(void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
+	} else {
+		struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
+
+		/*
+		 * The following is basically the equivalent of
+		 * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
+		 * the interrupt edge' if the channel is masked.
+		 */
+		if (evtchn_pending &&
+		    !sync_test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
+					   BM(&vcpu_info->evtchn_pending_sel)))
+			vcpu_info->evtchn_upcall_pending = 1;
+	}
+
+	put_cpu();
+}
+
+static DEFINE_PER_CPU(unsigned int, current_word_idx);
+static DEFINE_PER_CPU(unsigned int, current_bit_idx);
+
+/*
+ * Mask out the i least significant bits of w
+ */
+#define MASK_LSBS(w, i) (w & ((~((xen_ulong_t)0UL)) << i))
+
+static inline xen_ulong_t active_evtchns(unsigned int cpu,
+					 struct shared_info *sh,
+					 unsigned int idx)
+{
+	return sh->evtchn_pending[idx] &
+		per_cpu(cpu_evtchn_mask, cpu)[idx] &
+		~sh->evtchn_mask[idx];
+}
+
+/*
+ * Search the CPU's pending events bitmasks.  For each one found, map
+ * the event number to an irq, and feed it into do_IRQ() for handling.
+ *
+ * Xen uses a two-level bitmap to speed searching.  The first level is
+ * a bitset of words which contain pending event bits.  The second
+ * level is a bitset of pending events themselves.
+ */
+static void evtchn_2l_handle_events(unsigned cpu, struct evtchn_loop_ctrl *ctrl)
+{
+	int irq;
+	xen_ulong_t pending_words;
+	xen_ulong_t pending_bits;
+	int start_word_idx, start_bit_idx;
+	int word_idx, bit_idx;
+	int i;
+	struct shared_info *s = HYPERVISOR_shared_info;
+	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
+	evtchn_port_t evtchn;
+
+	/* Timer interrupt has highest priority. */
+	irq = irq_evtchn_from_virq(cpu, VIRQ_TIMER, &evtchn);
+	if (irq != -1) {
+		word_idx = evtchn / BITS_PER_LONG;
+		bit_idx = evtchn % BITS_PER_LONG;
+		if (active_evtchns(cpu, s, word_idx) & (1ULL << bit_idx))
+			generic_handle_irq(irq);
+	}
+
+	/*
+	 * Master flag must be cleared /before/ clearing
+	 * selector flag. xchg_xen_ulong must contain an
+	 * appropriate barrier.
+	 */
+	pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);
+
+	start_word_idx = __this_cpu_read(current_word_idx);
+	start_bit_idx = __this_cpu_read(current_bit_idx);
+
+	word_idx = start_word_idx;
+
+	for (i = 0; pending_words != 0; i++) {
+		xen_ulong_t words;
+
+		words = MASK_LSBS(pending_words, word_idx);
+
+		/*
+		 * If we masked out all events, wrap to beginning.
+		 */
+		if (words == 0) {
+			word_idx = 0;
+			bit_idx = 0;
+			continue;
+		}
+		word_idx = EVTCHN_FIRST_BIT(words);
+
+		pending_bits = active_evtchns(cpu, s, word_idx);
+		bit_idx = 0; /* usually scan entire word from start */
+		/*
+		 * We scan the starting word in two parts.
+		 *
+		 * 1st time: start in the middle, scanning the
+		 * upper bits.
+		 *
+		 * 2nd time: scan the whole word (not just the
+		 * parts skipped in the first pass) -- if an
+		 * event in the previously scanned bits is
+		 * pending again it would just be scanned on
+		 * the next loop anyway.
+		 */
+		if (word_idx == start_word_idx) {
+			if (i == 0)
+				bit_idx = start_bit_idx;
+		}
+
+		do {
+			xen_ulong_t bits;
+			evtchn_port_t port;
+
+			bits = MASK_LSBS(pending_bits, bit_idx);
+
+			/* If we masked out all events, move on. */
+			if (bits == 0)
+				break;
+
+			bit_idx = EVTCHN_FIRST_BIT(bits);
+
+			/* Process port. */
+			port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
+			handle_irq_for_port(port, ctrl);
+
+			bit_idx = (bit_idx + 1) % BITS_PER_EVTCHN_WORD;
+
+			/* Next caller starts at last processed + 1 */
+			__this_cpu_write(current_word_idx,
+					 bit_idx ? word_idx :
+					 (word_idx+1) % BITS_PER_EVTCHN_WORD);
+			__this_cpu_write(current_bit_idx, bit_idx);
+		} while (bit_idx != 0);
+
+		/* Scan start_l1i twice; all others once. */
+		if ((word_idx != start_word_idx) || (i != 0))
+			pending_words &= ~(1UL << word_idx);
+
+		word_idx = (word_idx + 1) % BITS_PER_EVTCHN_WORD;
+	}
+}
+
+irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
+{
+	struct shared_info *sh = HYPERVISOR_shared_info;
+	int cpu = smp_processor_id();
+	xen_ulong_t *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
+	int i;
+	unsigned long flags;
+	static DEFINE_SPINLOCK(debug_lock);
+	struct vcpu_info *v;
+
+	spin_lock_irqsave(&debug_lock, flags);
+
+	printk("\nvcpu %d\n  ", cpu);
+
+	for_each_online_cpu(i) {
+		int pending;
+		v = per_cpu(xen_vcpu, i);
+		pending = (get_irq_regs() && i == cpu)
+			? xen_irqs_disabled(get_irq_regs())
+			: v->evtchn_upcall_mask;
+		printk("%d: masked=%d pending=%d event_sel %0*"PRI_xen_ulong"\n  ", i,
+		       pending, v->evtchn_upcall_pending,
+		       (int)(sizeof(v->evtchn_pending_sel)*2),
+		       v->evtchn_pending_sel);
+	}
+	v = per_cpu(xen_vcpu, cpu);
+
+	printk("\npending:\n   ");
+	for (i = ARRAY_SIZE(sh->evtchn_pending)-1; i >= 0; i--)
+		printk("%0*"PRI_xen_ulong"%s",
+		       (int)sizeof(sh->evtchn_pending[0])*2,
+		       sh->evtchn_pending[i],
+		       i % 8 == 0 ? "\n   " : " ");
+	printk("\nglobal mask:\n   ");
+	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
+		printk("%0*"PRI_xen_ulong"%s",
+		       (int)(sizeof(sh->evtchn_mask[0])*2),
+		       sh->evtchn_mask[i],
+		       i % 8 == 0 ? "\n   " : " ");
+
+	printk("\nglobally unmasked:\n   ");
+	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
+		printk("%0*"PRI_xen_ulong"%s",
+		       (int)(sizeof(sh->evtchn_mask[0])*2),
+		       sh->evtchn_pending[i] & ~sh->evtchn_mask[i],
+		       i % 8 == 0 ? "\n   " : " ");
+
+	printk("\nlocal cpu%d mask:\n   ", cpu);
+	for (i = (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
+		printk("%0*"PRI_xen_ulong"%s", (int)(sizeof(cpu_evtchn[0])*2),
+		       cpu_evtchn[i],
+		       i % 8 == 0 ? "\n   " : " ");
+
+	printk("\nlocally unmasked:\n   ");
+	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--) {
+		xen_ulong_t pending = sh->evtchn_pending[i]
+			& ~sh->evtchn_mask[i]
+			& cpu_evtchn[i];
+		printk("%0*"PRI_xen_ulong"%s",
+		       (int)(sizeof(sh->evtchn_mask[0])*2),
+		       pending, i % 8 == 0 ? "\n   " : " ");
+	}
+
+	printk("\npending list:\n");
+	for (i = 0; i < EVTCHN_2L_NR_CHANNELS; i++) {
+		if (sync_test_bit(i, BM(sh->evtchn_pending))) {
+			int word_idx = i / BITS_PER_EVTCHN_WORD;
+			printk("  %d: event %d -> irq %u%s%s%s\n",
+			       cpu_from_evtchn(i), i,
+			       irq_from_evtchn(i),
+			       sync_test_bit(word_idx, BM(&v->evtchn_pending_sel))
+			       ? "" : " l2-clear",
+			       !sync_test_bit(i, BM(sh->evtchn_mask))
+			       ? "" : " globally-masked",
+			       sync_test_bit(i, BM(cpu_evtchn))
+			       ? "" : " locally-masked");
+		}
+	}
+
+	spin_unlock_irqrestore(&debug_lock, flags);
+
+	return IRQ_HANDLED;
+}
+
+static void evtchn_2l_resume(void)
+{
+	int i;
+
+	for_each_online_cpu(i)
+		memset(per_cpu(cpu_evtchn_mask, i), 0, sizeof(xen_ulong_t) *
+				EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD);
+}
+
+static int evtchn_2l_percpu_deinit(unsigned int cpu)
+{
+	memset(per_cpu(cpu_evtchn_mask, cpu), 0, sizeof(xen_ulong_t) *
+			EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD);
+
+	return 0;
+}
+
+static const struct evtchn_ops evtchn_ops_2l = {
+	.max_channels      = evtchn_2l_max_channels,
+	.nr_channels       = evtchn_2l_max_channels,
+	.remove            = evtchn_2l_remove,
+	.bind_to_cpu       = evtchn_2l_bind_to_cpu,
+	.clear_pending     = evtchn_2l_clear_pending,
+	.set_pending       = evtchn_2l_set_pending,
+	.is_pending        = evtchn_2l_is_pending,
+	.mask              = evtchn_2l_mask,
+	.unmask            = evtchn_2l_unmask,
+	.handle_events     = evtchn_2l_handle_events,
+	.resume	           = evtchn_2l_resume,
+	.percpu_deinit     = evtchn_2l_percpu_deinit,
+};
+
+void __init xen_evtchn_2l_init(void)
+{
+	pr_info("Using 2-level ABI\n");
+	evtchn_ops = &evtchn_ops_2l;
+}
diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
new file mode 100644
index 000000000..fd16d652c
--- /dev/null
+++ b/drivers/xen/events/events_base.c
@@ -0,0 +1,2327 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Xen event channels
+ *
+ * Xen models interrupts with abstract event channels.  Because each
+ * domain gets 1024 event channels, but NR_IRQ is not that large, we
+ * must dynamically map irqs<->event channels.  The event channels
+ * interface with the rest of the kernel by defining a xen interrupt
+ * chip.  When an event is received, it is mapped to an irq and sent
+ * through the normal interrupt processing path.
+ *
+ * There are four kinds of events which can be mapped to an event
+ * channel:
+ *
+ * 1. Inter-domain notifications.  This includes all the virtual
+ *    device events, since they're driven by front-ends in another domain
+ *    (typically dom0).
+ * 2. VIRQs, typically used for timers.  These are per-cpu events.
+ * 3. IPIs.
+ * 4. PIRQs - Hardware interrupts.
+ *
+ * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/linkage.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/moduleparam.h>
+#include <linux/string.h>
+#include <linux/memblock.h>
+#include <linux/slab.h>
+#include <linux/irqnr.h>
+#include <linux/pci.h>
+#include <linux/rcupdate.h>
+#include <linux/spinlock.h>
+#include <linux/cpuhotplug.h>
+#include <linux/atomic.h>
+#include <linux/ktime.h>
+
+#ifdef CONFIG_X86
+#include <asm/cpuid/api.h>
+#include <asm/desc.h>
+#include <asm/ptrace.h>
+#include <asm/idtentry.h>
+#include <asm/irq.h>
+#include <asm/io_apic.h>
+#include <asm/i8259.h>
+#include <asm/xen/cpuid.h>
+#include <asm/xen/pci.h>
+#endif
+#include <asm/sync_bitops.h>
+#include <asm/xen/hypercall.h>
+#include <asm/xen/hypervisor.h>
+#include <xen/page.h>
+
+#include <xen/xen.h>
+#include <xen/hvm.h>
+#include <xen/xen-ops.h>
+#include <xen/events.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/event_channel.h>
+#include <xen/interface/hvm/hvm_op.h>
+#include <xen/interface/hvm/params.h>
+#include <xen/interface/physdev.h>
+#include <xen/interface/sched.h>
+#include <xen/interface/vcpu.h>
+#include <xen/xenbus.h>
+#include <asm/hw_irq.h>
+
+#include "events_internal.h"
+
+#undef MODULE_PARAM_PREFIX
+#define MODULE_PARAM_PREFIX "xen."
+
+/* Interrupt types. */
+enum xen_irq_type {
+	IRQT_UNBOUND = 0,
+	IRQT_PIRQ,
+	IRQT_VIRQ,
+	IRQT_IPI,
+	IRQT_EVTCHN
+};
+
+/*
+ * Packed IRQ information:
+ * type - enum xen_irq_type
+ * event channel - irq->event channel mapping
+ * cpu - cpu this event channel is bound to
+ * index - type-specific information:
+ *    PIRQ - vector, with MSB being "needs EIO", or physical IRQ of the HVM
+ *           guest, or GSI (real passthrough IRQ) of the device.
+ *    VIRQ - virq number
+ *    IPI - IPI vector
+ *    EVTCHN -
+ */
+struct irq_info {
+	struct list_head list;
+	struct list_head eoi_list;
+	struct rcu_work rwork;
+	short refcnt;
+	u8 spurious_cnt;
+	u8 is_accounted;
+	short type;		/* type: IRQT_* */
+	u8 mask_reason;		/* Why is event channel masked */
+#define EVT_MASK_REASON_EXPLICIT	0x01
+#define EVT_MASK_REASON_TEMPORARY	0x02
+#define EVT_MASK_REASON_EOI_PENDING	0x04
+	u8 is_active;		/* Is event just being handled? */
+	unsigned irq;
+	evtchn_port_t evtchn;   /* event channel */
+	unsigned short cpu;     /* cpu bound */
+	unsigned short eoi_cpu; /* EOI must happen on this cpu-1 */
+	unsigned int irq_epoch; /* If eoi_cpu valid: irq_epoch of event */
+	u64 eoi_time;           /* Time in jiffies when to EOI. */
+	raw_spinlock_t lock;
+	bool is_static;           /* Is event channel static */
+
+	union {
+		unsigned short virq;
+		enum ipi_vector ipi;
+		struct {
+			unsigned short pirq;
+			unsigned short gsi;
+			unsigned char vector;
+			unsigned char flags;
+			uint16_t domid;
+		} pirq;
+		struct xenbus_device *interdomain;
+	} u;
+};
+
+#define PIRQ_NEEDS_EOI	(1 << 0)
+#define PIRQ_SHAREABLE	(1 << 1)
+#define PIRQ_MSI_GROUP	(1 << 2)
+
+static uint __read_mostly event_loop_timeout = 2;
+module_param(event_loop_timeout, uint, 0644);
+
+static uint __read_mostly event_eoi_delay = 10;
+module_param(event_eoi_delay, uint, 0644);
+
+const struct evtchn_ops *evtchn_ops;
+
+/*
+ * This lock protects updates to the following mapping and reference-count
+ * arrays. The lock does not need to be acquired to read the mapping tables.
+ */
+static DEFINE_MUTEX(irq_mapping_update_lock);
+
+/*
+ * Lock hierarchy:
+ *
+ * irq_mapping_update_lock
+ *   IRQ-desc lock
+ *     percpu eoi_list_lock
+ *       irq_info->lock
+ */
+
+static LIST_HEAD(xen_irq_list_head);
+
+/* IRQ <-> VIRQ mapping. */
+static DEFINE_PER_CPU(int [NR_VIRQS], virq_to_irq) = {[0 ... NR_VIRQS-1] = -1};
+
+/* IRQ <-> IPI mapping */
+static DEFINE_PER_CPU(int [XEN_NR_IPIS], ipi_to_irq) = {[0 ... XEN_NR_IPIS-1] = -1};
+/* Cache for IPI event channels - needed for hot cpu unplug (avoid RCU usage). */
+static DEFINE_PER_CPU(evtchn_port_t [XEN_NR_IPIS], ipi_to_evtchn) = {[0 ... XEN_NR_IPIS-1] = 0};
+
+/* Event channel distribution data */
+static atomic_t channels_on_cpu[NR_CPUS];
+
+static int **evtchn_to_irq;
+#ifdef CONFIG_X86
+static unsigned long *pirq_eoi_map;
+#endif
+static bool (*pirq_needs_eoi)(struct irq_info *info);
+
+#define EVTCHN_ROW(e)  (e / (PAGE_SIZE/sizeof(**evtchn_to_irq)))
+#define EVTCHN_COL(e)  (e % (PAGE_SIZE/sizeof(**evtchn_to_irq)))
+#define EVTCHN_PER_ROW (PAGE_SIZE / sizeof(**evtchn_to_irq))
+
+/* Xen will never allocate port zero for any purpose. */
+#define VALID_EVTCHN(chn)	((chn) != 0)
+
+static struct irq_info *legacy_info_ptrs[NR_IRQS_LEGACY];
+
+static struct irq_chip xen_dynamic_chip;
+static struct irq_chip xen_lateeoi_chip;
+static struct irq_chip xen_percpu_chip;
+static struct irq_chip xen_pirq_chip;
+static void enable_dynirq(struct irq_data *data);
+
+static DEFINE_PER_CPU(unsigned int, irq_epoch);
+
+static void clear_evtchn_to_irq_row(int *evtchn_row)
+{
+	unsigned col;
+
+	for (col = 0; col < EVTCHN_PER_ROW; col++)
+		WRITE_ONCE(evtchn_row[col], -1);
+}
+
+static void clear_evtchn_to_irq_all(void)
+{
+	unsigned row;
+
+	for (row = 0; row < EVTCHN_ROW(xen_evtchn_max_channels()); row++) {
+		if (evtchn_to_irq[row] == NULL)
+			continue;
+		clear_evtchn_to_irq_row(evtchn_to_irq[row]);
+	}
+}
+
+static int set_evtchn_to_irq(evtchn_port_t evtchn, unsigned int irq)
+{
+	unsigned row;
+	unsigned col;
+	int *evtchn_row;
+
+	if (evtchn >= xen_evtchn_max_channels())
+		return -EINVAL;
+
+	row = EVTCHN_ROW(evtchn);
+	col = EVTCHN_COL(evtchn);
+
+	if (evtchn_to_irq[row] == NULL) {
+		/* Unallocated irq entries return -1 anyway */
+		if (irq == -1)
+			return 0;
+
+		evtchn_row = (int *) __get_free_pages(GFP_KERNEL, 0);
+		if (evtchn_row == NULL)
+			return -ENOMEM;
+
+		clear_evtchn_to_irq_row(evtchn_row);
+
+		/*
+		 * We've prepared an empty row for the mapping. If a different
+		 * thread was faster inserting it, we can drop ours.
+		 */
+		if (cmpxchg(&evtchn_to_irq[row], NULL, evtchn_row) != NULL)
+			free_page((unsigned long) evtchn_row);
+	}
+
+	WRITE_ONCE(evtchn_to_irq[row][col], irq);
+	return 0;
+}
+
+/* Get info for IRQ */
+static struct irq_info *info_for_irq(unsigned irq)
+{
+	if (irq < nr_legacy_irqs())
+		return legacy_info_ptrs[irq];
+	else
+		return irq_get_chip_data(irq);
+}
+
+static void set_info_for_irq(unsigned int irq, struct irq_info *info)
+{
+	if (irq < nr_legacy_irqs())
+		legacy_info_ptrs[irq] = info;
+	else
+		irq_set_chip_data(irq, info);
+}
+
+static struct irq_info *evtchn_to_info(evtchn_port_t evtchn)
+{
+	int irq;
+
+	if (evtchn >= xen_evtchn_max_channels())
+		return NULL;
+	if (evtchn_to_irq[EVTCHN_ROW(evtchn)] == NULL)
+		return NULL;
+	irq = READ_ONCE(evtchn_to_irq[EVTCHN_ROW(evtchn)][EVTCHN_COL(evtchn)]);
+
+	return (irq < 0) ? NULL : info_for_irq(irq);
+}
+
+/* Per CPU channel accounting */
+static void channels_on_cpu_dec(struct irq_info *info)
+{
+	if (!info->is_accounted)
+		return;
+
+	info->is_accounted = 0;
+
+	if (WARN_ON_ONCE(info->cpu >= nr_cpu_ids))
+		return;
+
+	WARN_ON_ONCE(!atomic_add_unless(&channels_on_cpu[info->cpu], -1 , 0));
+}
+
+static void channels_on_cpu_inc(struct irq_info *info)
+{
+	if (WARN_ON_ONCE(info->cpu >= nr_cpu_ids))
+		return;
+
+	if (WARN_ON_ONCE(!atomic_add_unless(&channels_on_cpu[info->cpu], 1,
+					    INT_MAX)))
+		return;
+
+	info->is_accounted = 1;
+}
+
+static void xen_irq_free_desc(unsigned int irq)
+{
+	/* Legacy IRQ descriptors are managed by the arch. */
+	if (irq >= nr_legacy_irqs())
+		irq_free_desc(irq);
+}
+
+static void delayed_free_irq(struct work_struct *work)
+{
+	struct irq_info *info = container_of(to_rcu_work(work), struct irq_info,
+					     rwork);
+	unsigned int irq = info->irq;
+
+	/* Remove the info pointer only now, with no potential users left. */
+	set_info_for_irq(irq, NULL);
+
+	kfree(info);
+
+	xen_irq_free_desc(irq);
+}
+
+/* Constructors for packed IRQ information. */
+static int xen_irq_info_common_setup(struct irq_info *info,
+				     enum xen_irq_type type,
+				     evtchn_port_t evtchn,
+				     unsigned short cpu)
+{
+	int ret;
+
+	BUG_ON(info->type != IRQT_UNBOUND && info->type != type);
+
+	info->type = type;
+	info->evtchn = evtchn;
+	info->cpu = cpu;
+	info->mask_reason = EVT_MASK_REASON_EXPLICIT;
+	raw_spin_lock_init(&info->lock);
+
+	ret = set_evtchn_to_irq(evtchn, info->irq);
+	if (ret < 0)
+		return ret;
+
+	irq_clear_status_flags(info->irq, IRQ_NOREQUEST | IRQ_NOAUTOEN);
+
+	return xen_evtchn_port_setup(evtchn);
+}
+
+static int xen_irq_info_evtchn_setup(struct irq_info *info,
+				     evtchn_port_t evtchn,
+				     struct xenbus_device *dev)
+{
+	int ret;
+
+	ret = xen_irq_info_common_setup(info, IRQT_EVTCHN, evtchn, 0);
+	info->u.interdomain = dev;
+	if (dev)
+		atomic_inc(&dev->event_channels);
+
+	return ret;
+}
+
+static int xen_irq_info_ipi_setup(struct irq_info *info, unsigned int cpu,
+				  evtchn_port_t evtchn, enum ipi_vector ipi)
+{
+	info->u.ipi = ipi;
+
+	per_cpu(ipi_to_irq, cpu)[ipi] = info->irq;
+	per_cpu(ipi_to_evtchn, cpu)[ipi] = evtchn;
+
+	return xen_irq_info_common_setup(info, IRQT_IPI, evtchn, 0);
+}
+
+static int xen_irq_info_virq_setup(struct irq_info *info, unsigned int cpu,
+				   evtchn_port_t evtchn, unsigned int virq)
+{
+	info->u.virq = virq;
+
+	per_cpu(virq_to_irq, cpu)[virq] = info->irq;
+
+	return xen_irq_info_common_setup(info, IRQT_VIRQ, evtchn, 0);
+}
+
+static int xen_irq_info_pirq_setup(struct irq_info *info, evtchn_port_t evtchn,
+				   unsigned int pirq, unsigned int gsi,
+				   uint16_t domid, unsigned char flags)
+{
+	info->u.pirq.pirq = pirq;
+	info->u.pirq.gsi = gsi;
+	info->u.pirq.domid = domid;
+	info->u.pirq.flags = flags;
+
+	return xen_irq_info_common_setup(info, IRQT_PIRQ, evtchn, 0);
+}
+
+static void xen_irq_info_cleanup(struct irq_info *info)
+{
+	set_evtchn_to_irq(info->evtchn, -1);
+	xen_evtchn_port_remove(info->evtchn, info->cpu);
+	info->evtchn = 0;
+	channels_on_cpu_dec(info);
+}
+
+/*
+ * Accessors for packed IRQ information.
+ */
+static evtchn_port_t evtchn_from_irq(unsigned int irq)
+{
+	const struct irq_info *info = NULL;
+
+	if (likely(irq < irq_get_nr_irqs()))
+		info = info_for_irq(irq);
+	if (!info)
+		return 0;
+
+	return info->evtchn;
+}
+
+unsigned int irq_from_evtchn(evtchn_port_t evtchn)
+{
+	struct irq_info *info = evtchn_to_info(evtchn);
+
+	return info ? info->irq : -1;
+}
+EXPORT_SYMBOL_GPL(irq_from_evtchn);
+
+int irq_evtchn_from_virq(unsigned int cpu, unsigned int virq,
+			 evtchn_port_t *evtchn)
+{
+	int irq = per_cpu(virq_to_irq, cpu)[virq];
+
+	*evtchn = evtchn_from_irq(irq);
+
+	return irq;
+}
+
+static enum ipi_vector ipi_from_irq(struct irq_info *info)
+{
+	BUG_ON(info == NULL);
+	BUG_ON(info->type != IRQT_IPI);
+
+	return info->u.ipi;
+}
+
+static unsigned int virq_from_irq(struct irq_info *info)
+{
+	BUG_ON(info == NULL);
+	BUG_ON(info->type != IRQT_VIRQ);
+
+	return info->u.virq;
+}
+
+static unsigned int pirq_from_irq(struct irq_info *info)
+{
+	BUG_ON(info == NULL);
+	BUG_ON(info->type != IRQT_PIRQ);
+
+	return info->u.pirq.pirq;
+}
+
+unsigned int cpu_from_evtchn(evtchn_port_t evtchn)
+{
+	struct irq_info *info = evtchn_to_info(evtchn);
+
+	return info ? info->cpu : 0;
+}
+
+static void do_mask(struct irq_info *info, u8 reason)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&info->lock, flags);
+
+	if (!info->mask_reason)
+		mask_evtchn(info->evtchn);
+
+	info->mask_reason |= reason;
+
+	raw_spin_unlock_irqrestore(&info->lock, flags);
+}
+
+static void do_unmask(struct irq_info *info, u8 reason)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&info->lock, flags);
+
+	info->mask_reason &= ~reason;
+
+	if (!info->mask_reason)
+		unmask_evtchn(info->evtchn);
+
+	raw_spin_unlock_irqrestore(&info->lock, flags);
+}
+
+#ifdef CONFIG_X86
+static bool pirq_check_eoi_map(struct irq_info *info)
+{
+	return test_bit(pirq_from_irq(info), pirq_eoi_map);
+}
+#endif
+
+static bool pirq_needs_eoi_flag(struct irq_info *info)
+{
+	BUG_ON(info->type != IRQT_PIRQ);
+
+	return info->u.pirq.flags & PIRQ_NEEDS_EOI;
+}
+
+static void bind_evtchn_to_cpu(struct irq_info *info, unsigned int cpu,
+			       bool force_affinity)
+{
+	if (IS_ENABLED(CONFIG_SMP) && force_affinity) {
+		struct irq_data *data = irq_get_irq_data(info->irq);
+
+		irq_data_update_affinity(data, cpumask_of(cpu));
+		irq_data_update_effective_affinity(data, cpumask_of(cpu));
+	}
+
+	xen_evtchn_port_bind_to_cpu(info->evtchn, cpu, info->cpu);
+
+	channels_on_cpu_dec(info);
+	info->cpu = cpu;
+	channels_on_cpu_inc(info);
+}
+
+/**
+ * notify_remote_via_irq - send event to remote end of event channel via irq
+ * @irq: irq of event channel to send event to
+ *
+ * Unlike notify_remote_via_evtchn(), this is safe to use across
+ * save/restore. Notifications on a broken connection are silently
+ * dropped.
+ */
+void notify_remote_via_irq(int irq)
+{
+	evtchn_port_t evtchn = evtchn_from_irq(irq);
+
+	if (VALID_EVTCHN(evtchn))
+		notify_remote_via_evtchn(evtchn);
+}
+EXPORT_SYMBOL_GPL(notify_remote_via_irq);
+
+struct lateeoi_work {
+	struct delayed_work delayed;
+	spinlock_t eoi_list_lock;
+	struct list_head eoi_list;
+};
+
+static DEFINE_PER_CPU(struct lateeoi_work, lateeoi);
+
+static void lateeoi_list_del(struct irq_info *info)
+{
+	struct lateeoi_work *eoi = &per_cpu(lateeoi, info->eoi_cpu);
+	unsigned long flags;
+
+	spin_lock_irqsave(&eoi->eoi_list_lock, flags);
+	list_del_init(&info->eoi_list);
+	spin_unlock_irqrestore(&eoi->eoi_list_lock, flags);
+}
+
+static void lateeoi_list_add(struct irq_info *info)
+{
+	struct lateeoi_work *eoi = &per_cpu(lateeoi, info->eoi_cpu);
+	struct irq_info *elem;
+	u64 now = get_jiffies_64();
+	unsigned long delay;
+	unsigned long flags;
+
+	if (now < info->eoi_time)
+		delay = info->eoi_time - now;
+	else
+		delay = 1;
+
+	spin_lock_irqsave(&eoi->eoi_list_lock, flags);
+
+	elem = list_first_entry_or_null(&eoi->eoi_list, struct irq_info,
+					eoi_list);
+	if (!elem || info->eoi_time < elem->eoi_time) {
+		list_add(&info->eoi_list, &eoi->eoi_list);
+		mod_delayed_work_on(info->eoi_cpu, system_percpu_wq,
+				    &eoi->delayed, delay);
+	} else {
+		list_for_each_entry_reverse(elem, &eoi->eoi_list, eoi_list) {
+			if (elem->eoi_time <= info->eoi_time)
+				break;
+		}
+		list_add(&info->eoi_list, &elem->eoi_list);
+	}
+
+	spin_unlock_irqrestore(&eoi->eoi_list_lock, flags);
+}
+
+static void xen_irq_lateeoi_locked(struct irq_info *info, bool spurious)
+{
+	evtchn_port_t evtchn;
+	unsigned int cpu;
+	unsigned int delay = 0;
+
+	evtchn = info->evtchn;
+	if (!VALID_EVTCHN(evtchn) || !list_empty(&info->eoi_list))
+		return;
+
+	if (spurious) {
+		struct xenbus_device *dev = info->u.interdomain;
+		unsigned int threshold = 1;
+
+		if (dev && dev->spurious_threshold)
+			threshold = dev->spurious_threshold;
+
+		if ((1 << info->spurious_cnt) < (HZ << 2)) {
+			if (info->spurious_cnt != 0xFF)
+				info->spurious_cnt++;
+		}
+		if (info->spurious_cnt > threshold) {
+			delay = 1 << (info->spurious_cnt - 1 - threshold);
+			if (delay > HZ)
+				delay = HZ;
+			if (!info->eoi_time)
+				info->eoi_cpu = smp_processor_id();
+			info->eoi_time = get_jiffies_64() + delay;
+			if (dev)
+				atomic_add(delay, &dev->jiffies_eoi_delayed);
+		}
+		if (dev)
+			atomic_inc(&dev->spurious_events);
+	} else {
+		info->spurious_cnt = 0;
+	}
+
+	cpu = info->eoi_cpu;
+	if (info->eoi_time &&
+	    (info->irq_epoch == per_cpu(irq_epoch, cpu) || delay)) {
+		lateeoi_list_add(info);
+		return;
+	}
+
+	info->eoi_time = 0;
+
+	/* is_active hasn't been reset yet, do it now. */
+	smp_store_release(&info->is_active, 0);
+	do_unmask(info, EVT_MASK_REASON_EOI_PENDING);
+}
+
+static void xen_irq_lateeoi_worker(struct work_struct *work)
+{
+	struct lateeoi_work *eoi;
+	struct irq_info *info;
+	u64 now = get_jiffies_64();
+	unsigned long flags;
+
+	eoi = container_of(to_delayed_work(work), struct lateeoi_work, delayed);
+
+	rcu_read_lock();
+
+	while (true) {
+		spin_lock_irqsave(&eoi->eoi_list_lock, flags);
+
+		info = list_first_entry_or_null(&eoi->eoi_list, struct irq_info,
+						eoi_list);
+
+		if (info == NULL)
+			break;
+
+		if (now < info->eoi_time) {
+			mod_delayed_work_on(info->eoi_cpu, system_percpu_wq,
+					    &eoi->delayed,
+					    info->eoi_time - now);
+			break;
+		}
+
+		list_del_init(&info->eoi_list);
+
+		spin_unlock_irqrestore(&eoi->eoi_list_lock, flags);
+
+		info->eoi_time = 0;
+
+		xen_irq_lateeoi_locked(info, false);
+	}
+
+	spin_unlock_irqrestore(&eoi->eoi_list_lock, flags);
+
+	rcu_read_unlock();
+}
+
+static void xen_cpu_init_eoi(unsigned int cpu)
+{
+	struct lateeoi_work *eoi = &per_cpu(lateeoi, cpu);
+
+	INIT_DELAYED_WORK(&eoi->delayed, xen_irq_lateeoi_worker);
+	spin_lock_init(&eoi->eoi_list_lock);
+	INIT_LIST_HEAD(&eoi->eoi_list);
+}
+
+void xen_irq_lateeoi(unsigned int irq, unsigned int eoi_flags)
+{
+	struct irq_info *info;
+
+	rcu_read_lock();
+
+	info = info_for_irq(irq);
+
+	if (info)
+		xen_irq_lateeoi_locked(info, eoi_flags & XEN_EOI_FLAG_SPURIOUS);
+
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(xen_irq_lateeoi);
+
+static struct irq_info *xen_irq_init(unsigned int irq)
+{
+	struct irq_info *info;
+
+	info = kzalloc_obj(*info);
+	if (info) {
+		info->irq = irq;
+		info->type = IRQT_UNBOUND;
+		info->refcnt = -1;
+		INIT_RCU_WORK(&info->rwork, delayed_free_irq);
+
+		set_info_for_irq(irq, info);
+		INIT_LIST_HEAD(&info->eoi_list);
+		list_add_tail(&info->list, &xen_irq_list_head);
+	}
+
+	return info;
+}
+
+static struct irq_info *xen_allocate_irq_dynamic(void)
+{
+	int irq = irq_alloc_desc_from(0, -1);
+	struct irq_info *info = NULL;
+
+	if (irq >= 0) {
+		info = xen_irq_init(irq);
+		if (!info)
+			xen_irq_free_desc(irq);
+	}
+
+	return info;
+}
+
+static struct irq_info *xen_allocate_irq_gsi(unsigned int gsi)
+{
+	int irq;
+	struct irq_info *info;
+
+	/*
+	 * A PV guest has no concept of a GSI (since it has no ACPI
+	 * nor access to/knowledge of the physical APICs). Therefore
+	 * all IRQs are dynamically allocated from the entire IRQ
+	 * space.
+	 */
+	if (xen_pv_domain() && !xen_initial_domain())
+		return xen_allocate_irq_dynamic();
+
+	/* Legacy IRQ descriptors are already allocated by the arch. */
+	if (gsi < nr_legacy_irqs())
+		irq = gsi;
+	else
+		irq = irq_alloc_desc_at(gsi, -1);
+
+	info = xen_irq_init(irq);
+	if (!info)
+		xen_irq_free_desc(irq);
+
+	return info;
+}
+
+static void xen_free_irq(struct irq_info *info)
+{
+	if (WARN_ON(!info))
+		return;
+
+	if (!list_empty(&info->eoi_list))
+		lateeoi_list_del(info);
+
+	list_del(&info->list);
+
+	WARN_ON(info->refcnt > 0);
+
+	queue_rcu_work(system_percpu_wq, &info->rwork);
+}
+
+/* Not called for lateeoi events. */
+static void event_handler_exit(struct irq_info *info)
+{
+	smp_store_release(&info->is_active, 0);
+	clear_evtchn(info->evtchn);
+}
+
+static void pirq_query_unmask(struct irq_info *info)
+{
+	struct physdev_irq_status_query irq_status;
+
+	irq_status.irq = pirq_from_irq(info);
+	if (HYPERVISOR_physdev_op(PHYSDEVOP_irq_status_query, &irq_status))
+		irq_status.flags = 0;
+
+	info->u.pirq.flags &= ~PIRQ_NEEDS_EOI;
+	if (irq_status.flags & XENIRQSTAT_needs_eoi)
+		info->u.pirq.flags |= PIRQ_NEEDS_EOI;
+}
+
+static void do_eoi_pirq(struct irq_info *info)
+{
+	struct physdev_eoi eoi = { .irq = pirq_from_irq(info) };
+	int rc = 0;
+
+	if (!VALID_EVTCHN(info->evtchn))
+		return;
+
+	event_handler_exit(info);
+
+	if (pirq_needs_eoi(info)) {
+		rc = HYPERVISOR_physdev_op(PHYSDEVOP_eoi, &eoi);
+		WARN_ON(rc);
+	}
+}
+
+static void eoi_pirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+
+	do_eoi_pirq(info);
+}
+
+static void do_disable_dynirq(struct irq_info *info)
+{
+	if (VALID_EVTCHN(info->evtchn))
+		do_mask(info, EVT_MASK_REASON_EXPLICIT);
+}
+
+static void disable_dynirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+
+	if (info)
+		do_disable_dynirq(info);
+}
+
+static void mask_ack_pirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+
+	if (info) {
+		do_disable_dynirq(info);
+		do_eoi_pirq(info);
+	}
+}
+
+static unsigned int __startup_pirq(struct irq_info *info)
+{
+	struct evtchn_bind_pirq bind_pirq;
+	evtchn_port_t evtchn = info->evtchn;
+	int rc;
+
+	if (VALID_EVTCHN(evtchn))
+		goto out;
+
+	bind_pirq.pirq = pirq_from_irq(info);
+	/* NB. We are happy to share unless we are probing. */
+	bind_pirq.flags = info->u.pirq.flags & PIRQ_SHAREABLE ?
+					BIND_PIRQ__WILL_SHARE : 0;
+	rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_pirq, &bind_pirq);
+	if (rc != 0) {
+		pr_warn("Failed to obtain physical IRQ %d\n", info->irq);
+		return 0;
+	}
+	evtchn = bind_pirq.port;
+
+	pirq_query_unmask(info);
+
+	rc = set_evtchn_to_irq(evtchn, info->irq);
+	if (rc)
+		goto err;
+
+	info->evtchn = evtchn;
+	bind_evtchn_to_cpu(info, 0, false);
+
+	rc = xen_evtchn_port_setup(evtchn);
+	if (rc)
+		goto err;
+
+out:
+	do_unmask(info, EVT_MASK_REASON_EXPLICIT);
+
+	do_eoi_pirq(info);
+
+	return 0;
+
+err:
+	pr_err("irq%d: Failed to set port to irq mapping (%d)\n", info->irq,
+	       rc);
+	xen_evtchn_close(evtchn);
+	return 0;
+}
+
+static unsigned int startup_pirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+
+	return __startup_pirq(info);
+}
+
+static void shutdown_pirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+	evtchn_port_t evtchn = info->evtchn;
+
+	BUG_ON(info->type != IRQT_PIRQ);
+
+	if (!VALID_EVTCHN(evtchn))
+		return;
+
+	do_mask(info, EVT_MASK_REASON_EXPLICIT);
+	xen_irq_info_cleanup(info);
+	xen_evtchn_close(evtchn);
+}
+
+static void enable_pirq(struct irq_data *data)
+{
+	enable_dynirq(data);
+}
+
+static void disable_pirq(struct irq_data *data)
+{
+	disable_dynirq(data);
+}
+
+int xen_irq_from_gsi(unsigned gsi)
+{
+	struct irq_info *info;
+
+	list_for_each_entry(info, &xen_irq_list_head, list) {
+		if (info->type != IRQT_PIRQ)
+			continue;
+
+		if (info->u.pirq.gsi == gsi)
+			return info->irq;
+	}
+
+	return -1;
+}
+EXPORT_SYMBOL_GPL(xen_irq_from_gsi);
+
+static void __unbind_from_irq(struct irq_info *info, unsigned int irq)
+{
+	evtchn_port_t evtchn;
+	bool close_evtchn = false;
+
+	if (!info) {
+		xen_irq_free_desc(irq);
+		return;
+	}
+
+	if (info->refcnt > 0) {
+		info->refcnt--;
+		if (info->refcnt != 0)
+			return;
+	}
+
+	evtchn = info->evtchn;
+
+	if (VALID_EVTCHN(evtchn)) {
+		unsigned int cpu = info->cpu;
+		struct xenbus_device *dev;
+
+		if (!info->is_static)
+			close_evtchn = true;
+
+		switch (info->type) {
+		case IRQT_VIRQ:
+			per_cpu(virq_to_irq, cpu)[virq_from_irq(info)] = -1;
+			break;
+		case IRQT_IPI:
+			per_cpu(ipi_to_irq, cpu)[ipi_from_irq(info)] = -1;
+			per_cpu(ipi_to_evtchn, cpu)[ipi_from_irq(info)] = 0;
+			break;
+		case IRQT_EVTCHN:
+			dev = info->u.interdomain;
+			if (dev)
+				atomic_dec(&dev->event_channels);
+			break;
+		default:
+			break;
+		}
+
+		xen_irq_info_cleanup(info);
+
+		if (close_evtchn)
+			xen_evtchn_close(evtchn);
+	}
+
+	xen_free_irq(info);
+}
+
+/*
+ * Do not make any assumptions regarding the relationship between the
+ * IRQ number returned here and the Xen pirq argument.
+ *
+ * Note: We don't assign an event channel until the irq actually started
+ * up.  Return an existing irq if we've already got one for the gsi.
+ *
+ * Shareable implies level triggered, not shareable implies edge
+ * triggered here.
+ */
+int xen_bind_pirq_gsi_to_irq(unsigned gsi,
+			     unsigned pirq, int shareable, char *name)
+{
+	struct irq_info *info;
+	struct physdev_irq irq_op;
+	int ret;
+
+	mutex_lock(&irq_mapping_update_lock);
+
+	ret = xen_irq_from_gsi(gsi);
+	if (ret != -1) {
+		pr_info("%s: returning irq %d for gsi %u\n",
+			__func__, ret, gsi);
+		goto out;
+	}
+
+	info = xen_allocate_irq_gsi(gsi);
+	if (!info)
+		goto out;
+
+	irq_op.irq = info->irq;
+	irq_op.vector = 0;
+
+	/* Only the privileged domain can do this. For non-priv, the pcifront
+	 * driver provides a PCI bus that does the call to do exactly
+	 * this in the priv domain. */
+	if (xen_initial_domain() &&
+	    HYPERVISOR_physdev_op(PHYSDEVOP_alloc_irq_vector, &irq_op)) {
+		xen_free_irq(info);
+		ret = -ENOSPC;
+		goto out;
+	}
+
+	ret = xen_irq_info_pirq_setup(info, 0, pirq, gsi, DOMID_SELF,
+			       shareable ? PIRQ_SHAREABLE : 0);
+	if (ret < 0) {
+		__unbind_from_irq(info, info->irq);
+		goto out;
+	}
+
+	pirq_query_unmask(info);
+	/* We try to use the handler with the appropriate semantic for the
+	 * type of interrupt: if the interrupt is an edge triggered
+	 * interrupt we use handle_edge_irq.
+	 *
+	 * On the other hand if the interrupt is level triggered we use
+	 * handle_fasteoi_irq like the native code does for this kind of
+	 * interrupts.
+	 *
+	 * Depending on the Xen version, pirq_needs_eoi might return true
+	 * not only for level triggered interrupts but for edge triggered
+	 * interrupts too. In any case Xen always honors the eoi mechanism,
+	 * not injecting any more pirqs of the same kind if the first one
+	 * hasn't received an eoi yet. Therefore using the fasteoi handler
+	 * is the right choice either way.
+	 */
+	if (shareable)
+		irq_set_chip_and_handler_name(info->irq, &xen_pirq_chip,
+				handle_fasteoi_irq, name);
+	else
+		irq_set_chip_and_handler_name(info->irq, &xen_pirq_chip,
+				handle_edge_irq, name);
+
+	ret = info->irq;
+
+out:
+	mutex_unlock(&irq_mapping_update_lock);
+
+	return ret;
+}
+
+#ifdef CONFIG_PCI_MSI
+int xen_allocate_pirq_msi(struct pci_dev *dev, struct msi_desc *msidesc)
+{
+	int rc;
+	struct physdev_get_free_pirq op_get_free_pirq;
+
+	op_get_free_pirq.type = MAP_PIRQ_TYPE_MSI;
+	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_free_pirq, &op_get_free_pirq);
+
+	WARN_ONCE(rc == -ENOSYS,
+		  "hypervisor does not support the PHYSDEVOP_get_free_pirq interface\n");
+
+	return rc ? -1 : op_get_free_pirq.pirq;
+}
+
+int xen_bind_pirq_msi_to_irq(struct pci_dev *dev, struct msi_desc *msidesc,
+			     int pirq, int nvec, const char *name, domid_t domid)
+{
+	int i, irq, ret;
+	struct irq_info *info;
+
+	mutex_lock(&irq_mapping_update_lock);
+
+	irq = irq_alloc_descs(-1, 0, nvec, -1);
+	if (irq < 0)
+		goto out;
+
+	for (i = 0; i < nvec; i++) {
+		info = xen_irq_init(irq + i);
+		if (!info) {
+			ret = -ENOMEM;
+			goto error_irq;
+		}
+
+		irq_set_chip_and_handler_name(irq + i, &xen_pirq_chip, handle_edge_irq, name);
+
+		ret = xen_irq_info_pirq_setup(info, 0, pirq + i, 0, domid,
+					      i == 0 ? 0 : PIRQ_MSI_GROUP);
+		if (ret < 0)
+			goto error_irq;
+	}
+
+	ret = irq_set_msi_desc(irq, msidesc);
+	if (ret < 0)
+		goto error_irq;
+out:
+	mutex_unlock(&irq_mapping_update_lock);
+	return irq;
+
+error_irq:
+	while (nvec--) {
+		info = info_for_irq(irq + nvec);
+		__unbind_from_irq(info, irq + nvec);
+	}
+	mutex_unlock(&irq_mapping_update_lock);
+	return ret;
+}
+#endif
+
+int xen_destroy_irq(int irq)
+{
+	struct physdev_unmap_pirq unmap_irq;
+	struct irq_info *info = info_for_irq(irq);
+	int rc = -ENOENT;
+
+	mutex_lock(&irq_mapping_update_lock);
+
+	/*
+	 * If trying to remove a vector in a MSI group different
+	 * than the first one skip the PIRQ unmap unless this vector
+	 * is the first one in the group.
+	 */
+	if (xen_initial_domain() && !(info->u.pirq.flags & PIRQ_MSI_GROUP)) {
+		unmap_irq.pirq = info->u.pirq.pirq;
+		unmap_irq.domid = info->u.pirq.domid;
+		rc = HYPERVISOR_physdev_op(PHYSDEVOP_unmap_pirq, &unmap_irq);
+		/* If another domain quits without making the pci_disable_msix
+		 * call, the Xen hypervisor takes care of freeing the PIRQs
+		 * (free_domain_pirqs).
+		 */
+		if ((rc == -ESRCH && info->u.pirq.domid != DOMID_SELF))
+			pr_info("domain %d does not have %d anymore\n",
+				info->u.pirq.domid, info->u.pirq.pirq);
+		else if (rc) {
+			pr_warn("unmap irq failed %d\n", rc);
+			goto out;
+		}
+	}
+
+	xen_free_irq(info);
+
+out:
+	mutex_unlock(&irq_mapping_update_lock);
+	return rc;
+}
+
+int xen_pirq_from_irq(unsigned irq)
+{
+	struct irq_info *info = info_for_irq(irq);
+
+	return pirq_from_irq(info);
+}
+EXPORT_SYMBOL_GPL(xen_pirq_from_irq);
+
+static int bind_evtchn_to_irq_chip(evtchn_port_t evtchn, struct irq_chip *chip,
+				   struct xenbus_device *dev, bool shared)
+{
+	int ret = -ENOMEM;
+	struct irq_info *info;
+
+	if (evtchn >= xen_evtchn_max_channels())
+		return -ENOMEM;
+
+	mutex_lock(&irq_mapping_update_lock);
+
+	info = evtchn_to_info(evtchn);
+
+	if (!info) {
+		info = xen_allocate_irq_dynamic();
+		if (!info)
+			goto out;
+
+		irq_set_chip_and_handler_name(info->irq, chip,
+					      handle_edge_irq, "event");
+
+		ret = xen_irq_info_evtchn_setup(info, evtchn, dev);
+		if (ret < 0) {
+			__unbind_from_irq(info, info->irq);
+			goto out;
+		}
+		/*
+		 * New interdomain events are initially bound to vCPU0 This
+		 * is required to setup the event channel in the first
+		 * place and also important for UP guests because the
+		 * affinity setting is not invoked on them so nothing would
+		 * bind the channel.
+		 */
+		bind_evtchn_to_cpu(info, 0, false);
+	} else if (!WARN_ON(info->type != IRQT_EVTCHN)) {
+		if (shared && !WARN_ON(info->refcnt < 0))
+			info->refcnt++;
+	}
+
+	ret = info->irq;
+
+out:
+	mutex_unlock(&irq_mapping_update_lock);
+
+	return ret;
+}
+
+int bind_evtchn_to_irq(evtchn_port_t evtchn)
+{
+	return bind_evtchn_to_irq_chip(evtchn, &xen_dynamic_chip, NULL, false);
+}
+EXPORT_SYMBOL_GPL(bind_evtchn_to_irq);
+
+int bind_evtchn_to_irq_lateeoi(evtchn_port_t evtchn)
+{
+	return bind_evtchn_to_irq_chip(evtchn, &xen_lateeoi_chip, NULL, false);
+}
+EXPORT_SYMBOL_GPL(bind_evtchn_to_irq_lateeoi);
+
+static int bind_ipi_to_irq(unsigned int ipi, unsigned int cpu)
+{
+	struct evtchn_bind_ipi bind_ipi;
+	evtchn_port_t evtchn;
+	struct irq_info *info;
+	int ret;
+
+	mutex_lock(&irq_mapping_update_lock);
+
+	ret = per_cpu(ipi_to_irq, cpu)[ipi];
+
+	if (ret == -1) {
+		info = xen_allocate_irq_dynamic();
+		if (!info)
+			goto out;
+
+		irq_set_chip_and_handler_name(info->irq, &xen_percpu_chip,
+					      handle_percpu_irq, "ipi");
+
+		bind_ipi.vcpu = xen_vcpu_nr(cpu);
+		if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_ipi,
+						&bind_ipi) != 0)
+			BUG();
+		evtchn = bind_ipi.port;
+
+		ret = xen_irq_info_ipi_setup(info, cpu, evtchn, ipi);
+		if (ret < 0) {
+			__unbind_from_irq(info, info->irq);
+			goto out;
+		}
+		/*
+		 * Force the affinity mask to the target CPU so proc shows
+		 * the correct target.
+		 */
+		bind_evtchn_to_cpu(info, cpu, true);
+		ret = info->irq;
+	} else {
+		info = info_for_irq(ret);
+		WARN_ON(info == NULL || info->type != IRQT_IPI);
+	}
+
+ out:
+	mutex_unlock(&irq_mapping_update_lock);
+	return ret;
+}
+
+static int bind_interdomain_evtchn_to_irq_chip(struct xenbus_device *dev,
+					       evtchn_port_t remote_port,
+					       struct irq_chip *chip,
+					       bool shared)
+{
+	struct evtchn_bind_interdomain bind_interdomain;
+	int err;
+
+	bind_interdomain.remote_dom  = dev->otherend_id;
+	bind_interdomain.remote_port = remote_port;
+
+	err = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
+					  &bind_interdomain);
+
+	return err ? : bind_evtchn_to_irq_chip(bind_interdomain.local_port,
+					       chip, dev, shared);
+}
+
+int bind_interdomain_evtchn_to_irq_lateeoi(struct xenbus_device *dev,
+					   evtchn_port_t remote_port)
+{
+	return bind_interdomain_evtchn_to_irq_chip(dev, remote_port,
+						   &xen_lateeoi_chip, false);
+}
+EXPORT_SYMBOL_GPL(bind_interdomain_evtchn_to_irq_lateeoi);
+
+static int find_virq(unsigned int virq, unsigned int cpu, evtchn_port_t *evtchn,
+		     bool percpu)
+{
+	struct evtchn_status status;
+	evtchn_port_t port;
+	bool exists = false;
+
+	memset(&status, 0, sizeof(status));
+	for (port = 0; port < xen_evtchn_max_channels(); port++) {
+		int rc;
+
+		status.dom = DOMID_SELF;
+		status.port = port;
+		rc = HYPERVISOR_event_channel_op(EVTCHNOP_status, &status);
+		if (rc < 0)
+			continue;
+		if (status.status != EVTCHNSTAT_virq)
+			continue;
+		if (status.u.virq != virq)
+			continue;
+		if (status.vcpu == xen_vcpu_nr(cpu)) {
+			*evtchn = port;
+			return 0;
+		} else if (!percpu) {
+			exists = true;
+		}
+	}
+	return exists ? -EEXIST : -ENOENT;
+}
+
+/**
+ * xen_evtchn_nr_channels - number of usable event channel ports
+ *
+ * This may be less than the maximum supported by the current
+ * hypervisor ABI. Use xen_evtchn_max_channels() for the maximum
+ * supported.
+ */
+unsigned xen_evtchn_nr_channels(void)
+{
+        return evtchn_ops->nr_channels();
+}
+EXPORT_SYMBOL_GPL(xen_evtchn_nr_channels);
+
+int bind_virq_to_irq(unsigned int virq, unsigned int cpu, bool percpu)
+{
+	struct evtchn_bind_virq bind_virq;
+	evtchn_port_t evtchn = 0;
+	struct irq_info *info;
+	int ret;
+
+	mutex_lock(&irq_mapping_update_lock);
+
+	ret = per_cpu(virq_to_irq, cpu)[virq];
+
+	if (ret == -1) {
+		info = xen_allocate_irq_dynamic();
+		if (!info)
+			goto out;
+
+		if (percpu)
+			irq_set_chip_and_handler_name(info->irq, &xen_percpu_chip,
+						      handle_percpu_irq, "virq");
+		else
+			irq_set_chip_and_handler_name(info->irq, &xen_dynamic_chip,
+						      handle_edge_irq, "virq");
+
+		bind_virq.virq = virq;
+		bind_virq.vcpu = xen_vcpu_nr(cpu);
+		ret = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
+						&bind_virq);
+		if (ret == 0)
+			evtchn = bind_virq.port;
+		else {
+			if (ret == -EEXIST)
+				ret = find_virq(virq, cpu, &evtchn, percpu);
+			if (ret) {
+				__unbind_from_irq(info, info->irq);
+				goto out;
+			}
+		}
+
+		ret = xen_irq_info_virq_setup(info, cpu, evtchn, virq);
+		if (ret < 0) {
+			__unbind_from_irq(info, info->irq);
+			goto out;
+		}
+
+		/*
+		 * Force the affinity mask for percpu interrupts so proc
+		 * shows the correct target.
+		 */
+		bind_evtchn_to_cpu(info, cpu, percpu);
+		ret = info->irq;
+	} else {
+		info = info_for_irq(ret);
+		WARN_ON(info == NULL || info->type != IRQT_VIRQ);
+	}
+
+out:
+	mutex_unlock(&irq_mapping_update_lock);
+
+	return ret;
+}
+
+static void unbind_from_irq(unsigned int irq)
+{
+	struct irq_info *info;
+
+	mutex_lock(&irq_mapping_update_lock);
+	info = info_for_irq(irq);
+	__unbind_from_irq(info, irq);
+	mutex_unlock(&irq_mapping_update_lock);
+}
+
+static int bind_evtchn_to_irqhandler_chip(evtchn_port_t evtchn,
+					  irq_handler_t handler,
+					  unsigned long irqflags,
+					  const char *devname, void *dev_id,
+					  struct irq_chip *chip)
+{
+	int irq, retval;
+
+	irq = bind_evtchn_to_irq_chip(evtchn, chip, NULL,
+				      irqflags & IRQF_SHARED);
+	if (irq < 0)
+		return irq;
+	retval = request_irq(irq, handler, irqflags, devname, dev_id);
+	if (retval != 0) {
+		unbind_from_irq(irq);
+		return retval;
+	}
+
+	return irq;
+}
+
+int bind_evtchn_to_irqhandler(evtchn_port_t evtchn,
+			      irq_handler_t handler,
+			      unsigned long irqflags,
+			      const char *devname, void *dev_id)
+{
+	return bind_evtchn_to_irqhandler_chip(evtchn, handler, irqflags,
+					      devname, dev_id,
+					      &xen_dynamic_chip);
+}
+EXPORT_SYMBOL_GPL(bind_evtchn_to_irqhandler);
+
+int bind_evtchn_to_irqhandler_lateeoi(evtchn_port_t evtchn,
+				      irq_handler_t handler,
+				      unsigned long irqflags,
+				      const char *devname, void *dev_id)
+{
+	return bind_evtchn_to_irqhandler_chip(evtchn, handler, irqflags,
+					      devname, dev_id,
+					      &xen_lateeoi_chip);
+}
+EXPORT_SYMBOL_GPL(bind_evtchn_to_irqhandler_lateeoi);
+
+static int bind_interdomain_evtchn_to_irqhandler_chip(
+		struct xenbus_device *dev, evtchn_port_t remote_port,
+		irq_handler_t handler, unsigned long irqflags,
+		const char *devname, void *dev_id, struct irq_chip *chip)
+{
+	int irq, retval;
+
+	irq = bind_interdomain_evtchn_to_irq_chip(dev, remote_port, chip,
+						  irqflags & IRQF_SHARED);
+	if (irq < 0)
+		return irq;
+
+	retval = request_irq(irq, handler, irqflags, devname, dev_id);
+	if (retval != 0) {
+		unbind_from_irq(irq);
+		return retval;
+	}
+
+	return irq;
+}
+
+int bind_interdomain_evtchn_to_irqhandler_lateeoi(struct xenbus_device *dev,
+						  evtchn_port_t remote_port,
+						  irq_handler_t handler,
+						  unsigned long irqflags,
+						  const char *devname,
+						  void *dev_id)
+{
+	return bind_interdomain_evtchn_to_irqhandler_chip(dev,
+				remote_port, handler, irqflags, devname,
+				dev_id, &xen_lateeoi_chip);
+}
+EXPORT_SYMBOL_GPL(bind_interdomain_evtchn_to_irqhandler_lateeoi);
+
+int bind_virq_to_irqhandler(unsigned int virq, unsigned int cpu,
+			    irq_handler_t handler,
+			    unsigned long irqflags, const char *devname, void *dev_id)
+{
+	int irq, retval;
+
+	irq = bind_virq_to_irq(virq, cpu, irqflags & IRQF_PERCPU);
+	if (irq < 0)
+		return irq;
+	retval = request_irq(irq, handler, irqflags, devname, dev_id);
+	if (retval != 0) {
+		unbind_from_irq(irq);
+		return retval;
+	}
+
+	return irq;
+}
+EXPORT_SYMBOL_GPL(bind_virq_to_irqhandler);
+
+int bind_ipi_to_irqhandler(enum ipi_vector ipi,
+			   unsigned int cpu,
+			   irq_handler_t handler,
+			   unsigned long irqflags,
+			   const char *devname,
+			   void *dev_id)
+{
+	int irq, retval;
+
+	irq = bind_ipi_to_irq(ipi, cpu);
+	if (irq < 0)
+		return irq;
+
+	irqflags |= IRQF_NO_SUSPEND | IRQF_FORCE_RESUME | IRQF_EARLY_RESUME;
+	retval = request_irq(irq, handler, irqflags, devname, dev_id);
+	if (retval != 0) {
+		unbind_from_irq(irq);
+		return retval;
+	}
+
+	return irq;
+}
+
+void unbind_from_irqhandler(unsigned int irq, void *dev_id)
+{
+	struct irq_info *info = info_for_irq(irq);
+
+	if (WARN_ON(!info))
+		return;
+	free_irq(irq, dev_id);
+	unbind_from_irq(irq);
+}
+EXPORT_SYMBOL_GPL(unbind_from_irqhandler);
+
+/**
+ * xen_set_irq_priority() - set an event channel priority.
+ * @irq:irq bound to an event channel.
+ * @priority: priority between XEN_IRQ_PRIORITY_MAX and XEN_IRQ_PRIORITY_MIN.
+ */
+int xen_set_irq_priority(unsigned irq, unsigned priority)
+{
+	struct evtchn_set_priority set_priority;
+
+	set_priority.port = evtchn_from_irq(irq);
+	set_priority.priority = priority;
+
+	return HYPERVISOR_event_channel_op(EVTCHNOP_set_priority,
+					   &set_priority);
+}
+EXPORT_SYMBOL_GPL(xen_set_irq_priority);
+
+int evtchn_make_refcounted(evtchn_port_t evtchn, bool is_static)
+{
+	struct irq_info *info = evtchn_to_info(evtchn);
+
+	if (!info)
+		return -ENOENT;
+
+	WARN_ON(info->refcnt != -1);
+
+	info->refcnt = 1;
+	info->is_static = is_static;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(evtchn_make_refcounted);
+
+int evtchn_get(evtchn_port_t evtchn)
+{
+	struct irq_info *info;
+	int err = -ENOENT;
+
+	if (evtchn >= xen_evtchn_max_channels())
+		return -EINVAL;
+
+	mutex_lock(&irq_mapping_update_lock);
+
+	info = evtchn_to_info(evtchn);
+
+	if (!info)
+		goto done;
+
+	err = -EINVAL;
+	if (info->refcnt <= 0 || info->refcnt == SHRT_MAX)
+		goto done;
+
+	info->refcnt++;
+	err = 0;
+ done:
+	mutex_unlock(&irq_mapping_update_lock);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(evtchn_get);
+
+void evtchn_put(evtchn_port_t evtchn)
+{
+	struct irq_info *info = evtchn_to_info(evtchn);
+
+	if (WARN_ON(!info))
+		return;
+	unbind_from_irq(info->irq);
+}
+EXPORT_SYMBOL_GPL(evtchn_put);
+
+void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
+{
+	evtchn_port_t evtchn;
+
+#ifdef CONFIG_X86
+	if (unlikely(vector == XEN_NMI_VECTOR)) {
+		int rc =  HYPERVISOR_vcpu_op(VCPUOP_send_nmi, xen_vcpu_nr(cpu),
+					     NULL);
+		if (rc < 0)
+			printk(KERN_WARNING "Sending nmi to CPU%d failed (rc:%d)\n", cpu, rc);
+		return;
+	}
+#endif
+	evtchn = per_cpu(ipi_to_evtchn, cpu)[vector];
+	BUG_ON(evtchn == 0);
+	notify_remote_via_evtchn(evtchn);
+}
+
+struct evtchn_loop_ctrl {
+	ktime_t timeout;
+	unsigned count;
+	bool defer_eoi;
+};
+
+void handle_irq_for_port(evtchn_port_t port, struct evtchn_loop_ctrl *ctrl)
+{
+	struct irq_info *info = evtchn_to_info(port);
+	struct xenbus_device *dev;
+
+	if (!info)
+		return;
+
+	/*
+	 * Check for timeout every 256 events.
+	 * We are setting the timeout value only after the first 256
+	 * events in order to not hurt the common case of few loop
+	 * iterations. The 256 is basically an arbitrary value.
+	 *
+	 * In case we are hitting the timeout we need to defer all further
+	 * EOIs in order to ensure to leave the event handling loop rather
+	 * sooner than later.
+	 */
+	if (!ctrl->defer_eoi && !(++ctrl->count & 0xff)) {
+		ktime_t kt = ktime_get();
+
+		if (!ctrl->timeout) {
+			kt = ktime_add_ms(kt,
+					  jiffies_to_msecs(event_loop_timeout));
+			ctrl->timeout = kt;
+		} else if (kt > ctrl->timeout) {
+			ctrl->defer_eoi = true;
+		}
+	}
+
+	if (xchg_acquire(&info->is_active, 1))
+		return;
+
+	dev = (info->type == IRQT_EVTCHN) ? info->u.interdomain : NULL;
+	if (dev)
+		atomic_inc(&dev->events);
+
+	if (ctrl->defer_eoi) {
+		info->eoi_cpu = smp_processor_id();
+		info->irq_epoch = __this_cpu_read(irq_epoch);
+		info->eoi_time = get_jiffies_64() + event_eoi_delay;
+	}
+
+	generic_handle_irq(info->irq);
+}
+
+int xen_evtchn_do_upcall(void)
+{
+	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
+	int ret = vcpu_info->evtchn_upcall_pending ? IRQ_HANDLED : IRQ_NONE;
+	int cpu = smp_processor_id();
+	struct evtchn_loop_ctrl ctrl = { 0 };
+
+	/*
+	 * When closing an event channel the associated IRQ must not be freed
+	 * until all cpus have left the event handling loop. This is ensured
+	 * by taking the rcu_read_lock() while handling events, as freeing of
+	 * the IRQ is handled via queue_rcu_work() _after_ closing the event
+	 * channel.
+	 */
+	rcu_read_lock();
+
+	do {
+		vcpu_info->evtchn_upcall_pending = 0;
+
+		xen_evtchn_handle_events(cpu, &ctrl);
+
+		BUG_ON(!irqs_disabled());
+
+		virt_rmb(); /* Hypervisor can set upcall pending. */
+
+	} while (vcpu_info->evtchn_upcall_pending);
+
+	rcu_read_unlock();
+
+	/*
+	 * Increment irq_epoch only now to defer EOIs only for
+	 * xen_irq_lateeoi() invocations occurring from inside the loop
+	 * above.
+	 */
+	__this_cpu_inc(irq_epoch);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xen_evtchn_do_upcall);
+
+/* Rebind a new event channel to an existing irq. */
+void rebind_evtchn_irq(evtchn_port_t evtchn, int irq)
+{
+	struct irq_info *info = info_for_irq(irq);
+
+	if (WARN_ON(!info))
+		return;
+
+	/* Make sure the irq is masked, since the new event channel
+	   will also be masked. */
+	disable_irq(irq);
+
+	mutex_lock(&irq_mapping_update_lock);
+
+	/* After resume the irq<->evtchn mappings are all cleared out */
+	BUG_ON(evtchn_to_info(evtchn));
+	/* Expect irq to have been bound before,
+	   so there should be a proper type */
+	BUG_ON(info->type == IRQT_UNBOUND);
+
+	info->irq = irq;
+	(void)xen_irq_info_evtchn_setup(info, evtchn, NULL);
+
+	mutex_unlock(&irq_mapping_update_lock);
+
+	bind_evtchn_to_cpu(info, info->cpu, false);
+
+	/* Unmask the event channel. */
+	enable_irq(irq);
+}
+
+/* Rebind an evtchn so that it gets delivered to a specific cpu */
+static int xen_rebind_evtchn_to_cpu(struct irq_info *info, unsigned int tcpu)
+{
+	struct evtchn_bind_vcpu bind_vcpu;
+	evtchn_port_t evtchn = info ? info->evtchn : 0;
+
+	if (!VALID_EVTCHN(evtchn))
+		return -1;
+
+	if (!xen_support_evtchn_rebind())
+		return -1;
+
+	/* Send future instances of this interrupt to other vcpu. */
+	bind_vcpu.port = evtchn;
+	bind_vcpu.vcpu = xen_vcpu_nr(tcpu);
+
+	/*
+	 * Mask the event while changing the VCPU binding to prevent
+	 * it being delivered on an unexpected VCPU.
+	 */
+	do_mask(info, EVT_MASK_REASON_TEMPORARY);
+
+	/*
+	 * If this fails, it usually just indicates that we're dealing with a
+	 * virq or IPI channel, which don't actually need to be rebound. Ignore
+	 * it, but don't do the xenlinux-level rebind in that case.
+	 */
+	if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_vcpu, &bind_vcpu) >= 0) {
+		int old_cpu = info->cpu;
+
+		bind_evtchn_to_cpu(info, tcpu, false);
+
+		if (info->type == IRQT_VIRQ) {
+			int virq = info->u.virq;
+			int irq = per_cpu(virq_to_irq, old_cpu)[virq];
+
+			per_cpu(virq_to_irq, old_cpu)[virq] = -1;
+			per_cpu(virq_to_irq, tcpu)[virq] = irq;
+		}
+	}
+
+	do_unmask(info, EVT_MASK_REASON_TEMPORARY);
+
+	return 0;
+}
+
+/*
+ * Find the CPU within @dest mask which has the least number of channels
+ * assigned. This is not precise as the per cpu counts can be modified
+ * concurrently.
+ */
+static unsigned int select_target_cpu(const struct cpumask *dest)
+{
+	unsigned int cpu, best_cpu = UINT_MAX, minch = UINT_MAX;
+
+	for_each_cpu_and(cpu, dest, cpu_online_mask) {
+		unsigned int curch = atomic_read(&channels_on_cpu[cpu]);
+
+		if (curch < minch) {
+			minch = curch;
+			best_cpu = cpu;
+		}
+	}
+
+	/*
+	 * Catch the unlikely case that dest contains no online CPUs. Can't
+	 * recurse.
+	 */
+	if (best_cpu == UINT_MAX)
+		return select_target_cpu(cpu_online_mask);
+
+	return best_cpu;
+}
+
+static int set_affinity_irq(struct irq_data *data, const struct cpumask *dest,
+			    bool force)
+{
+	unsigned int tcpu = select_target_cpu(dest);
+	int ret;
+
+	ret = xen_rebind_evtchn_to_cpu(info_for_irq(data->irq), tcpu);
+	if (!ret)
+		irq_data_update_effective_affinity(data, cpumask_of(tcpu));
+
+	return ret;
+}
+
+static void enable_dynirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+	evtchn_port_t evtchn = info ? info->evtchn : 0;
+
+	if (VALID_EVTCHN(evtchn))
+		do_unmask(info, EVT_MASK_REASON_EXPLICIT);
+}
+
+static void do_ack_dynirq(struct irq_info *info)
+{
+	evtchn_port_t evtchn = info->evtchn;
+
+	if (VALID_EVTCHN(evtchn))
+		event_handler_exit(info);
+}
+
+static void ack_dynirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+
+	if (info)
+		do_ack_dynirq(info);
+}
+
+static void mask_ack_dynirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+
+	if (info) {
+		do_disable_dynirq(info);
+		do_ack_dynirq(info);
+	}
+}
+
+static void lateeoi_ack_dynirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+	evtchn_port_t evtchn = info ? info->evtchn : 0;
+
+	if (VALID_EVTCHN(evtchn)) {
+		do_mask(info, EVT_MASK_REASON_EOI_PENDING);
+		/*
+		 * Don't call event_handler_exit().
+		 * Need to keep is_active non-zero in order to ignore re-raised
+		 * events after cpu affinity changes while a lateeoi is pending.
+		 */
+		clear_evtchn(evtchn);
+	}
+}
+
+static void lateeoi_mask_ack_dynirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+	evtchn_port_t evtchn = info ? info->evtchn : 0;
+
+	if (VALID_EVTCHN(evtchn)) {
+		do_mask(info, EVT_MASK_REASON_EXPLICIT);
+		event_handler_exit(info);
+	}
+}
+
+static int retrigger_dynirq(struct irq_data *data)
+{
+	struct irq_info *info = info_for_irq(data->irq);
+	evtchn_port_t evtchn = info ? info->evtchn : 0;
+
+	if (!VALID_EVTCHN(evtchn))
+		return 0;
+
+	do_mask(info, EVT_MASK_REASON_TEMPORARY);
+	set_evtchn(evtchn);
+	do_unmask(info, EVT_MASK_REASON_TEMPORARY);
+
+	return 1;
+}
+
+static void restore_pirqs(void)
+{
+	int pirq, rc, irq, gsi;
+	struct physdev_map_pirq map_irq;
+	struct irq_info *info;
+
+	list_for_each_entry(info, &xen_irq_list_head, list) {
+		if (info->type != IRQT_PIRQ)
+			continue;
+
+		pirq = info->u.pirq.pirq;
+		gsi = info->u.pirq.gsi;
+		irq = info->irq;
+
+		/* save/restore of PT devices doesn't work, so at this point the
+		 * only devices present are GSI based emulated devices */
+		if (!gsi)
+			continue;
+
+		map_irq.domid = DOMID_SELF;
+		map_irq.type = MAP_PIRQ_TYPE_GSI;
+		map_irq.index = gsi;
+		map_irq.pirq = pirq;
+
+		rc = HYPERVISOR_physdev_op(PHYSDEVOP_map_pirq, &map_irq);
+		if (rc) {
+			pr_warn("xen map irq failed gsi=%d irq=%d pirq=%d rc=%d\n",
+				gsi, irq, pirq, rc);
+			xen_free_irq(info);
+			continue;
+		}
+
+		printk(KERN_DEBUG "xen: --> irq=%d, pirq=%d\n", irq, map_irq.pirq);
+
+		__startup_pirq(info);
+	}
+}
+
+static void restore_cpu_virqs(unsigned int cpu)
+{
+	struct evtchn_bind_virq bind_virq;
+	evtchn_port_t evtchn;
+	struct irq_info *info;
+	int virq, irq;
+
+	for (virq = 0; virq < NR_VIRQS; virq++) {
+		if ((irq = per_cpu(virq_to_irq, cpu)[virq]) == -1)
+			continue;
+		info = info_for_irq(irq);
+
+		BUG_ON(virq_from_irq(info) != virq);
+
+		/* Get a new binding from Xen. */
+		bind_virq.virq = virq;
+		bind_virq.vcpu = xen_vcpu_nr(cpu);
+		if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
+						&bind_virq) != 0)
+			BUG();
+		evtchn = bind_virq.port;
+
+		/* Record the new mapping. */
+		xen_irq_info_virq_setup(info, cpu, evtchn, virq);
+		/* The affinity mask is still valid */
+		bind_evtchn_to_cpu(info, cpu, false);
+	}
+}
+
+static void restore_cpu_ipis(unsigned int cpu)
+{
+	struct evtchn_bind_ipi bind_ipi;
+	evtchn_port_t evtchn;
+	struct irq_info *info;
+	int ipi, irq;
+
+	for (ipi = 0; ipi < XEN_NR_IPIS; ipi++) {
+		if ((irq = per_cpu(ipi_to_irq, cpu)[ipi]) == -1)
+			continue;
+		info = info_for_irq(irq);
+
+		BUG_ON(ipi_from_irq(info) != ipi);
+
+		/* Get a new binding from Xen. */
+		bind_ipi.vcpu = xen_vcpu_nr(cpu);
+		if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_ipi,
+						&bind_ipi) != 0)
+			BUG();
+		evtchn = bind_ipi.port;
+
+		/* Record the new mapping. */
+		xen_irq_info_ipi_setup(info, cpu, evtchn, ipi);
+		/* The affinity mask is still valid */
+		bind_evtchn_to_cpu(info, cpu, false);
+	}
+}
+
+/* Clear an irq's pending state, in preparation for polling on it */
+void xen_clear_irq_pending(int irq)
+{
+	struct irq_info *info = info_for_irq(irq);
+	evtchn_port_t evtchn = info ? info->evtchn : 0;
+
+	if (VALID_EVTCHN(evtchn))
+		event_handler_exit(info);
+}
+EXPORT_SYMBOL(xen_clear_irq_pending);
+
+bool xen_test_irq_pending(int irq)
+{
+	evtchn_port_t evtchn = evtchn_from_irq(irq);
+	bool ret = false;
+
+	if (VALID_EVTCHN(evtchn))
+		ret = test_evtchn(evtchn);
+
+	return ret;
+}
+
+/* Poll waiting for an irq to become pending with timeout.  In the usual case,
+ * the irq will be disabled so it won't deliver an interrupt. */
+void xen_poll_irq_timeout(int irq, u64 timeout)
+{
+	evtchn_port_t evtchn = evtchn_from_irq(irq);
+
+	if (VALID_EVTCHN(evtchn)) {
+		struct sched_poll poll;
+
+		poll.nr_ports = 1;
+		poll.timeout = timeout;
+		set_xen_guest_handle(poll.ports, &evtchn);
+
+		if (HYPERVISOR_sched_op(SCHEDOP_poll, &poll) != 0)
+			BUG();
+	}
+}
+EXPORT_SYMBOL(xen_poll_irq_timeout);
+/* Poll waiting for an irq to become pending.  In the usual case, the
+ * irq will be disabled so it won't deliver an interrupt. */
+void xen_poll_irq(int irq)
+{
+	xen_poll_irq_timeout(irq, 0 /* no timeout */);
+}
+
+/* Check whether the IRQ line is shared with other guests. */
+int xen_test_irq_shared(int irq)
+{
+	struct irq_info *info = info_for_irq(irq);
+	struct physdev_irq_status_query irq_status;
+
+	if (WARN_ON(!info))
+		return -ENOENT;
+
+	irq_status.irq = info->u.pirq.pirq;
+
+	if (HYPERVISOR_physdev_op(PHYSDEVOP_irq_status_query, &irq_status))
+		return 0;
+	return !(irq_status.flags & XENIRQSTAT_shared);
+}
+EXPORT_SYMBOL_GPL(xen_test_irq_shared);
+
+void xen_irq_resume(void)
+{
+	unsigned int cpu;
+	struct irq_info *info;
+
+	/* New event-channel space is not 'live' yet. */
+	xen_evtchn_resume();
+
+	/* No IRQ <-> event-channel mappings. */
+	list_for_each_entry(info, &xen_irq_list_head, list) {
+		/* Zap event-channel binding */
+		info->evtchn = 0;
+		/* Adjust accounting */
+		channels_on_cpu_dec(info);
+	}
+
+	clear_evtchn_to_irq_all();
+
+	for_each_possible_cpu(cpu) {
+		restore_cpu_virqs(cpu);
+		restore_cpu_ipis(cpu);
+	}
+
+	restore_pirqs();
+}
+
+static struct irq_chip xen_dynamic_chip __read_mostly = {
+	.name			= "xen-dyn",
+
+	.irq_disable		= disable_dynirq,
+	.irq_mask		= disable_dynirq,
+	.irq_unmask		= enable_dynirq,
+
+	.irq_ack		= ack_dynirq,
+	.irq_mask_ack		= mask_ack_dynirq,
+
+	.irq_set_affinity	= set_affinity_irq,
+	.irq_retrigger		= retrigger_dynirq,
+};
+
+static struct irq_chip xen_lateeoi_chip __read_mostly = {
+	/* The chip name needs to contain "xen-dyn" for irqbalance to work. */
+	.name			= "xen-dyn-lateeoi",
+
+	.irq_disable		= disable_dynirq,
+	.irq_mask		= disable_dynirq,
+	.irq_unmask		= enable_dynirq,
+
+	.irq_ack		= lateeoi_ack_dynirq,
+	.irq_mask_ack		= lateeoi_mask_ack_dynirq,
+
+	.irq_set_affinity	= set_affinity_irq,
+	.irq_retrigger		= retrigger_dynirq,
+};
+
+static struct irq_chip xen_pirq_chip __read_mostly = {
+	.name			= "xen-pirq",
+
+	.irq_startup		= startup_pirq,
+	.irq_shutdown		= shutdown_pirq,
+	.irq_enable		= enable_pirq,
+	.irq_disable		= disable_pirq,
+
+	.irq_mask		= disable_dynirq,
+	.irq_unmask		= enable_dynirq,
+
+	.irq_ack		= eoi_pirq,
+	.irq_eoi		= eoi_pirq,
+	.irq_mask_ack		= mask_ack_pirq,
+
+	.irq_set_affinity	= set_affinity_irq,
+
+	.irq_retrigger		= retrigger_dynirq,
+};
+
+static struct irq_chip xen_percpu_chip __read_mostly = {
+	.name			= "xen-percpu",
+
+	.irq_disable		= disable_dynirq,
+	.irq_mask		= disable_dynirq,
+	.irq_unmask		= enable_dynirq,
+
+	.irq_ack		= ack_dynirq,
+};
+
+#ifdef CONFIG_X86
+/* Vector callbacks are better than PCI interrupts to receive event
+ * channel notifications because we can receive vector callbacks on any
+ * vcpu and we don't need PCI support or APIC interactions. */
+void xen_setup_callback_vector(void)
+{
+	uint64_t callback_via;
+
+	if (xen_have_vector_callback) {
+		callback_via = HVM_CALLBACK_VECTOR(HYPERVISOR_CALLBACK_VECTOR);
+		if (xen_set_callback_via(callback_via)) {
+			pr_err("Request for Xen HVM callback vector failed\n");
+			xen_have_vector_callback = false;
+		}
+	}
+}
+
+/*
+ * Setup per-vCPU vector-type callbacks. If this setup is unavailable,
+ * fallback to the global vector-type callback.
+ */
+static __init void xen_init_setup_upcall_vector(void)
+{
+	if (!xen_have_vector_callback)
+		return;
+
+	if ((cpuid_eax(xen_cpuid_base() + 4) & XEN_HVM_CPUID_UPCALL_VECTOR) &&
+	    !xen_set_upcall_vector(0))
+		xen_percpu_upcall = true;
+	else if (xen_feature(XENFEAT_hvm_callback_vector))
+		xen_setup_callback_vector();
+	else
+		xen_have_vector_callback = false;
+}
+
+int xen_set_upcall_vector(unsigned int cpu)
+{
+	int rc;
+	xen_hvm_evtchn_upcall_vector_t op = {
+		.vector = HYPERVISOR_CALLBACK_VECTOR,
+		.vcpu = per_cpu(xen_vcpu_id, cpu),
+	};
+
+	rc = HYPERVISOR_hvm_op(HVMOP_set_evtchn_upcall_vector, &op);
+	if (rc)
+		return rc;
+
+	/* Trick toolstack to think we are enlightened. */
+	if (!cpu)
+		rc = xen_set_callback_via(1);
+
+	return rc;
+}
+
+static __init void xen_alloc_callback_vector(void)
+{
+	if (!xen_have_vector_callback)
+		return;
+
+	pr_info("Xen HVM callback vector for event delivery is enabled\n");
+	sysvec_install(HYPERVISOR_CALLBACK_VECTOR, sysvec_xen_hvm_callback);
+}
+#endif /* CONFIG_X86 */
+
+bool xen_fifo_events = true;
+module_param_named(fifo_events, xen_fifo_events, bool, 0);
+
+static int xen_evtchn_cpu_prepare(unsigned int cpu)
+{
+	int ret = 0;
+
+	xen_cpu_init_eoi(cpu);
+
+	if (evtchn_ops->percpu_init)
+		ret = evtchn_ops->percpu_init(cpu);
+
+	return ret;
+}
+
+static int xen_evtchn_cpu_dead(unsigned int cpu)
+{
+	int ret = 0;
+
+	if (evtchn_ops->percpu_deinit)
+		ret = evtchn_ops->percpu_deinit(cpu);
+
+	return ret;
+}
+
+void __init xen_init_IRQ(void)
+{
+	int ret = -EINVAL;
+	evtchn_port_t evtchn;
+
+	if (xen_fifo_events)
+		ret = xen_evtchn_fifo_init();
+	if (ret < 0) {
+		xen_evtchn_2l_init();
+		xen_fifo_events = false;
+	}
+
+	xen_cpu_init_eoi(smp_processor_id());
+
+	cpuhp_setup_state_nocalls(CPUHP_XEN_EVTCHN_PREPARE,
+				  "xen/evtchn:prepare",
+				  xen_evtchn_cpu_prepare, xen_evtchn_cpu_dead);
+
+	evtchn_to_irq = kzalloc_objs(*evtchn_to_irq,
+				     EVTCHN_ROW(xen_evtchn_max_channels()));
+	BUG_ON(!evtchn_to_irq);
+
+	/* No event channels are 'live' right now. */
+	for (evtchn = 0; evtchn < xen_evtchn_nr_channels(); evtchn++)
+		mask_evtchn(evtchn);
+
+	pirq_needs_eoi = pirq_needs_eoi_flag;
+
+#ifdef CONFIG_X86
+	if (xen_pv_domain()) {
+		if (xen_initial_domain())
+			pci_xen_initial_domain();
+	}
+	xen_init_setup_upcall_vector();
+	xen_alloc_callback_vector();
+
+
+	if (xen_hvm_domain()) {
+		native_init_IRQ();
+		/* pci_xen_hvm_init must be called after native_init_IRQ so that
+		 * __acpi_register_gsi can point at the right function */
+		pci_xen_hvm_init();
+	} else {
+		int rc;
+		struct physdev_pirq_eoi_gmfn eoi_gmfn;
+
+		pirq_eoi_map = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
+		eoi_gmfn.gmfn = virt_to_gfn(pirq_eoi_map);
+		rc = HYPERVISOR_physdev_op(PHYSDEVOP_pirq_eoi_gmfn_v2, &eoi_gmfn);
+		if (rc != 0) {
+			free_page((unsigned long) pirq_eoi_map);
+			pirq_eoi_map = NULL;
+		} else
+			pirq_needs_eoi = pirq_check_eoi_map;
+	}
+#endif
+}
diff --git a/drivers/xen/events/events_fifo.c b/drivers/xen/events/events_fifo.c
new file mode 100644
index 000000000..655775db7
--- /dev/null
+++ b/drivers/xen/events/events_fifo.c
@@ -0,0 +1,440 @@
+/*
+ * Xen event channels (FIFO-based ABI)
+ *
+ * Copyright (C) 2013 Citrix Systems R&D ltd.
+ *
+ * This source code is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * Or, when distributed separately from the Linux kernel or
+ * incorporated into other software packages, subject to the following
+ * license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/linkage.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/smp.h>
+#include <linux/percpu.h>
+#include <linux/cpu.h>
+
+#include <asm/barrier.h>
+#include <asm/sync_bitops.h>
+#include <asm/xen/hypercall.h>
+#include <asm/xen/hypervisor.h>
+
+#include <xen/xen.h>
+#include <xen/xen-ops.h>
+#include <xen/events.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/event_channel.h>
+#include <xen/page.h>
+
+#include "events_internal.h"
+
+#define EVENT_WORDS_PER_PAGE (XEN_PAGE_SIZE / sizeof(event_word_t))
+#define MAX_EVENT_ARRAY_PAGES (EVTCHN_FIFO_NR_CHANNELS / EVENT_WORDS_PER_PAGE)
+
+struct evtchn_fifo_queue {
+	uint32_t head[EVTCHN_FIFO_MAX_QUEUES];
+};
+
+static DEFINE_PER_CPU(struct evtchn_fifo_control_block *, cpu_control_block);
+static DEFINE_PER_CPU(struct evtchn_fifo_queue, cpu_queue);
+static event_word_t *event_array[MAX_EVENT_ARRAY_PAGES] __read_mostly;
+static unsigned event_array_pages __read_mostly;
+
+/*
+ * sync_set_bit() and friends must be unsigned long aligned.
+ */
+#if BITS_PER_LONG > 32
+
+#define BM(w) (unsigned long *)((unsigned long)w & ~0x7UL)
+#define EVTCHN_FIFO_BIT(b, w) \
+    (((unsigned long)w & 0x4UL) ? (EVTCHN_FIFO_ ##b + 32) : EVTCHN_FIFO_ ##b)
+
+#else
+
+#define BM(w) ((unsigned long *)(w))
+#define EVTCHN_FIFO_BIT(b, w) EVTCHN_FIFO_ ##b
+
+#endif
+
+static inline event_word_t *event_word_from_port(evtchn_port_t port)
+{
+	unsigned i = port / EVENT_WORDS_PER_PAGE;
+
+	return event_array[i] + port % EVENT_WORDS_PER_PAGE;
+}
+
+static unsigned evtchn_fifo_max_channels(void)
+{
+	return EVTCHN_FIFO_NR_CHANNELS;
+}
+
+static unsigned evtchn_fifo_nr_channels(void)
+{
+	return event_array_pages * EVENT_WORDS_PER_PAGE;
+}
+
+static int init_control_block(int cpu,
+                              struct evtchn_fifo_control_block *control_block)
+{
+	struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
+	struct evtchn_init_control init_control;
+	unsigned int i;
+
+	/* Reset the control block and the local HEADs. */
+	clear_page(control_block);
+	for (i = 0; i < EVTCHN_FIFO_MAX_QUEUES; i++)
+		q->head[i] = 0;
+
+	init_control.control_gfn = virt_to_gfn(control_block);
+	init_control.offset      = 0;
+	init_control.vcpu        = xen_vcpu_nr(cpu);
+
+	return HYPERVISOR_event_channel_op(EVTCHNOP_init_control, &init_control);
+}
+
+static void free_unused_array_pages(void)
+{
+	unsigned i;
+
+	for (i = event_array_pages; i < MAX_EVENT_ARRAY_PAGES; i++) {
+		if (!event_array[i])
+			break;
+		free_page((unsigned long)event_array[i]);
+		event_array[i] = NULL;
+	}
+}
+
+static void init_array_page(event_word_t *array_page)
+{
+	unsigned i;
+
+	for (i = 0; i < EVENT_WORDS_PER_PAGE; i++)
+		array_page[i] = 1 << EVTCHN_FIFO_MASKED;
+}
+
+static int evtchn_fifo_setup(evtchn_port_t port)
+{
+	unsigned new_array_pages;
+	int ret;
+
+	new_array_pages = port / EVENT_WORDS_PER_PAGE + 1;
+
+	if (new_array_pages > MAX_EVENT_ARRAY_PAGES)
+		return -EINVAL;
+
+	while (event_array_pages < new_array_pages) {
+		void *array_page;
+		struct evtchn_expand_array expand_array;
+
+		/* Might already have a page if we've resumed. */
+		array_page = event_array[event_array_pages];
+		if (!array_page) {
+			array_page = (void *)__get_free_page(GFP_KERNEL);
+			if (array_page == NULL) {
+				ret = -ENOMEM;
+				goto error;
+			}
+			event_array[event_array_pages] = array_page;
+		}
+
+		/* Mask all events in this page before adding it. */
+		init_array_page(array_page);
+
+		expand_array.array_gfn = virt_to_gfn(array_page);
+
+		ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array);
+		if (ret < 0)
+			goto error;
+
+		event_array_pages++;
+	}
+	return 0;
+
+  error:
+	if (event_array_pages == 0)
+		panic("xen: unable to expand event array with initial page (%d)\n", ret);
+	else
+		pr_err("unable to expand event array (%d)\n", ret);
+	free_unused_array_pages();
+	return ret;
+}
+
+static void evtchn_fifo_bind_to_cpu(evtchn_port_t evtchn, unsigned int cpu, 
+				    unsigned int old_cpu)
+{
+	/* no-op */
+}
+
+static void evtchn_fifo_clear_pending(evtchn_port_t port)
+{
+	event_word_t *word = event_word_from_port(port);
+	sync_clear_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
+}
+
+static void evtchn_fifo_set_pending(evtchn_port_t port)
+{
+	event_word_t *word = event_word_from_port(port);
+	sync_set_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
+}
+
+static bool evtchn_fifo_is_pending(evtchn_port_t port)
+{
+	event_word_t *word = event_word_from_port(port);
+	return sync_test_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
+}
+
+static void evtchn_fifo_mask(evtchn_port_t port)
+{
+	event_word_t *word = event_word_from_port(port);
+	sync_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
+}
+
+static bool evtchn_fifo_is_masked(evtchn_port_t port)
+{
+	event_word_t *word = event_word_from_port(port);
+	return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
+}
+/*
+ * Clear MASKED if not PENDING, spinning if BUSY is set.
+ * Return true if mask was cleared.
+ */
+static bool clear_masked_cond(volatile event_word_t *word)
+{
+	event_word_t new, old;
+
+	old = *word;
+
+	do {
+		if (!(old & (1 << EVTCHN_FIFO_MASKED)))
+			return true;
+
+		if (old & (1 << EVTCHN_FIFO_PENDING))
+			return false;
+
+		old = old & ~(1 << EVTCHN_FIFO_BUSY);
+		new = old & ~(1 << EVTCHN_FIFO_MASKED);
+	} while (!sync_try_cmpxchg(word, &old, new));
+
+	return true;
+}
+
+static void evtchn_fifo_unmask(evtchn_port_t port)
+{
+	event_word_t *word = event_word_from_port(port);
+
+	BUG_ON(!irqs_disabled());
+
+	if (!clear_masked_cond(word)) {
+		struct evtchn_unmask unmask = { .port = port };
+		(void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
+	}
+}
+
+static uint32_t clear_linked(volatile event_word_t *word)
+{
+	event_word_t new, old;
+
+	old = *word;
+
+	do {
+		new = (old & ~((1 << EVTCHN_FIFO_LINKED)
+			       | EVTCHN_FIFO_LINK_MASK));
+	} while (!sync_try_cmpxchg(word, &old, new));
+
+	return old & EVTCHN_FIFO_LINK_MASK;
+}
+
+static void consume_one_event(unsigned cpu, struct evtchn_loop_ctrl *ctrl,
+			      struct evtchn_fifo_control_block *control_block,
+			      unsigned priority, unsigned long *ready)
+{
+	struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
+	uint32_t head;
+	evtchn_port_t port;
+	event_word_t *word;
+
+	head = q->head[priority];
+
+	/*
+	 * Reached the tail last time?  Read the new HEAD from the
+	 * control block.
+	 */
+	if (head == 0) {
+		virt_rmb(); /* Ensure word is up-to-date before reading head. */
+		head = control_block->head[priority];
+	}
+
+	port = head;
+	word = event_word_from_port(port);
+	head = clear_linked(word);
+
+	/*
+	 * If the link is non-zero, there are more events in the
+	 * queue, otherwise the queue is empty.
+	 *
+	 * If the queue is empty, clear this priority from our local
+	 * copy of the ready word.
+	 */
+	if (head == 0)
+		clear_bit(priority, ready);
+
+	if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port)) {
+		if (unlikely(!ctrl))
+			pr_warn("Dropping pending event for port %u\n", port);
+		else
+			handle_irq_for_port(port, ctrl);
+	}
+
+	q->head[priority] = head;
+}
+
+static void __evtchn_fifo_handle_events(unsigned cpu,
+					struct evtchn_loop_ctrl *ctrl)
+{
+	struct evtchn_fifo_control_block *control_block;
+	unsigned long ready;
+	unsigned q;
+
+	control_block = per_cpu(cpu_control_block, cpu);
+
+	ready = xchg(&control_block->ready, 0);
+
+	while (ready) {
+		q = find_first_bit(&ready, EVTCHN_FIFO_MAX_QUEUES);
+		consume_one_event(cpu, ctrl, control_block, q, &ready);
+		ready |= xchg(&control_block->ready, 0);
+	}
+}
+
+static void evtchn_fifo_handle_events(unsigned cpu,
+				      struct evtchn_loop_ctrl *ctrl)
+{
+	__evtchn_fifo_handle_events(cpu, ctrl);
+}
+
+static void evtchn_fifo_resume(void)
+{
+	unsigned cpu;
+
+	for_each_possible_cpu(cpu) {
+		void *control_block = per_cpu(cpu_control_block, cpu);
+		int ret;
+
+		if (!control_block)
+			continue;
+
+		/*
+		 * If this CPU is offline, take the opportunity to
+		 * free the control block while it is not being
+		 * used.
+		 */
+		if (!cpu_online(cpu)) {
+			free_page((unsigned long)control_block);
+			per_cpu(cpu_control_block, cpu) = NULL;
+			continue;
+		}
+
+		ret = init_control_block(cpu, control_block);
+		BUG_ON(ret < 0);
+	}
+
+	/*
+	 * The event array starts out as empty again and is extended
+	 * as normal when events are bound.  The existing pages will
+	 * be reused.
+	 */
+	event_array_pages = 0;
+}
+
+static int evtchn_fifo_alloc_control_block(unsigned cpu)
+{
+	void *control_block = NULL;
+	int ret = -ENOMEM;
+
+	control_block = (void *)__get_free_page(GFP_KERNEL);
+	if (control_block == NULL)
+		goto error;
+
+	ret = init_control_block(cpu, control_block);
+	if (ret < 0)
+		goto error;
+
+	per_cpu(cpu_control_block, cpu) = control_block;
+
+	return 0;
+
+  error:
+	free_page((unsigned long)control_block);
+	return ret;
+}
+
+static int evtchn_fifo_percpu_init(unsigned int cpu)
+{
+	if (!per_cpu(cpu_control_block, cpu))
+		return evtchn_fifo_alloc_control_block(cpu);
+	return 0;
+}
+
+static int evtchn_fifo_percpu_deinit(unsigned int cpu)
+{
+	__evtchn_fifo_handle_events(cpu, NULL);
+	return 0;
+}
+
+static const struct evtchn_ops evtchn_ops_fifo = {
+	.max_channels      = evtchn_fifo_max_channels,
+	.nr_channels       = evtchn_fifo_nr_channels,
+	.setup             = evtchn_fifo_setup,
+	.bind_to_cpu       = evtchn_fifo_bind_to_cpu,
+	.clear_pending     = evtchn_fifo_clear_pending,
+	.set_pending       = evtchn_fifo_set_pending,
+	.is_pending        = evtchn_fifo_is_pending,
+	.mask              = evtchn_fifo_mask,
+	.unmask            = evtchn_fifo_unmask,
+	.handle_events     = evtchn_fifo_handle_events,
+	.resume            = evtchn_fifo_resume,
+	.percpu_init       = evtchn_fifo_percpu_init,
+	.percpu_deinit     = evtchn_fifo_percpu_deinit,
+};
+
+int __init xen_evtchn_fifo_init(void)
+{
+	int cpu = smp_processor_id();
+	int ret;
+
+	ret = evtchn_fifo_alloc_control_block(cpu);
+	if (ret < 0)
+		return ret;
+
+	pr_info("Using FIFO-based ABI\n");
+
+	evtchn_ops = &evtchn_ops_fifo;
+
+	return ret;
+}
diff --git a/drivers/xen/events/events_internal.h b/drivers/xen/events/events_internal.h
new file mode 100644
index 000000000..19ae31695
--- /dev/null
+++ b/drivers/xen/events/events_internal.h
@@ -0,0 +1,110 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Xen Event Channels (internal header)
+ *
+ * Copyright (C) 2013 Citrix Systems R&D Ltd.
+ */
+#ifndef __EVENTS_INTERNAL_H__
+#define __EVENTS_INTERNAL_H__
+
+struct evtchn_loop_ctrl;
+
+struct evtchn_ops {
+	unsigned (*max_channels)(void);
+	unsigned (*nr_channels)(void);
+
+	int (*setup)(evtchn_port_t port);
+	void (*remove)(evtchn_port_t port, unsigned int cpu);
+	void (*bind_to_cpu)(evtchn_port_t evtchn, unsigned int cpu,
+			    unsigned int old_cpu);
+
+	void (*clear_pending)(evtchn_port_t port);
+	void (*set_pending)(evtchn_port_t port);
+	bool (*is_pending)(evtchn_port_t port);
+	void (*mask)(evtchn_port_t port);
+	void (*unmask)(evtchn_port_t port);
+
+	void (*handle_events)(unsigned cpu, struct evtchn_loop_ctrl *ctrl);
+	void (*resume)(void);
+
+	int (*percpu_init)(unsigned int cpu);
+	int (*percpu_deinit)(unsigned int cpu);
+};
+
+extern const struct evtchn_ops *evtchn_ops;
+
+void handle_irq_for_port(evtchn_port_t port, struct evtchn_loop_ctrl *ctrl);
+
+unsigned int cpu_from_evtchn(evtchn_port_t evtchn);
+
+static inline unsigned xen_evtchn_max_channels(void)
+{
+	return evtchn_ops->max_channels();
+}
+
+/*
+ * Do any ABI specific setup for a bound event channel before it can
+ * be unmasked and used.
+ */
+static inline int xen_evtchn_port_setup(evtchn_port_t evtchn)
+{
+	if (evtchn_ops->setup)
+		return evtchn_ops->setup(evtchn);
+	return 0;
+}
+
+static inline void xen_evtchn_port_remove(evtchn_port_t evtchn,
+					  unsigned int cpu)
+{
+	if (evtchn_ops->remove)
+		evtchn_ops->remove(evtchn, cpu);
+}
+
+static inline void xen_evtchn_port_bind_to_cpu(evtchn_port_t evtchn,
+					       unsigned int cpu,
+					       unsigned int old_cpu)
+{
+	evtchn_ops->bind_to_cpu(evtchn, cpu, old_cpu);
+}
+
+static inline void clear_evtchn(evtchn_port_t port)
+{
+	evtchn_ops->clear_pending(port);
+}
+
+static inline void set_evtchn(evtchn_port_t port)
+{
+	evtchn_ops->set_pending(port);
+}
+
+static inline bool test_evtchn(evtchn_port_t port)
+{
+	return evtchn_ops->is_pending(port);
+}
+
+static inline void mask_evtchn(evtchn_port_t port)
+{
+	return evtchn_ops->mask(port);
+}
+
+static inline void unmask_evtchn(evtchn_port_t port)
+{
+	return evtchn_ops->unmask(port);
+}
+
+static inline void xen_evtchn_handle_events(unsigned cpu,
+					    struct evtchn_loop_ctrl *ctrl)
+{
+	return evtchn_ops->handle_events(cpu, ctrl);
+}
+
+static inline void xen_evtchn_resume(void)
+{
+	if (evtchn_ops->resume)
+		evtchn_ops->resume();
+}
+
+void xen_evtchn_2l_init(void);
+int xen_evtchn_fifo_init(void);
+
+#endif /* #ifndef __EVENTS_INTERNAL_H__ */
diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
new file mode 100644
index 000000000..b7665bf27
--- /dev/null
+++ b/drivers/xen/evtchn.c
@@ -0,0 +1,732 @@
+/******************************************************************************
+ * evtchn.c
+ *
+ * Driver for receiving and demuxing event-channel signals.
+ *
+ * Copyright (c) 2004-2005, K A Fraser
+ * Multi-process extensions Copyright (c) 2004, Steven Smith
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/major.h>
+#include <linux/proc_fs.h>
+#include <linux/stat.h>
+#include <linux/poll.h>
+#include <linux/irq.h>
+#include <linux/init.h>
+#include <linux/mutex.h>
+#include <linux/cpu.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+
+#include <xen/xen.h>
+#include <xen/events.h>
+#include <xen/evtchn.h>
+#include <xen/xen-ops.h>
+#include <asm/xen/hypervisor.h>
+
+struct per_user_data {
+	struct mutex bind_mutex; /* serialize bind/unbind operations */
+	struct rb_root evtchns;
+	unsigned int nr_evtchns;
+
+	/* Notification ring, accessed via /dev/xen/evtchn. */
+	unsigned int ring_size;
+	evtchn_port_t *ring;
+	unsigned int ring_cons, ring_prod, ring_overflow;
+	struct mutex ring_cons_mutex; /* protect against concurrent readers */
+	spinlock_t ring_prod_lock; /* product against concurrent interrupts */
+
+	/* Processes wait on this queue when ring is empty. */
+	wait_queue_head_t evtchn_wait;
+	struct fasync_struct *evtchn_async_queue;
+	const char *name;
+
+	domid_t restrict_domid;
+};
+
+#define UNRESTRICTED_DOMID ((domid_t)-1)
+
+struct user_evtchn {
+	struct rb_node node;
+	struct per_user_data *user;
+	evtchn_port_t port;
+	bool enabled;
+	bool unbinding;
+};
+
+static void evtchn_free_ring(evtchn_port_t *ring)
+{
+	kvfree(ring);
+}
+
+static unsigned int evtchn_ring_offset(struct per_user_data *u,
+				       unsigned int idx)
+{
+	return idx & (u->ring_size - 1);
+}
+
+static evtchn_port_t *evtchn_ring_entry(struct per_user_data *u,
+					unsigned int idx)
+{
+	return u->ring + evtchn_ring_offset(u, idx);
+}
+
+static int add_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
+{
+	struct rb_node **new = &(u->evtchns.rb_node), *parent = NULL;
+
+	u->nr_evtchns++;
+
+	while (*new) {
+		struct user_evtchn *this;
+
+		this = rb_entry(*new, struct user_evtchn, node);
+
+		parent = *new;
+		if (this->port < evtchn->port)
+			new = &((*new)->rb_left);
+		else if (this->port > evtchn->port)
+			new = &((*new)->rb_right);
+		else
+			return -EEXIST;
+	}
+
+	/* Add new node and rebalance tree. */
+	rb_link_node(&evtchn->node, parent, new);
+	rb_insert_color(&evtchn->node, &u->evtchns);
+
+	return 0;
+}
+
+static void del_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
+{
+	u->nr_evtchns--;
+	rb_erase(&evtchn->node, &u->evtchns);
+	kfree(evtchn);
+}
+
+static struct user_evtchn *find_evtchn(struct per_user_data *u,
+				       evtchn_port_t port)
+{
+	struct rb_node *node = u->evtchns.rb_node;
+
+	while (node) {
+		struct user_evtchn *evtchn;
+
+		evtchn = rb_entry(node, struct user_evtchn, node);
+
+		if (evtchn->port < port)
+			node = node->rb_left;
+		else if (evtchn->port > port)
+			node = node->rb_right;
+		else
+			return evtchn;
+	}
+	return NULL;
+}
+
+static irqreturn_t evtchn_interrupt(int irq, void *data)
+{
+	struct user_evtchn *evtchn = data;
+	struct per_user_data *u = evtchn->user;
+	unsigned int prod, cons;
+
+	/* Handler might be called when tearing down the IRQ. */
+	if (evtchn->unbinding)
+		return IRQ_HANDLED;
+
+	WARN(!evtchn->enabled,
+	     "Interrupt for port %u, but apparently not enabled; per-user %p\n",
+	     evtchn->port, u);
+
+	evtchn->enabled = false;
+
+	spin_lock(&u->ring_prod_lock);
+
+	prod = READ_ONCE(u->ring_prod);
+	cons = READ_ONCE(u->ring_cons);
+
+	if ((prod - cons) < u->ring_size) {
+		*evtchn_ring_entry(u, prod) = evtchn->port;
+		smp_wmb(); /* Ensure ring contents visible */
+		WRITE_ONCE(u->ring_prod, prod + 1);
+		if (cons == prod) {
+			wake_up_interruptible(&u->evtchn_wait);
+			kill_fasync(&u->evtchn_async_queue,
+				    SIGIO, POLL_IN);
+		}
+	} else
+		u->ring_overflow = 1;
+
+	spin_unlock(&u->ring_prod_lock);
+
+	return IRQ_HANDLED;
+}
+
+static ssize_t evtchn_read(struct file *file, char __user *buf,
+			   size_t count, loff_t *ppos)
+{
+	int rc;
+	unsigned int c, p, bytes1 = 0, bytes2 = 0;
+	struct per_user_data *u = file->private_data;
+
+	/* Whole number of ports. */
+	count &= ~(sizeof(evtchn_port_t)-1);
+
+	if (count == 0)
+		return 0;
+
+	if (count > PAGE_SIZE)
+		count = PAGE_SIZE;
+
+	for (;;) {
+		mutex_lock(&u->ring_cons_mutex);
+
+		rc = -EFBIG;
+		if (u->ring_overflow)
+			goto unlock_out;
+
+		c = READ_ONCE(u->ring_cons);
+		p = READ_ONCE(u->ring_prod);
+		if (c != p)
+			break;
+
+		mutex_unlock(&u->ring_cons_mutex);
+
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+
+		rc = wait_event_interruptible(u->evtchn_wait,
+			READ_ONCE(u->ring_cons) != READ_ONCE(u->ring_prod));
+		if (rc)
+			return rc;
+	}
+
+	/* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
+	if (((c ^ p) & u->ring_size) != 0) {
+		bytes1 = (u->ring_size - evtchn_ring_offset(u, c)) *
+			sizeof(evtchn_port_t);
+		bytes2 = evtchn_ring_offset(u, p) * sizeof(evtchn_port_t);
+	} else {
+		bytes1 = (p - c) * sizeof(evtchn_port_t);
+		bytes2 = 0;
+	}
+
+	/* Truncate chunks according to caller's maximum byte count. */
+	if (bytes1 > count) {
+		bytes1 = count;
+		bytes2 = 0;
+	} else if ((bytes1 + bytes2) > count) {
+		bytes2 = count - bytes1;
+	}
+
+	rc = -EFAULT;
+	smp_rmb(); /* Ensure that we see the port before we copy it. */
+	if (copy_to_user(buf, evtchn_ring_entry(u, c), bytes1) ||
+	    ((bytes2 != 0) &&
+	     copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
+		goto unlock_out;
+
+	WRITE_ONCE(u->ring_cons, c + (bytes1 + bytes2) / sizeof(evtchn_port_t));
+	rc = bytes1 + bytes2;
+
+ unlock_out:
+	mutex_unlock(&u->ring_cons_mutex);
+	return rc;
+}
+
+static ssize_t evtchn_write(struct file *file, const char __user *buf,
+			    size_t count, loff_t *ppos)
+{
+	int rc, i;
+	evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
+	struct per_user_data *u = file->private_data;
+
+	if (kbuf == NULL)
+		return -ENOMEM;
+
+	/* Whole number of ports. */
+	count &= ~(sizeof(evtchn_port_t)-1);
+
+	rc = 0;
+	if (count == 0)
+		goto out;
+
+	if (count > PAGE_SIZE)
+		count = PAGE_SIZE;
+
+	rc = -EFAULT;
+	if (copy_from_user(kbuf, buf, count) != 0)
+		goto out;
+
+	mutex_lock(&u->bind_mutex);
+
+	for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) {
+		evtchn_port_t port = kbuf[i];
+		struct user_evtchn *evtchn;
+
+		evtchn = find_evtchn(u, port);
+		if (evtchn && !evtchn->enabled) {
+			evtchn->enabled = true;
+			xen_irq_lateeoi(irq_from_evtchn(port), 0);
+		}
+	}
+
+	mutex_unlock(&u->bind_mutex);
+
+	rc = count;
+
+ out:
+	free_page((unsigned long)kbuf);
+	return rc;
+}
+
+static int evtchn_resize_ring(struct per_user_data *u)
+{
+	unsigned int new_size;
+	evtchn_port_t *new_ring, *old_ring;
+
+	/*
+	 * Ensure the ring is large enough to capture all possible
+	 * events. i.e., one free slot for each bound event.
+	 */
+	if (u->nr_evtchns <= u->ring_size)
+		return 0;
+
+	if (u->ring_size == 0)
+		new_size = 64;
+	else
+		new_size = 2 * u->ring_size;
+
+	new_ring = kvmalloc_objs(*new_ring, new_size);
+	if (!new_ring)
+		return -ENOMEM;
+
+	old_ring = u->ring;
+
+	/*
+	 * Access to the ring contents is serialized by either the
+	 * prod /or/ cons lock so take both when resizing.
+	 */
+	mutex_lock(&u->ring_cons_mutex);
+	spin_lock_irq(&u->ring_prod_lock);
+
+	/*
+	 * Copy the old ring contents to the new ring.
+	 *
+	 * To take care of wrapping, a full ring, and the new index
+	 * pointing into the second half, simply copy the old contents
+	 * twice.
+	 *
+	 * +---------+    +------------------+
+	 * |34567  12| -> |34567  1234567  12|
+	 * +-----p-c-+    +-------c------p---+
+	 */
+	memcpy(new_ring, old_ring, u->ring_size * sizeof(*u->ring));
+	memcpy(new_ring + u->ring_size, old_ring,
+	       u->ring_size * sizeof(*u->ring));
+
+	u->ring = new_ring;
+	u->ring_size = new_size;
+
+	spin_unlock_irq(&u->ring_prod_lock);
+	mutex_unlock(&u->ring_cons_mutex);
+
+	evtchn_free_ring(old_ring);
+
+	return 0;
+}
+
+static int evtchn_bind_to_user(struct per_user_data *u, evtchn_port_t port,
+			       bool is_static)
+{
+	struct user_evtchn *evtchn;
+	int rc = 0;
+
+	/*
+	 * Ports are never reused, so every caller should pass in a
+	 * unique port.
+	 *
+	 * (Locking not necessary because we haven't registered the
+	 * interrupt handler yet, and our caller has already
+	 * serialized bind operations.)
+	 */
+
+	evtchn = kzalloc_obj(*evtchn);
+	if (!evtchn)
+		return -ENOMEM;
+
+	evtchn->user = u;
+	evtchn->port = port;
+	evtchn->enabled = true; /* start enabled */
+
+	rc = add_evtchn(u, evtchn);
+	if (rc < 0)
+		goto err;
+
+	rc = evtchn_resize_ring(u);
+	if (rc < 0)
+		goto err;
+
+	rc = bind_evtchn_to_irqhandler_lateeoi(port, evtchn_interrupt, IRQF_SHARED,
+					       u->name, evtchn);
+	if (rc < 0)
+		goto err;
+
+	rc = evtchn_make_refcounted(port, is_static);
+	return rc;
+
+err:
+	/* bind failed, should close the port now */
+	if (!is_static)
+		xen_evtchn_close(port);
+
+	del_evtchn(u, evtchn);
+	return rc;
+}
+
+static void evtchn_unbind_from_user(struct per_user_data *u,
+				    struct user_evtchn *evtchn)
+{
+	int irq = irq_from_evtchn(evtchn->port);
+
+	BUG_ON(irq < 0);
+
+	evtchn->unbinding = true;
+	unbind_from_irqhandler(irq, evtchn);
+
+	del_evtchn(u, evtchn);
+}
+
+static long evtchn_ioctl(struct file *file,
+			 unsigned int cmd, unsigned long arg)
+{
+	int rc;
+	struct per_user_data *u = file->private_data;
+	void __user *uarg = (void __user *) arg;
+
+	/* Prevent bind from racing with unbind */
+	mutex_lock(&u->bind_mutex);
+
+	switch (cmd) {
+	case IOCTL_EVTCHN_BIND_VIRQ: {
+		struct ioctl_evtchn_bind_virq bind;
+		struct evtchn_bind_virq bind_virq;
+
+		rc = -EACCES;
+		if (u->restrict_domid != UNRESTRICTED_DOMID)
+			break;
+
+		rc = -EFAULT;
+		if (copy_from_user(&bind, uarg, sizeof(bind)))
+			break;
+
+		bind_virq.virq = bind.virq;
+		bind_virq.vcpu = xen_vcpu_nr(0);
+		rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
+						 &bind_virq);
+		if (rc != 0)
+			break;
+
+		rc = evtchn_bind_to_user(u, bind_virq.port, false);
+		if (rc == 0)
+			rc = bind_virq.port;
+		break;
+	}
+
+	case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
+		struct ioctl_evtchn_bind_interdomain bind;
+		struct evtchn_bind_interdomain bind_interdomain;
+
+		rc = -EFAULT;
+		if (copy_from_user(&bind, uarg, sizeof(bind)))
+			break;
+
+		rc = -EACCES;
+		if (u->restrict_domid != UNRESTRICTED_DOMID &&
+		    u->restrict_domid != bind.remote_domain)
+			break;
+
+		bind_interdomain.remote_dom  = bind.remote_domain;
+		bind_interdomain.remote_port = bind.remote_port;
+		rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
+						 &bind_interdomain);
+		if (rc != 0)
+			break;
+
+		rc = evtchn_bind_to_user(u, bind_interdomain.local_port, false);
+		if (rc == 0)
+			rc = bind_interdomain.local_port;
+		break;
+	}
+
+	case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
+		struct ioctl_evtchn_bind_unbound_port bind;
+		struct evtchn_alloc_unbound alloc_unbound;
+
+		rc = -EACCES;
+		if (u->restrict_domid != UNRESTRICTED_DOMID)
+			break;
+
+		rc = -EFAULT;
+		if (copy_from_user(&bind, uarg, sizeof(bind)))
+			break;
+
+		alloc_unbound.dom        = DOMID_SELF;
+		alloc_unbound.remote_dom = bind.remote_domain;
+		rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
+						 &alloc_unbound);
+		if (rc != 0)
+			break;
+
+		rc = evtchn_bind_to_user(u, alloc_unbound.port, false);
+		if (rc == 0)
+			rc = alloc_unbound.port;
+		break;
+	}
+
+	case IOCTL_EVTCHN_UNBIND: {
+		struct ioctl_evtchn_unbind unbind;
+		struct user_evtchn *evtchn;
+
+		rc = -EFAULT;
+		if (copy_from_user(&unbind, uarg, sizeof(unbind)))
+			break;
+
+		rc = -EINVAL;
+		if (unbind.port >= xen_evtchn_nr_channels())
+			break;
+
+		rc = -ENOTCONN;
+		evtchn = find_evtchn(u, unbind.port);
+		if (!evtchn)
+			break;
+
+		disable_irq(irq_from_evtchn(unbind.port));
+		evtchn_unbind_from_user(u, evtchn);
+		rc = 0;
+		break;
+	}
+
+	case IOCTL_EVTCHN_BIND_STATIC: {
+		struct ioctl_evtchn_bind bind;
+		struct user_evtchn *evtchn;
+
+		rc = -EFAULT;
+		if (copy_from_user(&bind, uarg, sizeof(bind)))
+			break;
+
+		rc = -EISCONN;
+		evtchn = find_evtchn(u, bind.port);
+		if (evtchn)
+			break;
+
+		rc = evtchn_bind_to_user(u, bind.port, true);
+		break;
+	}
+
+	case IOCTL_EVTCHN_NOTIFY: {
+		struct ioctl_evtchn_notify notify;
+		struct user_evtchn *evtchn;
+
+		rc = -EFAULT;
+		if (copy_from_user(&notify, uarg, sizeof(notify)))
+			break;
+
+		rc = -ENOTCONN;
+		evtchn = find_evtchn(u, notify.port);
+		if (evtchn) {
+			notify_remote_via_evtchn(notify.port);
+			rc = 0;
+		}
+		break;
+	}
+
+	case IOCTL_EVTCHN_RESET: {
+		/* Initialise the ring to empty. Clear errors. */
+		mutex_lock(&u->ring_cons_mutex);
+		spin_lock_irq(&u->ring_prod_lock);
+		WRITE_ONCE(u->ring_cons, 0);
+		WRITE_ONCE(u->ring_prod, 0);
+		u->ring_overflow = 0;
+		spin_unlock_irq(&u->ring_prod_lock);
+		mutex_unlock(&u->ring_cons_mutex);
+		rc = 0;
+		break;
+	}
+
+	case IOCTL_EVTCHN_RESTRICT_DOMID: {
+		struct ioctl_evtchn_restrict_domid ierd;
+
+		rc = -EACCES;
+		if (u->restrict_domid != UNRESTRICTED_DOMID)
+			break;
+
+		rc = -EFAULT;
+		if (copy_from_user(&ierd, uarg, sizeof(ierd)))
+		    break;
+
+		rc = -EINVAL;
+		if (ierd.domid == 0 || ierd.domid >= DOMID_FIRST_RESERVED)
+			break;
+
+		u->restrict_domid = ierd.domid;
+		rc = 0;
+
+		break;
+	}
+
+	default:
+		rc = -ENOSYS;
+		break;
+	}
+	mutex_unlock(&u->bind_mutex);
+
+	return rc;
+}
+
+static __poll_t evtchn_poll(struct file *file, poll_table *wait)
+{
+	__poll_t mask = EPOLLOUT | EPOLLWRNORM;
+	struct per_user_data *u = file->private_data;
+
+	poll_wait(file, &u->evtchn_wait, wait);
+	if (READ_ONCE(u->ring_cons) != READ_ONCE(u->ring_prod))
+		mask |= EPOLLIN | EPOLLRDNORM;
+	if (u->ring_overflow)
+		mask = EPOLLERR;
+	return mask;
+}
+
+static int evtchn_fasync(int fd, struct file *filp, int on)
+{
+	struct per_user_data *u = filp->private_data;
+	return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
+}
+
+static int evtchn_open(struct inode *inode, struct file *filp)
+{
+	struct per_user_data *u;
+
+	u = kzalloc_obj(*u);
+	if (u == NULL)
+		return -ENOMEM;
+
+	u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
+	if (u->name == NULL) {
+		kfree(u);
+		return -ENOMEM;
+	}
+
+	init_waitqueue_head(&u->evtchn_wait);
+
+	mutex_init(&u->bind_mutex);
+	mutex_init(&u->ring_cons_mutex);
+	spin_lock_init(&u->ring_prod_lock);
+
+	u->restrict_domid = UNRESTRICTED_DOMID;
+
+	filp->private_data = u;
+
+	return stream_open(inode, filp);
+}
+
+static int evtchn_release(struct inode *inode, struct file *filp)
+{
+	struct per_user_data *u = filp->private_data;
+	struct rb_node *node;
+
+	while ((node = u->evtchns.rb_node)) {
+		struct user_evtchn *evtchn;
+
+		evtchn = rb_entry(node, struct user_evtchn, node);
+		disable_irq(irq_from_evtchn(evtchn->port));
+		evtchn_unbind_from_user(u, evtchn);
+	}
+
+	evtchn_free_ring(u->ring);
+	kfree(u->name);
+	kfree(u);
+
+	return 0;
+}
+
+static const struct file_operations evtchn_fops = {
+	.owner   = THIS_MODULE,
+	.read    = evtchn_read,
+	.write   = evtchn_write,
+	.unlocked_ioctl = evtchn_ioctl,
+	.poll    = evtchn_poll,
+	.fasync  = evtchn_fasync,
+	.open    = evtchn_open,
+	.release = evtchn_release,
+};
+
+static struct miscdevice evtchn_miscdev = {
+	.minor        = MISC_DYNAMIC_MINOR,
+	.name         = "xen/evtchn",
+	.fops         = &evtchn_fops,
+};
+static int __init evtchn_init(void)
+{
+	int err;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	/* Create '/dev/xen/evtchn'. */
+	err = misc_register(&evtchn_miscdev);
+	if (err != 0) {
+		pr_err("Could not register /dev/xen/evtchn\n");
+		return err;
+	}
+
+	pr_info("Event-channel device installed\n");
+
+	return 0;
+}
+
+static void __exit evtchn_cleanup(void)
+{
+	misc_deregister(&evtchn_miscdev);
+}
+
+module_init(evtchn_init);
+module_exit(evtchn_cleanup);
+
+MODULE_DESCRIPTION("Xen /dev/xen/evtchn device driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/xen/features.c b/drivers/xen/features.c
new file mode 100644
index 000000000..87f1828d4
--- /dev/null
+++ b/drivers/xen/features.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/******************************************************************************
+ * features.c
+ *
+ * Xen feature flags.
+ *
+ * Copyright (c) 2006, Ian Campbell, XenSource Inc.
+ */
+#include <linux/types.h>
+#include <linux/cache.h>
+#include <linux/export.h>
+#include <linux/printk.h>
+
+#include <asm/xen/hypercall.h>
+
+#include <xen/xen.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/version.h>
+#include <xen/features.h>
+
+/*
+ * Linux kernel expects at least Xen 4.0.
+ *
+ * Assume some features to be available for that reason (depending on guest
+ * mode, of course).
+ */
+#define chk_required_feature(f) {					\
+		if (!xen_feature(f))					\
+			panic("Xen: feature %s not available!\n", #f);	\
+	}
+
+u8 xen_features[XENFEAT_NR_SUBMAPS * 32] __read_mostly;
+EXPORT_SYMBOL_GPL(xen_features);
+
+void xen_setup_features(void)
+{
+	struct xen_feature_info fi;
+	int i, j;
+
+	for (i = 0; i < XENFEAT_NR_SUBMAPS; i++) {
+		fi.submap_idx = i;
+		if (HYPERVISOR_xen_version(XENVER_get_features, &fi) < 0)
+			break;
+		for (j = 0; j < 32; j++)
+			xen_features[i * 32 + j] = !!(fi.submap & 1U << j);
+	}
+
+	if (xen_pv_domain()) {
+		chk_required_feature(XENFEAT_mmu_pt_update_preserve_ad);
+		chk_required_feature(XENFEAT_gnttab_map_avail_bits);
+	}
+}
diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
new file mode 100644
index 000000000..3218686be
--- /dev/null
+++ b/drivers/xen/gntalloc.c
@@ -0,0 +1,607 @@
+/******************************************************************************
+ * gntalloc.c
+ *
+ * Device for creating grant references (in user-space) that may be shared
+ * with other domains.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/*
+ * This driver exists to allow userspace programs in Linux to allocate kernel
+ * memory that will later be shared with another domain.  Without this device,
+ * Linux userspace programs cannot create grant references.
+ *
+ * How this stuff works:
+ *   X -> granting a page to Y
+ *   Y -> mapping the grant from X
+ *
+ *   1. X uses the gntalloc device to allocate a page of kernel memory, P.
+ *   2. X creates an entry in the grant table that says domid(Y) can access P.
+ *      This is done without a hypercall unless the grant table needs expansion.
+ *   3. X gives the grant reference identifier, GREF, to Y.
+ *   4. Y maps the page, either directly into kernel memory for use in a backend
+ *      driver, or via a the gntdev device to map into the address space of an
+ *      application running in Y. This is the first point at which Xen does any
+ *      tracking of the page.
+ *   5. A program in X mmap()s a segment of the gntalloc device that corresponds
+ *      to the shared page, and can now communicate with Y over the shared page.
+ *
+ *
+ * NOTE TO USERSPACE LIBRARIES:
+ *   The grant allocation and mmap()ing are, naturally, two separate operations.
+ *   You set up the sharing by calling the create ioctl() and then the mmap().
+ *   Teardown requires munmap() and either close() or ioctl().
+ *
+ * WARNING: Since Xen does not allow a guest to forcibly end the use of a grant
+ * reference, this device can be used to consume kernel memory by leaving grant
+ * references mapped by another domain when an application exits. Therefore,
+ * there is a global limit on the number of pages that can be allocated. When
+ * all references to the page are unmapped, it will be freed during the next
+ * grant operation.
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/atomic.h>
+#include <linux/module.h>
+#include <linux/miscdevice.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/device.h>
+#include <linux/mm.h>
+#include <linux/uaccess.h>
+#include <linux/types.h>
+#include <linux/list.h>
+#include <linux/highmem.h>
+
+#include <xen/xen.h>
+#include <xen/page.h>
+#include <xen/grant_table.h>
+#include <xen/gntalloc.h>
+#include <xen/events.h>
+
+static unsigned int limit = 1024;
+module_param(limit, uint, 0644);
+MODULE_PARM_DESC(limit, "Maximum number of grants that may be allocated by "
+		"the gntalloc device");
+
+static LIST_HEAD(gref_list);
+static DEFINE_MUTEX(gref_mutex);
+static unsigned int gref_size;
+
+struct notify_info {
+	uint16_t pgoff:12;    /* Bits 0-11: Offset of the byte to clear */
+	uint16_t flags:2;     /* Bits 12-13: Unmap notification flags */
+	int event;            /* Port (event channel) to notify */
+};
+
+/* Metadata on a grant reference. */
+struct gntalloc_gref {
+	struct list_head next_gref;  /* list entry gref_list */
+	struct list_head next_file;  /* list entry file->list, if open */
+	struct page *page;	     /* The shared page */
+	uint64_t file_index;         /* File offset for mmap() */
+	unsigned int users;          /* Use count - when zero, waiting on Xen */
+	grant_ref_t gref_id;         /* The grant reference number */
+	struct notify_info notify;   /* Unmap notification */
+};
+
+struct gntalloc_file_private_data {
+	struct list_head list;
+	uint64_t index;
+};
+
+struct gntalloc_vma_private_data {
+	struct gntalloc_gref *gref;
+	int users;
+	int count;
+};
+
+static void __del_gref(struct gntalloc_gref *gref);
+
+static void do_cleanup(void)
+{
+	struct gntalloc_gref *gref, *n;
+	list_for_each_entry_safe(gref, n, &gref_list, next_gref) {
+		if (!gref->users)
+			__del_gref(gref);
+	}
+}
+
+static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
+	uint32_t *gref_ids, struct gntalloc_file_private_data *priv)
+{
+	int i, rc, readonly;
+	LIST_HEAD(queue_gref);
+	LIST_HEAD(queue_file);
+	struct gntalloc_gref *gref, *next;
+
+	readonly = !(op->flags & GNTALLOC_FLAG_WRITABLE);
+	for (i = 0; i < op->count; i++) {
+		gref = kzalloc_obj(*gref);
+		if (!gref) {
+			rc = -ENOMEM;
+			goto undo;
+		}
+		list_add_tail(&gref->next_gref, &queue_gref);
+		list_add_tail(&gref->next_file, &queue_file);
+		gref->users = 1;
+		gref->file_index = op->index + i * PAGE_SIZE;
+		gref->page = alloc_page(GFP_KERNEL|__GFP_ZERO);
+		if (!gref->page) {
+			rc = -ENOMEM;
+			goto undo;
+		}
+
+		/* Grant foreign access to the page. */
+		rc = gnttab_grant_foreign_access(op->domid,
+						 xen_page_to_gfn(gref->page),
+						 readonly);
+		if (rc < 0)
+			goto undo;
+		gref_ids[i] = gref->gref_id = rc;
+	}
+
+	/* Add to gref lists. */
+	mutex_lock(&gref_mutex);
+	list_splice_tail(&queue_gref, &gref_list);
+	list_splice_tail(&queue_file, &priv->list);
+	mutex_unlock(&gref_mutex);
+
+	return 0;
+
+undo:
+	mutex_lock(&gref_mutex);
+	gref_size -= (op->count - i);
+
+	list_for_each_entry_safe(gref, next, &queue_file, next_file) {
+		list_del(&gref->next_file);
+		__del_gref(gref);
+	}
+
+	mutex_unlock(&gref_mutex);
+	return rc;
+}
+
+static void __del_gref(struct gntalloc_gref *gref)
+{
+	if (gref->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
+		uint8_t *tmp = kmap_local_page(gref->page);
+		tmp[gref->notify.pgoff] = 0;
+		kunmap_local(tmp);
+	}
+	if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
+		notify_remote_via_evtchn(gref->notify.event);
+		evtchn_put(gref->notify.event);
+	}
+
+	gref->notify.flags = 0;
+
+	if (gref->gref_id) {
+		if (gref->page)
+			gnttab_end_foreign_access(gref->gref_id, gref->page);
+		else
+			gnttab_free_grant_reference(gref->gref_id);
+	}
+
+	gref_size--;
+	list_del(&gref->next_gref);
+
+	kfree(gref);
+}
+
+/* finds contiguous grant references in a file, returns the first */
+static struct gntalloc_gref *find_grefs(struct gntalloc_file_private_data *priv,
+		uint64_t index, uint32_t count)
+{
+	struct gntalloc_gref *rv = NULL, *gref;
+	list_for_each_entry(gref, &priv->list, next_file) {
+		if (gref->file_index == index && !rv)
+			rv = gref;
+		if (rv) {
+			if (gref->file_index != index)
+				return NULL;
+			index += PAGE_SIZE;
+			count--;
+			if (count == 0)
+				return rv;
+		}
+	}
+	return NULL;
+}
+
+/*
+ * -------------------------------------
+ *  File operations.
+ * -------------------------------------
+ */
+static int gntalloc_open(struct inode *inode, struct file *filp)
+{
+	struct gntalloc_file_private_data *priv;
+
+	priv = kzalloc_obj(*priv);
+	if (!priv)
+		goto out_nomem;
+	INIT_LIST_HEAD(&priv->list);
+
+	filp->private_data = priv;
+
+	pr_debug("%s: priv %p\n", __func__, priv);
+
+	return 0;
+
+out_nomem:
+	return -ENOMEM;
+}
+
+static int gntalloc_release(struct inode *inode, struct file *filp)
+{
+	struct gntalloc_file_private_data *priv = filp->private_data;
+	struct gntalloc_gref *gref;
+
+	pr_debug("%s: priv %p\n", __func__, priv);
+
+	mutex_lock(&gref_mutex);
+	while (!list_empty(&priv->list)) {
+		gref = list_entry(priv->list.next,
+			struct gntalloc_gref, next_file);
+		list_del(&gref->next_file);
+		gref->users--;
+		if (gref->users == 0)
+			__del_gref(gref);
+	}
+	kfree(priv);
+	mutex_unlock(&gref_mutex);
+
+	return 0;
+}
+
+static long gntalloc_ioctl_alloc(struct gntalloc_file_private_data *priv,
+		struct ioctl_gntalloc_alloc_gref __user *arg)
+{
+	int rc = 0;
+	struct ioctl_gntalloc_alloc_gref op;
+	uint32_t *gref_ids;
+	unsigned int limit_snapshot;
+
+	pr_debug("%s: priv %p\n", __func__, priv);
+
+	if (copy_from_user(&op, arg, sizeof(op))) {
+		rc = -EFAULT;
+		goto out;
+	}
+
+	limit_snapshot = READ_ONCE(limit);
+	if (op.count > limit_snapshot) {
+		rc = -ENOSPC;
+		goto out;
+	}
+
+	gref_ids = kcalloc(op.count, sizeof(gref_ids[0]), GFP_KERNEL);
+	if (!gref_ids) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	mutex_lock(&gref_mutex);
+	/* Clean up pages that were at zero (local) users but were still mapped
+	 * by remote domains. Since those pages count towards the limit that we
+	 * are about to enforce, removing them here is a good idea.
+	 */
+	do_cleanup();
+	limit_snapshot = READ_ONCE(limit);
+	if (gref_size > limit_snapshot ||
+	    op.count > limit_snapshot - gref_size) {
+		mutex_unlock(&gref_mutex);
+		rc = -ENOSPC;
+		goto out_free;
+	}
+	gref_size += op.count;
+	op.index = priv->index;
+	priv->index += (uint64_t)op.count * PAGE_SIZE;
+	mutex_unlock(&gref_mutex);
+
+	rc = add_grefs(&op, gref_ids, priv);
+	if (rc < 0)
+		goto out_free;
+
+	/* Once we finish add_grefs, it is unsafe to touch the new reference,
+	 * since it is possible for a concurrent ioctl to remove it (by guessing
+	 * its index). If the userspace application doesn't provide valid memory
+	 * to write the IDs to, then it will need to close the file in order to
+	 * release - which it will do by segfaulting when it tries to access the
+	 * IDs to close them.
+	 */
+	if (copy_to_user(arg, &op, sizeof(op))) {
+		rc = -EFAULT;
+		goto out_free;
+	}
+	if (copy_to_user(arg->gref_ids_flex, gref_ids,
+			sizeof(gref_ids[0]) * op.count)) {
+		rc = -EFAULT;
+		goto out_free;
+	}
+
+out_free:
+	kfree(gref_ids);
+out:
+	return rc;
+}
+
+static long gntalloc_ioctl_dealloc(struct gntalloc_file_private_data *priv,
+		void __user *arg)
+{
+	int i, rc = 0;
+	struct ioctl_gntalloc_dealloc_gref op;
+	struct gntalloc_gref *gref, *n;
+
+	pr_debug("%s: priv %p\n", __func__, priv);
+
+	if (copy_from_user(&op, arg, sizeof(op))) {
+		rc = -EFAULT;
+		goto dealloc_grant_out;
+	}
+
+	mutex_lock(&gref_mutex);
+	gref = find_grefs(priv, op.index, op.count);
+	if (gref) {
+		/* Remove from the file list only, and decrease reference count.
+		 * The later call to do_cleanup() will remove from gref_list and
+		 * free the memory if the pages aren't mapped anywhere.
+		 */
+		for (i = 0; i < op.count; i++) {
+			n = list_entry(gref->next_file.next,
+				struct gntalloc_gref, next_file);
+			list_del(&gref->next_file);
+			gref->users--;
+			gref = n;
+		}
+	} else {
+		rc = -EINVAL;
+	}
+
+	do_cleanup();
+
+	mutex_unlock(&gref_mutex);
+dealloc_grant_out:
+	return rc;
+}
+
+static long gntalloc_ioctl_unmap_notify(struct gntalloc_file_private_data *priv,
+		void __user *arg)
+{
+	struct ioctl_gntalloc_unmap_notify op;
+	struct gntalloc_gref *gref;
+	uint64_t index;
+	int pgoff;
+	int rc;
+
+	if (copy_from_user(&op, arg, sizeof(op)))
+		return -EFAULT;
+
+	index = op.index & ~(PAGE_SIZE - 1);
+	pgoff = op.index & (PAGE_SIZE - 1);
+
+	mutex_lock(&gref_mutex);
+
+	gref = find_grefs(priv, index, 1);
+	if (!gref) {
+		rc = -ENOENT;
+		goto unlock_out;
+	}
+
+	if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE|UNMAP_NOTIFY_SEND_EVENT)) {
+		rc = -EINVAL;
+		goto unlock_out;
+	}
+
+	/* We need to grab a reference to the event channel we are going to use
+	 * to send the notify before releasing the reference we may already have
+	 * (if someone has called this ioctl twice). This is required so that
+	 * it is possible to change the clear_byte part of the notification
+	 * without disturbing the event channel part, which may now be the last
+	 * reference to that event channel.
+	 */
+	if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
+		if (evtchn_get(op.event_channel_port)) {
+			rc = -EINVAL;
+			goto unlock_out;
+		}
+	}
+
+	if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT)
+		evtchn_put(gref->notify.event);
+
+	gref->notify.flags = op.action;
+	gref->notify.pgoff = pgoff;
+	gref->notify.event = op.event_channel_port;
+	rc = 0;
+
+ unlock_out:
+	mutex_unlock(&gref_mutex);
+	return rc;
+}
+
+static long gntalloc_ioctl(struct file *filp, unsigned int cmd,
+		unsigned long arg)
+{
+	struct gntalloc_file_private_data *priv = filp->private_data;
+
+	switch (cmd) {
+	case IOCTL_GNTALLOC_ALLOC_GREF:
+		return gntalloc_ioctl_alloc(priv, (void __user *)arg);
+
+	case IOCTL_GNTALLOC_DEALLOC_GREF:
+		return gntalloc_ioctl_dealloc(priv, (void __user *)arg);
+
+	case IOCTL_GNTALLOC_SET_UNMAP_NOTIFY:
+		return gntalloc_ioctl_unmap_notify(priv, (void __user *)arg);
+
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	return 0;
+}
+
+static void gntalloc_vma_open(struct vm_area_struct *vma)
+{
+	struct gntalloc_vma_private_data *priv = vma->vm_private_data;
+
+	if (!priv)
+		return;
+
+	mutex_lock(&gref_mutex);
+	priv->users++;
+	mutex_unlock(&gref_mutex);
+}
+
+static void gntalloc_vma_close(struct vm_area_struct *vma)
+{
+	struct gntalloc_vma_private_data *priv = vma->vm_private_data;
+	struct gntalloc_gref *gref, *next;
+	int i;
+
+	if (!priv)
+		return;
+
+	mutex_lock(&gref_mutex);
+	priv->users--;
+	if (priv->users == 0) {
+		gref = priv->gref;
+		for (i = 0; i < priv->count; i++) {
+			gref->users--;
+			next = list_entry(gref->next_gref.next,
+					  struct gntalloc_gref, next_gref);
+			if (gref->users == 0)
+				__del_gref(gref);
+			gref = next;
+		}
+		kfree(priv);
+	}
+	mutex_unlock(&gref_mutex);
+}
+
+static const struct vm_operations_struct gntalloc_vmops = {
+	.open = gntalloc_vma_open,
+	.close = gntalloc_vma_close,
+};
+
+static int gntalloc_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct gntalloc_file_private_data *priv = filp->private_data;
+	struct gntalloc_vma_private_data *vm_priv;
+	struct gntalloc_gref *gref;
+	int count = vma_pages(vma);
+	int rv, i;
+
+	if (!(vma->vm_flags & VM_SHARED)) {
+		pr_err("%s: Mapping must be shared\n", __func__);
+		return -EINVAL;
+	}
+
+	vm_priv = kmalloc_obj(*vm_priv);
+	if (!vm_priv)
+		return -ENOMEM;
+
+	mutex_lock(&gref_mutex);
+
+	pr_debug("%s: priv %p,%p, page %lu+%d\n", __func__,
+		       priv, vm_priv, vma->vm_pgoff, count);
+
+	gref = find_grefs(priv, vma->vm_pgoff << PAGE_SHIFT, count);
+	if (gref == NULL) {
+		rv = -ENOENT;
+		pr_debug("%s: Could not find grant reference",
+				__func__);
+		kfree(vm_priv);
+		goto out_unlock;
+	}
+
+	vm_priv->gref = gref;
+	vm_priv->users = 1;
+	vm_priv->count = count;
+
+	vma->vm_private_data = vm_priv;
+
+	vm_flags_set(vma, VM_DONTEXPAND | VM_DONTDUMP);
+
+	vma->vm_ops = &gntalloc_vmops;
+
+	for (i = 0; i < count; i++) {
+		gref->users++;
+		rv = vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE,
+				gref->page);
+		if (rv)
+			goto out_unlock;
+
+		gref = list_entry(gref->next_file.next,
+				struct gntalloc_gref, next_file);
+	}
+	rv = 0;
+
+out_unlock:
+	mutex_unlock(&gref_mutex);
+	return rv;
+}
+
+static const struct file_operations gntalloc_fops = {
+	.owner = THIS_MODULE,
+	.open = gntalloc_open,
+	.release = gntalloc_release,
+	.unlocked_ioctl = gntalloc_ioctl,
+	.mmap = gntalloc_mmap
+};
+
+/*
+ * -------------------------------------
+ * Module creation/destruction.
+ * -------------------------------------
+ */
+static struct miscdevice gntalloc_miscdev = {
+	.minor	= MISC_DYNAMIC_MINOR,
+	.name	= "xen/gntalloc",
+	.fops	= &gntalloc_fops,
+};
+
+static int __init gntalloc_init(void)
+{
+	int err;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	err = misc_register(&gntalloc_miscdev);
+	if (err != 0) {
+		pr_err("Could not register misc gntalloc device\n");
+		return err;
+	}
+
+	pr_debug("Created grant allocation device at %d,%d\n",
+			MISC_MAJOR, gntalloc_miscdev.minor);
+
+	return 0;
+}
+
+static void __exit gntalloc_exit(void)
+{
+	misc_deregister(&gntalloc_miscdev);
+}
+
+module_init(gntalloc_init);
+module_exit(gntalloc_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Carter Weatherly <carter.weatherly@jhuapl.edu>, "
+		"Daniel De Graaf <dgdegra@tycho.nsa.gov>");
+MODULE_DESCRIPTION("User-space grant reference allocator driver");
diff --git a/drivers/xen/gntdev-common.h b/drivers/xen/gntdev-common.h
new file mode 100644
index 000000000..ac8ce3179
--- /dev/null
+++ b/drivers/xen/gntdev-common.h
@@ -0,0 +1,101 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Common functionality of grant device.
+ *
+ * Copyright (c) 2006-2007, D G Murray.
+ *           (c) 2009 Gerd Hoffmann <kraxel@redhat.com>
+ *           (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
+ */
+
+#ifndef _GNTDEV_COMMON_H
+#define _GNTDEV_COMMON_H
+
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/mmu_notifier.h>
+#include <linux/types.h>
+#include <xen/interface/event_channel.h>
+#include <xen/grant_table.h>
+
+struct gntdev_dmabuf_priv;
+
+struct gntdev_priv {
+	/* Maps with visible offsets in the file descriptor. */
+	struct list_head maps;
+	/* lock protects maps and freeable_maps. */
+	struct mutex lock;
+
+	/* Free instances of struct gntdev_copy_batch. */
+	struct gntdev_copy_batch *batch;
+	struct mutex batch_lock;
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	/* Device for which DMA memory is allocated. */
+	struct device *dma_dev;
+#endif
+
+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+	struct gntdev_dmabuf_priv *dmabuf_priv;
+#endif
+};
+
+struct gntdev_unmap_notify {
+	int flags;
+	/* Address relative to the start of the gntdev_grant_map. */
+	int addr;
+	evtchn_port_t event;
+};
+
+struct gntdev_grant_map {
+	atomic_t in_use;
+	struct mmu_interval_notifier notifier;
+	bool notifier_init;
+	struct list_head next;
+	int index;
+	int count;
+	int flags;
+	refcount_t users;
+	struct gntdev_unmap_notify notify;
+	struct ioctl_gntdev_grant_ref *grants;
+	struct gnttab_map_grant_ref   *map_ops;
+	struct gnttab_unmap_grant_ref *unmap_ops;
+	struct gnttab_map_grant_ref   *kmap_ops;
+	struct gnttab_unmap_grant_ref *kunmap_ops;
+	bool *being_removed;
+	struct page **pages;
+	unsigned long pages_vm_start;
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	/*
+	 * If dmabuf_vaddr is not NULL then this mapping is backed by DMA
+	 * capable memory.
+	 */
+
+	struct device *dma_dev;
+	/* Flags used to create this DMA buffer: GNTDEV_DMA_FLAG_XXX. */
+	int dma_flags;
+	void *dma_vaddr;
+	dma_addr_t dma_bus_addr;
+	/* Needed to avoid allocation in gnttab_dma_free_pages(). */
+	xen_pfn_t *frames;
+#endif
+
+	/* Number of live grants */
+	atomic_t live_grants;
+	/* Needed to avoid allocation in __unmap_grant_pages */
+	struct gntab_unmap_queue_data unmap_data;
+};
+
+struct gntdev_grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count,
+					  int dma_flags);
+
+void gntdev_add_map(struct gntdev_priv *priv, struct gntdev_grant_map *add);
+
+void gntdev_put_map(struct gntdev_priv *priv, struct gntdev_grant_map *map);
+
+bool gntdev_test_page_count(unsigned int count);
+
+int gntdev_map_grant_pages(struct gntdev_grant_map *map);
+
+#endif
diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c
new file mode 100644
index 000000000..83b0df460
--- /dev/null
+++ b/drivers/xen/gntdev-dmabuf.c
@@ -0,0 +1,837 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Xen dma-buf functionality for gntdev.
+ *
+ * DMA buffer implementation is based on drivers/gpu/drm/drm_prime.c.
+ *
+ * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-direct.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+
+#include <xen/xen.h>
+#include <xen/grant_table.h>
+
+#include "gntdev-common.h"
+#include "gntdev-dmabuf.h"
+
+MODULE_IMPORT_NS("DMA_BUF");
+
+struct gntdev_dmabuf {
+	struct gntdev_dmabuf_priv *priv;
+	struct dma_buf *dmabuf;
+	struct list_head next;
+	int fd;
+
+	union {
+		struct {
+			/* Exported buffers are reference counted. */
+			struct kref refcount;
+
+			struct gntdev_priv *priv;
+			struct gntdev_grant_map *map;
+		} exp;
+		struct {
+			/* Granted references of the imported buffer. */
+			grant_ref_t *refs;
+			/* Scatter-gather table of the imported buffer. */
+			struct sg_table *sgt;
+			/* dma-buf attachment of the imported buffer. */
+			struct dma_buf_attachment *attach;
+		} imp;
+	} u;
+
+	/* Number of pages this buffer has. */
+	int nr_pages;
+	/* Pages of this buffer (only for dma-buf export). */
+	struct page **pages;
+};
+
+struct gntdev_dmabuf_wait_obj {
+	struct list_head next;
+	struct gntdev_dmabuf *gntdev_dmabuf;
+	struct completion completion;
+};
+
+struct gntdev_dmabuf_attachment {
+	struct sg_table *sgt;
+	enum dma_data_direction dir;
+};
+
+struct gntdev_dmabuf_priv {
+	/* List of exported DMA buffers. */
+	struct list_head exp_list;
+	/* List of wait objects. */
+	struct list_head exp_wait_list;
+	/* List of imported DMA buffers. */
+	struct list_head imp_list;
+	/* This is the lock which protects dma_buf_xxx lists. */
+	struct mutex lock;
+	/*
+	 * We reference this file while exporting dma-bufs, so
+	 * the grant device context is not destroyed while there are
+	 * external users alive.
+	 */
+	struct file *filp;
+};
+
+/* DMA buffer export support. */
+
+/* Implementation of wait for exported DMA buffer to be released. */
+
+static void dmabuf_exp_release(struct kref *kref);
+
+static struct gntdev_dmabuf_wait_obj *
+dmabuf_exp_wait_obj_new(struct gntdev_dmabuf_priv *priv,
+			struct gntdev_dmabuf *gntdev_dmabuf)
+{
+	struct gntdev_dmabuf_wait_obj *obj;
+
+	obj = kzalloc_obj(*obj);
+	if (!obj)
+		return ERR_PTR(-ENOMEM);
+
+	init_completion(&obj->completion);
+	obj->gntdev_dmabuf = gntdev_dmabuf;
+
+	mutex_lock(&priv->lock);
+	list_add(&obj->next, &priv->exp_wait_list);
+	/* Put our reference and wait for gntdev_dmabuf's release to fire. */
+	kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release);
+	mutex_unlock(&priv->lock);
+	return obj;
+}
+
+static void dmabuf_exp_wait_obj_free(struct gntdev_dmabuf_priv *priv,
+				     struct gntdev_dmabuf_wait_obj *obj)
+{
+	mutex_lock(&priv->lock);
+	list_del(&obj->next);
+	mutex_unlock(&priv->lock);
+	kfree(obj);
+}
+
+static int dmabuf_exp_wait_obj_wait(struct gntdev_dmabuf_wait_obj *obj,
+				    u32 wait_to_ms)
+{
+	if (wait_for_completion_timeout(&obj->completion,
+			msecs_to_jiffies(wait_to_ms)) <= 0)
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+static void dmabuf_exp_wait_obj_signal(struct gntdev_dmabuf_priv *priv,
+				       struct gntdev_dmabuf *gntdev_dmabuf)
+{
+	struct gntdev_dmabuf_wait_obj *obj;
+
+	list_for_each_entry(obj, &priv->exp_wait_list, next)
+		if (obj->gntdev_dmabuf == gntdev_dmabuf) {
+			pr_debug("Found gntdev_dmabuf in the wait list, wake\n");
+			complete_all(&obj->completion);
+			break;
+		}
+}
+
+static struct gntdev_dmabuf *
+dmabuf_exp_wait_obj_get_dmabuf(struct gntdev_dmabuf_priv *priv, int fd)
+{
+	struct gntdev_dmabuf *gntdev_dmabuf, *ret = ERR_PTR(-ENOENT);
+
+	mutex_lock(&priv->lock);
+	list_for_each_entry(gntdev_dmabuf, &priv->exp_list, next)
+		if (gntdev_dmabuf->fd == fd) {
+			pr_debug("Found gntdev_dmabuf in the wait list\n");
+			kref_get(&gntdev_dmabuf->u.exp.refcount);
+			ret = gntdev_dmabuf;
+			break;
+		}
+	mutex_unlock(&priv->lock);
+	return ret;
+}
+
+static int dmabuf_exp_wait_released(struct gntdev_dmabuf_priv *priv, int fd,
+				    int wait_to_ms)
+{
+	struct gntdev_dmabuf *gntdev_dmabuf;
+	struct gntdev_dmabuf_wait_obj *obj;
+	int ret;
+
+	pr_debug("Will wait for dma-buf with fd %d\n", fd);
+	/*
+	 * Try to find the DMA buffer: if not found means that
+	 * either the buffer has already been released or file descriptor
+	 * provided is wrong.
+	 */
+	gntdev_dmabuf = dmabuf_exp_wait_obj_get_dmabuf(priv, fd);
+	if (IS_ERR(gntdev_dmabuf))
+		return PTR_ERR(gntdev_dmabuf);
+
+	/*
+	 * gntdev_dmabuf still exists and is reference count locked by us now,
+	 * so prepare to wait: allocate wait object and add it to the wait list,
+	 * so we can find it on release.
+	 */
+	obj = dmabuf_exp_wait_obj_new(priv, gntdev_dmabuf);
+	if (IS_ERR(obj))
+		return PTR_ERR(obj);
+
+	ret = dmabuf_exp_wait_obj_wait(obj, wait_to_ms);
+	dmabuf_exp_wait_obj_free(priv, obj);
+	return ret;
+}
+
+/* DMA buffer export support. */
+
+static struct sg_table *
+dmabuf_pages_to_sgt(struct page **pages, unsigned int nr_pages)
+{
+	struct sg_table *sgt;
+	int ret;
+
+	sgt = kmalloc_obj(*sgt);
+	if (!sgt) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = sg_alloc_table_from_pages(sgt, pages, nr_pages, 0,
+					nr_pages << PAGE_SHIFT,
+					GFP_KERNEL);
+	if (ret)
+		goto out;
+
+	return sgt;
+
+out:
+	kfree(sgt);
+	return ERR_PTR(ret);
+}
+
+static int dmabuf_exp_ops_attach(struct dma_buf *dma_buf,
+				 struct dma_buf_attachment *attach)
+{
+	struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach;
+
+	gntdev_dmabuf_attach = kzalloc_obj(*gntdev_dmabuf_attach);
+	if (!gntdev_dmabuf_attach)
+		return -ENOMEM;
+
+	gntdev_dmabuf_attach->dir = DMA_NONE;
+	attach->priv = gntdev_dmabuf_attach;
+	return 0;
+}
+
+static void dmabuf_exp_ops_detach(struct dma_buf *dma_buf,
+				  struct dma_buf_attachment *attach)
+{
+	struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv;
+
+	if (gntdev_dmabuf_attach) {
+		struct sg_table *sgt = gntdev_dmabuf_attach->sgt;
+
+		if (sgt) {
+			if (gntdev_dmabuf_attach->dir != DMA_NONE)
+				dma_unmap_sgtable(attach->dev, sgt,
+						  gntdev_dmabuf_attach->dir,
+						  DMA_ATTR_SKIP_CPU_SYNC);
+			sg_free_table(sgt);
+		}
+
+		kfree(sgt);
+		kfree(gntdev_dmabuf_attach);
+		attach->priv = NULL;
+	}
+}
+
+static struct sg_table *
+dmabuf_exp_ops_map_dma_buf(struct dma_buf_attachment *attach,
+			   enum dma_data_direction dir)
+{
+	struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv;
+	struct gntdev_dmabuf *gntdev_dmabuf = attach->dmabuf->priv;
+	struct sg_table *sgt;
+
+	pr_debug("Mapping %d pages for dev %p\n", gntdev_dmabuf->nr_pages,
+		 attach->dev);
+
+	if (dir == DMA_NONE || !gntdev_dmabuf_attach)
+		return ERR_PTR(-EINVAL);
+
+	/* Return the cached mapping when possible. */
+	if (gntdev_dmabuf_attach->dir == dir)
+		return gntdev_dmabuf_attach->sgt;
+
+	/*
+	 * Two mappings with different directions for the same attachment are
+	 * not allowed.
+	 */
+	if (gntdev_dmabuf_attach->dir != DMA_NONE)
+		return ERR_PTR(-EBUSY);
+
+	sgt = dmabuf_pages_to_sgt(gntdev_dmabuf->pages,
+				  gntdev_dmabuf->nr_pages);
+	if (!IS_ERR(sgt)) {
+		if (dma_map_sgtable(attach->dev, sgt, dir,
+				    DMA_ATTR_SKIP_CPU_SYNC)) {
+			sg_free_table(sgt);
+			kfree(sgt);
+			sgt = ERR_PTR(-ENOMEM);
+		} else {
+			gntdev_dmabuf_attach->sgt = sgt;
+			gntdev_dmabuf_attach->dir = dir;
+		}
+	}
+	if (IS_ERR(sgt))
+		pr_debug("Failed to map sg table for dev %p\n", attach->dev);
+	return sgt;
+}
+
+static void dmabuf_exp_ops_unmap_dma_buf(struct dma_buf_attachment *attach,
+					 struct sg_table *sgt,
+					 enum dma_data_direction dir)
+{
+	/* Not implemented. The unmap is done at dmabuf_exp_ops_detach(). */
+}
+
+static void dmabuf_exp_release(struct kref *kref)
+{
+	struct gntdev_dmabuf *gntdev_dmabuf =
+		container_of(kref, struct gntdev_dmabuf, u.exp.refcount);
+
+	dmabuf_exp_wait_obj_signal(gntdev_dmabuf->priv, gntdev_dmabuf);
+	list_del(&gntdev_dmabuf->next);
+	fput(gntdev_dmabuf->priv->filp);
+	kfree(gntdev_dmabuf);
+}
+
+static void dmabuf_exp_remove_map(struct gntdev_priv *priv,
+				  struct gntdev_grant_map *map)
+{
+	mutex_lock(&priv->lock);
+	list_del(&map->next);
+	gntdev_put_map(NULL /* already removed */, map);
+	mutex_unlock(&priv->lock);
+}
+
+static void dmabuf_exp_ops_release(struct dma_buf *dma_buf)
+{
+	struct gntdev_dmabuf *gntdev_dmabuf = dma_buf->priv;
+	struct gntdev_dmabuf_priv *priv = gntdev_dmabuf->priv;
+
+	dmabuf_exp_remove_map(gntdev_dmabuf->u.exp.priv,
+			      gntdev_dmabuf->u.exp.map);
+	mutex_lock(&priv->lock);
+	kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release);
+	mutex_unlock(&priv->lock);
+}
+
+static const struct dma_buf_ops dmabuf_exp_ops =  {
+	.attach = dmabuf_exp_ops_attach,
+	.detach = dmabuf_exp_ops_detach,
+	.map_dma_buf = dmabuf_exp_ops_map_dma_buf,
+	.unmap_dma_buf = dmabuf_exp_ops_unmap_dma_buf,
+	.release = dmabuf_exp_ops_release,
+};
+
+struct gntdev_dmabuf_export_args {
+	struct gntdev_priv *priv;
+	struct gntdev_grant_map *map;
+	struct gntdev_dmabuf_priv *dmabuf_priv;
+	struct device *dev;
+	int count;
+	struct page **pages;
+	u32 fd;
+};
+
+static int dmabuf_exp_from_pages(struct gntdev_dmabuf_export_args *args)
+{
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+	struct gntdev_dmabuf *gntdev_dmabuf __free(kfree) = NULL;
+	CLASS(get_unused_fd, ret)(O_CLOEXEC);
+
+	if (ret < 0)
+		return ret;
+
+	gntdev_dmabuf = kzalloc_obj(*gntdev_dmabuf);
+	if (!gntdev_dmabuf)
+		return -ENOMEM;
+
+	kref_init(&gntdev_dmabuf->u.exp.refcount);
+
+	gntdev_dmabuf->priv = args->dmabuf_priv;
+	gntdev_dmabuf->nr_pages = args->count;
+	gntdev_dmabuf->pages = args->pages;
+	gntdev_dmabuf->u.exp.priv = args->priv;
+	gntdev_dmabuf->u.exp.map = args->map;
+
+	exp_info.exp_name = KBUILD_MODNAME;
+	if (args->dev->driver && args->dev->driver->owner)
+		exp_info.owner = args->dev->driver->owner;
+	else
+		exp_info.owner = THIS_MODULE;
+	exp_info.ops = &dmabuf_exp_ops;
+	exp_info.size = args->count << PAGE_SHIFT;
+	exp_info.flags = O_RDWR;
+	exp_info.priv = gntdev_dmabuf;
+
+	gntdev_dmabuf->dmabuf = dma_buf_export(&exp_info);
+	if (IS_ERR(gntdev_dmabuf->dmabuf))
+		return PTR_ERR(gntdev_dmabuf->dmabuf);
+
+	gntdev_dmabuf->fd = ret;
+	args->fd = ret;
+
+	pr_debug("Exporting DMA buffer with fd %d\n", ret);
+
+	get_file(gntdev_dmabuf->priv->filp);
+	mutex_lock(&args->dmabuf_priv->lock);
+	list_add(&gntdev_dmabuf->next, &args->dmabuf_priv->exp_list);
+	mutex_unlock(&args->dmabuf_priv->lock);
+
+	fd_install(take_fd(ret), no_free_ptr(gntdev_dmabuf)->dmabuf->file);
+	return 0;
+}
+
+static struct gntdev_grant_map *
+dmabuf_exp_alloc_backing_storage(struct gntdev_priv *priv, int dmabuf_flags,
+				 int count)
+{
+	struct gntdev_grant_map *map;
+
+	if (unlikely(gntdev_test_page_count(count)))
+		return ERR_PTR(-EINVAL);
+
+	if ((dmabuf_flags & GNTDEV_DMA_FLAG_WC) &&
+	    (dmabuf_flags & GNTDEV_DMA_FLAG_COHERENT)) {
+		pr_debug("Wrong dma-buf flags: 0x%x\n", dmabuf_flags);
+		return ERR_PTR(-EINVAL);
+	}
+
+	map = gntdev_alloc_map(priv, count, dmabuf_flags);
+	if (!map)
+		return ERR_PTR(-ENOMEM);
+
+	return map;
+}
+
+static int dmabuf_exp_from_refs(struct gntdev_priv *priv, int flags,
+				int count, u32 domid, u32 *refs, u32 *fd)
+{
+	struct gntdev_grant_map *map;
+	struct gntdev_dmabuf_export_args args;
+	int i, ret;
+
+	map = dmabuf_exp_alloc_backing_storage(priv, flags, count);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	for (i = 0; i < count; i++) {
+		map->grants[i].domid = domid;
+		map->grants[i].ref = refs[i];
+	}
+
+	mutex_lock(&priv->lock);
+	gntdev_add_map(priv, map);
+	mutex_unlock(&priv->lock);
+
+	map->flags |= GNTMAP_host_map;
+#if defined(CONFIG_X86)
+	map->flags |= GNTMAP_device_map;
+#endif
+
+	ret = gntdev_map_grant_pages(map);
+	if (ret < 0)
+		goto out;
+
+	args.priv = priv;
+	args.map = map;
+	args.dev = priv->dma_dev;
+	args.dmabuf_priv = priv->dmabuf_priv;
+	args.count = map->count;
+	args.pages = map->pages;
+	args.fd = -1; /* Shut up unnecessary gcc warning for i386 */
+
+	ret = dmabuf_exp_from_pages(&args);
+	if (ret < 0)
+		goto out;
+
+	*fd = args.fd;
+	return 0;
+
+out:
+	dmabuf_exp_remove_map(priv, map);
+	return ret;
+}
+
+/* DMA buffer import support. */
+
+static int
+dmabuf_imp_grant_foreign_access(unsigned long *gfns, u32 *refs,
+				int count, int domid)
+{
+	grant_ref_t priv_gref_head;
+	int i, ret;
+
+	ret = gnttab_alloc_grant_references(count, &priv_gref_head);
+	if (ret < 0) {
+		pr_debug("Cannot allocate grant references, ret %d\n", ret);
+		return ret;
+	}
+
+	for (i = 0; i < count; i++) {
+		int cur_ref;
+
+		cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
+		if (cur_ref < 0) {
+			ret = cur_ref;
+			pr_debug("Cannot claim grant reference, ret %d\n", ret);
+			goto out;
+		}
+
+		gnttab_grant_foreign_access_ref(cur_ref, domid,
+						gfns[i], 0);
+		refs[i] = cur_ref;
+	}
+
+	return 0;
+
+out:
+	gnttab_free_grant_references(priv_gref_head);
+	return ret;
+}
+
+static void dmabuf_imp_end_foreign_access(u32 *refs, int count)
+{
+	int i;
+
+	for (i = 0; i < count; i++)
+		if (refs[i] != INVALID_GRANT_REF)
+			gnttab_end_foreign_access(refs[i], NULL);
+}
+
+static void dmabuf_imp_free_storage(struct gntdev_dmabuf *gntdev_dmabuf)
+{
+	kfree(gntdev_dmabuf->u.imp.refs);
+	kfree(gntdev_dmabuf);
+}
+
+static struct gntdev_dmabuf *dmabuf_imp_alloc_storage(int count)
+{
+	struct gntdev_dmabuf *gntdev_dmabuf;
+	int i;
+
+	gntdev_dmabuf = kzalloc_obj(*gntdev_dmabuf);
+	if (!gntdev_dmabuf)
+		goto fail_no_free;
+
+	gntdev_dmabuf->u.imp.refs = kzalloc_objs(gntdev_dmabuf->u.imp.refs[0],
+						 count);
+	if (!gntdev_dmabuf->u.imp.refs)
+		goto fail;
+
+	gntdev_dmabuf->nr_pages = count;
+
+	for (i = 0; i < count; i++)
+		gntdev_dmabuf->u.imp.refs[i] = INVALID_GRANT_REF;
+
+	return gntdev_dmabuf;
+
+fail:
+	dmabuf_imp_free_storage(gntdev_dmabuf);
+fail_no_free:
+	return ERR_PTR(-ENOMEM);
+}
+
+static struct gntdev_dmabuf *
+dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
+		   int fd, int count, int domid)
+{
+	struct gntdev_dmabuf *gntdev_dmabuf, *ret;
+	struct dma_buf *dma_buf;
+	struct dma_buf_attachment *attach;
+	struct sg_table *sgt;
+	struct sg_dma_page_iter sg_iter;
+	unsigned long *gfns;
+	int i;
+
+	dma_buf = dma_buf_get(fd);
+	if (IS_ERR(dma_buf))
+		return ERR_CAST(dma_buf);
+
+	gntdev_dmabuf = dmabuf_imp_alloc_storage(count);
+	if (IS_ERR(gntdev_dmabuf)) {
+		ret = gntdev_dmabuf;
+		goto fail_put;
+	}
+
+	gntdev_dmabuf->priv = priv;
+	gntdev_dmabuf->fd = fd;
+
+	attach = dma_buf_attach(dma_buf, dev);
+	if (IS_ERR(attach)) {
+		ret = ERR_CAST(attach);
+		goto fail_free_obj;
+	}
+
+	gntdev_dmabuf->u.imp.attach = attach;
+
+	sgt = dma_buf_map_attachment_unlocked(attach, DMA_BIDIRECTIONAL);
+	if (IS_ERR(sgt)) {
+		ret = ERR_CAST(sgt);
+		goto fail_detach;
+	}
+
+	/* Check that we have zero offset. */
+	if (sgt->sgl->offset) {
+		ret = ERR_PTR(-EINVAL);
+		pr_debug("DMA buffer has %d bytes offset, user-space expects 0\n",
+			 sgt->sgl->offset);
+		goto fail_unmap;
+	}
+
+	/* Check number of pages that imported buffer has. */
+	if (attach->dmabuf->size != gntdev_dmabuf->nr_pages << PAGE_SHIFT) {
+		ret = ERR_PTR(-EINVAL);
+		pr_debug("DMA buffer has %zu pages, user-space expects %d\n",
+			 attach->dmabuf->size, gntdev_dmabuf->nr_pages);
+		goto fail_unmap;
+	}
+
+	gntdev_dmabuf->u.imp.sgt = sgt;
+
+	gfns = kcalloc(count, sizeof(*gfns), GFP_KERNEL);
+	if (!gfns) {
+		ret = ERR_PTR(-ENOMEM);
+		goto fail_unmap;
+	}
+
+	/*
+	 * Now convert sgt to array of gfns without accessing underlying pages.
+	 * It is not allowed to access the underlying struct page of an sg table
+	 * exported by DMA-buf, but since we deal with special Xen dma device here
+	 * (not a normal physical one) look at the dma addresses in the sg table
+	 * and then calculate gfns directly from them.
+	 */
+	i = 0;
+	for_each_sgtable_dma_page(sgt, &sg_iter, 0) {
+		dma_addr_t addr = sg_page_iter_dma_address(&sg_iter);
+		unsigned long pfn = bfn_to_pfn(XEN_PFN_DOWN(dma_to_phys(dev, addr)));
+
+		gfns[i++] = pfn_to_gfn(pfn);
+	}
+
+	ret = ERR_PTR(dmabuf_imp_grant_foreign_access(gfns,
+						      gntdev_dmabuf->u.imp.refs,
+						      count, domid));
+	kfree(gfns);
+	if (IS_ERR(ret))
+		goto fail_end_access;
+
+	pr_debug("Imported DMA buffer with fd %d\n", fd);
+
+	mutex_lock(&priv->lock);
+	list_add(&gntdev_dmabuf->next, &priv->imp_list);
+	mutex_unlock(&priv->lock);
+
+	return gntdev_dmabuf;
+
+fail_end_access:
+	dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs, count);
+fail_unmap:
+	dma_buf_unmap_attachment_unlocked(attach, sgt, DMA_BIDIRECTIONAL);
+fail_detach:
+	dma_buf_detach(dma_buf, attach);
+fail_free_obj:
+	dmabuf_imp_free_storage(gntdev_dmabuf);
+fail_put:
+	dma_buf_put(dma_buf);
+	return ret;
+}
+
+/*
+ * Find the hyper dma-buf by its file descriptor and remove
+ * it from the buffer's list.
+ */
+static struct gntdev_dmabuf *
+dmabuf_imp_find_unlink(struct gntdev_dmabuf_priv *priv, int fd)
+{
+	struct gntdev_dmabuf *q, *gntdev_dmabuf, *ret = ERR_PTR(-ENOENT);
+
+	mutex_lock(&priv->lock);
+	list_for_each_entry_safe(gntdev_dmabuf, q, &priv->imp_list, next) {
+		if (gntdev_dmabuf->fd == fd) {
+			pr_debug("Found gntdev_dmabuf in the import list\n");
+			ret = gntdev_dmabuf;
+			list_del(&gntdev_dmabuf->next);
+			break;
+		}
+	}
+	mutex_unlock(&priv->lock);
+	return ret;
+}
+
+static int dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32 fd)
+{
+	struct gntdev_dmabuf *gntdev_dmabuf;
+	struct dma_buf_attachment *attach;
+	struct dma_buf *dma_buf;
+
+	gntdev_dmabuf = dmabuf_imp_find_unlink(priv, fd);
+	if (IS_ERR(gntdev_dmabuf))
+		return PTR_ERR(gntdev_dmabuf);
+
+	pr_debug("Releasing DMA buffer with fd %d\n", fd);
+
+	dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs,
+				      gntdev_dmabuf->nr_pages);
+
+	attach = gntdev_dmabuf->u.imp.attach;
+
+	if (gntdev_dmabuf->u.imp.sgt)
+		dma_buf_unmap_attachment_unlocked(attach, gntdev_dmabuf->u.imp.sgt,
+						  DMA_BIDIRECTIONAL);
+	dma_buf = attach->dmabuf;
+	dma_buf_detach(attach->dmabuf, attach);
+	dma_buf_put(dma_buf);
+
+	dmabuf_imp_free_storage(gntdev_dmabuf);
+	return 0;
+}
+
+static void dmabuf_imp_release_all(struct gntdev_dmabuf_priv *priv)
+{
+	struct gntdev_dmabuf *q, *gntdev_dmabuf;
+
+	list_for_each_entry_safe(gntdev_dmabuf, q, &priv->imp_list, next)
+		dmabuf_imp_release(priv, gntdev_dmabuf->fd);
+}
+
+/* DMA buffer IOCTL support. */
+
+long gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv *priv,
+				       struct ioctl_gntdev_dmabuf_exp_from_refs __user *u)
+{
+	struct ioctl_gntdev_dmabuf_exp_from_refs op;
+	u32 *refs;
+	long ret;
+
+	if (xen_pv_domain()) {
+		pr_debug("Cannot provide dma-buf in a PV domain\n");
+		return -EINVAL;
+	}
+
+	if (copy_from_user(&op, u, sizeof(op)) != 0)
+		return -EFAULT;
+
+	if (unlikely(gntdev_test_page_count(op.count)))
+		return -EINVAL;
+
+	refs = kcalloc(op.count, sizeof(*refs), GFP_KERNEL);
+	if (!refs)
+		return -ENOMEM;
+
+	if (copy_from_user(refs, u->refs, sizeof(*refs) * op.count) != 0) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	ret = dmabuf_exp_from_refs(priv, op.flags, op.count,
+				   op.domid, refs, &op.fd);
+	if (ret)
+		goto out;
+
+	if (copy_to_user(u, &op, sizeof(op)) != 0)
+		ret = -EFAULT;
+
+out:
+	kfree(refs);
+	return ret;
+}
+
+long gntdev_ioctl_dmabuf_exp_wait_released(struct gntdev_priv *priv,
+					   struct ioctl_gntdev_dmabuf_exp_wait_released __user *u)
+{
+	struct ioctl_gntdev_dmabuf_exp_wait_released op;
+
+	if (copy_from_user(&op, u, sizeof(op)) != 0)
+		return -EFAULT;
+
+	return dmabuf_exp_wait_released(priv->dmabuf_priv, op.fd,
+					op.wait_to_ms);
+}
+
+long gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv *priv,
+				     struct ioctl_gntdev_dmabuf_imp_to_refs __user *u)
+{
+	struct ioctl_gntdev_dmabuf_imp_to_refs op;
+	struct gntdev_dmabuf *gntdev_dmabuf;
+	long ret;
+
+	if (copy_from_user(&op, u, sizeof(op)) != 0)
+		return -EFAULT;
+
+	if (unlikely(gntdev_test_page_count(op.count)))
+		return -EINVAL;
+
+	gntdev_dmabuf = dmabuf_imp_to_refs(priv->dmabuf_priv,
+					   priv->dma_dev, op.fd,
+					   op.count, op.domid);
+	if (IS_ERR(gntdev_dmabuf))
+		return PTR_ERR(gntdev_dmabuf);
+
+	if (copy_to_user(u->refs, gntdev_dmabuf->u.imp.refs,
+			 sizeof(*u->refs) * op.count) != 0) {
+		ret = -EFAULT;
+		goto out_release;
+	}
+	return 0;
+
+out_release:
+	dmabuf_imp_release(priv->dmabuf_priv, op.fd);
+	return ret;
+}
+
+long gntdev_ioctl_dmabuf_imp_release(struct gntdev_priv *priv,
+				     struct ioctl_gntdev_dmabuf_imp_release __user *u)
+{
+	struct ioctl_gntdev_dmabuf_imp_release op;
+
+	if (copy_from_user(&op, u, sizeof(op)) != 0)
+		return -EFAULT;
+
+	return dmabuf_imp_release(priv->dmabuf_priv, op.fd);
+}
+
+struct gntdev_dmabuf_priv *gntdev_dmabuf_init(struct file *filp)
+{
+	struct gntdev_dmabuf_priv *priv;
+
+	priv = kzalloc_obj(*priv);
+	if (!priv)
+		return ERR_PTR(-ENOMEM);
+
+	mutex_init(&priv->lock);
+	INIT_LIST_HEAD(&priv->exp_list);
+	INIT_LIST_HEAD(&priv->exp_wait_list);
+	INIT_LIST_HEAD(&priv->imp_list);
+
+	priv->filp = filp;
+
+	return priv;
+}
+
+void gntdev_dmabuf_fini(struct gntdev_dmabuf_priv *priv)
+{
+	dmabuf_imp_release_all(priv);
+	kfree(priv);
+}
diff --git a/drivers/xen/gntdev-dmabuf.h b/drivers/xen/gntdev-dmabuf.h
new file mode 100644
index 000000000..9adf96ac7
--- /dev/null
+++ b/drivers/xen/gntdev-dmabuf.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Xen dma-buf functionality for gntdev.
+ *
+ * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
+ */
+
+#ifndef _GNTDEV_DMABUF_H
+#define _GNTDEV_DMABUF_H
+
+#include <xen/gntdev.h>
+
+struct gntdev_dmabuf_priv;
+struct gntdev_priv;
+
+struct gntdev_dmabuf_priv *gntdev_dmabuf_init(struct file *filp);
+
+void gntdev_dmabuf_fini(struct gntdev_dmabuf_priv *priv);
+
+long gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv *priv,
+				       struct ioctl_gntdev_dmabuf_exp_from_refs __user *u);
+
+long gntdev_ioctl_dmabuf_exp_wait_released(struct gntdev_priv *priv,
+					   struct ioctl_gntdev_dmabuf_exp_wait_released __user *u);
+
+long gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv *priv,
+				     struct ioctl_gntdev_dmabuf_imp_to_refs __user *u);
+
+long gntdev_ioctl_dmabuf_imp_release(struct gntdev_priv *priv,
+				     struct ioctl_gntdev_dmabuf_imp_release __user *u);
+
+#endif
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
new file mode 100644
index 000000000..1dcc46755
--- /dev/null
+++ b/drivers/xen/gntdev.c
@@ -0,0 +1,1198 @@
+/******************************************************************************
+ * gntdev.c
+ *
+ * Device for accessing (in user-space) pages that have been granted by other
+ * domains.
+ *
+ * Copyright (c) 2006-2007, D G Murray.
+ *           (c) 2009 Gerd Hoffmann <kraxel@redhat.com>
+ *           (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#undef DEBUG
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/dma-mapping.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/miscdevice.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/sched.h>
+#include <linux/sched/mm.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/highmem.h>
+#include <linux/refcount.h>
+#include <linux/workqueue.h>
+
+#include <xen/xen.h>
+#include <xen/grant_table.h>
+#include <xen/balloon.h>
+#include <xen/gntdev.h>
+#include <xen/events.h>
+#include <xen/page.h>
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+
+#include "gntdev-common.h"
+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+#include "gntdev-dmabuf.h"
+#endif
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Derek G. Murray <Derek.Murray@cl.cam.ac.uk>, "
+	      "Gerd Hoffmann <kraxel@redhat.com>");
+MODULE_DESCRIPTION("User-space granted page access driver");
+
+#define GNTDEV_COPY_BATCH 16
+
+struct gntdev_copy_batch {
+	struct gnttab_copy ops[GNTDEV_COPY_BATCH];
+	struct page *pages[GNTDEV_COPY_BATCH];
+	s16 __user *status[GNTDEV_COPY_BATCH];
+	unsigned int nr_ops;
+	unsigned int nr_pages;
+	bool writeable;
+	struct gntdev_copy_batch *next;
+};
+
+static unsigned int limit = 64*1024;
+module_param(limit, uint, 0644);
+MODULE_PARM_DESC(limit,
+	"Maximum number of grants that may be mapped by one mapping request");
+
+static void unmap_grant_pages(struct gntdev_grant_map *map,
+			      int offset, int pages);
+
+static struct miscdevice gntdev_miscdev;
+
+/* ------------------------------------------------------------------ */
+
+bool gntdev_test_page_count(unsigned int count)
+{
+	return !count || count > limit;
+}
+
+static void gntdev_print_maps(struct gntdev_priv *priv,
+			      char *text, int text_index)
+{
+#ifdef DEBUG
+	struct gntdev_grant_map *map;
+
+	pr_debug("%s: maps list (priv %p)\n", __func__, priv);
+	list_for_each_entry(map, &priv->maps, next)
+		pr_debug("  index %2d, count %2d %s\n",
+		       map->index, map->count,
+		       map->index == text_index && text ? text : "");
+#endif
+}
+
+static void gntdev_free_map(struct gntdev_grant_map *map)
+{
+	if (map == NULL)
+		return;
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	if (map->dma_vaddr) {
+		struct gnttab_dma_alloc_args args;
+
+		args.dev = map->dma_dev;
+		args.coherent = !!(map->dma_flags & GNTDEV_DMA_FLAG_COHERENT);
+		args.nr_pages = map->count;
+		args.pages = map->pages;
+		args.frames = map->frames;
+		args.vaddr = map->dma_vaddr;
+		args.dev_bus_addr = map->dma_bus_addr;
+
+		gnttab_dma_free_pages(&args);
+	} else
+#endif
+	if (map->pages)
+		gnttab_free_pages(map->count, map->pages);
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	kvfree(map->frames);
+#endif
+	kvfree(map->pages);
+	kvfree(map->grants);
+	kvfree(map->map_ops);
+	kvfree(map->unmap_ops);
+	kvfree(map->kmap_ops);
+	kvfree(map->kunmap_ops);
+	kvfree(map->being_removed);
+	kfree(map);
+}
+
+struct gntdev_grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count,
+					  int dma_flags)
+{
+	struct gntdev_grant_map *add;
+	int i;
+
+	add = kzalloc_obj(*add);
+	if (NULL == add)
+		return NULL;
+
+	add->grants    = kvmalloc_objs(add->grants[0], count);
+	add->map_ops   = kvmalloc_objs(add->map_ops[0], count);
+	add->unmap_ops = kvmalloc_objs(add->unmap_ops[0], count);
+	add->pages     = kvzalloc_objs(add->pages[0], count);
+	add->being_removed =
+		kvzalloc_objs(add->being_removed[0], count);
+	if (NULL == add->grants    ||
+	    NULL == add->map_ops   ||
+	    NULL == add->unmap_ops ||
+	    NULL == add->pages     ||
+	    NULL == add->being_removed)
+		goto err;
+	if (xen_pv_domain()) {
+		add->kmap_ops   = kvmalloc_objs(add->kmap_ops[0], count);
+		add->kunmap_ops = kvmalloc_objs(add->kunmap_ops[0], count);
+		if (NULL == add->kmap_ops || NULL == add->kunmap_ops)
+			goto err;
+	}
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	add->dma_flags = dma_flags;
+
+	/*
+	 * Check if this mapping is requested to be backed
+	 * by a DMA buffer.
+	 */
+	if (dma_flags & (GNTDEV_DMA_FLAG_WC | GNTDEV_DMA_FLAG_COHERENT)) {
+		struct gnttab_dma_alloc_args args;
+
+		add->frames = kvzalloc_objs(add->frames[0], count);
+		if (!add->frames)
+			goto err;
+
+		/* Remember the device, so we can free DMA memory. */
+		add->dma_dev = priv->dma_dev;
+
+		args.dev = priv->dma_dev;
+		args.coherent = !!(dma_flags & GNTDEV_DMA_FLAG_COHERENT);
+		args.nr_pages = count;
+		args.pages = add->pages;
+		args.frames = add->frames;
+
+		if (gnttab_dma_alloc_pages(&args))
+			goto err;
+
+		add->dma_vaddr = args.vaddr;
+		add->dma_bus_addr = args.dev_bus_addr;
+	} else
+#endif
+	if (gnttab_alloc_pages(count, add->pages))
+		goto err;
+
+	for (i = 0; i < count; i++) {
+		add->grants[i].domid = DOMID_INVALID;
+		add->grants[i].ref = INVALID_GRANT_REF;
+		add->map_ops[i].handle = INVALID_GRANT_HANDLE;
+		add->unmap_ops[i].handle = INVALID_GRANT_HANDLE;
+		if (xen_pv_domain()) {
+			add->kmap_ops[i].handle = INVALID_GRANT_HANDLE;
+			add->kunmap_ops[i].handle = INVALID_GRANT_HANDLE;
+		}
+	}
+
+	add->index = 0;
+	add->count = count;
+	refcount_set(&add->users, 1);
+
+	return add;
+
+err:
+	gntdev_free_map(add);
+	return NULL;
+}
+
+void gntdev_add_map(struct gntdev_priv *priv, struct gntdev_grant_map *add)
+{
+	struct gntdev_grant_map *map;
+
+	list_for_each_entry(map, &priv->maps, next) {
+		if (add->index + add->count < map->index) {
+			list_add_tail(&add->next, &map->next);
+			goto done;
+		}
+		add->index = map->index + map->count;
+	}
+	list_add_tail(&add->next, &priv->maps);
+
+done:
+	gntdev_print_maps(priv, "[new]", add->index);
+}
+
+static struct gntdev_grant_map *gntdev_find_map_index(struct gntdev_priv *priv,
+						      int index, int count)
+{
+	struct gntdev_grant_map *map;
+
+	list_for_each_entry(map, &priv->maps, next) {
+		if (map->index != index)
+			continue;
+		if (count && map->count != count)
+			continue;
+		return map;
+	}
+	return NULL;
+}
+
+void gntdev_put_map(struct gntdev_priv *priv, struct gntdev_grant_map *map)
+{
+	if (!map)
+		return;
+
+	if (!refcount_dec_and_test(&map->users))
+		return;
+
+	if (map->pages && !xen_pv_domain()) {
+		/*
+		 * Increment the reference count.  This ensures that the
+		 * subsequent call to unmap_grant_pages() will not wind up
+		 * re-entering itself.  It *can* wind up calling
+		 * gntdev_put_map() recursively, but such calls will be with a
+		 * reference count greater than 1, so they will return before
+		 * this code is reached.  The recursion depth is thus limited to
+		 * 1.  Do NOT use refcount_inc() here, as it will detect that
+		 * the reference count is zero and WARN().
+		 */
+		refcount_set(&map->users, 1);
+
+		/*
+		 * Unmap the grants.  This may or may not be asynchronous, so it
+		 * is possible that the reference count is 1 on return, but it
+		 * could also be greater than 1.
+		 */
+		unmap_grant_pages(map, 0, map->count);
+
+		/* Check if the memory now needs to be freed */
+		if (!refcount_dec_and_test(&map->users))
+			return;
+
+		/*
+		 * All pages have been returned to the hypervisor, so free the
+		 * map.
+		 */
+	}
+
+	if (xen_pv_domain() && map->notifier_init)
+		mmu_interval_notifier_remove(&map->notifier);
+
+	if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
+		notify_remote_via_evtchn(map->notify.event);
+		evtchn_put(map->notify.event);
+	}
+	gntdev_free_map(map);
+}
+
+/* ------------------------------------------------------------------ */
+
+static int find_grant_ptes(pte_t *pte, unsigned long addr, void *data)
+{
+	struct gntdev_grant_map *map = data;
+	unsigned int pgnr = (addr - map->pages_vm_start) >> PAGE_SHIFT;
+	int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte |
+		    (1 << _GNTMAP_guest_avail0);
+	u64 pte_maddr;
+
+	BUG_ON(pgnr >= map->count);
+	pte_maddr = arbitrary_virt_to_machine(pte).maddr;
+
+	/* Note: this will perform a pte_mkspecial() through the hypercall. */
+	gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,
+			  map->grants[pgnr].ref,
+			  map->grants[pgnr].domid);
+	gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr, flags,
+			    INVALID_GRANT_HANDLE);
+	return 0;
+}
+
+int gntdev_map_grant_pages(struct gntdev_grant_map *map)
+{
+	size_t alloced = 0;
+	int i, err = 0;
+
+	if (!xen_pv_domain()) {
+		/* Note: it could already be mapped */
+		if (map->map_ops[0].handle != INVALID_GRANT_HANDLE)
+			return 0;
+		for (i = 0; i < map->count; i++) {
+			unsigned long addr = (unsigned long)
+				pfn_to_kaddr(page_to_pfn(map->pages[i]));
+			gnttab_set_map_op(&map->map_ops[i], addr, map->flags,
+				map->grants[i].ref,
+				map->grants[i].domid);
+			gnttab_set_unmap_op(&map->unmap_ops[i], addr,
+				map->flags, INVALID_GRANT_HANDLE);
+		}
+	} else {
+		/*
+		 * Setup the map_ops corresponding to the pte entries pointing
+		 * to the kernel linear addresses of the struct pages.
+		 * These ptes are completely different from the user ptes dealt
+		 * with find_grant_ptes.
+		 * Note that GNTMAP_device_map isn't needed here: The
+		 * dev_bus_addr output field gets consumed only from ->map_ops,
+		 * and by not requesting it when mapping we also avoid needing
+		 * to mirror dev_bus_addr into ->unmap_ops (and holding an extra
+		 * reference to the page in the hypervisor).
+		 */
+		unsigned int flags = (map->flags & ~GNTMAP_device_map) |
+				     GNTMAP_host_map;
+
+		for (i = 0; i < map->count; i++) {
+			unsigned long address = (unsigned long)
+				pfn_to_kaddr(page_to_pfn(map->pages[i]));
+			BUG_ON(PageHighMem(map->pages[i]));
+
+			gnttab_set_map_op(&map->kmap_ops[i], address, flags,
+				map->grants[i].ref,
+				map->grants[i].domid);
+			gnttab_set_unmap_op(&map->kunmap_ops[i], address,
+				flags, INVALID_GRANT_HANDLE);
+		}
+	}
+
+	pr_debug("map %d+%d\n", map->index, map->count);
+	err = gnttab_map_refs(map->map_ops, map->kmap_ops, map->pages,
+			map->count);
+
+	for (i = 0; i < map->count; i++) {
+		if (map->map_ops[i].status == GNTST_okay) {
+			map->unmap_ops[i].handle = map->map_ops[i].handle;
+			alloced++;
+		} else if (!err)
+			err = -EINVAL;
+
+		if (map->flags & GNTMAP_device_map)
+			map->unmap_ops[i].dev_bus_addr = map->map_ops[i].dev_bus_addr;
+
+		if (xen_pv_domain()) {
+			if (map->kmap_ops[i].status == GNTST_okay) {
+				alloced++;
+				map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
+			} else if (!err)
+				err = -EINVAL;
+		}
+	}
+	atomic_add(alloced, &map->live_grants);
+	return err;
+}
+
+static void __unmap_grant_pages_done(int result,
+		struct gntab_unmap_queue_data *data)
+{
+	unsigned int i;
+	struct gntdev_grant_map *map = data->data;
+	unsigned int offset = data->unmap_ops - map->unmap_ops;
+	int successful_unmaps = 0;
+	int live_grants;
+
+	for (i = 0; i < data->count; i++) {
+		if (map->unmap_ops[offset + i].status == GNTST_okay &&
+		    map->unmap_ops[offset + i].handle != INVALID_GRANT_HANDLE)
+			successful_unmaps++;
+
+		WARN_ON(map->unmap_ops[offset + i].status != GNTST_okay &&
+			map->unmap_ops[offset + i].handle != INVALID_GRANT_HANDLE);
+		pr_debug("unmap handle=%d st=%d\n",
+			map->unmap_ops[offset+i].handle,
+			map->unmap_ops[offset+i].status);
+		map->unmap_ops[offset+i].handle = INVALID_GRANT_HANDLE;
+		if (xen_pv_domain()) {
+			if (map->kunmap_ops[offset + i].status == GNTST_okay &&
+			    map->kunmap_ops[offset + i].handle != INVALID_GRANT_HANDLE)
+				successful_unmaps++;
+
+			WARN_ON(map->kunmap_ops[offset + i].status != GNTST_okay &&
+				map->kunmap_ops[offset + i].handle != INVALID_GRANT_HANDLE);
+			pr_debug("kunmap handle=%u st=%d\n",
+				 map->kunmap_ops[offset+i].handle,
+				 map->kunmap_ops[offset+i].status);
+			map->kunmap_ops[offset+i].handle = INVALID_GRANT_HANDLE;
+		}
+	}
+
+	/*
+	 * Decrease the live-grant counter.  This must happen after the loop to
+	 * prevent premature reuse of the grants by gnttab_mmap().
+	 */
+	live_grants = atomic_sub_return(successful_unmaps, &map->live_grants);
+	if (WARN_ON(live_grants < 0))
+		pr_err("%s: live_grants became negative (%d) after unmapping %d pages!\n",
+		       __func__, live_grants, successful_unmaps);
+
+	/* Release reference taken by __unmap_grant_pages */
+	gntdev_put_map(NULL, map);
+}
+
+static void __unmap_grant_pages(struct gntdev_grant_map *map, int offset,
+			       int pages)
+{
+	if (map->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
+		int pgno = (map->notify.addr >> PAGE_SHIFT);
+
+		if (pgno >= offset && pgno < offset + pages) {
+			/* No need for kmap, pages are in lowmem */
+			uint8_t *tmp = pfn_to_kaddr(page_to_pfn(map->pages[pgno]));
+
+			tmp[map->notify.addr & (PAGE_SIZE-1)] = 0;
+			map->notify.flags &= ~UNMAP_NOTIFY_CLEAR_BYTE;
+		}
+	}
+
+	map->unmap_data.unmap_ops = map->unmap_ops + offset;
+	map->unmap_data.kunmap_ops = xen_pv_domain() ? map->kunmap_ops + offset : NULL;
+	map->unmap_data.pages = map->pages + offset;
+	map->unmap_data.count = pages;
+	map->unmap_data.done = __unmap_grant_pages_done;
+	map->unmap_data.data = map;
+	refcount_inc(&map->users); /* to keep map alive during async call below */
+
+	gnttab_unmap_refs_async(&map->unmap_data);
+}
+
+static void unmap_grant_pages(struct gntdev_grant_map *map, int offset,
+			      int pages)
+{
+	int range;
+
+	if (atomic_read(&map->live_grants) == 0)
+		return; /* Nothing to do */
+
+	pr_debug("unmap %d+%d [%d+%d]\n", map->index, map->count, offset, pages);
+
+	/* It is possible the requested range will have a "hole" where we
+	 * already unmapped some of the grants. Only unmap valid ranges.
+	 */
+	while (pages) {
+		while (pages && map->being_removed[offset]) {
+			offset++;
+			pages--;
+		}
+		range = 0;
+		while (range < pages) {
+			if (map->being_removed[offset + range])
+				break;
+			map->being_removed[offset + range] = true;
+			range++;
+		}
+		if (range)
+			__unmap_grant_pages(map, offset, range);
+		offset += range;
+		pages -= range;
+	}
+}
+
+/* ------------------------------------------------------------------ */
+
+static void gntdev_vma_open(struct vm_area_struct *vma)
+{
+	struct gntdev_grant_map *map = vma->vm_private_data;
+
+	pr_debug("gntdev_vma_open %p\n", vma);
+	refcount_inc(&map->users);
+}
+
+static void gntdev_vma_close(struct vm_area_struct *vma)
+{
+	struct gntdev_grant_map *map = vma->vm_private_data;
+	struct file *file = vma->vm_file;
+	struct gntdev_priv *priv = file->private_data;
+
+	pr_debug("gntdev_vma_close %p\n", vma);
+
+	vma->vm_private_data = NULL;
+	gntdev_put_map(priv, map);
+}
+
+static struct page *gntdev_vma_find_normal_page(struct vm_area_struct *vma,
+						 unsigned long addr)
+{
+	struct gntdev_grant_map *map = vma->vm_private_data;
+
+	return map->pages[(addr - map->pages_vm_start) >> PAGE_SHIFT];
+}
+
+static const struct vm_operations_struct gntdev_vmops = {
+	.open = gntdev_vma_open,
+	.close = gntdev_vma_close,
+	.find_normal_page = gntdev_vma_find_normal_page,
+};
+
+/* ------------------------------------------------------------------ */
+
+static bool gntdev_invalidate(struct mmu_interval_notifier *mn,
+			      const struct mmu_notifier_range *range,
+			      unsigned long cur_seq)
+{
+	struct gntdev_grant_map *map =
+		container_of(mn, struct gntdev_grant_map, notifier);
+	unsigned long mstart, mend;
+	unsigned long map_start, map_end;
+
+	if (!mmu_notifier_range_blockable(range))
+		return false;
+
+	map_start = map->pages_vm_start;
+	map_end = map->pages_vm_start + (map->count << PAGE_SHIFT);
+
+	/*
+	 * If the VMA is split or otherwise changed the notifier is not
+	 * updated, but we don't want to process VA's outside the modified
+	 * VMA. FIXME: It would be much more understandable to just prevent
+	 * modifying the VMA in the first place.
+	 */
+	if (map_start >= range->end || map_end <= range->start)
+		return true;
+
+	mstart = max(range->start, map_start);
+	mend = min(range->end, map_end);
+	pr_debug("map %d+%d (%lx %lx), range %lx %lx, mrange %lx %lx\n",
+		 map->index, map->count, map_start, map_end,
+		 range->start, range->end, mstart, mend);
+	unmap_grant_pages(map, (mstart - map_start) >> PAGE_SHIFT,
+			  (mend - mstart) >> PAGE_SHIFT);
+
+	return true;
+}
+
+static const struct mmu_interval_notifier_ops gntdev_mmu_ops = {
+	.invalidate = gntdev_invalidate,
+};
+
+/* ------------------------------------------------------------------ */
+
+static int gntdev_open(struct inode *inode, struct file *flip)
+{
+	struct gntdev_priv *priv;
+
+	priv = kzalloc_obj(*priv);
+	if (!priv)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&priv->maps);
+	mutex_init(&priv->lock);
+
+	mutex_init(&priv->batch_lock);
+
+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+	priv->dmabuf_priv = gntdev_dmabuf_init(flip);
+	if (IS_ERR(priv->dmabuf_priv)) {
+		int ret = PTR_ERR(priv->dmabuf_priv);
+
+		kfree(priv);
+		return ret;
+	}
+#endif
+
+	flip->private_data = priv;
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+	priv->dma_dev = gntdev_miscdev.this_device;
+	dma_coerce_mask_and_coherent(priv->dma_dev, DMA_BIT_MASK(64));
+#endif
+	pr_debug("priv %p\n", priv);
+
+	return 0;
+}
+
+static int gntdev_release(struct inode *inode, struct file *flip)
+{
+	struct gntdev_priv *priv = flip->private_data;
+	struct gntdev_grant_map *map;
+	struct gntdev_copy_batch *batch;
+
+	pr_debug("priv %p\n", priv);
+
+	mutex_lock(&priv->lock);
+	while (!list_empty(&priv->maps)) {
+		map = list_entry(priv->maps.next,
+				 struct gntdev_grant_map, next);
+		list_del(&map->next);
+		gntdev_put_map(NULL /* already removed */, map);
+	}
+	mutex_unlock(&priv->lock);
+
+	mutex_lock(&priv->batch_lock);
+	while (priv->batch) {
+		batch = priv->batch;
+		priv->batch = batch->next;
+		kfree(batch);
+	}
+	mutex_unlock(&priv->batch_lock);
+
+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+	gntdev_dmabuf_fini(priv->dmabuf_priv);
+#endif
+
+	kfree(priv);
+	return 0;
+}
+
+static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv,
+				       struct ioctl_gntdev_map_grant_ref __user *u)
+{
+	struct ioctl_gntdev_map_grant_ref op;
+	struct gntdev_grant_map *map;
+	int err;
+
+	if (copy_from_user(&op, u, sizeof(op)) != 0)
+		return -EFAULT;
+	pr_debug("priv %p, add %d\n", priv, op.count);
+	if (unlikely(gntdev_test_page_count(op.count)))
+		return -EINVAL;
+
+	err = -ENOMEM;
+	map = gntdev_alloc_map(priv, op.count, 0 /* This is not a dma-buf. */);
+	if (!map)
+		return err;
+
+	if (copy_from_user(map->grants, &u->refs,
+			   sizeof(map->grants[0]) * op.count) != 0) {
+		gntdev_put_map(NULL, map);
+		return -EFAULT;
+	}
+
+	mutex_lock(&priv->lock);
+	gntdev_add_map(priv, map);
+	op.index = map->index << PAGE_SHIFT;
+
+	if (copy_to_user(u, &op, sizeof(op)) != 0) {
+		list_del(&map->next);
+		mutex_unlock(&priv->lock);
+		gntdev_put_map(priv, map);
+		return -EFAULT;
+	}
+
+	mutex_unlock(&priv->lock);
+	return 0;
+}
+
+static long gntdev_ioctl_unmap_grant_ref(struct gntdev_priv *priv,
+					 struct ioctl_gntdev_unmap_grant_ref __user *u)
+{
+	struct ioctl_gntdev_unmap_grant_ref op;
+	struct gntdev_grant_map *map;
+	int err = -ENOENT;
+
+	if (copy_from_user(&op, u, sizeof(op)) != 0)
+		return -EFAULT;
+	pr_debug("priv %p, del %d+%d\n", priv, (int)op.index, (int)op.count);
+
+	mutex_lock(&priv->lock);
+	map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);
+	if (map) {
+		list_del(&map->next);
+		err = 0;
+	}
+	mutex_unlock(&priv->lock);
+	if (map)
+		gntdev_put_map(priv, map);
+	return err;
+}
+
+static long gntdev_ioctl_get_offset_for_vaddr(struct gntdev_priv *priv,
+					      struct ioctl_gntdev_get_offset_for_vaddr __user *u)
+{
+	struct ioctl_gntdev_get_offset_for_vaddr op;
+	struct vm_area_struct *vma;
+	struct gntdev_grant_map *map;
+	int rv = -EINVAL;
+
+	if (copy_from_user(&op, u, sizeof(op)) != 0)
+		return -EFAULT;
+	pr_debug("priv %p, offset for vaddr %lx\n", priv, (unsigned long)op.vaddr);
+
+	mmap_read_lock(current->mm);
+	vma = find_vma(current->mm, op.vaddr);
+	if (!vma || vma->vm_ops != &gntdev_vmops)
+		goto out_unlock;
+
+	map = vma->vm_private_data;
+	if (!map)
+		goto out_unlock;
+
+	op.offset = map->index << PAGE_SHIFT;
+	op.count = map->count;
+	rv = 0;
+
+ out_unlock:
+	mmap_read_unlock(current->mm);
+
+	if (rv == 0 && copy_to_user(u, &op, sizeof(op)) != 0)
+		return -EFAULT;
+	return rv;
+}
+
+static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)
+{
+	struct ioctl_gntdev_unmap_notify op;
+	struct gntdev_grant_map *map;
+	int rc;
+	int out_flags;
+	evtchn_port_t out_event;
+
+	if (copy_from_user(&op, u, sizeof(op)))
+		return -EFAULT;
+
+	if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE|UNMAP_NOTIFY_SEND_EVENT))
+		return -EINVAL;
+
+	/* We need to grab a reference to the event channel we are going to use
+	 * to send the notify before releasing the reference we may already have
+	 * (if someone has called this ioctl twice). This is required so that
+	 * it is possible to change the clear_byte part of the notification
+	 * without disturbing the event channel part, which may now be the last
+	 * reference to that event channel.
+	 */
+	if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
+		if (evtchn_get(op.event_channel_port))
+			return -EINVAL;
+	}
+
+	out_flags = op.action;
+	out_event = op.event_channel_port;
+
+	mutex_lock(&priv->lock);
+
+	list_for_each_entry(map, &priv->maps, next) {
+		uint64_t begin = map->index << PAGE_SHIFT;
+		uint64_t end = (map->index + map->count) << PAGE_SHIFT;
+		if (op.index >= begin && op.index < end)
+			goto found;
+	}
+	rc = -ENOENT;
+	goto unlock_out;
+
+ found:
+	if ((op.action & UNMAP_NOTIFY_CLEAR_BYTE) &&
+			(map->flags & GNTMAP_readonly)) {
+		rc = -EINVAL;
+		goto unlock_out;
+	}
+
+	out_flags = map->notify.flags;
+	out_event = map->notify.event;
+
+	map->notify.flags = op.action;
+	map->notify.addr = op.index - (map->index << PAGE_SHIFT);
+	map->notify.event = op.event_channel_port;
+
+	rc = 0;
+
+ unlock_out:
+	mutex_unlock(&priv->lock);
+
+	/* Drop the reference to the event channel we did not save in the map */
+	if (out_flags & UNMAP_NOTIFY_SEND_EVENT)
+		evtchn_put(out_event);
+
+	return rc;
+}
+
+static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt,
+				unsigned long *gfn)
+{
+	unsigned long addr = (unsigned long)virt;
+	struct page *page;
+	unsigned long xen_pfn;
+	int ret;
+
+	ret = pin_user_pages_fast(addr, 1, batch->writeable ? FOLL_WRITE : 0, &page);
+	if (ret < 0)
+		return ret;
+
+	batch->pages[batch->nr_pages++] = page;
+
+	xen_pfn = page_to_xen_pfn(page) + XEN_PFN_DOWN(addr & ~PAGE_MASK);
+	*gfn = pfn_to_gfn(xen_pfn);
+
+	return 0;
+}
+
+static void gntdev_put_pages(struct gntdev_copy_batch *batch)
+{
+	unpin_user_pages_dirty_lock(batch->pages, batch->nr_pages, batch->writeable);
+	batch->nr_pages = 0;
+	batch->writeable = false;
+}
+
+static int gntdev_copy(struct gntdev_copy_batch *batch)
+{
+	unsigned int i;
+
+	gnttab_batch_copy(batch->ops, batch->nr_ops);
+	gntdev_put_pages(batch);
+
+	/*
+	 * For each completed op, update the status if the op failed
+	 * and all previous ops for the segment were successful.
+	 */
+	for (i = 0; i < batch->nr_ops; i++) {
+		s16 status = batch->ops[i].status;
+		s16 old_status;
+
+		if (status == GNTST_okay)
+			continue;
+
+		if (__get_user(old_status, batch->status[i]))
+			return -EFAULT;
+
+		if (old_status != GNTST_okay)
+			continue;
+
+		if (__put_user(status, batch->status[i]))
+			return -EFAULT;
+	}
+
+	batch->nr_ops = 0;
+	return 0;
+}
+
+static int gntdev_grant_copy_seg(struct gntdev_copy_batch *batch,
+				 struct gntdev_grant_copy_segment *seg,
+				 s16 __user *status)
+{
+	uint16_t copied = 0;
+
+	/*
+	 * Disallow local -> local copies since there is only space in
+	 * batch->pages for one page per-op and this would be a very
+	 * expensive memcpy().
+	 */
+	if (!(seg->flags & (GNTCOPY_source_gref | GNTCOPY_dest_gref)))
+		return -EINVAL;
+
+	/* Can't cross page if source/dest is a grant ref. */
+	if (seg->flags & GNTCOPY_source_gref) {
+		if (seg->source.foreign.offset + seg->len > XEN_PAGE_SIZE)
+			return -EINVAL;
+	}
+	if (seg->flags & GNTCOPY_dest_gref) {
+		if (seg->dest.foreign.offset + seg->len > XEN_PAGE_SIZE)
+			return -EINVAL;
+	}
+
+	if (put_user(GNTST_okay, status))
+		return -EFAULT;
+
+	while (copied < seg->len) {
+		struct gnttab_copy *op;
+		void __user *virt;
+		size_t len, off;
+		unsigned long gfn;
+		int ret;
+
+		if (batch->nr_ops >= GNTDEV_COPY_BATCH) {
+			ret = gntdev_copy(batch);
+			if (ret < 0)
+				return ret;
+		}
+
+		len = seg->len - copied;
+
+		op = &batch->ops[batch->nr_ops];
+		op->flags = 0;
+
+		if (seg->flags & GNTCOPY_source_gref) {
+			op->source.u.ref = seg->source.foreign.ref;
+			op->source.domid = seg->source.foreign.domid;
+			op->source.offset = seg->source.foreign.offset + copied;
+			op->flags |= GNTCOPY_source_gref;
+		} else {
+			virt = seg->source.virt + copied;
+			off = (unsigned long)virt & ~XEN_PAGE_MASK;
+			len = min(len, (size_t)XEN_PAGE_SIZE - off);
+			batch->writeable = false;
+
+			ret = gntdev_get_page(batch, virt, &gfn);
+			if (ret < 0)
+				return ret;
+
+			op->source.u.gmfn = gfn;
+			op->source.domid = DOMID_SELF;
+			op->source.offset = off;
+		}
+
+		if (seg->flags & GNTCOPY_dest_gref) {
+			op->dest.u.ref = seg->dest.foreign.ref;
+			op->dest.domid = seg->dest.foreign.domid;
+			op->dest.offset = seg->dest.foreign.offset + copied;
+			op->flags |= GNTCOPY_dest_gref;
+		} else {
+			virt = seg->dest.virt + copied;
+			off = (unsigned long)virt & ~XEN_PAGE_MASK;
+			len = min(len, (size_t)XEN_PAGE_SIZE - off);
+			batch->writeable = true;
+
+			ret = gntdev_get_page(batch, virt, &gfn);
+			if (ret < 0)
+				return ret;
+
+			op->dest.u.gmfn = gfn;
+			op->dest.domid = DOMID_SELF;
+			op->dest.offset = off;
+		}
+
+		op->len = len;
+		copied += len;
+
+		batch->status[batch->nr_ops] = status;
+		batch->nr_ops++;
+	}
+
+	return 0;
+}
+
+static long gntdev_ioctl_grant_copy(struct gntdev_priv *priv, void __user *u)
+{
+	struct ioctl_gntdev_grant_copy copy;
+	struct gntdev_copy_batch *batch;
+	unsigned int i;
+	int ret = 0;
+
+	if (copy_from_user(&copy, u, sizeof(copy)))
+		return -EFAULT;
+
+	mutex_lock(&priv->batch_lock);
+	if (!priv->batch) {
+		batch = kmalloc_obj(*batch);
+	} else {
+		batch = priv->batch;
+		priv->batch = batch->next;
+	}
+	mutex_unlock(&priv->batch_lock);
+	if (!batch)
+		return -ENOMEM;
+
+	batch->nr_ops = 0;
+	batch->nr_pages = 0;
+
+	for (i = 0; i < copy.count; i++) {
+		struct gntdev_grant_copy_segment seg;
+
+		if (copy_from_user(&seg, &copy.segments[i], sizeof(seg))) {
+			ret = -EFAULT;
+			gntdev_put_pages(batch);
+			goto out;
+		}
+
+		ret = gntdev_grant_copy_seg(batch, &seg, &copy.segments[i].status);
+		if (ret < 0) {
+			gntdev_put_pages(batch);
+			goto out;
+		}
+
+		cond_resched();
+	}
+	if (batch->nr_ops)
+		ret = gntdev_copy(batch);
+
+ out:
+	mutex_lock(&priv->batch_lock);
+	batch->next = priv->batch;
+	priv->batch = batch;
+	mutex_unlock(&priv->batch_lock);
+
+	return ret;
+}
+
+static long gntdev_ioctl(struct file *flip,
+			 unsigned int cmd, unsigned long arg)
+{
+	struct gntdev_priv *priv = flip->private_data;
+	void __user *ptr = (void __user *)arg;
+
+	switch (cmd) {
+	case IOCTL_GNTDEV_MAP_GRANT_REF:
+		return gntdev_ioctl_map_grant_ref(priv, ptr);
+
+	case IOCTL_GNTDEV_UNMAP_GRANT_REF:
+		return gntdev_ioctl_unmap_grant_ref(priv, ptr);
+
+	case IOCTL_GNTDEV_GET_OFFSET_FOR_VADDR:
+		return gntdev_ioctl_get_offset_for_vaddr(priv, ptr);
+
+	case IOCTL_GNTDEV_SET_UNMAP_NOTIFY:
+		return gntdev_ioctl_notify(priv, ptr);
+
+	case IOCTL_GNTDEV_GRANT_COPY:
+		return gntdev_ioctl_grant_copy(priv, ptr);
+
+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+	case IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS:
+		return gntdev_ioctl_dmabuf_exp_from_refs(priv, ptr);
+
+	case IOCTL_GNTDEV_DMABUF_EXP_WAIT_RELEASED:
+		return gntdev_ioctl_dmabuf_exp_wait_released(priv, ptr);
+
+	case IOCTL_GNTDEV_DMABUF_IMP_TO_REFS:
+		return gntdev_ioctl_dmabuf_imp_to_refs(priv, ptr);
+
+	case IOCTL_GNTDEV_DMABUF_IMP_RELEASE:
+		return gntdev_ioctl_dmabuf_imp_release(priv, ptr);
+#endif
+
+	default:
+		pr_debug("priv %p, unknown cmd %x\n", priv, cmd);
+		return -ENOIOCTLCMD;
+	}
+
+	return 0;
+}
+
+static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
+{
+	struct gntdev_priv *priv = flip->private_data;
+	int index = vma->vm_pgoff;
+	int count = vma_pages(vma);
+	struct gntdev_grant_map *map;
+	int err = -EINVAL;
+
+	if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED))
+		return -EINVAL;
+
+	pr_debug("map %d+%d at %lx (pgoff %lx)\n",
+		 index, count, vma->vm_start, vma->vm_pgoff);
+
+	mutex_lock(&priv->lock);
+	map = gntdev_find_map_index(priv, index, count);
+	if (!map)
+		goto unlock_out;
+	if (!atomic_add_unless(&map->in_use, 1, 1))
+		goto unlock_out;
+
+	refcount_inc(&map->users);
+
+	vma->vm_ops = &gntdev_vmops;
+
+	vm_flags_set(vma, VM_DONTEXPAND | VM_DONTDUMP | VM_MIXEDMAP);
+
+	if (xen_pv_domain())
+		vm_flags_set(vma, VM_DONTCOPY);
+
+	vma->vm_private_data = map;
+	if (map->flags) {
+		if ((vma->vm_flags & VM_WRITE) &&
+				(map->flags & GNTMAP_readonly))
+			goto out_unlock_put;
+	} else {
+		map->flags = GNTMAP_host_map;
+		if (!(vma->vm_flags & VM_WRITE))
+			map->flags |= GNTMAP_readonly;
+	}
+
+	map->pages_vm_start = vma->vm_start;
+
+	if (xen_pv_domain()) {
+		err = mmu_interval_notifier_insert_locked(
+			&map->notifier, vma->vm_mm, vma->vm_start,
+			vma->vm_end - vma->vm_start, &gntdev_mmu_ops);
+		if (err)
+			goto out_unlock_put;
+
+		map->notifier_init = true;
+	}
+	mutex_unlock(&priv->lock);
+
+	if (xen_pv_domain()) {
+		/*
+		 * gntdev takes the address of the PTE in find_grant_ptes() and
+		 * passes it to the hypervisor in gntdev_map_grant_pages(). The
+		 * purpose of the notifier is to prevent the hypervisor pointer
+		 * to the PTE from going stale.
+		 *
+		 * Since this vma's mappings can't be touched without the
+		 * mmap_lock, and we are holding it now, there is no need for
+		 * the notifier_range locking pattern.
+		 */
+		mmu_interval_read_begin(&map->notifier);
+
+		err = apply_to_page_range(vma->vm_mm, vma->vm_start,
+					  vma->vm_end - vma->vm_start,
+					  find_grant_ptes, map);
+		if (err) {
+			pr_warn("find_grant_ptes() failure.\n");
+			goto out_put_map;
+		}
+	}
+
+	err = gntdev_map_grant_pages(map);
+	if (err)
+		goto out_put_map;
+
+	if (!xen_pv_domain()) {
+		err = vm_map_pages_zero(vma, map->pages, map->count);
+		if (err)
+			goto out_put_map;
+	}
+
+	return 0;
+
+unlock_out:
+	mutex_unlock(&priv->lock);
+	return err;
+
+out_unlock_put:
+	mutex_unlock(&priv->lock);
+out_put_map:
+	if (xen_pv_domain())
+		unmap_grant_pages(map, 0, map->count);
+	gntdev_put_map(priv, map);
+	return err;
+}
+
+static const struct file_operations gntdev_fops = {
+	.owner = THIS_MODULE,
+	.open = gntdev_open,
+	.release = gntdev_release,
+	.mmap = gntdev_mmap,
+	.unlocked_ioctl = gntdev_ioctl
+};
+
+static struct miscdevice gntdev_miscdev = {
+	.minor        = MISC_DYNAMIC_MINOR,
+	.name         = "xen/gntdev",
+	.fops         = &gntdev_fops,
+};
+
+/* ------------------------------------------------------------------ */
+
+static int __init gntdev_init(void)
+{
+	int err;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	err = misc_register(&gntdev_miscdev);
+	if (err != 0) {
+		pr_err("Could not register gntdev device\n");
+		return err;
+	}
+	return 0;
+}
+
+static void __exit gntdev_exit(void)
+{
+	misc_deregister(&gntdev_miscdev);
+}
+
+module_init(gntdev_init);
+module_exit(gntdev_exit);
+
+/* ------------------------------------------------------------------ */
diff --git a/drivers/xen/grant-dma-iommu.c b/drivers/xen/grant-dma-iommu.c
new file mode 100644
index 000000000..0965e2dd4
--- /dev/null
+++ b/drivers/xen/grant-dma-iommu.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Stub IOMMU driver which does nothing.
+ * The main purpose of it being present is to reuse generic IOMMU device tree
+ * bindings by Xen grant DMA-mapping layer.
+ *
+ * Copyright (C) 2022 EPAM Systems Inc.
+ */
+
+#include <linux/iommu.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct grant_dma_iommu_device {
+	struct device *dev;
+	struct iommu_device iommu;
+};
+
+static struct iommu_device *grant_dma_iommu_probe_device(struct device *dev)
+{
+	return ERR_PTR(-ENODEV);
+}
+
+/* Nothing is really needed here except a dummy probe_device callback */
+static const struct iommu_ops grant_dma_iommu_ops = {
+	.probe_device = grant_dma_iommu_probe_device,
+};
+
+static const struct of_device_id grant_dma_iommu_of_match[] = {
+	{ .compatible = "xen,grant-dma" },
+	{ },
+};
+
+static int grant_dma_iommu_probe(struct platform_device *pdev)
+{
+	struct grant_dma_iommu_device *mmu;
+	int ret;
+
+	mmu = devm_kzalloc(&pdev->dev, sizeof(*mmu), GFP_KERNEL);
+	if (!mmu)
+		return -ENOMEM;
+
+	mmu->dev = &pdev->dev;
+
+	ret = iommu_device_register(&mmu->iommu, &grant_dma_iommu_ops, &pdev->dev);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, mmu);
+
+	return 0;
+}
+
+static void grant_dma_iommu_remove(struct platform_device *pdev)
+{
+	struct grant_dma_iommu_device *mmu = platform_get_drvdata(pdev);
+
+	platform_set_drvdata(pdev, NULL);
+	iommu_device_unregister(&mmu->iommu);
+}
+
+static struct platform_driver grant_dma_iommu_driver = {
+	.driver = {
+		.name = "grant-dma-iommu",
+		.of_match_table = grant_dma_iommu_of_match,
+	},
+	.probe = grant_dma_iommu_probe,
+	.remove = grant_dma_iommu_remove,
+};
+
+static int __init grant_dma_iommu_init(void)
+{
+	struct device_node *iommu_np;
+
+	iommu_np = of_find_matching_node(NULL, grant_dma_iommu_of_match);
+	if (!iommu_np)
+		return 0;
+
+	of_node_put(iommu_np);
+
+	return platform_driver_register(&grant_dma_iommu_driver);
+}
+subsys_initcall(grant_dma_iommu_init);
diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
new file mode 100644
index 000000000..2aa1a772a
--- /dev/null
+++ b/drivers/xen/grant-dma-ops.c
@@ -0,0 +1,422 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Xen grant DMA-mapping layer - contains special DMA-mapping routines
+ * for providing grant references as DMA addresses to be used by frontends
+ * (e.g. virtio) in Xen guests
+ *
+ * Copyright (c) 2021, Juergen Gross <jgross@suse.com>
+ */
+
+#include <linux/module.h>
+#include <linux/dma-map-ops.h>
+#include <linux/of.h>
+#include <linux/pci.h>
+#include <linux/pfn.h>
+#include <linux/xarray.h>
+#include <linux/virtio_anchor.h>
+#include <linux/virtio.h>
+#include <xen/xen.h>
+#include <xen/xen-ops.h>
+#include <xen/grant_table.h>
+
+struct xen_grant_dma_data {
+	/* The ID of backend domain */
+	domid_t backend_domid;
+	/* Is device behaving sane? */
+	bool broken;
+};
+
+static DEFINE_XARRAY_FLAGS(xen_grant_dma_devices, XA_FLAGS_LOCK_IRQ);
+
+#define XEN_GRANT_DMA_ADDR_OFF	(1ULL << 63)
+
+static inline dma_addr_t grant_to_dma(grant_ref_t grant)
+{
+	return XEN_GRANT_DMA_ADDR_OFF | ((dma_addr_t)grant << XEN_PAGE_SHIFT);
+}
+
+static inline grant_ref_t dma_to_grant(dma_addr_t dma)
+{
+	return (grant_ref_t)((dma & ~XEN_GRANT_DMA_ADDR_OFF) >> XEN_PAGE_SHIFT);
+}
+
+static struct xen_grant_dma_data *find_xen_grant_dma_data(struct device *dev)
+{
+	struct xen_grant_dma_data *data;
+	unsigned long flags;
+
+	xa_lock_irqsave(&xen_grant_dma_devices, flags);
+	data = xa_load(&xen_grant_dma_devices, (unsigned long)dev);
+	xa_unlock_irqrestore(&xen_grant_dma_devices, flags);
+
+	return data;
+}
+
+static int store_xen_grant_dma_data(struct device *dev,
+				    struct xen_grant_dma_data *data)
+{
+	unsigned long flags;
+	int ret;
+
+	xa_lock_irqsave(&xen_grant_dma_devices, flags);
+	ret = xa_err(__xa_store(&xen_grant_dma_devices, (unsigned long)dev, data,
+			GFP_ATOMIC));
+	xa_unlock_irqrestore(&xen_grant_dma_devices, flags);
+
+	return ret;
+}
+
+/*
+ * DMA ops for Xen frontends (e.g. virtio).
+ *
+ * Used to act as a kind of software IOMMU for Xen guests by using grants as
+ * DMA addresses.
+ * Such a DMA address is formed by using the grant reference as a frame
+ * number and setting the highest address bit (this bit is for the backend
+ * to be able to distinguish it from e.g. a mmio address).
+ */
+static void *xen_grant_dma_alloc(struct device *dev, size_t size,
+				 dma_addr_t *dma_handle, gfp_t gfp,
+				 unsigned long attrs)
+{
+	struct xen_grant_dma_data *data;
+	unsigned int i, n_pages = XEN_PFN_UP(size);
+	unsigned long pfn;
+	grant_ref_t grant;
+	void *ret;
+
+	data = find_xen_grant_dma_data(dev);
+	if (!data)
+		return NULL;
+
+	if (unlikely(data->broken))
+		return NULL;
+
+	ret = alloc_pages_exact(n_pages * XEN_PAGE_SIZE, gfp);
+	if (!ret)
+		return NULL;
+
+	pfn = virt_to_pfn(ret);
+
+	if (gnttab_alloc_grant_reference_seq(n_pages, &grant)) {
+		free_pages_exact(ret, n_pages * XEN_PAGE_SIZE);
+		return NULL;
+	}
+
+	for (i = 0; i < n_pages; i++) {
+		gnttab_grant_foreign_access_ref(grant + i, data->backend_domid,
+				pfn_to_gfn(pfn + i), 0);
+	}
+
+	*dma_handle = grant_to_dma(grant);
+
+	return ret;
+}
+
+static void xen_grant_dma_free(struct device *dev, size_t size, void *vaddr,
+			       dma_addr_t dma_handle, unsigned long attrs)
+{
+	struct xen_grant_dma_data *data;
+	unsigned int i, n_pages = XEN_PFN_UP(size);
+	grant_ref_t grant;
+
+	data = find_xen_grant_dma_data(dev);
+	if (!data)
+		return;
+
+	if (unlikely(data->broken))
+		return;
+
+	grant = dma_to_grant(dma_handle);
+
+	for (i = 0; i < n_pages; i++) {
+		if (unlikely(!gnttab_end_foreign_access_ref(grant + i))) {
+			dev_alert(dev, "Grant still in use by backend domain, disabled for further use\n");
+			data->broken = true;
+			return;
+		}
+	}
+
+	gnttab_free_grant_reference_seq(grant, n_pages);
+
+	free_pages_exact(vaddr, n_pages * XEN_PAGE_SIZE);
+}
+
+static struct page *xen_grant_dma_alloc_pages(struct device *dev, size_t size,
+					      dma_addr_t *dma_handle,
+					      enum dma_data_direction dir,
+					      gfp_t gfp)
+{
+	void *vaddr;
+
+	vaddr = xen_grant_dma_alloc(dev, size, dma_handle, gfp, 0);
+	if (!vaddr)
+		return NULL;
+
+	return virt_to_page(vaddr);
+}
+
+static void xen_grant_dma_free_pages(struct device *dev, size_t size,
+				     struct page *vaddr, dma_addr_t dma_handle,
+				     enum dma_data_direction dir)
+{
+	xen_grant_dma_free(dev, size, page_to_virt(vaddr), dma_handle, 0);
+}
+
+static dma_addr_t xen_grant_dma_map_phys(struct device *dev, phys_addr_t phys,
+					 size_t size,
+					 enum dma_data_direction dir,
+					 unsigned long attrs)
+{
+	struct xen_grant_dma_data *data;
+	unsigned long offset = offset_in_page(phys);
+	unsigned long dma_offset = xen_offset_in_page(offset),
+			pfn_offset = XEN_PFN_DOWN(offset);
+	unsigned int i, n_pages = XEN_PFN_UP(dma_offset + size);
+	grant_ref_t grant;
+	dma_addr_t dma_handle;
+
+	if (unlikely(attrs & DMA_ATTR_MMIO))
+		return DMA_MAPPING_ERROR;
+
+	if (WARN_ON(dir == DMA_NONE))
+		return DMA_MAPPING_ERROR;
+
+	data = find_xen_grant_dma_data(dev);
+	if (!data)
+		return DMA_MAPPING_ERROR;
+
+	if (unlikely(data->broken))
+		return DMA_MAPPING_ERROR;
+
+	if (gnttab_alloc_grant_reference_seq(n_pages, &grant))
+		return DMA_MAPPING_ERROR;
+
+	for (i = 0; i < n_pages; i++) {
+		gnttab_grant_foreign_access_ref(grant + i, data->backend_domid,
+				pfn_to_gfn(page_to_xen_pfn(phys_to_page(phys)) + i + pfn_offset),
+				dir == DMA_TO_DEVICE);
+	}
+
+	dma_handle = grant_to_dma(grant) + dma_offset;
+
+	return dma_handle;
+}
+
+static void xen_grant_dma_unmap_phys(struct device *dev, dma_addr_t dma_handle,
+				     size_t size, enum dma_data_direction dir,
+				     unsigned long attrs)
+{
+	struct xen_grant_dma_data *data;
+	unsigned long dma_offset = xen_offset_in_page(dma_handle);
+	unsigned int i, n_pages = XEN_PFN_UP(dma_offset + size);
+	grant_ref_t grant;
+
+	if (WARN_ON(dir == DMA_NONE))
+		return;
+
+	data = find_xen_grant_dma_data(dev);
+	if (!data)
+		return;
+
+	if (unlikely(data->broken))
+		return;
+
+	grant = dma_to_grant(dma_handle);
+
+	for (i = 0; i < n_pages; i++) {
+		if (unlikely(!gnttab_end_foreign_access_ref(grant + i))) {
+			dev_alert(dev, "Grant still in use by backend domain, disabled for further use\n");
+			data->broken = true;
+			return;
+		}
+	}
+
+	gnttab_free_grant_reference_seq(grant, n_pages);
+}
+
+static void xen_grant_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
+				   int nents, enum dma_data_direction dir,
+				   unsigned long attrs)
+{
+	struct scatterlist *s;
+	unsigned int i;
+
+	if (WARN_ON(dir == DMA_NONE))
+		return;
+
+	for_each_sg(sg, s, nents, i)
+		xen_grant_dma_unmap_phys(dev, s->dma_address, sg_dma_len(s), dir,
+				attrs);
+}
+
+static int xen_grant_dma_map_sg(struct device *dev, struct scatterlist *sg,
+				int nents, enum dma_data_direction dir,
+				unsigned long attrs)
+{
+	struct scatterlist *s;
+	unsigned int i;
+
+	if (WARN_ON(dir == DMA_NONE))
+		return -EINVAL;
+
+	for_each_sg(sg, s, nents, i) {
+		s->dma_address = xen_grant_dma_map_phys(dev, sg_phys(s),
+				s->length, dir, attrs);
+		if (s->dma_address == DMA_MAPPING_ERROR)
+			goto out;
+
+		sg_dma_len(s) = s->length;
+	}
+
+	return nents;
+
+out:
+	xen_grant_dma_unmap_sg(dev, sg, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
+	sg_dma_len(sg) = 0;
+
+	return -EIO;
+}
+
+static int xen_grant_dma_supported(struct device *dev, u64 mask)
+{
+	return mask == DMA_BIT_MASK(64);
+}
+
+static const struct dma_map_ops xen_grant_dma_ops = {
+	.alloc = xen_grant_dma_alloc,
+	.free = xen_grant_dma_free,
+	.alloc_pages_op = xen_grant_dma_alloc_pages,
+	.free_pages = xen_grant_dma_free_pages,
+	.mmap = dma_common_mmap,
+	.get_sgtable = dma_common_get_sgtable,
+	.map_phys = xen_grant_dma_map_phys,
+	.unmap_phys = xen_grant_dma_unmap_phys,
+	.map_sg = xen_grant_dma_map_sg,
+	.unmap_sg = xen_grant_dma_unmap_sg,
+	.dma_supported = xen_grant_dma_supported,
+};
+
+static struct device_node *xen_dt_get_node(struct device *dev)
+{
+	if (dev_is_pci(dev)) {
+		struct pci_dev *pdev = to_pci_dev(dev);
+		struct pci_bus *bus = pdev->bus;
+
+		/* Walk up to the root bus to look for PCI Host controller */
+		while (!pci_is_root_bus(bus))
+			bus = bus->parent;
+
+		if (!bus->bridge->parent)
+			return NULL;
+		return of_node_get(bus->bridge->parent->of_node);
+	}
+
+	return of_node_get(dev->of_node);
+}
+
+static int xen_dt_grant_init_backend_domid(struct device *dev,
+					   struct device_node *np,
+					   domid_t *backend_domid)
+{
+	struct of_phandle_args iommu_spec = {};
+
+	if (dev_is_pci(dev)) {
+		struct pci_dev *pdev = to_pci_dev(dev);
+		u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
+
+		if (of_map_iommu_id(np, rid, &iommu_spec)) {
+			dev_dbg(dev, "Cannot translate ID\n");
+			return -ESRCH;
+		}
+	} else {
+		if (of_parse_phandle_with_args(np, "iommus", "#iommu-cells",
+				0, &iommu_spec)) {
+			dev_dbg(dev, "Cannot parse iommus property\n");
+			return -ESRCH;
+		}
+	}
+
+	if (!of_device_is_compatible(iommu_spec.np, "xen,grant-dma") ||
+			iommu_spec.args_count != 1) {
+		dev_dbg(dev, "Incompatible IOMMU node\n");
+		of_node_put(iommu_spec.np);
+		return -ESRCH;
+	}
+
+	of_node_put(iommu_spec.np);
+
+	/*
+	 * The endpoint ID here means the ID of the domain where the
+	 * corresponding backend is running
+	 */
+	*backend_domid = iommu_spec.args[0];
+
+	return 0;
+}
+
+static int xen_grant_init_backend_domid(struct device *dev,
+					domid_t *backend_domid)
+{
+	struct device_node *np;
+	int ret = -ENODEV;
+
+	np = xen_dt_get_node(dev);
+	if (np) {
+		ret = xen_dt_grant_init_backend_domid(dev, np, backend_domid);
+		of_node_put(np);
+	} else if (!xen_initial_domain() &&
+		   (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT) || xen_pv_domain())) {
+		dev_info(dev, "Using dom0 as backend\n");
+		*backend_domid = 0;
+		ret = 0;
+	}
+
+	return ret;
+}
+
+static void xen_grant_setup_dma_ops(struct device *dev, domid_t backend_domid)
+{
+	struct xen_grant_dma_data *data;
+
+	data = find_xen_grant_dma_data(dev);
+	if (data) {
+		dev_err(dev, "Xen grant DMA data is already created\n");
+		return;
+	}
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		goto err;
+
+	data->backend_domid = backend_domid;
+
+	if (store_xen_grant_dma_data(dev, data)) {
+		dev_err(dev, "Cannot store Xen grant DMA data\n");
+		goto err;
+	}
+
+	dev->dma_ops = &xen_grant_dma_ops;
+
+	return;
+
+err:
+	devm_kfree(dev, data);
+	dev_err(dev, "Cannot set up Xen grant DMA ops, retain platform DMA ops\n");
+}
+
+bool xen_virtio_restricted_mem_acc(struct virtio_device *dev)
+{
+	domid_t backend_domid;
+
+	if (!xen_grant_init_backend_domid(dev->dev.parent, &backend_domid)) {
+		xen_grant_setup_dma_ops(dev->dev.parent, backend_domid);
+		return true;
+	}
+
+	return false;
+}
+
+MODULE_DESCRIPTION("Xen grant DMA-mapping layer");
+MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
new file mode 100644
index 000000000..076c1b0ab
--- /dev/null
+++ b/drivers/xen/grant-table.c
@@ -0,0 +1,1699 @@
+/******************************************************************************
+ * grant_table.c
+ *
+ * Granting foreign access to our memory reservation.
+ *
+ * Copyright (c) 2005-2006, Christopher Clark
+ * Copyright (c) 2004-2005, K A Fraser
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/bitmap.h>
+#include <linux/memblock.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/uaccess.h>
+#include <linux/io.h>
+#include <linux/delay.h>
+#include <linux/hardirq.h>
+#include <linux/workqueue.h>
+#include <linux/ratelimit.h>
+#include <linux/moduleparam.h>
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+#include <linux/dma-mapping.h>
+#endif
+
+#include <xen/xen.h>
+#include <xen/interface/xen.h>
+#include <xen/page.h>
+#include <xen/grant_table.h>
+#include <xen/interface/memory.h>
+#include <xen/hvc-console.h>
+#include <xen/swiotlb-xen.h>
+#include <xen/balloon.h>
+#ifdef CONFIG_X86
+#include <asm/cpuid/api.h>
+#include <asm/xen/cpuid.h>
+#endif
+#include <xen/mem-reservation.h>
+#include <asm/xen/hypercall.h>
+#include <asm/xen/interface.h>
+
+#include <asm/sync_bitops.h>
+
+#define GNTTAB_LIST_END 0xffffffff
+
+static grant_ref_t **gnttab_list;
+static unsigned int nr_grant_frames;
+
+/*
+ * Handling of free grants:
+ *
+ * Free grants are in a simple list anchored in gnttab_free_head. They are
+ * linked by grant ref, the last element contains GNTTAB_LIST_END. The number
+ * of free entries is stored in gnttab_free_count.
+ * Additionally there is a bitmap of free entries anchored in
+ * gnttab_free_bitmap. This is being used for simplifying allocation of
+ * multiple consecutive grants, which is needed e.g. for support of virtio.
+ * gnttab_last_free is used to add free entries of new frames at the end of
+ * the free list.
+ * gnttab_free_tail_ptr specifies the variable which references the start
+ * of consecutive free grants ending with gnttab_last_free. This pointer is
+ * updated in a rather defensive way, in order to avoid performance hits in
+ * hot paths.
+ * All those variables are protected by gnttab_list_lock.
+ */
+static int gnttab_free_count;
+static unsigned int gnttab_size;
+static grant_ref_t gnttab_free_head = GNTTAB_LIST_END;
+static grant_ref_t gnttab_last_free = GNTTAB_LIST_END;
+static grant_ref_t *gnttab_free_tail_ptr;
+static unsigned long *gnttab_free_bitmap;
+static DEFINE_SPINLOCK(gnttab_list_lock);
+
+struct grant_frames xen_auto_xlat_grant_frames;
+static unsigned int xen_gnttab_version;
+module_param_named(version, xen_gnttab_version, uint, 0);
+
+static union {
+	struct grant_entry_v1 *v1;
+	union grant_entry_v2 *v2;
+	void *addr;
+} gnttab_shared;
+
+/*This is a structure of function pointers for grant table*/
+struct gnttab_ops {
+	/*
+	 * Version of the grant interface.
+	 */
+	unsigned int version;
+	/*
+	 * Grant refs per grant frame.
+	 */
+	unsigned int grefs_per_grant_frame;
+	/*
+	 * Mapping a list of frames for storing grant entries. Frames parameter
+	 * is used to store grant table address when grant table being setup,
+	 * nr_gframes is the number of frames to map grant table. Returning
+	 * GNTST_okay means success and negative value means failure.
+	 */
+	int (*map_frames)(xen_pfn_t *frames, unsigned int nr_gframes);
+	/*
+	 * Release a list of frames which are mapped in map_frames for grant
+	 * entry status.
+	 */
+	void (*unmap_frames)(void);
+	/*
+	 * Introducing a valid entry into the grant table, granting the frame of
+	 * this grant entry to domain for accessing. Ref
+	 * parameter is reference of this introduced grant entry, domid is id of
+	 * granted domain, frame is the page frame to be granted, and flags is
+	 * status of the grant entry to be updated.
+	 */
+	void (*update_entry)(grant_ref_t ref, domid_t domid,
+			     unsigned long frame, unsigned flags);
+	/*
+	 * Stop granting a grant entry to domain for accessing. Ref parameter is
+	 * reference of a grant entry whose grant access will be stopped.
+	 * If the grant entry is currently mapped for reading or writing, just
+	 * return failure(==0) directly and don't tear down the grant access.
+	 * Otherwise, stop grant access for this entry and return success(==1).
+	 */
+	int (*end_foreign_access_ref)(grant_ref_t ref);
+	/*
+	 * Read the frame number related to a given grant reference.
+	 */
+	unsigned long (*read_frame)(grant_ref_t ref);
+};
+
+struct unmap_refs_callback_data {
+	struct completion completion;
+	int result;
+};
+
+static const struct gnttab_ops *gnttab_interface;
+
+/* This reflects status of grant entries, so act as a global value. */
+static grant_status_t *grstatus;
+
+static struct gnttab_free_callback *gnttab_free_callback_list;
+
+static int gnttab_expand(unsigned int req_entries);
+
+#define RPP (PAGE_SIZE / sizeof(grant_ref_t))
+#define SPP (PAGE_SIZE / sizeof(grant_status_t))
+
+static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)
+{
+	return &gnttab_list[(entry) / RPP][(entry) % RPP];
+}
+/* This can be used as an l-value */
+#define gnttab_entry(entry) (*__gnttab_entry(entry))
+
+static int get_free_entries(unsigned count)
+{
+	unsigned long flags;
+	int ref, rc = 0;
+	grant_ref_t head;
+
+	spin_lock_irqsave(&gnttab_list_lock, flags);
+
+	if ((gnttab_free_count < count) &&
+	    ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) {
+		spin_unlock_irqrestore(&gnttab_list_lock, flags);
+		return rc;
+	}
+
+	ref = head = gnttab_free_head;
+	gnttab_free_count -= count;
+	while (count--) {
+		bitmap_clear(gnttab_free_bitmap, head, 1);
+		if (gnttab_free_tail_ptr == __gnttab_entry(head))
+			gnttab_free_tail_ptr = &gnttab_free_head;
+		if (count)
+			head = gnttab_entry(head);
+	}
+	gnttab_free_head = gnttab_entry(head);
+	gnttab_entry(head) = GNTTAB_LIST_END;
+
+	if (!gnttab_free_count) {
+		gnttab_last_free = GNTTAB_LIST_END;
+		gnttab_free_tail_ptr = NULL;
+	}
+
+	spin_unlock_irqrestore(&gnttab_list_lock, flags);
+
+	return ref;
+}
+
+static int get_seq_entry_count(void)
+{
+	if (gnttab_last_free == GNTTAB_LIST_END || !gnttab_free_tail_ptr ||
+	    *gnttab_free_tail_ptr == GNTTAB_LIST_END)
+		return 0;
+
+	return gnttab_last_free - *gnttab_free_tail_ptr + 1;
+}
+
+/* Rebuilds the free grant list and tries to find count consecutive entries. */
+static int get_free_seq(unsigned int count)
+{
+	int ret = -ENOSPC;
+	unsigned int from, to;
+	grant_ref_t *last;
+
+	gnttab_free_tail_ptr = &gnttab_free_head;
+	last = &gnttab_free_head;
+
+	for (from = find_first_bit(gnttab_free_bitmap, gnttab_size);
+	     from < gnttab_size;
+	     from = find_next_bit(gnttab_free_bitmap, gnttab_size, to + 1)) {
+		to = find_next_zero_bit(gnttab_free_bitmap, gnttab_size,
+					from + 1);
+		if (ret < 0 && to - from >= count) {
+			ret = from;
+			bitmap_clear(gnttab_free_bitmap, ret, count);
+			from += count;
+			gnttab_free_count -= count;
+			if (from == to)
+				continue;
+		}
+
+		/*
+		 * Recreate the free list in order to have it properly sorted.
+		 * This is needed to make sure that the free tail has the maximum
+		 * possible size.
+		 */
+		while (from < to) {
+			*last = from;
+			last = __gnttab_entry(from);
+			gnttab_last_free = from;
+			from++;
+		}
+		if (to < gnttab_size)
+			gnttab_free_tail_ptr = __gnttab_entry(to - 1);
+	}
+
+	*last = GNTTAB_LIST_END;
+	if (gnttab_last_free != gnttab_size - 1)
+		gnttab_free_tail_ptr = NULL;
+
+	return ret;
+}
+
+static int get_free_entries_seq(unsigned int count)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&gnttab_list_lock, flags);
+
+	if (gnttab_free_count < count) {
+		ret = gnttab_expand(count - gnttab_free_count);
+		if (ret < 0)
+			goto out;
+	}
+
+	if (get_seq_entry_count() < count) {
+		ret = get_free_seq(count);
+		if (ret >= 0)
+			goto out;
+		ret = gnttab_expand(count - get_seq_entry_count());
+		if (ret < 0)
+			goto out;
+	}
+
+	ret = *gnttab_free_tail_ptr;
+	*gnttab_free_tail_ptr = gnttab_entry(ret + count - 1);
+	gnttab_free_count -= count;
+	if (!gnttab_free_count)
+		gnttab_free_tail_ptr = NULL;
+	bitmap_clear(gnttab_free_bitmap, ret, count);
+
+ out:
+	spin_unlock_irqrestore(&gnttab_list_lock, flags);
+
+	return ret;
+}
+
+static void do_free_callbacks(void)
+{
+	struct gnttab_free_callback *callback, *next;
+
+	callback = gnttab_free_callback_list;
+	gnttab_free_callback_list = NULL;
+
+	while (callback != NULL) {
+		next = callback->next;
+		if (gnttab_free_count >= callback->count) {
+			callback->next = NULL;
+			callback->fn(callback->arg);
+		} else {
+			callback->next = gnttab_free_callback_list;
+			gnttab_free_callback_list = callback;
+		}
+		callback = next;
+	}
+}
+
+static inline void check_free_callbacks(void)
+{
+	if (unlikely(gnttab_free_callback_list))
+		do_free_callbacks();
+}
+
+static void put_free_entry_locked(grant_ref_t ref)
+{
+	if (unlikely(ref < GNTTAB_NR_RESERVED_ENTRIES))
+		return;
+
+	gnttab_entry(ref) = gnttab_free_head;
+	gnttab_free_head = ref;
+	if (!gnttab_free_count)
+		gnttab_last_free = ref;
+	if (gnttab_free_tail_ptr == &gnttab_free_head)
+		gnttab_free_tail_ptr = __gnttab_entry(ref);
+	gnttab_free_count++;
+	bitmap_set(gnttab_free_bitmap, ref, 1);
+}
+
+static void put_free_entry(grant_ref_t ref)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&gnttab_list_lock, flags);
+	put_free_entry_locked(ref);
+	check_free_callbacks();
+	spin_unlock_irqrestore(&gnttab_list_lock, flags);
+}
+
+static void gnttab_set_free(unsigned int start, unsigned int n)
+{
+	unsigned int i;
+
+	for (i = start; i < start + n - 1; i++)
+		gnttab_entry(i) = i + 1;
+
+	gnttab_entry(i) = GNTTAB_LIST_END;
+	if (!gnttab_free_count) {
+		gnttab_free_head = start;
+		gnttab_free_tail_ptr = &gnttab_free_head;
+	} else {
+		gnttab_entry(gnttab_last_free) = start;
+	}
+	gnttab_free_count += n;
+	gnttab_last_free = i;
+
+	bitmap_set(gnttab_free_bitmap, start, n);
+}
+
+/*
+ * Following applies to gnttab_update_entry_v1 and gnttab_update_entry_v2.
+ * Introducing a valid entry into the grant table:
+ *  1. Write ent->domid.
+ *  2. Write ent->frame: Frame to which access is permitted.
+ *  3. Write memory barrier (WMB).
+ *  4. Write ent->flags, inc. valid type.
+ */
+static void gnttab_update_entry_v1(grant_ref_t ref, domid_t domid,
+				   unsigned long frame, unsigned flags)
+{
+	gnttab_shared.v1[ref].domid = domid;
+	gnttab_shared.v1[ref].frame = frame;
+	wmb();
+	gnttab_shared.v1[ref].flags = flags;
+}
+
+static void gnttab_update_entry_v2(grant_ref_t ref, domid_t domid,
+				   unsigned long frame, unsigned int flags)
+{
+	gnttab_shared.v2[ref].hdr.domid = domid;
+	gnttab_shared.v2[ref].full_page.frame = frame;
+	wmb();	/* Hypervisor concurrent accesses. */
+	gnttab_shared.v2[ref].hdr.flags = GTF_permit_access | flags;
+}
+
+/*
+ * Public grant-issuing interface functions
+ */
+void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
+				     unsigned long frame, int readonly)
+{
+	gnttab_interface->update_entry(ref, domid, frame,
+			   GTF_permit_access | (readonly ? GTF_readonly : 0));
+}
+EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref);
+
+int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
+				int readonly)
+{
+	int ref;
+
+	ref = get_free_entries(1);
+	if (unlikely(ref < 0))
+		return -ENOSPC;
+
+	gnttab_grant_foreign_access_ref(ref, domid, frame, readonly);
+
+	return ref;
+}
+EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
+
+static int gnttab_end_foreign_access_ref_v1(grant_ref_t ref)
+{
+	u16 *pflags = &gnttab_shared.v1[ref].flags;
+	u16 flags;
+
+	flags = *pflags;
+	do {
+		if (flags & (GTF_reading|GTF_writing))
+			return 0;
+	} while (!sync_try_cmpxchg(pflags, &flags, 0));
+
+	return 1;
+}
+
+static int gnttab_end_foreign_access_ref_v2(grant_ref_t ref)
+{
+	gnttab_shared.v2[ref].hdr.flags = 0;
+	mb();	/* Concurrent access by hypervisor. */
+	if (grstatus[ref] & (GTF_reading|GTF_writing)) {
+		return 0;
+	} else {
+		/*
+		 * The read of grstatus needs to have acquire semantics.
+		 *  On x86, reads already have that, and we just need to
+		 * protect against compiler reorderings.
+		 * On other architectures we may need a full barrier.
+		 */
+#ifdef CONFIG_X86
+		barrier();
+#else
+		mb();
+#endif
+	}
+
+	return 1;
+}
+
+static inline int _gnttab_end_foreign_access_ref(grant_ref_t ref)
+{
+	return gnttab_interface->end_foreign_access_ref(ref);
+}
+
+int gnttab_end_foreign_access_ref(grant_ref_t ref)
+{
+	if (_gnttab_end_foreign_access_ref(ref))
+		return 1;
+	pr_warn("WARNING: g.e. %#x still in use!\n", ref);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);
+
+static unsigned long gnttab_read_frame_v1(grant_ref_t ref)
+{
+	return gnttab_shared.v1[ref].frame;
+}
+
+static unsigned long gnttab_read_frame_v2(grant_ref_t ref)
+{
+	return gnttab_shared.v2[ref].full_page.frame;
+}
+
+struct deferred_entry {
+	struct list_head list;
+	grant_ref_t ref;
+	uint16_t warn_delay;
+	struct page *page;
+};
+static LIST_HEAD(deferred_list);
+static void gnttab_handle_deferred(struct timer_list *);
+static DEFINE_TIMER(deferred_timer, gnttab_handle_deferred);
+
+static atomic64_t deferred_count;
+static atomic64_t leaked_count;
+static unsigned int free_per_iteration = 10;
+module_param(free_per_iteration, uint, 0600);
+
+static void gnttab_handle_deferred(struct timer_list *unused)
+{
+	unsigned int nr = READ_ONCE(free_per_iteration);
+	const bool ignore_limit = nr == 0;
+	struct deferred_entry *first = NULL;
+	unsigned long flags;
+	size_t freed = 0;
+
+	spin_lock_irqsave(&gnttab_list_lock, flags);
+	while ((ignore_limit || nr--) && !list_empty(&deferred_list)) {
+		struct deferred_entry *entry
+			= list_first_entry(&deferred_list,
+					   struct deferred_entry, list);
+
+		if (entry == first)
+			break;
+		list_del(&entry->list);
+		spin_unlock_irqrestore(&gnttab_list_lock, flags);
+		if (_gnttab_end_foreign_access_ref(entry->ref)) {
+			uint64_t ret = atomic64_dec_return(&deferred_count);
+
+			put_free_entry(entry->ref);
+			pr_debug("freeing g.e. %#x (pfn %#lx), %llu remaining\n",
+				 entry->ref, page_to_pfn(entry->page),
+				 (unsigned long long)ret);
+			put_page(entry->page);
+			freed++;
+			kfree(entry);
+			entry = NULL;
+		} else {
+			if (!--entry->warn_delay)
+				pr_info("g.e. %#x still pending\n", entry->ref);
+			if (!first)
+				first = entry;
+		}
+		spin_lock_irqsave(&gnttab_list_lock, flags);
+		if (entry)
+			list_add_tail(&entry->list, &deferred_list);
+	}
+	if (list_empty(&deferred_list))
+		WARN_ON(atomic64_read(&deferred_count));
+	else if (!timer_pending(&deferred_timer)) {
+		deferred_timer.expires = jiffies + HZ;
+		add_timer(&deferred_timer);
+	}
+	spin_unlock_irqrestore(&gnttab_list_lock, flags);
+	pr_debug("Freed %zu references", freed);
+}
+
+static void gnttab_add_deferred(grant_ref_t ref, struct page *page)
+{
+	struct deferred_entry *entry;
+	gfp_t gfp = (in_atomic() || irqs_disabled()) ? GFP_ATOMIC : GFP_KERNEL;
+	uint64_t leaked, deferred;
+
+	entry = kmalloc_obj(*entry, gfp);
+	if (!page) {
+		unsigned long gfn = gnttab_interface->read_frame(ref);
+
+		page = pfn_to_page(gfn_to_pfn(gfn));
+		get_page(page);
+	}
+
+	if (entry) {
+		unsigned long flags;
+
+		entry->ref = ref;
+		entry->page = page;
+		entry->warn_delay = 60;
+		spin_lock_irqsave(&gnttab_list_lock, flags);
+		list_add_tail(&entry->list, &deferred_list);
+		if (!timer_pending(&deferred_timer)) {
+			deferred_timer.expires = jiffies + HZ;
+			add_timer(&deferred_timer);
+		}
+		spin_unlock_irqrestore(&gnttab_list_lock, flags);
+		deferred = atomic64_inc_return(&deferred_count);
+		leaked = atomic64_read(&leaked_count);
+		pr_debug("deferring g.e. %#x (pfn %#lx) (total deferred %llu, total leaked %llu)\n",
+			 ref, page ? page_to_pfn(page) : -1, deferred, leaked);
+	} else {
+		deferred = atomic64_read(&deferred_count);
+		leaked = atomic64_inc_return(&leaked_count);
+		pr_warn("leaking g.e. %#x (pfn %#lx) (total deferred %llu, total leaked %llu)\n",
+			ref, page ? page_to_pfn(page) : -1, deferred, leaked);
+	}
+}
+
+int gnttab_try_end_foreign_access(grant_ref_t ref)
+{
+	int ret = _gnttab_end_foreign_access_ref(ref);
+
+	if (ret)
+		put_free_entry(ref);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_try_end_foreign_access);
+
+void gnttab_end_foreign_access(grant_ref_t ref, struct page *page)
+{
+	if (gnttab_try_end_foreign_access(ref)) {
+		if (page)
+			put_page(page);
+	} else
+		gnttab_add_deferred(ref, page);
+}
+EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);
+
+void gnttab_free_grant_reference(grant_ref_t ref)
+{
+	put_free_entry(ref);
+}
+EXPORT_SYMBOL_GPL(gnttab_free_grant_reference);
+
+void gnttab_free_grant_references(grant_ref_t head)
+{
+	grant_ref_t ref;
+	unsigned long flags;
+
+	spin_lock_irqsave(&gnttab_list_lock, flags);
+	while (head != GNTTAB_LIST_END) {
+		ref = gnttab_entry(head);
+		put_free_entry_locked(head);
+		head = ref;
+	}
+	check_free_callbacks();
+	spin_unlock_irqrestore(&gnttab_list_lock, flags);
+}
+EXPORT_SYMBOL_GPL(gnttab_free_grant_references);
+
+void gnttab_free_grant_reference_seq(grant_ref_t head, unsigned int count)
+{
+	unsigned long flags;
+	unsigned int i;
+
+	spin_lock_irqsave(&gnttab_list_lock, flags);
+	for (i = count; i > 0; i--)
+		put_free_entry_locked(head + i - 1);
+	check_free_callbacks();
+	spin_unlock_irqrestore(&gnttab_list_lock, flags);
+}
+EXPORT_SYMBOL_GPL(gnttab_free_grant_reference_seq);
+
+int gnttab_alloc_grant_references(u16 count, grant_ref_t *head)
+{
+	int h = get_free_entries(count);
+
+	if (h < 0)
+		return -ENOSPC;
+
+	*head = h;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references);
+
+int gnttab_alloc_grant_reference_seq(unsigned int count, grant_ref_t *first)
+{
+	int h;
+
+	if (count == 1)
+		h = get_free_entries(1);
+	else
+		h = get_free_entries_seq(count);
+
+	if (h < 0)
+		return -ENOSPC;
+
+	*first = h;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_alloc_grant_reference_seq);
+
+int gnttab_empty_grant_references(const grant_ref_t *private_head)
+{
+	return (*private_head == GNTTAB_LIST_END);
+}
+EXPORT_SYMBOL_GPL(gnttab_empty_grant_references);
+
+int gnttab_claim_grant_reference(grant_ref_t *private_head)
+{
+	grant_ref_t g = *private_head;
+	if (unlikely(g == GNTTAB_LIST_END))
+		return -ENOSPC;
+	*private_head = gnttab_entry(g);
+	return g;
+}
+EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference);
+
+void gnttab_release_grant_reference(grant_ref_t *private_head,
+				    grant_ref_t release)
+{
+	gnttab_entry(release) = *private_head;
+	*private_head = release;
+}
+EXPORT_SYMBOL_GPL(gnttab_release_grant_reference);
+
+void gnttab_request_free_callback(struct gnttab_free_callback *callback,
+				  void (*fn)(void *), void *arg, u16 count)
+{
+	unsigned long flags;
+	struct gnttab_free_callback *cb;
+
+	spin_lock_irqsave(&gnttab_list_lock, flags);
+
+	/* Check if the callback is already on the list */
+	cb = gnttab_free_callback_list;
+	while (cb) {
+		if (cb == callback)
+			goto out;
+		cb = cb->next;
+	}
+
+	callback->fn = fn;
+	callback->arg = arg;
+	callback->count = count;
+	callback->next = gnttab_free_callback_list;
+	gnttab_free_callback_list = callback;
+	check_free_callbacks();
+out:
+	spin_unlock_irqrestore(&gnttab_list_lock, flags);
+}
+EXPORT_SYMBOL_GPL(gnttab_request_free_callback);
+
+void gnttab_cancel_free_callback(struct gnttab_free_callback *callback)
+{
+	struct gnttab_free_callback **pcb;
+	unsigned long flags;
+
+	spin_lock_irqsave(&gnttab_list_lock, flags);
+	for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) {
+		if (*pcb == callback) {
+			*pcb = callback->next;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&gnttab_list_lock, flags);
+}
+EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback);
+
+static unsigned int gnttab_frames(unsigned int frames, unsigned int align)
+{
+	return (frames * gnttab_interface->grefs_per_grant_frame + align - 1) /
+	       align;
+}
+
+static int grow_gnttab_list(unsigned int more_frames)
+{
+	unsigned int new_nr_grant_frames, extra_entries, i;
+	unsigned int nr_glist_frames, new_nr_glist_frames;
+	unsigned int grefs_per_frame;
+
+	grefs_per_frame = gnttab_interface->grefs_per_grant_frame;
+
+	new_nr_grant_frames = nr_grant_frames + more_frames;
+	extra_entries = more_frames * grefs_per_frame;
+
+	nr_glist_frames = gnttab_frames(nr_grant_frames, RPP);
+	new_nr_glist_frames = gnttab_frames(new_nr_grant_frames, RPP);
+	for (i = nr_glist_frames; i < new_nr_glist_frames; i++) {
+		gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);
+		if (!gnttab_list[i])
+			goto grow_nomem;
+	}
+
+	gnttab_set_free(gnttab_size, extra_entries);
+
+	if (!gnttab_free_tail_ptr)
+		gnttab_free_tail_ptr = __gnttab_entry(gnttab_size);
+
+	nr_grant_frames = new_nr_grant_frames;
+	gnttab_size += extra_entries;
+
+	check_free_callbacks();
+
+	return 0;
+
+grow_nomem:
+	while (i-- > nr_glist_frames)
+		free_page((unsigned long) gnttab_list[i]);
+	return -ENOMEM;
+}
+
+static unsigned int __max_nr_grant_frames(void)
+{
+	struct gnttab_query_size query;
+	int rc;
+
+	query.dom = DOMID_SELF;
+
+	rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1);
+	if ((rc < 0) || (query.status != GNTST_okay))
+		return 4; /* Legacy max supported number of frames */
+
+	return query.max_nr_frames;
+}
+
+unsigned int gnttab_max_grant_frames(void)
+{
+	unsigned int xen_max = __max_nr_grant_frames();
+	static unsigned int boot_max_nr_grant_frames;
+
+	/* First time, initialize it properly. */
+	if (!boot_max_nr_grant_frames)
+		boot_max_nr_grant_frames = __max_nr_grant_frames();
+
+	if (xen_max > boot_max_nr_grant_frames)
+		return boot_max_nr_grant_frames;
+	return xen_max;
+}
+EXPORT_SYMBOL_GPL(gnttab_max_grant_frames);
+
+int gnttab_setup_auto_xlat_frames(phys_addr_t addr)
+{
+	xen_pfn_t *pfn;
+	unsigned int max_nr_gframes = __max_nr_grant_frames();
+	unsigned int i;
+	void *vaddr;
+
+	if (xen_auto_xlat_grant_frames.count)
+		return -EINVAL;
+
+	vaddr = memremap(addr, XEN_PAGE_SIZE * max_nr_gframes, MEMREMAP_WB);
+	if (vaddr == NULL) {
+		pr_warn("Failed to ioremap gnttab share frames (addr=%pa)!\n",
+			&addr);
+		return -ENOMEM;
+	}
+	pfn = kzalloc_objs(pfn[0], max_nr_gframes);
+	if (!pfn) {
+		memunmap(vaddr);
+		return -ENOMEM;
+	}
+	for (i = 0; i < max_nr_gframes; i++)
+		pfn[i] = XEN_PFN_DOWN(addr) + i;
+
+	xen_auto_xlat_grant_frames.vaddr = vaddr;
+	xen_auto_xlat_grant_frames.pfn = pfn;
+	xen_auto_xlat_grant_frames.count = max_nr_gframes;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_setup_auto_xlat_frames);
+
+void gnttab_free_auto_xlat_frames(void)
+{
+	if (!xen_auto_xlat_grant_frames.count)
+		return;
+	kfree(xen_auto_xlat_grant_frames.pfn);
+	memunmap(xen_auto_xlat_grant_frames.vaddr);
+
+	xen_auto_xlat_grant_frames.pfn = NULL;
+	xen_auto_xlat_grant_frames.count = 0;
+	xen_auto_xlat_grant_frames.vaddr = NULL;
+}
+EXPORT_SYMBOL_GPL(gnttab_free_auto_xlat_frames);
+
+int gnttab_pages_set_private(int nr_pages, struct page **pages)
+{
+	int i;
+
+	for (i = 0; i < nr_pages; i++) {
+#if BITS_PER_LONG < 64
+		struct xen_page_foreign *foreign;
+
+		foreign = kzalloc_obj(*foreign);
+		if (!foreign)
+			return -ENOMEM;
+
+		set_page_private(pages[i], (unsigned long)foreign);
+#endif
+		SetPagePrivate(pages[i]);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_pages_set_private);
+
+/**
+ * gnttab_alloc_pages - alloc pages suitable for grant mapping into
+ * @nr_pages: number of pages to alloc
+ * @pages: returns the pages
+ */
+int gnttab_alloc_pages(int nr_pages, struct page **pages)
+{
+	int ret;
+
+	ret = xen_alloc_unpopulated_pages(nr_pages, pages);
+	if (ret < 0)
+		return ret;
+
+	ret = gnttab_pages_set_private(nr_pages, pages);
+	if (ret < 0)
+		gnttab_free_pages(nr_pages, pages);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_alloc_pages);
+
+#ifdef CONFIG_XEN_UNPOPULATED_ALLOC
+static inline void cache_init(struct gnttab_page_cache *cache)
+{
+	cache->pages = NULL;
+}
+
+static inline bool cache_empty(struct gnttab_page_cache *cache)
+{
+	return !cache->pages;
+}
+
+static inline struct page *cache_deq(struct gnttab_page_cache *cache)
+{
+	struct page *page;
+
+	page = cache->pages;
+	cache->pages = page->zone_device_data;
+
+	return page;
+}
+
+static inline void cache_enq(struct gnttab_page_cache *cache, struct page *page)
+{
+	page->zone_device_data = cache->pages;
+	cache->pages = page;
+}
+#else
+static inline void cache_init(struct gnttab_page_cache *cache)
+{
+	INIT_LIST_HEAD(&cache->pages);
+}
+
+static inline bool cache_empty(struct gnttab_page_cache *cache)
+{
+	return list_empty(&cache->pages);
+}
+
+static inline struct page *cache_deq(struct gnttab_page_cache *cache)
+{
+	struct page *page;
+
+	page = list_first_entry(&cache->pages, struct page, lru);
+	list_del(&page->lru);
+
+	return page;
+}
+
+static inline void cache_enq(struct gnttab_page_cache *cache, struct page *page)
+{
+	list_add(&page->lru, &cache->pages);
+}
+#endif
+
+void gnttab_page_cache_init(struct gnttab_page_cache *cache)
+{
+	spin_lock_init(&cache->lock);
+	cache_init(cache);
+	cache->num_pages = 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_page_cache_init);
+
+int gnttab_page_cache_get(struct gnttab_page_cache *cache, struct page **page)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&cache->lock, flags);
+
+	if (cache_empty(cache)) {
+		spin_unlock_irqrestore(&cache->lock, flags);
+		return gnttab_alloc_pages(1, page);
+	}
+
+	page[0] = cache_deq(cache);
+	cache->num_pages--;
+
+	spin_unlock_irqrestore(&cache->lock, flags);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_page_cache_get);
+
+void gnttab_page_cache_put(struct gnttab_page_cache *cache, struct page **page,
+			   unsigned int num)
+{
+	unsigned long flags;
+	unsigned int i;
+
+	spin_lock_irqsave(&cache->lock, flags);
+
+	for (i = 0; i < num; i++)
+		cache_enq(cache, page[i]);
+	cache->num_pages += num;
+
+	spin_unlock_irqrestore(&cache->lock, flags);
+}
+EXPORT_SYMBOL_GPL(gnttab_page_cache_put);
+
+void gnttab_page_cache_shrink(struct gnttab_page_cache *cache, unsigned int num)
+{
+	struct page *page[10];
+	unsigned int i = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&cache->lock, flags);
+
+	while (cache->num_pages > num) {
+		page[i] = cache_deq(cache);
+		cache->num_pages--;
+		if (++i == ARRAY_SIZE(page)) {
+			spin_unlock_irqrestore(&cache->lock, flags);
+			gnttab_free_pages(i, page);
+			i = 0;
+			spin_lock_irqsave(&cache->lock, flags);
+		}
+	}
+
+	spin_unlock_irqrestore(&cache->lock, flags);
+
+	if (i != 0)
+		gnttab_free_pages(i, page);
+}
+EXPORT_SYMBOL_GPL(gnttab_page_cache_shrink);
+
+void gnttab_pages_clear_private(int nr_pages, struct page **pages)
+{
+	int i;
+
+	for (i = 0; i < nr_pages; i++) {
+		if (PagePrivate(pages[i])) {
+#if BITS_PER_LONG < 64
+			kfree((void *)page_private(pages[i]));
+#endif
+			ClearPagePrivate(pages[i]);
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(gnttab_pages_clear_private);
+
+/**
+ * gnttab_free_pages - free pages allocated by gnttab_alloc_pages()
+ * @nr_pages: number of pages to free
+ * @pages: the pages
+ */
+void gnttab_free_pages(int nr_pages, struct page **pages)
+{
+	gnttab_pages_clear_private(nr_pages, pages);
+	xen_free_unpopulated_pages(nr_pages, pages);
+}
+EXPORT_SYMBOL_GPL(gnttab_free_pages);
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+/**
+ * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into
+ * @args: arguments to the function
+ */
+int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args)
+{
+	unsigned long pfn, start_pfn;
+	size_t size;
+	int i, ret;
+
+	if (args->nr_pages < 0 || args->nr_pages > (INT_MAX >> PAGE_SHIFT))
+		return -ENOMEM;
+
+	size = args->nr_pages << PAGE_SHIFT;
+	if (args->coherent)
+		args->vaddr = dma_alloc_coherent(args->dev, size,
+						 &args->dev_bus_addr,
+						 GFP_KERNEL | __GFP_NOWARN);
+	else
+		args->vaddr = dma_alloc_wc(args->dev, size,
+					   &args->dev_bus_addr,
+					   GFP_KERNEL | __GFP_NOWARN);
+	if (!args->vaddr) {
+		pr_debug("Failed to allocate DMA buffer of size %zu\n", size);
+		return -ENOMEM;
+	}
+
+	start_pfn = __phys_to_pfn(args->dev_bus_addr);
+	for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages;
+			pfn++, i++) {
+		struct page *page = pfn_to_page(pfn);
+
+		args->pages[i] = page;
+		args->frames[i] = xen_page_to_gfn(page);
+		xenmem_reservation_scrub_page(page);
+	}
+
+	xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages);
+
+	ret = xenmem_reservation_decrease(args->nr_pages, args->frames);
+	if (ret != args->nr_pages) {
+		pr_debug("Failed to decrease reservation for DMA buffer\n");
+		ret = -EFAULT;
+		goto fail;
+	}
+
+	ret = gnttab_pages_set_private(args->nr_pages, args->pages);
+	if (ret < 0)
+		goto fail;
+
+	return 0;
+
+fail:
+	gnttab_dma_free_pages(args);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_dma_alloc_pages);
+
+/**
+ * gnttab_dma_free_pages - free DMAable pages
+ * @args: arguments to the function
+ */
+int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args)
+{
+	size_t size;
+	int i, ret;
+
+	gnttab_pages_clear_private(args->nr_pages, args->pages);
+
+	for (i = 0; i < args->nr_pages; i++)
+		args->frames[i] = page_to_xen_pfn(args->pages[i]);
+
+	ret = xenmem_reservation_increase(args->nr_pages, args->frames);
+	if (ret != args->nr_pages) {
+		pr_debug("Failed to increase reservation for DMA buffer\n");
+		ret = -EFAULT;
+	} else {
+		ret = 0;
+	}
+
+	xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
+					     args->frames);
+
+	size = args->nr_pages << PAGE_SHIFT;
+	if (args->coherent)
+		dma_free_coherent(args->dev, size,
+				  args->vaddr, args->dev_bus_addr);
+	else
+		dma_free_wc(args->dev, size,
+			    args->vaddr, args->dev_bus_addr);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_dma_free_pages);
+#endif
+
+/* Handling of paged out grant targets (GNTST_eagain) */
+#define MAX_DELAY 256
+static inline void
+gnttab_retry_eagain_gop(unsigned int cmd, void *gop, int16_t *status,
+						const char *func)
+{
+	unsigned delay = 1;
+
+	do {
+		BUG_ON(HYPERVISOR_grant_table_op(cmd, gop, 1));
+		if (*status == GNTST_eagain)
+			msleep(delay++);
+	} while ((*status == GNTST_eagain) && (delay < MAX_DELAY));
+
+	if (delay >= MAX_DELAY) {
+		pr_err("%s: %s eagain grant\n", func, current->comm);
+		*status = GNTST_bad_page;
+	}
+}
+
+void gnttab_batch_map(struct gnttab_map_grant_ref *batch, unsigned count)
+{
+	struct gnttab_map_grant_ref *op;
+
+	if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, batch, count))
+		BUG();
+	for (op = batch; op < batch + count; op++)
+		if (op->status == GNTST_eagain)
+			gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, op,
+						&op->status, __func__);
+}
+EXPORT_SYMBOL_GPL(gnttab_batch_map);
+
+void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count)
+{
+	struct gnttab_copy *op;
+
+	if (HYPERVISOR_grant_table_op(GNTTABOP_copy, batch, count))
+		BUG();
+	for (op = batch; op < batch + count; op++)
+		if (op->status == GNTST_eagain)
+			gnttab_retry_eagain_gop(GNTTABOP_copy, op,
+						&op->status, __func__);
+}
+EXPORT_SYMBOL_GPL(gnttab_batch_copy);
+
+void gnttab_foreach_grant_in_range(struct page *page,
+				   unsigned int offset,
+				   unsigned int len,
+				   xen_grant_fn_t fn,
+				   void *data)
+{
+	unsigned int goffset;
+	unsigned int glen;
+	unsigned long xen_pfn;
+
+	len = min(PAGE_SIZE - offset, len);
+	goffset = xen_offset_in_page(offset);
+
+	xen_pfn = page_to_xen_pfn(page) + XEN_PFN_DOWN(offset);
+
+	while (len) {
+		glen = min_t(unsigned int, XEN_PAGE_SIZE - goffset, len);
+		fn(pfn_to_gfn(xen_pfn), goffset, glen, data);
+
+		goffset = 0;
+		xen_pfn++;
+		len -= glen;
+	}
+}
+EXPORT_SYMBOL_GPL(gnttab_foreach_grant_in_range);
+
+void gnttab_foreach_grant(struct page **pages,
+			  unsigned int nr_grefs,
+			  xen_grant_fn_t fn,
+			  void *data)
+{
+	unsigned int goffset = 0;
+	unsigned long xen_pfn = 0;
+	unsigned int i;
+
+	for (i = 0; i < nr_grefs; i++) {
+		if ((i % XEN_PFN_PER_PAGE) == 0) {
+			xen_pfn = page_to_xen_pfn(pages[i / XEN_PFN_PER_PAGE]);
+			goffset = 0;
+		}
+
+		fn(pfn_to_gfn(xen_pfn), goffset, XEN_PAGE_SIZE, data);
+
+		goffset += XEN_PAGE_SIZE;
+		xen_pfn++;
+	}
+}
+
+int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
+		    struct gnttab_map_grant_ref *kmap_ops,
+		    struct page **pages, unsigned int count)
+{
+	int i, ret;
+
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map_ops, count);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < count; i++) {
+		switch (map_ops[i].status) {
+		case GNTST_okay:
+		{
+			struct xen_page_foreign *foreign;
+
+			SetPageForeign(pages[i]);
+			foreign = xen_page_foreign(pages[i]);
+			foreign->domid = map_ops[i].dom;
+			foreign->gref = map_ops[i].ref;
+			break;
+		}
+
+		case GNTST_no_device_space:
+			pr_warn_ratelimited("maptrack limit reached, can't map all guest pages\n");
+			break;
+
+		case GNTST_eagain:
+			/* Retry eagain maps */
+			gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref,
+						map_ops + i,
+						&map_ops[i].status, __func__);
+			/* Test status in next loop iteration. */
+			i--;
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	return set_foreign_p2m_mapping(map_ops, kmap_ops, pages, count);
+}
+EXPORT_SYMBOL_GPL(gnttab_map_refs);
+
+int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
+		      struct gnttab_unmap_grant_ref *kunmap_ops,
+		      struct page **pages, unsigned int count)
+{
+	unsigned int i;
+	int ret;
+
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < count; i++)
+		ClearPageForeign(pages[i]);
+
+	return clear_foreign_p2m_mapping(unmap_ops, kunmap_ops, pages, count);
+}
+EXPORT_SYMBOL_GPL(gnttab_unmap_refs);
+
+#define GNTTAB_UNMAP_REFS_DELAY 5
+
+static void __gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item);
+
+static void gnttab_unmap_work(struct work_struct *work)
+{
+	struct gntab_unmap_queue_data
+		*unmap_data = container_of(work, 
+					   struct gntab_unmap_queue_data,
+					   gnttab_work.work);
+	if (unmap_data->age != UINT_MAX)
+		unmap_data->age++;
+	__gnttab_unmap_refs_async(unmap_data);
+}
+
+static void __gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item)
+{
+	int ret;
+	int pc;
+
+	for (pc = 0; pc < item->count; pc++) {
+		if (page_count(item->pages[pc]) > 1) {
+			unsigned long delay = GNTTAB_UNMAP_REFS_DELAY * (item->age + 1);
+			schedule_delayed_work(&item->gnttab_work,
+					      msecs_to_jiffies(delay));
+			return;
+		}
+	}
+
+	ret = gnttab_unmap_refs(item->unmap_ops, item->kunmap_ops,
+				item->pages, item->count);
+	item->done(ret, item);
+}
+
+void gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item)
+{
+	INIT_DELAYED_WORK(&item->gnttab_work, gnttab_unmap_work);
+	item->age = 0;
+
+	__gnttab_unmap_refs_async(item);
+}
+EXPORT_SYMBOL_GPL(gnttab_unmap_refs_async);
+
+static void unmap_refs_callback(int result,
+		struct gntab_unmap_queue_data *data)
+{
+	struct unmap_refs_callback_data *d = data->data;
+
+	d->result = result;
+	complete(&d->completion);
+}
+
+int gnttab_unmap_refs_sync(struct gntab_unmap_queue_data *item)
+{
+	struct unmap_refs_callback_data data;
+
+	init_completion(&data.completion);
+	item->data = &data;
+	item->done = &unmap_refs_callback;
+	gnttab_unmap_refs_async(item);
+	wait_for_completion(&data.completion);
+
+	return data.result;
+}
+EXPORT_SYMBOL_GPL(gnttab_unmap_refs_sync);
+
+static unsigned int nr_status_frames(unsigned int nr_grant_frames)
+{
+	return gnttab_frames(nr_grant_frames, SPP);
+}
+
+static int gnttab_map_frames_v1(xen_pfn_t *frames, unsigned int nr_gframes)
+{
+	int rc;
+
+	rc = arch_gnttab_map_shared(frames, nr_gframes,
+				    gnttab_max_grant_frames(),
+				    &gnttab_shared.addr);
+	BUG_ON(rc);
+
+	return 0;
+}
+
+static void gnttab_unmap_frames_v1(void)
+{
+	arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
+}
+
+static int gnttab_map_frames_v2(xen_pfn_t *frames, unsigned int nr_gframes)
+{
+	uint64_t *sframes;
+	unsigned int nr_sframes;
+	struct gnttab_get_status_frames getframes;
+	int rc;
+
+	nr_sframes = nr_status_frames(nr_gframes);
+
+	/* No need for kzalloc as it is initialized in following hypercall
+	 * GNTTABOP_get_status_frames.
+	 */
+	sframes = kmalloc_array(nr_sframes, sizeof(*sframes), GFP_ATOMIC);
+	if (!sframes)
+		return -ENOMEM;
+
+	getframes.dom        = DOMID_SELF;
+	getframes.nr_frames  = nr_sframes;
+	set_xen_guest_handle(getframes.frame_list, sframes);
+
+	rc = HYPERVISOR_grant_table_op(GNTTABOP_get_status_frames,
+				       &getframes, 1);
+	if (rc == -ENOSYS) {
+		kfree(sframes);
+		return -ENOSYS;
+	}
+
+	BUG_ON(rc || getframes.status);
+
+	rc = arch_gnttab_map_status(sframes, nr_sframes,
+				    nr_status_frames(gnttab_max_grant_frames()),
+				    &grstatus);
+	BUG_ON(rc);
+	kfree(sframes);
+
+	rc = arch_gnttab_map_shared(frames, nr_gframes,
+				    gnttab_max_grant_frames(),
+				    &gnttab_shared.addr);
+	BUG_ON(rc);
+
+	return 0;
+}
+
+static void gnttab_unmap_frames_v2(void)
+{
+	arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
+	arch_gnttab_unmap(grstatus, nr_status_frames(nr_grant_frames));
+}
+
+static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
+{
+	struct gnttab_setup_table setup;
+	xen_pfn_t *frames;
+	unsigned int nr_gframes = end_idx + 1;
+	int rc;
+
+	if (!xen_pv_domain()) {
+		struct xen_add_to_physmap xatp;
+		unsigned int i = end_idx;
+		rc = 0;
+		BUG_ON(xen_auto_xlat_grant_frames.count < nr_gframes);
+		/*
+		 * Loop backwards, so that the first hypercall has the largest
+		 * index, ensuring that the table will grow only once.
+		 */
+		do {
+			xatp.domid = DOMID_SELF;
+			xatp.idx = i;
+			xatp.space = XENMAPSPACE_grant_table;
+			xatp.gpfn = xen_auto_xlat_grant_frames.pfn[i];
+			rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
+			if (rc != 0) {
+				pr_warn("grant table add_to_physmap failed, err=%d\n",
+					rc);
+				break;
+			}
+		} while (i-- > start_idx);
+
+		return rc;
+	}
+
+	/* No need for kzalloc as it is initialized in following hypercall
+	 * GNTTABOP_setup_table.
+	 */
+	frames = kmalloc_objs(*frames, nr_gframes, GFP_ATOMIC);
+	if (!frames)
+		return -ENOMEM;
+
+	setup.dom        = DOMID_SELF;
+	setup.nr_frames  = nr_gframes;
+	set_xen_guest_handle(setup.frame_list, frames);
+
+	rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
+	if (rc == -ENOSYS) {
+		kfree(frames);
+		return -ENOSYS;
+	}
+
+	BUG_ON(rc || setup.status);
+
+	rc = gnttab_interface->map_frames(frames, nr_gframes);
+
+	kfree(frames);
+
+	return rc;
+}
+
+static const struct gnttab_ops gnttab_v1_ops = {
+	.version			= 1,
+	.grefs_per_grant_frame		= XEN_PAGE_SIZE /
+					  sizeof(struct grant_entry_v1),
+	.map_frames			= gnttab_map_frames_v1,
+	.unmap_frames			= gnttab_unmap_frames_v1,
+	.update_entry			= gnttab_update_entry_v1,
+	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v1,
+	.read_frame			= gnttab_read_frame_v1,
+};
+
+static const struct gnttab_ops gnttab_v2_ops = {
+	.version			= 2,
+	.grefs_per_grant_frame		= XEN_PAGE_SIZE /
+					  sizeof(union grant_entry_v2),
+	.map_frames			= gnttab_map_frames_v2,
+	.unmap_frames			= gnttab_unmap_frames_v2,
+	.update_entry			= gnttab_update_entry_v2,
+	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v2,
+	.read_frame			= gnttab_read_frame_v2,
+};
+
+static bool gnttab_need_v2(void)
+{
+#ifdef CONFIG_X86
+	uint32_t base, width;
+
+	if (xen_pv_domain()) {
+		base = xen_cpuid_base();
+		if (cpuid_eax(base) < 5)
+			return false;	/* Information not available, use V1. */
+		width = cpuid_ebx(base + 5) &
+			XEN_CPUID_MACHINE_ADDRESS_WIDTH_MASK;
+		return width > 32 + PAGE_SHIFT;
+	}
+#endif
+	return !!(max_possible_pfn >> 32);
+}
+
+static void gnttab_request_version(void)
+{
+	long rc;
+	struct gnttab_set_version gsv;
+
+	if (gnttab_need_v2())
+		gsv.version = 2;
+	else
+		gsv.version = 1;
+
+	/* Boot parameter overrides automatic selection. */
+	if (xen_gnttab_version >= 1 && xen_gnttab_version <= 2)
+		gsv.version = xen_gnttab_version;
+
+	rc = HYPERVISOR_grant_table_op(GNTTABOP_set_version, &gsv, 1);
+	if (rc == 0 && gsv.version == 2)
+		gnttab_interface = &gnttab_v2_ops;
+	else
+		gnttab_interface = &gnttab_v1_ops;
+	pr_info("Grant tables using version %d layout\n",
+		gnttab_interface->version);
+}
+
+static int gnttab_setup(void)
+{
+	unsigned int max_nr_gframes;
+
+	max_nr_gframes = gnttab_max_grant_frames();
+	if (max_nr_gframes < nr_grant_frames)
+		return -ENOSYS;
+
+	if (!xen_pv_domain() && gnttab_shared.addr == NULL) {
+		gnttab_shared.addr = xen_auto_xlat_grant_frames.vaddr;
+		if (gnttab_shared.addr == NULL) {
+			pr_warn("gnttab share frames is not mapped!\n");
+			return -ENOMEM;
+		}
+	}
+	return gnttab_map(0, nr_grant_frames - 1);
+}
+#ifdef CONFIG_HIBERNATE_CALLBACKS
+int gnttab_resume(void)
+{
+	gnttab_request_version();
+	return gnttab_setup();
+}
+
+int gnttab_suspend(void)
+{
+	if (xen_pv_domain())
+		gnttab_interface->unmap_frames();
+	return 0;
+}
+#endif
+
+static int gnttab_expand(unsigned int req_entries)
+{
+	int rc;
+	unsigned int cur, extra;
+
+	cur = nr_grant_frames;
+	extra = ((req_entries + gnttab_interface->grefs_per_grant_frame - 1) /
+		 gnttab_interface->grefs_per_grant_frame);
+	if (cur + extra > gnttab_max_grant_frames()) {
+		pr_warn_ratelimited("xen/grant-table: max_grant_frames reached"
+				    " cur=%u extra=%u limit=%u"
+				    " gnttab_free_count=%u req_entries=%u\n",
+				    cur, extra, gnttab_max_grant_frames(),
+				    gnttab_free_count, req_entries);
+		return -ENOSPC;
+	}
+
+	rc = gnttab_map(cur, cur + extra - 1);
+	if (rc == 0)
+		rc = grow_gnttab_list(extra);
+
+	return rc;
+}
+
+int gnttab_init(void)
+{
+	int i;
+	unsigned long max_nr_grant_frames, max_nr_grefs;
+	unsigned int max_nr_glist_frames, nr_glist_frames;
+	int ret;
+
+	gnttab_request_version();
+	max_nr_grant_frames = gnttab_max_grant_frames();
+	max_nr_grefs = max_nr_grant_frames *
+			gnttab_interface->grefs_per_grant_frame;
+	nr_grant_frames = 1;
+
+	/* Determine the maximum number of frames required for the
+	 * grant reference free list on the current hypervisor.
+	 */
+	max_nr_glist_frames = max_nr_grefs / RPP;
+
+	gnttab_list = kmalloc_objs(grant_ref_t *, max_nr_glist_frames);
+	if (gnttab_list == NULL)
+		return -ENOMEM;
+
+	nr_glist_frames = gnttab_frames(nr_grant_frames, RPP);
+	for (i = 0; i < nr_glist_frames; i++) {
+		gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);
+		if (gnttab_list[i] == NULL) {
+			ret = -ENOMEM;
+			goto ini_nomem;
+		}
+	}
+
+	gnttab_free_bitmap = bitmap_zalloc(max_nr_grefs, GFP_KERNEL);
+	if (!gnttab_free_bitmap) {
+		ret = -ENOMEM;
+		goto ini_nomem;
+	}
+
+	ret = arch_gnttab_init(max_nr_grant_frames,
+			       nr_status_frames(max_nr_grant_frames));
+	if (ret < 0)
+		goto ini_nomem;
+
+	if (gnttab_setup() < 0) {
+		ret = -ENODEV;
+		goto ini_nomem;
+	}
+
+	gnttab_size = nr_grant_frames * gnttab_interface->grefs_per_grant_frame;
+
+	gnttab_set_free(GNTTAB_NR_RESERVED_ENTRIES,
+			gnttab_size - GNTTAB_NR_RESERVED_ENTRIES);
+
+	printk("Grant table initialized\n");
+	return 0;
+
+ ini_nomem:
+	for (i--; i >= 0; i--)
+		free_page((unsigned long)gnttab_list[i]);
+	kfree(gnttab_list);
+	bitmap_free(gnttab_free_bitmap);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_init);
+
+static int __gnttab_init(void)
+{
+	if (!xen_domain())
+		return -ENODEV;
+
+	/* Delay grant-table initialization in the PV on HVM case */
+	if (xen_hvm_domain() && !xen_pvh_domain())
+		return 0;
+
+	return gnttab_init();
+}
+/* Starts after core_initcall so that xen_pvh_gnttab_setup can be called
+ * beforehand to initialize xen_auto_xlat_grant_frames. */
+core_initcall_sync(__gnttab_init);
diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
new file mode 100644
index 000000000..05d7de128
--- /dev/null
+++ b/drivers/xen/manage.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Handle extern requests for shutdown, reboot and sysrq
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/reboot.h>
+#include <linux/sysrq.h>
+#include <linux/stop_machine.h>
+#include <linux/suspend.h>
+#include <linux/freezer.h>
+#include <linux/syscore_ops.h>
+#include <linux/export.h>
+
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/grant_table.h>
+#include <xen/events.h>
+#include <xen/hvc-console.h>
+#include <xen/page.h>
+#include <xen/xen-ops.h>
+
+#include <asm/xen/hypercall.h>
+#include <asm/xen/hypervisor.h>
+
+enum shutdown_state {
+	SHUTDOWN_INVALID = -1,
+	SHUTDOWN_POWEROFF = 0,
+	SHUTDOWN_SUSPEND = 2,
+	/* Code 3 is SHUTDOWN_CRASH, which we don't use because the domain can only
+	   report a crash, not be instructed to crash!
+	   HALT is the same as POWEROFF, as far as we're concerned.  The tools use
+	   the distinction when we return the reason code to them.  */
+	 SHUTDOWN_HALT = 4,
+};
+
+/* Ignore multiple shutdown requests. */
+static enum shutdown_state shutting_down = SHUTDOWN_INVALID;
+
+struct suspend_info {
+	int cancelled;
+};
+
+static RAW_NOTIFIER_HEAD(xen_resume_notifier);
+
+void xen_resume_notifier_register(struct notifier_block *nb)
+{
+	raw_notifier_chain_register(&xen_resume_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(xen_resume_notifier_register);
+
+#ifdef CONFIG_HIBERNATE_CALLBACKS
+static int xen_suspend(void *data)
+{
+	struct suspend_info *si = data;
+	int err;
+
+	BUG_ON(!irqs_disabled());
+
+	err = syscore_suspend();
+	if (err) {
+		pr_err("%s: system core suspend failed: %d\n", __func__, err);
+		return err;
+	}
+
+	gnttab_suspend();
+	xen_manage_runstate_time(-1);
+	xen_arch_pre_suspend();
+
+	si->cancelled = HYPERVISOR_suspend(xen_pv_domain()
+                                           ? virt_to_gfn(xen_start_info)
+                                           : 0);
+
+	xen_arch_post_suspend(si->cancelled);
+	xen_manage_runstate_time(si->cancelled ? 1 : 0);
+	gnttab_resume();
+
+	if (!si->cancelled) {
+		xen_irq_resume();
+		xen_timer_resume();
+	}
+
+	syscore_resume();
+
+	return 0;
+}
+
+static void do_suspend(void)
+{
+	int err;
+	struct suspend_info si;
+
+	shutting_down = SHUTDOWN_SUSPEND;
+
+	if (!mutex_trylock(&system_transition_mutex))
+	{
+		pr_err("%s: failed to take system_transition_mutex\n", __func__);
+		goto out;
+	}
+
+	err = freeze_processes();
+	if (err) {
+		pr_err("%s: freeze processes failed %d\n", __func__, err);
+		goto out_unlock;
+	}
+
+	err = freeze_kernel_threads();
+	if (err) {
+		pr_err("%s: freeze kernel threads failed %d\n", __func__, err);
+		goto out_thaw;
+	}
+
+	err = dpm_suspend_start(PMSG_FREEZE);
+	if (err) {
+		pr_err("%s: dpm_suspend_start %d\n", __func__, err);
+		goto out_resume_end;
+	}
+
+	printk(KERN_DEBUG "suspending xenstore...\n");
+	xs_suspend();
+
+	err = dpm_suspend_end(PMSG_FREEZE);
+	if (err) {
+		pr_err("dpm_suspend_end failed: %d\n", err);
+		si.cancelled = 0;
+		goto out_resume;
+	}
+
+	xen_arch_suspend();
+
+	si.cancelled = 1;
+
+	err = stop_machine(xen_suspend, &si, cpumask_of(0));
+
+	/* Resume console as early as possible. */
+	if (!si.cancelled)
+		xen_console_resume();
+
+	raw_notifier_call_chain(&xen_resume_notifier, 0, NULL);
+
+	xen_arch_resume();
+
+	dpm_resume_start(si.cancelled ? PMSG_THAW : PMSG_RESTORE);
+
+	if (err) {
+		pr_err("failed to start xen_suspend: %d\n", err);
+		si.cancelled = 1;
+	}
+
+out_resume:
+	if (!si.cancelled)
+		xs_resume();
+	else
+		xs_suspend_cancel();
+
+out_resume_end:
+	dpm_resume_end(si.cancelled ? PMSG_THAW : PMSG_RESTORE);
+
+out_thaw:
+	thaw_processes();
+out_unlock:
+	mutex_unlock(&system_transition_mutex);
+out:
+	shutting_down = SHUTDOWN_INVALID;
+}
+#endif	/* CONFIG_HIBERNATE_CALLBACKS */
+
+struct shutdown_handler {
+#define SHUTDOWN_CMD_SIZE 11
+	const char command[SHUTDOWN_CMD_SIZE];
+	bool flag;
+	void (*cb)(void);
+};
+
+static int poweroff_nb(struct notifier_block *cb, unsigned long code, void *unused)
+{
+	switch (code) {
+	case SYS_DOWN:
+	case SYS_HALT:
+	case SYS_POWER_OFF:
+		shutting_down = SHUTDOWN_POWEROFF;
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_DONE;
+}
+static void do_poweroff(void)
+{
+	switch (system_state) {
+	case SYSTEM_BOOTING:
+	case SYSTEM_SCHEDULING:
+		orderly_poweroff(true);
+		break;
+	case SYSTEM_RUNNING:
+		orderly_poweroff(false);
+		break;
+	default:
+		/* Don't do it when we are halting/rebooting. */
+		pr_info("Ignoring Xen toolstack shutdown.\n");
+		break;
+	}
+}
+
+static void do_reboot(void)
+{
+	shutting_down = SHUTDOWN_POWEROFF; /* ? */
+	orderly_reboot();
+}
+
+static const struct shutdown_handler shutdown_handlers[] = {
+	{ "poweroff",	true,	do_poweroff },
+	{ "halt",	false,	do_poweroff },
+	{ "reboot",	true,	do_reboot   },
+#ifdef CONFIG_HIBERNATE_CALLBACKS
+	{ "suspend",	true,	do_suspend  },
+#endif
+};
+
+static void shutdown_handler(struct xenbus_watch *watch,
+			     const char *path, const char *token)
+{
+	char *str;
+	struct xenbus_transaction xbt;
+	int err;
+	int idx;
+
+	if (shutting_down != SHUTDOWN_INVALID)
+		return;
+
+ again:
+	err = xenbus_transaction_start(&xbt);
+	if (err)
+		return;
+
+	str = (char *)xenbus_read(xbt, "control", "shutdown", NULL);
+	/* Ignore read errors and empty reads. */
+	if (XENBUS_IS_ERR_READ(str)) {
+		xenbus_transaction_end(xbt, 1);
+		return;
+	}
+
+	for (idx = 0; idx < ARRAY_SIZE(shutdown_handlers); idx++) {
+		if (strcmp(str, shutdown_handlers[idx].command) == 0)
+			break;
+	}
+
+	/* Only acknowledge commands which we are prepared to handle. */
+	if (idx < ARRAY_SIZE(shutdown_handlers))
+		xenbus_write(xbt, "control", "shutdown", "");
+
+	err = xenbus_transaction_end(xbt, 0);
+	if (err == -EAGAIN) {
+		kfree(str);
+		goto again;
+	}
+
+	if (idx < ARRAY_SIZE(shutdown_handlers)) {
+		shutdown_handlers[idx].cb();
+	} else {
+		pr_info("Ignoring shutdown request: %s\n", str);
+		shutting_down = SHUTDOWN_INVALID;
+	}
+
+	kfree(str);
+}
+
+#ifdef CONFIG_MAGIC_SYSRQ
+static void sysrq_handler(struct xenbus_watch *watch, const char *path,
+			  const char *token)
+{
+	char sysrq_key = '\0';
+	struct xenbus_transaction xbt;
+	int err;
+
+ again:
+	err = xenbus_transaction_start(&xbt);
+	if (err)
+		return;
+	err = xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key);
+	if (err < 0) {
+		/*
+		 * The Xenstore watch fires directly after registering it and
+		 * after a suspend/resume cycle. So ENOENT is no error but
+		 * might happen in those cases. ERANGE is observed when we get
+		 * an empty value (''), this happens when we acknowledge the
+		 * request by writing '\0' below.
+		 */
+		if (err != -ENOENT && err != -ERANGE)
+			pr_err("Error %d reading sysrq code in control/sysrq\n",
+			       err);
+		xenbus_transaction_end(xbt, 1);
+		return;
+	}
+
+	if (sysrq_key != '\0') {
+		err = xenbus_printf(xbt, "control", "sysrq", "%c", '\0');
+		if (err) {
+			pr_err("%s: Error %d writing sysrq in control/sysrq\n",
+			       __func__, err);
+			xenbus_transaction_end(xbt, 1);
+			return;
+		}
+	}
+
+	err = xenbus_transaction_end(xbt, 0);
+	if (err == -EAGAIN)
+		goto again;
+
+	if (sysrq_key != '\0')
+		handle_sysrq(sysrq_key);
+}
+
+static struct xenbus_watch sysrq_watch = {
+	.node = "control/sysrq",
+	.callback = sysrq_handler
+};
+#endif
+
+static struct xenbus_watch shutdown_watch = {
+	.node = "control/shutdown",
+	.callback = shutdown_handler
+};
+
+static struct notifier_block xen_reboot_nb = {
+	.notifier_call = poweroff_nb,
+};
+
+static int setup_shutdown_watcher(void)
+{
+	int err;
+	int idx;
+#define FEATURE_PATH_SIZE (SHUTDOWN_CMD_SIZE + sizeof("feature-"))
+	char node[FEATURE_PATH_SIZE];
+
+	err = register_xenbus_watch(&shutdown_watch);
+	if (err) {
+		pr_err("Failed to set shutdown watcher\n");
+		return err;
+	}
+
+#ifdef CONFIG_MAGIC_SYSRQ
+	err = register_xenbus_watch(&sysrq_watch);
+	if (err) {
+		pr_err("Failed to set sysrq watcher\n");
+		goto err_unregister_shutdown;
+	}
+#endif
+
+	for (idx = 0; idx < ARRAY_SIZE(shutdown_handlers); idx++) {
+		if (!shutdown_handlers[idx].flag)
+			continue;
+		snprintf(node, FEATURE_PATH_SIZE, "feature-%s",
+			 shutdown_handlers[idx].command);
+		err = xenbus_printf(XBT_NIL, "control", node, "%u", 1);
+		if (err) {
+			pr_err("%s: Error %d writing %s\n", __func__,
+				err, node);
+			goto err_remove_features;
+		}
+	}
+
+	return 0;
+
+err_remove_features:
+	while (--idx >= 0) {
+		if (!shutdown_handlers[idx].flag)
+			continue;
+		snprintf(node, FEATURE_PATH_SIZE, "feature-%s",
+			 shutdown_handlers[idx].command);
+		xenbus_rm(XBT_NIL, "control", node);
+	}
+#ifdef CONFIG_MAGIC_SYSRQ
+	unregister_xenbus_watch(&sysrq_watch);
+err_unregister_shutdown:
+#endif
+	unregister_xenbus_watch(&shutdown_watch);
+	return err;
+}
+
+static int shutdown_event(struct notifier_block *notifier,
+			  unsigned long event,
+			  void *data)
+{
+	setup_shutdown_watcher();
+	return NOTIFY_DONE;
+}
+
+int xen_setup_shutdown_event(void)
+{
+	static struct notifier_block xenstore_notifier = {
+		.notifier_call = shutdown_event
+	};
+
+	if (!xen_domain())
+		return -ENODEV;
+	register_xenstore_notifier(&xenstore_notifier);
+	register_reboot_notifier(&xen_reboot_nb);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_setup_shutdown_event);
+
+subsys_initcall(xen_setup_shutdown_event);
diff --git a/drivers/xen/mcelog.c b/drivers/xen/mcelog.c
new file mode 100644
index 000000000..32ab419bb
--- /dev/null
+++ b/drivers/xen/mcelog.c
@@ -0,0 +1,423 @@
+/******************************************************************************
+ * mcelog.c
+ * Driver for receiving and transferring machine check error infomation
+ *
+ * Copyright (c) 2012 Intel Corporation
+ * Author: Liu, Jinsong <jinsong.liu@intel.com>
+ * Author: Jiang, Yunhong <yunhong.jiang@intel.com>
+ * Author: Ke, Liping <liping.ke@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) "xen_mcelog: " fmt
+
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/device.h>
+#include <linux/miscdevice.h>
+#include <linux/uaccess.h>
+#include <linux/capability.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+
+#include <xen/interface/xen.h>
+#include <xen/events.h>
+#include <xen/interface/vcpu.h>
+#include <xen/xen.h>
+#include <asm/xen/hypercall.h>
+#include <asm/xen/hypervisor.h>
+
+static struct mc_info g_mi;
+static struct mcinfo_logical_cpu *g_physinfo __ro_after_init;
+static uint32_t ncpus __ro_after_init;
+
+static DEFINE_MUTEX(mcelog_lock);
+
+static struct xen_mce_log xen_mcelog = {
+	.signature	= XEN_MCE_LOG_SIGNATURE,
+	.len		= XEN_MCE_LOG_LEN,
+	.recordlen	= sizeof(struct xen_mce),
+};
+
+static DEFINE_SPINLOCK(xen_mce_chrdev_state_lock);
+static int xen_mce_chrdev_open_count;	/* #times opened */
+static int xen_mce_chrdev_open_exclu;	/* already open exclusive? */
+
+static DECLARE_WAIT_QUEUE_HEAD(xen_mce_chrdev_wait);
+
+static int xen_mce_chrdev_open(struct inode *inode, struct file *file)
+{
+	spin_lock(&xen_mce_chrdev_state_lock);
+
+	if (xen_mce_chrdev_open_exclu ||
+	    (xen_mce_chrdev_open_count && (file->f_flags & O_EXCL))) {
+		spin_unlock(&xen_mce_chrdev_state_lock);
+
+		return -EBUSY;
+	}
+
+	if (file->f_flags & O_EXCL)
+		xen_mce_chrdev_open_exclu = 1;
+	xen_mce_chrdev_open_count++;
+
+	spin_unlock(&xen_mce_chrdev_state_lock);
+
+	return nonseekable_open(inode, file);
+}
+
+static int xen_mce_chrdev_release(struct inode *inode, struct file *file)
+{
+	spin_lock(&xen_mce_chrdev_state_lock);
+
+	xen_mce_chrdev_open_count--;
+	xen_mce_chrdev_open_exclu = 0;
+
+	spin_unlock(&xen_mce_chrdev_state_lock);
+
+	return 0;
+}
+
+static ssize_t xen_mce_chrdev_read(struct file *filp, char __user *ubuf,
+				size_t usize, loff_t *off)
+{
+	char __user *buf = ubuf;
+	unsigned num;
+	int i, err;
+
+	mutex_lock(&mcelog_lock);
+
+	num = xen_mcelog.next;
+
+	/* Only supports full reads right now */
+	err = -EINVAL;
+	if (*off != 0 || usize < XEN_MCE_LOG_LEN*sizeof(struct xen_mce))
+		goto out;
+
+	err = 0;
+	for (i = 0; i < num; i++) {
+		struct xen_mce *m = &xen_mcelog.entry[i];
+
+		err |= copy_to_user(buf, m, sizeof(*m));
+		buf += sizeof(*m);
+	}
+
+	memset(xen_mcelog.entry, 0, num * sizeof(struct xen_mce));
+	xen_mcelog.next = 0;
+
+	if (err)
+		err = -EFAULT;
+
+out:
+	mutex_unlock(&mcelog_lock);
+
+	return err ? err : buf - ubuf;
+}
+
+static __poll_t xen_mce_chrdev_poll(struct file *file, poll_table *wait)
+{
+	poll_wait(file, &xen_mce_chrdev_wait, wait);
+
+	if (xen_mcelog.next)
+		return EPOLLIN | EPOLLRDNORM;
+
+	return 0;
+}
+
+static long xen_mce_chrdev_ioctl(struct file *f, unsigned int cmd,
+				unsigned long arg)
+{
+	int __user *p = (int __user *)arg;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	switch (cmd) {
+	case MCE_GET_RECORD_LEN:
+		return put_user(sizeof(struct xen_mce), p);
+	case MCE_GET_LOG_LEN:
+		return put_user(XEN_MCE_LOG_LEN, p);
+	case MCE_GETCLEAR_FLAGS: {
+		unsigned flags;
+
+		flags = xchg(&xen_mcelog.flags, 0);
+
+		return put_user(flags, p);
+	}
+	default:
+		return -ENOTTY;
+	}
+}
+
+static const struct file_operations xen_mce_chrdev_ops = {
+	.open			= xen_mce_chrdev_open,
+	.release		= xen_mce_chrdev_release,
+	.read			= xen_mce_chrdev_read,
+	.poll			= xen_mce_chrdev_poll,
+	.unlocked_ioctl		= xen_mce_chrdev_ioctl,
+};
+
+static struct miscdevice xen_mce_chrdev_device __ro_after_init = {
+	MISC_MCELOG_MINOR,
+	"mcelog",
+	&xen_mce_chrdev_ops,
+};
+
+/*
+ * Caller should hold the mcelog_lock
+ */
+static void xen_mce_log(struct xen_mce *mce)
+{
+	unsigned entry;
+
+	entry = xen_mcelog.next;
+
+	/*
+	 * When the buffer fills up discard new entries.
+	 * Assume that the earlier errors are the more
+	 * interesting ones:
+	 */
+	if (entry >= XEN_MCE_LOG_LEN) {
+		set_bit(XEN_MCE_OVERFLOW,
+			(unsigned long *)&xen_mcelog.flags);
+		return;
+	}
+
+	memcpy(xen_mcelog.entry + entry, mce, sizeof(struct xen_mce));
+
+	xen_mcelog.next++;
+}
+
+static int convert_log(struct mc_info *mi)
+{
+	struct mcinfo_common *mic;
+	struct mcinfo_global *mc_global;
+	struct mcinfo_bank *mc_bank;
+	struct xen_mce m;
+	unsigned int i, j;
+
+	mic = NULL;
+	x86_mcinfo_lookup(&mic, mi, MC_TYPE_GLOBAL);
+	if (unlikely(!mic)) {
+		pr_warn("Failed to find global error info\n");
+		return -ENODEV;
+	}
+
+	memset(&m, 0, sizeof(struct xen_mce));
+
+	mc_global = (struct mcinfo_global *)mic;
+	m.mcgstatus = mc_global->mc_gstatus;
+	m.apicid = mc_global->mc_apicid;
+
+	for (i = 0; i < ncpus; i++)
+		if (g_physinfo[i].mc_apicid == m.apicid)
+			break;
+	if (unlikely(i == ncpus)) {
+		pr_warn("Failed to match cpu with apicid %d\n", m.apicid);
+		return -ENODEV;
+	}
+
+	m.socketid = g_physinfo[i].mc_chipid;
+	m.cpu = m.extcpu = g_physinfo[i].mc_cpunr;
+	m.cpuvendor = (__u8)g_physinfo[i].mc_vendor;
+	for (j = 0; j < g_physinfo[i].mc_nmsrvals; ++j)
+		switch (g_physinfo[i].mc_msrvalues[j].reg) {
+		case MSR_IA32_MCG_CAP:
+			m.mcgcap = g_physinfo[i].mc_msrvalues[j].value;
+			break;
+
+		case MSR_PPIN:
+		case MSR_AMD_PPIN:
+			m.ppin = g_physinfo[i].mc_msrvalues[j].value;
+			break;
+		}
+
+	mic = NULL;
+	x86_mcinfo_lookup(&mic, mi, MC_TYPE_BANK);
+	if (unlikely(!mic)) {
+		pr_warn("Fail to find bank error info\n");
+		return -ENODEV;
+	}
+
+	do {
+		if ((!mic) || (mic->size == 0) ||
+		    (mic->type != MC_TYPE_GLOBAL   &&
+		     mic->type != MC_TYPE_BANK     &&
+		     mic->type != MC_TYPE_EXTENDED &&
+		     mic->type != MC_TYPE_RECOVERY))
+			break;
+
+		if (mic->type == MC_TYPE_BANK) {
+			mc_bank = (struct mcinfo_bank *)mic;
+			m.misc = mc_bank->mc_misc;
+			m.status = mc_bank->mc_status;
+			m.addr = mc_bank->mc_addr;
+			m.tsc = mc_bank->mc_tsc;
+			m.bank = mc_bank->mc_bank;
+			m.finished = 1;
+			/*log this record*/
+			xen_mce_log(&m);
+		}
+		mic = x86_mcinfo_next(mic);
+	} while (1);
+
+	return 0;
+}
+
+static int mc_queue_handle(uint32_t flags)
+{
+	struct xen_mc mc_op;
+	int ret = 0;
+
+	mc_op.cmd = XEN_MC_fetch;
+	set_xen_guest_handle(mc_op.u.mc_fetch.data, &g_mi);
+	do {
+		mc_op.u.mc_fetch.flags = flags;
+		ret = HYPERVISOR_mca(&mc_op);
+		if (ret) {
+			pr_err("Failed to fetch %surgent error log\n",
+			       flags == XEN_MC_URGENT ? "" : "non");
+			break;
+		}
+
+		if (mc_op.u.mc_fetch.flags & XEN_MC_NODATA ||
+		    mc_op.u.mc_fetch.flags & XEN_MC_FETCHFAILED)
+			break;
+		else {
+			ret = convert_log(&g_mi);
+			if (ret)
+				pr_warn("Failed to convert this error log, continue acking it anyway\n");
+
+			mc_op.u.mc_fetch.flags = flags | XEN_MC_ACK;
+			ret = HYPERVISOR_mca(&mc_op);
+			if (ret) {
+				pr_err("Failed to ack previous error log\n");
+				break;
+			}
+		}
+	} while (1);
+
+	return ret;
+}
+
+/* virq handler for machine check error info*/
+static void xen_mce_work_fn(struct work_struct *work)
+{
+	int err;
+
+	mutex_lock(&mcelog_lock);
+
+	/* urgent mc_info */
+	err = mc_queue_handle(XEN_MC_URGENT);
+	if (err)
+		pr_err("Failed to handle urgent mc_info queue, continue handling nonurgent mc_info queue anyway\n");
+
+	/* nonurgent mc_info */
+	err = mc_queue_handle(XEN_MC_NONURGENT);
+	if (err)
+		pr_err("Failed to handle nonurgent mc_info queue\n");
+
+	/* wake processes polling /dev/mcelog */
+	wake_up_interruptible(&xen_mce_chrdev_wait);
+
+	mutex_unlock(&mcelog_lock);
+}
+static DECLARE_WORK(xen_mce_work, xen_mce_work_fn);
+
+static irqreturn_t xen_mce_interrupt(int irq, void *dev_id)
+{
+	schedule_work(&xen_mce_work);
+	return IRQ_HANDLED;
+}
+
+static int bind_virq_for_mce(void)
+{
+	int ret;
+	struct xen_mc mc_op;
+
+	memset(&mc_op, 0, sizeof(struct xen_mc));
+
+	/* Fetch physical CPU Numbers */
+	mc_op.cmd = XEN_MC_physcpuinfo;
+	set_xen_guest_handle(mc_op.u.mc_physcpuinfo.info, g_physinfo);
+	ret = HYPERVISOR_mca(&mc_op);
+	if (ret) {
+		pr_err("Failed to get CPU numbers\n");
+		return ret;
+	}
+
+	/* Fetch each CPU Physical Info for later reference*/
+	ncpus = mc_op.u.mc_physcpuinfo.ncpus;
+	g_physinfo = kzalloc_objs(struct mcinfo_logical_cpu, ncpus);
+	if (!g_physinfo)
+		return -ENOMEM;
+	set_xen_guest_handle(mc_op.u.mc_physcpuinfo.info, g_physinfo);
+	ret = HYPERVISOR_mca(&mc_op);
+	if (ret) {
+		pr_err("Failed to get CPU info\n");
+		kfree(g_physinfo);
+		return ret;
+	}
+
+	ret  = bind_virq_to_irqhandler(VIRQ_MCA, 0,
+				       xen_mce_interrupt, 0, "mce", NULL);
+	if (ret < 0) {
+		pr_err("Failed to bind virq\n");
+		kfree(g_physinfo);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int __init xen_late_init_mcelog(void)
+{
+	int ret;
+
+	/* Only DOM0 is responsible for MCE logging */
+	if (!xen_initial_domain())
+		return -ENODEV;
+
+	/* register character device /dev/mcelog for xen mcelog */
+	ret = misc_register(&xen_mce_chrdev_device);
+	if (ret)
+		return ret;
+
+	ret = bind_virq_for_mce();
+	if (ret)
+		goto deregister;
+
+	pr_info("/dev/mcelog registered by Xen\n");
+
+	return 0;
+
+deregister:
+	misc_deregister(&xen_mce_chrdev_device);
+	return ret;
+}
+device_initcall(xen_late_init_mcelog);
diff --git a/drivers/xen/mem-reservation.c b/drivers/xen/mem-reservation.c
new file mode 100644
index 000000000..24648836e
--- /dev/null
+++ b/drivers/xen/mem-reservation.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/******************************************************************************
+ * Xen memory reservation utilities.
+ *
+ * Copyright (c) 2003, B Dragovic
+ * Copyright (c) 2003-2004, M Williamson, K Fraser
+ * Copyright (c) 2005 Dan M. Smith, IBM Corporation
+ * Copyright (c) 2010 Daniel Kiper
+ * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
+ */
+
+#include <asm/xen/hypercall.h>
+
+#include <xen/interface/memory.h>
+#include <xen/mem-reservation.h>
+#include <linux/moduleparam.h>
+
+bool __read_mostly xen_scrub_pages = IS_ENABLED(CONFIG_XEN_SCRUB_PAGES_DEFAULT);
+core_param(xen_scrub_pages, xen_scrub_pages, bool, 0);
+
+/*
+ * Use one extent per PAGE_SIZE to avoid to break down the page into
+ * multiple frame.
+ */
+#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+void __xenmem_reservation_va_mapping_update(unsigned long count,
+					    struct page **pages,
+					    xen_pfn_t *frames)
+{
+	int i;
+
+	for (i = 0; i < count; i++) {
+		struct page *page = pages[i];
+		unsigned long pfn = page_to_pfn(page);
+		int ret;
+
+		BUG_ON(!page);
+
+		/*
+		 * We don't support PV MMU when Linux and Xen is using
+		 * different page granularity.
+		 */
+		BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
+		set_phys_to_machine(pfn, frames[i]);
+
+		ret = HYPERVISOR_update_va_mapping(
+				(unsigned long)__va(pfn << PAGE_SHIFT),
+				mfn_pte(frames[i], PAGE_KERNEL), 0);
+		BUG_ON(ret);
+	}
+}
+EXPORT_SYMBOL_GPL(__xenmem_reservation_va_mapping_update);
+
+void __xenmem_reservation_va_mapping_reset(unsigned long count,
+					   struct page **pages)
+{
+	int i;
+
+	for (i = 0; i < count; i++) {
+		struct page *page = pages[i];
+		unsigned long pfn = page_to_pfn(page);
+		int ret;
+
+		/*
+		 * We don't support PV MMU when Linux and Xen are using
+		 * different page granularity.
+		 */
+		BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
+		ret = HYPERVISOR_update_va_mapping(
+				(unsigned long)__va(pfn << PAGE_SHIFT),
+				__pte_ma(0), 0);
+		BUG_ON(ret);
+
+		__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+	}
+}
+EXPORT_SYMBOL_GPL(__xenmem_reservation_va_mapping_reset);
+#endif /* CONFIG_XEN_HAVE_PVMMU */
+
+/* @frames is an array of PFNs */
+int xenmem_reservation_increase(int count, xen_pfn_t *frames)
+{
+	struct xen_memory_reservation reservation = {
+		.address_bits = 0,
+		.extent_order = EXTENT_ORDER,
+		.domid        = DOMID_SELF
+	};
+
+	/* XENMEM_populate_physmap requires a PFN based on Xen granularity. */
+	set_xen_guest_handle(reservation.extent_start, frames);
+	reservation.nr_extents = count;
+	return HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
+}
+EXPORT_SYMBOL_GPL(xenmem_reservation_increase);
+
+/* @frames is an array of GFNs */
+int xenmem_reservation_decrease(int count, xen_pfn_t *frames)
+{
+	struct xen_memory_reservation reservation = {
+		.address_bits = 0,
+		.extent_order = EXTENT_ORDER,
+		.domid        = DOMID_SELF
+	};
+
+	/* XENMEM_decrease_reservation requires a GFN */
+	set_xen_guest_handle(reservation.extent_start, frames);
+	reservation.nr_extents = count;
+	return HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+}
+EXPORT_SYMBOL_GPL(xenmem_reservation_decrease);
diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c
new file mode 100644
index 000000000..385d2587b
--- /dev/null
+++ b/drivers/xen/pci.c
@@ -0,0 +1,373 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2009, Intel Corporation.
+ *
+ * Author: Weidong Han <weidong.han@intel.com>
+ */
+
+#include <linux/pci.h>
+#include <linux/acpi.h>
+#include <linux/pci-acpi.h>
+#include <xen/pci.h>
+#include <xen/xen.h>
+#include <xen/interface/physdev.h>
+#include <xen/interface/xen.h>
+
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+#include "../pci/pci.h"
+#ifdef CONFIG_PCI_MMCONFIG
+#include <asm/pci_x86.h>
+
+static int xen_mcfg_late(void);
+#endif
+
+static bool __read_mostly pci_seg_supported = true;
+
+static int xen_add_device(struct device *dev)
+{
+	int r;
+	struct pci_dev *pci_dev = to_pci_dev(dev);
+#ifdef CONFIG_PCI_IOV
+	struct pci_dev *physfn = pci_dev->physfn;
+#endif
+#ifdef CONFIG_PCI_MMCONFIG
+	static bool pci_mcfg_reserved = false;
+	/*
+	 * Reserve MCFG areas in Xen on first invocation due to this being
+	 * potentially called from inside of acpi_init immediately after
+	 * MCFG table has been finally parsed.
+	 */
+	if (!pci_mcfg_reserved) {
+		xen_mcfg_late();
+		pci_mcfg_reserved = true;
+	}
+#endif
+
+	if (pci_domain_nr(pci_dev->bus) >> 16) {
+		/*
+		 * The hypercall interface is limited to 16bit PCI segment
+		 * values, do not attempt to register devices with Xen in
+		 * segments greater or equal than 0x10000.
+		 */
+		dev_info(dev,
+			 "not registering with Xen: invalid PCI segment\n");
+		return 0;
+	}
+
+	if (pci_seg_supported) {
+		DEFINE_RAW_FLEX(struct physdev_pci_device_add, add, optarr, 1);
+
+		add->seg = pci_domain_nr(pci_dev->bus);
+		add->bus = pci_dev->bus->number;
+		add->devfn = pci_dev->devfn;
+
+#ifdef CONFIG_ACPI
+		acpi_handle handle;
+#endif
+
+#ifdef CONFIG_PCI_IOV
+		if (pci_dev->is_virtfn) {
+			add->flags = XEN_PCI_DEV_VIRTFN;
+			add->physfn.bus = physfn->bus->number;
+			add->physfn.devfn = physfn->devfn;
+		} else
+#endif
+		if (pci_ari_enabled(pci_dev->bus) && PCI_SLOT(pci_dev->devfn))
+			add->flags = XEN_PCI_DEV_EXTFN;
+
+#ifdef CONFIG_ACPI
+		handle = ACPI_HANDLE(&pci_dev->dev);
+#ifdef CONFIG_PCI_IOV
+		if (!handle && pci_dev->is_virtfn)
+			handle = ACPI_HANDLE(physfn->bus->bridge);
+#endif
+		if (!handle) {
+			/*
+			 * This device was not listed in the ACPI name space at
+			 * all. Try to get acpi handle of parent pci bus.
+			 */
+			struct pci_bus *pbus;
+			for (pbus = pci_dev->bus; pbus; pbus = pbus->parent) {
+				handle = acpi_pci_get_bridge_handle(pbus);
+				if (handle)
+					break;
+			}
+		}
+		if (handle) {
+			acpi_status status;
+
+			do {
+				unsigned long long pxm;
+
+				status = acpi_evaluate_integer(handle, "_PXM",
+							       NULL, &pxm);
+				if (ACPI_SUCCESS(status)) {
+					add->optarr[0] = pxm;
+					add->flags |= XEN_PCI_DEV_PXM;
+					break;
+				}
+				status = acpi_get_parent(handle, &handle);
+			} while (ACPI_SUCCESS(status));
+		}
+#endif /* CONFIG_ACPI */
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_add, add);
+		if (r != -ENOSYS)
+			return r;
+		pci_seg_supported = false;
+	}
+
+	if (pci_domain_nr(pci_dev->bus))
+		r = -ENOSYS;
+#ifdef CONFIG_PCI_IOV
+	else if (pci_dev->is_virtfn) {
+		struct physdev_manage_pci_ext manage_pci_ext = {
+			.bus		= pci_dev->bus->number,
+			.devfn		= pci_dev->devfn,
+			.is_virtfn 	= 1,
+			.physfn.bus	= physfn->bus->number,
+			.physfn.devfn	= physfn->devfn,
+		};
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_manage_pci_add_ext,
+			&manage_pci_ext);
+	}
+#endif
+	else if (pci_ari_enabled(pci_dev->bus) && PCI_SLOT(pci_dev->devfn)) {
+		struct physdev_manage_pci_ext manage_pci_ext = {
+			.bus		= pci_dev->bus->number,
+			.devfn		= pci_dev->devfn,
+			.is_extfn	= 1,
+		};
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_manage_pci_add_ext,
+			&manage_pci_ext);
+	} else {
+		struct physdev_manage_pci manage_pci = {
+			.bus	= pci_dev->bus->number,
+			.devfn	= pci_dev->devfn,
+		};
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_manage_pci_add,
+			&manage_pci);
+	}
+
+	return r;
+}
+
+static int xen_remove_device(struct device *dev)
+{
+	int r;
+	struct pci_dev *pci_dev = to_pci_dev(dev);
+
+	if (pci_domain_nr(pci_dev->bus) >> 16) {
+		/*
+		 * The hypercall interface is limited to 16bit PCI segment
+		 * values.
+		 */
+		dev_info(dev,
+			 "not unregistering with Xen: invalid PCI segment\n");
+		return 0;
+	}
+
+	if (pci_seg_supported) {
+		struct physdev_pci_device device = {
+			.seg = pci_domain_nr(pci_dev->bus),
+			.bus = pci_dev->bus->number,
+			.devfn = pci_dev->devfn
+		};
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_remove,
+					  &device);
+	} else if (pci_domain_nr(pci_dev->bus))
+		r = -ENOSYS;
+	else {
+		struct physdev_manage_pci manage_pci = {
+			.bus = pci_dev->bus->number,
+			.devfn = pci_dev->devfn
+		};
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_manage_pci_remove,
+					  &manage_pci);
+	}
+
+	return r;
+}
+
+int xen_reset_device(const struct pci_dev *dev)
+{
+	struct pci_device_reset device = {
+		.dev.seg = pci_domain_nr(dev->bus),
+		.dev.bus = dev->bus->number,
+		.dev.devfn = dev->devfn,
+		.flags = PCI_DEVICE_RESET_FLR,
+	};
+
+	if (pci_domain_nr(dev->bus) >> 16) {
+		/*
+		 * The hypercall interface is limited to 16bit PCI segment
+		 * values.
+		 */
+		dev_info(&dev->dev,
+			 "unable to notify Xen of device reset: invalid PCI segment\n");
+		return 0;
+	}
+
+	return HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_reset, &device);
+}
+EXPORT_SYMBOL_GPL(xen_reset_device);
+
+static int xen_pci_notifier(struct notifier_block *nb,
+			    unsigned long action, void *data)
+{
+	struct device *dev = data;
+	int r = 0;
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		r = xen_add_device(dev);
+		break;
+	case BUS_NOTIFY_DEL_DEVICE:
+		r = xen_remove_device(dev);
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+	if (r)
+		dev_err(dev, "Failed to %s - passthrough or MSI/MSI-X might fail!\n",
+			action == BUS_NOTIFY_ADD_DEVICE ? "add" :
+			(action == BUS_NOTIFY_DEL_DEVICE ? "delete" : "?"));
+	return NOTIFY_OK;
+}
+
+static struct notifier_block device_nb = {
+	.notifier_call = xen_pci_notifier,
+};
+
+static int __init register_xen_pci_notifier(void)
+{
+	if (!xen_initial_domain())
+		return 0;
+
+	return bus_register_notifier(&pci_bus_type, &device_nb);
+}
+
+arch_initcall(register_xen_pci_notifier);
+
+#ifdef CONFIG_PCI_MMCONFIG
+static int xen_mcfg_late(void)
+{
+	struct pci_mmcfg_region *cfg;
+	int rc;
+
+	if (!xen_initial_domain())
+		return 0;
+
+	if ((pci_probe & PCI_PROBE_MMCONF) == 0)
+		return 0;
+
+	if (list_empty(&pci_mmcfg_list))
+		return 0;
+
+	/* Check whether they are in the right area. */
+	list_for_each_entry(cfg, &pci_mmcfg_list, list) {
+		struct physdev_pci_mmcfg_reserved r;
+
+		r.address = cfg->address;
+		r.segment = cfg->segment;
+		r.start_bus = cfg->start_bus;
+		r.end_bus = cfg->end_bus;
+		r.flags = XEN_PCI_MMCFG_RESERVED;
+
+		rc = HYPERVISOR_physdev_op(PHYSDEVOP_pci_mmcfg_reserved, &r);
+		switch (rc) {
+		case 0:
+		case -ENOSYS:
+			continue;
+
+		default:
+			pr_warn("Failed to report MMCONFIG reservation"
+				" state for %s to hypervisor"
+				" (%d)\n",
+				cfg->name, rc);
+		}
+	}
+	return 0;
+}
+#endif
+
+#ifdef CONFIG_XEN_DOM0
+struct xen_device_domain_owner {
+	domid_t domain;
+	struct pci_dev *dev;
+	struct list_head list;
+};
+
+static DEFINE_SPINLOCK(dev_domain_list_spinlock);
+static LIST_HEAD(dev_domain_list);
+
+static struct xen_device_domain_owner *find_device(struct pci_dev *dev)
+{
+	struct xen_device_domain_owner *owner;
+
+	list_for_each_entry(owner, &dev_domain_list, list) {
+		if (owner->dev == dev)
+			return owner;
+	}
+	return NULL;
+}
+
+int xen_find_device_domain_owner(struct pci_dev *dev)
+{
+	struct xen_device_domain_owner *owner;
+	int domain = -ENODEV;
+
+	spin_lock(&dev_domain_list_spinlock);
+	owner = find_device(dev);
+	if (owner)
+		domain = owner->domain;
+	spin_unlock(&dev_domain_list_spinlock);
+	return domain;
+}
+EXPORT_SYMBOL_GPL(xen_find_device_domain_owner);
+
+int xen_register_device_domain_owner(struct pci_dev *dev, uint16_t domain)
+{
+	struct xen_device_domain_owner *owner;
+
+	owner = kzalloc_obj(struct xen_device_domain_owner);
+	if (!owner)
+		return -ENODEV;
+
+	spin_lock(&dev_domain_list_spinlock);
+	if (find_device(dev)) {
+		spin_unlock(&dev_domain_list_spinlock);
+		kfree(owner);
+		return -EEXIST;
+	}
+	owner->domain = domain;
+	owner->dev = dev;
+	list_add_tail(&owner->list, &dev_domain_list);
+	spin_unlock(&dev_domain_list_spinlock);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_register_device_domain_owner);
+
+int xen_unregister_device_domain_owner(struct pci_dev *dev)
+{
+	struct xen_device_domain_owner *owner;
+
+	spin_lock(&dev_domain_list_spinlock);
+	owner = find_device(dev);
+	if (!owner) {
+		spin_unlock(&dev_domain_list_spinlock);
+		return -ENODEV;
+	}
+	list_del(&owner->list);
+	spin_unlock(&dev_domain_list_spinlock);
+	kfree(owner);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_unregister_device_domain_owner);
+#endif
diff --git a/drivers/xen/pcpu.c b/drivers/xen/pcpu.c
new file mode 100644
index 000000000..0a20bb7c5
--- /dev/null
+++ b/drivers/xen/pcpu.c
@@ -0,0 +1,425 @@
+/******************************************************************************
+ * pcpu.c
+ * Management physical cpu in dom0, get pcpu info and provide sys interface
+ *
+ * Copyright (c) 2012 Intel Corporation
+ * Author: Liu, Jinsong <jinsong.liu@intel.com>
+ * Author: Jiang, Yunhong <yunhong.jiang@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) "xen_cpu: " fmt
+
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/cpu.h>
+#include <linux/stat.h>
+#include <linux/capability.h>
+
+#include <xen/xen.h>
+#include <xen/acpi.h>
+#include <xen/xenbus.h>
+#include <xen/events.h>
+#include <xen/interface/platform.h>
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+
+#ifdef CONFIG_ACPI
+#include <acpi/processor.h>
+#endif
+
+/*
+ * @cpu_id: Xen physical cpu logic number
+ * @flags: Xen physical cpu status flag
+ * - XEN_PCPU_FLAGS_ONLINE: cpu is online
+ * - XEN_PCPU_FLAGS_INVALID: cpu is not present
+ */
+struct pcpu {
+	struct list_head list;
+	struct device dev;
+	uint32_t cpu_id;
+	uint32_t acpi_id;
+	uint32_t flags;
+};
+
+static const struct bus_type xen_pcpu_subsys = {
+	.name = "xen_cpu",
+	.dev_name = "xen_cpu",
+};
+
+static DEFINE_MUTEX(xen_pcpu_lock);
+
+static LIST_HEAD(xen_pcpus);
+
+static int xen_pcpu_down(uint32_t cpu_id)
+{
+	struct xen_platform_op op = {
+		.cmd			= XENPF_cpu_offline,
+		.interface_version	= XENPF_INTERFACE_VERSION,
+		.u.cpu_ol.cpuid		= cpu_id,
+	};
+
+	return HYPERVISOR_platform_op(&op);
+}
+
+static int xen_pcpu_up(uint32_t cpu_id)
+{
+	struct xen_platform_op op = {
+		.cmd			= XENPF_cpu_online,
+		.interface_version	= XENPF_INTERFACE_VERSION,
+		.u.cpu_ol.cpuid		= cpu_id,
+	};
+
+	return HYPERVISOR_platform_op(&op);
+}
+
+static ssize_t online_show(struct device *dev,
+			   struct device_attribute *attr,
+			   char *buf)
+{
+	struct pcpu *cpu = container_of(dev, struct pcpu, dev);
+
+	return sprintf(buf, "%u\n", !!(cpu->flags & XEN_PCPU_FLAGS_ONLINE));
+}
+
+static ssize_t online_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct pcpu *pcpu = container_of(dev, struct pcpu, dev);
+	unsigned long long val;
+	ssize_t ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (kstrtoull(buf, 0, &val) < 0)
+		return -EINVAL;
+
+	switch (val) {
+	case 0:
+		ret = xen_pcpu_down(pcpu->cpu_id);
+		break;
+	case 1:
+		ret = xen_pcpu_up(pcpu->cpu_id);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	if (ret >= 0)
+		ret = count;
+	return ret;
+}
+static DEVICE_ATTR_RW(online);
+
+static struct attribute *pcpu_dev_attrs[] = {
+	&dev_attr_online.attr,
+	NULL
+};
+
+static umode_t pcpu_dev_is_visible(struct kobject *kobj,
+				   struct attribute *attr, int idx)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	/*
+	 * Xen never offline cpu0 due to several restrictions
+	 * and assumptions. This basically doesn't add a sys control
+	 * to user, one cannot attempt to offline BSP.
+	 */
+	return dev->id ? attr->mode : 0;
+}
+
+static const struct attribute_group pcpu_dev_group = {
+	.attrs = pcpu_dev_attrs,
+	.is_visible = pcpu_dev_is_visible,
+};
+
+static const struct attribute_group *pcpu_dev_groups[] = {
+	&pcpu_dev_group,
+	NULL
+};
+
+static bool xen_pcpu_online(uint32_t flags)
+{
+	return !!(flags & XEN_PCPU_FLAGS_ONLINE);
+}
+
+static void pcpu_online_status(struct xenpf_pcpuinfo *info,
+			       struct pcpu *pcpu)
+{
+	if (xen_pcpu_online(info->flags) &&
+	   !xen_pcpu_online(pcpu->flags)) {
+		/* the pcpu is onlined */
+		pcpu->flags |= XEN_PCPU_FLAGS_ONLINE;
+		kobject_uevent(&pcpu->dev.kobj, KOBJ_ONLINE);
+	} else if (!xen_pcpu_online(info->flags) &&
+		    xen_pcpu_online(pcpu->flags)) {
+		/* The pcpu is offlined */
+		pcpu->flags &= ~XEN_PCPU_FLAGS_ONLINE;
+		kobject_uevent(&pcpu->dev.kobj, KOBJ_OFFLINE);
+	}
+}
+
+static struct pcpu *get_pcpu(uint32_t cpu_id)
+{
+	struct pcpu *pcpu;
+
+	list_for_each_entry(pcpu, &xen_pcpus, list) {
+		if (pcpu->cpu_id == cpu_id)
+			return pcpu;
+	}
+
+	return NULL;
+}
+
+static void pcpu_release(struct device *dev)
+{
+	struct pcpu *pcpu = container_of(dev, struct pcpu, dev);
+
+	list_del(&pcpu->list);
+	kfree(pcpu);
+}
+
+static void unregister_and_remove_pcpu(struct pcpu *pcpu)
+{
+	struct device *dev;
+
+	if (!pcpu)
+		return;
+
+	dev = &pcpu->dev;
+	/* pcpu remove would be implicitly done */
+	device_unregister(dev);
+}
+
+static int register_pcpu(struct pcpu *pcpu)
+{
+	struct device *dev;
+	int err = -EINVAL;
+
+	if (!pcpu)
+		return err;
+
+	dev = &pcpu->dev;
+	dev->bus = &xen_pcpu_subsys;
+	dev->id = pcpu->cpu_id;
+	dev->release = pcpu_release;
+	dev->groups = pcpu_dev_groups;
+
+	err = device_register(dev);
+	if (err) {
+		put_device(dev);
+		return err;
+	}
+
+	return 0;
+}
+
+static struct pcpu *create_and_register_pcpu(struct xenpf_pcpuinfo *info)
+{
+	struct pcpu *pcpu;
+	int err;
+
+	if (info->flags & XEN_PCPU_FLAGS_INVALID)
+		return ERR_PTR(-ENODEV);
+
+	pcpu = kzalloc_obj(struct pcpu);
+	if (!pcpu)
+		return ERR_PTR(-ENOMEM);
+
+	INIT_LIST_HEAD(&pcpu->list);
+	pcpu->cpu_id = info->xen_cpuid;
+	pcpu->acpi_id = info->acpi_id;
+	pcpu->flags = info->flags;
+
+	/* Need hold on xen_pcpu_lock before pcpu list manipulations */
+	list_add_tail(&pcpu->list, &xen_pcpus);
+
+	err = register_pcpu(pcpu);
+	if (err) {
+		pr_warn("Failed to register pcpu%u\n", info->xen_cpuid);
+		return ERR_PTR(-ENOENT);
+	}
+
+	return pcpu;
+}
+
+/*
+ * Caller should hold the xen_pcpu_lock
+ */
+static int sync_pcpu(uint32_t cpu, uint32_t *max_cpu)
+{
+	int ret;
+	struct pcpu *pcpu = NULL;
+	struct xenpf_pcpuinfo *info;
+	struct xen_platform_op op = {
+		.cmd                   = XENPF_get_cpuinfo,
+		.interface_version     = XENPF_INTERFACE_VERSION,
+		.u.pcpu_info.xen_cpuid = cpu,
+	};
+
+	ret = HYPERVISOR_platform_op(&op);
+	if (ret)
+		return ret;
+
+	info = &op.u.pcpu_info;
+	if (max_cpu)
+		*max_cpu = info->max_present;
+
+	pcpu = get_pcpu(cpu);
+
+	/*
+	 * Only those at cpu present map has its sys interface.
+	 */
+	if (info->flags & XEN_PCPU_FLAGS_INVALID) {
+		unregister_and_remove_pcpu(pcpu);
+		return 0;
+	}
+
+	if (!pcpu) {
+		pcpu = create_and_register_pcpu(info);
+		if (IS_ERR_OR_NULL(pcpu))
+			return -ENODEV;
+	} else
+		pcpu_online_status(info, pcpu);
+
+	return 0;
+}
+
+/*
+ * Sync dom0's pcpu information with xen hypervisor's
+ */
+static int xen_sync_pcpus(void)
+{
+	/*
+	 * Boot cpu always have cpu_id 0 in xen
+	 */
+	uint32_t cpu = 0, max_cpu = 0;
+	int err = 0;
+	struct pcpu *pcpu, *tmp;
+
+	mutex_lock(&xen_pcpu_lock);
+
+	while (!err && (cpu <= max_cpu)) {
+		err = sync_pcpu(cpu, &max_cpu);
+		cpu++;
+	}
+
+	if (err)
+		list_for_each_entry_safe(pcpu, tmp, &xen_pcpus, list)
+			unregister_and_remove_pcpu(pcpu);
+
+	mutex_unlock(&xen_pcpu_lock);
+
+	return err;
+}
+
+static void xen_pcpu_work_fn(struct work_struct *work)
+{
+	xen_sync_pcpus();
+}
+static DECLARE_WORK(xen_pcpu_work, xen_pcpu_work_fn);
+
+static irqreturn_t xen_pcpu_interrupt(int irq, void *dev_id)
+{
+	schedule_work(&xen_pcpu_work);
+	return IRQ_HANDLED;
+}
+
+static int __init xen_pcpu_init(void)
+{
+	int irq, ret;
+
+	if (!xen_initial_domain())
+		return -ENODEV;
+
+	irq = bind_virq_to_irqhandler(VIRQ_PCPU_STATE, 0,
+				      xen_pcpu_interrupt, 0,
+				      "xen-pcpu", NULL);
+	if (irq < 0) {
+		pr_warn("Failed to bind pcpu virq\n");
+		return irq;
+	}
+
+	ret = subsys_system_register(&xen_pcpu_subsys, NULL);
+	if (ret) {
+		pr_warn("Failed to register pcpu subsys\n");
+		goto err1;
+	}
+
+	ret = xen_sync_pcpus();
+	if (ret) {
+		pr_warn("Failed to sync pcpu info\n");
+		goto err2;
+	}
+
+	return 0;
+
+err2:
+	bus_unregister(&xen_pcpu_subsys);
+err1:
+	unbind_from_irqhandler(irq, NULL);
+	return ret;
+}
+arch_initcall(xen_pcpu_init);
+
+#ifdef CONFIG_ACPI
+bool __init xen_processor_present(uint32_t acpi_id)
+{
+	const struct pcpu *pcpu;
+	bool online = false;
+
+	mutex_lock(&xen_pcpu_lock);
+	list_for_each_entry(pcpu, &xen_pcpus, list)
+		if (pcpu->acpi_id == acpi_id) {
+			online = pcpu->flags & XEN_PCPU_FLAGS_ONLINE;
+			break;
+		}
+	mutex_unlock(&xen_pcpu_lock);
+
+	return online;
+}
+
+void xen_sanitize_proc_cap_bits(uint32_t *cap)
+{
+	struct xen_platform_op op = {
+		.cmd			= XENPF_set_processor_pminfo,
+		.u.set_pminfo.id	= -1,
+		.u.set_pminfo.type	= XEN_PM_PDC,
+	};
+	u32 buf[3] = { ACPI_PDC_REVISION_ID, 1, *cap };
+	int ret;
+
+	set_xen_guest_handle(op.u.set_pminfo.pdc, buf);
+	ret = HYPERVISOR_platform_op(&op);
+	if (ret)
+		pr_err("sanitize of _PDC buffer bits from Xen failed: %d\n",
+		       ret);
+	else
+		*cap = buf[2];
+}
+#endif
diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c
new file mode 100644
index 000000000..f24382325
--- /dev/null
+++ b/drivers/xen/platform-pci.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/******************************************************************************
+ * platform-pci.c
+ *
+ * Xen platform PCI device driver
+ *
+ * Authors: ssmith@xensource.com and stefano.stabellini@eu.citrix.com
+ *
+ * Copyright (c) 2005, Intel Corporation.
+ * Copyright (c) 2007, XenSource Inc.
+ * Copyright (c) 2010, Citrix
+ */
+
+
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/pci.h>
+
+#include <xen/platform_pci.h>
+#include <xen/grant_table.h>
+#include <xen/xenbus.h>
+#include <xen/events.h>
+#include <xen/hvm.h>
+#include <xen/xen-ops.h>
+
+#define DRV_NAME    "xen-platform-pci"
+
+#define PCI_DEVICE_ID_XEN_PLATFORM_XS61	0x0002
+
+static unsigned long platform_mmio;
+static unsigned long platform_mmio_alloc;
+static unsigned long platform_mmiolen;
+static uint64_t callback_via;
+
+static unsigned long alloc_xen_mmio(unsigned long len)
+{
+	unsigned long addr;
+
+	addr = platform_mmio + platform_mmio_alloc;
+	platform_mmio_alloc += len;
+	BUG_ON(platform_mmio_alloc > platform_mmiolen);
+
+	return addr;
+}
+
+static uint64_t get_callback_via(struct pci_dev *pdev)
+{
+	u8 pin;
+	int irq;
+
+	irq = pdev->irq;
+	if (irq < 16)
+		return irq; /* ISA IRQ */
+
+	pin = pdev->pin;
+
+	/* We don't know the GSI. Specify the PCI INTx line instead. */
+	return ((uint64_t)HVM_PARAM_CALLBACK_TYPE_PCI_INTX <<
+			  HVM_CALLBACK_VIA_TYPE_SHIFT) |
+		((uint64_t)pci_domain_nr(pdev->bus) << 32) |
+		((uint64_t)pdev->bus->number << 16) |
+		((uint64_t)(pdev->devfn & 0xff) << 8) |
+		((uint64_t)(pin - 1) & 3);
+}
+
+static irqreturn_t do_hvm_evtchn_intr(int irq, void *dev_id)
+{
+	return xen_evtchn_do_upcall();
+}
+
+static int xen_allocate_irq(struct pci_dev *pdev)
+{
+	return request_irq(pdev->irq, do_hvm_evtchn_intr,
+			IRQF_NOBALANCING | IRQF_SHARED,
+			"xen-platform-pci", pdev);
+}
+
+static int platform_pci_resume(struct device *dev)
+{
+	int err;
+
+	if (xen_have_vector_callback)
+		return 0;
+
+	err = xen_set_callback_via(callback_via);
+	if (err) {
+		dev_err(dev, "platform_pci_resume failure!\n");
+		return err;
+	}
+	return 0;
+}
+
+static int platform_pci_probe(struct pci_dev *pdev,
+			      const struct pci_device_id *ent)
+{
+	int i, ret;
+	long ioaddr;
+	long mmio_addr, mmio_len;
+	unsigned int max_nr_gframes;
+	unsigned long grant_frames;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	i = pci_enable_device(pdev);
+	if (i)
+		return i;
+
+	ioaddr = pci_resource_start(pdev, 0);
+
+	mmio_addr = pci_resource_start(pdev, 1);
+	mmio_len = pci_resource_len(pdev, 1);
+
+	if (mmio_addr == 0 || ioaddr == 0) {
+		dev_err(&pdev->dev, "no resources found\n");
+		ret = -ENOENT;
+		goto pci_out;
+	}
+
+	ret = pci_request_region(pdev, 1, DRV_NAME);
+	if (ret < 0)
+		goto pci_out;
+
+	ret = pci_request_region(pdev, 0, DRV_NAME);
+	if (ret < 0)
+		goto mem_out;
+
+	platform_mmio = mmio_addr;
+	platform_mmiolen = mmio_len;
+	if (!xen_have_vector_callback) {
+		ret = xen_allocate_irq(pdev);
+		if (ret) {
+			dev_warn(&pdev->dev, "request_irq failed err=%d\n", ret);
+			goto out;
+		}
+		/*
+		 * It doesn't strictly *have* to run on CPU0 but it sure
+		 * as hell better process the event channel ports delivered
+		 * to CPU0.
+		 */
+		irq_set_affinity(pdev->irq, cpumask_of(0));
+
+		callback_via = get_callback_via(pdev);
+		ret = xen_set_callback_via(callback_via);
+		if (ret) {
+			dev_warn(&pdev->dev, "Unable to set the evtchn callback "
+					 "err=%d\n", ret);
+			goto irq_out;
+		}
+	}
+
+	max_nr_gframes = gnttab_max_grant_frames();
+	grant_frames = alloc_xen_mmio(PAGE_SIZE * max_nr_gframes);
+	ret = gnttab_setup_auto_xlat_frames(grant_frames);
+	if (ret)
+		goto irq_out;
+	ret = gnttab_init();
+	if (ret)
+		goto grant_out;
+	return 0;
+grant_out:
+	gnttab_free_auto_xlat_frames();
+irq_out:
+	if (!xen_have_vector_callback)
+		free_irq(pdev->irq, pdev);
+out:
+	pci_release_region(pdev, 0);
+mem_out:
+	pci_release_region(pdev, 1);
+pci_out:
+	pci_disable_device(pdev);
+	return ret;
+}
+
+static const struct pci_device_id platform_pci_tbl[] = {
+	{ PCI_VDEVICE(XEN, PCI_DEVICE_ID_XEN_PLATFORM) },
+	{ PCI_VDEVICE(XEN, PCI_DEVICE_ID_XEN_PLATFORM_XS61) },
+	{ }
+};
+
+static const struct dev_pm_ops platform_pm_ops = {
+	.resume_noirq =   platform_pci_resume,
+};
+
+static struct pci_driver platform_driver = {
+	.name =           DRV_NAME,
+	.probe =          platform_pci_probe,
+	.id_table =       platform_pci_tbl,
+	.driver = {
+		.pm =     &platform_pm_ops,
+	},
+};
+
+builtin_pci_driver(platform_driver);
diff --git a/drivers/xen/privcmd-buf.c b/drivers/xen/privcmd-buf.c
new file mode 100644
index 000000000..4cb66eb54
--- /dev/null
+++ b/drivers/xen/privcmd-buf.c
@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/******************************************************************************
+ * privcmd-buf.c
+ *
+ * Mmap of hypercall buffers.
+ *
+ * Copyright (c) 2018 Juergen Gross
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/miscdevice.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+
+#include "privcmd.h"
+
+MODULE_DESCRIPTION("Xen Mmap of hypercall buffers");
+MODULE_LICENSE("GPL");
+
+struct privcmd_buf_private {
+	struct mutex lock;
+	struct list_head list;
+};
+
+struct privcmd_buf_vma_private {
+	struct privcmd_buf_private *file_priv;
+	struct list_head list;
+	unsigned int users;
+	unsigned int n_pages;
+	struct page *pages[];
+};
+
+static int privcmd_buf_open(struct inode *ino, struct file *file)
+{
+	struct privcmd_buf_private *file_priv;
+
+	file_priv = kzalloc_obj(*file_priv);
+	if (!file_priv)
+		return -ENOMEM;
+
+	mutex_init(&file_priv->lock);
+	INIT_LIST_HEAD(&file_priv->list);
+
+	file->private_data = file_priv;
+
+	return 0;
+}
+
+static void privcmd_buf_vmapriv_free(struct privcmd_buf_vma_private *vma_priv)
+{
+	unsigned int i;
+
+	list_del(&vma_priv->list);
+
+	for (i = 0; i < vma_priv->n_pages; i++)
+		__free_page(vma_priv->pages[i]);
+
+	kfree(vma_priv);
+}
+
+static int privcmd_buf_release(struct inode *ino, struct file *file)
+{
+	struct privcmd_buf_private *file_priv = file->private_data;
+	struct privcmd_buf_vma_private *vma_priv;
+
+	mutex_lock(&file_priv->lock);
+
+	while (!list_empty(&file_priv->list)) {
+		vma_priv = list_first_entry(&file_priv->list,
+					    struct privcmd_buf_vma_private,
+					    list);
+		privcmd_buf_vmapriv_free(vma_priv);
+	}
+
+	mutex_unlock(&file_priv->lock);
+
+	kfree(file_priv);
+
+	return 0;
+}
+
+static void privcmd_buf_vma_open(struct vm_area_struct *vma)
+{
+	struct privcmd_buf_vma_private *vma_priv = vma->vm_private_data;
+
+	if (!vma_priv)
+		return;
+
+	mutex_lock(&vma_priv->file_priv->lock);
+	vma_priv->users++;
+	mutex_unlock(&vma_priv->file_priv->lock);
+}
+
+static void privcmd_buf_vma_close(struct vm_area_struct *vma)
+{
+	struct privcmd_buf_vma_private *vma_priv = vma->vm_private_data;
+	struct privcmd_buf_private *file_priv;
+
+	if (!vma_priv)
+		return;
+
+	file_priv = vma_priv->file_priv;
+
+	mutex_lock(&file_priv->lock);
+
+	vma_priv->users--;
+	if (!vma_priv->users)
+		privcmd_buf_vmapriv_free(vma_priv);
+
+	mutex_unlock(&file_priv->lock);
+}
+
+static vm_fault_t privcmd_buf_vma_fault(struct vm_fault *vmf)
+{
+	pr_debug("fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n",
+		 vmf->vma, vmf->vma->vm_start, vmf->vma->vm_end,
+		 vmf->pgoff, (void *)vmf->address);
+
+	return VM_FAULT_SIGBUS;
+}
+
+static const struct vm_operations_struct privcmd_buf_vm_ops = {
+	.open = privcmd_buf_vma_open,
+	.close = privcmd_buf_vma_close,
+	.fault = privcmd_buf_vma_fault,
+};
+
+static int privcmd_buf_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct privcmd_buf_private *file_priv = file->private_data;
+	struct privcmd_buf_vma_private *vma_priv;
+	unsigned long count = vma_pages(vma);
+	unsigned int i;
+	int ret = 0;
+
+	if (!(vma->vm_flags & VM_SHARED))
+		return -EINVAL;
+
+	vma_priv = kzalloc_flex(*vma_priv, pages, count);
+	if (!vma_priv)
+		return -ENOMEM;
+
+	for (i = 0; i < count; i++) {
+		vma_priv->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO);
+		if (!vma_priv->pages[i])
+			break;
+		vma_priv->n_pages++;
+	}
+
+	mutex_lock(&file_priv->lock);
+
+	vma_priv->file_priv = file_priv;
+	vma_priv->users = 1;
+
+	vm_flags_set(vma, VM_IO | VM_DONTEXPAND);
+	vma->vm_ops = &privcmd_buf_vm_ops;
+	vma->vm_private_data = vma_priv;
+
+	list_add(&vma_priv->list, &file_priv->list);
+
+	if (vma_priv->n_pages != count)
+		ret = -ENOMEM;
+	else
+		ret = vm_map_pages_zero(vma, vma_priv->pages,
+						vma_priv->n_pages);
+
+	if (ret)
+		privcmd_buf_vmapriv_free(vma_priv);
+
+	mutex_unlock(&file_priv->lock);
+
+	return ret;
+}
+
+const struct file_operations xen_privcmdbuf_fops = {
+	.owner = THIS_MODULE,
+	.open = privcmd_buf_open,
+	.release = privcmd_buf_release,
+	.mmap = privcmd_buf_mmap,
+};
+EXPORT_SYMBOL_GPL(xen_privcmdbuf_fops);
+
+struct miscdevice xen_privcmdbuf_dev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "xen/hypercall",
+	.fops = &xen_privcmdbuf_fops,
+};
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
new file mode 100644
index 000000000..7cfc28f1b
--- /dev/null
+++ b/drivers/xen/privcmd.c
@@ -0,0 +1,1785 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/******************************************************************************
+ * privcmd.c
+ *
+ * Interface to privileged domain-0 commands.
+ *
+ * Copyright (c) 2002-2004, K A Fraser, B Dragovic
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/eventfd.h>
+#include <linux/file.h>
+#include <linux/kernel.h>
+#include <linux/kstrtox.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/srcu.h>
+#include <linux/string.h>
+#include <linux/workqueue.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/uaccess.h>
+#include <linux/swap.h>
+#include <linux/highmem.h>
+#include <linux/pagemap.h>
+#include <linux/seq_file.h>
+#include <linux/miscdevice.h>
+#include <linux/moduleparam.h>
+#include <linux/notifier.h>
+#include <linux/security.h>
+#include <linux/virtio_mmio.h>
+#include <linux/wait.h>
+
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+
+#include <xen/xen.h>
+#include <xen/events.h>
+#include <xen/privcmd.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/memory.h>
+#include <xen/interface/hvm/dm_op.h>
+#include <xen/interface/hvm/ioreq.h>
+#include <xen/features.h>
+#include <xen/page.h>
+#include <xen/xen-ops.h>
+#include <xen/balloon.h>
+#include <xen/xenbus.h>
+#ifdef CONFIG_XEN_ACPI
+#include <xen/acpi.h>
+#endif
+
+#include "privcmd.h"
+
+MODULE_DESCRIPTION("Xen hypercall passthrough driver");
+MODULE_LICENSE("GPL");
+
+#define PRIV_VMA_LOCKED ((void *)1)
+
+static unsigned int privcmd_dm_op_max_num = 16;
+module_param_named(dm_op_max_nr_bufs, privcmd_dm_op_max_num, uint, 0644);
+MODULE_PARM_DESC(dm_op_max_nr_bufs,
+		 "Maximum number of buffers per dm_op hypercall");
+
+static unsigned int privcmd_dm_op_buf_max_size = 4096;
+module_param_named(dm_op_buf_max_size, privcmd_dm_op_buf_max_size, uint,
+		   0644);
+MODULE_PARM_DESC(dm_op_buf_max_size,
+		 "Maximum size of a dm_op hypercall buffer");
+
+static bool unrestricted;
+module_param(unrestricted, bool, 0);
+MODULE_PARM_DESC(unrestricted,
+	"Don't restrict hypercalls to target domain if running in a domU");
+
+struct privcmd_data {
+	domid_t domid;
+};
+
+/* DOMID_INVALID implies no restriction */
+static domid_t target_domain = DOMID_INVALID;
+static bool restrict_wait;
+static DECLARE_WAIT_QUEUE_HEAD(restrict_wait_wq);
+
+static int privcmd_vma_range_is_mapped(
+               struct vm_area_struct *vma,
+               unsigned long addr,
+               unsigned long nr_pages);
+
+static long privcmd_ioctl_hypercall(struct file *file, void __user *udata)
+{
+	struct privcmd_data *data = file->private_data;
+	struct privcmd_hypercall hypercall;
+	long ret;
+
+	/* Disallow arbitrary hypercalls if restricted */
+	if (data->domid != DOMID_INVALID)
+		return -EPERM;
+
+	if (copy_from_user(&hypercall, udata, sizeof(hypercall)))
+		return -EFAULT;
+
+	xen_preemptible_hcall_begin();
+	ret = privcmd_call(hypercall.op,
+			   hypercall.arg[0], hypercall.arg[1],
+			   hypercall.arg[2], hypercall.arg[3],
+			   hypercall.arg[4]);
+	xen_preemptible_hcall_end();
+
+	return ret;
+}
+
+static void free_page_list(struct list_head *pages)
+{
+	struct page *p, *n;
+
+	list_for_each_entry_safe(p, n, pages, lru)
+		__free_page(p);
+
+	INIT_LIST_HEAD(pages);
+}
+
+/*
+ * Given an array of items in userspace, return a list of pages
+ * containing the data.  If copying fails, either because of memory
+ * allocation failure or a problem reading user memory, return an
+ * error code; its up to the caller to dispose of any partial list.
+ */
+static int gather_array(struct list_head *pagelist,
+			unsigned nelem, size_t size,
+			const void __user *data)
+{
+	unsigned pageidx;
+	void *pagedata;
+	int ret;
+
+	if (size > PAGE_SIZE)
+		return 0;
+
+	pageidx = PAGE_SIZE;
+	pagedata = NULL;	/* quiet, gcc */
+	while (nelem--) {
+		if (pageidx > PAGE_SIZE-size) {
+			struct page *page = alloc_page(GFP_KERNEL);
+
+			ret = -ENOMEM;
+			if (page == NULL)
+				goto fail;
+
+			pagedata = page_address(page);
+
+			list_add_tail(&page->lru, pagelist);
+			pageidx = 0;
+		}
+
+		ret = -EFAULT;
+		if (copy_from_user(pagedata + pageidx, data, size))
+			goto fail;
+
+		data += size;
+		pageidx += size;
+	}
+
+	ret = 0;
+
+fail:
+	return ret;
+}
+
+/*
+ * Call function "fn" on each element of the array fragmented
+ * over a list of pages.
+ */
+static int traverse_pages(unsigned nelem, size_t size,
+			  struct list_head *pos,
+			  int (*fn)(void *data, void *state),
+			  void *state)
+{
+	void *pagedata;
+	unsigned pageidx;
+	int ret = 0;
+
+	BUG_ON(size > PAGE_SIZE);
+
+	pageidx = PAGE_SIZE;
+	pagedata = NULL;	/* hush, gcc */
+
+	while (nelem--) {
+		if (pageidx > PAGE_SIZE-size) {
+			struct page *page;
+			pos = pos->next;
+			page = list_entry(pos, struct page, lru);
+			pagedata = page_address(page);
+			pageidx = 0;
+		}
+
+		ret = (*fn)(pagedata + pageidx, state);
+		if (ret)
+			break;
+		pageidx += size;
+	}
+
+	return ret;
+}
+
+/*
+ * Similar to traverse_pages, but use each page as a "block" of
+ * data to be processed as one unit.
+ */
+static int traverse_pages_block(unsigned nelem, size_t size,
+				struct list_head *pos,
+				int (*fn)(void *data, int nr, void *state),
+				void *state)
+{
+	void *pagedata;
+	int ret = 0;
+
+	BUG_ON(size > PAGE_SIZE);
+
+	while (nelem) {
+		int nr = (PAGE_SIZE/size);
+		struct page *page;
+		if (nr > nelem)
+			nr = nelem;
+		pos = pos->next;
+		page = list_entry(pos, struct page, lru);
+		pagedata = page_address(page);
+		ret = (*fn)(pagedata, nr, state);
+		if (ret)
+			break;
+		nelem -= nr;
+	}
+
+	return ret;
+}
+
+struct mmap_gfn_state {
+	unsigned long va;
+	struct vm_area_struct *vma;
+	domid_t domain;
+};
+
+static int mmap_gfn_range(void *data, void *state)
+{
+	struct privcmd_mmap_entry *msg = data;
+	struct mmap_gfn_state *st = state;
+	struct vm_area_struct *vma = st->vma;
+	int rc;
+
+	/* Do not allow range to wrap the address space. */
+	if ((msg->npages > (LONG_MAX >> PAGE_SHIFT)) ||
+	    ((unsigned long)(msg->npages << PAGE_SHIFT) >= -st->va))
+		return -EINVAL;
+
+	/* Range chunks must be contiguous in va space. */
+	if ((msg->va != st->va) ||
+	    ((msg->va+(msg->npages<<PAGE_SHIFT)) > vma->vm_end))
+		return -EINVAL;
+
+	rc = xen_remap_domain_gfn_range(vma,
+					msg->va & PAGE_MASK,
+					msg->mfn, msg->npages,
+					vma->vm_page_prot,
+					st->domain, NULL);
+	if (rc < 0)
+		return rc;
+
+	st->va += msg->npages << PAGE_SHIFT;
+
+	return 0;
+}
+
+static long privcmd_ioctl_mmap(struct file *file, void __user *udata)
+{
+	struct privcmd_data *data = file->private_data;
+	struct privcmd_mmap mmapcmd;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	int rc;
+	LIST_HEAD(pagelist);
+	struct mmap_gfn_state state;
+
+	/* We only support privcmd_ioctl_mmap_batch for non-auto-translated. */
+	if (!xen_pv_domain())
+		return -ENOSYS;
+
+	if (copy_from_user(&mmapcmd, udata, sizeof(mmapcmd)))
+		return -EFAULT;
+
+	/* If restriction is in place, check the domid matches */
+	if (data->domid != DOMID_INVALID && data->domid != mmapcmd.dom)
+		return -EPERM;
+
+	rc = gather_array(&pagelist,
+			  mmapcmd.num, sizeof(struct privcmd_mmap_entry),
+			  mmapcmd.entry);
+
+	if (rc || list_empty(&pagelist))
+		goto out;
+
+	mmap_write_lock(mm);
+
+	{
+		struct page *page = list_first_entry(&pagelist,
+						     struct page, lru);
+		struct privcmd_mmap_entry *msg = page_address(page);
+
+		vma = vma_lookup(mm, msg->va);
+		rc = -EINVAL;
+
+		if (!vma || (msg->va != vma->vm_start) || vma->vm_private_data)
+			goto out_up;
+		vma->vm_private_data = PRIV_VMA_LOCKED;
+	}
+
+	state.va = vma->vm_start;
+	state.vma = vma;
+	state.domain = mmapcmd.dom;
+
+	rc = traverse_pages(mmapcmd.num, sizeof(struct privcmd_mmap_entry),
+			    &pagelist,
+			    mmap_gfn_range, &state);
+
+
+out_up:
+	mmap_write_unlock(mm);
+
+out:
+	free_page_list(&pagelist);
+
+	return rc;
+}
+
+struct mmap_batch_state {
+	domid_t domain;
+	unsigned long va;
+	struct vm_area_struct *vma;
+	int index;
+	/* A tristate:
+	 *      0 for no errors
+	 *      1 if at least one error has happened (and no
+	 *          -ENOENT errors have happened)
+	 *      -ENOENT if at least 1 -ENOENT has happened.
+	 */
+	int global_error;
+	int version;
+
+	/* User-space gfn array to store errors in the second pass for V1. */
+	xen_pfn_t __user *user_gfn;
+	/* User-space int array to store errors in the second pass for V2. */
+	int __user *user_err;
+};
+
+/* auto translated dom0 note: if domU being created is PV, then gfn is
+ * mfn(addr on bus). If it's auto xlated, then gfn is pfn (input to HAP).
+ */
+static int mmap_batch_fn(void *data, int nr, void *state)
+{
+	xen_pfn_t *gfnp = data;
+	struct mmap_batch_state *st = state;
+	struct vm_area_struct *vma = st->vma;
+	struct page **pages = vma->vm_private_data;
+	struct page **cur_pages = NULL;
+	int ret;
+
+	if (!xen_pv_domain())
+		cur_pages = &pages[st->index];
+
+	BUG_ON(nr < 0);
+	ret = xen_remap_domain_gfn_array(st->vma, st->va & PAGE_MASK, gfnp, nr,
+					 (int *)gfnp, st->vma->vm_page_prot,
+					 st->domain, cur_pages);
+
+	/* Adjust the global_error? */
+	if (ret != nr) {
+		if (ret == -ENOENT)
+			st->global_error = -ENOENT;
+		else {
+			/* Record that at least one error has happened. */
+			if (st->global_error == 0)
+				st->global_error = 1;
+		}
+	}
+	st->va += XEN_PAGE_SIZE * nr;
+	st->index += nr / XEN_PFN_PER_PAGE;
+
+	return 0;
+}
+
+static int mmap_return_error(int err, struct mmap_batch_state *st)
+{
+	int ret;
+
+	if (st->version == 1) {
+		if (err) {
+			xen_pfn_t gfn;
+
+			ret = get_user(gfn, st->user_gfn);
+			if (ret < 0)
+				return ret;
+			/*
+			 * V1 encodes the error codes in the 32bit top
+			 * nibble of the gfn (with its known
+			 * limitations vis-a-vis 64 bit callers).
+			 */
+			gfn |= (err == -ENOENT) ?
+				PRIVCMD_MMAPBATCH_PAGED_ERROR :
+				PRIVCMD_MMAPBATCH_MFN_ERROR;
+			return __put_user(gfn, st->user_gfn++);
+		} else
+			st->user_gfn++;
+	} else { /* st->version == 2 */
+		if (err)
+			return __put_user(err, st->user_err++);
+		else
+			st->user_err++;
+	}
+
+	return 0;
+}
+
+static int mmap_return_errors(void *data, int nr, void *state)
+{
+	struct mmap_batch_state *st = state;
+	int *errs = data;
+	int i;
+	int ret;
+
+	for (i = 0; i < nr; i++) {
+		ret = mmap_return_error(errs[i], st);
+		if (ret < 0)
+			return ret;
+	}
+	return 0;
+}
+
+/* Allocate pfns that are then mapped with gfns from foreign domid. Update
+ * the vma with the page info to use later.
+ * Returns: 0 if success, otherwise -errno
+ */
+static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs)
+{
+	int rc;
+	struct page **pages;
+
+	pages = kvzalloc_objs(pages[0], numpgs);
+	if (pages == NULL)
+		return -ENOMEM;
+
+	rc = xen_alloc_unpopulated_pages(numpgs, pages);
+	if (rc != 0) {
+		pr_warn("%s Could not alloc %d pfns rc:%d\n", __func__,
+			numpgs, rc);
+		kvfree(pages);
+		return -ENOMEM;
+	}
+	BUG_ON(vma->vm_private_data != NULL);
+	vma->vm_private_data = pages;
+
+	return 0;
+}
+
+static const struct vm_operations_struct privcmd_vm_ops;
+
+static long privcmd_ioctl_mmap_batch(
+	struct file *file, void __user *udata, int version)
+{
+	struct privcmd_data *data = file->private_data;
+	int ret;
+	struct privcmd_mmapbatch_v2 m;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	unsigned long nr_pages;
+	LIST_HEAD(pagelist);
+	struct mmap_batch_state state;
+
+	switch (version) {
+	case 1:
+		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch)))
+			return -EFAULT;
+		/* Returns per-frame error in m.arr. */
+		m.err = NULL;
+		if (!access_ok(m.arr, m.num * sizeof(*m.arr)))
+			return -EFAULT;
+		break;
+	case 2:
+		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch_v2)))
+			return -EFAULT;
+		/* Returns per-frame error code in m.err. */
+		if (!access_ok(m.err, m.num * (sizeof(*m.err))))
+			return -EFAULT;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* If restriction is in place, check the domid matches */
+	if (data->domid != DOMID_INVALID && data->domid != m.dom)
+		return -EPERM;
+
+	nr_pages = DIV_ROUND_UP(m.num, XEN_PFN_PER_PAGE);
+	if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
+		return -EINVAL;
+
+	ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t), m.arr);
+
+	if (ret)
+		goto out;
+	if (list_empty(&pagelist)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (version == 2) {
+		/* Zero error array now to only copy back actual errors. */
+		if (clear_user(m.err, sizeof(int) * m.num)) {
+			ret = -EFAULT;
+			goto out;
+		}
+	}
+
+	mmap_write_lock(mm);
+
+	vma = find_vma(mm, m.addr);
+	if (!vma ||
+	    vma->vm_ops != &privcmd_vm_ops) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	/*
+	 * Caller must either:
+	 *
+	 * Map the whole VMA range, which will also allocate all the
+	 * pages required for the auto_translated_physmap case.
+	 *
+	 * Or
+	 *
+	 * Map unmapped holes left from a previous map attempt (e.g.,
+	 * because those foreign frames were previously paged out).
+	 */
+	if (vma->vm_private_data == NULL) {
+		if (m.addr != vma->vm_start ||
+		    m.addr + (nr_pages << PAGE_SHIFT) != vma->vm_end) {
+			ret = -EINVAL;
+			goto out_unlock;
+		}
+		if (!xen_pv_domain()) {
+			ret = alloc_empty_pages(vma, nr_pages);
+			if (ret < 0)
+				goto out_unlock;
+		} else
+			vma->vm_private_data = PRIV_VMA_LOCKED;
+	} else {
+		if (m.addr < vma->vm_start ||
+		    m.addr + (nr_pages << PAGE_SHIFT) > vma->vm_end) {
+			ret = -EINVAL;
+			goto out_unlock;
+		}
+		if (privcmd_vma_range_is_mapped(vma, m.addr, nr_pages)) {
+			ret = -EINVAL;
+			goto out_unlock;
+		}
+	}
+
+	state.domain        = m.dom;
+	state.vma           = vma;
+	state.va            = m.addr;
+	state.index         = 0;
+	state.global_error  = 0;
+	state.version       = version;
+
+	BUILD_BUG_ON(((PAGE_SIZE / sizeof(xen_pfn_t)) % XEN_PFN_PER_PAGE) != 0);
+	/* mmap_batch_fn guarantees ret == 0 */
+	BUG_ON(traverse_pages_block(m.num, sizeof(xen_pfn_t),
+				    &pagelist, mmap_batch_fn, &state));
+
+	mmap_write_unlock(mm);
+
+	if (state.global_error) {
+		/* Write back errors in second pass. */
+		state.user_gfn = (xen_pfn_t *)m.arr;
+		state.user_err = m.err;
+		ret = traverse_pages_block(m.num, sizeof(xen_pfn_t),
+					   &pagelist, mmap_return_errors, &state);
+	} else
+		ret = 0;
+
+	/* If we have not had any EFAULT-like global errors then set the global
+	 * error to -ENOENT if necessary. */
+	if ((ret == 0) && (state.global_error == -ENOENT))
+		ret = -ENOENT;
+
+out:
+	free_page_list(&pagelist);
+	return ret;
+
+out_unlock:
+	mmap_write_unlock(mm);
+	goto out;
+}
+
+static int lock_pages(
+	struct privcmd_dm_op_buf kbufs[], unsigned int num,
+	struct page *pages[], unsigned int nr_pages, unsigned int *pinned)
+{
+	unsigned int i, off = 0;
+
+	for (i = 0; i < num; ) {
+		unsigned int requested;
+		int page_count;
+
+		requested = DIV_ROUND_UP(
+			offset_in_page(kbufs[i].uptr) + kbufs[i].size,
+			PAGE_SIZE) - off;
+		if (requested > nr_pages)
+			return -ENOSPC;
+
+		page_count = pin_user_pages_fast(
+			(unsigned long)kbufs[i].uptr + off * PAGE_SIZE,
+			requested, FOLL_WRITE, pages);
+		if (page_count <= 0)
+			return page_count ? : -EFAULT;
+
+		*pinned += page_count;
+		nr_pages -= page_count;
+		pages += page_count;
+
+		off = (requested == page_count) ? 0 : off + page_count;
+		i += !off;
+	}
+
+	return 0;
+}
+
+static void unlock_pages(struct page *pages[], unsigned int nr_pages)
+{
+	unpin_user_pages_dirty_lock(pages, nr_pages, true);
+}
+
+static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
+{
+	struct privcmd_data *data = file->private_data;
+	struct privcmd_dm_op kdata;
+	struct privcmd_dm_op_buf *kbufs;
+	unsigned int nr_pages = 0;
+	struct page **pages = NULL;
+	struct xen_dm_op_buf *xbufs = NULL;
+	unsigned int i;
+	long rc;
+	unsigned int pinned = 0;
+
+	if (copy_from_user(&kdata, udata, sizeof(kdata)))
+		return -EFAULT;
+
+	/* If restriction is in place, check the domid matches */
+	if (data->domid != DOMID_INVALID && data->domid != kdata.dom)
+		return -EPERM;
+
+	if (kdata.num == 0)
+		return 0;
+
+	if (kdata.num > privcmd_dm_op_max_num)
+		return -E2BIG;
+
+	kbufs = kzalloc_objs(*kbufs, kdata.num);
+	if (!kbufs)
+		return -ENOMEM;
+
+	if (copy_from_user(kbufs, kdata.ubufs,
+			   sizeof(*kbufs) * kdata.num)) {
+		rc = -EFAULT;
+		goto out;
+	}
+
+	for (i = 0; i < kdata.num; i++) {
+		if (kbufs[i].size > privcmd_dm_op_buf_max_size) {
+			rc = -E2BIG;
+			goto out;
+		}
+
+		if (!access_ok(kbufs[i].uptr,
+			       kbufs[i].size)) {
+			rc = -EFAULT;
+			goto out;
+		}
+
+		nr_pages += DIV_ROUND_UP(
+			offset_in_page(kbufs[i].uptr) + kbufs[i].size,
+			PAGE_SIZE);
+	}
+
+	pages = kzalloc_objs(*pages, nr_pages);
+	if (!pages) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	xbufs = kzalloc_objs(*xbufs, kdata.num);
+	if (!xbufs) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned);
+	if (rc < 0)
+		goto out;
+
+	for (i = 0; i < kdata.num; i++) {
+		set_xen_guest_handle(xbufs[i].h, kbufs[i].uptr);
+		xbufs[i].size = kbufs[i].size;
+	}
+
+	xen_preemptible_hcall_begin();
+	rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
+	xen_preemptible_hcall_end();
+
+out:
+	unlock_pages(pages, pinned);
+	kfree(xbufs);
+	kfree(pages);
+	kfree(kbufs);
+
+	return rc;
+}
+
+static long privcmd_ioctl_restrict(struct file *file, void __user *udata)
+{
+	struct privcmd_data *data = file->private_data;
+	domid_t dom;
+
+	if (copy_from_user(&dom, udata, sizeof(dom)))
+		return -EFAULT;
+
+	/* Set restriction to the specified domain, or check it matches */
+	if (data->domid == DOMID_INVALID)
+		data->domid = dom;
+	else if (data->domid != dom)
+		return -EINVAL;
+
+	return 0;
+}
+
+static long privcmd_ioctl_mmap_resource(struct file *file,
+				struct privcmd_mmap_resource __user *udata)
+{
+	struct privcmd_data *data = file->private_data;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	struct privcmd_mmap_resource kdata;
+	xen_pfn_t *pfns = NULL;
+	struct xen_mem_acquire_resource xdata = { };
+	int rc;
+
+	if (copy_from_user(&kdata, udata, sizeof(kdata)))
+		return -EFAULT;
+
+	/* If restriction is in place, check the domid matches */
+	if (data->domid != DOMID_INVALID && data->domid != kdata.dom)
+		return -EPERM;
+
+	/* Both fields must be set or unset */
+	if (!!kdata.addr != !!kdata.num)
+		return -EINVAL;
+
+	xdata.domid = kdata.dom;
+	xdata.type = kdata.type;
+	xdata.id = kdata.id;
+
+	if (!kdata.addr && !kdata.num) {
+		/* Query the size of the resource. */
+		rc = HYPERVISOR_memory_op(XENMEM_acquire_resource, &xdata);
+		if (rc)
+			return rc;
+		return __put_user(xdata.nr_frames, &udata->num);
+	}
+
+	mmap_write_lock(mm);
+
+	vma = find_vma(mm, kdata.addr);
+	if (!vma || vma->vm_ops != &privcmd_vm_ops) {
+		rc = -EINVAL;
+		goto out;
+	}
+
+	pfns = kzalloc_objs(*pfns, kdata.num, GFP_KERNEL | __GFP_NOWARN);
+	if (!pfns) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	if (!xen_pv_domain()) {
+		unsigned int nr = DIV_ROUND_UP(kdata.num, XEN_PFN_PER_PAGE);
+		struct page **pages;
+		unsigned int i;
+
+		rc = alloc_empty_pages(vma, nr);
+		if (rc < 0)
+			goto out;
+
+		pages = vma->vm_private_data;
+
+		for (i = 0; i < kdata.num; i++) {
+			xen_pfn_t pfn =
+				page_to_xen_pfn(pages[i / XEN_PFN_PER_PAGE]);
+
+			pfns[i] = pfn + (i % XEN_PFN_PER_PAGE);
+		}
+	} else
+		vma->vm_private_data = PRIV_VMA_LOCKED;
+
+	xdata.frame = kdata.idx;
+	xdata.nr_frames = kdata.num;
+	set_xen_guest_handle(xdata.frame_list, pfns);
+
+	xen_preemptible_hcall_begin();
+	rc = HYPERVISOR_memory_op(XENMEM_acquire_resource, &xdata);
+	xen_preemptible_hcall_end();
+
+	if (rc)
+		goto out;
+
+	if (!xen_pv_domain()) {
+		rc = xen_remap_vma_range(vma, kdata.addr, kdata.num << PAGE_SHIFT);
+	} else {
+		unsigned int domid =
+			(xdata.flags & XENMEM_rsrc_acq_caller_owned) ?
+			DOMID_SELF : kdata.dom;
+		int num, *errs = (int *)pfns;
+
+		BUILD_BUG_ON(sizeof(*errs) > sizeof(*pfns));
+		num = xen_remap_domain_mfn_array(vma,
+						 kdata.addr & PAGE_MASK,
+						 pfns, kdata.num, errs,
+						 vma->vm_page_prot,
+						 domid);
+		if (num < 0)
+			rc = num;
+		else if (num != kdata.num) {
+			unsigned int i;
+
+			for (i = 0; i < num; i++) {
+				rc = errs[i];
+				if (rc < 0)
+					break;
+			}
+		} else
+			rc = 0;
+	}
+
+out:
+	mmap_write_unlock(mm);
+	kfree(pfns);
+
+	return rc;
+}
+
+static long privcmd_ioctl_pcidev_get_gsi(struct file *file, void __user *udata)
+{
+#if defined(CONFIG_XEN_ACPI)
+	int rc;
+	struct privcmd_pcidev_get_gsi kdata;
+
+	if (copy_from_user(&kdata, udata, sizeof(kdata)))
+		return -EFAULT;
+
+	rc = xen_acpi_get_gsi_from_sbdf(kdata.sbdf);
+	if (rc < 0)
+		return rc;
+
+	kdata.gsi = rc;
+	if (copy_to_user(udata, &kdata, sizeof(kdata)))
+		return -EFAULT;
+
+	return 0;
+#else
+	return -EINVAL;
+#endif
+}
+
+#ifdef CONFIG_XEN_PRIVCMD_EVENTFD
+/* Irqfd support */
+static struct workqueue_struct *irqfd_cleanup_wq;
+static DEFINE_SPINLOCK(irqfds_lock);
+DEFINE_STATIC_SRCU(irqfds_srcu);
+static LIST_HEAD(irqfds_list);
+
+struct privcmd_kernel_irqfd {
+	struct xen_dm_op_buf xbufs;
+	domid_t dom;
+	bool error;
+	struct eventfd_ctx *eventfd;
+	struct work_struct shutdown;
+	wait_queue_entry_t wait;
+	struct list_head list;
+	poll_table pt;
+};
+
+static void irqfd_deactivate(struct privcmd_kernel_irqfd *kirqfd)
+{
+	lockdep_assert_held(&irqfds_lock);
+
+	list_del_init(&kirqfd->list);
+	queue_work(irqfd_cleanup_wq, &kirqfd->shutdown);
+}
+
+static void irqfd_shutdown(struct work_struct *work)
+{
+	struct privcmd_kernel_irqfd *kirqfd =
+		container_of(work, struct privcmd_kernel_irqfd, shutdown);
+	u64 cnt;
+
+	/* Make sure irqfd has been initialized in assign path */
+	synchronize_srcu(&irqfds_srcu);
+
+	eventfd_ctx_remove_wait_queue(kirqfd->eventfd, &kirqfd->wait, &cnt);
+	eventfd_ctx_put(kirqfd->eventfd);
+	kfree(kirqfd);
+}
+
+static void irqfd_inject(struct privcmd_kernel_irqfd *kirqfd)
+{
+	u64 cnt;
+	long rc;
+
+	eventfd_ctx_do_read(kirqfd->eventfd, &cnt);
+
+	xen_preemptible_hcall_begin();
+	rc = HYPERVISOR_dm_op(kirqfd->dom, 1, &kirqfd->xbufs);
+	xen_preemptible_hcall_end();
+
+	/* Don't repeat the error message for consecutive failures */
+	if (rc && !kirqfd->error) {
+		pr_err("Failed to configure irq for guest domain: %d\n",
+		       kirqfd->dom);
+	}
+
+	kirqfd->error = rc;
+}
+
+static int
+irqfd_wakeup(wait_queue_entry_t *wait, unsigned int mode, int sync, void *key)
+{
+	struct privcmd_kernel_irqfd *kirqfd =
+		container_of(wait, struct privcmd_kernel_irqfd, wait);
+	__poll_t flags = key_to_poll(key);
+
+	if (flags & EPOLLIN)
+		irqfd_inject(kirqfd);
+
+	if (flags & EPOLLHUP) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&irqfds_lock, flags);
+		irqfd_deactivate(kirqfd);
+		spin_unlock_irqrestore(&irqfds_lock, flags);
+	}
+
+	return 0;
+}
+
+static void
+irqfd_poll_func(struct file *file, wait_queue_head_t *wqh, poll_table *pt)
+{
+	struct privcmd_kernel_irqfd *kirqfd =
+		container_of(pt, struct privcmd_kernel_irqfd, pt);
+
+	add_wait_queue_priority(wqh, &kirqfd->wait);
+}
+
+static int privcmd_irqfd_assign(struct privcmd_irqfd *irqfd)
+{
+	struct privcmd_kernel_irqfd *kirqfd, *tmp;
+	unsigned long flags;
+	__poll_t events;
+	void *dm_op;
+	int ret, idx;
+
+	CLASS(fd, f)(irqfd->fd);
+
+	kirqfd = kzalloc(sizeof(*kirqfd) + irqfd->size, GFP_KERNEL);
+	if (!kirqfd)
+		return -ENOMEM;
+	dm_op = kirqfd + 1;
+
+	if (copy_from_user(dm_op, u64_to_user_ptr(irqfd->dm_op), irqfd->size)) {
+		ret = -EFAULT;
+		goto error_kfree;
+	}
+
+	kirqfd->xbufs.size = irqfd->size;
+	set_xen_guest_handle(kirqfd->xbufs.h, dm_op);
+	kirqfd->dom = irqfd->dom;
+	INIT_WORK(&kirqfd->shutdown, irqfd_shutdown);
+
+	if (fd_empty(f)) {
+		ret = -EBADF;
+		goto error_kfree;
+	}
+
+	kirqfd->eventfd = eventfd_ctx_fileget(fd_file(f));
+	if (IS_ERR(kirqfd->eventfd)) {
+		ret = PTR_ERR(kirqfd->eventfd);
+		goto error_kfree;
+	}
+
+	/*
+	 * Install our own custom wake-up handling so we are notified via a
+	 * callback whenever someone signals the underlying eventfd.
+	 */
+	init_waitqueue_func_entry(&kirqfd->wait, irqfd_wakeup);
+	init_poll_funcptr(&kirqfd->pt, irqfd_poll_func);
+
+	spin_lock_irqsave(&irqfds_lock, flags);
+
+	list_for_each_entry(tmp, &irqfds_list, list) {
+		if (kirqfd->eventfd == tmp->eventfd) {
+			ret = -EBUSY;
+			spin_unlock_irqrestore(&irqfds_lock, flags);
+			goto error_eventfd;
+		}
+	}
+
+	idx = srcu_read_lock(&irqfds_srcu);
+	list_add_tail(&kirqfd->list, &irqfds_list);
+	spin_unlock_irqrestore(&irqfds_lock, flags);
+
+	/*
+	 * Check if there was an event already pending on the eventfd before we
+	 * registered, and trigger it as if we didn't miss it.
+	 */
+	events = vfs_poll(fd_file(f), &kirqfd->pt);
+	if (events & EPOLLIN)
+		irqfd_inject(kirqfd);
+
+	srcu_read_unlock(&irqfds_srcu, idx);
+	return 0;
+
+error_eventfd:
+	eventfd_ctx_put(kirqfd->eventfd);
+
+error_kfree:
+	kfree(kirqfd);
+	return ret;
+}
+
+static int privcmd_irqfd_deassign(struct privcmd_irqfd *irqfd)
+{
+	struct privcmd_kernel_irqfd *kirqfd;
+	struct eventfd_ctx *eventfd;
+	unsigned long flags;
+
+	eventfd = eventfd_ctx_fdget(irqfd->fd);
+	if (IS_ERR(eventfd))
+		return PTR_ERR(eventfd);
+
+	spin_lock_irqsave(&irqfds_lock, flags);
+
+	list_for_each_entry(kirqfd, &irqfds_list, list) {
+		if (kirqfd->eventfd == eventfd) {
+			irqfd_deactivate(kirqfd);
+			break;
+		}
+	}
+
+	spin_unlock_irqrestore(&irqfds_lock, flags);
+
+	eventfd_ctx_put(eventfd);
+
+	/*
+	 * Block until we know all outstanding shutdown jobs have completed so
+	 * that we guarantee there will not be any more interrupts once this
+	 * deassign function returns.
+	 */
+	flush_workqueue(irqfd_cleanup_wq);
+
+	return 0;
+}
+
+static long privcmd_ioctl_irqfd(struct file *file, void __user *udata)
+{
+	struct privcmd_data *data = file->private_data;
+	struct privcmd_irqfd irqfd;
+
+	if (copy_from_user(&irqfd, udata, sizeof(irqfd)))
+		return -EFAULT;
+
+	/* No other flags should be set */
+	if (irqfd.flags & ~PRIVCMD_IRQFD_FLAG_DEASSIGN)
+		return -EINVAL;
+
+	/* If restriction is in place, check the domid matches */
+	if (data->domid != DOMID_INVALID && data->domid != irqfd.dom)
+		return -EPERM;
+
+	if (irqfd.flags & PRIVCMD_IRQFD_FLAG_DEASSIGN)
+		return privcmd_irqfd_deassign(&irqfd);
+
+	return privcmd_irqfd_assign(&irqfd);
+}
+
+static int privcmd_irqfd_init(void)
+{
+	irqfd_cleanup_wq = alloc_workqueue("privcmd-irqfd-cleanup", WQ_PERCPU,
+					   0);
+	if (!irqfd_cleanup_wq)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void privcmd_irqfd_exit(void)
+{
+	struct privcmd_kernel_irqfd *kirqfd, *tmp;
+	unsigned long flags;
+
+	spin_lock_irqsave(&irqfds_lock, flags);
+
+	list_for_each_entry_safe(kirqfd, tmp, &irqfds_list, list)
+		irqfd_deactivate(kirqfd);
+
+	spin_unlock_irqrestore(&irqfds_lock, flags);
+
+	destroy_workqueue(irqfd_cleanup_wq);
+}
+
+/* Ioeventfd Support */
+#define QUEUE_NOTIFY_VQ_MASK 0xFFFF
+
+static DEFINE_MUTEX(ioreq_lock);
+static LIST_HEAD(ioreq_list);
+
+/* per-eventfd structure */
+struct privcmd_kernel_ioeventfd {
+	struct eventfd_ctx *eventfd;
+	struct list_head list;
+	u64 addr;
+	unsigned int addr_len;
+	unsigned int vq;
+};
+
+/* per-guest CPU / port structure */
+struct ioreq_port {
+	int vcpu;
+	unsigned int port;
+	struct privcmd_kernel_ioreq *kioreq;
+};
+
+/* per-guest structure */
+struct privcmd_kernel_ioreq {
+	domid_t dom;
+	unsigned int vcpus;
+	u64 uioreq;
+	struct ioreq *ioreq;
+	spinlock_t lock; /* Protects ioeventfds list */
+	struct list_head ioeventfds;
+	struct list_head list;
+	struct ioreq_port ports[] __counted_by(vcpus);
+};
+
+static irqreturn_t ioeventfd_interrupt(int irq, void *dev_id)
+{
+	struct ioreq_port *port = dev_id;
+	struct privcmd_kernel_ioreq *kioreq = port->kioreq;
+	struct ioreq *ioreq = &kioreq->ioreq[port->vcpu];
+	struct privcmd_kernel_ioeventfd *kioeventfd;
+	unsigned int state = STATE_IOREQ_READY;
+
+	if (ioreq->state != STATE_IOREQ_READY ||
+	    ioreq->type != IOREQ_TYPE_COPY || ioreq->dir != IOREQ_WRITE)
+		return IRQ_NONE;
+
+	/*
+	 * We need a barrier, smp_mb(), here to ensure reads are finished before
+	 * `state` is updated. Since the lock implementation ensures that
+	 * appropriate barrier will be added anyway, we can avoid adding
+	 * explicit barrier here.
+	 *
+	 * Ideally we don't need to update `state` within the locks, but we do
+	 * that here to avoid adding explicit barrier.
+	 */
+
+	spin_lock(&kioreq->lock);
+	ioreq->state = STATE_IOREQ_INPROCESS;
+
+	list_for_each_entry(kioeventfd, &kioreq->ioeventfds, list) {
+		if (ioreq->addr == kioeventfd->addr + VIRTIO_MMIO_QUEUE_NOTIFY &&
+		    ioreq->size == kioeventfd->addr_len &&
+		    (ioreq->data & QUEUE_NOTIFY_VQ_MASK) == kioeventfd->vq) {
+			eventfd_signal(kioeventfd->eventfd);
+			state = STATE_IORESP_READY;
+			break;
+		}
+	}
+	spin_unlock(&kioreq->lock);
+
+	/*
+	 * We need a barrier, smp_mb(), here to ensure writes are finished
+	 * before `state` is updated. Since the lock implementation ensures that
+	 * appropriate barrier will be added anyway, we can avoid adding
+	 * explicit barrier here.
+	 */
+
+	ioreq->state = state;
+
+	if (state == STATE_IORESP_READY) {
+		notify_remote_via_evtchn(port->port);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static void ioreq_free(struct privcmd_kernel_ioreq *kioreq)
+{
+	struct ioreq_port *ports = kioreq->ports;
+	int i;
+
+	lockdep_assert_held(&ioreq_lock);
+
+	list_del(&kioreq->list);
+
+	for (i = kioreq->vcpus - 1; i >= 0; i--)
+		unbind_from_irqhandler(irq_from_evtchn(ports[i].port), &ports[i]);
+
+	kfree(kioreq);
+}
+
+static
+struct privcmd_kernel_ioreq *alloc_ioreq(struct privcmd_ioeventfd *ioeventfd)
+{
+	struct privcmd_kernel_ioreq *kioreq;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	struct page **pages;
+	unsigned int *ports;
+	int ret, size, i;
+
+	lockdep_assert_held(&ioreq_lock);
+
+	size = struct_size(kioreq, ports, ioeventfd->vcpus);
+	kioreq = kzalloc(size, GFP_KERNEL);
+	if (!kioreq)
+		return ERR_PTR(-ENOMEM);
+
+	kioreq->dom = ioeventfd->dom;
+	kioreq->vcpus = ioeventfd->vcpus;
+	kioreq->uioreq = ioeventfd->ioreq;
+	spin_lock_init(&kioreq->lock);
+	INIT_LIST_HEAD(&kioreq->ioeventfds);
+
+	/* The memory for ioreq server must have been mapped earlier */
+	mmap_write_lock(mm);
+	vma = find_vma(mm, (unsigned long)ioeventfd->ioreq);
+	if (!vma) {
+		pr_err("Failed to find vma for ioreq page!\n");
+		mmap_write_unlock(mm);
+		ret = -EFAULT;
+		goto error_kfree;
+	}
+
+	pages = vma->vm_private_data;
+	kioreq->ioreq = (struct ioreq *)(page_to_virt(pages[0]));
+	mmap_write_unlock(mm);
+
+	ports = memdup_array_user(u64_to_user_ptr(ioeventfd->ports),
+				  kioreq->vcpus, sizeof(*ports));
+	if (IS_ERR(ports)) {
+		ret = PTR_ERR(ports);
+		goto error_kfree;
+	}
+
+	for (i = 0; i < kioreq->vcpus; i++) {
+		kioreq->ports[i].vcpu = i;
+		kioreq->ports[i].port = ports[i];
+		kioreq->ports[i].kioreq = kioreq;
+
+		ret = bind_evtchn_to_irqhandler_lateeoi(ports[i],
+				ioeventfd_interrupt, IRQF_SHARED, "ioeventfd",
+				&kioreq->ports[i]);
+		if (ret < 0)
+			goto error_unbind;
+	}
+
+	kfree(ports);
+
+	list_add_tail(&kioreq->list, &ioreq_list);
+
+	return kioreq;
+
+error_unbind:
+	while (--i >= 0)
+		unbind_from_irqhandler(irq_from_evtchn(ports[i]), &kioreq->ports[i]);
+
+	kfree(ports);
+error_kfree:
+	kfree(kioreq);
+	return ERR_PTR(ret);
+}
+
+static struct privcmd_kernel_ioreq *
+get_ioreq(struct privcmd_ioeventfd *ioeventfd, struct eventfd_ctx *eventfd)
+{
+	struct privcmd_kernel_ioreq *kioreq;
+	unsigned long flags;
+
+	list_for_each_entry(kioreq, &ioreq_list, list) {
+		struct privcmd_kernel_ioeventfd *kioeventfd;
+
+		/*
+		 * kioreq fields can be accessed here without a lock as they are
+		 * never updated after being added to the ioreq_list.
+		 */
+		if (kioreq->uioreq != ioeventfd->ioreq) {
+			continue;
+		} else if (kioreq->dom != ioeventfd->dom ||
+			   kioreq->vcpus != ioeventfd->vcpus) {
+			pr_err("Invalid ioeventfd configuration mismatch, dom (%u vs %u), vcpus (%u vs %u)\n",
+			       kioreq->dom, ioeventfd->dom, kioreq->vcpus,
+			       ioeventfd->vcpus);
+			return ERR_PTR(-EINVAL);
+		}
+
+		/* Look for a duplicate eventfd for the same guest */
+		spin_lock_irqsave(&kioreq->lock, flags);
+		list_for_each_entry(kioeventfd, &kioreq->ioeventfds, list) {
+			if (eventfd == kioeventfd->eventfd) {
+				spin_unlock_irqrestore(&kioreq->lock, flags);
+				return ERR_PTR(-EBUSY);
+			}
+		}
+		spin_unlock_irqrestore(&kioreq->lock, flags);
+
+		return kioreq;
+	}
+
+	/* Matching kioreq isn't found, allocate a new one */
+	return alloc_ioreq(ioeventfd);
+}
+
+static void ioeventfd_free(struct privcmd_kernel_ioeventfd *kioeventfd)
+{
+	list_del(&kioeventfd->list);
+	eventfd_ctx_put(kioeventfd->eventfd);
+	kfree(kioeventfd);
+}
+
+static int privcmd_ioeventfd_assign(struct privcmd_ioeventfd *ioeventfd)
+{
+	struct privcmd_kernel_ioeventfd *kioeventfd;
+	struct privcmd_kernel_ioreq *kioreq;
+	unsigned long flags;
+	int ret;
+
+	/* Check for range overflow */
+	if (ioeventfd->addr + ioeventfd->addr_len < ioeventfd->addr)
+		return -EINVAL;
+
+	/* Vhost requires us to support length 1, 2, 4, and 8 */
+	if (!(ioeventfd->addr_len == 1 || ioeventfd->addr_len == 2 ||
+	      ioeventfd->addr_len == 4 || ioeventfd->addr_len == 8))
+		return -EINVAL;
+
+	/* 4096 vcpus limit enough ? */
+	if (!ioeventfd->vcpus || ioeventfd->vcpus > 4096)
+		return -EINVAL;
+
+	kioeventfd = kzalloc_obj(*kioeventfd);
+	if (!kioeventfd)
+		return -ENOMEM;
+
+	kioeventfd->eventfd = eventfd_ctx_fdget(ioeventfd->event_fd);
+	if (IS_ERR(kioeventfd->eventfd)) {
+		ret = PTR_ERR(kioeventfd->eventfd);
+		goto error_kfree;
+	}
+
+	kioeventfd->addr = ioeventfd->addr;
+	kioeventfd->addr_len = ioeventfd->addr_len;
+	kioeventfd->vq = ioeventfd->vq;
+
+	mutex_lock(&ioreq_lock);
+	kioreq = get_ioreq(ioeventfd, kioeventfd->eventfd);
+	if (IS_ERR(kioreq)) {
+		mutex_unlock(&ioreq_lock);
+		ret = PTR_ERR(kioreq);
+		goto error_eventfd;
+	}
+
+	spin_lock_irqsave(&kioreq->lock, flags);
+	list_add_tail(&kioeventfd->list, &kioreq->ioeventfds);
+	spin_unlock_irqrestore(&kioreq->lock, flags);
+
+	mutex_unlock(&ioreq_lock);
+
+	return 0;
+
+error_eventfd:
+	eventfd_ctx_put(kioeventfd->eventfd);
+
+error_kfree:
+	kfree(kioeventfd);
+	return ret;
+}
+
+static int privcmd_ioeventfd_deassign(struct privcmd_ioeventfd *ioeventfd)
+{
+	struct privcmd_kernel_ioreq *kioreq, *tkioreq;
+	struct eventfd_ctx *eventfd;
+	unsigned long flags;
+	int ret = 0;
+
+	eventfd = eventfd_ctx_fdget(ioeventfd->event_fd);
+	if (IS_ERR(eventfd))
+		return PTR_ERR(eventfd);
+
+	mutex_lock(&ioreq_lock);
+	list_for_each_entry_safe(kioreq, tkioreq, &ioreq_list, list) {
+		struct privcmd_kernel_ioeventfd *kioeventfd, *tmp;
+		/*
+		 * kioreq fields can be accessed here without a lock as they are
+		 * never updated after being added to the ioreq_list.
+		 */
+		if (kioreq->dom != ioeventfd->dom ||
+		    kioreq->uioreq != ioeventfd->ioreq ||
+		    kioreq->vcpus != ioeventfd->vcpus)
+			continue;
+
+		spin_lock_irqsave(&kioreq->lock, flags);
+		list_for_each_entry_safe(kioeventfd, tmp, &kioreq->ioeventfds, list) {
+			if (eventfd == kioeventfd->eventfd) {
+				ioeventfd_free(kioeventfd);
+				spin_unlock_irqrestore(&kioreq->lock, flags);
+
+				if (list_empty(&kioreq->ioeventfds))
+					ioreq_free(kioreq);
+				goto unlock;
+			}
+		}
+		spin_unlock_irqrestore(&kioreq->lock, flags);
+		break;
+	}
+
+	pr_err("Ioeventfd isn't already assigned, dom: %u, addr: %llu\n",
+	       ioeventfd->dom, ioeventfd->addr);
+	ret = -ENODEV;
+
+unlock:
+	mutex_unlock(&ioreq_lock);
+	eventfd_ctx_put(eventfd);
+
+	return ret;
+}
+
+static long privcmd_ioctl_ioeventfd(struct file *file, void __user *udata)
+{
+	struct privcmd_data *data = file->private_data;
+	struct privcmd_ioeventfd ioeventfd;
+
+	if (copy_from_user(&ioeventfd, udata, sizeof(ioeventfd)))
+		return -EFAULT;
+
+	/* No other flags should be set */
+	if (ioeventfd.flags & ~PRIVCMD_IOEVENTFD_FLAG_DEASSIGN)
+		return -EINVAL;
+
+	/* If restriction is in place, check the domid matches */
+	if (data->domid != DOMID_INVALID && data->domid != ioeventfd.dom)
+		return -EPERM;
+
+	if (ioeventfd.flags & PRIVCMD_IOEVENTFD_FLAG_DEASSIGN)
+		return privcmd_ioeventfd_deassign(&ioeventfd);
+
+	return privcmd_ioeventfd_assign(&ioeventfd);
+}
+
+static void privcmd_ioeventfd_exit(void)
+{
+	struct privcmd_kernel_ioreq *kioreq, *tmp;
+	unsigned long flags;
+
+	mutex_lock(&ioreq_lock);
+	list_for_each_entry_safe(kioreq, tmp, &ioreq_list, list) {
+		struct privcmd_kernel_ioeventfd *kioeventfd, *tmp;
+
+		spin_lock_irqsave(&kioreq->lock, flags);
+		list_for_each_entry_safe(kioeventfd, tmp, &kioreq->ioeventfds, list)
+			ioeventfd_free(kioeventfd);
+		spin_unlock_irqrestore(&kioreq->lock, flags);
+
+		ioreq_free(kioreq);
+	}
+	mutex_unlock(&ioreq_lock);
+}
+#else
+static inline long privcmd_ioctl_irqfd(struct file *file, void __user *udata)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int privcmd_irqfd_init(void)
+{
+	return 0;
+}
+
+static inline void privcmd_irqfd_exit(void)
+{
+}
+
+static inline long privcmd_ioctl_ioeventfd(struct file *file, void __user *udata)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void privcmd_ioeventfd_exit(void)
+{
+}
+#endif /* CONFIG_XEN_PRIVCMD_EVENTFD */
+
+static long privcmd_ioctl(struct file *file,
+			  unsigned int cmd, unsigned long data)
+{
+	int ret = -ENOTTY;
+	void __user *udata = (void __user *) data;
+
+	switch (cmd) {
+	case IOCTL_PRIVCMD_HYPERCALL:
+		ret = privcmd_ioctl_hypercall(file, udata);
+		break;
+
+	case IOCTL_PRIVCMD_MMAP:
+		ret = privcmd_ioctl_mmap(file, udata);
+		break;
+
+	case IOCTL_PRIVCMD_MMAPBATCH:
+		ret = privcmd_ioctl_mmap_batch(file, udata, 1);
+		break;
+
+	case IOCTL_PRIVCMD_MMAPBATCH_V2:
+		ret = privcmd_ioctl_mmap_batch(file, udata, 2);
+		break;
+
+	case IOCTL_PRIVCMD_DM_OP:
+		ret = privcmd_ioctl_dm_op(file, udata);
+		break;
+
+	case IOCTL_PRIVCMD_RESTRICT:
+		ret = privcmd_ioctl_restrict(file, udata);
+		break;
+
+	case IOCTL_PRIVCMD_MMAP_RESOURCE:
+		ret = privcmd_ioctl_mmap_resource(file, udata);
+		break;
+
+	case IOCTL_PRIVCMD_IRQFD:
+		ret = privcmd_ioctl_irqfd(file, udata);
+		break;
+
+	case IOCTL_PRIVCMD_IOEVENTFD:
+		ret = privcmd_ioctl_ioeventfd(file, udata);
+		break;
+
+	case IOCTL_PRIVCMD_PCIDEV_GET_GSI:
+		ret = privcmd_ioctl_pcidev_get_gsi(file, udata);
+		break;
+
+	default:
+		break;
+	}
+
+	return ret;
+}
+
+static int privcmd_open(struct inode *ino, struct file *file)
+{
+	struct privcmd_data *data;
+
+	if (wait_event_interruptible(restrict_wait_wq, !restrict_wait) < 0)
+		return -EINTR;
+
+	data = kzalloc_obj(*data);
+	if (!data)
+		return -ENOMEM;
+
+	data->domid = target_domain;
+
+	file->private_data = data;
+	return 0;
+}
+
+static int privcmd_release(struct inode *ino, struct file *file)
+{
+	struct privcmd_data *data = file->private_data;
+
+	kfree(data);
+	return 0;
+}
+
+static void privcmd_close(struct vm_area_struct *vma)
+{
+	struct page **pages = vma->vm_private_data;
+	int numpgs = vma_pages(vma);
+	int numgfns = (vma->vm_end - vma->vm_start) >> XEN_PAGE_SHIFT;
+	int rc;
+
+	if (xen_pv_domain() || !numpgs || !pages)
+		return;
+
+	rc = xen_unmap_domain_gfn_range(vma, numgfns, pages);
+	if (rc == 0)
+		xen_free_unpopulated_pages(numpgs, pages);
+	else
+		pr_crit("unable to unmap MFN range: leaking %d pages. rc=%d\n",
+			numpgs, rc);
+	kvfree(pages);
+}
+
+static int privcmd_may_split(struct vm_area_struct *area, unsigned long addr)
+{
+	/* Forbid splitting, avoids double free via privcmd_close(). */
+	return -EINVAL;
+}
+
+static vm_fault_t privcmd_fault(struct vm_fault *vmf)
+{
+	printk(KERN_DEBUG "privcmd_fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n",
+	       vmf->vma, vmf->vma->vm_start, vmf->vma->vm_end,
+	       vmf->pgoff, (void *)vmf->address);
+
+	return VM_FAULT_SIGBUS;
+}
+
+static const struct vm_operations_struct privcmd_vm_ops = {
+	.close = privcmd_close,
+	.may_split = privcmd_may_split,
+	.fault = privcmd_fault
+};
+
+static int privcmd_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	/* DONTCOPY is essential for Xen because copy_page_range doesn't know
+	 * how to recreate these mappings */
+	vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTCOPY |
+			 VM_DONTEXPAND | VM_DONTDUMP);
+	vma->vm_ops = &privcmd_vm_ops;
+	vma->vm_private_data = NULL;
+
+	return 0;
+}
+
+/*
+ * For MMAPBATCH*. This allows asserting the singleshot mapping
+ * on a per pfn/pte basis. Mapping calls that fail with ENOENT
+ * can be then retried until success.
+ */
+static int is_mapped_fn(pte_t *pte, unsigned long addr, void *data)
+{
+	return pte_none(ptep_get(pte)) ? 0 : -EBUSY;
+}
+
+static int privcmd_vma_range_is_mapped(
+	           struct vm_area_struct *vma,
+	           unsigned long addr,
+	           unsigned long nr_pages)
+{
+	return apply_to_page_range(vma->vm_mm, addr, nr_pages << PAGE_SHIFT,
+				   is_mapped_fn, NULL) != 0;
+}
+
+const struct file_operations xen_privcmd_fops = {
+	.owner = THIS_MODULE,
+	.unlocked_ioctl = privcmd_ioctl,
+	.open = privcmd_open,
+	.release = privcmd_release,
+	.mmap = privcmd_mmap,
+};
+EXPORT_SYMBOL_GPL(xen_privcmd_fops);
+
+static struct miscdevice privcmd_dev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "xen/privcmd",
+	.fops = &xen_privcmd_fops,
+};
+
+static int init_restrict(struct notifier_block *notifier,
+			 unsigned long event,
+			 void *data)
+{
+	char *target;
+	unsigned int domid;
+
+	/* Default to an guaranteed unused domain-id. */
+	target_domain = DOMID_IDLE;
+
+	target = xenbus_read(XBT_NIL, "target", "", NULL);
+	if (IS_ERR(target) || kstrtouint(target, 10, &domid)) {
+		pr_err("No target domain found, blocking all hypercalls\n");
+		goto out;
+	}
+
+	target_domain = domid;
+
+ out:
+	if (!IS_ERR(target))
+		kfree(target);
+
+	restrict_wait = false;
+	wake_up_all(&restrict_wait_wq);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block xenstore_notifier = {
+	.notifier_call = init_restrict,
+};
+
+static void __init restrict_driver(void)
+{
+	if (unrestricted) {
+		if (security_locked_down(LOCKDOWN_XEN_USER_ACTIONS))
+			pr_warn("Kernel is locked down, parameter \"unrestricted\" ignored\n");
+		else
+			return;
+	}
+
+	restrict_wait = true;
+
+	register_xenstore_notifier(&xenstore_notifier);
+}
+
+static int __init privcmd_init(void)
+{
+	int err;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	if (!xen_initial_domain())
+		restrict_driver();
+
+	err = misc_register(&privcmd_dev);
+	if (err != 0) {
+		pr_err("Could not register Xen privcmd device\n");
+		return err;
+	}
+
+	err = misc_register(&xen_privcmdbuf_dev);
+	if (err != 0) {
+		pr_err("Could not register Xen hypercall-buf device\n");
+		goto err_privcmdbuf;
+	}
+
+	err = privcmd_irqfd_init();
+	if (err != 0) {
+		pr_err("irqfd init failed\n");
+		goto err_irqfd;
+	}
+
+	return 0;
+
+err_irqfd:
+	misc_deregister(&xen_privcmdbuf_dev);
+err_privcmdbuf:
+	misc_deregister(&privcmd_dev);
+	return err;
+}
+
+static void __exit privcmd_exit(void)
+{
+	if (!xen_initial_domain())
+		unregister_xenstore_notifier(&xenstore_notifier);
+
+	privcmd_ioeventfd_exit();
+	privcmd_irqfd_exit();
+	misc_deregister(&privcmd_dev);
+	misc_deregister(&xen_privcmdbuf_dev);
+}
+
+module_init(privcmd_init);
+module_exit(privcmd_exit);
diff --git a/drivers/xen/privcmd.h b/drivers/xen/privcmd.h
new file mode 100644
index 000000000..0dd9f8f67
--- /dev/null
+++ b/drivers/xen/privcmd.h
@@ -0,0 +1,6 @@
+#include <linux/fs.h>
+
+extern const struct file_operations xen_privcmd_fops;
+extern const struct file_operations xen_privcmdbuf_fops;
+
+extern struct miscdevice xen_privcmdbuf_dev;
diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
new file mode 100644
index 000000000..ba62651a7
--- /dev/null
+++ b/drivers/xen/pvcalls-back.c
@@ -0,0 +1,1251 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * (c) 2017 Stefano Stabellini <stefano@aporeto.com>
+ */
+
+#include <linux/inet.h>
+#include <linux/kthread.h>
+#include <linux/list.h>
+#include <linux/radix-tree.h>
+#include <linux/module.h>
+#include <linux/semaphore.h>
+#include <linux/wait.h>
+#include <net/sock.h>
+#include <net/inet_common.h>
+#include <net/inet_connection_sock.h>
+#include <net/request_sock.h>
+#include <trace/events/sock.h>
+
+#include <xen/events.h>
+#include <xen/grant_table.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/interface/io/pvcalls.h>
+
+#define PVCALLS_VERSIONS "1"
+#define MAX_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
+
+static struct pvcalls_back_global {
+	struct list_head frontends;
+	struct semaphore frontends_lock;
+} pvcalls_back_global;
+
+/*
+ * Per-frontend data structure. It contains pointers to the command
+ * ring, its event channel, a list of active sockets and a tree of
+ * passive sockets.
+ */
+struct pvcalls_fedata {
+	struct list_head list;
+	struct xenbus_device *dev;
+	struct xen_pvcalls_sring *sring;
+	struct xen_pvcalls_back_ring ring;
+	int irq;
+	struct list_head socket_mappings;
+	struct radix_tree_root socketpass_mappings;
+	struct semaphore socket_lock;
+};
+
+struct pvcalls_ioworker {
+	struct work_struct register_work;
+	struct workqueue_struct *wq;
+};
+
+struct sock_mapping {
+	struct list_head list;
+	struct pvcalls_fedata *fedata;
+	struct sockpass_mapping *sockpass;
+	struct socket *sock;
+	uint64_t id;
+	grant_ref_t ref;
+	struct pvcalls_data_intf *ring;
+	void *bytes;
+	struct pvcalls_data data;
+	uint32_t ring_order;
+	int irq;
+	atomic_t read;
+	atomic_t write;
+	atomic_t io;
+	atomic_t release;
+	atomic_t eoi;
+	void (*saved_data_ready)(struct sock *sk);
+	struct pvcalls_ioworker ioworker;
+};
+
+struct sockpass_mapping {
+	struct list_head list;
+	struct pvcalls_fedata *fedata;
+	struct socket *sock;
+	uint64_t id;
+	struct xen_pvcalls_request reqcopy;
+	spinlock_t copy_lock;
+	struct workqueue_struct *wq;
+	struct work_struct register_work;
+	void (*saved_data_ready)(struct sock *sk);
+};
+
+static irqreturn_t pvcalls_back_conn_event(int irq, void *sock_map);
+static int pvcalls_back_release_active(struct xenbus_device *dev,
+				       struct pvcalls_fedata *fedata,
+				       struct sock_mapping *map);
+
+static bool pvcalls_conn_back_read(void *opaque)
+{
+	struct sock_mapping *map = (struct sock_mapping *)opaque;
+	struct msghdr msg;
+	struct kvec vec[2];
+	RING_IDX cons, prod, size, wanted, array_size, masked_prod, masked_cons;
+	int32_t error;
+	struct pvcalls_data_intf *intf = map->ring;
+	struct pvcalls_data *data = &map->data;
+	unsigned long flags;
+	int ret;
+
+	array_size = XEN_FLEX_RING_SIZE(map->ring_order);
+	cons = intf->in_cons;
+	prod = intf->in_prod;
+	error = intf->in_error;
+	/* read the indexes first, then deal with the data */
+	virt_mb();
+
+	if (error)
+		return false;
+
+	size = pvcalls_queued(prod, cons, array_size);
+	if (size >= array_size)
+		return false;
+	spin_lock_irqsave(&map->sock->sk->sk_receive_queue.lock, flags);
+	if (skb_queue_empty(&map->sock->sk->sk_receive_queue)) {
+		atomic_set(&map->read, 0);
+		spin_unlock_irqrestore(&map->sock->sk->sk_receive_queue.lock,
+				flags);
+		return true;
+	}
+	spin_unlock_irqrestore(&map->sock->sk->sk_receive_queue.lock, flags);
+	wanted = array_size - size;
+	masked_prod = pvcalls_mask(prod, array_size);
+	masked_cons = pvcalls_mask(cons, array_size);
+
+	memset(&msg, 0, sizeof(msg));
+	if (masked_prod < masked_cons) {
+		vec[0].iov_base = data->in + masked_prod;
+		vec[0].iov_len = wanted;
+		iov_iter_kvec(&msg.msg_iter, ITER_DEST, vec, 1, wanted);
+	} else {
+		vec[0].iov_base = data->in + masked_prod;
+		vec[0].iov_len = array_size - masked_prod;
+		vec[1].iov_base = data->in;
+		vec[1].iov_len = wanted - vec[0].iov_len;
+		iov_iter_kvec(&msg.msg_iter, ITER_DEST, vec, 2, wanted);
+	}
+
+	atomic_set(&map->read, 0);
+	ret = inet_recvmsg(map->sock, &msg, wanted, MSG_DONTWAIT);
+	WARN_ON(ret > wanted);
+	if (ret == -EAGAIN) /* shouldn't happen */
+		return true;
+	if (!ret)
+		ret = -ENOTCONN;
+	spin_lock_irqsave(&map->sock->sk->sk_receive_queue.lock, flags);
+	if (ret > 0 && !skb_queue_empty(&map->sock->sk->sk_receive_queue))
+		atomic_inc(&map->read);
+	spin_unlock_irqrestore(&map->sock->sk->sk_receive_queue.lock, flags);
+
+	/* write the data, then modify the indexes */
+	virt_wmb();
+	if (ret < 0) {
+		atomic_set(&map->read, 0);
+		intf->in_error = ret;
+	} else
+		intf->in_prod = prod + ret;
+	/* update the indexes, then notify the other end */
+	virt_wmb();
+	notify_remote_via_irq(map->irq);
+
+	return true;
+}
+
+static bool pvcalls_conn_back_write(struct sock_mapping *map)
+{
+	struct pvcalls_data_intf *intf = map->ring;
+	struct pvcalls_data *data = &map->data;
+	struct msghdr msg;
+	struct kvec vec[2];
+	RING_IDX cons, prod, size, array_size;
+	int ret;
+
+	atomic_set(&map->write, 0);
+
+	cons = intf->out_cons;
+	prod = intf->out_prod;
+	/* read the indexes before dealing with the data */
+	virt_mb();
+
+	array_size = XEN_FLEX_RING_SIZE(map->ring_order);
+	size = pvcalls_queued(prod, cons, array_size);
+	if (size == 0)
+		return false;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.msg_flags |= MSG_DONTWAIT;
+	if (pvcalls_mask(prod, array_size) > pvcalls_mask(cons, array_size)) {
+		vec[0].iov_base = data->out + pvcalls_mask(cons, array_size);
+		vec[0].iov_len = size;
+		iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, vec, 1, size);
+	} else {
+		vec[0].iov_base = data->out + pvcalls_mask(cons, array_size);
+		vec[0].iov_len = array_size - pvcalls_mask(cons, array_size);
+		vec[1].iov_base = data->out;
+		vec[1].iov_len = size - vec[0].iov_len;
+		iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, vec, 2, size);
+	}
+
+	ret = inet_sendmsg(map->sock, &msg, size);
+	if (ret == -EAGAIN) {
+		atomic_inc(&map->write);
+		atomic_inc(&map->io);
+		return true;
+	}
+
+	/* write the data, then update the indexes */
+	virt_wmb();
+	if (ret < 0) {
+		intf->out_error = ret;
+	} else {
+		intf->out_error = 0;
+		intf->out_cons = cons + ret;
+		prod = intf->out_prod;
+	}
+	/* update the indexes, then notify the other end */
+	virt_wmb();
+	if (prod != cons + ret) {
+		atomic_inc(&map->write);
+		atomic_inc(&map->io);
+	}
+	notify_remote_via_irq(map->irq);
+
+	return true;
+}
+
+static void pvcalls_back_ioworker(struct work_struct *work)
+{
+	struct pvcalls_ioworker *ioworker = container_of(work,
+		struct pvcalls_ioworker, register_work);
+	struct sock_mapping *map = container_of(ioworker, struct sock_mapping,
+		ioworker);
+	unsigned int eoi_flags = XEN_EOI_FLAG_SPURIOUS;
+
+	while (atomic_read(&map->io) > 0) {
+		if (atomic_read(&map->release) > 0) {
+			atomic_set(&map->release, 0);
+			return;
+		}
+
+		if (atomic_read(&map->read) > 0 &&
+		    pvcalls_conn_back_read(map))
+			eoi_flags = 0;
+		if (atomic_read(&map->write) > 0 &&
+		    pvcalls_conn_back_write(map))
+			eoi_flags = 0;
+
+		if (atomic_read(&map->eoi) > 0 && !atomic_read(&map->write)) {
+			atomic_set(&map->eoi, 0);
+			xen_irq_lateeoi(map->irq, eoi_flags);
+			eoi_flags = XEN_EOI_FLAG_SPURIOUS;
+		}
+
+		atomic_dec(&map->io);
+	}
+}
+
+static int pvcalls_back_socket(struct xenbus_device *dev,
+		struct xen_pvcalls_request *req)
+{
+	struct pvcalls_fedata *fedata;
+	int ret;
+	struct xen_pvcalls_response *rsp;
+
+	fedata = dev_get_drvdata(&dev->dev);
+
+	if (req->u.socket.domain != AF_INET ||
+	    req->u.socket.type != SOCK_STREAM ||
+	    (req->u.socket.protocol != IPPROTO_IP &&
+	     req->u.socket.protocol != AF_INET))
+		ret = -EAFNOSUPPORT;
+	else
+		ret = 0;
+
+	/* leave the actual socket allocation for later */
+
+	rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
+	rsp->req_id = req->req_id;
+	rsp->cmd = req->cmd;
+	rsp->u.socket.id = req->u.socket.id;
+	rsp->ret = ret;
+
+	return 0;
+}
+
+static void pvcalls_sk_state_change(struct sock *sock)
+{
+	struct sock_mapping *map = sock->sk_user_data;
+
+	if (map == NULL)
+		return;
+
+	atomic_inc(&map->read);
+	notify_remote_via_irq(map->irq);
+}
+
+static void pvcalls_sk_data_ready(struct sock *sock)
+{
+	struct sock_mapping *map = sock->sk_user_data;
+	struct pvcalls_ioworker *iow;
+
+	trace_sk_data_ready(sock);
+
+	if (map == NULL)
+		return;
+
+	iow = &map->ioworker;
+	atomic_inc(&map->read);
+	atomic_inc(&map->io);
+	queue_work(iow->wq, &iow->register_work);
+}
+
+static struct sock_mapping *pvcalls_new_active_socket(
+		struct pvcalls_fedata *fedata,
+		uint64_t id,
+		grant_ref_t ref,
+		evtchn_port_t evtchn,
+		struct socket *sock)
+{
+	int ret;
+	struct sock_mapping *map;
+	void *page;
+
+	map = kzalloc_obj(*map);
+	if (map == NULL) {
+		sock_release(sock);
+		return NULL;
+	}
+
+	map->fedata = fedata;
+	map->sock = sock;
+	map->id = id;
+	map->ref = ref;
+
+	ret = xenbus_map_ring_valloc(fedata->dev, &ref, 1, &page);
+	if (ret < 0)
+		goto out;
+	map->ring = page;
+	map->ring_order = map->ring->ring_order;
+	/* first read the order, then map the data ring */
+	virt_rmb();
+	if (map->ring_order > MAX_RING_ORDER) {
+		pr_warn("%s frontend requested ring_order %u, which is > MAX (%u)\n",
+				__func__, map->ring_order, MAX_RING_ORDER);
+		goto out;
+	}
+	ret = xenbus_map_ring_valloc(fedata->dev, map->ring->ref,
+				     (1 << map->ring_order), &page);
+	if (ret < 0)
+		goto out;
+	map->bytes = page;
+
+	ret = bind_interdomain_evtchn_to_irqhandler_lateeoi(
+			fedata->dev, evtchn,
+			pvcalls_back_conn_event, 0, "pvcalls-backend", map);
+	if (ret < 0)
+		goto out;
+	map->irq = ret;
+
+	map->data.in = map->bytes;
+	map->data.out = map->bytes + XEN_FLEX_RING_SIZE(map->ring_order);
+
+	map->ioworker.wq = alloc_ordered_workqueue("pvcalls_io", 0);
+	if (!map->ioworker.wq)
+		goto out;
+	atomic_set(&map->io, 1);
+	INIT_WORK(&map->ioworker.register_work,	pvcalls_back_ioworker);
+
+	down(&fedata->socket_lock);
+	list_add_tail(&map->list, &fedata->socket_mappings);
+	up(&fedata->socket_lock);
+
+	write_lock_bh(&map->sock->sk->sk_callback_lock);
+	map->saved_data_ready = map->sock->sk->sk_data_ready;
+	map->sock->sk->sk_user_data = map;
+	map->sock->sk->sk_data_ready = pvcalls_sk_data_ready;
+	map->sock->sk->sk_state_change = pvcalls_sk_state_change;
+	write_unlock_bh(&map->sock->sk->sk_callback_lock);
+
+	return map;
+out:
+	down(&fedata->socket_lock);
+	list_del(&map->list);
+	pvcalls_back_release_active(fedata->dev, fedata, map);
+	up(&fedata->socket_lock);
+	return NULL;
+}
+
+static int pvcalls_back_connect(struct xenbus_device *dev,
+				struct xen_pvcalls_request *req)
+{
+	struct pvcalls_fedata *fedata;
+	int ret = -EINVAL;
+	struct socket *sock;
+	struct sock_mapping *map;
+	struct xen_pvcalls_response *rsp;
+	struct sockaddr *sa = (struct sockaddr *)&req->u.connect.addr;
+
+	fedata = dev_get_drvdata(&dev->dev);
+
+	if (req->u.connect.len < sizeof(sa->sa_family) ||
+	    req->u.connect.len > sizeof(req->u.connect.addr) ||
+	    sa->sa_family != AF_INET)
+		goto out;
+
+	ret = sock_create(AF_INET, SOCK_STREAM, 0, &sock);
+	if (ret < 0)
+		goto out;
+	ret = inet_stream_connect(sock, (struct sockaddr_unsized *)sa, req->u.connect.len, 0);
+	if (ret < 0) {
+		sock_release(sock);
+		goto out;
+	}
+
+	map = pvcalls_new_active_socket(fedata,
+					req->u.connect.id,
+					req->u.connect.ref,
+					req->u.connect.evtchn,
+					sock);
+	if (!map)
+		ret = -EFAULT;
+
+out:
+	rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
+	rsp->req_id = req->req_id;
+	rsp->cmd = req->cmd;
+	rsp->u.connect.id = req->u.connect.id;
+	rsp->ret = ret;
+
+	return 0;
+}
+
+static int pvcalls_back_release_active(struct xenbus_device *dev,
+				       struct pvcalls_fedata *fedata,
+				       struct sock_mapping *map)
+{
+	disable_irq(map->irq);
+	if (map->sock->sk != NULL) {
+		write_lock_bh(&map->sock->sk->sk_callback_lock);
+		map->sock->sk->sk_user_data = NULL;
+		map->sock->sk->sk_data_ready = map->saved_data_ready;
+		write_unlock_bh(&map->sock->sk->sk_callback_lock);
+	}
+
+	atomic_set(&map->release, 1);
+	flush_work(&map->ioworker.register_work);
+
+	xenbus_unmap_ring_vfree(dev, map->bytes);
+	xenbus_unmap_ring_vfree(dev, (void *)map->ring);
+	unbind_from_irqhandler(map->irq, map);
+
+	sock_release(map->sock);
+	kfree(map);
+
+	return 0;
+}
+
+static int pvcalls_back_release_passive(struct xenbus_device *dev,
+					struct pvcalls_fedata *fedata,
+					struct sockpass_mapping *mappass)
+{
+	if (mappass->sock->sk != NULL) {
+		write_lock_bh(&mappass->sock->sk->sk_callback_lock);
+		mappass->sock->sk->sk_user_data = NULL;
+		mappass->sock->sk->sk_data_ready = mappass->saved_data_ready;
+		write_unlock_bh(&mappass->sock->sk->sk_callback_lock);
+	}
+	sock_release(mappass->sock);
+	destroy_workqueue(mappass->wq);
+	kfree(mappass);
+
+	return 0;
+}
+
+static int pvcalls_back_release(struct xenbus_device *dev,
+				struct xen_pvcalls_request *req)
+{
+	struct pvcalls_fedata *fedata;
+	struct sock_mapping *map, *n;
+	struct sockpass_mapping *mappass;
+	int ret = 0;
+	struct xen_pvcalls_response *rsp;
+
+	fedata = dev_get_drvdata(&dev->dev);
+
+	down(&fedata->socket_lock);
+	list_for_each_entry_safe(map, n, &fedata->socket_mappings, list) {
+		if (map->id == req->u.release.id) {
+			list_del(&map->list);
+			up(&fedata->socket_lock);
+			ret = pvcalls_back_release_active(dev, fedata, map);
+			goto out;
+		}
+	}
+	mappass = radix_tree_lookup(&fedata->socketpass_mappings,
+				    req->u.release.id);
+	if (mappass != NULL) {
+		radix_tree_delete(&fedata->socketpass_mappings, mappass->id);
+		up(&fedata->socket_lock);
+		ret = pvcalls_back_release_passive(dev, fedata, mappass);
+	} else
+		up(&fedata->socket_lock);
+
+out:
+	rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
+	rsp->req_id = req->req_id;
+	rsp->u.release.id = req->u.release.id;
+	rsp->cmd = req->cmd;
+	rsp->ret = ret;
+	return 0;
+}
+
+static void __pvcalls_back_accept(struct work_struct *work)
+{
+	struct sockpass_mapping *mappass = container_of(
+		work, struct sockpass_mapping, register_work);
+	struct proto_accept_arg arg = {
+		.flags = O_NONBLOCK,
+		.kern = true,
+	};
+	struct sock_mapping *map;
+	struct pvcalls_ioworker *iow;
+	struct pvcalls_fedata *fedata;
+	struct socket *sock;
+	struct xen_pvcalls_response *rsp;
+	struct xen_pvcalls_request *req;
+	int notify;
+	int ret = -EINVAL;
+	unsigned long flags;
+
+	fedata = mappass->fedata;
+	/*
+	 * __pvcalls_back_accept can race against pvcalls_back_accept.
+	 * We only need to check the value of "cmd" on read. It could be
+	 * done atomically, but to simplify the code on the write side, we
+	 * use a spinlock.
+	 */
+	spin_lock_irqsave(&mappass->copy_lock, flags);
+	req = &mappass->reqcopy;
+	if (req->cmd != PVCALLS_ACCEPT) {
+		spin_unlock_irqrestore(&mappass->copy_lock, flags);
+		return;
+	}
+	spin_unlock_irqrestore(&mappass->copy_lock, flags);
+
+	sock = sock_alloc();
+	if (sock == NULL)
+		goto out_error;
+	sock->type = mappass->sock->type;
+	sock->ops = mappass->sock->ops;
+
+	ret = inet_accept(mappass->sock, sock, &arg);
+	if (ret == -EAGAIN) {
+		sock_release(sock);
+		return;
+	}
+
+	map = pvcalls_new_active_socket(fedata,
+					req->u.accept.id_new,
+					req->u.accept.ref,
+					req->u.accept.evtchn,
+					sock);
+	if (!map) {
+		ret = -EFAULT;
+		goto out_error;
+	}
+
+	map->sockpass = mappass;
+	iow = &map->ioworker;
+	atomic_inc(&map->read);
+	atomic_inc(&map->io);
+	queue_work(iow->wq, &iow->register_work);
+
+out_error:
+	rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
+	rsp->req_id = req->req_id;
+	rsp->cmd = req->cmd;
+	rsp->u.accept.id = req->u.accept.id;
+	rsp->ret = ret;
+	RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&fedata->ring, notify);
+	if (notify)
+		notify_remote_via_irq(fedata->irq);
+
+	mappass->reqcopy.cmd = 0;
+}
+
+static void pvcalls_pass_sk_data_ready(struct sock *sock)
+{
+	struct sockpass_mapping *mappass = sock->sk_user_data;
+	struct pvcalls_fedata *fedata;
+	struct xen_pvcalls_response *rsp;
+	unsigned long flags;
+	int notify;
+
+	trace_sk_data_ready(sock);
+
+	if (mappass == NULL)
+		return;
+
+	fedata = mappass->fedata;
+	spin_lock_irqsave(&mappass->copy_lock, flags);
+	if (mappass->reqcopy.cmd == PVCALLS_POLL) {
+		rsp = RING_GET_RESPONSE(&fedata->ring,
+					fedata->ring.rsp_prod_pvt++);
+		rsp->req_id = mappass->reqcopy.req_id;
+		rsp->u.poll.id = mappass->reqcopy.u.poll.id;
+		rsp->cmd = mappass->reqcopy.cmd;
+		rsp->ret = 0;
+
+		mappass->reqcopy.cmd = 0;
+		spin_unlock_irqrestore(&mappass->copy_lock, flags);
+
+		RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&fedata->ring, notify);
+		if (notify)
+			notify_remote_via_irq(mappass->fedata->irq);
+	} else {
+		spin_unlock_irqrestore(&mappass->copy_lock, flags);
+		queue_work(mappass->wq, &mappass->register_work);
+	}
+}
+
+static int pvcalls_back_bind(struct xenbus_device *dev,
+			     struct xen_pvcalls_request *req)
+{
+	struct pvcalls_fedata *fedata;
+	int ret;
+	struct sockpass_mapping *map;
+	struct xen_pvcalls_response *rsp;
+
+	fedata = dev_get_drvdata(&dev->dev);
+
+	map = kzalloc_obj(*map);
+	if (map == NULL) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	INIT_WORK(&map->register_work, __pvcalls_back_accept);
+	spin_lock_init(&map->copy_lock);
+	map->wq = alloc_ordered_workqueue("pvcalls_wq", 0);
+	if (!map->wq) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = sock_create(AF_INET, SOCK_STREAM, 0, &map->sock);
+	if (ret < 0)
+		goto out;
+
+	ret = inet_bind(map->sock, (struct sockaddr_unsized *)&req->u.bind.addr,
+			req->u.bind.len);
+	if (ret < 0)
+		goto out;
+
+	map->fedata = fedata;
+	map->id = req->u.bind.id;
+
+	down(&fedata->socket_lock);
+	ret = radix_tree_insert(&fedata->socketpass_mappings, map->id,
+				map);
+	up(&fedata->socket_lock);
+	if (ret)
+		goto out;
+
+	write_lock_bh(&map->sock->sk->sk_callback_lock);
+	map->saved_data_ready = map->sock->sk->sk_data_ready;
+	map->sock->sk->sk_user_data = map;
+	map->sock->sk->sk_data_ready = pvcalls_pass_sk_data_ready;
+	write_unlock_bh(&map->sock->sk->sk_callback_lock);
+
+out:
+	if (ret) {
+		if (map && map->sock)
+			sock_release(map->sock);
+		if (map && map->wq)
+			destroy_workqueue(map->wq);
+		kfree(map);
+	}
+	rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
+	rsp->req_id = req->req_id;
+	rsp->cmd = req->cmd;
+	rsp->u.bind.id = req->u.bind.id;
+	rsp->ret = ret;
+	return 0;
+}
+
+static int pvcalls_back_listen(struct xenbus_device *dev,
+			       struct xen_pvcalls_request *req)
+{
+	struct pvcalls_fedata *fedata;
+	int ret = -EINVAL;
+	struct sockpass_mapping *map;
+	struct xen_pvcalls_response *rsp;
+
+	fedata = dev_get_drvdata(&dev->dev);
+
+	down(&fedata->socket_lock);
+	map = radix_tree_lookup(&fedata->socketpass_mappings, req->u.listen.id);
+	up(&fedata->socket_lock);
+	if (map == NULL)
+		goto out;
+
+	ret = inet_listen(map->sock, req->u.listen.backlog);
+
+out:
+	rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
+	rsp->req_id = req->req_id;
+	rsp->cmd = req->cmd;
+	rsp->u.listen.id = req->u.listen.id;
+	rsp->ret = ret;
+	return 0;
+}
+
+static int pvcalls_back_accept(struct xenbus_device *dev,
+			       struct xen_pvcalls_request *req)
+{
+	struct pvcalls_fedata *fedata;
+	struct sockpass_mapping *mappass;
+	int ret = -EINVAL;
+	struct xen_pvcalls_response *rsp;
+	unsigned long flags;
+
+	fedata = dev_get_drvdata(&dev->dev);
+
+	down(&fedata->socket_lock);
+	mappass = radix_tree_lookup(&fedata->socketpass_mappings,
+		req->u.accept.id);
+	up(&fedata->socket_lock);
+	if (mappass == NULL)
+		goto out_error;
+
+	/*
+	 * Limitation of the current implementation: only support one
+	 * concurrent accept or poll call on one socket.
+	 */
+	spin_lock_irqsave(&mappass->copy_lock, flags);
+	if (mappass->reqcopy.cmd != 0) {
+		spin_unlock_irqrestore(&mappass->copy_lock, flags);
+		ret = -EINTR;
+		goto out_error;
+	}
+
+	mappass->reqcopy = *req;
+	spin_unlock_irqrestore(&mappass->copy_lock, flags);
+	queue_work(mappass->wq, &mappass->register_work);
+
+	/* Tell the caller we don't need to send back a notification yet */
+	return -1;
+
+out_error:
+	rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
+	rsp->req_id = req->req_id;
+	rsp->cmd = req->cmd;
+	rsp->u.accept.id = req->u.accept.id;
+	rsp->ret = ret;
+	return 0;
+}
+
+static int pvcalls_back_poll(struct xenbus_device *dev,
+			     struct xen_pvcalls_request *req)
+{
+	struct pvcalls_fedata *fedata;
+	struct sockpass_mapping *mappass;
+	struct xen_pvcalls_response *rsp;
+	struct inet_connection_sock *icsk;
+	struct request_sock_queue *queue;
+	unsigned long flags;
+	int ret;
+	bool data;
+
+	fedata = dev_get_drvdata(&dev->dev);
+
+	down(&fedata->socket_lock);
+	mappass = radix_tree_lookup(&fedata->socketpass_mappings,
+				    req->u.poll.id);
+	up(&fedata->socket_lock);
+	if (mappass == NULL)
+		return -EINVAL;
+
+	/*
+	 * Limitation of the current implementation: only support one
+	 * concurrent accept or poll call on one socket.
+	 */
+	spin_lock_irqsave(&mappass->copy_lock, flags);
+	if (mappass->reqcopy.cmd != 0) {
+		ret = -EINTR;
+		goto out;
+	}
+
+	mappass->reqcopy = *req;
+	icsk = inet_csk(mappass->sock->sk);
+	queue = &icsk->icsk_accept_queue;
+	data = READ_ONCE(queue->rskq_accept_head) != NULL;
+	if (data) {
+		mappass->reqcopy.cmd = 0;
+		ret = 0;
+		goto out;
+	}
+	spin_unlock_irqrestore(&mappass->copy_lock, flags);
+
+	/* Tell the caller we don't need to send back a notification yet */
+	return -1;
+
+out:
+	spin_unlock_irqrestore(&mappass->copy_lock, flags);
+
+	rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
+	rsp->req_id = req->req_id;
+	rsp->cmd = req->cmd;
+	rsp->u.poll.id = req->u.poll.id;
+	rsp->ret = ret;
+	return 0;
+}
+
+static int pvcalls_back_handle_cmd(struct xenbus_device *dev,
+				   struct xen_pvcalls_request *req)
+{
+	int ret = 0;
+
+	switch (req->cmd) {
+	case PVCALLS_SOCKET:
+		ret = pvcalls_back_socket(dev, req);
+		break;
+	case PVCALLS_CONNECT:
+		ret = pvcalls_back_connect(dev, req);
+		break;
+	case PVCALLS_RELEASE:
+		ret = pvcalls_back_release(dev, req);
+		break;
+	case PVCALLS_BIND:
+		ret = pvcalls_back_bind(dev, req);
+		break;
+	case PVCALLS_LISTEN:
+		ret = pvcalls_back_listen(dev, req);
+		break;
+	case PVCALLS_ACCEPT:
+		ret = pvcalls_back_accept(dev, req);
+		break;
+	case PVCALLS_POLL:
+		ret = pvcalls_back_poll(dev, req);
+		break;
+	default:
+	{
+		struct pvcalls_fedata *fedata;
+		struct xen_pvcalls_response *rsp;
+
+		fedata = dev_get_drvdata(&dev->dev);
+		rsp = RING_GET_RESPONSE(
+				&fedata->ring, fedata->ring.rsp_prod_pvt++);
+		rsp->req_id = req->req_id;
+		rsp->cmd = req->cmd;
+		rsp->ret = -ENOTSUPP;
+		break;
+	}
+	}
+	return ret;
+}
+
+static void pvcalls_back_work(struct pvcalls_fedata *fedata)
+{
+	int notify, notify_all = 0, more = 1;
+	struct xen_pvcalls_request req;
+	struct xenbus_device *dev = fedata->dev;
+
+	while (more) {
+		while (RING_HAS_UNCONSUMED_REQUESTS(&fedata->ring)) {
+			RING_COPY_REQUEST(&fedata->ring,
+					  fedata->ring.req_cons++,
+					  &req);
+
+			if (!pvcalls_back_handle_cmd(dev, &req)) {
+				RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(
+					&fedata->ring, notify);
+				notify_all += notify;
+			}
+		}
+
+		if (notify_all) {
+			notify_remote_via_irq(fedata->irq);
+			notify_all = 0;
+		}
+
+		RING_FINAL_CHECK_FOR_REQUESTS(&fedata->ring, more);
+	}
+}
+
+static irqreturn_t pvcalls_back_event(int irq, void *dev_id)
+{
+	struct xenbus_device *dev = dev_id;
+	struct pvcalls_fedata *fedata = NULL;
+	unsigned int eoi_flags = XEN_EOI_FLAG_SPURIOUS;
+
+	if (dev) {
+		fedata = dev_get_drvdata(&dev->dev);
+		if (fedata) {
+			pvcalls_back_work(fedata);
+			eoi_flags = 0;
+		}
+	}
+
+	xen_irq_lateeoi(irq, eoi_flags);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t pvcalls_back_conn_event(int irq, void *sock_map)
+{
+	struct sock_mapping *map = sock_map;
+	struct pvcalls_ioworker *iow;
+
+	if (map == NULL || map->sock == NULL || map->sock->sk == NULL ||
+		map->sock->sk->sk_user_data != map) {
+		xen_irq_lateeoi(irq, 0);
+		return IRQ_HANDLED;
+	}
+
+	iow = &map->ioworker;
+
+	atomic_inc(&map->write);
+	atomic_inc(&map->eoi);
+	atomic_inc(&map->io);
+	queue_work(iow->wq, &iow->register_work);
+
+	return IRQ_HANDLED;
+}
+
+static int backend_connect(struct xenbus_device *dev)
+{
+	int err;
+	evtchn_port_t evtchn;
+	grant_ref_t ring_ref;
+	struct pvcalls_fedata *fedata = NULL;
+
+	fedata = kzalloc_obj(struct pvcalls_fedata);
+	if (!fedata)
+		return -ENOMEM;
+
+	fedata->irq = -1;
+	err = xenbus_scanf(XBT_NIL, dev->otherend, "port", "%u",
+			   &evtchn);
+	if (err != 1) {
+		err = -EINVAL;
+		xenbus_dev_fatal(dev, err, "reading %s/event-channel",
+				 dev->otherend);
+		goto error;
+	}
+
+	err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-ref", "%u", &ring_ref);
+	if (err != 1) {
+		err = -EINVAL;
+		xenbus_dev_fatal(dev, err, "reading %s/ring-ref",
+				 dev->otherend);
+		goto error;
+	}
+
+	err = bind_interdomain_evtchn_to_irq_lateeoi(dev, evtchn);
+	if (err < 0)
+		goto error;
+	fedata->irq = err;
+
+	err = request_threaded_irq(fedata->irq, NULL, pvcalls_back_event,
+				   IRQF_ONESHOT, "pvcalls-back", dev);
+	if (err < 0)
+		goto error;
+
+	err = xenbus_map_ring_valloc(dev, &ring_ref, 1,
+				     (void **)&fedata->sring);
+	if (err < 0)
+		goto error;
+
+	BACK_RING_INIT(&fedata->ring, fedata->sring, XEN_PAGE_SIZE * 1);
+	fedata->dev = dev;
+
+	INIT_LIST_HEAD(&fedata->socket_mappings);
+	INIT_RADIX_TREE(&fedata->socketpass_mappings, GFP_KERNEL);
+	sema_init(&fedata->socket_lock, 1);
+	dev_set_drvdata(&dev->dev, fedata);
+
+	down(&pvcalls_back_global.frontends_lock);
+	list_add_tail(&fedata->list, &pvcalls_back_global.frontends);
+	up(&pvcalls_back_global.frontends_lock);
+
+	return 0;
+
+ error:
+	if (fedata->irq >= 0)
+		unbind_from_irqhandler(fedata->irq, dev);
+	if (fedata->sring != NULL)
+		xenbus_unmap_ring_vfree(dev, fedata->sring);
+	kfree(fedata);
+	return err;
+}
+
+static int backend_disconnect(struct xenbus_device *dev)
+{
+	struct pvcalls_fedata *fedata;
+	struct sock_mapping *map, *n;
+	struct sockpass_mapping *mappass;
+	struct radix_tree_iter iter;
+	void **slot;
+
+
+	fedata = dev_get_drvdata(&dev->dev);
+
+	down(&fedata->socket_lock);
+	list_for_each_entry_safe(map, n, &fedata->socket_mappings, list) {
+		list_del(&map->list);
+		pvcalls_back_release_active(dev, fedata, map);
+	}
+
+	radix_tree_for_each_slot(slot, &fedata->socketpass_mappings, &iter, 0) {
+		mappass = radix_tree_deref_slot(slot);
+		if (!mappass)
+			continue;
+		if (radix_tree_exception(mappass)) {
+			if (radix_tree_deref_retry(mappass))
+				slot = radix_tree_iter_retry(&iter);
+		} else {
+			radix_tree_delete(&fedata->socketpass_mappings,
+					  mappass->id);
+			pvcalls_back_release_passive(dev, fedata, mappass);
+		}
+	}
+	up(&fedata->socket_lock);
+
+	unbind_from_irqhandler(fedata->irq, dev);
+	xenbus_unmap_ring_vfree(dev, fedata->sring);
+
+	list_del(&fedata->list);
+	kfree(fedata);
+	dev_set_drvdata(&dev->dev, NULL);
+
+	return 0;
+}
+
+static int pvcalls_back_probe(struct xenbus_device *dev,
+			      const struct xenbus_device_id *id)
+{
+	int err, abort;
+	struct xenbus_transaction xbt;
+
+again:
+	abort = 1;
+
+	err = xenbus_transaction_start(&xbt);
+	if (err) {
+		pr_warn("%s cannot create xenstore transaction\n", __func__);
+		return err;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename, "versions", "%s",
+			    PVCALLS_VERSIONS);
+	if (err) {
+		pr_warn("%s write out 'versions' failed\n", __func__);
+		goto abort;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename, "max-page-order", "%u",
+			    MAX_RING_ORDER);
+	if (err) {
+		pr_warn("%s write out 'max-page-order' failed\n", __func__);
+		goto abort;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename, "function-calls",
+			    XENBUS_FUNCTIONS_CALLS);
+	if (err) {
+		pr_warn("%s write out 'function-calls' failed\n", __func__);
+		goto abort;
+	}
+
+	abort = 0;
+abort:
+	err = xenbus_transaction_end(xbt, abort);
+	if (err) {
+		if (err == -EAGAIN && !abort)
+			goto again;
+		pr_warn("%s cannot complete xenstore transaction\n", __func__);
+		return err;
+	}
+
+	if (abort)
+		return -EFAULT;
+
+	xenbus_switch_state(dev, XenbusStateInitWait);
+
+	return 0;
+}
+
+static void set_backend_state(struct xenbus_device *dev,
+			      enum xenbus_state state)
+{
+	while (dev->state != state) {
+		switch (dev->state) {
+		case XenbusStateClosed:
+			switch (state) {
+			case XenbusStateInitWait:
+			case XenbusStateConnected:
+				xenbus_switch_state(dev, XenbusStateInitWait);
+				break;
+			case XenbusStateClosing:
+				xenbus_switch_state(dev, XenbusStateClosing);
+				break;
+			default:
+				WARN_ON(1);
+			}
+			break;
+		case XenbusStateInitWait:
+		case XenbusStateInitialised:
+			switch (state) {
+			case XenbusStateConnected:
+				if (backend_connect(dev))
+					return;
+				xenbus_switch_state(dev, XenbusStateConnected);
+				break;
+			case XenbusStateClosing:
+			case XenbusStateClosed:
+				xenbus_switch_state(dev, XenbusStateClosing);
+				break;
+			default:
+				WARN_ON(1);
+			}
+			break;
+		case XenbusStateConnected:
+			switch (state) {
+			case XenbusStateInitWait:
+			case XenbusStateClosing:
+			case XenbusStateClosed:
+				down(&pvcalls_back_global.frontends_lock);
+				backend_disconnect(dev);
+				up(&pvcalls_back_global.frontends_lock);
+				xenbus_switch_state(dev, XenbusStateClosing);
+				break;
+			default:
+				WARN_ON(1);
+			}
+			break;
+		case XenbusStateClosing:
+			switch (state) {
+			case XenbusStateInitWait:
+			case XenbusStateConnected:
+			case XenbusStateClosed:
+				xenbus_switch_state(dev, XenbusStateClosed);
+				break;
+			default:
+				WARN_ON(1);
+			}
+			break;
+		default:
+			WARN_ON(1);
+		}
+	}
+}
+
+static void pvcalls_back_changed(struct xenbus_device *dev,
+				 enum xenbus_state frontend_state)
+{
+	switch (frontend_state) {
+	case XenbusStateInitialising:
+		set_backend_state(dev, XenbusStateInitWait);
+		break;
+
+	case XenbusStateInitialised:
+	case XenbusStateConnected:
+		set_backend_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosing:
+		set_backend_state(dev, XenbusStateClosing);
+		break;
+
+	case XenbusStateClosed:
+		set_backend_state(dev, XenbusStateClosed);
+		if (xenbus_dev_is_online(dev))
+			break;
+		device_unregister(&dev->dev);
+		break;
+	case XenbusStateUnknown:
+		set_backend_state(dev, XenbusStateClosed);
+		device_unregister(&dev->dev);
+		break;
+
+	default:
+		xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
+				 frontend_state);
+		break;
+	}
+}
+
+static void pvcalls_back_remove(struct xenbus_device *dev)
+{
+}
+
+static int pvcalls_back_uevent(const struct xenbus_device *xdev,
+			       struct kobj_uevent_env *env)
+{
+	return 0;
+}
+
+static const struct xenbus_device_id pvcalls_back_ids[] = {
+	{ "pvcalls" },
+	{ "" }
+};
+
+static struct xenbus_driver pvcalls_back_driver = {
+	.ids = pvcalls_back_ids,
+	.probe = pvcalls_back_probe,
+	.remove = pvcalls_back_remove,
+	.uevent = pvcalls_back_uevent,
+	.otherend_changed = pvcalls_back_changed,
+};
+
+static int __init pvcalls_back_init(void)
+{
+	int ret;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	ret = xenbus_register_backend(&pvcalls_back_driver);
+	if (ret < 0)
+		return ret;
+
+	sema_init(&pvcalls_back_global.frontends_lock, 1);
+	INIT_LIST_HEAD(&pvcalls_back_global.frontends);
+	return 0;
+}
+module_init(pvcalls_back_init);
+
+static void __exit pvcalls_back_fin(void)
+{
+	struct pvcalls_fedata *fedata, *nfedata;
+
+	down(&pvcalls_back_global.frontends_lock);
+	list_for_each_entry_safe(fedata, nfedata,
+				 &pvcalls_back_global.frontends, list) {
+		backend_disconnect(fedata->dev);
+	}
+	up(&pvcalls_back_global.frontends_lock);
+
+	xenbus_unregister_driver(&pvcalls_back_driver);
+}
+
+module_exit(pvcalls_back_fin);
+
+MODULE_DESCRIPTION("Xen PV Calls backend driver");
+MODULE_AUTHOR("Stefano Stabellini <sstabellini@kernel.org>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
new file mode 100644
index 000000000..3e7aa807c
--- /dev/null
+++ b/drivers/xen/pvcalls-front.c
@@ -0,0 +1,1376 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * (c) 2017 Stefano Stabellini <stefano@aporeto.com>
+ */
+
+#include <linux/module.h>
+#include <linux/net.h>
+#include <linux/socket.h>
+
+#include <net/sock.h>
+
+#include <xen/events.h>
+#include <xen/grant_table.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/interface/io/pvcalls.h>
+
+#include "pvcalls-front.h"
+
+#define PVCALLS_INVALID_ID UINT_MAX
+#define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
+#define PVCALLS_NR_RSP_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE)
+#define PVCALLS_FRONT_MAX_SPIN 5000
+
+static struct proto pvcalls_proto = {
+	.name	= "PVCalls",
+	.owner	= THIS_MODULE,
+	.obj_size = sizeof(struct sock),
+};
+
+struct pvcalls_bedata {
+	struct xen_pvcalls_front_ring ring;
+	grant_ref_t ref;
+	int irq;
+	bool disabled;
+
+	struct list_head socket_mappings;
+	spinlock_t socket_lock;
+
+	wait_queue_head_t inflight_req;
+	struct xen_pvcalls_response rsp[PVCALLS_NR_RSP_PER_RING];
+};
+/* Only one front/back connection supported. */
+static struct xenbus_device *pvcalls_front_dev;
+static atomic_t pvcalls_refcount;
+
+/* first increment refcount, then proceed */
+#define pvcalls_enter() {               \
+	atomic_inc(&pvcalls_refcount);      \
+}
+
+/* first complete other operations, then decrement refcount */
+#define pvcalls_exit() {                \
+	atomic_dec(&pvcalls_refcount);      \
+}
+
+struct sock_mapping {
+	bool active_socket;
+	struct list_head list;
+	struct socket *sock;
+	atomic_t refcount;
+	union {
+		struct {
+			int irq;
+			grant_ref_t ref;
+			struct pvcalls_data_intf *ring;
+			struct pvcalls_data data;
+			struct mutex in_mutex;
+			struct mutex out_mutex;
+
+			wait_queue_head_t inflight_conn_req;
+		} active;
+		struct {
+		/*
+		 * Socket status, needs to be 64-bit aligned due to the
+		 * test_and_* functions which have this requirement on arm64.
+		 */
+#define PVCALLS_STATUS_UNINITALIZED  0
+#define PVCALLS_STATUS_BIND          1
+#define PVCALLS_STATUS_LISTEN        2
+			uint8_t status __attribute__((aligned(8)));
+		/*
+		 * Internal state-machine flags.
+		 * Only one accept operation can be inflight for a socket.
+		 * Only one poll operation can be inflight for a given socket.
+		 * flags needs to be 64-bit aligned due to the test_and_*
+		 * functions which have this requirement on arm64.
+		 */
+#define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
+#define PVCALLS_FLAG_POLL_INFLIGHT   1
+#define PVCALLS_FLAG_POLL_RET        2
+			uint8_t flags __attribute__((aligned(8)));
+			uint32_t inflight_req_id;
+			struct sock_mapping *accept_map;
+			wait_queue_head_t inflight_accept_req;
+		} passive;
+	};
+};
+
+static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
+{
+	struct sock_mapping *map;
+
+	if (!pvcalls_front_dev ||
+		dev_get_drvdata(&pvcalls_front_dev->dev) == NULL)
+		return ERR_PTR(-ENOTCONN);
+
+	map = (struct sock_mapping *)sock->sk->sk_send_head;
+	if (map == NULL)
+		return ERR_PTR(-ENOTSOCK);
+
+	pvcalls_enter();
+	atomic_inc(&map->refcount);
+	return map;
+}
+
+static inline void pvcalls_exit_sock(struct socket *sock)
+{
+	struct sock_mapping *map;
+
+	map = (struct sock_mapping *)sock->sk->sk_send_head;
+	atomic_dec(&map->refcount);
+	pvcalls_exit();
+}
+
+static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
+{
+	*req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
+	if (RING_FULL(&bedata->ring) ||
+	    bedata->rsp[*req_id].req_id != PVCALLS_INVALID_ID)
+		return -EAGAIN;
+	return 0;
+}
+
+/*
+ * Wait for the backend's response to req_id, or for the frontend to be
+ * disabled because the backend violated the wire protocol. Returns 0 once
+ * the response has arrived, or -EIO if the frontend was disabled.
+ */
+static int pvcalls_front_wait_rsp(struct pvcalls_bedata *bedata, u32 req_id)
+{
+	wait_event(bedata->inflight_req,
+		   READ_ONCE(bedata->rsp[req_id].req_id) == req_id ||
+		   READ_ONCE(bedata->disabled));
+
+	return READ_ONCE(bedata->disabled) ? -EIO : 0;
+}
+
+static bool pvcalls_front_write_todo(struct sock_mapping *map)
+{
+	struct pvcalls_data_intf *intf = map->active.ring;
+	RING_IDX cons, prod, size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
+	int32_t error;
+
+	error = intf->out_error;
+	if (error == -ENOTCONN)
+		return false;
+	if (error != 0)
+		return true;
+
+	cons = intf->out_cons;
+	prod = intf->out_prod;
+	return !!(size - pvcalls_queued(prod, cons, size));
+}
+
+static bool pvcalls_front_read_todo(struct sock_mapping *map)
+{
+	struct pvcalls_data_intf *intf = map->active.ring;
+	RING_IDX cons, prod;
+	int32_t error;
+
+	cons = intf->in_cons;
+	prod = intf->in_prod;
+	error = intf->in_error;
+	return (error != 0 ||
+		pvcalls_queued(prod, cons,
+			       XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER)) != 0);
+}
+
+static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
+{
+	struct xenbus_device *dev = dev_id;
+	struct pvcalls_bedata *bedata;
+	struct xen_pvcalls_response *rsp;
+	uint8_t *src, *dst;
+	u32 req_id = 0;
+	int more = 0, done = 0;
+
+	if (dev == NULL)
+		return IRQ_HANDLED;
+
+	pvcalls_enter();
+	bedata = dev_get_drvdata(&dev->dev);
+	if (bedata == NULL) {
+		pvcalls_exit();
+		return IRQ_HANDLED;
+	}
+	if (READ_ONCE(bedata->disabled)) {
+		pvcalls_exit();
+		return IRQ_HANDLED;
+	}
+
+again:
+	while (RING_HAS_UNCONSUMED_RESPONSES(&bedata->ring)) {
+		rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons);
+
+		req_id = rsp->req_id;
+		if (req_id >= PVCALLS_NR_RSP_PER_RING) {
+			/*
+			 * The backend supplied a req_id that would index
+			 * bedata->rsp[] out of bounds: a protocol violation
+			 * from a malicious or buggy backend. Log once, stop
+			 * trusting this backend and disable the frontend rather
+			 * than silently dropping the response and continuing.
+			 */
+			pr_err_once("pvcalls: backend sent out-of-range req_id %u, disabling frontend\n",
+				    req_id);
+			WRITE_ONCE(bedata->disabled, true);
+			bedata->ring.rsp_cons++;
+			done = 1;
+			break;
+		}
+		if (rsp->cmd == PVCALLS_POLL) {
+			struct sock_mapping *map = (struct sock_mapping *)(uintptr_t)
+						   rsp->u.poll.id;
+
+			clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
+				  (void *)&map->passive.flags);
+			/*
+			 * clear INFLIGHT, then set RET. It pairs with
+			 * the checks at the beginning of
+			 * pvcalls_front_poll_passive.
+			 */
+			smp_wmb();
+			set_bit(PVCALLS_FLAG_POLL_RET,
+				(void *)&map->passive.flags);
+		} else {
+			dst = (uint8_t *)&bedata->rsp[req_id] +
+			      sizeof(rsp->req_id);
+			src = (uint8_t *)rsp + sizeof(rsp->req_id);
+			memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
+			/*
+			 * First copy the rest of the data, then req_id. It is
+			 * paired with the barrier when accessing bedata->rsp.
+			 */
+			smp_wmb();
+			bedata->rsp[req_id].req_id = req_id;
+		}
+
+		done = 1;
+		bedata->ring.rsp_cons++;
+	}
+
+	RING_FINAL_CHECK_FOR_RESPONSES(&bedata->ring, more);
+	if (more && !READ_ONCE(bedata->disabled))
+		goto again;
+	if (done)
+		wake_up(&bedata->inflight_req);
+	pvcalls_exit();
+	return IRQ_HANDLED;
+}
+
+static void free_active_ring(struct sock_mapping *map);
+
+static void pvcalls_front_destroy_active(struct pvcalls_bedata *bedata,
+					 struct sock_mapping *map)
+{
+	int i;
+
+	unbind_from_irqhandler(map->active.irq, map);
+
+	if (bedata) {
+		spin_lock(&bedata->socket_lock);
+		if (!list_empty(&map->list))
+			list_del_init(&map->list);
+		spin_unlock(&bedata->socket_lock);
+	}
+
+	for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
+		gnttab_end_foreign_access(map->active.ring->ref[i], NULL);
+	gnttab_end_foreign_access(map->active.ref, NULL);
+	free_active_ring(map);
+}
+
+static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
+				   struct sock_mapping *map)
+{
+	pvcalls_front_destroy_active(bedata, map);
+
+	kfree(map);
+}
+
+static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
+{
+	struct sock_mapping *map = sock_map;
+
+	if (map == NULL)
+		return IRQ_HANDLED;
+
+	wake_up_interruptible(&map->active.inflight_conn_req);
+
+	return IRQ_HANDLED;
+}
+
+int pvcalls_front_socket(struct socket *sock)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map = NULL;
+	struct xen_pvcalls_request *req;
+	int notify, req_id, ret;
+
+	/*
+	 * PVCalls only supports domain AF_INET,
+	 * type SOCK_STREAM and protocol 0 sockets for now.
+	 *
+	 * Check socket type here, AF_INET and protocol checks are done
+	 * by the caller.
+	 */
+	if (sock->type != SOCK_STREAM)
+		return -EOPNOTSUPP;
+
+	pvcalls_enter();
+	if (!pvcalls_front_dev) {
+		pvcalls_exit();
+		return -EACCES;
+	}
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	map = kzalloc_obj(*map);
+	if (map == NULL) {
+		pvcalls_exit();
+		return -ENOMEM;
+	}
+
+	spin_lock(&bedata->socket_lock);
+
+	ret = get_request(bedata, &req_id);
+	if (ret < 0) {
+		kfree(map);
+		spin_unlock(&bedata->socket_lock);
+		pvcalls_exit();
+		return ret;
+	}
+
+	/*
+	 * sock->sk->sk_send_head is not used for ip sockets: reuse the
+	 * field to store a pointer to the struct sock_mapping
+	 * corresponding to the socket. This way, we can easily get the
+	 * struct sock_mapping from the struct socket.
+	 */
+	sock->sk->sk_send_head = (void *)map;
+	list_add_tail(&map->list, &bedata->socket_mappings);
+
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	req->cmd = PVCALLS_SOCKET;
+	req->u.socket.id = (uintptr_t) map;
+	req->u.socket.domain = AF_INET;
+	req->u.socket.type = SOCK_STREAM;
+	req->u.socket.protocol = IPPROTO_IP;
+
+	bedata->ring.req_prod_pvt++;
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
+	spin_unlock(&bedata->socket_lock);
+	if (notify)
+		notify_remote_via_irq(bedata->irq);
+
+	ret = pvcalls_front_wait_rsp(bedata, req_id);
+	if (ret) {
+		pvcalls_exit();
+		return ret;
+	}
+
+	/* read req_id, then the content */
+	smp_rmb();
+	ret = bedata->rsp[req_id].ret;
+	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
+
+	pvcalls_exit();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pvcalls_front_socket);
+
+static void free_active_ring(struct sock_mapping *map)
+{
+	if (!map->active.ring)
+		return;
+
+	free_pages_exact(map->active.data.in,
+			 PAGE_SIZE << map->active.ring->ring_order);
+	free_page((unsigned long)map->active.ring);
+}
+
+static int alloc_active_ring(struct sock_mapping *map)
+{
+	void *bytes;
+
+	map->active.ring = (struct pvcalls_data_intf *)
+		get_zeroed_page(GFP_KERNEL);
+	if (!map->active.ring)
+		goto out;
+
+	map->active.ring->ring_order = PVCALLS_RING_ORDER;
+	bytes = alloc_pages_exact(PAGE_SIZE << PVCALLS_RING_ORDER,
+				  GFP_KERNEL | __GFP_ZERO);
+	if (!bytes)
+		goto out;
+
+	map->active.data.in = bytes;
+	map->active.data.out = bytes +
+		XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
+
+	return 0;
+
+out:
+	free_active_ring(map);
+	return -ENOMEM;
+}
+
+static int create_active(struct sock_mapping *map, evtchn_port_t *evtchn)
+{
+	void *bytes;
+	int ret, irq = -1, i;
+
+	*evtchn = 0;
+	init_waitqueue_head(&map->active.inflight_conn_req);
+
+	bytes = map->active.data.in;
+	for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
+		map->active.ring->ref[i] = gnttab_grant_foreign_access(
+			pvcalls_front_dev->otherend_id,
+			pfn_to_gfn(virt_to_pfn(bytes) + i), 0);
+
+	map->active.ref = gnttab_grant_foreign_access(
+		pvcalls_front_dev->otherend_id,
+		pfn_to_gfn(virt_to_pfn((void *)map->active.ring)), 0);
+
+	ret = xenbus_alloc_evtchn(pvcalls_front_dev, evtchn);
+	if (ret)
+		goto out_error;
+	irq = bind_evtchn_to_irqhandler(*evtchn, pvcalls_front_conn_handler,
+					0, "pvcalls-frontend", map);
+	if (irq < 0) {
+		ret = irq;
+		goto out_error;
+	}
+
+	map->active.irq = irq;
+	map->active_socket = true;
+	mutex_init(&map->active.in_mutex);
+	mutex_init(&map->active.out_mutex);
+
+	return 0;
+
+out_error:
+	if (*evtchn > 0)
+		xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
+	return ret;
+}
+
+int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
+				int addr_len, int flags)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map = NULL;
+	struct xen_pvcalls_request *req;
+	int notify, req_id, ret;
+	evtchn_port_t evtchn;
+
+	if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
+		return -EOPNOTSUPP;
+
+	map = pvcalls_enter_sock(sock);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+	ret = alloc_active_ring(map);
+	if (ret < 0) {
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+	ret = create_active(map, &evtchn);
+	if (ret < 0) {
+		free_active_ring(map);
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+
+	spin_lock(&bedata->socket_lock);
+	ret = get_request(bedata, &req_id);
+	if (ret < 0) {
+		spin_unlock(&bedata->socket_lock);
+		pvcalls_front_destroy_active(NULL, map);
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	req->cmd = PVCALLS_CONNECT;
+	req->u.connect.id = (uintptr_t)map;
+	req->u.connect.len = addr_len;
+	req->u.connect.flags = flags;
+	req->u.connect.ref = map->active.ref;
+	req->u.connect.evtchn = evtchn;
+	memcpy(req->u.connect.addr, addr, sizeof(*addr));
+
+	map->sock = sock;
+
+	bedata->ring.req_prod_pvt++;
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
+	spin_unlock(&bedata->socket_lock);
+
+	if (notify)
+		notify_remote_via_irq(bedata->irq);
+
+	ret = pvcalls_front_wait_rsp(bedata, req_id);
+	if (ret) {
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+
+	/* read req_id, then the content */
+	smp_rmb();
+	ret = bedata->rsp[req_id].ret;
+	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
+	pvcalls_exit_sock(sock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pvcalls_front_connect);
+
+static int __write_ring(struct pvcalls_data_intf *intf,
+			struct pvcalls_data *data,
+			struct iov_iter *msg_iter,
+			int len)
+{
+	RING_IDX cons, prod, size, masked_prod, masked_cons;
+	RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
+	int32_t error;
+
+	error = intf->out_error;
+	if (error < 0)
+		return error;
+	cons = intf->out_cons;
+	prod = intf->out_prod;
+	/* read indexes before continuing */
+	virt_mb();
+
+	size = pvcalls_queued(prod, cons, array_size);
+	if (size > array_size)
+		return -EINVAL;
+	if (size == array_size)
+		return 0;
+	if (len > array_size - size)
+		len = array_size - size;
+
+	masked_prod = pvcalls_mask(prod, array_size);
+	masked_cons = pvcalls_mask(cons, array_size);
+
+	if (masked_prod < masked_cons) {
+		len = copy_from_iter(data->out + masked_prod, len, msg_iter);
+	} else {
+		if (len > array_size - masked_prod) {
+			int ret = copy_from_iter(data->out + masked_prod,
+				       array_size - masked_prod, msg_iter);
+			if (ret != array_size - masked_prod) {
+				len = ret;
+				goto out;
+			}
+			len = ret + copy_from_iter(data->out, len - ret, msg_iter);
+		} else {
+			len = copy_from_iter(data->out + masked_prod, len, msg_iter);
+		}
+	}
+out:
+	/* write to ring before updating pointer */
+	virt_wmb();
+	intf->out_prod += len;
+
+	return len;
+}
+
+int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
+			  size_t len)
+{
+	struct sock_mapping *map;
+	int sent, tot_sent = 0;
+	int count = 0, flags;
+
+	flags = msg->msg_flags;
+	if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
+		return -EOPNOTSUPP;
+
+	map = pvcalls_enter_sock(sock);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	mutex_lock(&map->active.out_mutex);
+	if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
+		mutex_unlock(&map->active.out_mutex);
+		pvcalls_exit_sock(sock);
+		return -EAGAIN;
+	}
+	if (len > INT_MAX)
+		len = INT_MAX;
+
+again:
+	count++;
+	sent = __write_ring(map->active.ring,
+			    &map->active.data, &msg->msg_iter,
+			    len);
+	if (sent > 0) {
+		len -= sent;
+		tot_sent += sent;
+		notify_remote_via_irq(map->active.irq);
+	}
+	if (sent >= 0 && len > 0 && count < PVCALLS_FRONT_MAX_SPIN)
+		goto again;
+	if (sent < 0)
+		tot_sent = sent;
+
+	mutex_unlock(&map->active.out_mutex);
+	pvcalls_exit_sock(sock);
+	return tot_sent;
+}
+EXPORT_SYMBOL_GPL(pvcalls_front_sendmsg);
+
+static int __read_ring(struct pvcalls_data_intf *intf,
+		       struct pvcalls_data *data,
+		       struct iov_iter *msg_iter,
+		       size_t len, int flags)
+{
+	RING_IDX cons, prod, size, masked_prod, masked_cons;
+	RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
+	int32_t error;
+
+	cons = intf->in_cons;
+	prod = intf->in_prod;
+	error = intf->in_error;
+	/* get pointers before reading from the ring */
+	virt_rmb();
+
+	size = pvcalls_queued(prod, cons, array_size);
+	masked_prod = pvcalls_mask(prod, array_size);
+	masked_cons = pvcalls_mask(cons, array_size);
+
+	if (size == 0)
+		return error ?: size;
+
+	if (len > size)
+		len = size;
+
+	if (masked_prod > masked_cons) {
+		len = copy_to_iter(data->in + masked_cons, len, msg_iter);
+	} else {
+		if (len > (array_size - masked_cons)) {
+			int ret = copy_to_iter(data->in + masked_cons,
+				     array_size - masked_cons, msg_iter);
+			if (ret != array_size - masked_cons) {
+				len = ret;
+				goto out;
+			}
+			len = ret + copy_to_iter(data->in, len - ret, msg_iter);
+		} else {
+			len = copy_to_iter(data->in + masked_cons, len, msg_iter);
+		}
+	}
+out:
+	/* read data from the ring before increasing the index */
+	virt_mb();
+	if (!(flags & MSG_PEEK))
+		intf->in_cons += len;
+
+	return len;
+}
+
+int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
+		     int flags)
+{
+	int ret;
+	struct sock_mapping *map;
+
+	if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
+		return -EOPNOTSUPP;
+
+	map = pvcalls_enter_sock(sock);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	mutex_lock(&map->active.in_mutex);
+	if (len > XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER))
+		len = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
+
+	while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
+		wait_event_interruptible(map->active.inflight_conn_req,
+					 pvcalls_front_read_todo(map));
+	}
+	ret = __read_ring(map->active.ring, &map->active.data,
+			  &msg->msg_iter, len, flags);
+
+	if (ret > 0)
+		notify_remote_via_irq(map->active.irq);
+	if (ret == 0)
+		ret = (flags & MSG_DONTWAIT) ? -EAGAIN : 0;
+	if (ret == -ENOTCONN)
+		ret = 0;
+
+	mutex_unlock(&map->active.in_mutex);
+	pvcalls_exit_sock(sock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pvcalls_front_recvmsg);
+
+int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map = NULL;
+	struct xen_pvcalls_request *req;
+	int notify, req_id, ret;
+
+	if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
+		return -EOPNOTSUPP;
+
+	map = pvcalls_enter_sock(sock);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	spin_lock(&bedata->socket_lock);
+	ret = get_request(bedata, &req_id);
+	if (ret < 0) {
+		spin_unlock(&bedata->socket_lock);
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	map->sock = sock;
+	req->cmd = PVCALLS_BIND;
+	req->u.bind.id = (uintptr_t)map;
+	memcpy(req->u.bind.addr, addr, sizeof(*addr));
+	req->u.bind.len = addr_len;
+
+	init_waitqueue_head(&map->passive.inflight_accept_req);
+
+	map->active_socket = false;
+
+	bedata->ring.req_prod_pvt++;
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
+	spin_unlock(&bedata->socket_lock);
+	if (notify)
+		notify_remote_via_irq(bedata->irq);
+
+	ret = pvcalls_front_wait_rsp(bedata, req_id);
+	if (ret) {
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+
+	/* read req_id, then the content */
+	smp_rmb();
+	ret = bedata->rsp[req_id].ret;
+	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
+
+	map->passive.status = PVCALLS_STATUS_BIND;
+	pvcalls_exit_sock(sock);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pvcalls_front_bind);
+
+int pvcalls_front_listen(struct socket *sock, int backlog)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map;
+	struct xen_pvcalls_request *req;
+	int notify, req_id, ret;
+
+	map = pvcalls_enter_sock(sock);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	if (map->passive.status != PVCALLS_STATUS_BIND) {
+		pvcalls_exit_sock(sock);
+		return -EOPNOTSUPP;
+	}
+
+	spin_lock(&bedata->socket_lock);
+	ret = get_request(bedata, &req_id);
+	if (ret < 0) {
+		spin_unlock(&bedata->socket_lock);
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	req->cmd = PVCALLS_LISTEN;
+	req->u.listen.id = (uintptr_t) map;
+	req->u.listen.backlog = backlog;
+
+	bedata->ring.req_prod_pvt++;
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
+	spin_unlock(&bedata->socket_lock);
+	if (notify)
+		notify_remote_via_irq(bedata->irq);
+
+	ret = pvcalls_front_wait_rsp(bedata, req_id);
+	if (ret) {
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+
+	/* read req_id, then the content */
+	smp_rmb();
+	ret = bedata->rsp[req_id].ret;
+	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
+
+	map->passive.status = PVCALLS_STATUS_LISTEN;
+	pvcalls_exit_sock(sock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pvcalls_front_listen);
+
+int pvcalls_front_accept(struct socket *sock, struct socket *newsock,
+			 struct proto_accept_arg *arg)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map;
+	struct sock_mapping *map2 = NULL;
+	struct xen_pvcalls_request *req;
+	int notify, req_id, ret, nonblock;
+	evtchn_port_t evtchn;
+
+	map = pvcalls_enter_sock(sock);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	if (map->passive.status != PVCALLS_STATUS_LISTEN) {
+		pvcalls_exit_sock(sock);
+		return -EINVAL;
+	}
+
+	nonblock = arg->flags & SOCK_NONBLOCK;
+	/*
+	 * Backend only supports 1 inflight accept request, will return
+	 * errors for the others
+	 */
+	if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+			     (void *)&map->passive.flags)) {
+		req_id = READ_ONCE(map->passive.inflight_req_id);
+		if (req_id != PVCALLS_INVALID_ID &&
+		    READ_ONCE(bedata->rsp[req_id].req_id) == req_id) {
+			map2 = map->passive.accept_map;
+			goto received;
+		}
+		if (nonblock) {
+			pvcalls_exit_sock(sock);
+			return -EAGAIN;
+		}
+		if (wait_event_interruptible(map->passive.inflight_accept_req,
+			!test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+					  (void *)&map->passive.flags))) {
+			pvcalls_exit_sock(sock);
+			return -EINTR;
+		}
+	}
+
+	if (READ_ONCE(bedata->disabled)) {
+		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+			  (void *)&map->passive.flags);
+		wake_up(&map->passive.inflight_accept_req);
+		pvcalls_exit_sock(sock);
+		return -EIO;
+	}
+
+	map2 = kzalloc_obj(*map2);
+	if (map2 == NULL) {
+		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+			  (void *)&map->passive.flags);
+		pvcalls_exit_sock(sock);
+		return -ENOMEM;
+	}
+	ret = alloc_active_ring(map2);
+	if (ret < 0) {
+		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+				(void *)&map->passive.flags);
+		kfree(map2);
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+	ret = create_active(map2, &evtchn);
+	if (ret < 0) {
+		free_active_ring(map2);
+		kfree(map2);
+		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+			  (void *)&map->passive.flags);
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+
+	spin_lock(&bedata->socket_lock);
+	ret = get_request(bedata, &req_id);
+	if (ret < 0) {
+		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+			  (void *)&map->passive.flags);
+		spin_unlock(&bedata->socket_lock);
+		pvcalls_front_free_map(bedata, map2);
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+
+	list_add_tail(&map2->list, &bedata->socket_mappings);
+
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	req->cmd = PVCALLS_ACCEPT;
+	req->u.accept.id = (uintptr_t) map;
+	req->u.accept.ref = map2->active.ref;
+	req->u.accept.id_new = (uintptr_t) map2;
+	req->u.accept.evtchn = evtchn;
+	map->passive.accept_map = map2;
+
+	bedata->ring.req_prod_pvt++;
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
+	spin_unlock(&bedata->socket_lock);
+	if (notify)
+		notify_remote_via_irq(bedata->irq);
+	/* We could check if we have received a response before returning. */
+	if (nonblock) {
+		WRITE_ONCE(map->passive.inflight_req_id, req_id);
+		pvcalls_exit_sock(sock);
+		return -EAGAIN;
+	}
+
+	if (wait_event_interruptible(bedata->inflight_req,
+		READ_ONCE(bedata->rsp[req_id].req_id) == req_id ||
+		READ_ONCE(bedata->disabled))) {
+		pvcalls_exit_sock(sock);
+		return -EINTR;
+	}
+	if (READ_ONCE(bedata->disabled)) {
+		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+			  (void *)&map->passive.flags);
+		wake_up(&map->passive.inflight_accept_req);
+		pvcalls_exit_sock(sock);
+		return -EIO;
+	}
+	/* read req_id, then the content */
+	smp_rmb();
+
+received:
+	map2->sock = newsock;
+	newsock->sk = sk_alloc(sock_net(sock->sk), PF_INET, GFP_KERNEL, &pvcalls_proto, false);
+	if (!newsock->sk) {
+		bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
+		map->passive.inflight_req_id = PVCALLS_INVALID_ID;
+		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+			  (void *)&map->passive.flags);
+		pvcalls_front_free_map(bedata, map2);
+		pvcalls_exit_sock(sock);
+		return -ENOMEM;
+	}
+	newsock->sk->sk_send_head = (void *)map2;
+
+	ret = bedata->rsp[req_id].ret;
+	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
+	map->passive.inflight_req_id = PVCALLS_INVALID_ID;
+
+	clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
+	wake_up(&map->passive.inflight_accept_req);
+
+	pvcalls_exit_sock(sock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pvcalls_front_accept);
+
+static __poll_t pvcalls_front_poll_passive(struct file *file,
+					       struct pvcalls_bedata *bedata,
+					       struct sock_mapping *map,
+					       poll_table *wait)
+{
+	int notify, req_id, ret;
+	struct xen_pvcalls_request *req;
+
+	if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+		     (void *)&map->passive.flags)) {
+		uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
+
+		if (req_id != PVCALLS_INVALID_ID &&
+		    READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
+			return EPOLLIN | EPOLLRDNORM;
+
+		poll_wait(file, &map->passive.inflight_accept_req, wait);
+		return 0;
+	}
+
+	if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
+			       (void *)&map->passive.flags))
+		return EPOLLIN | EPOLLRDNORM;
+
+	/*
+	 * First check RET, then INFLIGHT. No barriers necessary to
+	 * ensure execution ordering because of the conditional
+	 * instructions creating control dependencies.
+	 */
+
+	if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
+			     (void *)&map->passive.flags)) {
+		poll_wait(file, &bedata->inflight_req, wait);
+		return 0;
+	}
+
+	spin_lock(&bedata->socket_lock);
+	ret = get_request(bedata, &req_id);
+	if (ret < 0) {
+		spin_unlock(&bedata->socket_lock);
+		return ret;
+	}
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	req->cmd = PVCALLS_POLL;
+	req->u.poll.id = (uintptr_t) map;
+
+	bedata->ring.req_prod_pvt++;
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
+	spin_unlock(&bedata->socket_lock);
+	if (notify)
+		notify_remote_via_irq(bedata->irq);
+
+	poll_wait(file, &bedata->inflight_req, wait);
+	return 0;
+}
+
+static __poll_t pvcalls_front_poll_active(struct file *file,
+					      struct pvcalls_bedata *bedata,
+					      struct sock_mapping *map,
+					      poll_table *wait)
+{
+	__poll_t mask = 0;
+	int32_t in_error, out_error;
+	struct pvcalls_data_intf *intf = map->active.ring;
+
+	out_error = intf->out_error;
+	in_error = intf->in_error;
+
+	poll_wait(file, &map->active.inflight_conn_req, wait);
+	if (pvcalls_front_write_todo(map))
+		mask |= EPOLLOUT | EPOLLWRNORM;
+	if (pvcalls_front_read_todo(map))
+		mask |= EPOLLIN | EPOLLRDNORM;
+	if (in_error != 0 || out_error != 0)
+		mask |= EPOLLERR;
+
+	return mask;
+}
+
+__poll_t pvcalls_front_poll(struct file *file, struct socket *sock,
+			       poll_table *wait)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map;
+	__poll_t ret;
+
+	map = pvcalls_enter_sock(sock);
+	if (IS_ERR(map))
+		return EPOLLNVAL;
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	if (map->active_socket)
+		ret = pvcalls_front_poll_active(file, bedata, map, wait);
+	else
+		ret = pvcalls_front_poll_passive(file, bedata, map, wait);
+	pvcalls_exit_sock(sock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pvcalls_front_poll);
+
+int pvcalls_front_release(struct socket *sock)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map;
+	int req_id, notify, ret;
+	struct xen_pvcalls_request *req;
+
+	if (sock->sk == NULL)
+		return 0;
+
+	map = pvcalls_enter_sock(sock);
+	if (IS_ERR(map)) {
+		if (PTR_ERR(map) == -ENOTCONN)
+			return -EIO;
+		else
+			return 0;
+	}
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	spin_lock(&bedata->socket_lock);
+	ret = get_request(bedata, &req_id);
+	if (ret < 0) {
+		spin_unlock(&bedata->socket_lock);
+		pvcalls_exit_sock(sock);
+		return ret;
+	}
+	sock->sk->sk_send_head = NULL;
+
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	req->cmd = PVCALLS_RELEASE;
+	req->u.release.id = (uintptr_t)map;
+
+	bedata->ring.req_prod_pvt++;
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
+	spin_unlock(&bedata->socket_lock);
+	if (notify)
+		notify_remote_via_irq(bedata->irq);
+
+	wait_event(bedata->inflight_req,
+		   READ_ONCE(bedata->rsp[req_id].req_id) == req_id ||
+		   READ_ONCE(bedata->disabled));
+
+	if (map->active_socket) {
+		/*
+		 * Set in_error and wake up inflight_conn_req to force
+		 * recvmsg waiters to exit.
+		 */
+		map->active.ring->in_error = -EBADF;
+		wake_up_interruptible(&map->active.inflight_conn_req);
+
+		/*
+		 * We need to make sure that sendmsg/recvmsg on this socket have
+		 * not started before we've cleared sk_send_head here. The
+		 * easiest way to guarantee this is to see that no pvcalls
+		 * (other than us) is in progress on this socket.
+		 */
+		while (atomic_read(&map->refcount) > 1)
+			cpu_relax();
+
+		pvcalls_front_free_map(bedata, map);
+	} else {
+		wake_up(&bedata->inflight_req);
+		wake_up(&map->passive.inflight_accept_req);
+
+		while (atomic_read(&map->refcount) > 1)
+			cpu_relax();
+
+		spin_lock(&bedata->socket_lock);
+		list_del(&map->list);
+		spin_unlock(&bedata->socket_lock);
+		if (READ_ONCE(map->passive.inflight_req_id) != PVCALLS_INVALID_ID &&
+			READ_ONCE(map->passive.inflight_req_id) != 0) {
+			pvcalls_front_free_map(bedata,
+					       map->passive.accept_map);
+		}
+		kfree(map);
+	}
+	WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
+
+	pvcalls_exit();
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pvcalls_front_release);
+
+static const struct xenbus_device_id pvcalls_front_ids[] = {
+	{ "pvcalls" },
+	{ "" }
+};
+
+static void pvcalls_front_remove(struct xenbus_device *dev)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map = NULL, *n;
+
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+	dev_set_drvdata(&dev->dev, NULL);
+	pvcalls_front_dev = NULL;
+	if (bedata->irq >= 0)
+		unbind_from_irqhandler(bedata->irq, dev);
+
+	list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
+		map->sock->sk->sk_send_head = NULL;
+		if (map->active_socket) {
+			map->active.ring->in_error = -EBADF;
+			wake_up_interruptible(&map->active.inflight_conn_req);
+		}
+	}
+
+	smp_mb();
+	while (atomic_read(&pvcalls_refcount) > 0)
+		cpu_relax();
+	list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
+		if (map->active_socket) {
+			/* No need to lock, refcount is 0 */
+			pvcalls_front_free_map(bedata, map);
+		} else {
+			list_del(&map->list);
+			kfree(map);
+		}
+	}
+	if (bedata->ref != -1)
+		gnttab_end_foreign_access(bedata->ref, NULL);
+	kfree(bedata->ring.sring);
+	kfree(bedata);
+	xenbus_switch_state(dev, XenbusStateClosed);
+}
+
+static int pvcalls_front_probe(struct xenbus_device *dev,
+			  const struct xenbus_device_id *id)
+{
+	int ret = -ENOMEM, i;
+	evtchn_port_t evtchn;
+	unsigned int max_page_order, function_calls, len;
+	char *versions;
+	grant_ref_t gref_head = 0;
+	struct xenbus_transaction xbt;
+	struct pvcalls_bedata *bedata = NULL;
+	struct xen_pvcalls_sring *sring;
+
+	if (pvcalls_front_dev != NULL) {
+		dev_err(&dev->dev, "only one PV Calls connection supported\n");
+		return -EINVAL;
+	}
+
+	versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
+	if (IS_ERR(versions))
+		return PTR_ERR(versions);
+	if (!len)
+		return -EINVAL;
+	if (strcmp(versions, "1")) {
+		kfree(versions);
+		return -EINVAL;
+	}
+	kfree(versions);
+	max_page_order = xenbus_read_unsigned(dev->otherend,
+					      "max-page-order", 0);
+	if (max_page_order < PVCALLS_RING_ORDER)
+		return -ENODEV;
+	function_calls = xenbus_read_unsigned(dev->otherend,
+					      "function-calls", 0);
+	/* See XENBUS_FUNCTIONS_CALLS in pvcalls.h */
+	if (function_calls != 1)
+		return -ENODEV;
+	pr_info("%s max-page-order is %u\n", __func__, max_page_order);
+
+	bedata = kzalloc_obj(struct pvcalls_bedata);
+	if (!bedata)
+		return -ENOMEM;
+
+	dev_set_drvdata(&dev->dev, bedata);
+	pvcalls_front_dev = dev;
+	init_waitqueue_head(&bedata->inflight_req);
+	INIT_LIST_HEAD(&bedata->socket_mappings);
+	spin_lock_init(&bedata->socket_lock);
+	bedata->irq = -1;
+	bedata->ref = -1;
+
+	for (i = 0; i < PVCALLS_NR_RSP_PER_RING; i++)
+		bedata->rsp[i].req_id = PVCALLS_INVALID_ID;
+
+	sring = (struct xen_pvcalls_sring *) __get_free_page(GFP_KERNEL |
+							     __GFP_ZERO);
+	if (!sring)
+		goto error;
+	SHARED_RING_INIT(sring);
+	FRONT_RING_INIT(&bedata->ring, sring, XEN_PAGE_SIZE);
+
+	ret = xenbus_alloc_evtchn(dev, &evtchn);
+	if (ret)
+		goto error;
+
+	bedata->irq = bind_evtchn_to_irqhandler(evtchn,
+						pvcalls_front_event_handler,
+						0, "pvcalls-frontend", dev);
+	if (bedata->irq < 0) {
+		ret = bedata->irq;
+		goto error;
+	}
+
+	ret = gnttab_alloc_grant_references(1, &gref_head);
+	if (ret < 0)
+		goto error;
+	ret = gnttab_claim_grant_reference(&gref_head);
+	if (ret < 0)
+		goto error;
+	bedata->ref = ret;
+	gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
+					virt_to_gfn((void *)sring), 0);
+
+ again:
+	ret = xenbus_transaction_start(&xbt);
+	if (ret) {
+		xenbus_dev_fatal(dev, ret, "starting transaction");
+		goto error;
+	}
+	ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
+	if (ret)
+		goto error_xenbus;
+	ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", bedata->ref);
+	if (ret)
+		goto error_xenbus;
+	ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
+			    evtchn);
+	if (ret)
+		goto error_xenbus;
+	ret = xenbus_transaction_end(xbt, 0);
+	if (ret) {
+		if (ret == -EAGAIN)
+			goto again;
+		xenbus_dev_fatal(dev, ret, "completing transaction");
+		goto error;
+	}
+	xenbus_switch_state(dev, XenbusStateInitialised);
+
+	return 0;
+
+ error_xenbus:
+	xenbus_transaction_end(xbt, 1);
+	xenbus_dev_fatal(dev, ret, "writing xenstore");
+ error:
+	pvcalls_front_remove(dev);
+	return ret;
+}
+
+static void pvcalls_front_changed(struct xenbus_device *dev,
+			    enum xenbus_state backend_state)
+{
+	switch (backend_state) {
+	case XenbusStateReconfiguring:
+	case XenbusStateReconfigured:
+	case XenbusStateInitialising:
+	case XenbusStateInitialised:
+	case XenbusStateUnknown:
+		break;
+
+	case XenbusStateInitWait:
+		break;
+
+	case XenbusStateConnected:
+		xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosed:
+		if (dev->state == XenbusStateClosed)
+			break;
+		/* Missed the backend's CLOSING state */
+		fallthrough;
+	case XenbusStateClosing:
+		xenbus_frontend_closed(dev);
+		break;
+	}
+}
+
+static struct xenbus_driver pvcalls_front_driver = {
+	.ids = pvcalls_front_ids,
+	.probe = pvcalls_front_probe,
+	.remove = pvcalls_front_remove,
+	.otherend_changed = pvcalls_front_changed,
+	.not_essential = true,
+};
+
+static int __init pvcalls_frontend_init(void)
+{
+	if (!xen_domain())
+		return -ENODEV;
+
+	pr_info("Initialising Xen pvcalls frontend driver\n");
+
+	return xenbus_register_frontend(&pvcalls_front_driver);
+}
+
+module_init(pvcalls_frontend_init);
+
+MODULE_DESCRIPTION("Xen PV Calls frontend driver");
+MODULE_AUTHOR("Stefano Stabellini <sstabellini@kernel.org>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h
new file mode 100644
index 000000000..881ef1466
--- /dev/null
+++ b/drivers/xen/pvcalls-front.h
@@ -0,0 +1,28 @@
+#ifndef __PVCALLS_FRONT_H__
+#define __PVCALLS_FRONT_H__
+
+#include <linux/net.h>
+
+int pvcalls_front_socket(struct socket *sock);
+int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
+			  int addr_len, int flags);
+int pvcalls_front_bind(struct socket *sock,
+		       struct sockaddr *addr,
+		       int addr_len);
+int pvcalls_front_listen(struct socket *sock, int backlog);
+int pvcalls_front_accept(struct socket *sock,
+			 struct socket *newsock,
+			 struct proto_accept_arg *arg);
+int pvcalls_front_sendmsg(struct socket *sock,
+			  struct msghdr *msg,
+			  size_t len);
+int pvcalls_front_recvmsg(struct socket *sock,
+			  struct msghdr *msg,
+			  size_t len,
+			  int flags);
+__poll_t pvcalls_front_poll(struct file *file,
+				struct socket *sock,
+				poll_table *wait);
+int pvcalls_front_release(struct socket *sock);
+
+#endif
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
new file mode 100644
index 000000000..e2538824e
--- /dev/null
+++ b/drivers/xen/swiotlb-xen.c
@@ -0,0 +1,452 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Copyright 2010
+ *  by Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
+ *
+ * This code provides a IOMMU for Xen PV guests with PCI passthrough.
+ *
+ * PV guests under Xen are running in an non-contiguous memory architecture.
+ *
+ * When PCI pass-through is utilized, this necessitates an IOMMU for
+ * translating bus (DMA) to virtual and vice-versa and also providing a
+ * mechanism to have contiguous pages for device drivers operations (say DMA
+ * operations).
+ *
+ * Specifically, under Xen the Linux idea of pages is an illusion. It
+ * assumes that pages start at zero and go up to the available memory. To
+ * help with that, the Linux Xen MMU provides a lookup mechanism to
+ * translate the page frame numbers (PFN) to machine frame numbers (MFN)
+ * and vice-versa. The MFN are the "real" frame numbers. Furthermore
+ * memory is not contiguous. Xen hypervisor stitches memory for guests
+ * from different pools, which means there is no guarantee that PFN==MFN
+ * and PFN+1==MFN+1. Lastly with Xen 4.0, pages (in debug mode) are
+ * allocated in descending order (high to low), meaning the guest might
+ * never get any MFN's under the 4GB mark.
+ */
+
+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/memblock.h>
+#include <linux/dma-direct.h>
+#include <linux/dma-map-ops.h>
+#include <linux/export.h>
+#include <xen/swiotlb-xen.h>
+#include <xen/page.h>
+#include <xen/xen-ops.h>
+#include <xen/hvc-console.h>
+
+#include <asm/dma-mapping.h>
+
+#include <trace/events/swiotlb.h>
+#define MAX_DMA_BITS 32
+
+/*
+ * Quick lookup value of the bus address of the IOTLB.
+ */
+
+static inline phys_addr_t xen_phys_to_bus(struct device *dev, phys_addr_t paddr)
+{
+	unsigned long bfn = pfn_to_bfn(XEN_PFN_DOWN(paddr));
+	phys_addr_t baddr = (phys_addr_t)bfn << XEN_PAGE_SHIFT;
+
+	baddr |= paddr & ~XEN_PAGE_MASK;
+	return baddr;
+}
+
+static inline dma_addr_t xen_phys_to_dma(struct device *dev, phys_addr_t paddr)
+{
+	return phys_to_dma(dev, xen_phys_to_bus(dev, paddr));
+}
+
+static inline phys_addr_t xen_bus_to_phys(struct device *dev,
+					  phys_addr_t baddr)
+{
+	unsigned long xen_pfn = bfn_to_pfn(XEN_PFN_DOWN(baddr));
+	phys_addr_t paddr = (xen_pfn << XEN_PAGE_SHIFT) |
+			    (baddr & ~XEN_PAGE_MASK);
+
+	return paddr;
+}
+
+static inline phys_addr_t xen_dma_to_phys(struct device *dev,
+					  dma_addr_t dma_addr)
+{
+	return xen_bus_to_phys(dev, dma_to_phys(dev, dma_addr));
+}
+
+static inline bool range_requires_alignment(phys_addr_t p, size_t size)
+{
+	phys_addr_t algn = 1ULL << (get_order(size) + PAGE_SHIFT);
+	phys_addr_t bus_addr = pfn_to_bfn(XEN_PFN_DOWN(p)) << XEN_PAGE_SHIFT;
+
+	return IS_ALIGNED(p, algn) && !IS_ALIGNED(bus_addr, algn);
+}
+
+static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
+{
+	unsigned long next_bfn, xen_pfn = XEN_PFN_DOWN(p);
+	unsigned int i, nr_pages = XEN_PFN_UP(xen_offset_in_page(p) + size);
+
+	next_bfn = pfn_to_bfn(xen_pfn);
+
+	for (i = 1; i < nr_pages; i++)
+		if (pfn_to_bfn(++xen_pfn) != ++next_bfn)
+			return 1;
+
+	return 0;
+}
+
+static struct io_tlb_pool *xen_swiotlb_find_pool(struct device *dev,
+						 dma_addr_t dma_addr)
+{
+	unsigned long bfn = XEN_PFN_DOWN(dma_to_phys(dev, dma_addr));
+	unsigned long xen_pfn = bfn_to_local_pfn(bfn);
+	phys_addr_t paddr = (phys_addr_t)xen_pfn << XEN_PAGE_SHIFT;
+
+	/* If the address is outside our domain, it CAN
+	 * have the same virtual address as another address
+	 * in our domain. Therefore _only_ check address within our domain.
+	 */
+	if (pfn_valid(PFN_DOWN(paddr)))
+		return swiotlb_find_pool(dev, paddr);
+	return NULL;
+}
+
+#ifdef CONFIG_X86
+int __init xen_swiotlb_fixup(void *buf, unsigned long nslabs)
+{
+	int rc;
+	unsigned int order = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT);
+	unsigned int i, dma_bits = order + PAGE_SHIFT;
+	dma_addr_t dma_handle;
+	phys_addr_t p = virt_to_phys(buf);
+
+	BUILD_BUG_ON(IO_TLB_SEGSIZE & (IO_TLB_SEGSIZE - 1));
+	BUG_ON(nslabs % IO_TLB_SEGSIZE);
+
+	i = 0;
+	do {
+		do {
+			rc = xen_create_contiguous_region(
+				p + (i << IO_TLB_SHIFT), order,
+				dma_bits, &dma_handle);
+		} while (rc && dma_bits++ < MAX_DMA_BITS);
+		if (rc)
+			return rc;
+
+		i += IO_TLB_SEGSIZE;
+	} while (i < nslabs);
+	return 0;
+}
+
+static void *
+xen_swiotlb_alloc_coherent(struct device *dev, size_t size,
+		dma_addr_t *dma_handle, gfp_t flags, unsigned long attrs)
+{
+	u64 dma_mask = dev->coherent_dma_mask;
+	int order = get_order(size);
+	phys_addr_t phys;
+	void *ret;
+
+	/* Align the allocation to the Xen page size */
+	size = ALIGN(size, XEN_PAGE_SIZE);
+
+	ret = (void *)__get_free_pages(flags, get_order(size));
+	if (!ret)
+		return ret;
+	phys = virt_to_phys(ret);
+
+	*dma_handle = xen_phys_to_dma(dev, phys);
+	if (*dma_handle + size - 1 > dma_mask ||
+	    range_straddles_page_boundary(phys, size) ||
+	    range_requires_alignment(phys, size)) {
+		if (xen_create_contiguous_region(phys, order, fls64(dma_mask),
+				dma_handle) != 0)
+			goto out_free_pages;
+		SetPageXenRemapped(virt_to_page(ret));
+	}
+
+	memset(ret, 0, size);
+	return ret;
+
+out_free_pages:
+	free_pages((unsigned long)ret, get_order(size));
+	return NULL;
+}
+
+static void
+xen_swiotlb_free_coherent(struct device *dev, size_t size, void *vaddr,
+		dma_addr_t dma_handle, unsigned long attrs)
+{
+	phys_addr_t phys = virt_to_phys(vaddr);
+	int order = get_order(size);
+
+	/* Convert the size to actually allocated. */
+	size = ALIGN(size, XEN_PAGE_SIZE);
+
+	if (WARN_ON_ONCE(dma_handle + size - 1 > dev->coherent_dma_mask) ||
+	    WARN_ON_ONCE(range_straddles_page_boundary(phys, size) ||
+			 range_requires_alignment(phys, size)))
+	    	return;
+
+	if (TestClearPageXenRemapped(virt_to_page(vaddr)))
+		xen_destroy_contiguous_region(phys, order);
+	free_pages((unsigned long)vaddr, get_order(size));
+}
+#endif /* CONFIG_X86 */
+
+/*
+ * Map a single buffer of the indicated size for DMA in streaming mode.  The
+ * physical address to use is returned.
+ *
+ * Once the device is given the dma address, the device owns this memory until
+ * either xen_swiotlb_unmap_phys or xen_swiotlb_dma_sync_single is performed.
+ */
+static dma_addr_t xen_swiotlb_map_phys(struct device *dev, phys_addr_t phys,
+				size_t size, enum dma_data_direction dir,
+				unsigned long attrs)
+{
+	dma_addr_t dev_addr;
+	phys_addr_t map;
+
+	BUG_ON(dir == DMA_NONE);
+
+	if (attrs & DMA_ATTR_MMIO) {
+		if (unlikely(!dma_capable(dev, phys, size, false, attrs))) {
+			dev_err_once(
+				dev,
+				"DMA addr %pa+%zu overflow (mask %llx, bus limit %llx).\n",
+				&phys, size, *dev->dma_mask,
+				dev->bus_dma_limit);
+			WARN_ON_ONCE(1);
+			return DMA_MAPPING_ERROR;
+		}
+		return phys;
+	}
+
+	dev_addr = xen_phys_to_dma(dev, phys);
+
+	/*
+	 * If the address happens to be in the device's DMA window,
+	 * we can safely return the device addr and not worry about bounce
+	 * buffering it.
+	 */
+	if (dma_capable(dev, dev_addr, size, true, attrs) &&
+	    !dma_kmalloc_needs_bounce(dev, size, dir) &&
+	    !range_straddles_page_boundary(phys, size) &&
+		!xen_arch_need_swiotlb(dev, phys, dev_addr) &&
+		!is_swiotlb_force_bounce(dev))
+		goto done;
+
+	/*
+	 * Oh well, have to allocate and map a bounce buffer.
+	 */
+	trace_swiotlb_bounced(dev, dev_addr, size);
+
+	map = swiotlb_tbl_map_single(dev, phys, size, 0, dir, &attrs);
+	if (map == (phys_addr_t)DMA_MAPPING_ERROR)
+		return DMA_MAPPING_ERROR;
+
+	phys = map;
+	dev_addr = xen_phys_to_dma(dev, map);
+
+	/*
+	 * Ensure that the address returned is DMA'ble
+	 */
+	if (unlikely(!dma_capable(dev, dev_addr, size, true, attrs))) {
+		__swiotlb_tbl_unmap_single(dev, map, size, dir,
+				attrs | DMA_ATTR_SKIP_CPU_SYNC,
+				swiotlb_find_pool(dev, map));
+		return DMA_MAPPING_ERROR;
+	}
+
+done:
+	if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
+		if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dev_addr)))) {
+			arch_sync_dma_for_device(phys, size, dir);
+			arch_sync_dma_flush();
+		} else {
+			xen_dma_sync_for_device(dev, dev_addr, size, dir);
+		}
+	}
+	return dev_addr;
+}
+
+/*
+ * Unmap a single streaming mode DMA translation.  The dma_addr and size must
+ * match what was provided for in a previous xen_swiotlb_map_phys call.  All
+ * other usages are undefined.
+ *
+ * After this call, reads by the cpu to the buffer are guaranteed to see
+ * whatever the device wrote there.
+ */
+static void xen_swiotlb_unmap_phys(struct device *hwdev, dma_addr_t dev_addr,
+		size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+	phys_addr_t paddr = xen_dma_to_phys(hwdev, dev_addr);
+	struct io_tlb_pool *pool;
+
+	BUG_ON(dir == DMA_NONE);
+
+	if (!dev_is_dma_coherent(hwdev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
+		if (pfn_valid(PFN_DOWN(dma_to_phys(hwdev, dev_addr)))) {
+			arch_sync_dma_for_cpu(paddr, size, dir);
+			arch_sync_dma_flush();
+		} else {
+			xen_dma_sync_for_cpu(hwdev, dev_addr, size, dir);
+		}
+	}
+
+	/* NOTE: We use dev_addr here, not paddr! */
+	pool = xen_swiotlb_find_pool(hwdev, dev_addr);
+	if (pool)
+		__swiotlb_tbl_unmap_single(hwdev, paddr, size, dir,
+					   attrs, pool);
+}
+
+static void
+xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
+		size_t size, enum dma_data_direction dir)
+{
+	phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);
+	struct io_tlb_pool *pool;
+
+	if (!dev_is_dma_coherent(dev)) {
+		if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr)))) {
+			arch_sync_dma_for_cpu(paddr, size, dir);
+			arch_sync_dma_flush();
+		} else {
+			xen_dma_sync_for_cpu(dev, dma_addr, size, dir);
+		}
+	}
+
+	pool = xen_swiotlb_find_pool(dev, dma_addr);
+	if (pool)
+		__swiotlb_sync_single_for_cpu(dev, paddr, size, dir, pool);
+}
+
+static void
+xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
+		size_t size, enum dma_data_direction dir)
+{
+	phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);
+	struct io_tlb_pool *pool;
+
+	pool = xen_swiotlb_find_pool(dev, dma_addr);
+	if (pool)
+		__swiotlb_sync_single_for_device(dev, paddr, size, dir, pool);
+
+	if (!dev_is_dma_coherent(dev)) {
+		if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr)))) {
+			arch_sync_dma_for_device(paddr, size, dir);
+			arch_sync_dma_flush();
+		} else {
+			xen_dma_sync_for_device(dev, dma_addr, size, dir);
+		}
+	}
+}
+
+/*
+ * Unmap a set of streaming mode DMA translations.  Again, cpu read rules
+ * concerning calls here are the same as for xen_swiotlb_unmap_phys() above.
+ */
+static void
+xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
+		enum dma_data_direction dir, unsigned long attrs)
+{
+	struct scatterlist *sg;
+	int i;
+
+	BUG_ON(dir == DMA_NONE);
+
+	for_each_sg(sgl, sg, nelems, i)
+		xen_swiotlb_unmap_phys(hwdev, sg->dma_address, sg_dma_len(sg),
+				dir, attrs);
+
+}
+
+static int
+xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
+		enum dma_data_direction dir, unsigned long attrs)
+{
+	struct scatterlist *sg;
+	int i;
+
+	BUG_ON(dir == DMA_NONE);
+
+	for_each_sg(sgl, sg, nelems, i) {
+		sg->dma_address = xen_swiotlb_map_phys(dev, sg_phys(sg),
+				sg->length, dir, attrs);
+		if (sg->dma_address == DMA_MAPPING_ERROR)
+			goto out_unmap;
+		sg_dma_len(sg) = sg->length;
+	}
+
+	return nelems;
+out_unmap:
+	xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
+	sg_dma_len(sgl) = 0;
+	return -EIO;
+}
+
+static void
+xen_swiotlb_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
+			    int nelems, enum dma_data_direction dir)
+{
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgl, sg, nelems, i) {
+		xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address,
+				sg->length, dir);
+	}
+}
+
+static void
+xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
+			       int nelems, enum dma_data_direction dir)
+{
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgl, sg, nelems, i) {
+		xen_swiotlb_sync_single_for_device(dev, sg->dma_address,
+				sg->length, dir);
+	}
+}
+
+/*
+ * Return whether the given device DMA address mask can be supported
+ * properly.  For example, if your device can only drive the low 24-bits
+ * during bus mastering, then you would pass 0x00ffffff as the mask to
+ * this function.
+ */
+static int
+xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
+{
+	return xen_phys_to_dma(hwdev, default_swiotlb_limit()) <= mask;
+}
+
+const struct dma_map_ops xen_swiotlb_dma_ops = {
+#ifdef CONFIG_X86
+	.alloc = xen_swiotlb_alloc_coherent,
+	.free = xen_swiotlb_free_coherent,
+#else
+	.alloc = dma_direct_alloc,
+	.free = dma_direct_free,
+#endif
+	.sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu,
+	.sync_single_for_device = xen_swiotlb_sync_single_for_device,
+	.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
+	.sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
+	.map_sg = xen_swiotlb_map_sg,
+	.unmap_sg = xen_swiotlb_unmap_sg,
+	.map_phys = xen_swiotlb_map_phys,
+	.unmap_phys = xen_swiotlb_unmap_phys,
+	.dma_supported = xen_swiotlb_dma_supported,
+	.mmap = dma_common_mmap,
+	.get_sgtable = dma_common_get_sgtable,
+	.alloc_pages_op = dma_common_alloc_pages,
+	.free_pages = dma_common_free_pages,
+	.max_mapping_size = swiotlb_max_mapping_size,
+};
diff --git a/drivers/xen/sys-hypervisor.c b/drivers/xen/sys-hypervisor.c
new file mode 100644
index 000000000..91923242a
--- /dev/null
+++ b/drivers/xen/sys-hypervisor.c
@@ -0,0 +1,674 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  copyright (c) 2006 IBM Corporation
+ *  Authored by: Mike D. Day <ncmike@us.ibm.com>
+ */
+
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/kobject.h>
+#include <linux/err.h>
+
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/version.h>
+#ifdef CONFIG_XEN_HAVE_VPMU
+#include <xen/interface/xenpmu.h>
+#endif
+
+#define HYPERVISOR_ATTR_RO(_name) \
+static struct hyp_sysfs_attr _name##_attr = __ATTR_RO(_name)
+
+#define HYPERVISOR_ATTR_RW(_name) \
+static struct hyp_sysfs_attr _name##_attr = __ATTR_RW(_name)
+
+struct hyp_sysfs_attr {
+	struct attribute attr;
+	ssize_t (*show)(struct hyp_sysfs_attr *, char *);
+	ssize_t (*store)(struct hyp_sysfs_attr *, const char *, size_t);
+	union {
+		void *hyp_attr_data;
+		unsigned long hyp_attr_value;
+	};
+};
+
+static ssize_t type_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	return sprintf(buffer, "xen\n");
+}
+
+HYPERVISOR_ATTR_RO(type);
+
+static int __init xen_sysfs_type_init(void)
+{
+	return sysfs_create_file(hypervisor_kobj, &type_attr.attr);
+}
+
+static ssize_t guest_type_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	const char *type;
+
+	switch (xen_domain_type) {
+	case XEN_NATIVE:
+		/* ARM only. */
+		type = "Xen";
+		break;
+	case XEN_PV_DOMAIN:
+		type = "PV";
+		break;
+	case XEN_HVM_DOMAIN:
+		type = xen_pvh_domain() ? "PVH" : "HVM";
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return sprintf(buffer, "%s\n", type);
+}
+
+HYPERVISOR_ATTR_RO(guest_type);
+
+static int __init xen_sysfs_guest_type_init(void)
+{
+	return sysfs_create_file(hypervisor_kobj, &guest_type_attr.attr);
+}
+
+/* xen version attributes */
+static ssize_t major_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int version = HYPERVISOR_xen_version(XENVER_version, NULL);
+	if (version)
+		return sprintf(buffer, "%d\n", version >> 16);
+	return -ENODEV;
+}
+
+HYPERVISOR_ATTR_RO(major);
+
+static ssize_t minor_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int version = HYPERVISOR_xen_version(XENVER_version, NULL);
+	if (version)
+		return sprintf(buffer, "%d\n", version & 0xff);
+	return -ENODEV;
+}
+
+HYPERVISOR_ATTR_RO(minor);
+
+static ssize_t extra_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret = -ENOMEM;
+	char *extra;
+
+	extra = kmalloc(XEN_EXTRAVERSION_LEN, GFP_KERNEL);
+	if (extra) {
+		ret = HYPERVISOR_xen_version(XENVER_extraversion, extra);
+		if (!ret)
+			ret = sprintf(buffer, "%s\n", extra);
+		kfree(extra);
+	}
+
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(extra);
+
+static struct attribute *version_attrs[] = {
+	&major_attr.attr,
+	&minor_attr.attr,
+	&extra_attr.attr,
+	NULL
+};
+
+static const struct attribute_group version_group = {
+	.name = "version",
+	.attrs = version_attrs,
+};
+
+static int __init xen_sysfs_version_init(void)
+{
+	return sysfs_create_group(hypervisor_kobj, &version_group);
+}
+
+/* UUID */
+
+static ssize_t uuid_show_fallback(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	char *vm, *val;
+	int ret;
+	extern int xenstored_ready;
+
+	if (!xenstored_ready)
+		return -EBUSY;
+
+	vm = xenbus_read(XBT_NIL, "vm", "", NULL);
+	if (IS_ERR(vm))
+		return PTR_ERR(vm);
+	val = xenbus_read(XBT_NIL, vm, "uuid", NULL);
+	kfree(vm);
+	if (IS_ERR(val))
+		return PTR_ERR(val);
+	ret = sprintf(buffer, "%s\n", val);
+	kfree(val);
+	return ret;
+}
+
+static ssize_t uuid_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	xen_domain_handle_t uuid;
+	int ret;
+	ret = HYPERVISOR_xen_version(XENVER_guest_handle, uuid);
+	if (ret)
+		return uuid_show_fallback(attr, buffer);
+	ret = sprintf(buffer, "%pU\n", uuid);
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(uuid);
+
+static int __init xen_sysfs_uuid_init(void)
+{
+	return sysfs_create_file(hypervisor_kobj, &uuid_attr.attr);
+}
+
+/* xen compilation attributes */
+
+static ssize_t compiler_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret = -ENOMEM;
+	struct xen_compile_info *info;
+
+	info = kmalloc_obj(struct xen_compile_info);
+	if (info) {
+		ret = HYPERVISOR_xen_version(XENVER_compile_info, info);
+		if (!ret)
+			ret = sprintf(buffer, "%s\n", info->compiler);
+		kfree(info);
+	}
+
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(compiler);
+
+static ssize_t compiled_by_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret = -ENOMEM;
+	struct xen_compile_info *info;
+
+	info = kmalloc_obj(struct xen_compile_info);
+	if (info) {
+		ret = HYPERVISOR_xen_version(XENVER_compile_info, info);
+		if (!ret)
+			ret = sprintf(buffer, "%s\n", info->compile_by);
+		kfree(info);
+	}
+
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(compiled_by);
+
+static ssize_t compile_date_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret = -ENOMEM;
+	struct xen_compile_info *info;
+
+	info = kmalloc_obj(struct xen_compile_info);
+	if (info) {
+		ret = HYPERVISOR_xen_version(XENVER_compile_info, info);
+		if (!ret)
+			ret = sprintf(buffer, "%s\n", info->compile_date);
+		kfree(info);
+	}
+
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(compile_date);
+
+static struct attribute *xen_compile_attrs[] = {
+	&compiler_attr.attr,
+	&compiled_by_attr.attr,
+	&compile_date_attr.attr,
+	NULL
+};
+
+static const struct attribute_group xen_compilation_group = {
+	.name = "compilation",
+	.attrs = xen_compile_attrs,
+};
+
+static int __init xen_sysfs_compilation_init(void)
+{
+	return sysfs_create_group(hypervisor_kobj, &xen_compilation_group);
+}
+
+/* xen properties info */
+
+static ssize_t capabilities_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret = -ENOMEM;
+	char *caps;
+
+	caps = kmalloc(XEN_CAPABILITIES_INFO_LEN, GFP_KERNEL);
+	if (caps) {
+		ret = HYPERVISOR_xen_version(XENVER_capabilities, caps);
+		if (!ret)
+			ret = sprintf(buffer, "%s\n", caps);
+		kfree(caps);
+	}
+
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(capabilities);
+
+static ssize_t changeset_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret = -ENOMEM;
+	char *cset;
+
+	cset = kmalloc(XEN_CHANGESET_INFO_LEN, GFP_KERNEL);
+	if (cset) {
+		ret = HYPERVISOR_xen_version(XENVER_changeset, cset);
+		if (!ret)
+			ret = sprintf(buffer, "%s\n", cset);
+		kfree(cset);
+	}
+
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(changeset);
+
+static ssize_t virtual_start_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret = -ENOMEM;
+	struct xen_platform_parameters *parms;
+
+	parms = kmalloc_obj(struct xen_platform_parameters);
+	if (parms) {
+		ret = HYPERVISOR_xen_version(XENVER_platform_parameters,
+					     parms);
+		if (!ret)
+			ret = sprintf(buffer, "%"PRI_xen_ulong"\n",
+				      parms->virt_start);
+		kfree(parms);
+	}
+
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(virtual_start);
+
+static ssize_t pagesize_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret;
+
+	ret = HYPERVISOR_xen_version(XENVER_pagesize, NULL);
+	if (ret > 0)
+		ret = sprintf(buffer, "%x\n", ret);
+
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(pagesize);
+
+static ssize_t xen_feature_show(int index, char *buffer)
+{
+	ssize_t ret;
+	struct xen_feature_info info;
+
+	info.submap_idx = index;
+	ret = HYPERVISOR_xen_version(XENVER_get_features, &info);
+	if (!ret)
+		ret = sprintf(buffer, "%08x", info.submap);
+
+	return ret;
+}
+
+static ssize_t features_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	ssize_t len;
+	int i;
+
+	len = 0;
+	for (i = XENFEAT_NR_SUBMAPS-1; i >= 0; i--) {
+		int ret = xen_feature_show(i, buffer + len);
+		if (ret < 0) {
+			if (len == 0)
+				len = ret;
+			break;
+		}
+		len += ret;
+	}
+	if (len > 0)
+		buffer[len++] = '\n';
+
+	return len;
+}
+
+HYPERVISOR_ATTR_RO(features);
+
+static ssize_t buildid_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	ssize_t ret;
+	struct xen_build_id *buildid;
+
+	ret = HYPERVISOR_xen_version(XENVER_build_id, NULL);
+	if (ret < 0) {
+		if (ret == -EPERM)
+			ret = sprintf(buffer, "<denied>");
+		return ret;
+	}
+	if (ret > PAGE_SIZE)
+		return -ENOSPC;
+
+	buildid = kmalloc(sizeof(*buildid) + ret, GFP_KERNEL);
+	if (!buildid)
+		return -ENOMEM;
+
+	buildid->len = ret;
+	ret = HYPERVISOR_xen_version(XENVER_build_id, buildid);
+	if (ret > 0) {
+		/* Build id is binary, not a string. */
+		memcpy(buffer, buildid->buf, ret);
+	}
+	kfree(buildid);
+
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(buildid);
+
+static struct attribute *xen_properties_attrs[] = {
+	&capabilities_attr.attr,
+	&changeset_attr.attr,
+	&virtual_start_attr.attr,
+	&pagesize_attr.attr,
+	&features_attr.attr,
+	&buildid_attr.attr,
+	NULL
+};
+
+static const struct attribute_group xen_properties_group = {
+	.name = "properties",
+	.attrs = xen_properties_attrs,
+};
+
+static int __init xen_sysfs_properties_init(void)
+{
+	return sysfs_create_group(hypervisor_kobj, &xen_properties_group);
+}
+
+#define FLAG_UNAME "unknown"
+#define FLAG_UNAME_FMT FLAG_UNAME "%02u"
+#define FLAG_UNAME_MAX sizeof(FLAG_UNAME "XX")
+#define FLAG_COUNT (sizeof(xen_start_flags) * BITS_PER_BYTE)
+static_assert(sizeof(xen_start_flags) <=
+	      sizeof_field(struct hyp_sysfs_attr, hyp_attr_value));
+
+static ssize_t flag_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	char *p = buffer;
+
+	*p++ = '0' + ((xen_start_flags & attr->hyp_attr_value) != 0);
+	*p++ = '\n';
+	return p - buffer;
+}
+
+#define FLAG_NODE(flag, node)				\
+	[ilog2(flag)] = {				\
+		.attr = { .name = #node, .mode = 0444 },\
+		.show = flag_show,			\
+		.hyp_attr_value = flag			\
+	}
+
+/*
+ * Add new, known flags here.  No other changes are required, but
+ * note that each known flag wastes one entry in flag_unames[].
+ * The code/complexity machinations to avoid this isn't worth it
+ * for a few entries, but keep it in mind.
+ */
+static struct hyp_sysfs_attr flag_attrs[FLAG_COUNT] = {
+	FLAG_NODE(SIF_PRIVILEGED, privileged),
+	FLAG_NODE(SIF_INITDOMAIN, initdomain)
+};
+static struct attribute_group xen_flags_group = {
+	.name = "start_flags",
+	.attrs = (struct attribute *[FLAG_COUNT + 1]){}
+};
+static char flag_unames[FLAG_COUNT][FLAG_UNAME_MAX];
+
+static int __init xen_sysfs_flags_init(void)
+{
+	for (unsigned fnum = 0; fnum != FLAG_COUNT; fnum++) {
+		if (likely(flag_attrs[fnum].attr.name == NULL)) {
+			sprintf(flag_unames[fnum], FLAG_UNAME_FMT, fnum);
+			flag_attrs[fnum].attr.name = flag_unames[fnum];
+			flag_attrs[fnum].attr.mode = 0444;
+			flag_attrs[fnum].show = flag_show;
+			flag_attrs[fnum].hyp_attr_value = 1 << fnum;
+		}
+		xen_flags_group.attrs[fnum] = &flag_attrs[fnum].attr;
+	}
+	return sysfs_create_group(hypervisor_kobj, &xen_flags_group);
+}
+
+#ifdef CONFIG_XEN_HAVE_VPMU
+struct pmu_mode {
+	const char *name;
+	uint32_t mode;
+};
+
+static struct pmu_mode pmu_modes[] = {
+	{"off", XENPMU_MODE_OFF},
+	{"self", XENPMU_MODE_SELF},
+	{"hv", XENPMU_MODE_HV},
+	{"all", XENPMU_MODE_ALL}
+};
+
+static ssize_t pmu_mode_store(struct hyp_sysfs_attr *attr,
+			      const char *buffer, size_t len)
+{
+	int ret;
+	struct xen_pmu_params xp;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(pmu_modes); i++) {
+		if (strncmp(buffer, pmu_modes[i].name, len - 1) == 0) {
+			xp.val = pmu_modes[i].mode;
+			break;
+		}
+	}
+
+	if (i == ARRAY_SIZE(pmu_modes))
+		return -EINVAL;
+
+	xp.version.maj = XENPMU_VER_MAJ;
+	xp.version.min = XENPMU_VER_MIN;
+	ret = HYPERVISOR_xenpmu_op(XENPMU_mode_set, &xp);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static ssize_t pmu_mode_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret;
+	struct xen_pmu_params xp;
+	int i;
+	uint32_t mode;
+
+	xp.version.maj = XENPMU_VER_MAJ;
+	xp.version.min = XENPMU_VER_MIN;
+	ret = HYPERVISOR_xenpmu_op(XENPMU_mode_get, &xp);
+	if (ret)
+		return ret;
+
+	mode = (uint32_t)xp.val;
+	for (i = 0; i < ARRAY_SIZE(pmu_modes); i++) {
+		if (mode == pmu_modes[i].mode)
+			return sprintf(buffer, "%s\n", pmu_modes[i].name);
+	}
+
+	return -EINVAL;
+}
+HYPERVISOR_ATTR_RW(pmu_mode);
+
+static ssize_t pmu_features_store(struct hyp_sysfs_attr *attr,
+				  const char *buffer, size_t len)
+{
+	int ret;
+	uint32_t features;
+	struct xen_pmu_params xp;
+
+	ret = kstrtou32(buffer, 0, &features);
+	if (ret)
+		return ret;
+
+	xp.val = features;
+	xp.version.maj = XENPMU_VER_MAJ;
+	xp.version.min = XENPMU_VER_MIN;
+	ret = HYPERVISOR_xenpmu_op(XENPMU_feature_set, &xp);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static ssize_t pmu_features_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	int ret;
+	struct xen_pmu_params xp;
+
+	xp.version.maj = XENPMU_VER_MAJ;
+	xp.version.min = XENPMU_VER_MIN;
+	ret = HYPERVISOR_xenpmu_op(XENPMU_feature_get, &xp);
+	if (ret)
+		return ret;
+
+	return sprintf(buffer, "0x%x\n", (uint32_t)xp.val);
+}
+HYPERVISOR_ATTR_RW(pmu_features);
+
+static struct attribute *xen_pmu_attrs[] = {
+	&pmu_mode_attr.attr,
+	&pmu_features_attr.attr,
+	NULL
+};
+
+static const struct attribute_group xen_pmu_group = {
+	.name = "pmu",
+	.attrs = xen_pmu_attrs,
+};
+
+static int __init xen_sysfs_pmu_init(void)
+{
+	return sysfs_create_group(hypervisor_kobj, &xen_pmu_group);
+}
+#endif
+
+static int __init hyper_sysfs_init(void)
+{
+	int ret;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	ret = xen_sysfs_type_init();
+	if (ret)
+		goto out;
+	ret = xen_sysfs_guest_type_init();
+	if (ret)
+		goto guest_type_out;
+	ret = xen_sysfs_version_init();
+	if (ret)
+		goto version_out;
+	ret = xen_sysfs_compilation_init();
+	if (ret)
+		goto comp_out;
+	ret = xen_sysfs_uuid_init();
+	if (ret)
+		goto uuid_out;
+	ret = xen_sysfs_properties_init();
+	if (ret)
+		goto prop_out;
+	ret = xen_sysfs_flags_init();
+	if (ret)
+		goto flags_out;
+#ifdef CONFIG_XEN_HAVE_VPMU
+	if (xen_initial_domain()) {
+		ret = xen_sysfs_pmu_init();
+		if (ret) {
+			sysfs_remove_group(hypervisor_kobj, &xen_flags_group);
+			goto flags_out;
+		}
+	}
+#endif
+	goto out;
+
+flags_out:
+	sysfs_remove_group(hypervisor_kobj, &xen_properties_group);
+prop_out:
+	sysfs_remove_file(hypervisor_kobj, &uuid_attr.attr);
+uuid_out:
+	sysfs_remove_group(hypervisor_kobj, &xen_compilation_group);
+comp_out:
+	sysfs_remove_group(hypervisor_kobj, &version_group);
+version_out:
+	sysfs_remove_file(hypervisor_kobj, &guest_type_attr.attr);
+guest_type_out:
+	sysfs_remove_file(hypervisor_kobj, &type_attr.attr);
+out:
+	return ret;
+}
+device_initcall(hyper_sysfs_init);
+
+static ssize_t hyp_sysfs_show(struct kobject *kobj,
+			      struct attribute *attr,
+			      char *buffer)
+{
+	struct hyp_sysfs_attr *hyp_attr;
+	hyp_attr = container_of(attr, struct hyp_sysfs_attr, attr);
+	if (hyp_attr->show)
+		return hyp_attr->show(hyp_attr, buffer);
+	return 0;
+}
+
+static ssize_t hyp_sysfs_store(struct kobject *kobj,
+			       struct attribute *attr,
+			       const char *buffer,
+			       size_t len)
+{
+	struct hyp_sysfs_attr *hyp_attr;
+	hyp_attr = container_of(attr, struct hyp_sysfs_attr, attr);
+	if (hyp_attr->store)
+		return hyp_attr->store(hyp_attr, buffer, len);
+	return 0;
+}
+
+static const struct sysfs_ops hyp_sysfs_ops = {
+	.show = hyp_sysfs_show,
+	.store = hyp_sysfs_store,
+};
+
+static const struct kobj_type hyp_sysfs_kobj_type = {
+	.sysfs_ops = &hyp_sysfs_ops,
+};
+
+static int __init hypervisor_subsys_init(void)
+{
+	if (!xen_domain())
+		return -ENODEV;
+
+	hypervisor_kobj->ktype = &hyp_sysfs_kobj_type;
+	return 0;
+}
+device_initcall(hypervisor_subsys_init);
diff --git a/drivers/xen/time.c b/drivers/xen/time.c
new file mode 100644
index 000000000..a2be0a4d4
--- /dev/null
+++ b/drivers/xen/time.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Xen stolen ticks accounting.
+ */
+#include <linux/kernel.h>
+#include <linux/kernel_stat.h>
+#include <linux/math64.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+#include <linux/static_call.h>
+#include <linux/sched/cputime.h>
+
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+
+#include <xen/events.h>
+#include <xen/features.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/vcpu.h>
+#include <xen/xen-ops.h>
+
+/* runstate info updated by Xen */
+static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
+
+static DEFINE_PER_CPU(u64[4], old_runstate_time);
+
+/* return an consistent snapshot of 64-bit time/counter value */
+static u64 get64(const u64 *p)
+{
+	u64 ret;
+
+	if (BITS_PER_LONG < 64) {
+		u32 *p32 = (u32 *)p;
+		u32 h, l, h2;
+
+		/*
+		 * Read high then low, and then make sure high is
+		 * still the same; this will only loop if low wraps
+		 * and carries into high.
+		 * XXX some clean way to make this endian-proof?
+		 */
+		do {
+			h = READ_ONCE(p32[1]);
+			l = READ_ONCE(p32[0]);
+			h2 = READ_ONCE(p32[1]);
+		} while(h2 != h);
+
+		ret = (((u64)h) << 32) | l;
+	} else
+		ret = READ_ONCE(*p);
+
+	return ret;
+}
+
+static void xen_get_runstate_snapshot_cpu_delta(
+			      struct vcpu_runstate_info *res, unsigned int cpu)
+{
+	u64 state_time;
+	struct vcpu_runstate_info *state;
+
+	BUG_ON(preemptible());
+
+	state = per_cpu_ptr(&xen_runstate, cpu);
+
+	do {
+		state_time = get64(&state->state_entry_time);
+		rmb();	/* Hypervisor might update data. */
+		*res = __READ_ONCE(*state);
+		rmb();	/* Hypervisor might update data. */
+	} while (get64(&state->state_entry_time) != state_time ||
+		 (state_time & XEN_RUNSTATE_UPDATE));
+}
+
+static void xen_get_runstate_snapshot_cpu(struct vcpu_runstate_info *res,
+					  unsigned int cpu)
+{
+	int i;
+
+	xen_get_runstate_snapshot_cpu_delta(res, cpu);
+
+	for (i = 0; i < 4; i++)
+		res->time[i] += per_cpu(old_runstate_time, cpu)[i];
+}
+
+void xen_manage_runstate_time(int action)
+{
+	static struct vcpu_runstate_info *runstate_delta;
+	struct vcpu_runstate_info state;
+	int cpu, i;
+
+	switch (action) {
+	case -1: /* backup runstate time before suspend */
+		if (unlikely(runstate_delta))
+			pr_warn_once("%s: memory leak as runstate_delta is not NULL\n",
+					__func__);
+
+		runstate_delta = kmalloc_objs(*runstate_delta,
+					      num_possible_cpus(), GFP_ATOMIC);
+		if (unlikely(!runstate_delta)) {
+			pr_warn("%s: failed to allocate runstate_delta\n",
+					__func__);
+			return;
+		}
+
+		for_each_possible_cpu(cpu) {
+			xen_get_runstate_snapshot_cpu_delta(&state, cpu);
+			memcpy(runstate_delta[cpu].time, state.time,
+					sizeof(runstate_delta[cpu].time));
+		}
+
+		break;
+
+	case 0: /* backup runstate time after resume */
+		if (unlikely(!runstate_delta)) {
+			pr_warn("%s: cannot accumulate runstate time as runstate_delta is NULL\n",
+					__func__);
+			return;
+		}
+
+		for_each_possible_cpu(cpu) {
+			for (i = 0; i < 4; i++)
+				per_cpu(old_runstate_time, cpu)[i] +=
+					runstate_delta[cpu].time[i];
+		}
+
+		break;
+
+	default: /* do not accumulate runstate time for checkpointing */
+		break;
+	}
+
+	if (action != -1 && runstate_delta) {
+		kfree(runstate_delta);
+		runstate_delta = NULL;
+	}
+}
+
+/* return true when a vcpu could run but has no real cpu to run on */
+bool xen_vcpu_stolen(int vcpu)
+{
+	return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
+}
+
+u64 xen_steal_clock(int cpu)
+{
+	struct vcpu_runstate_info state;
+
+	xen_get_runstate_snapshot_cpu(&state, cpu);
+	return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
+}
+
+void xen_setup_runstate_info(int cpu)
+{
+	struct vcpu_register_runstate_memory_area area;
+
+	area.addr.v = &per_cpu(xen_runstate, cpu);
+
+	if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
+			       xen_vcpu_nr(cpu), &area))
+		BUG();
+}
+
+void __init xen_time_setup_guest(void)
+{
+	bool xen_runstate_remote;
+
+	xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
+					VMASST_TYPE_runstate_update_flag);
+
+	static_call_update(pv_steal_clock, xen_steal_clock);
+
+	static_key_slow_inc(&paravirt_steal_enabled);
+	if (xen_runstate_remote)
+		static_key_slow_inc(&paravirt_steal_rq_enabled);
+}
diff --git a/drivers/xen/unpopulated-alloc.c b/drivers/xen/unpopulated-alloc.c
new file mode 100644
index 000000000..9cdabf184
--- /dev/null
+++ b/drivers/xen/unpopulated-alloc.c
@@ -0,0 +1,251 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/errno.h>
+#include <linux/gfp.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/memremap.h>
+#include <linux/slab.h>
+
+#include <asm/page.h>
+
+#include <xen/balloon.h>
+#include <xen/page.h>
+#include <xen/xen.h>
+
+static DEFINE_MUTEX(list_lock);
+static struct page *page_list;
+static unsigned int list_count;
+
+static struct resource *target_resource;
+
+/* Pages to subtract from the memory count when setting balloon target. */
+unsigned long xen_unpopulated_pages __initdata;
+
+/*
+ * If arch is not happy with system "iomem_resource" being used for
+ * the region allocation it can provide it's own view by creating specific
+ * Xen resource with unused regions of guest physical address space provided
+ * by the hypervisor.
+ */
+int __weak __init arch_xen_unpopulated_init(struct resource **res)
+{
+	*res = &iomem_resource;
+
+	return 0;
+}
+
+static int fill_list(unsigned int nr_pages)
+{
+	struct dev_pagemap *pgmap;
+	struct resource *res, *tmp_res = NULL;
+	void *vaddr;
+	unsigned int i, alloc_pages = round_up(nr_pages, PAGES_PER_SECTION);
+	struct range mhp_range;
+	int ret;
+
+	res = kzalloc_obj(*res);
+	if (!res)
+		return -ENOMEM;
+
+	res->name = "Xen scratch";
+	res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+
+	mhp_range = mhp_get_pluggable_range(true);
+
+	ret = allocate_resource(target_resource, res,
+				alloc_pages * PAGE_SIZE, mhp_range.start, mhp_range.end,
+				PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
+	if (ret < 0) {
+		pr_err("Cannot allocate new IOMEM resource\n");
+		goto err_resource;
+	}
+
+	/*
+	 * Reserve the region previously allocated from Xen resource to avoid
+	 * re-using it by someone else.
+	 */
+	if (target_resource != &iomem_resource) {
+		tmp_res = kzalloc_obj(*tmp_res);
+		if (!tmp_res) {
+			ret = -ENOMEM;
+			goto err_insert;
+		}
+
+		tmp_res->name = res->name;
+		tmp_res->start = res->start;
+		tmp_res->end = res->end;
+		tmp_res->flags = res->flags;
+
+		ret = request_resource(&iomem_resource, tmp_res);
+		if (ret < 0) {
+			pr_err("Cannot request resource %pR (%d)\n", tmp_res, ret);
+			kfree(tmp_res);
+			goto err_insert;
+		}
+	}
+
+	pgmap = kzalloc_obj(*pgmap);
+	if (!pgmap) {
+		ret = -ENOMEM;
+		goto err_pgmap;
+	}
+
+	pgmap->type = MEMORY_DEVICE_GENERIC;
+	pgmap->range = (struct range) {
+		.start = res->start,
+		.end = res->end,
+	};
+	pgmap->nr_range = 1;
+	pgmap->owner = res;
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+        /*
+         * memremap will build page tables for the new memory so
+         * the p2m must contain invalid entries so the correct
+         * non-present PTEs will be written.
+         *
+         * If a failure occurs, the original (identity) p2m entries
+         * are not restored since this region is now known not to
+         * conflict with any devices.
+         */
+	if (xen_pv_domain()) {
+		xen_pfn_t pfn = PFN_DOWN(res->start);
+
+		for (i = 0; i < alloc_pages; i++) {
+			if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
+				pr_warn("set_phys_to_machine() failed, no memory added\n");
+				ret = -ENOMEM;
+				goto err_memremap;
+			}
+                }
+	}
+#endif
+
+	vaddr = memremap_pages(pgmap, NUMA_NO_NODE);
+	if (IS_ERR(vaddr)) {
+		pr_err("Cannot remap memory range\n");
+		ret = PTR_ERR(vaddr);
+		goto err_memremap;
+	}
+
+	for (i = 0; i < alloc_pages; i++) {
+		struct page *pg = virt_to_page(vaddr + PAGE_SIZE * i);
+
+		pg->zone_device_data = page_list;
+		page_list = pg;
+		list_count++;
+	}
+
+	return 0;
+
+err_memremap:
+	kfree(pgmap);
+err_pgmap:
+	if (tmp_res) {
+		release_resource(tmp_res);
+		kfree(tmp_res);
+	}
+err_insert:
+	release_resource(res);
+err_resource:
+	kfree(res);
+	return ret;
+}
+
+/**
+ * xen_alloc_unpopulated_pages - alloc unpopulated pages
+ * @nr_pages: Number of pages
+ * @pages: pages returned
+ * @return 0 on success, error otherwise
+ */
+int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages)
+{
+	unsigned int i;
+	int ret = 0;
+
+	/*
+	 * Fallback to default behavior if we do not have any suitable resource
+	 * to allocate required region from and as the result we won't be able to
+	 * construct pages.
+	 */
+	if (!target_resource)
+		return xen_alloc_ballooned_pages(nr_pages, pages);
+
+	mutex_lock(&list_lock);
+	if (list_count < nr_pages) {
+		ret = fill_list(nr_pages - list_count);
+		if (ret)
+			goto out;
+	}
+
+	for (i = 0; i < nr_pages; i++) {
+		struct page *pg = page_list;
+
+		BUG_ON(!pg);
+		page_list = pg->zone_device_data;
+		list_count--;
+		pages[i] = pg;
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+		if (xen_pv_domain()) {
+			ret = xen_alloc_p2m_entry(page_to_pfn(pg));
+			if (ret < 0) {
+				unsigned int j;
+
+				for (j = 0; j <= i; j++) {
+					pages[j]->zone_device_data = page_list;
+					page_list = pages[j];
+					list_count++;
+				}
+				goto out;
+			}
+		}
+#endif
+	}
+
+out:
+	mutex_unlock(&list_lock);
+	return ret;
+}
+EXPORT_SYMBOL(xen_alloc_unpopulated_pages);
+
+/**
+ * xen_free_unpopulated_pages - return unpopulated pages
+ * @nr_pages: Number of pages
+ * @pages: pages to return
+ */
+void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages)
+{
+	unsigned int i;
+
+	if (!target_resource) {
+		xen_free_ballooned_pages(nr_pages, pages);
+		return;
+	}
+
+	mutex_lock(&list_lock);
+	for (i = 0; i < nr_pages; i++) {
+		pages[i]->zone_device_data = page_list;
+		page_list = pages[i];
+		list_count++;
+	}
+	mutex_unlock(&list_lock);
+}
+EXPORT_SYMBOL(xen_free_unpopulated_pages);
+
+static int __init unpopulated_init(void)
+{
+	int ret;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	ret = arch_xen_unpopulated_init(&target_resource);
+	if (ret) {
+		pr_err("xen:unpopulated: Cannot initialize target resource\n");
+		target_resource = NULL;
+	}
+
+	return ret;
+}
+early_initcall(unpopulated_init);
diff --git a/drivers/xen/xen-acpi-pad.c b/drivers/xen/xen-acpi-pad.c
new file mode 100644
index 000000000..2fa9c7d35
--- /dev/null
+++ b/drivers/xen/xen-acpi-pad.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * xen-acpi-pad.c - Xen pad interface
+ *
+ * Copyright (c) 2012, Intel Corporation.
+ *    Author: Liu, Jinsong <jinsong.liu@intel.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/acpi.h>
+#include <linux/platform_device.h>
+#include <xen/xen.h>
+#include <xen/interface/version.h>
+#include <xen/xen-ops.h>
+#include <asm/xen/hypercall.h>
+
+#define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80
+static DEFINE_MUTEX(xen_cpu_lock);
+
+static int xen_acpi_pad_idle_cpus(unsigned int idle_nums)
+{
+	struct xen_platform_op op;
+
+	op.cmd = XENPF_core_parking;
+	op.u.core_parking.type = XEN_CORE_PARKING_SET;
+	op.u.core_parking.idle_nums = idle_nums;
+
+	return HYPERVISOR_platform_op(&op);
+}
+
+static int xen_acpi_pad_idle_cpus_num(void)
+{
+	struct xen_platform_op op;
+
+	op.cmd = XENPF_core_parking;
+	op.u.core_parking.type = XEN_CORE_PARKING_GET;
+
+	return HYPERVISOR_platform_op(&op)
+	       ?: op.u.core_parking.idle_nums;
+}
+
+/*
+ * Query firmware how many CPUs should be idle
+ * return -1 on failure
+ */
+static int acpi_pad_pur(acpi_handle handle)
+{
+	struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
+	union acpi_object *package;
+	int num = -1;
+
+	if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
+		return num;
+
+	if (!buffer.length || !buffer.pointer)
+		return num;
+
+	package = buffer.pointer;
+
+	if (package->type == ACPI_TYPE_PACKAGE &&
+		package->package.count == 2 &&
+		package->package.elements[0].integer.value == 1) /* rev 1 */
+		num = package->package.elements[1].integer.value;
+
+	kfree(buffer.pointer);
+	return num;
+}
+
+static void acpi_pad_handle_notify(acpi_handle handle)
+{
+	int idle_nums;
+	struct acpi_buffer param = {
+		.length = 4,
+		.pointer = (void *)&idle_nums,
+	};
+
+
+	mutex_lock(&xen_cpu_lock);
+	idle_nums = acpi_pad_pur(handle);
+	if (idle_nums < 0) {
+		mutex_unlock(&xen_cpu_lock);
+		return;
+	}
+
+	idle_nums = xen_acpi_pad_idle_cpus(idle_nums)
+		    ?: xen_acpi_pad_idle_cpus_num();
+	if (idle_nums >= 0)
+		acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY,
+				  0, &param);
+	mutex_unlock(&xen_cpu_lock);
+}
+
+static void acpi_pad_notify(acpi_handle handle, u32 event,
+	void *data)
+{
+	switch (event) {
+	case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
+		acpi_pad_handle_notify(handle);
+		break;
+	default:
+		pr_warn("Unsupported event [0x%x]\n", event);
+		break;
+	}
+}
+
+static int acpi_pad_probe(struct platform_device *pdev)
+{
+	struct acpi_device *device;
+	acpi_status status;
+
+	device = ACPI_COMPANION(&pdev->dev);
+	if (!device)
+		return -ENODEV;
+
+	status = acpi_install_notify_handler(device->handle,
+		ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	return 0;
+}
+
+static void acpi_pad_remove(struct platform_device *pdev)
+{
+	mutex_lock(&xen_cpu_lock);
+	xen_acpi_pad_idle_cpus(0);
+	mutex_unlock(&xen_cpu_lock);
+
+	acpi_remove_notify_handler(ACPI_HANDLE(&pdev->dev),
+		ACPI_DEVICE_NOTIFY, acpi_pad_notify);
+}
+
+static const struct acpi_device_id pad_device_ids[] = {
+	{"ACPI000C", 0},
+	{"", 0},
+};
+
+static struct platform_driver acpi_pad_driver = {
+	.probe = acpi_pad_probe,
+	.remove = acpi_pad_remove,
+	.driver = {
+		.name = "acpi_processor_aggregator",
+		.acpi_match_table = pad_device_ids,
+	},
+};
+
+static int __init xen_acpi_pad_init(void)
+{
+	/* Only DOM0 is responsible for Xen acpi pad */
+	if (!xen_initial_domain())
+		return -ENODEV;
+
+	/* Only Xen4.2 or later support Xen acpi pad */
+	if (!xen_running_on_version_or_later(4, 2))
+		return -ENODEV;
+
+	return platform_driver_register(&acpi_pad_driver);
+}
+subsys_initcall(xen_acpi_pad_init);
diff --git a/drivers/xen/xen-acpi-processor.c b/drivers/xen/xen-acpi-processor.c
new file mode 100644
index 000000000..897ae2a0b
--- /dev/null
+++ b/drivers/xen/xen-acpi-processor.c
@@ -0,0 +1,600 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2012 by Oracle Inc
+ * Author: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
+ *
+ * This code borrows ideas from
+ * https://lore.kernel.org/lkml/1322673664-14642-6-git-send-email-konrad.wilk@oracle.com
+ * so many thanks go to Kevin Tian <kevin.tian@intel.com>
+ * and Yu Ke <ke.yu@intel.com>.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/cpumask.h>
+#include <linux/cpufreq.h>
+#include <linux/freezer.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/syscore_ops.h>
+#include <linux/acpi.h>
+#include <acpi/processor.h>
+#include <xen/xen.h>
+#include <xen/interface/platform.h>
+#include <asm/xen/hypercall.h>
+
+static int no_hypercall;
+MODULE_PARM_DESC(off, "Inhibit the hypercall.");
+module_param_named(off, no_hypercall, int, 0400);
+
+/*
+ * Note: Do not convert the acpi_id* below to cpumask_var_t or use cpumask_bit
+ * - as those shrink to nr_cpu_bits (which is dependent on possible_cpu), which
+ * can be less than what we want to put in. Instead use the 'nr_acpi_bits'
+ * which is dynamically computed based on the MADT or x2APIC table.
+ */
+static unsigned int nr_acpi_bits;
+/* Mutex to protect the acpi_ids_done - for CPU hotplug use. */
+static DEFINE_MUTEX(acpi_ids_mutex);
+/* Which ACPI ID we have processed from 'struct acpi_processor'. */
+static unsigned long *acpi_ids_done;
+/* Which ACPI ID exist in the SSDT/DSDT processor definitions. */
+static unsigned long *acpi_id_present;
+/* And if there is an _CST definition (or a PBLK) for the ACPI IDs */
+static unsigned long *acpi_id_cst_present;
+/* Which ACPI P-State dependencies for a enumerated processor */
+static struct acpi_psd_package *acpi_psd;
+
+static int push_cxx_to_hypervisor(struct acpi_processor *_pr)
+{
+	struct xen_platform_op op = {
+		.cmd			= XENPF_set_processor_pminfo,
+		.interface_version	= XENPF_INTERFACE_VERSION,
+		.u.set_pminfo.id	= _pr->acpi_id,
+		.u.set_pminfo.type	= XEN_PM_CX,
+	};
+	struct xen_processor_cx *dst_cx, *dst_cx_states = NULL;
+	struct acpi_processor_cx *cx;
+	unsigned int i, ok;
+	int ret = 0;
+
+	dst_cx_states = kzalloc_objs(struct xen_processor_cx, _pr->power.count);
+	if (!dst_cx_states)
+		return -ENOMEM;
+
+	for (ok = 0, i = 1; i <= _pr->power.count; i++) {
+		cx = &_pr->power.states[i];
+		if (!cx->valid)
+			continue;
+
+		dst_cx = &(dst_cx_states[ok++]);
+
+		dst_cx->reg.space_id = ACPI_ADR_SPACE_SYSTEM_IO;
+		if (cx->entry_method == ACPI_CSTATE_SYSTEMIO) {
+			dst_cx->reg.bit_width = 8;
+			dst_cx->reg.bit_offset = 0;
+			dst_cx->reg.access_size = 1;
+		} else {
+			dst_cx->reg.space_id = ACPI_ADR_SPACE_FIXED_HARDWARE;
+			if (cx->entry_method == ACPI_CSTATE_FFH) {
+				/* NATIVE_CSTATE_BEYOND_HALT */
+				dst_cx->reg.bit_offset = 2;
+				dst_cx->reg.bit_width = 1; /* VENDOR_INTEL */
+			}
+			dst_cx->reg.access_size = 0;
+		}
+		dst_cx->reg.address = cx->address;
+
+		dst_cx->type = cx->type;
+		dst_cx->latency = cx->latency;
+
+		dst_cx->dpcnt = 0;
+		set_xen_guest_handle(dst_cx->dp, NULL);
+	}
+	if (!ok) {
+		pr_debug("No _Cx for ACPI CPU %u\n", _pr->acpi_id);
+		kfree(dst_cx_states);
+		return -EINVAL;
+	}
+	op.u.set_pminfo.power.count = ok;
+	op.u.set_pminfo.power.flags.bm_control = _pr->flags.bm_control;
+	op.u.set_pminfo.power.flags.bm_check = _pr->flags.bm_check;
+	op.u.set_pminfo.power.flags.has_cst = _pr->flags.has_cst;
+	op.u.set_pminfo.power.flags.power_setup_done =
+		_pr->flags.power_setup_done;
+
+	set_xen_guest_handle(op.u.set_pminfo.power.states, dst_cx_states);
+
+	if (!no_hypercall)
+		ret = HYPERVISOR_platform_op(&op);
+
+	if (!ret) {
+		pr_debug("ACPI CPU%u - C-states uploaded.\n", _pr->acpi_id);
+		for (i = 1; i <= _pr->power.count; i++) {
+			cx = &_pr->power.states[i];
+			if (!cx->valid)
+				continue;
+			pr_debug("     C%d: %s %d uS\n",
+				 cx->type, cx->desc, (u32)cx->latency);
+		}
+	} else if ((ret != -EINVAL) && (ret != -ENOSYS))
+		/* EINVAL means the ACPI ID is incorrect - meaning the ACPI
+		 * table is referencing a non-existing CPU - which can happen
+		 * with broken ACPI tables. */
+		pr_err("(CX): Hypervisor error (%d) for ACPI CPU%u\n",
+		       ret, _pr->acpi_id);
+
+	kfree(dst_cx_states);
+
+	return ret;
+}
+static struct xen_processor_px *
+xen_copy_pss_data(struct acpi_processor *_pr,
+		  struct xen_processor_performance *dst_perf)
+{
+	struct xen_processor_px *dst_states = NULL;
+	unsigned int i;
+
+	BUILD_BUG_ON(sizeof(struct xen_processor_px) !=
+		     sizeof(struct acpi_processor_px));
+
+	dst_states = kzalloc_objs(struct xen_processor_px,
+				  _pr->performance->state_count);
+	if (!dst_states)
+		return ERR_PTR(-ENOMEM);
+
+	dst_perf->state_count = _pr->performance->state_count;
+	for (i = 0; i < _pr->performance->state_count; i++) {
+		/* Fortunatly for us, they are both the same size */
+		memcpy(&(dst_states[i]), &(_pr->performance->states[i]),
+		       sizeof(struct acpi_processor_px));
+	}
+	return dst_states;
+}
+static int xen_copy_psd_data(struct acpi_processor *_pr,
+			     struct xen_processor_performance *dst)
+{
+	struct acpi_psd_package *pdomain;
+
+	BUILD_BUG_ON(sizeof(struct xen_psd_package) !=
+		     sizeof(struct acpi_psd_package));
+
+	/* This information is enumerated only if acpi_processor_preregister_performance
+	 * has been called.
+	 */
+	dst->shared_type = _pr->performance->shared_type;
+
+	pdomain = &(_pr->performance->domain_info);
+
+	/* 'acpi_processor_preregister_performance' does not parse if the
+	 * num_processors <= 1, but Xen still requires it. Do it manually here.
+	 */
+	if (pdomain->num_processors <= 1) {
+		if (pdomain->coord_type == DOMAIN_COORD_TYPE_SW_ALL)
+			dst->shared_type = CPUFREQ_SHARED_TYPE_ALL;
+		else if (pdomain->coord_type == DOMAIN_COORD_TYPE_HW_ALL)
+			dst->shared_type = CPUFREQ_SHARED_TYPE_HW;
+		else if (pdomain->coord_type == DOMAIN_COORD_TYPE_SW_ANY)
+			dst->shared_type = CPUFREQ_SHARED_TYPE_ANY;
+
+	}
+	memcpy(&(dst->domain_info), pdomain, sizeof(struct acpi_psd_package));
+	return 0;
+}
+static int xen_copy_pct_data(struct acpi_pct_register *pct,
+			     struct xen_pct_register *dst_pct)
+{
+	/* It would be nice if you could just do 'memcpy(pct, dst_pct') but
+	 * sadly the Xen structure did not have the proper padding so the
+	 * descriptor field takes two (dst_pct) bytes instead of one (pct).
+	 */
+	dst_pct->descriptor = pct->descriptor;
+	dst_pct->length = pct->length;
+	dst_pct->space_id = pct->space_id;
+	dst_pct->bit_width = pct->bit_width;
+	dst_pct->bit_offset = pct->bit_offset;
+	dst_pct->reserved = pct->reserved;
+	dst_pct->address = pct->address;
+	return 0;
+}
+static int push_pxx_to_hypervisor(struct acpi_processor *_pr)
+{
+	int ret = 0;
+	struct xen_platform_op op = {
+		.cmd			= XENPF_set_processor_pminfo,
+		.interface_version	= XENPF_INTERFACE_VERSION,
+		.u.set_pminfo.id	= _pr->acpi_id,
+		.u.set_pminfo.type	= XEN_PM_PX,
+	};
+	struct xen_processor_performance *dst_perf;
+	struct xen_processor_px *dst_states = NULL;
+
+	dst_perf = &op.u.set_pminfo.perf;
+
+	dst_perf->platform_limit = _pr->performance_platform_limit;
+	dst_perf->flags |= XEN_PX_PPC;
+	xen_copy_pct_data(&(_pr->performance->control_register),
+			  &dst_perf->control_register);
+	xen_copy_pct_data(&(_pr->performance->status_register),
+			  &dst_perf->status_register);
+	dst_perf->flags |= XEN_PX_PCT;
+	dst_states = xen_copy_pss_data(_pr, dst_perf);
+	if (!IS_ERR_OR_NULL(dst_states)) {
+		set_xen_guest_handle(dst_perf->states, dst_states);
+		dst_perf->flags |= XEN_PX_PSS;
+	}
+	if (!xen_copy_psd_data(_pr, dst_perf))
+		dst_perf->flags |= XEN_PX_PSD;
+
+	if (dst_perf->flags != (XEN_PX_PSD | XEN_PX_PSS | XEN_PX_PCT | XEN_PX_PPC)) {
+		pr_warn("ACPI CPU%u missing some P-state data (%x), skipping\n",
+			_pr->acpi_id, dst_perf->flags);
+		ret = -ENODEV;
+		goto err_free;
+	}
+
+	if (!no_hypercall)
+		ret = HYPERVISOR_platform_op(&op);
+
+	if (!ret) {
+		struct acpi_processor_performance *perf;
+		unsigned int i;
+
+		perf = _pr->performance;
+		pr_debug("ACPI CPU%u - P-states uploaded.\n", _pr->acpi_id);
+		for (i = 0; i < perf->state_count; i++) {
+			pr_debug("     %cP%d: %d MHz, %d mW, %d uS\n",
+			(i == perf->state ? '*' : ' '), i,
+			(u32) perf->states[i].core_frequency,
+			(u32) perf->states[i].power,
+			(u32) perf->states[i].transition_latency);
+		}
+	} else if ((ret != -EINVAL) && (ret != -ENOSYS))
+		/* EINVAL means the ACPI ID is incorrect - meaning the ACPI
+		 * table is referencing a non-existing CPU - which can happen
+		 * with broken ACPI tables. */
+		pr_warn("(_PXX): Hypervisor error (%d) for ACPI CPU%u\n",
+			ret, _pr->acpi_id);
+err_free:
+	if (!IS_ERR_OR_NULL(dst_states))
+		kfree(dst_states);
+
+	return ret;
+}
+static int upload_pm_data(struct acpi_processor *_pr)
+{
+	int err = 0;
+
+	mutex_lock(&acpi_ids_mutex);
+	if (__test_and_set_bit(_pr->acpi_id, acpi_ids_done)) {
+		mutex_unlock(&acpi_ids_mutex);
+		return -EBUSY;
+	}
+	if (_pr->flags.power)
+		err = push_cxx_to_hypervisor(_pr);
+
+	if (_pr->performance && _pr->performance->states)
+		err |= push_pxx_to_hypervisor(_pr);
+
+	mutex_unlock(&acpi_ids_mutex);
+	return err;
+}
+static unsigned int __init get_max_acpi_id(void)
+{
+	struct xenpf_pcpuinfo *info;
+	struct xen_platform_op op = {
+		.cmd = XENPF_get_cpuinfo,
+		.interface_version = XENPF_INTERFACE_VERSION,
+	};
+	int ret = 0;
+	unsigned int i, last_cpu, max_acpi_id = 0;
+
+	info = &op.u.pcpu_info;
+	info->xen_cpuid = 0;
+
+	ret = HYPERVISOR_platform_op(&op);
+	if (ret)
+		return NR_CPUS;
+
+	/* The max_present is the same irregardless of the xen_cpuid */
+	last_cpu = op.u.pcpu_info.max_present;
+	for (i = 0; i <= last_cpu; i++) {
+		info->xen_cpuid = i;
+		ret = HYPERVISOR_platform_op(&op);
+		if (ret)
+			continue;
+		max_acpi_id = max(info->acpi_id, max_acpi_id);
+	}
+	max_acpi_id *= 2; /* Slack for CPU hotplug support. */
+	pr_debug("Max ACPI ID: %u\n", max_acpi_id);
+	return max_acpi_id;
+}
+/*
+ * The read_acpi_id and check_acpi_ids are there to support the Xen
+ * oddity of virtual CPUs != physical CPUs in the initial domain.
+ * The user can supply 'xen_max_vcpus=X' on the Xen hypervisor line
+ * which will band the amount of CPUs the initial domain can see.
+ * In general that is OK, except it plays havoc with any of the
+ * for_each_[present|online]_cpu macros which are banded to the virtual
+ * CPU amount.
+ */
+static acpi_status
+read_acpi_id(acpi_handle handle, u32 lvl, void *context, void **rv)
+{
+	u32 acpi_id;
+	acpi_status status;
+	acpi_object_type acpi_type;
+	unsigned long long tmp;
+	union acpi_object object = { 0 };
+	struct acpi_buffer buffer = { sizeof(union acpi_object), &object };
+	acpi_io_address pblk = 0;
+
+	status = acpi_get_type(handle, &acpi_type);
+	if (ACPI_FAILURE(status))
+		return AE_OK;
+
+	switch (acpi_type) {
+	case ACPI_TYPE_PROCESSOR:
+		status = acpi_evaluate_object(handle, NULL, NULL, &buffer);
+		if (ACPI_FAILURE(status))
+			return AE_OK;
+		acpi_id = object.processor.proc_id;
+		pblk = object.processor.pblk_address;
+		break;
+	case ACPI_TYPE_DEVICE:
+		status = acpi_evaluate_integer(handle, "_UID", NULL, &tmp);
+		if (ACPI_FAILURE(status))
+			return AE_OK;
+		acpi_id = tmp;
+		break;
+	default:
+		return AE_OK;
+	}
+	if (invalid_phys_cpuid(acpi_get_phys_id(handle,
+						acpi_type == ACPI_TYPE_DEVICE,
+						acpi_id))) {
+		pr_debug("CPU with ACPI ID %u is unavailable\n", acpi_id);
+		return AE_OK;
+	}
+	/* There are more ACPI Processor objects than in x2APIC or MADT.
+	 * This can happen with incorrect ACPI SSDT declerations. */
+	if (acpi_id >= nr_acpi_bits) {
+		pr_debug("max acpi id %u, trying to set %u\n",
+			 nr_acpi_bits - 1, acpi_id);
+		return AE_OK;
+	}
+	/* OK, There is a ACPI Processor object */
+	__set_bit(acpi_id, acpi_id_present);
+
+	pr_debug("ACPI CPU%u w/ PBLK:0x%lx\n", acpi_id, (unsigned long)pblk);
+
+	/* It has P-state dependencies */
+	if (!acpi_processor_get_psd(handle, &acpi_psd[acpi_id])) {
+		pr_debug("ACPI CPU%u w/ PST:coord_type = %llu domain = %llu\n",
+			 acpi_id, acpi_psd[acpi_id].coord_type,
+			 acpi_psd[acpi_id].domain);
+	}
+
+	if (!pblk && !acpi_has_method(handle, "_CST"))
+		return AE_OK;
+	/* .. and it has a C-state */
+	__set_bit(acpi_id, acpi_id_cst_present);
+
+	return AE_OK;
+}
+static int check_acpi_ids(struct acpi_processor *pr_backup)
+{
+
+	if (!pr_backup)
+		return -ENODEV;
+
+	if (acpi_id_present && acpi_id_cst_present)
+		/* OK, done this once .. skip to uploading */
+		goto upload;
+
+	/* All online CPUs have been processed at this stage. Now verify
+	 * whether in fact "online CPUs" == physical CPUs.
+	 */
+	acpi_id_present = bitmap_zalloc(nr_acpi_bits, GFP_KERNEL);
+	if (!acpi_id_present)
+		return -ENOMEM;
+
+	acpi_id_cst_present = bitmap_zalloc(nr_acpi_bits, GFP_KERNEL);
+	if (!acpi_id_cst_present) {
+		bitmap_free(acpi_id_present);
+		return -ENOMEM;
+	}
+
+	acpi_psd = kzalloc_objs(struct acpi_psd_package, nr_acpi_bits);
+	if (!acpi_psd) {
+		bitmap_free(acpi_id_present);
+		bitmap_free(acpi_id_cst_present);
+		return -ENOMEM;
+	}
+
+	acpi_walk_namespace(ACPI_TYPE_PROCESSOR, ACPI_ROOT_OBJECT,
+			    ACPI_UINT32_MAX,
+			    read_acpi_id, NULL, NULL, NULL);
+	acpi_get_devices(ACPI_PROCESSOR_DEVICE_HID, read_acpi_id, NULL, NULL);
+
+upload:
+	if (!bitmap_equal(acpi_id_present, acpi_ids_done, nr_acpi_bits)) {
+		unsigned int i;
+		for_each_set_bit(i, acpi_id_present, nr_acpi_bits) {
+			pr_backup->acpi_id = i;
+			/* Mask out C-states if there are no _CST or PBLK */
+			pr_backup->flags.power = test_bit(i, acpi_id_cst_present);
+			/* num_entries is non-zero if we evaluated _PSD */
+			if (acpi_psd[i].num_entries) {
+				memcpy(&pr_backup->performance->domain_info,
+				       &acpi_psd[i],
+				       sizeof(struct acpi_psd_package));
+			}
+			(void)upload_pm_data(pr_backup);
+		}
+	}
+
+	return 0;
+}
+
+/* acpi_perf_data is a pointer to percpu data. */
+static struct acpi_processor_performance __percpu *acpi_perf_data;
+
+static void free_acpi_perf_data(void)
+{
+	int i;
+
+	/* Freeing a NULL pointer is OK, and alloc_percpu zeroes. */
+	for_each_possible_cpu(i)
+		free_cpumask_var(per_cpu_ptr(acpi_perf_data, i)
+				 ->shared_cpu_map);
+	free_percpu(acpi_perf_data);
+}
+
+static int xen_upload_processor_pm_data(void)
+{
+	struct acpi_processor *pr_backup = NULL;
+	int i;
+	int rc = 0;
+
+	pr_info("Uploading Xen processor PM info\n");
+
+	for_each_possible_cpu(i) {
+		struct acpi_processor *_pr;
+		_pr = per_cpu(processors, i /* APIC ID */);
+		if (!_pr)
+			continue;
+
+		if (!pr_backup)
+			pr_backup = kmemdup(_pr, sizeof(*_pr), GFP_KERNEL);
+		(void)upload_pm_data(_pr);
+	}
+
+	rc = check_acpi_ids(pr_backup);
+	kfree(pr_backup);
+
+	return rc;
+}
+
+static void xen_acpi_processor_resume_worker(struct work_struct *dummy)
+{
+	int rc;
+
+	bitmap_zero(acpi_ids_done, nr_acpi_bits);
+
+	rc = xen_upload_processor_pm_data();
+	if (rc != 0)
+		pr_info("ACPI data upload failed, error = %d\n", rc);
+}
+
+static void xen_acpi_processor_resume(void *data)
+{
+	static DECLARE_WORK(wq, xen_acpi_processor_resume_worker);
+
+	/*
+	 * xen_upload_processor_pm_data() calls non-atomic code.
+	 * However, the context for xen_acpi_processor_resume is syscore
+	 * with only the boot CPU online and in an atomic context.
+	 *
+	 * So defer the upload for some point safer.
+	 */
+	schedule_work(&wq);
+}
+
+static const struct syscore_ops xap_syscore_ops = {
+	.resume	= xen_acpi_processor_resume,
+};
+
+static struct syscore xap_syscore = {
+	.ops = &xap_syscore_ops,
+};
+
+static int __init xen_acpi_processor_init(void)
+{
+	int i;
+	int rc;
+
+	if (!xen_initial_domain())
+		return -ENODEV;
+
+	nr_acpi_bits = get_max_acpi_id() + 1;
+	acpi_ids_done = bitmap_zalloc(nr_acpi_bits, GFP_KERNEL);
+	if (!acpi_ids_done)
+		return -ENOMEM;
+
+	acpi_perf_data = alloc_percpu(struct acpi_processor_performance);
+	if (!acpi_perf_data) {
+		pr_debug("Memory allocation error for acpi_perf_data\n");
+		bitmap_free(acpi_ids_done);
+		return -ENOMEM;
+	}
+	for_each_possible_cpu(i) {
+		if (!zalloc_cpumask_var_node(
+			&per_cpu_ptr(acpi_perf_data, i)->shared_cpu_map,
+			GFP_KERNEL, cpu_to_node(i))) {
+			rc = -ENOMEM;
+			goto err_out;
+		}
+	}
+
+	/* Do initialization in ACPI core. It is OK to fail here. */
+	(void)acpi_processor_preregister_performance(acpi_perf_data);
+
+	for_each_possible_cpu(i) {
+		struct acpi_processor *pr;
+		struct acpi_processor_performance *perf;
+
+		pr = per_cpu(processors, i);
+		perf = per_cpu_ptr(acpi_perf_data, i);
+		if (!pr)
+			continue;
+
+		pr->performance = perf;
+		rc = acpi_processor_get_performance_info(pr);
+		if (rc)
+			goto err_out;
+	}
+
+	rc = xen_upload_processor_pm_data();
+	if (rc)
+		goto err_unregister;
+
+	register_syscore(&xap_syscore);
+
+	return 0;
+err_unregister:
+	for_each_possible_cpu(i)
+		acpi_processor_unregister_performance(i);
+
+err_out:
+	/* Freeing a NULL pointer is OK: alloc_percpu zeroes. */
+	free_acpi_perf_data();
+	bitmap_free(acpi_ids_done);
+	return rc;
+}
+static void __exit xen_acpi_processor_exit(void)
+{
+	int i;
+
+	unregister_syscore(&xap_syscore);
+	bitmap_free(acpi_ids_done);
+	bitmap_free(acpi_id_present);
+	bitmap_free(acpi_id_cst_present);
+	kfree(acpi_psd);
+	for_each_possible_cpu(i)
+		acpi_processor_unregister_performance(i);
+
+	free_acpi_perf_data();
+}
+
+MODULE_AUTHOR("Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>");
+MODULE_DESCRIPTION("Xen ACPI Processor P-states (and Cx) driver which uploads PM data to Xen hypervisor");
+MODULE_LICENSE("GPL");
+
+/* We want to be loaded before the CPU freq scaling drivers are loaded.
+ * They are loaded in late_initcall. */
+device_initcall(xen_acpi_processor_init);
+module_exit(xen_acpi_processor_exit);
diff --git a/drivers/xen/xen-balloon.c b/drivers/xen/xen-balloon.c
new file mode 100644
index 000000000..67b0e2dbe
--- /dev/null
+++ b/drivers/xen/xen-balloon.c
@@ -0,0 +1,264 @@
+/******************************************************************************
+ * Xen balloon driver - enables returning/claiming memory to/from Xen.
+ *
+ * Copyright (c) 2003, B Dragovic
+ * Copyright (c) 2003-2004, M Williamson, K Fraser
+ * Copyright (c) 2005 Dan M. Smith, IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/mm_types.h>
+#include <linux/init.h>
+#include <linux/capability.h>
+#include <linux/memory_hotplug.h>
+
+#include <xen/xen.h>
+#include <xen/interface/xen.h>
+#include <xen/balloon.h>
+#include <xen/xenbus.h>
+#include <xen/features.h>
+#include <xen/page.h>
+#include <xen/mem-reservation.h>
+
+#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
+
+#define BALLOON_CLASS_NAME "xen_memory"
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+u64 xen_saved_max_mem_size = 0;
+#endif
+
+static struct device balloon_dev;
+
+static int register_balloon(struct device *dev);
+
+/* React to a change in the target key */
+static void watch_target(struct xenbus_watch *watch,
+			 const char *path, const char *token)
+{
+	unsigned long long new_target, static_max;
+	int err;
+	static bool watch_fired;
+	static long target_diff;
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+	/* The balloon driver will take care of adding memory now. */
+	if (xen_saved_max_mem_size)
+		max_mem_size = xen_saved_max_mem_size;
+#endif
+
+	err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
+	if (err != 1) {
+		/* This is ok (for domain0 at least) - so just return */
+		return;
+	}
+
+	/* The given memory/target value is in KiB, so it needs converting to
+	 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
+	 */
+	new_target >>= PAGE_SHIFT - 10;
+
+	if (!watch_fired) {
+		watch_fired = true;
+
+		if ((xenbus_scanf(XBT_NIL, "memory", "static-max",
+				  "%llu", &static_max) == 1) ||
+		    (xenbus_scanf(XBT_NIL, "memory", "memory_static_max",
+				  "%llu", &static_max) == 1))
+			static_max >>= PAGE_SHIFT - 10;
+		else
+			static_max = balloon_stats.current_pages;
+
+		target_diff = (xen_pv_domain() || xen_initial_domain()) ? 0
+				: static_max - balloon_stats.target_pages;
+	}
+
+	balloon_set_new_target(new_target - target_diff);
+}
+static struct xenbus_watch target_watch = {
+	.node = "memory/target",
+	.callback = watch_target,
+};
+
+
+static int balloon_init_watcher(struct notifier_block *notifier,
+				unsigned long event,
+				void *data)
+{
+	int err;
+
+	err = register_xenbus_watch(&target_watch);
+	if (err)
+		pr_err("Failed to set balloon watcher\n");
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block xenstore_notifier = {
+	.notifier_call = balloon_init_watcher,
+};
+
+void xen_balloon_init(void)
+{
+	register_balloon(&balloon_dev);
+
+	register_xenstore_notifier(&xenstore_notifier);
+}
+EXPORT_SYMBOL_GPL(xen_balloon_init);
+
+#define BALLOON_SHOW(name, format, args...)				\
+	static ssize_t name##_show(struct device *dev,			\
+				   struct device_attribute *attr,	\
+				   char *buf)				\
+	{								\
+		return sysfs_emit(buf, format, ##args);			\
+	}								\
+	static DEVICE_ATTR_RO(name)
+
+BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
+BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
+BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
+
+static DEVICE_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
+static DEVICE_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
+static DEVICE_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
+static DEVICE_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
+static DEVICE_BOOL_ATTR(scrub_pages, 0644, xen_scrub_pages);
+
+static ssize_t target_kb_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	return sysfs_emit(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
+}
+
+static ssize_t target_kb_store(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t count)
+{
+	char *endchar;
+	unsigned long long target_bytes;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
+
+	balloon_set_new_target(target_bytes >> PAGE_SHIFT);
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(target_kb);
+
+static ssize_t target_show(struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	return sysfs_emit(buf, "%llu\n",
+		       (unsigned long long)balloon_stats.target_pages
+		       << PAGE_SHIFT);
+}
+
+static ssize_t target_store(struct device *dev,
+			    struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	char *endchar;
+	unsigned long long target_bytes;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	target_bytes = memparse(buf, &endchar);
+
+	balloon_set_new_target(target_bytes >> PAGE_SHIFT);
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(target);
+
+static struct attribute *balloon_attrs[] = {
+	&dev_attr_target_kb.attr,
+	&dev_attr_target.attr,
+	&dev_attr_schedule_delay.attr.attr,
+	&dev_attr_max_schedule_delay.attr.attr,
+	&dev_attr_retry_count.attr.attr,
+	&dev_attr_max_retry_count.attr.attr,
+	&dev_attr_scrub_pages.attr.attr,
+	NULL
+};
+
+static const struct attribute_group balloon_group = {
+	.attrs = balloon_attrs
+};
+
+static struct attribute *balloon_info_attrs[] = {
+	&dev_attr_current_kb.attr,
+	&dev_attr_low_kb.attr,
+	&dev_attr_high_kb.attr,
+	NULL
+};
+
+static const struct attribute_group balloon_info_group = {
+	.name = "info",
+	.attrs = balloon_info_attrs
+};
+
+static const struct attribute_group *balloon_groups[] = {
+	&balloon_group,
+	&balloon_info_group,
+	NULL
+};
+
+static const struct bus_type balloon_subsys = {
+	.name = BALLOON_CLASS_NAME,
+	.dev_name = BALLOON_CLASS_NAME,
+};
+
+static int register_balloon(struct device *dev)
+{
+	int error;
+
+	error = subsys_system_register(&balloon_subsys, NULL);
+	if (error)
+		return error;
+
+	dev->id = 0;
+	dev->bus = &balloon_subsys;
+	dev->groups = balloon_groups;
+
+	error = device_register(dev);
+	if (error) {
+		bus_unregister(&balloon_subsys);
+		return error;
+	}
+
+	return 0;
+}
diff --git a/drivers/xen/xen-front-pgdir-shbuf.c b/drivers/xen/xen-front-pgdir-shbuf.c
new file mode 100644
index 000000000..428187edf
--- /dev/null
+++ b/drivers/xen/xen-front-pgdir-shbuf.c
@@ -0,0 +1,553 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ * Xen frontend/backend page directory based shared buffer
+ * helper module.
+ *
+ * Copyright (C) 2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+
+#include <asm/xen/hypervisor.h>
+#include <xen/balloon.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/interface/io/ring.h>
+
+#include <xen/xen-front-pgdir-shbuf.h>
+
+/*
+ * This structure represents the structure of a shared page
+ * that contains grant references to the pages of the shared
+ * buffer. This structure is common to many Xen para-virtualized
+ * protocols at include/xen/interface/io/
+ */
+struct xen_page_directory {
+	grant_ref_t gref_dir_next_page;
+#define XEN_GREF_LIST_END	0
+	grant_ref_t gref[]; /* Variable length */
+};
+
+/*
+ * Shared buffer ops which are differently implemented
+ * depending on the allocation mode, e.g. if the buffer
+ * is allocated by the corresponding backend or frontend.
+ * Some of the operations.
+ */
+struct xen_front_pgdir_shbuf_ops {
+	/*
+	 * Calculate number of grefs required to handle this buffer,
+	 * e.g. if grefs are required for page directory only or the buffer
+	 * pages as well.
+	 */
+	void (*calc_num_grefs)(struct xen_front_pgdir_shbuf *buf);
+
+	/* Fill page directory according to para-virtual display protocol. */
+	void (*fill_page_dir)(struct xen_front_pgdir_shbuf *buf);
+
+	/* Claim grant references for the pages of the buffer. */
+	int (*grant_refs_for_buffer)(struct xen_front_pgdir_shbuf *buf,
+				     grant_ref_t *priv_gref_head, int gref_idx);
+
+	/* Map grant references of the buffer. */
+	int (*map)(struct xen_front_pgdir_shbuf *buf);
+
+	/* Unmap grant references of the buffer. */
+	int (*unmap)(struct xen_front_pgdir_shbuf *buf);
+};
+
+/*
+ * Get granted reference to the very first page of the
+ * page directory. Usually this is passed to the backend,
+ * so it can find/fill the grant references to the buffer's
+ * pages.
+ *
+ * \param buf shared buffer which page directory is of interest.
+ * \return granted reference to the very first page of the
+ * page directory.
+ */
+grant_ref_t
+xen_front_pgdir_shbuf_get_dir_start(struct xen_front_pgdir_shbuf *buf)
+{
+	if (!buf->grefs)
+		return INVALID_GRANT_REF;
+
+	return buf->grefs[0];
+}
+EXPORT_SYMBOL_GPL(xen_front_pgdir_shbuf_get_dir_start);
+
+/*
+ * Map granted references of the shared buffer.
+ *
+ * Depending on the shared buffer mode of allocation
+ * (be_alloc flag) this can either do nothing (for buffers
+ * shared by the frontend itself) or map the provided granted
+ * references onto the backing storage (buf->pages).
+ *
+ * \param buf shared buffer which grants to be mapped.
+ * \return zero on success or a negative number on failure.
+ */
+int xen_front_pgdir_shbuf_map(struct xen_front_pgdir_shbuf *buf)
+{
+	if (buf->ops && buf->ops->map)
+		return buf->ops->map(buf);
+
+	/* No need to map own grant references. */
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_front_pgdir_shbuf_map);
+
+/*
+ * Unmap granted references of the shared buffer.
+ *
+ * Depending on the shared buffer mode of allocation
+ * (be_alloc flag) this can either do nothing (for buffers
+ * shared by the frontend itself) or unmap the provided granted
+ * references.
+ *
+ * \param buf shared buffer which grants to be unmapped.
+ * \return zero on success or a negative number on failure.
+ */
+int xen_front_pgdir_shbuf_unmap(struct xen_front_pgdir_shbuf *buf)
+{
+	if (buf->ops && buf->ops->unmap)
+		return buf->ops->unmap(buf);
+
+	/* No need to unmap own grant references. */
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_front_pgdir_shbuf_unmap);
+
+/*
+ * Free all the resources of the shared buffer.
+ *
+ * \param buf shared buffer which resources to be freed.
+ */
+void xen_front_pgdir_shbuf_free(struct xen_front_pgdir_shbuf *buf)
+{
+	if (buf->grefs) {
+		int i;
+
+		for (i = 0; i < buf->num_grefs; i++)
+			if (buf->grefs[i] != INVALID_GRANT_REF)
+				gnttab_end_foreign_access(buf->grefs[i], NULL);
+	}
+	kfree(buf->grefs);
+	kfree(buf->directory);
+}
+EXPORT_SYMBOL_GPL(xen_front_pgdir_shbuf_free);
+
+/*
+ * Number of grefs a page can hold with respect to the
+ * struct xen_page_directory header.
+ */
+#define XEN_NUM_GREFS_PER_PAGE ((PAGE_SIZE - \
+				 offsetof(struct xen_page_directory, \
+					  gref)) / sizeof(grant_ref_t))
+
+/*
+ * Get the number of pages the page directory consumes itself.
+ *
+ * \param buf shared buffer.
+ */
+static int get_num_pages_dir(struct xen_front_pgdir_shbuf *buf)
+{
+	return DIV_ROUND_UP(buf->num_pages, XEN_NUM_GREFS_PER_PAGE);
+}
+
+/*
+ * Calculate the number of grant references needed to share the buffer
+ * and its pages when backend allocates the buffer.
+ *
+ * \param buf shared buffer.
+ */
+static void backend_calc_num_grefs(struct xen_front_pgdir_shbuf *buf)
+{
+	/* Only for pages the page directory consumes itself. */
+	buf->num_grefs = get_num_pages_dir(buf);
+}
+
+/*
+ * Calculate the number of grant references needed to share the buffer
+ * and its pages when frontend allocates the buffer.
+ *
+ * \param buf shared buffer.
+ */
+static void guest_calc_num_grefs(struct xen_front_pgdir_shbuf *buf)
+{
+	/*
+	 * Number of pages the page directory consumes itself
+	 * plus grefs for the buffer pages.
+	 */
+	buf->num_grefs = get_num_pages_dir(buf) + buf->num_pages;
+}
+
+#define xen_page_to_vaddr(page) \
+	((uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
+
+/*
+ * Unmap the buffer previously mapped with grant references
+ * provided by the backend.
+ *
+ * \param buf shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+static int backend_unmap(struct xen_front_pgdir_shbuf *buf)
+{
+	struct gnttab_unmap_grant_ref *unmap_ops;
+	int i, ret;
+
+	if (!buf->pages || !buf->backend_map_handles || !buf->grefs)
+		return 0;
+
+	unmap_ops = kzalloc_objs(*unmap_ops, buf->num_pages);
+	if (!unmap_ops)
+		return -ENOMEM;
+
+	for (i = 0; i < buf->num_pages; i++) {
+		phys_addr_t addr;
+
+		addr = xen_page_to_vaddr(buf->pages[i]);
+		gnttab_set_unmap_op(&unmap_ops[i], addr, GNTMAP_host_map,
+				    buf->backend_map_handles[i]);
+	}
+
+	ret = gnttab_unmap_refs(unmap_ops, NULL, buf->pages,
+				buf->num_pages);
+
+	for (i = 0; i < buf->num_pages; i++) {
+		if (unlikely(unmap_ops[i].status != GNTST_okay))
+			dev_err(&buf->xb_dev->dev,
+				"Failed to unmap page %d: %d\n",
+				i, unmap_ops[i].status);
+	}
+
+	if (ret)
+		dev_err(&buf->xb_dev->dev,
+			"Failed to unmap grant references, ret %d", ret);
+
+	kfree(unmap_ops);
+	kfree(buf->backend_map_handles);
+	buf->backend_map_handles = NULL;
+	return ret;
+}
+
+/*
+ * Map the buffer with grant references provided by the backend.
+ *
+ * \param buf shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+static int backend_map(struct xen_front_pgdir_shbuf *buf)
+{
+	struct gnttab_map_grant_ref *map_ops = NULL;
+	unsigned char *ptr;
+	int ret, cur_gref, cur_dir_page, cur_page, grefs_left;
+
+	map_ops = kzalloc_objs(*map_ops, buf->num_pages);
+	if (!map_ops)
+		return -ENOMEM;
+
+	buf->backend_map_handles = kzalloc_objs(*buf->backend_map_handles,
+						buf->num_pages);
+	if (!buf->backend_map_handles) {
+		kfree(map_ops);
+		return -ENOMEM;
+	}
+
+	/*
+	 * Read page directory to get grefs from the backend: for external
+	 * buffer we only allocate buf->grefs for the page directory,
+	 * so buf->num_grefs has number of pages in the page directory itself.
+	 */
+	ptr = buf->directory;
+	grefs_left = buf->num_pages;
+	cur_page = 0;
+	for (cur_dir_page = 0; cur_dir_page < buf->num_grefs; cur_dir_page++) {
+		struct xen_page_directory *page_dir =
+			(struct xen_page_directory *)ptr;
+		int to_copy = XEN_NUM_GREFS_PER_PAGE;
+
+		if (to_copy > grefs_left)
+			to_copy = grefs_left;
+
+		for (cur_gref = 0; cur_gref < to_copy; cur_gref++) {
+			phys_addr_t addr;
+
+			addr = xen_page_to_vaddr(buf->pages[cur_page]);
+			gnttab_set_map_op(&map_ops[cur_page], addr,
+					  GNTMAP_host_map,
+					  page_dir->gref[cur_gref],
+					  buf->xb_dev->otherend_id);
+			cur_page++;
+		}
+
+		grefs_left -= to_copy;
+		ptr += PAGE_SIZE;
+	}
+	ret = gnttab_map_refs(map_ops, NULL, buf->pages, buf->num_pages);
+
+	/* Save handles even if error, so we can unmap. */
+	for (cur_page = 0; cur_page < buf->num_pages; cur_page++) {
+		if (likely(map_ops[cur_page].status == GNTST_okay)) {
+			buf->backend_map_handles[cur_page] =
+				map_ops[cur_page].handle;
+		} else {
+			buf->backend_map_handles[cur_page] =
+				INVALID_GRANT_HANDLE;
+			if (!ret)
+				ret = -ENXIO;
+			dev_err(&buf->xb_dev->dev,
+				"Failed to map page %d: %d\n",
+				cur_page, map_ops[cur_page].status);
+		}
+	}
+
+	if (ret) {
+		dev_err(&buf->xb_dev->dev,
+			"Failed to map grant references, ret %d", ret);
+		backend_unmap(buf);
+	}
+
+	kfree(map_ops);
+	return ret;
+}
+
+/*
+ * Fill page directory with grant references to the pages of the
+ * page directory itself.
+ *
+ * The grant references to the buffer pages are provided by the
+ * backend in this case.
+ *
+ * \param buf shared buffer.
+ */
+static void backend_fill_page_dir(struct xen_front_pgdir_shbuf *buf)
+{
+	struct xen_page_directory *page_dir;
+	unsigned char *ptr;
+	int i, num_pages_dir;
+
+	ptr = buf->directory;
+	num_pages_dir = get_num_pages_dir(buf);
+
+	/* Fill only grefs for the page directory itself. */
+	for (i = 0; i < num_pages_dir - 1; i++) {
+		page_dir = (struct xen_page_directory *)ptr;
+
+		page_dir->gref_dir_next_page = buf->grefs[i + 1];
+		ptr += PAGE_SIZE;
+	}
+	/* Last page must say there is no more pages. */
+	page_dir = (struct xen_page_directory *)ptr;
+	page_dir->gref_dir_next_page = XEN_GREF_LIST_END;
+}
+
+/*
+ * Fill page directory with grant references to the pages of the
+ * page directory and the buffer we share with the backend.
+ *
+ * \param buf shared buffer.
+ */
+static void guest_fill_page_dir(struct xen_front_pgdir_shbuf *buf)
+{
+	unsigned char *ptr;
+	int cur_gref, grefs_left, to_copy, i, num_pages_dir;
+
+	ptr = buf->directory;
+	num_pages_dir = get_num_pages_dir(buf);
+
+	/*
+	 * While copying, skip grefs at start, they are for pages
+	 * granted for the page directory itself.
+	 */
+	cur_gref = num_pages_dir;
+	grefs_left = buf->num_pages;
+	for (i = 0; i < num_pages_dir; i++) {
+		struct xen_page_directory *page_dir =
+			(struct xen_page_directory *)ptr;
+
+		if (grefs_left <= XEN_NUM_GREFS_PER_PAGE) {
+			to_copy = grefs_left;
+			page_dir->gref_dir_next_page = XEN_GREF_LIST_END;
+		} else {
+			to_copy = XEN_NUM_GREFS_PER_PAGE;
+			page_dir->gref_dir_next_page = buf->grefs[i + 1];
+		}
+		memcpy(&page_dir->gref, &buf->grefs[cur_gref],
+		       to_copy * sizeof(grant_ref_t));
+		ptr += PAGE_SIZE;
+		grefs_left -= to_copy;
+		cur_gref += to_copy;
+	}
+}
+
+/*
+ * Grant references to the frontend's buffer pages.
+ *
+ * These will be shared with the backend, so it can
+ * access the buffer's data.
+ *
+ * \param buf shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+static int guest_grant_refs_for_buffer(struct xen_front_pgdir_shbuf *buf,
+				       grant_ref_t *priv_gref_head,
+				       int gref_idx)
+{
+	int i, cur_ref, otherend_id;
+
+	otherend_id = buf->xb_dev->otherend_id;
+	for (i = 0; i < buf->num_pages; i++) {
+		cur_ref = gnttab_claim_grant_reference(priv_gref_head);
+		if (cur_ref < 0)
+			return cur_ref;
+
+		gnttab_grant_foreign_access_ref(cur_ref, otherend_id,
+						xen_page_to_gfn(buf->pages[i]),
+						0);
+		buf->grefs[gref_idx++] = cur_ref;
+	}
+	return 0;
+}
+
+/*
+ * Grant all the references needed to share the buffer.
+ *
+ * Grant references to the page directory pages and, if
+ * needed, also to the pages of the shared buffer data.
+ *
+ * \param buf shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+static int grant_references(struct xen_front_pgdir_shbuf *buf)
+{
+	grant_ref_t priv_gref_head;
+	int ret, i, j, cur_ref;
+	int otherend_id, num_pages_dir;
+
+	ret = gnttab_alloc_grant_references(buf->num_grefs, &priv_gref_head);
+	if (ret < 0) {
+		dev_err(&buf->xb_dev->dev,
+			"Cannot allocate grant references\n");
+		return ret;
+	}
+
+	otherend_id = buf->xb_dev->otherend_id;
+	j = 0;
+	num_pages_dir = get_num_pages_dir(buf);
+	for (i = 0; i < num_pages_dir; i++) {
+		unsigned long frame;
+
+		cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
+		if (cur_ref < 0) {
+			ret = cur_ref;
+			goto out_free_refs;
+		}
+
+		frame = xen_page_to_gfn(virt_to_page(buf->directory +
+						     PAGE_SIZE * i));
+		gnttab_grant_foreign_access_ref(cur_ref, otherend_id, frame, 0);
+		buf->grefs[j++] = cur_ref;
+	}
+
+	if (buf->ops->grant_refs_for_buffer) {
+		ret = buf->ops->grant_refs_for_buffer(buf, &priv_gref_head, j);
+		if (ret)
+			goto out_free_refs;
+	}
+
+	ret = 0;
+out_free_refs:
+	gnttab_free_grant_references(priv_gref_head);
+	return ret;
+}
+
+/*
+ * Allocate all required structures to mange shared buffer.
+ *
+ * \param buf shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+static int alloc_storage(struct xen_front_pgdir_shbuf *buf)
+{
+	buf->grefs = kzalloc_objs(*buf->grefs, buf->num_grefs);
+	if (!buf->grefs)
+		return -ENOMEM;
+
+	buf->directory = kcalloc(get_num_pages_dir(buf), PAGE_SIZE, GFP_KERNEL);
+	if (!buf->directory)
+		return -ENOMEM;
+
+	return 0;
+}
+
+/*
+ * For backend allocated buffers we don't need grant_refs_for_buffer
+ * as those grant references are allocated at backend side.
+ */
+static const struct xen_front_pgdir_shbuf_ops backend_ops = {
+	.calc_num_grefs = backend_calc_num_grefs,
+	.fill_page_dir = backend_fill_page_dir,
+	.map = backend_map,
+	.unmap = backend_unmap
+};
+
+/*
+ * For locally granted references we do not need to map/unmap
+ * the references.
+ */
+static const struct xen_front_pgdir_shbuf_ops local_ops = {
+	.calc_num_grefs = guest_calc_num_grefs,
+	.fill_page_dir = guest_fill_page_dir,
+	.grant_refs_for_buffer = guest_grant_refs_for_buffer,
+};
+
+/*
+ * Allocate a new instance of a shared buffer.
+ *
+ * \param cfg configuration to be used while allocating a new shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+int xen_front_pgdir_shbuf_alloc(struct xen_front_pgdir_shbuf_cfg *cfg)
+{
+	struct xen_front_pgdir_shbuf *buf = cfg->pgdir;
+	int ret;
+
+	if (cfg->be_alloc)
+		buf->ops = &backend_ops;
+	else
+		buf->ops = &local_ops;
+	buf->xb_dev = cfg->xb_dev;
+	buf->num_pages = cfg->num_pages;
+	buf->pages = cfg->pages;
+
+	buf->ops->calc_num_grefs(buf);
+
+	ret = alloc_storage(buf);
+	if (ret)
+		goto fail;
+
+	ret = grant_references(buf);
+	if (ret)
+		goto fail;
+
+	buf->ops->fill_page_dir(buf);
+
+	return 0;
+
+fail:
+	xen_front_pgdir_shbuf_free(buf);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xen_front_pgdir_shbuf_alloc);
+
+MODULE_DESCRIPTION("Xen frontend/backend page directory based "
+		   "shared buffer handling");
+MODULE_AUTHOR("Oleksandr Andrushchenko");
+MODULE_LICENSE("GPL");
diff --git a/drivers/xen/xen-pciback/Makefile b/drivers/xen/xen-pciback/Makefile
new file mode 100644
index 000000000..d63df09de
--- /dev/null
+++ b/drivers/xen/xen-pciback/Makefile
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# N.B. The below cannot be expressed with a single line using
+# CONFIG_XEN_PCI_STUB as it always remains in "y" state,
+# thus preventing the driver to be built as a module.
+# Please note, that CONFIG_XEN_PCIDEV_BACKEND and
+# CONFIG_XEN_PCIDEV_STUB are mutually exclusive.
+obj-$(CONFIG_XEN_PCIDEV_BACKEND) += xen-pciback.o
+obj-$(CONFIG_XEN_PCIDEV_STUB) += xen-pciback.o
+
+xen-pciback-y := pci_stub.o pciback_ops.o xenbus.o
+xen-pciback-y += conf_space.o conf_space_header.o \
+		 conf_space_capability.o \
+		 conf_space_quirks.o vpci.o \
+		 passthrough.o
diff --git a/drivers/xen/xen-pciback/conf_space.c b/drivers/xen/xen-pciback/conf_space.c
new file mode 100644
index 000000000..a2ae8de6f
--- /dev/null
+++ b/drivers/xen/xen-pciback/conf_space.c
@@ -0,0 +1,471 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PCI Backend - Functions for creating a virtual configuration space for
+ *               exported PCI Devices.
+ *               It's dangerous to allow PCI Driver Domains to change their
+ *               device's resources (memory, i/o ports, interrupts). We need to
+ *               restrict changes to certain PCI Configuration registers:
+ *               BARs, INTERRUPT_PIN, most registers in the header...
+ *
+ * Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ */
+
+#define dev_fmt(fmt) DRV_NAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/moduleparam.h>
+#include <linux/pci.h>
+#include "pciback.h"
+#include "conf_space.h"
+#include "conf_space_quirks.h"
+
+bool xen_pcibk_permissive;
+module_param_named(permissive, xen_pcibk_permissive, bool, 0644);
+
+/* This is where xen_pcibk_read_config_byte, xen_pcibk_read_config_word,
+ * xen_pcibk_write_config_word, and xen_pcibk_write_config_byte are created. */
+#define DEFINE_PCI_CONFIG(op, size, type)			\
+int xen_pcibk_##op##_config_##size				\
+(struct pci_dev *dev, int offset, type value, void *data)	\
+{								\
+	return pci_##op##_config_##size(dev, offset, value);	\
+}
+
+DEFINE_PCI_CONFIG(read, byte, u8 *)
+DEFINE_PCI_CONFIG(read, word, u16 *)
+DEFINE_PCI_CONFIG(read, dword, u32 *)
+
+DEFINE_PCI_CONFIG(write, byte, u8)
+DEFINE_PCI_CONFIG(write, word, u16)
+DEFINE_PCI_CONFIG(write, dword, u32)
+
+static int conf_space_read(struct pci_dev *dev,
+			   const struct config_field_entry *entry,
+			   int offset, u32 *value)
+{
+	int ret = 0;
+	const struct config_field *field = entry->field;
+
+	*value = 0;
+
+	switch (field->size) {
+	case 1:
+		if (field->u.b.read)
+			ret = field->u.b.read(dev, offset, (u8 *) value,
+					      entry->data);
+		break;
+	case 2:
+		if (field->u.w.read)
+			ret = field->u.w.read(dev, offset, (u16 *) value,
+					      entry->data);
+		break;
+	case 4:
+		if (field->u.dw.read)
+			ret = field->u.dw.read(dev, offset, value, entry->data);
+		break;
+	}
+	return ret;
+}
+
+static int conf_space_write(struct pci_dev *dev,
+			    const struct config_field_entry *entry,
+			    int offset, u32 value)
+{
+	int ret = 0;
+	const struct config_field *field = entry->field;
+
+	switch (field->size) {
+	case 1:
+		if (field->u.b.write)
+			ret = field->u.b.write(dev, offset, (u8) value,
+					       entry->data);
+		break;
+	case 2:
+		if (field->u.w.write)
+			ret = field->u.w.write(dev, offset, (u16) value,
+					       entry->data);
+		break;
+	case 4:
+		if (field->u.dw.write)
+			ret = field->u.dw.write(dev, offset, value,
+						entry->data);
+		break;
+	}
+	return ret;
+}
+
+static inline u32 get_mask(int size)
+{
+	if (size == 1)
+		return 0xff;
+	else if (size == 2)
+		return 0xffff;
+	else
+		return 0xffffffff;
+}
+
+static inline int valid_request(int offset, int size)
+{
+	/* Validate request (no un-aligned requests) */
+	if ((size == 1 || size == 2 || size == 4) && (offset % size) == 0)
+		return 1;
+	return 0;
+}
+
+static inline u32 merge_value(u32 val, u32 new_val, u32 new_val_mask,
+			      int offset)
+{
+	if (offset >= 0) {
+		new_val_mask <<= (offset * 8);
+		new_val <<= (offset * 8);
+	} else {
+		new_val_mask >>= (offset * -8);
+		new_val >>= (offset * -8);
+	}
+	val = (val & ~new_val_mask) | (new_val & new_val_mask);
+
+	return val;
+}
+
+static int xen_pcibios_err_to_errno(int err)
+{
+	switch (err) {
+	case PCIBIOS_SUCCESSFUL:
+		return XEN_PCI_ERR_success;
+	case PCIBIOS_DEVICE_NOT_FOUND:
+		return XEN_PCI_ERR_dev_not_found;
+	case PCIBIOS_BAD_REGISTER_NUMBER:
+		return XEN_PCI_ERR_invalid_offset;
+	case PCIBIOS_FUNC_NOT_SUPPORTED:
+		return XEN_PCI_ERR_not_implemented;
+	case PCIBIOS_SET_FAILED:
+		return XEN_PCI_ERR_access_denied;
+	}
+	return err;
+}
+
+int xen_pcibk_config_read(struct pci_dev *dev, int offset, int size,
+			  u32 *ret_val)
+{
+	int err = 0;
+	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
+	const struct config_field_entry *cfg_entry;
+	const struct config_field *field;
+	int field_start, field_end;
+	/* if read fails for any reason, return 0
+	 * (as if device didn't respond) */
+	u32 value = 0, tmp_val;
+
+	dev_dbg(&dev->dev, "read %d bytes at 0x%x\n", size, offset);
+
+	if (!valid_request(offset, size)) {
+		err = XEN_PCI_ERR_invalid_offset;
+		goto out;
+	}
+
+	/* Get the real value first, then modify as appropriate */
+	switch (size) {
+	case 1:
+		err = pci_read_config_byte(dev, offset, (u8 *) &value);
+		break;
+	case 2:
+		err = pci_read_config_word(dev, offset, (u16 *) &value);
+		break;
+	case 4:
+		err = pci_read_config_dword(dev, offset, &value);
+		break;
+	}
+
+	list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
+		field = cfg_entry->field;
+
+		field_start = OFFSET(cfg_entry);
+		field_end = OFFSET(cfg_entry) + field->size;
+
+		if (offset + size > field_start && field_end > offset) {
+			err = conf_space_read(dev, cfg_entry, field_start,
+					      &tmp_val);
+			if (err)
+				goto out;
+
+			value = merge_value(value, tmp_val,
+					    get_mask(field->size),
+					    field_start - offset);
+		}
+	}
+
+out:
+	dev_dbg(&dev->dev, "read %d bytes at 0x%x = %x\n", size, offset, value);
+
+	*ret_val = value;
+	return xen_pcibios_err_to_errno(err);
+}
+
+int xen_pcibk_config_write(struct pci_dev *dev, int offset, int size, u32 value)
+{
+	int err = 0, handled = 0;
+	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
+	const struct config_field_entry *cfg_entry;
+	const struct config_field *field;
+	u32 tmp_val;
+	int field_start, field_end;
+
+	dev_dbg(&dev->dev, "write request %d bytes at 0x%x = %x\n",
+		size, offset, value);
+
+	if (!valid_request(offset, size))
+		return XEN_PCI_ERR_invalid_offset;
+
+	list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
+		field = cfg_entry->field;
+
+		field_start = OFFSET(cfg_entry);
+		field_end = OFFSET(cfg_entry) + field->size;
+
+		if (offset + size > field_start && field_end > offset) {
+			err = conf_space_read(dev, cfg_entry, field_start,
+					      &tmp_val);
+			if (err)
+				break;
+
+			tmp_val = merge_value(tmp_val, value, get_mask(size),
+					      offset - field_start);
+
+			err = conf_space_write(dev, cfg_entry, field_start,
+					       tmp_val);
+
+			/* handled is set true here, but not every byte
+			 * may have been written! Properly detecting if
+			 * every byte is handled is unnecessary as the
+			 * flag is used to detect devices that need
+			 * special helpers to work correctly.
+			 */
+			handled = 1;
+		}
+	}
+
+	if (!handled && !err) {
+		/* By default, anything not specificially handled above is
+		 * read-only. The permissive flag changes this behavior so
+		 * that anything not specifically handled above is writable.
+		 * This means that some fields may still be read-only because
+		 * they have entries in the config_field list that intercept
+		 * the write and do nothing. */
+		if (dev_data->permissive || xen_pcibk_permissive) {
+			switch (size) {
+			case 1:
+				err = pci_write_config_byte(dev, offset,
+							    (u8) value);
+				break;
+			case 2:
+				err = pci_write_config_word(dev, offset,
+							    (u16) value);
+				break;
+			case 4:
+				err = pci_write_config_dword(dev, offset,
+							     (u32) value);
+				break;
+			}
+		} else if (!dev_data->warned_on_write) {
+			dev_data->warned_on_write = 1;
+			dev_warn(&dev->dev, "Driver tried to write to a "
+				 "read-only configuration space field at offset"
+				 " 0x%x, size %d. This may be harmless, but if "
+				 "you have problems with your device:\n"
+				 "1) see permissive attribute in sysfs\n"
+				 "2) report problems to the xen-devel "
+				 "mailing list along with details of your "
+				 "device obtained from lspci.\n", offset, size);
+		}
+	}
+
+	return xen_pcibios_err_to_errno(err);
+}
+
+int xen_pcibk_get_interrupt_type(struct pci_dev *dev)
+{
+	int err;
+	u16 val;
+	int ret = 0;
+
+	/*
+	 * Do not trust dev->msi(x)_enabled here, as enabling could be done
+	 * bypassing the pci_*msi* functions, by the qemu.
+	 */
+	if (dev->msi_cap) {
+		err = pci_read_config_word(dev,
+				dev->msi_cap + PCI_MSI_FLAGS,
+				&val);
+		if (err)
+			return err;
+		if (val & PCI_MSI_FLAGS_ENABLE)
+			ret |= INTERRUPT_TYPE_MSI;
+	}
+	if (dev->msix_cap) {
+		err = pci_read_config_word(dev,
+				dev->msix_cap + PCI_MSIX_FLAGS,
+				&val);
+		if (err)
+			return err;
+		if (val & PCI_MSIX_FLAGS_ENABLE)
+			ret |= INTERRUPT_TYPE_MSIX;
+	}
+
+	/*
+	 * PCIe spec says device cannot use INTx if MSI/MSI-X is enabled,
+	 * so check for INTx only when both are disabled.
+	 */
+	if (!ret) {
+		err = pci_read_config_word(dev, PCI_COMMAND, &val);
+		if (err)
+			return err;
+		if (!(val & PCI_COMMAND_INTX_DISABLE))
+			ret |= INTERRUPT_TYPE_INTX;
+	}
+
+	return ret ?: INTERRUPT_TYPE_NONE;
+}
+
+void xen_pcibk_config_free_dyn_fields(struct pci_dev *dev)
+{
+	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
+	struct config_field_entry *cfg_entry, *t;
+	const struct config_field *field;
+
+	dev_dbg(&dev->dev, "free-ing dynamically allocated virtual "
+			   "configuration space fields\n");
+	if (!dev_data)
+		return;
+
+	list_for_each_entry_safe(cfg_entry, t, &dev_data->config_fields, list) {
+		field = cfg_entry->field;
+
+		if (field->clean) {
+			field->clean((struct config_field *)field);
+
+			kfree(cfg_entry->data);
+
+			list_del(&cfg_entry->list);
+			kfree(cfg_entry);
+		}
+
+	}
+}
+
+void xen_pcibk_config_reset_dev(struct pci_dev *dev)
+{
+	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
+	const struct config_field_entry *cfg_entry;
+	const struct config_field *field;
+
+	dev_dbg(&dev->dev, "resetting virtual configuration space\n");
+	if (!dev_data)
+		return;
+
+	list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
+		field = cfg_entry->field;
+
+		if (field->reset)
+			field->reset(dev, OFFSET(cfg_entry), cfg_entry->data);
+	}
+}
+
+void xen_pcibk_config_free_dev(struct pci_dev *dev)
+{
+	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
+	struct config_field_entry *cfg_entry, *t;
+	const struct config_field *field;
+
+	dev_dbg(&dev->dev, "free-ing virtual configuration space fields\n");
+	if (!dev_data)
+		return;
+
+	list_for_each_entry_safe(cfg_entry, t, &dev_data->config_fields, list) {
+		list_del(&cfg_entry->list);
+
+		field = cfg_entry->field;
+
+		if (field->release)
+			field->release(dev, OFFSET(cfg_entry), cfg_entry->data);
+
+		kfree(cfg_entry);
+	}
+}
+
+int xen_pcibk_config_add_field_offset(struct pci_dev *dev,
+				    const struct config_field *field,
+				    unsigned int base_offset)
+{
+	int err = 0;
+	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
+	struct config_field_entry *cfg_entry;
+	void *tmp;
+
+	cfg_entry = kmalloc_obj(*cfg_entry);
+	if (!cfg_entry) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	cfg_entry->data = NULL;
+	cfg_entry->field = field;
+	cfg_entry->base_offset = base_offset;
+
+	/* silently ignore duplicate fields */
+	err = xen_pcibk_field_is_dup(dev, OFFSET(cfg_entry));
+	if (err)
+		goto out;
+
+	if (field->init) {
+		tmp = field->init(dev, OFFSET(cfg_entry));
+
+		if (IS_ERR(tmp)) {
+			err = PTR_ERR(tmp);
+			goto out;
+		}
+
+		cfg_entry->data = tmp;
+	}
+
+	dev_dbg(&dev->dev, "added config field at offset 0x%02x\n",
+		OFFSET(cfg_entry));
+	list_add_tail(&cfg_entry->list, &dev_data->config_fields);
+
+out:
+	if (err)
+		kfree(cfg_entry);
+
+	return err;
+}
+
+/* This sets up the device's virtual configuration space to keep track of
+ * certain registers (like the base address registers (BARs) so that we can
+ * keep the client from manipulating them directly.
+ */
+int xen_pcibk_config_init_dev(struct pci_dev *dev)
+{
+	int err = 0;
+	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
+
+	dev_dbg(&dev->dev, "initializing virtual configuration space\n");
+
+	INIT_LIST_HEAD(&dev_data->config_fields);
+
+	err = xen_pcibk_config_header_add_fields(dev);
+	if (err)
+		goto out;
+
+	err = xen_pcibk_config_capability_add_fields(dev);
+	if (err)
+		goto out;
+
+	err = xen_pcibk_config_quirks_init(dev);
+
+out:
+	return err;
+}
+
+int xen_pcibk_config_init(void)
+{
+	return xen_pcibk_config_capability_init();
+}
diff --git a/drivers/xen/xen-pciback/conf_space.h b/drivers/xen/xen-pciback/conf_space.h
new file mode 100644
index 000000000..5fe431c79
--- /dev/null
+++ b/drivers/xen/xen-pciback/conf_space.h
@@ -0,0 +1,136 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * PCI Backend - Common data structures for overriding the configuration space
+ *
+ * Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ */
+
+#ifndef __XEN_PCIBACK_CONF_SPACE_H__
+#define __XEN_PCIBACK_CONF_SPACE_H__
+
+#include <linux/list.h>
+#include <linux/err.h>
+
+/* conf_field_init can return an errno in a ptr with ERR_PTR() */
+typedef void *(*conf_field_init) (struct pci_dev *dev, int offset);
+typedef void (*conf_field_reset) (struct pci_dev *dev, int offset, void *data);
+typedef void (*conf_field_free) (struct pci_dev *dev, int offset, void *data);
+
+typedef int (*conf_dword_write) (struct pci_dev *dev, int offset, u32 value,
+				 void *data);
+typedef int (*conf_word_write) (struct pci_dev *dev, int offset, u16 value,
+				void *data);
+typedef int (*conf_byte_write) (struct pci_dev *dev, int offset, u8 value,
+				void *data);
+typedef int (*conf_dword_read) (struct pci_dev *dev, int offset, u32 *value,
+				void *data);
+typedef int (*conf_word_read) (struct pci_dev *dev, int offset, u16 *value,
+			       void *data);
+typedef int (*conf_byte_read) (struct pci_dev *dev, int offset, u8 *value,
+			       void *data);
+
+/* These are the fields within the configuration space which we
+ * are interested in intercepting reads/writes to and changing their
+ * values.
+ */
+struct config_field {
+	unsigned int offset;
+	unsigned int size;
+	unsigned int mask;
+	conf_field_init init;
+	conf_field_reset reset;
+	conf_field_free release;
+	void (*clean) (struct config_field *field);
+	union {
+		struct {
+			conf_dword_write write;
+			conf_dword_read read;
+		} dw;
+		struct {
+			conf_word_write write;
+			conf_word_read read;
+		} w;
+		struct {
+			conf_byte_write write;
+			conf_byte_read read;
+		} b;
+	} u;
+	struct list_head list;
+};
+
+struct config_field_entry {
+	struct list_head list;
+	const struct config_field *field;
+	unsigned int base_offset;
+	void *data;
+};
+
+#define INTERRUPT_TYPE_NONE (0)
+#define INTERRUPT_TYPE_INTX (1<<0)
+#define INTERRUPT_TYPE_MSI  (1<<1)
+#define INTERRUPT_TYPE_MSIX (1<<2)
+
+extern bool xen_pcibk_permissive;
+
+#define OFFSET(cfg_entry) ((cfg_entry)->base_offset+(cfg_entry)->field->offset)
+
+/* Add fields to a device - the add_fields macro expects to get a pointer to
+ * the first entry in an array (of which the ending is marked by size==0)
+ */
+int xen_pcibk_config_add_field_offset(struct pci_dev *dev,
+				    const struct config_field *field,
+				    unsigned int offset);
+
+static inline int xen_pcibk_config_add_field(struct pci_dev *dev,
+					   const struct config_field *field)
+{
+	return xen_pcibk_config_add_field_offset(dev, field, 0);
+}
+
+static inline int xen_pcibk_config_add_fields(struct pci_dev *dev,
+					    const struct config_field *field)
+{
+	int i, err = 0;
+	for (i = 0; field[i].size != 0; i++) {
+		err = xen_pcibk_config_add_field(dev, &field[i]);
+		if (err)
+			break;
+	}
+	return err;
+}
+
+static inline int xen_pcibk_config_add_fields_offset(struct pci_dev *dev,
+					const struct config_field *field,
+					unsigned int offset)
+{
+	int i, err = 0;
+	for (i = 0; field[i].size != 0; i++) {
+		err = xen_pcibk_config_add_field_offset(dev, &field[i], offset);
+		if (err)
+			break;
+	}
+	return err;
+}
+
+/* Read/Write the real configuration space */
+int xen_pcibk_read_config_byte(struct pci_dev *dev, int offset, u8 *value,
+			       void *data);
+int xen_pcibk_read_config_word(struct pci_dev *dev, int offset, u16 *value,
+			       void *data);
+int xen_pcibk_read_config_dword(struct pci_dev *dev, int offset, u32 *value,
+				void *data);
+int xen_pcibk_write_config_byte(struct pci_dev *dev, int offset, u8 value,
+				 void *data);
+int xen_pcibk_write_config_word(struct pci_dev *dev, int offset, u16 value,
+				void *data);
+int xen_pcibk_write_config_dword(struct pci_dev *dev, int offset, u32 value,
+				 void *data);
+
+int xen_pcibk_config_capability_init(void);
+
+int xen_pcibk_config_header_add_fields(struct pci_dev *dev);
+int xen_pcibk_config_capability_add_fields(struct pci_dev *dev);
+
+int xen_pcibk_get_interrupt_type(struct pci_dev *dev);
+
+#endif				/* __XEN_PCIBACK_CONF_SPACE_H__ */
diff --git a/drivers/xen/xen-pciback/conf_space_capability.c b/drivers/xen/xen-pciback/conf_space_capability.c
new file mode 100644
index 000000000..cf568e899
--- /dev/null
+++ b/drivers/xen/xen-pciback/conf_space_capability.c
@@ -0,0 +1,305 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PCI Backend - Handles the virtual fields found on the capability lists
+ *               in the configuration space.
+ *
+ * Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ */
+
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include "pciback.h"
+#include "conf_space.h"
+
+static LIST_HEAD(capabilities);
+struct xen_pcibk_config_capability {
+	struct list_head cap_list;
+
+	int capability;
+
+	/* If the device has the capability found above, add these fields */
+	const struct config_field *fields;
+};
+
+static const struct config_field caplist_header[] = {
+	{
+	 .offset    = PCI_CAP_LIST_ID,
+	 .size      = 2, /* encompass PCI_CAP_LIST_ID & PCI_CAP_LIST_NEXT */
+	 .u.w.read  = xen_pcibk_read_config_word,
+	 .u.w.write = NULL,
+	},
+	{}
+};
+
+static inline void register_capability(struct xen_pcibk_config_capability *cap)
+{
+	list_add_tail(&cap->cap_list, &capabilities);
+}
+
+int xen_pcibk_config_capability_add_fields(struct pci_dev *dev)
+{
+	int err = 0;
+	struct xen_pcibk_config_capability *cap;
+	int cap_offset;
+
+	list_for_each_entry(cap, &capabilities, cap_list) {
+		cap_offset = pci_find_capability(dev, cap->capability);
+		if (cap_offset) {
+			dev_dbg(&dev->dev, "Found capability 0x%x at 0x%x\n",
+				cap->capability, cap_offset);
+
+			err = xen_pcibk_config_add_fields_offset(dev,
+							       caplist_header,
+							       cap_offset);
+			if (err)
+				goto out;
+			err = xen_pcibk_config_add_fields_offset(dev,
+							       cap->fields,
+							       cap_offset);
+			if (err)
+				goto out;
+		}
+	}
+
+out:
+	return err;
+}
+
+static int vpd_address_write(struct pci_dev *dev, int offset, u16 value,
+			     void *data)
+{
+	/* Disallow writes to the vital product data */
+	if (value & PCI_VPD_ADDR_F)
+		return PCIBIOS_SET_FAILED;
+	else
+		return pci_write_config_word(dev, offset, value);
+}
+
+static const struct config_field caplist_vpd[] = {
+	{
+	 .offset    = PCI_VPD_ADDR,
+	 .size      = 2,
+	 .u.w.read  = xen_pcibk_read_config_word,
+	 .u.w.write = vpd_address_write,
+	 },
+	{
+	 .offset     = PCI_VPD_DATA,
+	 .size       = 4,
+	 .u.dw.read  = xen_pcibk_read_config_dword,
+	 .u.dw.write = NULL,
+	 },
+	{}
+};
+
+static int pm_caps_read(struct pci_dev *dev, int offset, u16 *value,
+			void *data)
+{
+	int err;
+	u16 real_value;
+
+	err = pci_read_config_word(dev, offset, &real_value);
+	if (err)
+		goto out;
+
+	*value = real_value & ~PCI_PM_CAP_PME_MASK;
+
+out:
+	return err;
+}
+
+/* PM_OK_BITS specifies the bits that the driver domain is allowed to change.
+ * Can't allow driver domain to enable PMEs - they're shared */
+#define PM_OK_BITS (PCI_PM_CTRL_PME_STATUS|PCI_PM_CTRL_DATA_SEL_MASK)
+
+static int pm_ctrl_write(struct pci_dev *dev, int offset, u16 new_value,
+			 void *data)
+{
+	int err;
+	u16 old_value;
+	pci_power_t new_state;
+
+	err = pci_read_config_word(dev, offset, &old_value);
+	if (err)
+		goto out;
+
+	new_state = (__force pci_power_t)(new_value & PCI_PM_CTRL_STATE_MASK);
+
+	new_value &= PM_OK_BITS;
+	if ((old_value & PM_OK_BITS) != new_value) {
+		new_value = (old_value & ~PM_OK_BITS) | new_value;
+		err = pci_write_config_word(dev, offset, new_value);
+		if (err)
+			goto out;
+	}
+
+	/* Let pci core handle the power management change */
+	dev_dbg(&dev->dev, "set power state to %x\n", new_state);
+	err = pci_set_power_state(dev, new_state);
+	if (err) {
+		err = PCIBIOS_SET_FAILED;
+		goto out;
+	}
+
+ out:
+	return err;
+}
+
+/* Ensure PMEs are disabled */
+static void *pm_ctrl_init(struct pci_dev *dev, int offset)
+{
+	int err;
+	u16 value;
+
+	err = pci_read_config_word(dev, offset, &value);
+	if (err)
+		goto out;
+
+	if (value & PCI_PM_CTRL_PME_ENABLE) {
+		value &= ~PCI_PM_CTRL_PME_ENABLE;
+		err = pci_write_config_word(dev, offset, value);
+	}
+
+out:
+	return err ? ERR_PTR(err) : NULL;
+}
+
+static const struct config_field caplist_pm[] = {
+	{
+		.offset     = PCI_PM_PMC,
+		.size       = 2,
+		.u.w.read   = pm_caps_read,
+	},
+	{
+		.offset     = PCI_PM_CTRL,
+		.size       = 2,
+		.init       = pm_ctrl_init,
+		.u.w.read   = xen_pcibk_read_config_word,
+		.u.w.write  = pm_ctrl_write,
+	},
+	{
+		.offset     = PCI_PM_PPB_EXTENSIONS,
+		.size       = 1,
+		.u.b.read   = xen_pcibk_read_config_byte,
+	},
+	{
+		.offset     = PCI_PM_DATA_REGISTER,
+		.size       = 1,
+		.u.b.read   = xen_pcibk_read_config_byte,
+	},
+	{}
+};
+
+static struct msi_msix_field_config {
+	u16          enable_bit;   /* bit for enabling MSI/MSI-X */
+	u16          allowed_bits; /* bits allowed to be changed */
+	unsigned int int_type;     /* interrupt type for exclusiveness check */
+} msi_field_config = {
+	.enable_bit	= PCI_MSI_FLAGS_ENABLE,
+	.allowed_bits	= PCI_MSI_FLAGS_ENABLE,
+	.int_type	= INTERRUPT_TYPE_MSI,
+}, msix_field_config = {
+	.enable_bit	= PCI_MSIX_FLAGS_ENABLE,
+	.allowed_bits	= PCI_MSIX_FLAGS_ENABLE | PCI_MSIX_FLAGS_MASKALL,
+	.int_type	= INTERRUPT_TYPE_MSIX,
+};
+
+static void *msi_field_init(struct pci_dev *dev, int offset)
+{
+	return &msi_field_config;
+}
+
+static void *msix_field_init(struct pci_dev *dev, int offset)
+{
+	return &msix_field_config;
+}
+
+static int msi_msix_flags_write(struct pci_dev *dev, int offset, u16 new_value,
+				void *data)
+{
+	int err;
+	u16 old_value;
+	const struct msi_msix_field_config *field_config = data;
+	const struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
+
+	if (xen_pcibk_permissive || dev_data->permissive)
+		goto write;
+
+	err = pci_read_config_word(dev, offset, &old_value);
+	if (err)
+		return err;
+
+	if (new_value == old_value)
+		return 0;
+
+	if (!dev_data->allow_interrupt_control ||
+	    (new_value ^ old_value) & ~field_config->allowed_bits)
+		return PCIBIOS_SET_FAILED;
+
+	if (new_value & field_config->enable_bit) {
+		/*
+		 * Don't allow enabling together with other interrupt type, but do
+		 * allow enabling MSI(-X) while INTx is still active to please Linuxes
+		 * MSI(-X) startup sequence. It is safe to do, as according to PCI
+		 * spec, device with enabled MSI(-X) shouldn't use INTx.
+		 */
+		int int_type = xen_pcibk_get_interrupt_type(dev);
+
+		if (int_type == INTERRUPT_TYPE_NONE ||
+		    int_type == INTERRUPT_TYPE_INTX ||
+		    int_type == field_config->int_type)
+			goto write;
+		return PCIBIOS_SET_FAILED;
+	}
+
+write:
+	return pci_write_config_word(dev, offset, new_value);
+}
+
+static const struct config_field caplist_msix[] = {
+	{
+		.offset    = PCI_MSIX_FLAGS,
+		.size      = 2,
+		.init      = msix_field_init,
+		.u.w.read  = xen_pcibk_read_config_word,
+		.u.w.write = msi_msix_flags_write,
+	},
+	{}
+};
+
+static const struct config_field caplist_msi[] = {
+	{
+		.offset    = PCI_MSI_FLAGS,
+		.size      = 2,
+		.init      = msi_field_init,
+		.u.w.read  = xen_pcibk_read_config_word,
+		.u.w.write = msi_msix_flags_write,
+	},
+	{}
+};
+
+static struct xen_pcibk_config_capability xen_pcibk_config_capability_pm = {
+	.capability = PCI_CAP_ID_PM,
+	.fields = caplist_pm,
+};
+static struct xen_pcibk_config_capability xen_pcibk_config_capability_vpd = {
+	.capability = PCI_CAP_ID_VPD,
+	.fields = caplist_vpd,
+};
+static struct xen_pcibk_config_capability xen_pcibk_config_capability_msi = {
+	.capability = PCI_CAP_ID_MSI,
+	.fields = caplist_msi,
+};
+static struct xen_pcibk_config_capability xen_pcibk_config_capability_msix = {
+	.capability = PCI_CAP_ID_MSIX,
+	.fields = caplist_msix,
+};
+
+int xen_pcibk_config_capability_init(void)
+{
+	register_capability(&xen_pcibk_config_capability_vpd);
+	register_capability(&xen_pcibk_config_capability_pm);
+	register_capability(&xen_pcibk_config_capability_msi);
+	register_capability(&xen_pcibk_config_capability_msix);
+
+	return 0;
+}
diff --git a/drivers/xen/xen-pciback/conf_space_header.c b/drivers/xen/xen-pciback/conf_space_header.c
new file mode 100644
index 000000000..8b50cbcbd
--- /dev/null
+++ b/drivers/xen/xen-pciback/conf_space_header.c
@@ -0,0 +1,416 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PCI Backend - Handles the virtual fields in the configuration space headers.
+ *
+ * Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#define dev_fmt pr_fmt
+
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include "pciback.h"
+#include "conf_space.h"
+
+struct pci_cmd_info {
+	u16 val;
+};
+
+struct pci_bar_info {
+	u32 val;
+	u32 len_val;
+	int which;
+};
+
+#define is_enable_cmd(value) ((value)&(PCI_COMMAND_MEMORY|PCI_COMMAND_IO))
+#define is_master_cmd(value) ((value)&PCI_COMMAND_MASTER)
+
+/* Bits guests are allowed to control in permissive mode. */
+#define PCI_COMMAND_GUEST (PCI_COMMAND_MASTER|PCI_COMMAND_SPECIAL| \
+			   PCI_COMMAND_INVALIDATE|PCI_COMMAND_VGA_PALETTE| \
+			   PCI_COMMAND_WAIT|PCI_COMMAND_FAST_BACK)
+
+static void *command_init(struct pci_dev *dev, int offset)
+{
+	struct pci_cmd_info *cmd = kmalloc_obj(*cmd);
+	int err;
+
+	if (!cmd)
+		return ERR_PTR(-ENOMEM);
+
+	err = pci_read_config_word(dev, PCI_COMMAND, &cmd->val);
+	if (err) {
+		kfree(cmd);
+		return ERR_PTR(err);
+	}
+
+	return cmd;
+}
+
+static int command_read(struct pci_dev *dev, int offset, u16 *value, void *data)
+{
+	int ret = pci_read_config_word(dev, offset, value);
+	const struct pci_cmd_info *cmd = data;
+
+	*value &= PCI_COMMAND_GUEST;
+	*value |= cmd->val & ~PCI_COMMAND_GUEST;
+
+	return ret;
+}
+
+static int command_write(struct pci_dev *dev, int offset, u16 value, void *data)
+{
+	struct xen_pcibk_dev_data *dev_data;
+	int err;
+	u16 val;
+	struct pci_cmd_info *cmd = data;
+
+	dev_data = pci_get_drvdata(dev);
+	if (!pci_is_enabled(dev) && is_enable_cmd(value)) {
+		dev_dbg(&dev->dev, "enable\n");
+		err = pci_enable_device(dev);
+		if (err)
+			return err;
+		if (dev_data)
+			dev_data->enable_intx = 1;
+	} else if (pci_is_enabled(dev) && !is_enable_cmd(value)) {
+		dev_dbg(&dev->dev, "disable\n");
+		pci_disable_device(dev);
+		if (dev_data)
+			dev_data->enable_intx = 0;
+	}
+
+	if (!dev->is_busmaster && is_master_cmd(value)) {
+		dev_dbg(&dev->dev, "set bus master\n");
+		pci_set_master(dev);
+	} else if (dev->is_busmaster && !is_master_cmd(value)) {
+		dev_dbg(&dev->dev, "clear bus master\n");
+		pci_clear_master(dev);
+	}
+
+	if (!(cmd->val & PCI_COMMAND_INVALIDATE) &&
+	    (value & PCI_COMMAND_INVALIDATE)) {
+		dev_dbg(&dev->dev, "enable memory-write-invalidate\n");
+		err = pci_set_mwi(dev);
+		if (err) {
+			dev_warn(&dev->dev, "cannot enable memory-write-invalidate (%d)\n",
+				err);
+			value &= ~PCI_COMMAND_INVALIDATE;
+		}
+	} else if ((cmd->val & PCI_COMMAND_INVALIDATE) &&
+		   !(value & PCI_COMMAND_INVALIDATE)) {
+		dev_dbg(&dev->dev, "disable memory-write-invalidate\n");
+		pci_clear_mwi(dev);
+	}
+
+	if (dev_data && dev_data->allow_interrupt_control &&
+	    ((cmd->val ^ value) & PCI_COMMAND_INTX_DISABLE))
+		pci_intx(dev, !(value & PCI_COMMAND_INTX_DISABLE));
+
+	cmd->val = value;
+
+	if (!xen_pcibk_permissive && (!dev_data || !dev_data->permissive))
+		return 0;
+
+	/* Only allow the guest to control certain bits. */
+	err = pci_read_config_word(dev, offset, &val);
+	if (err || val == value)
+		return err;
+
+	value &= PCI_COMMAND_GUEST;
+	value |= val & ~PCI_COMMAND_GUEST;
+
+	return pci_write_config_word(dev, offset, value);
+}
+
+static int rom_write(struct pci_dev *dev, int offset, u32 value, void *data)
+{
+	struct pci_bar_info *bar = data;
+
+	if (unlikely(!bar)) {
+		dev_warn(&dev->dev, "driver data not found\n");
+		return XEN_PCI_ERR_op_failed;
+	}
+
+	/* A write to obtain the length must happen as a 32-bit write.
+	 * This does not (yet) support writing individual bytes
+	 */
+	if ((value | ~PCI_ROM_ADDRESS_MASK) == ~0U)
+		bar->which = 1;
+	else {
+		u32 tmpval;
+		pci_read_config_dword(dev, offset, &tmpval);
+		if (tmpval != bar->val && value == bar->val) {
+			/* Allow restoration of bar value. */
+			pci_write_config_dword(dev, offset, bar->val);
+		}
+		bar->which = 0;
+	}
+
+	/* Do we need to support enabling/disabling the rom address here? */
+
+	return 0;
+}
+
+/* For the BARs, only allow writes which write ~0 or
+ * the correct resource information
+ * (Needed for when the driver probes the resource usage)
+ */
+static int bar_write(struct pci_dev *dev, int offset, u32 value, void *data)
+{
+	struct pci_bar_info *bar = data;
+	unsigned int pos = (offset - PCI_BASE_ADDRESS_0) / 4;
+	const struct resource *res = dev->resource;
+	u32 mask;
+
+	if (unlikely(!bar)) {
+		dev_warn(&dev->dev, "driver data not found\n");
+		return XEN_PCI_ERR_op_failed;
+	}
+
+	/* A write to obtain the length must happen as a 32-bit write.
+	 * This does not (yet) support writing individual bytes
+	 */
+	if (res[pos].flags & IORESOURCE_IO)
+		mask = ~PCI_BASE_ADDRESS_IO_MASK;
+	else if (pos && (res[pos - 1].flags & IORESOURCE_MEM_64))
+		mask = 0;
+	else
+		mask = ~PCI_BASE_ADDRESS_MEM_MASK;
+	if ((value | mask) == ~0U)
+		bar->which = 1;
+	else {
+		u32 tmpval;
+		pci_read_config_dword(dev, offset, &tmpval);
+		if (tmpval != bar->val && value == bar->val) {
+			/* Allow restoration of bar value. */
+			pci_write_config_dword(dev, offset, bar->val);
+		}
+		bar->which = 0;
+	}
+
+	return 0;
+}
+
+static int bar_read(struct pci_dev *dev, int offset, u32 * value, void *data)
+{
+	struct pci_bar_info *bar = data;
+
+	if (unlikely(!bar)) {
+		dev_warn(&dev->dev, "driver data not found\n");
+		return XEN_PCI_ERR_op_failed;
+	}
+
+	*value = bar->which ? bar->len_val : bar->val;
+
+	return 0;
+}
+
+static void *bar_init(struct pci_dev *dev, int offset)
+{
+	unsigned int pos;
+	const struct resource *res = dev->resource;
+	struct pci_bar_info *bar = kzalloc_obj(*bar);
+
+	if (!bar)
+		return ERR_PTR(-ENOMEM);
+
+	if (offset == PCI_ROM_ADDRESS || offset == PCI_ROM_ADDRESS1)
+		pos = PCI_ROM_RESOURCE;
+	else {
+		pos = (offset - PCI_BASE_ADDRESS_0) / 4;
+		if (pos && (res[pos - 1].flags & IORESOURCE_MEM_64)) {
+			/*
+			 * Use ">> 16 >> 16" instead of direct ">> 32" shift
+			 * to avoid warnings on 32-bit architectures.
+			 */
+			bar->val = res[pos - 1].start >> 16 >> 16;
+			bar->len_val = -resource_size(&res[pos - 1]) >> 16 >> 16;
+			return bar;
+		}
+	}
+
+	if (!res[pos].flags ||
+	    (res[pos].flags & (IORESOURCE_DISABLED | IORESOURCE_UNSET |
+			       IORESOURCE_BUSY)))
+		return bar;
+
+	bar->val = res[pos].start |
+		   (res[pos].flags & PCI_REGION_FLAG_MASK);
+	bar->len_val = -resource_size(&res[pos]) |
+		       (res[pos].flags & PCI_REGION_FLAG_MASK);
+
+	return bar;
+}
+
+static void bar_reset(struct pci_dev *dev, int offset, void *data)
+{
+	struct pci_bar_info *bar = data;
+
+	bar->which = 0;
+}
+
+static void bar_release(struct pci_dev *dev, int offset, void *data)
+{
+	kfree(data);
+}
+
+static int xen_pcibk_read_vendor(struct pci_dev *dev, int offset,
+			       u16 *value, void *data)
+{
+	*value = dev->vendor;
+
+	return 0;
+}
+
+static int xen_pcibk_read_device(struct pci_dev *dev, int offset,
+			       u16 *value, void *data)
+{
+	*value = dev->device;
+
+	return 0;
+}
+
+static int interrupt_read(struct pci_dev *dev, int offset, u8 * value,
+			  void *data)
+{
+	*value = (u8) dev->irq;
+
+	return 0;
+}
+
+static int bist_write(struct pci_dev *dev, int offset, u8 value, void *data)
+{
+	u8 cur_value;
+	int err;
+
+	err = pci_read_config_byte(dev, offset, &cur_value);
+	if (err)
+		goto out;
+
+	if ((cur_value & ~PCI_BIST_START) == (value & ~PCI_BIST_START)
+	    || value == PCI_BIST_START)
+		err = pci_write_config_byte(dev, offset, value);
+
+out:
+	return err;
+}
+
+static const struct config_field header_common[] = {
+	{
+	 .offset    = PCI_VENDOR_ID,
+	 .size      = 2,
+	 .u.w.read  = xen_pcibk_read_vendor,
+	},
+	{
+	 .offset    = PCI_DEVICE_ID,
+	 .size      = 2,
+	 .u.w.read  = xen_pcibk_read_device,
+	},
+	{
+	 .offset    = PCI_COMMAND,
+	 .size      = 2,
+	 .init      = command_init,
+	 .release   = bar_release,
+	 .u.w.read  = command_read,
+	 .u.w.write = command_write,
+	},
+	{
+	 .offset    = PCI_INTERRUPT_LINE,
+	 .size      = 1,
+	 .u.b.read  = interrupt_read,
+	},
+	{
+	 .offset    = PCI_INTERRUPT_PIN,
+	 .size      = 1,
+	 .u.b.read  = xen_pcibk_read_config_byte,
+	},
+	{
+	 /* Any side effects of letting driver domain control cache line? */
+	 .offset    = PCI_CACHE_LINE_SIZE,
+	 .size      = 1,
+	 .u.b.read  = xen_pcibk_read_config_byte,
+	 .u.b.write = xen_pcibk_write_config_byte,
+	},
+	{
+	 .offset    = PCI_LATENCY_TIMER,
+	 .size      = 1,
+	 .u.b.read  = xen_pcibk_read_config_byte,
+	},
+	{
+	 .offset    = PCI_BIST,
+	 .size      = 1,
+	 .u.b.read  = xen_pcibk_read_config_byte,
+	 .u.b.write = bist_write,
+	},
+	{}
+};
+
+#define CFG_FIELD_BAR(reg_offset)			\
+	{						\
+	.offset     = reg_offset,			\
+	.size       = 4,				\
+	.init       = bar_init,				\
+	.reset      = bar_reset,			\
+	.release    = bar_release,			\
+	.u.dw.read  = bar_read,				\
+	.u.dw.write = bar_write,			\
+	}
+
+#define CFG_FIELD_ROM(reg_offset)			\
+	{						\
+	.offset     = reg_offset,			\
+	.size       = 4,				\
+	.init       = bar_init,				\
+	.reset      = bar_reset,			\
+	.release    = bar_release,			\
+	.u.dw.read  = bar_read,				\
+	.u.dw.write = rom_write,			\
+	}
+
+static const struct config_field header_0[] = {
+	CFG_FIELD_BAR(PCI_BASE_ADDRESS_0),
+	CFG_FIELD_BAR(PCI_BASE_ADDRESS_1),
+	CFG_FIELD_BAR(PCI_BASE_ADDRESS_2),
+	CFG_FIELD_BAR(PCI_BASE_ADDRESS_3),
+	CFG_FIELD_BAR(PCI_BASE_ADDRESS_4),
+	CFG_FIELD_BAR(PCI_BASE_ADDRESS_5),
+	CFG_FIELD_ROM(PCI_ROM_ADDRESS),
+	{}
+};
+
+static const struct config_field header_1[] = {
+	CFG_FIELD_BAR(PCI_BASE_ADDRESS_0),
+	CFG_FIELD_BAR(PCI_BASE_ADDRESS_1),
+	CFG_FIELD_ROM(PCI_ROM_ADDRESS1),
+	{}
+};
+
+int xen_pcibk_config_header_add_fields(struct pci_dev *dev)
+{
+	int err;
+
+	err = xen_pcibk_config_add_fields(dev, header_common);
+	if (err)
+		goto out;
+
+	switch (dev->hdr_type) {
+	case PCI_HEADER_TYPE_NORMAL:
+		err = xen_pcibk_config_add_fields(dev, header_0);
+		break;
+
+	case PCI_HEADER_TYPE_BRIDGE:
+		err = xen_pcibk_config_add_fields(dev, header_1);
+		break;
+
+	default:
+		err = -EINVAL;
+		dev_err(&dev->dev, "Unsupported header type %d!\n",
+			dev->hdr_type);
+		break;
+	}
+
+out:
+	return err;
+}
diff --git a/drivers/xen/xen-pciback/conf_space_quirks.c b/drivers/xen/xen-pciback/conf_space_quirks.c
new file mode 100644
index 000000000..675519b51
--- /dev/null
+++ b/drivers/xen/xen-pciback/conf_space_quirks.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PCI Backend - Handle special overlays for broken devices.
+ *
+ * Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ * Author: Chris Bookholt <hap10@epoch.ncsc.mil>
+ */
+
+#define dev_fmt(fmt) DRV_NAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include "pciback.h"
+#include "conf_space.h"
+#include "conf_space_quirks.h"
+
+LIST_HEAD(xen_pcibk_quirks);
+static inline const struct pci_device_id *
+match_one_device(const struct pci_device_id *id, const struct pci_dev *dev)
+{
+	if ((id->vendor == PCI_ANY_ID || id->vendor == dev->vendor) &&
+	    (id->device == PCI_ANY_ID || id->device == dev->device) &&
+	    (id->subvendor == PCI_ANY_ID ||
+				id->subvendor == dev->subsystem_vendor) &&
+	    (id->subdevice == PCI_ANY_ID ||
+				id->subdevice == dev->subsystem_device) &&
+	    !((id->class ^ dev->class) & id->class_mask))
+		return id;
+	return NULL;
+}
+
+static struct xen_pcibk_config_quirk *xen_pcibk_find_quirk(struct pci_dev *dev)
+{
+	struct xen_pcibk_config_quirk *tmp_quirk;
+
+	list_for_each_entry(tmp_quirk, &xen_pcibk_quirks, quirks_list)
+		if (match_one_device(&tmp_quirk->devid, dev) != NULL)
+			goto out;
+	tmp_quirk = NULL;
+	dev_printk(KERN_DEBUG, &dev->dev,
+		   "quirk didn't match any device known\n");
+out:
+	return tmp_quirk;
+}
+
+static inline void register_quirk(struct xen_pcibk_config_quirk *quirk)
+{
+	list_add_tail(&quirk->quirks_list, &xen_pcibk_quirks);
+}
+
+int xen_pcibk_field_is_dup(struct pci_dev *dev, unsigned int reg)
+{
+	int ret = 0;
+	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
+	struct config_field_entry *cfg_entry;
+
+	list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
+		if (OFFSET(cfg_entry) == reg) {
+			ret = 1;
+			break;
+		}
+	}
+	return ret;
+}
+
+int xen_pcibk_config_quirks_add_field(struct pci_dev *dev, struct config_field
+				    *field)
+{
+	int err = 0;
+
+	switch (field->size) {
+	case 1:
+		field->u.b.read = xen_pcibk_read_config_byte;
+		field->u.b.write = xen_pcibk_write_config_byte;
+		break;
+	case 2:
+		field->u.w.read = xen_pcibk_read_config_word;
+		field->u.w.write = xen_pcibk_write_config_word;
+		break;
+	case 4:
+		field->u.dw.read = xen_pcibk_read_config_dword;
+		field->u.dw.write = xen_pcibk_write_config_dword;
+		break;
+	default:
+		err = -EINVAL;
+		goto out;
+	}
+
+	xen_pcibk_config_add_field(dev, field);
+
+out:
+	return err;
+}
+
+int xen_pcibk_config_quirks_init(struct pci_dev *dev)
+{
+	struct xen_pcibk_config_quirk *quirk;
+	int ret = 0;
+
+	quirk = kzalloc_obj(*quirk);
+	if (!quirk) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	quirk->devid.vendor = dev->vendor;
+	quirk->devid.device = dev->device;
+	quirk->devid.subvendor = dev->subsystem_vendor;
+	quirk->devid.subdevice = dev->subsystem_device;
+	quirk->devid.class = 0;
+	quirk->devid.class_mask = 0;
+	quirk->devid.driver_data = 0UL;
+
+	quirk->pdev = dev;
+
+	register_quirk(quirk);
+out:
+	return ret;
+}
+
+void xen_pcibk_config_field_free(struct config_field *field)
+{
+	kfree(field);
+}
+
+int xen_pcibk_config_quirk_release(struct pci_dev *dev)
+{
+	struct xen_pcibk_config_quirk *quirk;
+	int ret = 0;
+
+	quirk = xen_pcibk_find_quirk(dev);
+	if (!quirk) {
+		ret = -ENXIO;
+		goto out;
+	}
+
+	list_del(&quirk->quirks_list);
+	kfree(quirk);
+
+out:
+	return ret;
+}
diff --git a/drivers/xen/xen-pciback/conf_space_quirks.h b/drivers/xen/xen-pciback/conf_space_quirks.h
new file mode 100644
index 000000000..fc1557dfe
--- /dev/null
+++ b/drivers/xen/xen-pciback/conf_space_quirks.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * PCI Backend - Data structures for special overlays for broken devices.
+ *
+ * Ryan Wilson <hap9@epoch.ncsc.mil>
+ * Chris Bookholt <hap10@epoch.ncsc.mil>
+ */
+
+#ifndef __XEN_PCIBACK_CONF_SPACE_QUIRKS_H__
+#define __XEN_PCIBACK_CONF_SPACE_QUIRKS_H__
+
+#include <linux/pci.h>
+#include <linux/list.h>
+
+struct xen_pcibk_config_quirk {
+	struct list_head quirks_list;
+	struct pci_device_id devid;
+	struct pci_dev *pdev;
+};
+
+int xen_pcibk_config_quirks_add_field(struct pci_dev *dev, struct config_field
+				    *field);
+
+int xen_pcibk_config_quirks_init(struct pci_dev *dev);
+
+void xen_pcibk_config_field_free(struct config_field *field);
+
+int xen_pcibk_config_quirk_release(struct pci_dev *dev);
+
+int xen_pcibk_field_is_dup(struct pci_dev *dev, unsigned int reg);
+
+#endif
diff --git a/drivers/xen/xen-pciback/passthrough.c b/drivers/xen/xen-pciback/passthrough.c
new file mode 100644
index 000000000..7a6df524c
--- /dev/null
+++ b/drivers/xen/xen-pciback/passthrough.c
@@ -0,0 +1,197 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PCI Backend - Provides restricted access to the real PCI bus topology
+ *               to the frontend
+ *
+ *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ */
+
+#include <linux/list.h>
+#include <linux/pci.h>
+#include <linux/mutex.h>
+#include "pciback.h"
+
+struct passthrough_dev_data {
+	/* Access to dev_list must be protected by lock */
+	struct list_head dev_list;
+	struct mutex lock;
+};
+
+static struct pci_dev *__xen_pcibk_get_pci_dev(struct xen_pcibk_device *pdev,
+					       unsigned int domain,
+					       unsigned int bus,
+					       unsigned int devfn)
+{
+	struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
+	struct pci_dev_entry *dev_entry;
+	struct pci_dev *dev = NULL;
+
+	mutex_lock(&dev_data->lock);
+
+	list_for_each_entry(dev_entry, &dev_data->dev_list, list) {
+		if (domain == (unsigned int)pci_domain_nr(dev_entry->dev->bus)
+		    && bus == (unsigned int)dev_entry->dev->bus->number
+		    && devfn == dev_entry->dev->devfn) {
+			dev = dev_entry->dev;
+			break;
+		}
+	}
+
+	mutex_unlock(&dev_data->lock);
+
+	return dev;
+}
+
+static int __xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev,
+				   struct pci_dev *dev,
+				   int devid, publish_pci_dev_cb publish_cb)
+{
+	struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
+	struct pci_dev_entry *dev_entry;
+	unsigned int domain, bus, devfn;
+	int err;
+
+	dev_entry = kmalloc_obj(*dev_entry);
+	if (!dev_entry)
+		return -ENOMEM;
+	dev_entry->dev = dev;
+
+	mutex_lock(&dev_data->lock);
+	list_add_tail(&dev_entry->list, &dev_data->dev_list);
+	mutex_unlock(&dev_data->lock);
+
+	/* Publish this device. */
+	domain = (unsigned int)pci_domain_nr(dev->bus);
+	bus = (unsigned int)dev->bus->number;
+	devfn = dev->devfn;
+	err = publish_cb(pdev, domain, bus, devfn, devid);
+
+	return err;
+}
+
+static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
+					struct pci_dev *dev, bool lock)
+{
+	struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
+	struct pci_dev_entry *dev_entry, *t;
+	struct pci_dev *found_dev = NULL;
+
+	mutex_lock(&dev_data->lock);
+
+	list_for_each_entry_safe(dev_entry, t, &dev_data->dev_list, list) {
+		if (dev_entry->dev == dev) {
+			list_del(&dev_entry->list);
+			found_dev = dev_entry->dev;
+			kfree(dev_entry);
+		}
+	}
+
+	mutex_unlock(&dev_data->lock);
+
+	if (found_dev) {
+		if (lock)
+			device_lock(&found_dev->dev);
+		pcistub_put_pci_dev(found_dev);
+		if (lock)
+			device_unlock(&found_dev->dev);
+	}
+}
+
+static int __xen_pcibk_init_devices(struct xen_pcibk_device *pdev)
+{
+	struct passthrough_dev_data *dev_data;
+
+	dev_data = kmalloc_obj(*dev_data);
+	if (!dev_data)
+		return -ENOMEM;
+
+	mutex_init(&dev_data->lock);
+
+	INIT_LIST_HEAD(&dev_data->dev_list);
+
+	pdev->pci_dev_data = dev_data;
+
+	return 0;
+}
+
+static int __xen_pcibk_publish_pci_roots(struct xen_pcibk_device *pdev,
+					 publish_pci_root_cb publish_root_cb)
+{
+	int err = 0;
+	struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
+	struct pci_dev_entry *dev_entry, *e;
+	struct pci_dev *dev;
+	int found;
+	unsigned int domain, bus;
+
+	mutex_lock(&dev_data->lock);
+
+	list_for_each_entry(dev_entry, &dev_data->dev_list, list) {
+		/* Only publish this device as a root if none of its
+		 * parent bridges are exported
+		 */
+		found = 0;
+		dev = dev_entry->dev->bus->self;
+		for (; !found && dev != NULL; dev = dev->bus->self) {
+			list_for_each_entry(e, &dev_data->dev_list, list) {
+				if (dev == e->dev) {
+					found = 1;
+					break;
+				}
+			}
+		}
+
+		domain = (unsigned int)pci_domain_nr(dev_entry->dev->bus);
+		bus = (unsigned int)dev_entry->dev->bus->number;
+
+		if (!found) {
+			err = publish_root_cb(pdev, domain, bus);
+			if (err)
+				break;
+		}
+	}
+
+	mutex_unlock(&dev_data->lock);
+
+	return err;
+}
+
+static void __xen_pcibk_release_devices(struct xen_pcibk_device *pdev)
+{
+	struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
+	struct pci_dev_entry *dev_entry, *t;
+
+	list_for_each_entry_safe(dev_entry, t, &dev_data->dev_list, list) {
+		struct pci_dev *dev = dev_entry->dev;
+		list_del(&dev_entry->list);
+		device_lock(&dev->dev);
+		pcistub_put_pci_dev(dev);
+		device_unlock(&dev->dev);
+		kfree(dev_entry);
+	}
+
+	kfree(dev_data);
+	pdev->pci_dev_data = NULL;
+}
+
+static int __xen_pcibk_get_pcifront_dev(struct pci_dev *pcidev,
+					struct xen_pcibk_device *pdev,
+					unsigned int *domain, unsigned int *bus,
+					unsigned int *devfn)
+{
+	*domain = pci_domain_nr(pcidev->bus);
+	*bus = pcidev->bus->number;
+	*devfn = pcidev->devfn;
+	return 1;
+}
+
+const struct xen_pcibk_backend xen_pcibk_passthrough_backend = {
+	.name           = "passthrough",
+	.init           = __xen_pcibk_init_devices,
+	.free		= __xen_pcibk_release_devices,
+	.find           = __xen_pcibk_get_pcifront_dev,
+	.publish        = __xen_pcibk_publish_pci_roots,
+	.release        = __xen_pcibk_release_pci_dev,
+	.add            = __xen_pcibk_add_pci_dev,
+	.get            = __xen_pcibk_get_pci_dev,
+};
diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
new file mode 100644
index 000000000..79a2b5dfd
--- /dev/null
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -0,0 +1,1766 @@
+/*
+ * PCI Stub Driver - Grabs devices in backend to be exported later
+ *
+ * Ryan Wilson <hap9@epoch.ncsc.mil>
+ * Chris Bookholt <hap10@epoch.ncsc.mil>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#define dev_fmt pr_fmt
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/rwsem.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/kref.h>
+#include <linux/pci.h>
+#include <linux/wait.h>
+#include <linux/sched.h>
+#include <linux/atomic.h>
+#include <xen/events.h>
+#include <xen/pci.h>
+#include <xen/xen.h>
+#ifdef CONFIG_XEN_ACPI
+#include <xen/acpi.h>
+#endif
+#include <asm/xen/hypervisor.h>
+#include <xen/interface/physdev.h>
+#include "pciback.h"
+#include "conf_space.h"
+#include "conf_space_quirks.h"
+
+#define PCISTUB_DRIVER_NAME "pciback"
+
+static char *pci_devs_to_hide;
+wait_queue_head_t xen_pcibk_aer_wait_queue;
+/*Add sem for sync AER handling and xen_pcibk remove/reconfigue ops,
+* We want to avoid in middle of AER ops, xen_pcibk devices is being removed
+*/
+static DECLARE_RWSEM(pcistub_sem);
+module_param_named(hide, pci_devs_to_hide, charp, 0444);
+
+struct pcistub_device_id {
+	struct list_head slot_list;
+	int domain;
+	unsigned char bus;
+	unsigned int devfn;
+};
+static LIST_HEAD(pcistub_device_ids);
+static DEFINE_SPINLOCK(device_ids_lock);
+
+struct pcistub_device {
+	struct kref kref;
+	struct list_head dev_list;
+	spinlock_t lock;
+
+	struct pci_dev *dev;
+	struct xen_pcibk_device *pdev;/* non-NULL if struct pci_dev is in use */
+#ifdef CONFIG_XEN_ACPI
+	int gsi;
+#endif
+};
+
+/* Access to pcistub_devices & seized_devices lists and the initialize_devices
+ * flag must be locked with pcistub_devices_lock
+ */
+static DEFINE_SPINLOCK(pcistub_devices_lock);
+static LIST_HEAD(pcistub_devices);
+
+/* wait for device_initcall before initializing our devices
+ * (see pcistub_init_devices_late)
+ */
+static int initialize_devices;
+static LIST_HEAD(seized_devices);
+
+static struct pcistub_device *pcistub_device_alloc(struct pci_dev *dev)
+{
+	struct pcistub_device *psdev;
+
+	dev_dbg(&dev->dev, "pcistub_device_alloc\n");
+
+	psdev = kzalloc_obj(*psdev);
+	if (!psdev)
+		return NULL;
+
+	psdev->dev = pci_dev_get(dev);
+	if (!psdev->dev) {
+		kfree(psdev);
+		return NULL;
+	}
+
+	kref_init(&psdev->kref);
+	spin_lock_init(&psdev->lock);
+#ifdef CONFIG_XEN_ACPI
+	psdev->gsi = -1;
+#endif
+
+	return psdev;
+}
+
+static int pcistub_reset_device_state(struct pci_dev *dev)
+{
+	__pci_reset_function_locked(dev);
+
+	if (!xen_pv_domain())
+		return xen_reset_device(dev);
+	else
+		return 0;
+}
+
+/* Don't call this directly as it's called by pcistub_device_put */
+static void pcistub_device_release(struct kref *kref)
+{
+	struct pcistub_device *psdev;
+	struct pci_dev *dev;
+	struct xen_pcibk_dev_data *dev_data;
+
+	psdev = container_of(kref, struct pcistub_device, kref);
+	dev = psdev->dev;
+	dev_data = pci_get_drvdata(dev);
+
+	dev_dbg(&dev->dev, "pcistub_device_release\n");
+
+	xen_unregister_device_domain_owner(dev);
+
+	/* Call the reset function which does not take lock as this
+	 * is called from "unbind" which takes a device_lock mutex.
+	 */
+	pcistub_reset_device_state(dev);
+	if (dev_data &&
+	    pci_load_and_free_saved_state(dev, &dev_data->pci_saved_state))
+		dev_info(&dev->dev, "Could not reload PCI state\n");
+	else
+		pci_restore_state(dev);
+
+	if (dev->msix_cap) {
+		struct physdev_pci_device ppdev = {
+			.seg = pci_domain_nr(dev->bus),
+			.bus = dev->bus->number,
+			.devfn = dev->devfn
+		};
+		int err = HYPERVISOR_physdev_op(PHYSDEVOP_release_msix,
+						&ppdev);
+
+		if (err && err != -ENOSYS)
+			dev_warn(&dev->dev, "MSI-X release failed (%d)\n",
+				 err);
+	}
+
+	/* Disable the device */
+	xen_pcibk_reset_device(dev);
+
+	kfree(dev_data);
+	pci_set_drvdata(dev, NULL);
+
+	/* Clean-up the device */
+	xen_pcibk_config_free_dyn_fields(dev);
+	xen_pcibk_config_free_dev(dev);
+
+	pci_clear_dev_assigned(dev);
+	pci_dev_put(dev);
+
+	kfree(psdev);
+}
+
+static inline void pcistub_device_get(struct pcistub_device *psdev)
+{
+	kref_get(&psdev->kref);
+}
+
+static inline void pcistub_device_put(struct pcistub_device *psdev)
+{
+	kref_put(&psdev->kref, pcistub_device_release);
+}
+
+static struct pcistub_device *pcistub_device_find_locked(int domain, int bus,
+							 int slot, int func)
+{
+	struct pcistub_device *psdev;
+
+	list_for_each_entry(psdev, &pcistub_devices, dev_list) {
+		if (psdev->dev != NULL
+		    && domain == pci_domain_nr(psdev->dev->bus)
+		    && bus == psdev->dev->bus->number
+		    && slot == PCI_SLOT(psdev->dev->devfn)
+		    && func == PCI_FUNC(psdev->dev->devfn)) {
+			return psdev;
+		}
+	}
+
+	return NULL;
+}
+
+static struct pcistub_device *pcistub_device_find(int domain, int bus,
+						  int slot, int func)
+{
+	struct pcistub_device *psdev;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+
+	psdev = pcistub_device_find_locked(domain, bus, slot, func);
+	if (psdev)
+		pcistub_device_get(psdev);
+
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+	return psdev;
+}
+
+static struct pci_dev *pcistub_device_get_pci_dev(struct xen_pcibk_device *pdev,
+						  struct pcistub_device *psdev)
+{
+	struct pci_dev *pci_dev = NULL;
+	unsigned long flags;
+
+	spin_lock_irqsave(&psdev->lock, flags);
+	if (!psdev->pdev) {
+		psdev->pdev = pdev;
+		pci_dev = psdev->dev;
+	}
+	spin_unlock_irqrestore(&psdev->lock, flags);
+
+	if (pci_dev)
+		pcistub_device_get(psdev);
+
+	return pci_dev;
+}
+
+#ifdef CONFIG_XEN_ACPI
+static int pcistub_get_gsi_from_sbdf(unsigned int sbdf)
+{
+	struct pcistub_device *psdev;
+	int domain = (sbdf >> 16) & 0xffff;
+	int bus = PCI_BUS_NUM(sbdf);
+	int slot = PCI_SLOT(sbdf);
+	int func = PCI_FUNC(sbdf);
+
+	psdev = pcistub_device_find(domain, bus, slot, func);
+
+	if (!psdev)
+		return -ENODEV;
+
+	return psdev->gsi;
+}
+#endif
+
+struct pci_dev *pcistub_get_pci_dev_by_slot(struct xen_pcibk_device *pdev,
+					    int domain, int bus,
+					    int slot, int func)
+{
+	struct pcistub_device *psdev;
+	struct pci_dev *found_dev = NULL;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+
+	psdev = pcistub_device_find_locked(domain, bus, slot, func);
+	if (psdev)
+		found_dev = pcistub_device_get_pci_dev(pdev, psdev);
+
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+	return found_dev;
+}
+
+/*
+ * Called when:
+ *  - XenBus state has been reconfigure (pci unplug). See xen_pcibk_remove_device
+ *  - XenBus state has been disconnected (guest shutdown). See xen_pcibk_xenbus_remove
+ *  - 'echo BDF > unbind' on pciback module with no guest attached. See pcistub_remove
+ *  - 'echo BDF > unbind' with a guest still using it. See pcistub_remove
+ *
+ *  As such we have to be careful.
+ *
+ *  To make this easier, the caller has to hold the device lock.
+ */
+void pcistub_put_pci_dev(struct pci_dev *dev)
+{
+	struct pcistub_device *psdev, *found_psdev = NULL;
+	unsigned long flags;
+	struct xen_pcibk_dev_data *dev_data;
+	int ret;
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+
+	list_for_each_entry(psdev, &pcistub_devices, dev_list) {
+		if (psdev->dev == dev) {
+			found_psdev = psdev;
+			break;
+		}
+	}
+
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+	if (WARN_ON(!found_psdev))
+		return;
+
+	/*hold this lock for avoiding breaking link between
+	* pcistub and xen_pcibk when AER is in processing
+	*/
+	down_write(&pcistub_sem);
+	/* Cleanup our device
+	 * (so it's ready for the next domain)
+	 */
+	device_lock_assert(&dev->dev);
+	pcistub_reset_device_state(dev);
+
+	dev_data = pci_get_drvdata(dev);
+	ret = pci_load_saved_state(dev, dev_data->pci_saved_state);
+	if (!ret) {
+		/*
+		 * The usual sequence is pci_save_state & pci_restore_state
+		 * but the guest might have messed the configuration space up.
+		 * Use the initial version (when device was bound to us).
+		 */
+		pci_restore_state(dev);
+	} else
+		dev_info(&dev->dev, "Could not reload PCI state\n");
+	/* This disables the device. */
+	xen_pcibk_reset_device(dev);
+
+	/* And cleanup up our emulated fields. */
+	xen_pcibk_config_reset_dev(dev);
+	xen_pcibk_config_free_dyn_fields(dev);
+
+	dev_data->allow_interrupt_control = 0;
+
+	xen_unregister_device_domain_owner(dev);
+
+	spin_lock_irqsave(&found_psdev->lock, flags);
+	found_psdev->pdev = NULL;
+	spin_unlock_irqrestore(&found_psdev->lock, flags);
+
+	pcistub_device_put(found_psdev);
+	up_write(&pcistub_sem);
+}
+
+static int pcistub_match_one(struct pci_dev *dev,
+			     struct pcistub_device_id *pdev_id)
+{
+	/* Match the specified device by domain, bus, slot, func and also if
+	 * any of the device's parent bridges match.
+	 */
+	for (; dev != NULL; dev = dev->bus->self) {
+		if (pci_domain_nr(dev->bus) == pdev_id->domain
+		    && dev->bus->number == pdev_id->bus
+		    && dev->devfn == pdev_id->devfn)
+			return 1;
+
+		/* Sometimes topmost bridge links to itself. */
+		if (dev == dev->bus->self)
+			break;
+	}
+
+	return 0;
+}
+
+static int pcistub_match(struct pci_dev *dev)
+{
+	struct pcistub_device_id *pdev_id;
+	unsigned long flags;
+	int found = 0;
+
+	spin_lock_irqsave(&device_ids_lock, flags);
+	list_for_each_entry(pdev_id, &pcistub_device_ids, slot_list) {
+		if (pcistub_match_one(dev, pdev_id)) {
+			found = 1;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&device_ids_lock, flags);
+
+	return found;
+}
+
+static int pcistub_init_device(struct pcistub_device *psdev)
+{
+	struct xen_pcibk_dev_data *dev_data;
+	struct pci_dev *dev;
+#ifdef CONFIG_XEN_ACPI
+	int gsi, trigger, polarity;
+#endif
+	int err = 0;
+
+	if (!psdev)
+		return -EINVAL;
+
+	dev = psdev->dev;
+
+	dev_dbg(&dev->dev, "initializing...\n");
+
+	/* The PCI backend is not intended to be a module (or to work with
+	 * removable PCI devices (yet). If it were, xen_pcibk_config_free()
+	 * would need to be called somewhere to free the memory allocated
+	 * here and then to call kfree(pci_get_drvdata(psdev->dev)).
+	 */
+	dev_data = kzalloc(sizeof(*dev_data) +  strlen(DRV_NAME "[]")
+				+ strlen(pci_name(dev)) + 1, GFP_KERNEL);
+	if (!dev_data) {
+		err = -ENOMEM;
+		goto out;
+	}
+	pci_set_drvdata(dev, dev_data);
+
+	/*
+	 * Setup name for fake IRQ handler. It will only be enabled
+	 * once the device is turned on by the guest.
+	 */
+	sprintf(dev_data->irq_name, DRV_NAME "[%s]", pci_name(dev));
+
+	dev_dbg(&dev->dev, "initializing config\n");
+
+	init_waitqueue_head(&xen_pcibk_aer_wait_queue);
+	err = xen_pcibk_config_init_dev(dev);
+	if (err)
+		goto out;
+
+	/* HACK: Force device (& ACPI) to determine what IRQ it's on - we
+	 * must do this here because pcibios_enable_device may specify
+	 * the pci device's true irq (and possibly its other resources)
+	 * if they differ from what's in the configuration space.
+	 * This makes the assumption that the device's resources won't
+	 * change after this point (otherwise this code may break!)
+	 */
+	dev_dbg(&dev->dev, "enabling device\n");
+	err = pci_enable_device(dev);
+	if (err)
+		goto config_release;
+
+	if (dev->msix_cap) {
+		struct physdev_pci_device ppdev = {
+			.seg = pci_domain_nr(dev->bus),
+			.bus = dev->bus->number,
+			.devfn = dev->devfn
+		};
+
+		err = HYPERVISOR_physdev_op(PHYSDEVOP_prepare_msix, &ppdev);
+		if (err && err != -ENOSYS)
+			dev_err(&dev->dev, "MSI-X preparation failed (%d)\n",
+				err);
+	}
+
+	/* We need the device active to save the state. */
+	dev_dbg(&dev->dev, "save state of device\n");
+	pci_save_state(dev);
+	dev_data->pci_saved_state = pci_store_saved_state(dev);
+	if (!dev_data->pci_saved_state)
+		dev_err(&dev->dev, "Could not store PCI conf saved state!\n");
+	else {
+		dev_dbg(&dev->dev, "resetting (FLR, D3, etc) the device\n");
+		err = pcistub_reset_device_state(dev);
+		if (err)
+			goto config_release;
+		pci_restore_state(dev);
+	}
+
+#ifdef CONFIG_XEN_ACPI
+	if (xen_initial_domain() && xen_pvh_domain()) {
+		err = xen_acpi_get_gsi_info(dev, &gsi, &trigger, &polarity);
+		if (err) {
+			dev_err(&dev->dev, "Fail to get gsi info!\n");
+			goto config_release;
+		}
+		err = xen_pvh_setup_gsi(gsi, trigger, polarity);
+		if (err)
+			goto config_release;
+		psdev->gsi = gsi;
+	}
+#endif
+
+	/* Now disable the device (this also ensures some private device
+	 * data is setup before we export)
+	 */
+	dev_dbg(&dev->dev, "reset device\n");
+	xen_pcibk_reset_device(dev);
+
+	pci_set_dev_assigned(dev);
+	return 0;
+
+config_release:
+	xen_pcibk_config_free_dev(dev);
+
+out:
+	pci_set_drvdata(dev, NULL);
+	kfree(dev_data);
+	return err;
+}
+
+/*
+ * Because some initialization still happens on
+ * devices during fs_initcall, we need to defer
+ * full initialization of our devices until
+ * device_initcall.
+ */
+static int __init pcistub_init_devices_late(void)
+{
+	struct pcistub_device *psdev;
+	unsigned long flags;
+	int err = 0;
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+
+	while (!list_empty(&seized_devices)) {
+		psdev = container_of(seized_devices.next,
+				     struct pcistub_device, dev_list);
+		list_del(&psdev->dev_list);
+
+		spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+
+		err = pcistub_init_device(psdev);
+		if (err) {
+			dev_err(&psdev->dev->dev,
+				"error %d initializing device\n", err);
+			kfree(psdev);
+			psdev = NULL;
+		}
+
+		spin_lock_irqsave(&pcistub_devices_lock, flags);
+
+		if (psdev)
+			list_add_tail(&psdev->dev_list, &pcistub_devices);
+	}
+
+	initialize_devices = 1;
+
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+
+	return 0;
+}
+
+static void pcistub_device_id_add_list(struct pcistub_device_id *new,
+				       int domain, int bus, unsigned int devfn)
+{
+	struct pcistub_device_id *pci_dev_id;
+	unsigned long flags;
+	int found = 0;
+
+	spin_lock_irqsave(&device_ids_lock, flags);
+
+	list_for_each_entry(pci_dev_id, &pcistub_device_ids, slot_list) {
+		if (pci_dev_id->domain == domain && pci_dev_id->bus == bus &&
+		    pci_dev_id->devfn == devfn) {
+			found = 1;
+			break;
+		}
+	}
+
+	if (!found) {
+		new->domain = domain;
+		new->bus = bus;
+		new->devfn = devfn;
+		list_add_tail(&new->slot_list, &pcistub_device_ids);
+	}
+
+	spin_unlock_irqrestore(&device_ids_lock, flags);
+
+	if (found)
+		kfree(new);
+}
+
+static int pcistub_seize(struct pci_dev *dev,
+			 struct pcistub_device_id *pci_dev_id)
+{
+	struct pcistub_device *psdev;
+	unsigned long flags;
+	int err = 0;
+
+	psdev = pcistub_device_alloc(dev);
+	if (!psdev) {
+		kfree(pci_dev_id);
+		return -ENOMEM;
+	}
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+
+	if (initialize_devices) {
+		spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+
+		/* don't want irqs disabled when calling pcistub_init_device */
+		err = pcistub_init_device(psdev);
+
+		spin_lock_irqsave(&pcistub_devices_lock, flags);
+
+		if (!err)
+			list_add(&psdev->dev_list, &pcistub_devices);
+	} else {
+		dev_dbg(&dev->dev, "deferring initialization\n");
+		list_add(&psdev->dev_list, &seized_devices);
+	}
+
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+
+	if (err) {
+		kfree(pci_dev_id);
+		pcistub_device_put(psdev);
+	} else if (pci_dev_id)
+		pcistub_device_id_add_list(pci_dev_id, pci_domain_nr(dev->bus),
+					   dev->bus->number, dev->devfn);
+
+	return err;
+}
+
+static struct pci_driver xen_pcibk_pci_driver;
+
+/* Called when 'bind'. This means we must _NOT_ call pci_reset_function or
+ * other functions that take the sysfs lock. */
+static int pcistub_probe(struct pci_dev *dev, const struct pci_device_id *id)
+{
+	int err = 0, match;
+	struct pcistub_device_id *pci_dev_id = NULL;
+
+	dev_dbg(&dev->dev, "probing...\n");
+
+	match = pcistub_match(dev);
+
+	if (device_match_driver_override(&dev->dev,
+					 &xen_pcibk_pci_driver.driver) > 0 ||
+	    match) {
+
+		if (dev->hdr_type != PCI_HEADER_TYPE_NORMAL
+		    && dev->hdr_type != PCI_HEADER_TYPE_BRIDGE) {
+			dev_err(&dev->dev, "can't export pci devices that "
+				"don't have a normal (0) or bridge (1) "
+				"header type!\n");
+			err = -ENODEV;
+			goto out;
+		}
+
+		if (!match) {
+			pci_dev_id = kmalloc_obj(*pci_dev_id);
+			if (!pci_dev_id) {
+				err = -ENOMEM;
+				goto out;
+			}
+		}
+
+		dev_info(&dev->dev, "seizing device\n");
+		err = pcistub_seize(dev, pci_dev_id);
+	} else
+		/* Didn't find the device */
+		err = -ENODEV;
+
+out:
+	return err;
+}
+
+/* Called when 'unbind'. This means we must _NOT_ call pci_reset_function or
+ * other functions that take the sysfs lock. */
+static void pcistub_remove(struct pci_dev *dev)
+{
+	struct pcistub_device *psdev, *found_psdev = NULL;
+	unsigned long flags;
+
+	dev_dbg(&dev->dev, "removing\n");
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+
+	xen_pcibk_config_quirk_release(dev);
+
+	list_for_each_entry(psdev, &pcistub_devices, dev_list) {
+		if (psdev->dev == dev) {
+			found_psdev = psdev;
+			break;
+		}
+	}
+
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+
+	if (found_psdev) {
+		dev_dbg(&dev->dev, "found device to remove %s\n",
+			found_psdev->pdev ? "- in-use" : "");
+
+		if (found_psdev->pdev) {
+			int domid = xen_find_device_domain_owner(dev);
+
+			dev_warn(&dev->dev, "****** removing device %s while still in-use by domain %d! ******\n",
+			       pci_name(found_psdev->dev), domid);
+			dev_warn(&dev->dev, "****** driver domain may still access this device's i/o resources!\n");
+			dev_warn(&dev->dev, "****** shutdown driver domain before binding device\n");
+			dev_warn(&dev->dev, "****** to other drivers or domains\n");
+
+			/* N.B. This ends up calling pcistub_put_pci_dev which ends up
+			 * doing the FLR. */
+			xen_pcibk_release_pci_dev(found_psdev->pdev,
+						found_psdev->dev,
+						false /* caller holds the lock. */);
+		}
+
+		spin_lock_irqsave(&pcistub_devices_lock, flags);
+		list_del(&found_psdev->dev_list);
+		spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+
+		/* the final put for releasing from the list */
+		pcistub_device_put(found_psdev);
+	}
+}
+
+static const struct pci_device_id pcistub_ids[] = {
+	{
+	 .vendor = PCI_ANY_ID,
+	 .device = PCI_ANY_ID,
+	 .subvendor = PCI_ANY_ID,
+	 .subdevice = PCI_ANY_ID,
+	 },
+	{0,},
+};
+
+#define PCI_NODENAME_MAX 40
+static void kill_domain_by_device(struct pcistub_device *psdev)
+{
+	struct xenbus_transaction xbt;
+	int err;
+	char nodename[PCI_NODENAME_MAX];
+
+	BUG_ON(!psdev);
+	snprintf(nodename, PCI_NODENAME_MAX, "/local/domain/0/backend/pci/%d/0",
+		psdev->pdev->xdev->otherend_id);
+
+again:
+	err = xenbus_transaction_start(&xbt);
+	if (err) {
+		dev_err(&psdev->dev->dev,
+			"error %d when start xenbus transaction\n", err);
+		return;
+	}
+	/*PV AER handlers will set this flag*/
+	xenbus_printf(xbt, nodename, "aerState" , "aerfail");
+	err = xenbus_transaction_end(xbt, 0);
+	if (err) {
+		if (err == -EAGAIN)
+			goto again;
+		dev_err(&psdev->dev->dev,
+			"error %d when end xenbus transaction\n", err);
+		return;
+	}
+}
+
+/* For each aer recovery step error_detected, mmio_enabled, etc, front_end and
+ * backend need to have cooperation. In xen_pcibk, those steps will do similar
+ * jobs: send service request and waiting for front_end response.
+*/
+static pci_ers_result_t common_process(struct pcistub_device *psdev,
+				       pci_channel_state_t state, int aer_cmd,
+				       pci_ers_result_t result)
+{
+	pci_ers_result_t res = result;
+	struct xen_pcie_aer_op *aer_op;
+	struct xen_pcibk_device *pdev = psdev->pdev;
+	struct xen_pci_sharedinfo *sh_info = pdev->sh_info;
+	int ret;
+
+	/*with PV AER drivers*/
+	aer_op = &(sh_info->aer_op);
+	aer_op->cmd = aer_cmd ;
+	/*useful for error_detected callback*/
+	aer_op->err = state;
+	/*pcifront_end BDF*/
+	ret = xen_pcibk_get_pcifront_dev(psdev->dev, psdev->pdev,
+		&aer_op->domain, &aer_op->bus, &aer_op->devfn);
+	if (!ret) {
+		dev_err(&psdev->dev->dev, "failed to get pcifront device\n");
+		return PCI_ERS_RESULT_NONE;
+	}
+	wmb();
+
+	dev_dbg(&psdev->dev->dev, "aer_op %x dom %x bus %x devfn %x\n",
+			aer_cmd, aer_op->domain, aer_op->bus, aer_op->devfn);
+	/*local flag to mark there's aer request, xen_pcibk callback will use
+	* this flag to judge whether we need to check pci-front give aer
+	* service ack signal
+	*/
+	set_bit(_PCIB_op_pending, (unsigned long *)&pdev->flags);
+
+	/*It is possible that a pcifront conf_read_write ops request invokes
+	* the callback which cause the spurious execution of wake_up.
+	* Yet it is harmless and better than a spinlock here
+	*/
+	set_bit(_XEN_PCIB_active,
+		(unsigned long *)&sh_info->flags);
+	wmb();
+	notify_remote_via_irq(pdev->evtchn_irq);
+
+	/* Enable IRQ to signal "request done". */
+	xen_pcibk_lateeoi(pdev, 0);
+
+	ret = wait_event_timeout(xen_pcibk_aer_wait_queue,
+				 !(test_bit(_XEN_PCIB_active, (unsigned long *)
+				 &sh_info->flags)), 300*HZ);
+
+	/* Enable IRQ for pcifront request if not already active. */
+	if (!test_bit(_PDEVF_op_active, &pdev->flags))
+		xen_pcibk_lateeoi(pdev, 0);
+
+	if (!ret) {
+		if (test_bit(_XEN_PCIB_active,
+			(unsigned long *)&sh_info->flags)) {
+			dev_err(&psdev->dev->dev,
+				"pcifront aer process not responding!\n");
+			clear_bit(_XEN_PCIB_active,
+			  (unsigned long *)&sh_info->flags);
+			aer_op->err = PCI_ERS_RESULT_NONE;
+			return res;
+		}
+	}
+	clear_bit(_PCIB_op_pending, (unsigned long *)&pdev->flags);
+
+	res = (__force pci_ers_result_t)aer_op->err;
+	return res;
+}
+
+/*
+* xen_pcibk_slot_reset: it will send the slot_reset request to  pcifront in case
+* of the device driver could provide this service, and then wait for pcifront
+* ack.
+* @dev: pointer to PCI devices
+* return value is used by aer_core do_recovery policy
+*/
+static pci_ers_result_t xen_pcibk_slot_reset(struct pci_dev *dev)
+{
+	struct pcistub_device *psdev;
+	pci_ers_result_t result;
+
+	result = PCI_ERS_RESULT_RECOVERED;
+	dev_dbg(&dev->dev, "xen_pcibk_slot_reset(bus:%x,devfn:%x)\n",
+		dev->bus->number, dev->devfn);
+
+	down_write(&pcistub_sem);
+	psdev = pcistub_device_find(pci_domain_nr(dev->bus),
+				dev->bus->number,
+				PCI_SLOT(dev->devfn),
+				PCI_FUNC(dev->devfn));
+
+	if (!psdev || !psdev->pdev) {
+		dev_err(&dev->dev, "device is not found/assigned\n");
+		goto end;
+	}
+
+	if (!psdev->pdev->sh_info) {
+		dev_err(&dev->dev, "device is not connected or owned"
+			" by HVM, kill it\n");
+		kill_domain_by_device(psdev);
+		goto end;
+	}
+
+	if (!test_bit(_XEN_PCIB_AERHANDLER,
+		(unsigned long *)&psdev->pdev->sh_info->flags)) {
+		dev_err(&dev->dev,
+			"guest with no AER driver should have been killed\n");
+		goto end;
+	}
+	result = common_process(psdev, pci_channel_io_normal, XEN_PCI_OP_aer_slotreset, result);
+
+	if (result == PCI_ERS_RESULT_NONE ||
+		result == PCI_ERS_RESULT_DISCONNECT) {
+		dev_dbg(&dev->dev,
+			"No AER slot_reset service or disconnected!\n");
+		kill_domain_by_device(psdev);
+	}
+end:
+	if (psdev)
+		pcistub_device_put(psdev);
+	up_write(&pcistub_sem);
+	return result;
+
+}
+
+
+/*xen_pcibk_mmio_enabled: it will send the mmio_enabled request to  pcifront
+* in case of the device driver could provide this service, and then wait
+* for pcifront ack
+* @dev: pointer to PCI devices
+* return value is used by aer_core do_recovery policy
+*/
+
+static pci_ers_result_t xen_pcibk_mmio_enabled(struct pci_dev *dev)
+{
+	struct pcistub_device *psdev;
+	pci_ers_result_t result;
+
+	result = PCI_ERS_RESULT_RECOVERED;
+	dev_dbg(&dev->dev, "xen_pcibk_mmio_enabled(bus:%x,devfn:%x)\n",
+		dev->bus->number, dev->devfn);
+
+	down_write(&pcistub_sem);
+	psdev = pcistub_device_find(pci_domain_nr(dev->bus),
+				dev->bus->number,
+				PCI_SLOT(dev->devfn),
+				PCI_FUNC(dev->devfn));
+
+	if (!psdev || !psdev->pdev) {
+		dev_err(&dev->dev, "device is not found/assigned\n");
+		goto end;
+	}
+
+	if (!psdev->pdev->sh_info) {
+		dev_err(&dev->dev, "device is not connected or owned"
+			" by HVM, kill it\n");
+		kill_domain_by_device(psdev);
+		goto end;
+	}
+
+	if (!test_bit(_XEN_PCIB_AERHANDLER,
+		(unsigned long *)&psdev->pdev->sh_info->flags)) {
+		dev_err(&dev->dev,
+			"guest with no AER driver should have been killed\n");
+		goto end;
+	}
+	result = common_process(psdev, pci_channel_io_normal, XEN_PCI_OP_aer_mmio, result);
+
+	if (result == PCI_ERS_RESULT_NONE ||
+		result == PCI_ERS_RESULT_DISCONNECT) {
+		dev_dbg(&dev->dev,
+			"No AER mmio_enabled service or disconnected!\n");
+		kill_domain_by_device(psdev);
+	}
+end:
+	if (psdev)
+		pcistub_device_put(psdev);
+	up_write(&pcistub_sem);
+	return result;
+}
+
+/*xen_pcibk_error_detected: it will send the error_detected request to  pcifront
+* in case of the device driver could provide this service, and then wait
+* for pcifront ack.
+* @dev: pointer to PCI devices
+* @error: the current PCI connection state
+* return value is used by aer_core do_recovery policy
+*/
+
+static pci_ers_result_t xen_pcibk_error_detected(struct pci_dev *dev,
+	pci_channel_state_t error)
+{
+	struct pcistub_device *psdev;
+	pci_ers_result_t result;
+
+	result = PCI_ERS_RESULT_CAN_RECOVER;
+	dev_dbg(&dev->dev, "xen_pcibk_error_detected(bus:%x,devfn:%x)\n",
+		dev->bus->number, dev->devfn);
+
+	down_write(&pcistub_sem);
+	psdev = pcistub_device_find(pci_domain_nr(dev->bus),
+				dev->bus->number,
+				PCI_SLOT(dev->devfn),
+				PCI_FUNC(dev->devfn));
+
+	if (!psdev || !psdev->pdev) {
+		dev_err(&dev->dev, "device is not found/assigned\n");
+		goto end;
+	}
+
+	if (!psdev->pdev->sh_info) {
+		dev_err(&dev->dev, "device is not connected or owned"
+			" by HVM, kill it\n");
+		kill_domain_by_device(psdev);
+		goto end;
+	}
+
+	/*Guest owns the device yet no aer handler regiested, kill guest*/
+	if (!test_bit(_XEN_PCIB_AERHANDLER,
+		(unsigned long *)&psdev->pdev->sh_info->flags)) {
+		dev_dbg(&dev->dev, "guest may have no aer driver, kill it\n");
+		kill_domain_by_device(psdev);
+		goto end;
+	}
+	result = common_process(psdev, error, XEN_PCI_OP_aer_detected, result);
+
+	if (result == PCI_ERS_RESULT_NONE ||
+		result == PCI_ERS_RESULT_DISCONNECT) {
+		dev_dbg(&dev->dev,
+			"No AER error_detected service or disconnected!\n");
+		kill_domain_by_device(psdev);
+	}
+end:
+	if (psdev)
+		pcistub_device_put(psdev);
+	up_write(&pcistub_sem);
+	return result;
+}
+
+/*xen_pcibk_error_resume: it will send the error_resume request to  pcifront
+* in case of the device driver could provide this service, and then wait
+* for pcifront ack.
+* @dev: pointer to PCI devices
+*/
+
+static void xen_pcibk_error_resume(struct pci_dev *dev)
+{
+	struct pcistub_device *psdev;
+
+	dev_dbg(&dev->dev, "xen_pcibk_error_resume(bus:%x,devfn:%x)\n",
+		dev->bus->number, dev->devfn);
+
+	down_write(&pcistub_sem);
+	psdev = pcistub_device_find(pci_domain_nr(dev->bus),
+				dev->bus->number,
+				PCI_SLOT(dev->devfn),
+				PCI_FUNC(dev->devfn));
+
+	if (!psdev || !psdev->pdev) {
+		dev_err(&dev->dev, "device is not found/assigned\n");
+		goto end;
+	}
+
+	if (!psdev->pdev->sh_info) {
+		dev_err(&dev->dev, "device is not connected or owned"
+			" by HVM, kill it\n");
+		kill_domain_by_device(psdev);
+		goto end;
+	}
+
+	if (!test_bit(_XEN_PCIB_AERHANDLER,
+		(unsigned long *)&psdev->pdev->sh_info->flags)) {
+		dev_err(&dev->dev,
+			"guest with no AER driver should have been killed\n");
+		kill_domain_by_device(psdev);
+		goto end;
+	}
+	common_process(psdev, pci_channel_io_normal, XEN_PCI_OP_aer_resume,
+		       PCI_ERS_RESULT_RECOVERED);
+end:
+	if (psdev)
+		pcistub_device_put(psdev);
+	up_write(&pcistub_sem);
+	return;
+}
+
+/*add xen_pcibk AER handling*/
+static const struct pci_error_handlers xen_pcibk_error_handler = {
+	.error_detected = xen_pcibk_error_detected,
+	.mmio_enabled = xen_pcibk_mmio_enabled,
+	.slot_reset = xen_pcibk_slot_reset,
+	.resume = xen_pcibk_error_resume,
+};
+
+/*
+ * Note: There is no MODULE_DEVICE_TABLE entry here because this isn't
+ * for a normal device. I don't want it to be loaded automatically.
+ */
+
+static struct pci_driver xen_pcibk_pci_driver = {
+	/* The name should be xen_pciback, but until the tools are updated
+	 * we will keep it as pciback. */
+	.name = PCISTUB_DRIVER_NAME,
+	.id_table = pcistub_ids,
+	.probe = pcistub_probe,
+	.remove = pcistub_remove,
+	.err_handler = &xen_pcibk_error_handler,
+};
+
+static inline int str_to_slot(const char *buf, int *domain, int *bus,
+			      int *slot, int *func)
+{
+	int parsed = 0;
+
+	switch (sscanf(buf, " %x:%x:%x.%x %n", domain, bus, slot, func,
+		       &parsed)) {
+	case 3:
+		*func = -1;
+		sscanf(buf, " %x:%x:%x.* %n", domain, bus, slot, &parsed);
+		break;
+	case 2:
+		*slot = *func = -1;
+		sscanf(buf, " %x:%x:*.* %n", domain, bus, &parsed);
+		break;
+	}
+	if (parsed && !buf[parsed])
+		return 0;
+
+	/* try again without domain */
+	*domain = 0;
+	switch (sscanf(buf, " %x:%x.%x %n", bus, slot, func, &parsed)) {
+	case 2:
+		*func = -1;
+		sscanf(buf, " %x:%x.* %n", bus, slot, &parsed);
+		break;
+	case 1:
+		*slot = *func = -1;
+		sscanf(buf, " %x:*.* %n", bus, &parsed);
+		break;
+	}
+	if (parsed && !buf[parsed])
+		return 0;
+
+	return -EINVAL;
+}
+
+static inline int str_to_quirk(const char *buf, int *domain, int *bus, int
+			       *slot, int *func, int *reg, int *size, int *mask)
+{
+	int parsed = 0;
+
+	sscanf(buf, " %x:%x:%x.%x-%x:%x:%x %n", domain, bus, slot, func,
+	       reg, size, mask, &parsed);
+	if (parsed && !buf[parsed])
+		return 0;
+
+	/* try again without domain */
+	*domain = 0;
+	sscanf(buf, " %x:%x.%x-%x:%x:%x %n", bus, slot, func, reg, size,
+	       mask, &parsed);
+	if (parsed && !buf[parsed])
+		return 0;
+
+	return -EINVAL;
+}
+
+static int pcistub_device_id_add(int domain, int bus, int slot, int func)
+{
+	struct pcistub_device_id *pci_dev_id;
+	int rc = 0, devfn = PCI_DEVFN(slot, func);
+
+	if (slot < 0) {
+		for (slot = 0; !rc && slot < 32; ++slot)
+			rc = pcistub_device_id_add(domain, bus, slot, func);
+		return rc;
+	}
+
+	if (func < 0) {
+		for (func = 0; !rc && func < 8; ++func)
+			rc = pcistub_device_id_add(domain, bus, slot, func);
+		return rc;
+	}
+
+	if ((
+#if !defined(MODULE) /* pci_domains_supported is not being exported */ \
+    || !defined(CONFIG_PCI_DOMAINS)
+	     !pci_domains_supported ? domain :
+#endif
+	     domain < 0 || domain > 0xffff)
+	    || bus < 0 || bus > 0xff
+	    || PCI_SLOT(devfn) != slot
+	    || PCI_FUNC(devfn) != func)
+		return -EINVAL;
+
+	pci_dev_id = kmalloc_obj(*pci_dev_id);
+	if (!pci_dev_id)
+		return -ENOMEM;
+
+	pr_debug("wants to seize %04x:%02x:%02x.%d\n",
+		 domain, bus, slot, func);
+
+	pcistub_device_id_add_list(pci_dev_id, domain, bus, devfn);
+
+	return 0;
+}
+
+static int pcistub_device_id_remove(int domain, int bus, int slot, int func)
+{
+	struct pcistub_device_id *pci_dev_id, *t;
+	int err = -ENOENT;
+	unsigned long flags;
+
+	spin_lock_irqsave(&device_ids_lock, flags);
+	list_for_each_entry_safe(pci_dev_id, t, &pcistub_device_ids,
+				 slot_list) {
+		if (pci_dev_id->domain == domain && pci_dev_id->bus == bus
+		    && (slot < 0 || PCI_SLOT(pci_dev_id->devfn) == slot)
+		    && (func < 0 || PCI_FUNC(pci_dev_id->devfn) == func)) {
+			/* Don't break; here because it's possible the same
+			 * slot could be in the list more than once
+			 */
+			list_del(&pci_dev_id->slot_list);
+			kfree(pci_dev_id);
+
+			err = 0;
+
+			pr_debug("removed %04x:%02x:%02x.%d from seize list\n",
+				 domain, bus, slot, func);
+		}
+	}
+	spin_unlock_irqrestore(&device_ids_lock, flags);
+
+	return err;
+}
+
+static int pcistub_reg_add(int domain, int bus, int slot, int func,
+			   unsigned int reg, unsigned int size,
+			   unsigned int mask)
+{
+	int err = 0;
+	struct pcistub_device *psdev;
+	struct pci_dev *dev;
+	struct config_field *field;
+
+	if (reg > 0xfff || (size < 4 && (mask >> (size * 8))))
+		return -EINVAL;
+
+	psdev = pcistub_device_find(domain, bus, slot, func);
+	if (!psdev) {
+		err = -ENODEV;
+		goto out;
+	}
+	dev = psdev->dev;
+
+	field = kzalloc_obj(*field);
+	if (!field) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	field->offset = reg;
+	field->size = size;
+	field->mask = mask;
+	field->init = NULL;
+	field->reset = NULL;
+	field->release = NULL;
+	field->clean = xen_pcibk_config_field_free;
+
+	err = xen_pcibk_config_quirks_add_field(dev, field);
+	if (err)
+		kfree(field);
+out:
+	if (psdev)
+		pcistub_device_put(psdev);
+	return err;
+}
+
+static ssize_t new_slot_store(struct device_driver *drv, const char *buf,
+			      size_t count)
+{
+	int domain, bus, slot, func;
+	int err;
+
+	err = str_to_slot(buf, &domain, &bus, &slot, &func);
+	if (err)
+		goto out;
+
+	err = pcistub_device_id_add(domain, bus, slot, func);
+
+out:
+	if (!err)
+		err = count;
+	return err;
+}
+static DRIVER_ATTR_WO(new_slot);
+
+static ssize_t remove_slot_store(struct device_driver *drv, const char *buf,
+				 size_t count)
+{
+	int domain, bus, slot, func;
+	int err;
+
+	err = str_to_slot(buf, &domain, &bus, &slot, &func);
+	if (err)
+		goto out;
+
+	err = pcistub_device_id_remove(domain, bus, slot, func);
+
+out:
+	if (!err)
+		err = count;
+	return err;
+}
+static DRIVER_ATTR_WO(remove_slot);
+
+static ssize_t slots_show(struct device_driver *drv, char *buf)
+{
+	struct pcistub_device_id *pci_dev_id;
+	size_t count = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&device_ids_lock, flags);
+	list_for_each_entry(pci_dev_id, &pcistub_device_ids, slot_list) {
+		if (count >= PAGE_SIZE)
+			break;
+
+		count += sysfs_emit_at(buf, count,
+				   "%04x:%02x:%02x.%d\n",
+				   pci_dev_id->domain, pci_dev_id->bus,
+				   PCI_SLOT(pci_dev_id->devfn),
+				   PCI_FUNC(pci_dev_id->devfn));
+	}
+	spin_unlock_irqrestore(&device_ids_lock, flags);
+
+	return count;
+}
+static DRIVER_ATTR_RO(slots);
+
+static ssize_t irq_handlers_show(struct device_driver *drv, char *buf)
+{
+	struct pcistub_device *psdev;
+	struct xen_pcibk_dev_data *dev_data;
+	size_t count = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+	list_for_each_entry(psdev, &pcistub_devices, dev_list) {
+		if (count >= PAGE_SIZE)
+			break;
+		if (!psdev->dev)
+			continue;
+		dev_data = pci_get_drvdata(psdev->dev);
+		if (!dev_data)
+			continue;
+		count +=
+		    sysfs_emit_at(buf, count,
+			      "%s:%s:%sing:%ld\n",
+			      pci_name(psdev->dev),
+			      dev_data->isr_on ? "on" : "off",
+			      dev_data->ack_intr ? "ack" : "not ack",
+			      dev_data->handled);
+	}
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+	return count;
+}
+static DRIVER_ATTR_RO(irq_handlers);
+
+static ssize_t irq_handler_state_store(struct device_driver *drv,
+				       const char *buf, size_t count)
+{
+	struct pcistub_device *psdev;
+	struct xen_pcibk_dev_data *dev_data;
+	int domain, bus, slot, func;
+	int err;
+
+	err = str_to_slot(buf, &domain, &bus, &slot, &func);
+	if (err)
+		return err;
+
+	psdev = pcistub_device_find(domain, bus, slot, func);
+	if (!psdev) {
+		err = -ENOENT;
+		goto out;
+	}
+
+	dev_data = pci_get_drvdata(psdev->dev);
+	if (!dev_data) {
+		err = -ENOENT;
+		goto out;
+	}
+
+	dev_dbg(&psdev->dev->dev, "%s fake irq handler: %d->%d\n",
+		dev_data->irq_name, dev_data->isr_on,
+		!dev_data->isr_on);
+
+	dev_data->isr_on = !(dev_data->isr_on);
+	if (dev_data->isr_on)
+		dev_data->ack_intr = 1;
+out:
+	if (psdev)
+		pcistub_device_put(psdev);
+	if (!err)
+		err = count;
+	return err;
+}
+static DRIVER_ATTR_WO(irq_handler_state);
+
+static ssize_t quirks_store(struct device_driver *drv, const char *buf,
+			    size_t count)
+{
+	int domain, bus, slot, func, reg, size, mask;
+	int err;
+
+	err = str_to_quirk(buf, &domain, &bus, &slot, &func, &reg, &size,
+			   &mask);
+	if (err)
+		goto out;
+
+	err = pcistub_reg_add(domain, bus, slot, func, reg, size, mask);
+
+out:
+	if (!err)
+		err = count;
+	return err;
+}
+
+static ssize_t quirks_show(struct device_driver *drv, char *buf)
+{
+	int count = 0;
+	unsigned long flags;
+	struct xen_pcibk_config_quirk *quirk;
+	struct xen_pcibk_dev_data *dev_data;
+	const struct config_field *field;
+	const struct config_field_entry *cfg_entry;
+
+	spin_lock_irqsave(&device_ids_lock, flags);
+	list_for_each_entry(quirk, &xen_pcibk_quirks, quirks_list) {
+		if (count >= PAGE_SIZE)
+			goto out;
+
+		count += sysfs_emit_at(buf, count,
+				   "%02x:%02x.%01x\n\t%04x:%04x:%04x:%04x\n",
+				   quirk->pdev->bus->number,
+				   PCI_SLOT(quirk->pdev->devfn),
+				   PCI_FUNC(quirk->pdev->devfn),
+				   quirk->devid.vendor, quirk->devid.device,
+				   quirk->devid.subvendor,
+				   quirk->devid.subdevice);
+
+		dev_data = pci_get_drvdata(quirk->pdev);
+
+		list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
+			field = cfg_entry->field;
+			if (count >= PAGE_SIZE)
+				goto out;
+
+			count += sysfs_emit_at(buf, count,
+					   "\t\t%08x:%01x:%08x\n",
+					   cfg_entry->base_offset +
+					   field->offset, field->size,
+					   field->mask);
+		}
+	}
+
+out:
+	spin_unlock_irqrestore(&device_ids_lock, flags);
+
+	return count;
+}
+static DRIVER_ATTR_RW(quirks);
+
+static ssize_t permissive_store(struct device_driver *drv, const char *buf,
+				size_t count)
+{
+	int domain, bus, slot, func;
+	int err;
+	struct pcistub_device *psdev;
+	struct xen_pcibk_dev_data *dev_data;
+
+	err = str_to_slot(buf, &domain, &bus, &slot, &func);
+	if (err)
+		goto out;
+
+	psdev = pcistub_device_find(domain, bus, slot, func);
+	if (!psdev) {
+		err = -ENODEV;
+		goto out;
+	}
+
+	dev_data = pci_get_drvdata(psdev->dev);
+	/* the driver data for a device should never be null at this point */
+	if (!dev_data) {
+		err = -ENXIO;
+		goto release;
+	}
+	if (!dev_data->permissive) {
+		dev_data->permissive = 1;
+		/* Let user know that what they're doing could be unsafe */
+		dev_warn(&psdev->dev->dev, "enabling permissive mode "
+			 "configuration space accesses!\n");
+		dev_warn(&psdev->dev->dev,
+			 "permissive mode is potentially unsafe!\n");
+	}
+release:
+	pcistub_device_put(psdev);
+out:
+	if (!err)
+		err = count;
+	return err;
+}
+
+static ssize_t permissive_show(struct device_driver *drv, char *buf)
+{
+	struct pcistub_device *psdev;
+	struct xen_pcibk_dev_data *dev_data;
+	size_t count = 0;
+	unsigned long flags;
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+	list_for_each_entry(psdev, &pcistub_devices, dev_list) {
+		if (count >= PAGE_SIZE)
+			break;
+		if (!psdev->dev)
+			continue;
+		dev_data = pci_get_drvdata(psdev->dev);
+		if (!dev_data || !dev_data->permissive)
+			continue;
+		count +=
+		    sysfs_emit_at(buf, count, "%s\n",
+			      pci_name(psdev->dev));
+	}
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+	return count;
+}
+static DRIVER_ATTR_RW(permissive);
+
+static ssize_t allow_interrupt_control_store(struct device_driver *drv,
+					     const char *buf, size_t count)
+{
+	int domain, bus, slot, func;
+	int err;
+	struct pcistub_device *psdev;
+	struct xen_pcibk_dev_data *dev_data;
+
+	err = str_to_slot(buf, &domain, &bus, &slot, &func);
+	if (err)
+		goto out;
+
+	psdev = pcistub_device_find(domain, bus, slot, func);
+	if (!psdev) {
+		err = -ENODEV;
+		goto out;
+	}
+
+	dev_data = pci_get_drvdata(psdev->dev);
+	/* the driver data for a device should never be null at this point */
+	if (!dev_data) {
+		err = -ENXIO;
+		goto release;
+	}
+	dev_data->allow_interrupt_control = 1;
+release:
+	pcistub_device_put(psdev);
+out:
+	if (!err)
+		err = count;
+	return err;
+}
+
+static ssize_t allow_interrupt_control_show(struct device_driver *drv,
+					    char *buf)
+{
+	struct pcistub_device *psdev;
+	struct xen_pcibk_dev_data *dev_data;
+	size_t count = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+	list_for_each_entry(psdev, &pcistub_devices, dev_list) {
+		if (count >= PAGE_SIZE)
+			break;
+		if (!psdev->dev)
+			continue;
+		dev_data = pci_get_drvdata(psdev->dev);
+		if (!dev_data || !dev_data->allow_interrupt_control)
+			continue;
+		count +=
+		    sysfs_emit_at(buf, count, "%s\n",
+			      pci_name(psdev->dev));
+	}
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+	return count;
+}
+static DRIVER_ATTR_RW(allow_interrupt_control);
+
+static void pcistub_exit(void)
+{
+	driver_remove_file(&xen_pcibk_pci_driver.driver, &driver_attr_new_slot);
+	driver_remove_file(&xen_pcibk_pci_driver.driver,
+			   &driver_attr_remove_slot);
+	driver_remove_file(&xen_pcibk_pci_driver.driver, &driver_attr_slots);
+	driver_remove_file(&xen_pcibk_pci_driver.driver, &driver_attr_quirks);
+	driver_remove_file(&xen_pcibk_pci_driver.driver,
+			   &driver_attr_permissive);
+	driver_remove_file(&xen_pcibk_pci_driver.driver,
+			   &driver_attr_allow_interrupt_control);
+	driver_remove_file(&xen_pcibk_pci_driver.driver,
+			   &driver_attr_irq_handlers);
+	driver_remove_file(&xen_pcibk_pci_driver.driver,
+			   &driver_attr_irq_handler_state);
+	pci_unregister_driver(&xen_pcibk_pci_driver);
+}
+
+static int __init pcistub_init(void)
+{
+	int pos = 0;
+	int err = 0;
+	int domain, bus, slot, func;
+	int parsed;
+
+	if (pci_devs_to_hide && *pci_devs_to_hide) {
+		do {
+			parsed = 0;
+
+			err = sscanf(pci_devs_to_hide + pos,
+				     " (%x:%x:%x.%x) %n",
+				     &domain, &bus, &slot, &func, &parsed);
+			switch (err) {
+			case 3:
+				func = -1;
+				sscanf(pci_devs_to_hide + pos,
+				       " (%x:%x:%x.*) %n",
+				       &domain, &bus, &slot, &parsed);
+				break;
+			case 2:
+				slot = func = -1;
+				sscanf(pci_devs_to_hide + pos,
+				       " (%x:%x:*.*) %n",
+				       &domain, &bus, &parsed);
+				break;
+			}
+
+			if (!parsed) {
+				domain = 0;
+				err = sscanf(pci_devs_to_hide + pos,
+					     " (%x:%x.%x) %n",
+					     &bus, &slot, &func, &parsed);
+				switch (err) {
+				case 2:
+					func = -1;
+					sscanf(pci_devs_to_hide + pos,
+					       " (%x:%x.*) %n",
+					       &bus, &slot, &parsed);
+					break;
+				case 1:
+					slot = func = -1;
+					sscanf(pci_devs_to_hide + pos,
+					       " (%x:*.*) %n",
+					       &bus, &parsed);
+					break;
+				}
+			}
+
+			if (parsed <= 0)
+				goto parse_error;
+
+			err = pcistub_device_id_add(domain, bus, slot, func);
+			if (err)
+				goto out;
+
+			pos += parsed;
+		} while (pci_devs_to_hide[pos]);
+	}
+
+	/* If we're the first PCI Device Driver to register, we're the
+	 * first one to get offered PCI devices as they become
+	 * available (and thus we can be the first to grab them)
+	 */
+	err = pci_register_driver(&xen_pcibk_pci_driver);
+	if (err < 0)
+		goto out;
+
+	err = driver_create_file(&xen_pcibk_pci_driver.driver,
+				 &driver_attr_new_slot);
+	if (!err)
+		err = driver_create_file(&xen_pcibk_pci_driver.driver,
+					 &driver_attr_remove_slot);
+	if (!err)
+		err = driver_create_file(&xen_pcibk_pci_driver.driver,
+					 &driver_attr_slots);
+	if (!err)
+		err = driver_create_file(&xen_pcibk_pci_driver.driver,
+					 &driver_attr_quirks);
+	if (!err)
+		err = driver_create_file(&xen_pcibk_pci_driver.driver,
+					 &driver_attr_permissive);
+	if (!err)
+		err = driver_create_file(&xen_pcibk_pci_driver.driver,
+					 &driver_attr_allow_interrupt_control);
+
+	if (!err)
+		err = driver_create_file(&xen_pcibk_pci_driver.driver,
+					 &driver_attr_irq_handlers);
+	if (!err)
+		err = driver_create_file(&xen_pcibk_pci_driver.driver,
+					&driver_attr_irq_handler_state);
+	if (err)
+		pcistub_exit();
+
+out:
+	return err;
+
+parse_error:
+	pr_err("Error parsing pci_devs_to_hide at \"%s\"\n",
+	       pci_devs_to_hide + pos);
+	return -EINVAL;
+}
+
+#ifndef MODULE
+/*
+ * fs_initcall happens before device_initcall
+ * so xen_pcibk *should* get called first (b/c we
+ * want to suck up any device before other drivers
+ * get a chance by being the first pci device
+ * driver to register)
+ */
+fs_initcall(pcistub_init);
+#endif
+
+#ifdef CONFIG_PCI_IOV
+static struct pcistub_device *find_vfs(const struct pci_dev *pdev)
+{
+	struct pcistub_device *psdev = NULL;
+	unsigned long flags;
+	bool found = false;
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+	list_for_each_entry(psdev, &pcistub_devices, dev_list) {
+		if (!psdev->pdev && psdev->dev != pdev
+		    && pci_physfn(psdev->dev) == pdev) {
+			found = true;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+	if (found)
+		return psdev;
+	return NULL;
+}
+
+static int pci_stub_notifier(struct notifier_block *nb,
+			     unsigned long action, void *data)
+{
+	struct device *dev = data;
+	const struct pci_dev *pdev = to_pci_dev(dev);
+
+	if (action != BUS_NOTIFY_UNBIND_DRIVER)
+		return NOTIFY_DONE;
+
+	if (!pdev->is_physfn)
+		return NOTIFY_DONE;
+
+	for (;;) {
+		struct pcistub_device *psdev = find_vfs(pdev);
+		if (!psdev)
+			break;
+		device_release_driver(&psdev->dev->dev);
+	}
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block pci_stub_nb = {
+	.notifier_call = pci_stub_notifier,
+};
+#endif
+
+static int __init xen_pcibk_init(void)
+{
+	int err;
+
+	if (!xen_initial_domain())
+		return -ENODEV;
+
+	err = xen_pcibk_config_init();
+	if (err)
+		return err;
+
+#ifdef MODULE
+	err = pcistub_init();
+	if (err < 0)
+		return err;
+#endif
+
+	pcistub_init_devices_late();
+	err = xen_pcibk_xenbus_register();
+	if (err)
+		pcistub_exit();
+#ifdef CONFIG_PCI_IOV
+	else
+		bus_register_notifier(&pci_bus_type, &pci_stub_nb);
+#endif
+
+#ifdef CONFIG_XEN_ACPI
+	xen_acpi_register_get_gsi_func(pcistub_get_gsi_from_sbdf);
+#endif
+
+	return err;
+}
+
+static void __exit xen_pcibk_cleanup(void)
+{
+#ifdef CONFIG_XEN_ACPI
+	xen_acpi_register_get_gsi_func(NULL);
+#endif
+
+#ifdef CONFIG_PCI_IOV
+	bus_unregister_notifier(&pci_bus_type, &pci_stub_nb);
+#endif
+	xen_pcibk_xenbus_unregister();
+	pcistub_exit();
+}
+
+module_init(xen_pcibk_init);
+module_exit(xen_pcibk_cleanup);
+
+MODULE_DESCRIPTION("Xen PCI-device stub driver");
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS("xen-backend:pci");
diff --git a/drivers/xen/xen-pciback/pciback.h b/drivers/xen/xen-pciback/pciback.h
new file mode 100644
index 000000000..b786c1f74
--- /dev/null
+++ b/drivers/xen/xen-pciback/pciback.h
@@ -0,0 +1,201 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * PCI Backend Common Data Structures & Function Declarations
+ *
+ *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ */
+#ifndef __XEN_PCIBACK_H__
+#define __XEN_PCIBACK_H__
+
+#include <linux/pci.h>
+#include <linux/interrupt.h>
+#include <xen/xenbus.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/workqueue.h>
+#include <linux/atomic.h>
+#include <xen/events.h>
+#include <xen/interface/io/pciif.h>
+
+#define DRV_NAME	"xen-pciback"
+
+struct pci_dev_entry {
+	struct list_head list;
+	struct pci_dev *dev;
+};
+
+#define _PDEVF_op_active	(0)
+#define PDEVF_op_active		(1<<(_PDEVF_op_active))
+#define _PCIB_op_pending	(1)
+#define PCIB_op_pending		(1<<(_PCIB_op_pending))
+#define _EOI_pending		(2)
+#define EOI_pending		(1<<(_EOI_pending))
+
+struct xen_pcibk_device {
+	void *pci_dev_data;
+	struct mutex dev_lock;
+	struct xenbus_device *xdev;
+	struct xenbus_watch be_watch;
+	u8 be_watching;
+	int evtchn_irq;
+	struct xen_pci_sharedinfo *sh_info;
+	unsigned long flags;
+	struct work_struct op_work;
+	struct xen_pci_op op;
+};
+
+struct xen_pcibk_dev_data {
+	struct list_head config_fields;
+	struct pci_saved_state *pci_saved_state;
+	unsigned int permissive:1;
+	unsigned int allow_interrupt_control:1;
+	unsigned int warned_on_write:1;
+	unsigned int enable_intx:1;
+	unsigned int isr_on:1; /* Whether the IRQ handler is installed. */
+	unsigned int ack_intr:1; /* .. and ACK-ing */
+	unsigned long handled;
+	unsigned int irq; /* Saved in case device transitions to MSI/MSI-X */
+	char irq_name[]; /* xen-pcibk[000:04:00.0] */
+};
+
+/* Used by XenBus and xen_pcibk_ops.c */
+extern wait_queue_head_t xen_pcibk_aer_wait_queue;
+/* Used by pcistub.c and conf_space_quirks.c */
+extern struct list_head xen_pcibk_quirks;
+
+/* Get/Put PCI Devices that are hidden from the PCI Backend Domain */
+struct pci_dev *pcistub_get_pci_dev_by_slot(struct xen_pcibk_device *pdev,
+					    int domain, int bus,
+					    int slot, int func);
+void pcistub_put_pci_dev(struct pci_dev *dev);
+
+static inline bool xen_pcibk_pv_support(void)
+{
+	return IS_ENABLED(CONFIG_XEN_PCIDEV_BACKEND);
+}
+
+/* Ensure a device is turned off or reset */
+void xen_pcibk_reset_device(struct pci_dev *pdev);
+
+/* Access a virtual configuration space for a PCI device */
+int xen_pcibk_config_init(void);
+int xen_pcibk_config_init_dev(struct pci_dev *dev);
+void xen_pcibk_config_free_dyn_fields(struct pci_dev *dev);
+void xen_pcibk_config_reset_dev(struct pci_dev *dev);
+void xen_pcibk_config_free_dev(struct pci_dev *dev);
+int xen_pcibk_config_read(struct pci_dev *dev, int offset, int size,
+			  u32 *ret_val);
+int xen_pcibk_config_write(struct pci_dev *dev, int offset, int size,
+			   u32 value);
+
+/* Handle requests for specific devices from the frontend */
+typedef int (*publish_pci_dev_cb) (struct xen_pcibk_device *pdev,
+				   unsigned int domain, unsigned int bus,
+				   unsigned int devfn, unsigned int devid);
+typedef int (*publish_pci_root_cb) (struct xen_pcibk_device *pdev,
+				    unsigned int domain, unsigned int bus);
+
+/* Backend registration for the two types of BDF representation:
+ *  vpci - BDFs start at 00
+ *  passthrough - BDFs are exactly like in the host.
+ */
+struct xen_pcibk_backend {
+	const char *name;
+	int (*init)(struct xen_pcibk_device *pdev);
+	void (*free)(struct xen_pcibk_device *pdev);
+	int (*find)(struct pci_dev *pcidev, struct xen_pcibk_device *pdev,
+		    unsigned int *domain, unsigned int *bus,
+		    unsigned int *devfn);
+	int (*publish)(struct xen_pcibk_device *pdev, publish_pci_root_cb cb);
+	void (*release)(struct xen_pcibk_device *pdev, struct pci_dev *dev,
+                        bool lock);
+	int (*add)(struct xen_pcibk_device *pdev, struct pci_dev *dev,
+		   int devid, publish_pci_dev_cb publish_cb);
+	struct pci_dev *(*get)(struct xen_pcibk_device *pdev,
+			       unsigned int domain, unsigned int bus,
+			       unsigned int devfn);
+};
+
+extern const struct xen_pcibk_backend xen_pcibk_vpci_backend;
+extern const struct xen_pcibk_backend xen_pcibk_passthrough_backend;
+extern const struct xen_pcibk_backend *xen_pcibk_backend;
+
+static inline int xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev,
+					struct pci_dev *dev,
+					int devid,
+					publish_pci_dev_cb publish_cb)
+{
+	if (xen_pcibk_backend && xen_pcibk_backend->add)
+		return xen_pcibk_backend->add(pdev, dev, devid, publish_cb);
+	return -1;
+}
+
+static inline void xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
+					     struct pci_dev *dev, bool lock)
+{
+	if (xen_pcibk_backend && xen_pcibk_backend->release)
+		return xen_pcibk_backend->release(pdev, dev, lock);
+}
+
+static inline struct pci_dev *
+xen_pcibk_get_pci_dev(struct xen_pcibk_device *pdev, unsigned int domain,
+		      unsigned int bus, unsigned int devfn)
+{
+	if (xen_pcibk_backend && xen_pcibk_backend->get)
+		return xen_pcibk_backend->get(pdev, domain, bus, devfn);
+	return NULL;
+}
+
+/**
+* Add for domain0 PCIE-AER handling. Get guest domain/bus/devfn in xen_pcibk
+* before sending aer request to pcifront, so that guest could identify
+* device, coopearte with xen_pcibk to finish aer recovery job if device driver
+* has the capability
+*/
+static inline int xen_pcibk_get_pcifront_dev(struct pci_dev *pcidev,
+					     struct xen_pcibk_device *pdev,
+					     unsigned int *domain,
+					     unsigned int *bus,
+					     unsigned int *devfn)
+{
+	if (xen_pcibk_backend && xen_pcibk_backend->find)
+		return xen_pcibk_backend->find(pcidev, pdev, domain, bus,
+					       devfn);
+	return -1;
+}
+
+static inline int xen_pcibk_init_devices(struct xen_pcibk_device *pdev)
+{
+	if (xen_pcibk_backend && xen_pcibk_backend->init)
+		return xen_pcibk_backend->init(pdev);
+	return -1;
+}
+
+static inline int xen_pcibk_publish_pci_roots(struct xen_pcibk_device *pdev,
+					      publish_pci_root_cb cb)
+{
+	if (xen_pcibk_backend && xen_pcibk_backend->publish)
+		return xen_pcibk_backend->publish(pdev, cb);
+	return -1;
+}
+
+static inline void xen_pcibk_release_devices(struct xen_pcibk_device *pdev)
+{
+	if (xen_pcibk_backend && xen_pcibk_backend->free)
+		return xen_pcibk_backend->free(pdev);
+}
+
+/* Handles events from front-end */
+irqreturn_t xen_pcibk_handle_event(int irq, void *dev_id);
+void xen_pcibk_do_op(struct work_struct *data);
+
+static inline void xen_pcibk_lateeoi(struct xen_pcibk_device *pdev,
+				     unsigned int eoi_flag)
+{
+	if (test_and_clear_bit(_EOI_pending, &pdev->flags))
+		xen_irq_lateeoi(pdev->evtchn_irq, eoi_flag);
+}
+
+int xen_pcibk_xenbus_register(void);
+void xen_pcibk_xenbus_unregister(void);
+#endif
diff --git a/drivers/xen/xen-pciback/pciback_ops.c b/drivers/xen/xen-pciback/pciback_ops.c
new file mode 100644
index 000000000..bfc186bf0
--- /dev/null
+++ b/drivers/xen/xen-pciback/pciback_ops.c
@@ -0,0 +1,443 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PCI Backend Operations - respond to PCI requests from Frontend
+ *
+ *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#define dev_fmt pr_fmt
+
+#include <linux/moduleparam.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <xen/events.h>
+#include <linux/sched.h>
+#include "pciback.h"
+
+static irqreturn_t xen_pcibk_guest_interrupt(int irq, void *dev_id);
+
+/* Ensure a device is has the fake IRQ handler "turned on/off" and is
+ * ready to be exported. This MUST be run after xen_pcibk_reset_device
+ * which does the actual PCI device enable/disable.
+ */
+static void xen_pcibk_control_isr(struct pci_dev *dev, int reset)
+{
+	struct xen_pcibk_dev_data *dev_data;
+	int rc;
+	int enable = 0;
+
+	dev_data = pci_get_drvdata(dev);
+	if (!dev_data)
+		return;
+
+	/* We don't deal with bridges */
+	if (dev->hdr_type != PCI_HEADER_TYPE_NORMAL)
+		return;
+
+	if (reset) {
+		dev_data->enable_intx = 0;
+		dev_data->ack_intr = 0;
+	}
+	enable =  dev_data->enable_intx;
+
+	/* Asked to disable, but ISR isn't runnig */
+	if (!enable && !dev_data->isr_on)
+		return;
+
+	/* Squirrel away the IRQs in the dev_data. We need this
+	 * b/c when device transitions to MSI, the dev->irq is
+	 * overwritten with the MSI vector.
+	 */
+	if (enable)
+		dev_data->irq = dev->irq;
+
+	/*
+	 * SR-IOV devices in all use MSI-X and have no legacy
+	 * interrupts, so inhibit creating a fake IRQ handler for them.
+	 */
+	if (dev_data->irq == 0)
+		goto out;
+
+	dev_dbg(&dev->dev, "%s: #%d %s %s%s %s-> %s\n",
+		dev_data->irq_name,
+		dev_data->irq,
+		pci_is_enabled(dev) ? "on" : "off",
+		dev->msi_enabled ? "MSI" : "",
+		dev->msix_enabled ? "MSI/X" : "",
+		dev_data->isr_on ? "enable" : "disable",
+		enable ? "enable" : "disable");
+
+	if (enable) {
+		/*
+		 * The MSI or MSI-X should not have an IRQ handler. Otherwise
+		 * if the guest terminates we BUG_ON in free_msi_irqs.
+		 */
+		if (dev->msi_enabled || dev->msix_enabled)
+			goto out;
+
+		rc = request_irq(dev_data->irq,
+				xen_pcibk_guest_interrupt, IRQF_SHARED,
+				dev_data->irq_name, dev);
+		if (rc) {
+			dev_err(&dev->dev, "%s: failed to install fake IRQ " \
+				"handler for IRQ %d! (rc:%d)\n",
+				dev_data->irq_name, dev_data->irq, rc);
+			goto out;
+		}
+	} else {
+		free_irq(dev_data->irq, dev);
+		dev_data->irq = 0;
+	}
+	dev_data->isr_on = enable;
+	dev_data->ack_intr = enable;
+out:
+	dev_dbg(&dev->dev, "%s: #%d %s %s%s %s\n",
+		dev_data->irq_name,
+		dev_data->irq,
+		pci_is_enabled(dev) ? "on" : "off",
+		dev->msi_enabled ? "MSI" : "",
+		dev->msix_enabled ? "MSI/X" : "",
+		enable ? (dev_data->isr_on ? "enabled" : "failed to enable") :
+			(dev_data->isr_on ? "failed to disable" : "disabled"));
+}
+
+/* Ensure a device is "turned off" and ready to be exported.
+ * (Also see xen_pcibk_config_reset to ensure virtual configuration space is
+ * ready to be re-exported)
+ */
+void xen_pcibk_reset_device(struct pci_dev *dev)
+{
+	u16 cmd;
+
+	xen_pcibk_control_isr(dev, 1 /* reset device */);
+
+	/* Disable devices (but not bridges) */
+	if (dev->hdr_type == PCI_HEADER_TYPE_NORMAL) {
+#ifdef CONFIG_PCI_MSI
+		/* The guest could have been abruptly killed without
+		 * disabling MSI/MSI-X interrupts.*/
+		if (dev->msix_enabled)
+			pci_disable_msix(dev);
+		if (dev->msi_enabled)
+			pci_disable_msi(dev);
+#endif
+		if (pci_is_enabled(dev))
+			pci_disable_device(dev);
+
+		dev->is_busmaster = 0;
+	} else {
+		pci_read_config_word(dev, PCI_COMMAND, &cmd);
+		if (cmd & (PCI_COMMAND_INVALIDATE)) {
+			cmd &= ~(PCI_COMMAND_INVALIDATE);
+			pci_write_config_word(dev, PCI_COMMAND, cmd);
+
+			dev->is_busmaster = 0;
+		}
+	}
+}
+
+#ifdef CONFIG_PCI_MSI
+static
+int xen_pcibk_enable_msi(struct xen_pcibk_device *pdev,
+			 struct pci_dev *dev, struct xen_pci_op *op)
+{
+	struct xen_pcibk_dev_data *dev_data;
+	int status;
+
+	if (dev->msi_enabled)
+		status = -EALREADY;
+	else if (dev->msix_enabled)
+		status = -ENXIO;
+	else
+		status = pci_enable_msi(dev);
+
+	if (status) {
+		dev_warn_ratelimited(&dev->dev, "error enabling MSI for guest %u: err %d\n",
+				     pdev->xdev->otherend_id, status);
+		op->value = 0;
+		return XEN_PCI_ERR_op_failed;
+	}
+
+	/* The value the guest needs is actually the IDT vector, not
+	 * the local domain's IRQ number. */
+
+	op->value = dev->irq ? xen_pirq_from_irq(dev->irq) : 0;
+
+	dev_dbg(&dev->dev, "MSI: %d\n", op->value);
+
+	dev_data = pci_get_drvdata(dev);
+	if (dev_data)
+		dev_data->ack_intr = 0;
+
+	return 0;
+}
+
+static
+int xen_pcibk_disable_msi(struct xen_pcibk_device *pdev,
+			  struct pci_dev *dev, struct xen_pci_op *op)
+{
+	if (dev->msi_enabled) {
+		struct xen_pcibk_dev_data *dev_data;
+
+		pci_disable_msi(dev);
+
+		dev_data = pci_get_drvdata(dev);
+		if (dev_data)
+			dev_data->ack_intr = 1;
+	}
+	op->value = dev->irq ? xen_pirq_from_irq(dev->irq) : 0;
+
+	dev_dbg(&dev->dev, "MSI: %d\n", op->value);
+
+	return 0;
+}
+
+static
+int xen_pcibk_enable_msix(struct xen_pcibk_device *pdev,
+			  struct pci_dev *dev, struct xen_pci_op *op)
+{
+	struct xen_pcibk_dev_data *dev_data;
+	int i, result;
+	struct msix_entry *entries;
+	u16 cmd;
+
+	dev_dbg(&dev->dev, "enable MSI-X\n");
+
+	if (op->value > SH_INFO_MAX_VEC)
+		return -EINVAL;
+
+	if (dev->msix_enabled)
+		return -EALREADY;
+
+	/*
+	 * PCI_COMMAND_MEMORY must be enabled, otherwise we may not be able
+	 * to access the BARs where the MSI-X entries reside.
+	 * But VF devices are unique in which the PF needs to be checked.
+	 */
+	pci_read_config_word(pci_physfn(dev), PCI_COMMAND, &cmd);
+	if (dev->msi_enabled || !(cmd & PCI_COMMAND_MEMORY))
+		return -ENXIO;
+
+	entries = kmalloc_objs(*entries, op->value);
+	if (entries == NULL)
+		return -ENOMEM;
+
+	for (i = 0; i < op->value; i++) {
+		entries[i].entry = op->msix_entries[i].entry;
+		entries[i].vector = op->msix_entries[i].vector;
+	}
+
+	result = pci_enable_msix_exact(dev, entries, op->value);
+	if (result == 0) {
+		for (i = 0; i < op->value; i++) {
+			op->msix_entries[i].entry = entries[i].entry;
+			if (entries[i].vector) {
+				op->msix_entries[i].vector =
+					xen_pirq_from_irq(entries[i].vector);
+				dev_dbg(&dev->dev, "MSI-X[%d]: %d\n", i,
+					op->msix_entries[i].vector);
+			}
+		}
+	} else
+		dev_warn_ratelimited(&dev->dev, "error enabling MSI-X for guest %u: err %d!\n",
+				     pdev->xdev->otherend_id, result);
+	kfree(entries);
+
+	op->value = result;
+	dev_data = pci_get_drvdata(dev);
+	if (dev_data)
+		dev_data->ack_intr = 0;
+
+	return result > 0 ? 0 : result;
+}
+
+static
+int xen_pcibk_disable_msix(struct xen_pcibk_device *pdev,
+			   struct pci_dev *dev, struct xen_pci_op *op)
+{
+	if (dev->msix_enabled) {
+		struct xen_pcibk_dev_data *dev_data;
+
+		pci_disable_msix(dev);
+
+		dev_data = pci_get_drvdata(dev);
+		if (dev_data)
+			dev_data->ack_intr = 1;
+	}
+	/*
+	 * SR-IOV devices (which don't have any legacy IRQ) have
+	 * an undefined IRQ value of zero.
+	 */
+	op->value = dev->irq ? xen_pirq_from_irq(dev->irq) : 0;
+
+	dev_dbg(&dev->dev, "MSI-X: %d\n", op->value);
+
+	return 0;
+}
+#endif
+
+static inline bool xen_pcibk_test_op_pending(struct xen_pcibk_device *pdev)
+{
+	return test_bit(_XEN_PCIF_active,
+			(unsigned long *)&pdev->sh_info->flags) &&
+	       !test_and_set_bit(_PDEVF_op_active, &pdev->flags);
+}
+
+/*
+* Now the same evtchn is used for both pcifront conf_read_write request
+* as well as pcie aer front end ack. We use a new work_queue to schedule
+* xen_pcibk conf_read_write service for avoiding confict with aer_core
+* do_recovery job which also use the system default work_queue
+*/
+static void xen_pcibk_test_and_schedule_op(struct xen_pcibk_device *pdev)
+{
+	bool eoi = true;
+
+	/* Check that frontend is requesting an operation and that we are not
+	 * already processing a request */
+	if (xen_pcibk_test_op_pending(pdev)) {
+		schedule_work(&pdev->op_work);
+		eoi = false;
+	}
+	/*_XEN_PCIB_active should have been cleared by pcifront. And also make
+	sure xen_pcibk is waiting for ack by checking _PCIB_op_pending*/
+	if (!test_bit(_XEN_PCIB_active, (unsigned long *)&pdev->sh_info->flags)
+	    && test_bit(_PCIB_op_pending, &pdev->flags)) {
+		wake_up(&xen_pcibk_aer_wait_queue);
+		eoi = false;
+	}
+
+	/* EOI if there was nothing to do. */
+	if (eoi)
+		xen_pcibk_lateeoi(pdev, XEN_EOI_FLAG_SPURIOUS);
+}
+
+/* Performing the configuration space reads/writes must not be done in atomic
+ * context because some of the pci_* functions can sleep (mostly due to ACPI
+ * use of semaphores). This function is intended to be called from a work
+ * queue in process context taking a struct xen_pcibk_device as a parameter */
+
+static void xen_pcibk_do_one_op(struct xen_pcibk_device *pdev)
+{
+	struct pci_dev *dev;
+	struct xen_pcibk_dev_data *dev_data = NULL;
+	struct xen_pci_op *op = &pdev->op;
+	int test_intx = 0;
+#ifdef CONFIG_PCI_MSI
+	unsigned int nr = 0;
+#endif
+
+	*op = pdev->sh_info->op;
+	barrier();
+	dev = xen_pcibk_get_pci_dev(pdev, op->domain, op->bus, op->devfn);
+
+	if (dev == NULL)
+		op->err = XEN_PCI_ERR_dev_not_found;
+	else {
+		dev_data = pci_get_drvdata(dev);
+		if (dev_data)
+			test_intx = dev_data->enable_intx;
+		switch (op->cmd) {
+		case XEN_PCI_OP_conf_read:
+			op->err = xen_pcibk_config_read(dev,
+				  op->offset, op->size, &op->value);
+			break;
+		case XEN_PCI_OP_conf_write:
+			op->err = xen_pcibk_config_write(dev,
+				  op->offset, op->size,	op->value);
+			break;
+#ifdef CONFIG_PCI_MSI
+		case XEN_PCI_OP_enable_msi:
+			op->err = xen_pcibk_enable_msi(pdev, dev, op);
+			break;
+		case XEN_PCI_OP_disable_msi:
+			op->err = xen_pcibk_disable_msi(pdev, dev, op);
+			break;
+		case XEN_PCI_OP_enable_msix:
+			nr = op->value;
+			op->err = xen_pcibk_enable_msix(pdev, dev, op);
+			break;
+		case XEN_PCI_OP_disable_msix:
+			op->err = xen_pcibk_disable_msix(pdev, dev, op);
+			break;
+#endif
+		default:
+			op->err = XEN_PCI_ERR_not_implemented;
+			break;
+		}
+	}
+	if (!op->err && dev && dev_data) {
+		/* Transition detected */
+		if ((dev_data->enable_intx != test_intx))
+			xen_pcibk_control_isr(dev, 0 /* no reset */);
+	}
+	pdev->sh_info->op.err = op->err;
+	pdev->sh_info->op.value = op->value;
+#ifdef CONFIG_PCI_MSI
+	if (op->cmd == XEN_PCI_OP_enable_msix && op->err == 0) {
+		unsigned int i;
+
+		for (i = 0; i < nr; i++)
+			pdev->sh_info->op.msix_entries[i].vector =
+				op->msix_entries[i].vector;
+	}
+#endif
+	/* Tell the driver domain that we're done. */
+	wmb();
+	clear_bit(_XEN_PCIF_active, (unsigned long *)&pdev->sh_info->flags);
+	notify_remote_via_irq(pdev->evtchn_irq);
+
+	/* Mark that we're done. */
+	smp_mb__before_atomic(); /* /after/ clearing PCIF_active */
+	clear_bit(_PDEVF_op_active, &pdev->flags);
+	smp_mb__after_atomic(); /* /before/ final check for work */
+}
+
+void xen_pcibk_do_op(struct work_struct *data)
+{
+	struct xen_pcibk_device *pdev =
+		container_of(data, struct xen_pcibk_device, op_work);
+
+	do {
+		xen_pcibk_do_one_op(pdev);
+	} while (xen_pcibk_test_op_pending(pdev));
+
+	xen_pcibk_lateeoi(pdev, 0);
+}
+
+irqreturn_t xen_pcibk_handle_event(int irq, void *dev_id)
+{
+	struct xen_pcibk_device *pdev = dev_id;
+	bool eoi;
+
+	/* IRQs might come in before pdev->evtchn_irq is written. */
+	if (unlikely(pdev->evtchn_irq != irq))
+		pdev->evtchn_irq = irq;
+
+	eoi = test_and_set_bit(_EOI_pending, &pdev->flags);
+	WARN(eoi, "IRQ while EOI pending\n");
+
+	xen_pcibk_test_and_schedule_op(pdev);
+
+	return IRQ_HANDLED;
+}
+static irqreturn_t xen_pcibk_guest_interrupt(int irq, void *dev_id)
+{
+	struct pci_dev *dev = (struct pci_dev *)dev_id;
+	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
+
+	if (dev_data->isr_on && dev_data->ack_intr) {
+		dev_data->handled++;
+		if ((dev_data->handled % 1000) == 0) {
+			if (xen_test_irq_shared(irq)) {
+				dev_info(&dev->dev, "%s IRQ line is not shared "
+					"with other domains. Turning ISR off\n",
+					 dev_data->irq_name);
+				dev_data->ack_intr = 0;
+			}
+		}
+		return IRQ_HANDLED;
+	}
+	return IRQ_NONE;
+}
diff --git a/drivers/xen/xen-pciback/vpci.c b/drivers/xen/xen-pciback/vpci.c
new file mode 100644
index 000000000..df292c19e
--- /dev/null
+++ b/drivers/xen/xen-pciback/vpci.c
@@ -0,0 +1,268 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PCI Backend - Provides a Virtual PCI bus (with real devices)
+ *               to the frontend
+ *
+ *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#define dev_fmt pr_fmt
+
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/pci.h>
+#include <linux/mutex.h>
+#include "pciback.h"
+
+#define PCI_SLOT_MAX 32
+
+struct vpci_dev_data {
+	/* Access to dev_list must be protected by lock */
+	struct list_head dev_list[PCI_SLOT_MAX];
+	struct mutex lock;
+};
+
+static inline struct list_head *list_first(struct list_head *head)
+{
+	return head->next;
+}
+
+static struct pci_dev *__xen_pcibk_get_pci_dev(struct xen_pcibk_device *pdev,
+					       unsigned int domain,
+					       unsigned int bus,
+					       unsigned int devfn)
+{
+	struct pci_dev_entry *entry;
+	struct pci_dev *dev = NULL;
+	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
+
+	if (domain != 0 || bus != 0)
+		return NULL;
+
+	if (PCI_SLOT(devfn) < PCI_SLOT_MAX) {
+		mutex_lock(&vpci_dev->lock);
+
+		list_for_each_entry(entry,
+				    &vpci_dev->dev_list[PCI_SLOT(devfn)],
+				    list) {
+			if (PCI_FUNC(entry->dev->devfn) == PCI_FUNC(devfn)) {
+				dev = entry->dev;
+				break;
+			}
+		}
+
+		mutex_unlock(&vpci_dev->lock);
+	}
+	return dev;
+}
+
+static inline int match_slot(struct pci_dev *l, struct pci_dev *r)
+{
+	if (pci_domain_nr(l->bus) == pci_domain_nr(r->bus)
+	    && l->bus == r->bus && PCI_SLOT(l->devfn) == PCI_SLOT(r->devfn))
+		return 1;
+
+	return 0;
+}
+
+static int __xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev,
+				   struct pci_dev *dev, int devid,
+				   publish_pci_dev_cb publish_cb)
+{
+	int err = 0, slot, func = PCI_FUNC(dev->devfn);
+	struct pci_dev_entry *t, *dev_entry;
+	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
+
+	if ((dev->class >> 24) == PCI_BASE_CLASS_BRIDGE) {
+		err = -EFAULT;
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Can't export bridges on the virtual PCI bus");
+		goto out;
+	}
+
+	dev_entry = kmalloc_obj(*dev_entry);
+	if (!dev_entry) {
+		err = -ENOMEM;
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error adding entry to virtual PCI bus");
+		goto out;
+	}
+
+	dev_entry->dev = dev;
+
+	mutex_lock(&vpci_dev->lock);
+
+	/*
+	 * Keep multi-function devices together on the virtual PCI bus, except
+	 * that we want to keep virtual functions at func 0 on their own. They
+	 * aren't multi-function devices and hence their presence at func 0
+	 * may cause guests to not scan the other functions.
+	 */
+	if (!dev->is_virtfn || func) {
+		for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
+			if (list_empty(&vpci_dev->dev_list[slot]))
+				continue;
+
+			t = list_entry(list_first(&vpci_dev->dev_list[slot]),
+				       struct pci_dev_entry, list);
+			if (t->dev->is_virtfn && !PCI_FUNC(t->dev->devfn))
+				continue;
+
+			if (match_slot(dev, t->dev)) {
+				dev_info(&dev->dev, "vpci: assign to virtual slot %d func %d\n",
+					 slot, func);
+				list_add_tail(&dev_entry->list,
+					      &vpci_dev->dev_list[slot]);
+				goto unlock;
+			}
+		}
+	}
+
+	/* Assign to a new slot on the virtual PCI bus */
+	for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
+		if (list_empty(&vpci_dev->dev_list[slot])) {
+			dev_info(&dev->dev, "vpci: assign to virtual slot %d\n",
+				 slot);
+			list_add_tail(&dev_entry->list,
+				      &vpci_dev->dev_list[slot]);
+			goto unlock;
+		}
+	}
+
+	err = -ENOMEM;
+	xenbus_dev_fatal(pdev->xdev, err,
+			 "No more space on root virtual PCI bus");
+
+unlock:
+	mutex_unlock(&vpci_dev->lock);
+
+	/* Publish this device. */
+	if (!err)
+		err = publish_cb(pdev, 0, 0, PCI_DEVFN(slot, func), devid);
+	else
+		kfree(dev_entry);
+
+out:
+	return err;
+}
+
+static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
+					struct pci_dev *dev, bool lock)
+{
+	int slot;
+	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
+	struct pci_dev *found_dev = NULL;
+
+	mutex_lock(&vpci_dev->lock);
+
+	for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
+		struct pci_dev_entry *e;
+
+		list_for_each_entry(e, &vpci_dev->dev_list[slot], list) {
+			if (e->dev == dev) {
+				list_del(&e->list);
+				found_dev = e->dev;
+				kfree(e);
+				goto out;
+			}
+		}
+	}
+
+out:
+	mutex_unlock(&vpci_dev->lock);
+
+	if (found_dev) {
+		if (lock)
+			device_lock(&found_dev->dev);
+		pcistub_put_pci_dev(found_dev);
+		if (lock)
+			device_unlock(&found_dev->dev);
+	}
+}
+
+static int __xen_pcibk_init_devices(struct xen_pcibk_device *pdev)
+{
+	int slot;
+	struct vpci_dev_data *vpci_dev;
+
+	vpci_dev = kmalloc_obj(*vpci_dev);
+	if (!vpci_dev)
+		return -ENOMEM;
+
+	mutex_init(&vpci_dev->lock);
+
+	for (slot = 0; slot < PCI_SLOT_MAX; slot++)
+		INIT_LIST_HEAD(&vpci_dev->dev_list[slot]);
+
+	pdev->pci_dev_data = vpci_dev;
+
+	return 0;
+}
+
+static int __xen_pcibk_publish_pci_roots(struct xen_pcibk_device *pdev,
+					 publish_pci_root_cb publish_cb)
+{
+	/* The Virtual PCI bus has only one root */
+	return publish_cb(pdev, 0, 0);
+}
+
+static void __xen_pcibk_release_devices(struct xen_pcibk_device *pdev)
+{
+	int slot;
+	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
+
+	for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
+		struct pci_dev_entry *e, *tmp;
+		list_for_each_entry_safe(e, tmp, &vpci_dev->dev_list[slot],
+					 list) {
+			struct pci_dev *dev = e->dev;
+			list_del(&e->list);
+			device_lock(&dev->dev);
+			pcistub_put_pci_dev(dev);
+			device_unlock(&dev->dev);
+			kfree(e);
+		}
+	}
+
+	kfree(vpci_dev);
+	pdev->pci_dev_data = NULL;
+}
+
+static int __xen_pcibk_get_pcifront_dev(struct pci_dev *pcidev,
+					struct xen_pcibk_device *pdev,
+					unsigned int *domain, unsigned int *bus,
+					unsigned int *devfn)
+{
+	struct pci_dev_entry *entry;
+	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
+	int found = 0, slot;
+
+	mutex_lock(&vpci_dev->lock);
+	for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
+		list_for_each_entry(entry,
+			    &vpci_dev->dev_list[slot],
+			    list) {
+			if (entry->dev == pcidev) {
+				found = 1;
+				*domain = 0;
+				*bus = 0;
+				*devfn = PCI_DEVFN(slot,
+					 PCI_FUNC(pcidev->devfn));
+			}
+		}
+	}
+	mutex_unlock(&vpci_dev->lock);
+	return found;
+}
+
+const struct xen_pcibk_backend xen_pcibk_vpci_backend = {
+	.name		= "vpci",
+	.init		= __xen_pcibk_init_devices,
+	.free		= __xen_pcibk_release_devices,
+	.find		= __xen_pcibk_get_pcifront_dev,
+	.publish	= __xen_pcibk_publish_pci_roots,
+	.release	= __xen_pcibk_release_pci_dev,
+	.add		= __xen_pcibk_add_pci_dev,
+	.get		= __xen_pcibk_get_pci_dev,
+};
diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
new file mode 100644
index 000000000..b34785ba7
--- /dev/null
+++ b/drivers/xen/xen-pciback/xenbus.c
@@ -0,0 +1,758 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PCI Backend Xenbus Setup - handles setup with frontend and xend
+ *
+ *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/moduleparam.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/vmalloc.h>
+#include <linux/workqueue.h>
+#include <xen/xenbus.h>
+#include <xen/events.h>
+#include <xen/pci.h>
+#include "pciback.h"
+
+#define INVALID_EVTCHN_IRQ  (-1)
+
+static bool __read_mostly passthrough;
+module_param(passthrough, bool, S_IRUGO);
+MODULE_PARM_DESC(passthrough,
+	"Option to specify how to export PCI topology to guest:\n"\
+	" 0 - (default) Hide the true PCI topology and makes the frontend\n"\
+	"   there is a single PCI bus with only the exported devices on it.\n"\
+	"   For example, a device at 03:05.0 will be re-assigned to 00:00.0\n"\
+	"   while second device at 02:1a.1 will be re-assigned to 00:01.1.\n"\
+	" 1 - Passthrough provides a real view of the PCI topology to the\n"\
+	"   frontend (for example, a device at 06:01.b will still appear at\n"\
+	"   06:01.b to the frontend). This is similar to how Xen 2.0.x\n"\
+	"   exposed PCI devices to its driver domains. This may be required\n"\
+	"   for drivers which depend on finding their hardware in certain\n"\
+	"   bus/slot locations.");
+
+static struct xen_pcibk_device *alloc_pdev(struct xenbus_device *xdev)
+{
+	struct xen_pcibk_device *pdev;
+
+	pdev = kzalloc_obj(struct xen_pcibk_device);
+	if (pdev == NULL)
+		goto out;
+	dev_dbg(&xdev->dev, "allocated pdev @ 0x%p\n", pdev);
+
+	pdev->xdev = xdev;
+
+	mutex_init(&pdev->dev_lock);
+
+	pdev->sh_info = NULL;
+	pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
+	pdev->be_watching = 0;
+
+	INIT_WORK(&pdev->op_work, xen_pcibk_do_op);
+
+	if (xen_pcibk_init_devices(pdev)) {
+		kfree(pdev);
+		pdev = NULL;
+	}
+
+	dev_set_drvdata(&xdev->dev, pdev);
+
+out:
+	return pdev;
+}
+
+static void xen_pcibk_disconnect(struct xen_pcibk_device *pdev)
+{
+	mutex_lock(&pdev->dev_lock);
+	/* Ensure the guest can't trigger our handler before removing devices */
+	if (pdev->evtchn_irq != INVALID_EVTCHN_IRQ) {
+		unbind_from_irqhandler(pdev->evtchn_irq, pdev);
+		pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
+	}
+
+	/* If the driver domain started an op, make sure we complete it
+	 * before releasing the shared memory */
+
+	flush_work(&pdev->op_work);
+
+	if (pdev->sh_info != NULL) {
+		xenbus_unmap_ring_vfree(pdev->xdev, pdev->sh_info);
+		pdev->sh_info = NULL;
+	}
+	mutex_unlock(&pdev->dev_lock);
+}
+
+static void free_pdev(struct xen_pcibk_device *pdev)
+{
+	if (pdev->be_watching) {
+		unregister_xenbus_watch(&pdev->be_watch);
+		pdev->be_watching = 0;
+	}
+
+	xen_pcibk_disconnect(pdev);
+
+	/* N.B. This calls pcistub_put_pci_dev which does the FLR on all
+	 * of the PCIe devices. */
+	xen_pcibk_release_devices(pdev);
+
+	dev_set_drvdata(&pdev->xdev->dev, NULL);
+	pdev->xdev = NULL;
+
+	kfree(pdev);
+}
+
+static int xen_pcibk_do_attach(struct xen_pcibk_device *pdev, int gnt_ref,
+			     evtchn_port_t remote_evtchn)
+{
+	int err = 0;
+	void *vaddr;
+
+	dev_dbg(&pdev->xdev->dev,
+		"Attaching to frontend resources - gnt_ref=%d evtchn=%u\n",
+		gnt_ref, remote_evtchn);
+
+	err = xenbus_map_ring_valloc(pdev->xdev, &gnt_ref, 1, &vaddr);
+	if (err < 0) {
+		xenbus_dev_fatal(pdev->xdev, err,
+				"Error mapping other domain page in ours.");
+		goto out;
+	}
+
+	pdev->sh_info = vaddr;
+
+	err = bind_interdomain_evtchn_to_irqhandler_lateeoi(
+		pdev->xdev, remote_evtchn, xen_pcibk_handle_event,
+		0, DRV_NAME, pdev);
+	if (err < 0) {
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error binding event channel to IRQ");
+		goto out;
+	}
+	pdev->evtchn_irq = err;
+	err = 0;
+
+	dev_dbg(&pdev->xdev->dev, "Attached!\n");
+out:
+	return err;
+}
+
+static int xen_pcibk_attach(struct xen_pcibk_device *pdev)
+{
+	int err = 0;
+	int gnt_ref;
+	evtchn_port_t remote_evtchn;
+	char *magic = NULL;
+
+
+	mutex_lock(&pdev->dev_lock);
+	/* Make sure we only do this setup once */
+	if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) !=
+	    XenbusStateInitialised)
+		goto out;
+
+	/* Wait for frontend to state that it has published the configuration */
+	if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->otherend) !=
+	    XenbusStateInitialised)
+		goto out;
+
+	dev_dbg(&pdev->xdev->dev, "Reading frontend config\n");
+
+	err = xenbus_gather(XBT_NIL, pdev->xdev->otherend,
+			    "pci-op-ref", "%u", &gnt_ref,
+			    "event-channel", "%u", &remote_evtchn,
+			    "magic", NULL, &magic, NULL);
+	if (err) {
+		/* If configuration didn't get read correctly, wait longer */
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error reading configuration from frontend");
+		goto out;
+	}
+
+	if (magic == NULL || strcmp(magic, XEN_PCI_MAGIC) != 0) {
+		xenbus_dev_fatal(pdev->xdev, -EFAULT,
+				 "version mismatch (%s/%s) with pcifront - "
+				 "halting " DRV_NAME,
+				 magic, XEN_PCI_MAGIC);
+		err = -EFAULT;
+		goto out;
+	}
+
+	err = xen_pcibk_do_attach(pdev, gnt_ref, remote_evtchn);
+	if (err)
+		goto out;
+
+	dev_dbg(&pdev->xdev->dev, "Connecting...\n");
+
+	err = xenbus_switch_state(pdev->xdev, XenbusStateConnected);
+	if (err)
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error switching to connected state!");
+
+	dev_dbg(&pdev->xdev->dev, "Connected? %d\n", err);
+out:
+	mutex_unlock(&pdev->dev_lock);
+
+	kfree(magic);
+
+	return err;
+}
+
+static int xen_pcibk_publish_pci_dev(struct xen_pcibk_device *pdev,
+				   unsigned int domain, unsigned int bus,
+				   unsigned int devfn, unsigned int devid)
+{
+	int err;
+	int len;
+	char str[64];
+
+	len = snprintf(str, sizeof(str), "vdev-%d", devid);
+	if (unlikely(len >= (sizeof(str) - 1))) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	/* Note: The PV protocol uses %02x, don't change it */
+	err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, str,
+			    "%04x:%02x:%02x.%02x", domain, bus,
+			    PCI_SLOT(devfn), PCI_FUNC(devfn));
+
+out:
+	return err;
+}
+
+static int xen_pcibk_export_device(struct xen_pcibk_device *pdev,
+				 int domain, int bus, int slot, int func,
+				 int devid)
+{
+	struct pci_dev *dev;
+	int err = 0;
+
+	dev_dbg(&pdev->xdev->dev, "exporting dom %x bus %x slot %x func %x\n",
+		domain, bus, slot, func);
+
+	dev = pcistub_get_pci_dev_by_slot(pdev, domain, bus, slot, func);
+	if (!dev) {
+		err = -EINVAL;
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Couldn't locate PCI device "
+				 "(%04x:%02x:%02x.%d)! "
+				 "perhaps already in-use?",
+				 domain, bus, slot, func);
+		goto out;
+	}
+
+	err = xen_pcibk_add_pci_dev(pdev, dev, devid,
+				    xen_pcibk_publish_pci_dev);
+	if (err)
+		goto out;
+
+	dev_info(&dev->dev, "registering for %d\n", pdev->xdev->otherend_id);
+	if (xen_register_device_domain_owner(dev,
+					     pdev->xdev->otherend_id) != 0) {
+		dev_err(&dev->dev, "Stealing ownership from dom%d.\n",
+			xen_find_device_domain_owner(dev));
+		xen_unregister_device_domain_owner(dev);
+		xen_register_device_domain_owner(dev, pdev->xdev->otherend_id);
+	}
+
+	/* TODO: It'd be nice to export a bridge and have all of its children
+	 * get exported with it. This may be best done in xend (which will
+	 * have to calculate resource usage anyway) but we probably want to
+	 * put something in here to ensure that if a bridge gets given to a
+	 * driver domain, that all devices under that bridge are not given
+	 * to other driver domains (as he who controls the bridge can disable
+	 * it and stop the other devices from working).
+	 */
+out:
+	return err;
+}
+
+static int xen_pcibk_remove_device(struct xen_pcibk_device *pdev,
+				 int domain, int bus, int slot, int func)
+{
+	int err = 0;
+	struct pci_dev *dev;
+
+	dev_dbg(&pdev->xdev->dev, "removing dom %x bus %x slot %x func %x\n",
+		domain, bus, slot, func);
+
+	dev = xen_pcibk_get_pci_dev(pdev, domain, bus, PCI_DEVFN(slot, func));
+	if (!dev) {
+		err = -EINVAL;
+		dev_dbg(&pdev->xdev->dev, "Couldn't locate PCI device "
+			"(%04x:%02x:%02x.%d)! not owned by this domain\n",
+			domain, bus, slot, func);
+		goto out;
+	}
+
+	dev_dbg(&dev->dev, "unregistering for %d\n", pdev->xdev->otherend_id);
+	xen_unregister_device_domain_owner(dev);
+
+	/* N.B. This ends up calling pcistub_put_pci_dev which ends up
+	 * doing the FLR. */
+	xen_pcibk_release_pci_dev(pdev, dev, true /* use the lock. */);
+
+out:
+	return err;
+}
+
+static int xen_pcibk_publish_pci_root(struct xen_pcibk_device *pdev,
+				    unsigned int domain, unsigned int bus)
+{
+	unsigned int d, b;
+	int i, root_num, len, err;
+	char str[64];
+
+	dev_dbg(&pdev->xdev->dev, "Publishing pci roots\n");
+
+	err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
+			   "root_num", "%d", &root_num);
+	if (err == 0 || err == -ENOENT)
+		root_num = 0;
+	else if (err < 0)
+		goto out;
+
+	/* Verify that we haven't already published this pci root */
+	for (i = 0; i < root_num; i++) {
+		len = snprintf(str, sizeof(str), "root-%d", i);
+		if (unlikely(len >= (sizeof(str) - 1))) {
+			err = -ENOMEM;
+			goto out;
+		}
+
+		err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
+				   str, "%x:%x", &d, &b);
+		if (err < 0)
+			goto out;
+		if (err != 2) {
+			err = -EINVAL;
+			goto out;
+		}
+
+		if (d == domain && b == bus) {
+			err = 0;
+			goto out;
+		}
+	}
+
+	len = snprintf(str, sizeof(str), "root-%d", root_num);
+	if (unlikely(len >= (sizeof(str) - 1))) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	dev_dbg(&pdev->xdev->dev, "writing root %d at %04x:%02x\n",
+		root_num, domain, bus);
+
+	err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, str,
+			    "%04x:%02x", domain, bus);
+	if (err)
+		goto out;
+
+	err = xenbus_printf(XBT_NIL, pdev->xdev->nodename,
+			    "root_num", "%d", (root_num + 1));
+
+out:
+	return err;
+}
+
+static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev,
+				 enum xenbus_state state)
+{
+	int err = 0;
+	int num_devs;
+	int domain, bus, slot, func;
+	unsigned int substate;
+	int i, len;
+	char state_str[64];
+	char dev_str[64];
+
+
+	dev_dbg(&pdev->xdev->dev, "Reconfiguring device ...\n");
+
+	mutex_lock(&pdev->dev_lock);
+	if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) != state)
+		goto out;
+
+	err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d",
+			   &num_devs);
+	if (err != 1) {
+		if (err >= 0)
+			err = -EINVAL;
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error reading number of devices");
+		goto out;
+	}
+
+	for (i = 0; i < num_devs; i++) {
+		len = snprintf(state_str, sizeof(state_str), "state-%d", i);
+		if (unlikely(len >= (sizeof(state_str) - 1))) {
+			err = -ENOMEM;
+			xenbus_dev_fatal(pdev->xdev, err,
+					 "String overflow while reading "
+					 "configuration");
+			goto out;
+		}
+		substate = xenbus_read_unsigned(pdev->xdev->nodename, state_str,
+						XenbusStateUnknown);
+
+		switch (substate) {
+		case XenbusStateInitialising:
+			dev_dbg(&pdev->xdev->dev, "Attaching dev-%d ...\n", i);
+
+			len = snprintf(dev_str, sizeof(dev_str), "dev-%d", i);
+			if (unlikely(len >= (sizeof(dev_str) - 1))) {
+				err = -ENOMEM;
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "String overflow while "
+						 "reading configuration");
+				goto out;
+			}
+			err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
+					   dev_str, "%x:%x:%x.%x",
+					   &domain, &bus, &slot, &func);
+			if (err < 0) {
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error reading device "
+						 "configuration");
+				goto out;
+			}
+			if (err != 4) {
+				err = -EINVAL;
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error parsing pci device "
+						 "configuration");
+				goto out;
+			}
+
+			err = xen_pcibk_export_device(pdev, domain, bus, slot,
+						    func, i);
+			if (err)
+				goto out;
+
+			/* Publish pci roots. */
+			err = xen_pcibk_publish_pci_roots(pdev,
+						xen_pcibk_publish_pci_root);
+			if (err) {
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error while publish PCI root"
+						 "buses for frontend");
+				goto out;
+			}
+
+			err = xenbus_printf(XBT_NIL, pdev->xdev->nodename,
+					    state_str, "%d",
+					    XenbusStateInitialised);
+			if (err) {
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error switching substate of "
+						 "dev-%d\n", i);
+				goto out;
+			}
+			break;
+
+		case XenbusStateClosing:
+			dev_dbg(&pdev->xdev->dev, "Detaching dev-%d ...\n", i);
+
+			len = snprintf(dev_str, sizeof(dev_str), "vdev-%d", i);
+			if (unlikely(len >= (sizeof(dev_str) - 1))) {
+				err = -ENOMEM;
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "String overflow while "
+						 "reading configuration");
+				goto out;
+			}
+			err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
+					   dev_str, "%x:%x:%x.%x",
+					   &domain, &bus, &slot, &func);
+			if (err < 0) {
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error reading device "
+						 "configuration");
+				goto out;
+			}
+			if (err != 4) {
+				err = -EINVAL;
+				xenbus_dev_fatal(pdev->xdev, err,
+						 "Error parsing pci device "
+						 "configuration");
+				goto out;
+			}
+
+			err = xen_pcibk_remove_device(pdev, domain, bus, slot,
+						    func);
+			if (err)
+				goto out;
+
+			/* TODO: If at some point we implement support for pci
+			 * root hot-remove on pcifront side, we'll need to
+			 * remove unnecessary xenstore nodes of pci roots here.
+			 */
+
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	if (state != XenbusStateReconfiguring)
+		/* Make sure we only reconfigure once. */
+		goto out;
+
+	err = xenbus_switch_state(pdev->xdev, XenbusStateReconfigured);
+	if (err) {
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error switching to reconfigured state!");
+		goto out;
+	}
+
+out:
+	mutex_unlock(&pdev->dev_lock);
+	return 0;
+}
+
+static void xen_pcibk_frontend_changed(struct xenbus_device *xdev,
+				     enum xenbus_state fe_state)
+{
+	struct xen_pcibk_device *pdev = dev_get_drvdata(&xdev->dev);
+
+	dev_dbg(&xdev->dev, "fe state changed %d\n", fe_state);
+
+	switch (fe_state) {
+	case XenbusStateInitialised:
+		xen_pcibk_attach(pdev);
+		break;
+
+	case XenbusStateReconfiguring:
+		xen_pcibk_reconfigure(pdev, XenbusStateReconfiguring);
+		break;
+
+	case XenbusStateConnected:
+		/* pcifront switched its state from reconfiguring to connected.
+		 * Then switch to connected state.
+		 */
+		xenbus_switch_state(xdev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosing:
+		xen_pcibk_disconnect(pdev);
+		xenbus_switch_state(xdev, XenbusStateClosing);
+		break;
+
+	case XenbusStateClosed:
+		xen_pcibk_disconnect(pdev);
+		xenbus_switch_state(xdev, XenbusStateClosed);
+		if (xenbus_dev_is_online(xdev))
+			break;
+		fallthrough;	/* if not online */
+	case XenbusStateUnknown:
+		dev_dbg(&xdev->dev, "frontend is gone! unregister device\n");
+		device_unregister(&xdev->dev);
+		break;
+
+	default:
+		break;
+	}
+}
+
+static int xen_pcibk_setup_backend(struct xen_pcibk_device *pdev)
+{
+	/* Get configuration from xend (if available now) */
+	int domain, bus, slot, func;
+	int err = 0;
+	int i, num_devs;
+	char dev_str[64];
+	char state_str[64];
+
+	mutex_lock(&pdev->dev_lock);
+	/* It's possible we could get the call to setup twice, so make sure
+	 * we're not already connected.
+	 */
+	if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) !=
+	    XenbusStateInitWait)
+		goto out;
+
+	dev_dbg(&pdev->xdev->dev, "getting be setup\n");
+
+	err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d",
+			   &num_devs);
+	if (err != 1) {
+		if (err >= 0)
+			err = -EINVAL;
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error reading number of devices");
+		goto out;
+	}
+
+	for (i = 0; i < num_devs; i++) {
+		int l = snprintf(dev_str, sizeof(dev_str), "dev-%d", i);
+		if (unlikely(l >= (sizeof(dev_str) - 1))) {
+			err = -ENOMEM;
+			xenbus_dev_fatal(pdev->xdev, err,
+					 "String overflow while reading "
+					 "configuration");
+			goto out;
+		}
+
+		err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, dev_str,
+				   "%x:%x:%x.%x", &domain, &bus, &slot, &func);
+		if (err < 0) {
+			xenbus_dev_fatal(pdev->xdev, err,
+					 "Error reading device configuration");
+			goto out;
+		}
+		if (err != 4) {
+			err = -EINVAL;
+			xenbus_dev_fatal(pdev->xdev, err,
+					 "Error parsing pci device "
+					 "configuration");
+			goto out;
+		}
+
+		err = xen_pcibk_export_device(pdev, domain, bus, slot, func, i);
+		if (err)
+			goto out;
+
+		/* Switch substate of this device. */
+		l = snprintf(state_str, sizeof(state_str), "state-%d", i);
+		if (unlikely(l >= (sizeof(state_str) - 1))) {
+			err = -ENOMEM;
+			xenbus_dev_fatal(pdev->xdev, err,
+					 "String overflow while reading "
+					 "configuration");
+			goto out;
+		}
+		err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, state_str,
+				    "%d", XenbusStateInitialised);
+		if (err) {
+			xenbus_dev_fatal(pdev->xdev, err, "Error switching "
+					 "substate of dev-%d\n", i);
+			goto out;
+		}
+	}
+
+	err = xen_pcibk_publish_pci_roots(pdev, xen_pcibk_publish_pci_root);
+	if (err) {
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error while publish PCI root buses "
+				 "for frontend");
+		goto out;
+	}
+
+	err = xenbus_switch_state(pdev->xdev, XenbusStateInitialised);
+	if (err)
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error switching to initialised state!");
+
+out:
+	mutex_unlock(&pdev->dev_lock);
+	if (!err)
+		/* see if pcifront is already configured (if not, we'll wait) */
+		xen_pcibk_attach(pdev);
+	return err;
+}
+
+static void xen_pcibk_be_watch(struct xenbus_watch *watch,
+			       const char *path, const char *token)
+{
+	struct xen_pcibk_device *pdev =
+	    container_of(watch, struct xen_pcibk_device, be_watch);
+
+	switch (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename)) {
+	case XenbusStateInitWait:
+		xen_pcibk_setup_backend(pdev);
+		break;
+
+	case XenbusStateInitialised:
+		/*
+		 * We typically move to Initialised when the first device was
+		 * added. Hence subsequent devices getting added may need
+		 * reconfiguring.
+		 */
+		xen_pcibk_reconfigure(pdev, XenbusStateInitialised);
+		break;
+
+	default:
+		break;
+	}
+}
+
+static int xen_pcibk_xenbus_probe(struct xenbus_device *dev,
+				const struct xenbus_device_id *id)
+{
+	int err = 0;
+	struct xen_pcibk_device *pdev = alloc_pdev(dev);
+
+	if (pdev == NULL) {
+		err = -ENOMEM;
+		xenbus_dev_fatal(dev, err,
+				 "Error allocating xen_pcibk_device struct");
+		goto out;
+	}
+
+	/* wait for xend to configure us */
+	err = xenbus_switch_state(dev, XenbusStateInitWait);
+	if (err)
+		goto out;
+
+	/* watch the backend node for backend configuration information */
+	err = xenbus_watch_path(dev, dev->nodename, &pdev->be_watch,
+				NULL, xen_pcibk_be_watch);
+	if (err)
+		goto out;
+
+	pdev->be_watching = 1;
+
+	/* We need to force a call to our callback here in case
+	 * xend already configured us!
+	 */
+	xen_pcibk_be_watch(&pdev->be_watch, NULL, NULL);
+
+out:
+	return err;
+}
+
+static void xen_pcibk_xenbus_remove(struct xenbus_device *dev)
+{
+	struct xen_pcibk_device *pdev = dev_get_drvdata(&dev->dev);
+
+	if (pdev != NULL)
+		free_pdev(pdev);
+}
+
+static const struct xenbus_device_id xen_pcibk_ids[] = {
+	{"pci"},
+	{""},
+};
+
+static struct xenbus_driver xen_pcibk_driver = {
+	.name                   = DRV_NAME,
+	.ids                    = xen_pcibk_ids,
+	.probe			= xen_pcibk_xenbus_probe,
+	.remove			= xen_pcibk_xenbus_remove,
+	.otherend_changed	= xen_pcibk_frontend_changed,
+};
+
+const struct xen_pcibk_backend *__read_mostly xen_pcibk_backend;
+
+int __init xen_pcibk_xenbus_register(void)
+{
+	if (!xen_pcibk_pv_support())
+		return 0;
+
+	xen_pcibk_backend = &xen_pcibk_vpci_backend;
+	if (passthrough)
+		xen_pcibk_backend = &xen_pcibk_passthrough_backend;
+	pr_info("backend is %s\n", xen_pcibk_backend->name);
+	return xenbus_register_backend(&xen_pcibk_driver);
+}
+
+void __exit xen_pcibk_xenbus_unregister(void)
+{
+	if (xen_pcibk_pv_support())
+		xenbus_unregister_driver(&xen_pcibk_driver);
+}
diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
new file mode 100644
index 000000000..c7036e0e4
--- /dev/null
+++ b/drivers/xen/xen-scsiback.c
@@ -0,0 +1,1907 @@
+/*
+ * Xen SCSI backend driver
+ *
+ * Copyright (c) 2008, FUJITSU Limited
+ *
+ * Based on the blkback driver code.
+ * Adaption to kernel taget core infrastructure taken from vhost/scsi.c
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) "xen-pvscsi: " fmt
+
+#include <linux/module.h>
+#include <linux/utsname.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
+#include <linux/sched.h>
+#include <linux/list.h>
+#include <linux/gfp.h>
+#include <linux/delay.h>
+#include <linux/spinlock.h>
+#include <linux/configfs.h>
+
+#include <generated/utsrelease.h>
+
+#include <scsi/scsi_host.h> /* SG_ALL */
+
+#include <target/target_core_base.h>
+#include <target/target_core_fabric.h>
+
+#include <asm/hypervisor.h>
+
+#include <xen/xen.h>
+#include <xen/balloon.h>
+#include <xen/events.h>
+#include <xen/xenbus.h>
+#include <xen/grant_table.h>
+#include <xen/page.h>
+
+#include <xen/interface/grant_table.h>
+#include <xen/interface/io/vscsiif.h>
+
+#define VSCSI_VERSION	"v0.1"
+#define VSCSI_NAMELEN	32
+
+struct ids_tuple {
+	unsigned int hst;		/* host    */
+	unsigned int chn;		/* channel */
+	unsigned int tgt;		/* target  */
+	unsigned int lun;		/* LUN     */
+};
+
+struct v2p_entry {
+	struct ids_tuple v;		/* translate from */
+	struct scsiback_tpg *tpg;	/* translate to   */
+	unsigned int lun;
+	struct kref kref;
+	struct list_head l;
+};
+
+struct vscsibk_info {
+	struct xenbus_device *dev;
+
+	domid_t domid;
+	unsigned int irq;
+
+	struct vscsiif_back_ring ring;
+
+	spinlock_t ring_lock;
+	atomic_t nr_unreplied_reqs;
+
+	spinlock_t v2p_lock;
+	struct list_head v2p_entry_lists;
+
+	wait_queue_head_t waiting_to_free;
+
+	struct gnttab_page_cache free_pages;
+};
+
+/* theoretical maximum of grants for one request */
+#define VSCSI_MAX_GRANTS	(SG_ALL + VSCSIIF_SG_TABLESIZE)
+
+/*
+ * VSCSI_GRANT_BATCH is the maximum number of grants to be processed in one
+ * call to map/unmap grants. Don't choose it too large, as there are arrays
+ * with VSCSI_GRANT_BATCH elements allocated on the stack.
+ */
+#define VSCSI_GRANT_BATCH	16
+
+struct vscsibk_pend {
+	uint16_t rqid;
+
+	uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE];
+	uint8_t cmd_len;
+
+	uint8_t sc_data_direction;
+	uint16_t n_sg;		/* real length of SG list */
+	uint16_t n_grants;	/* SG pages and potentially SG list */
+	uint32_t data_len;
+	uint32_t result;
+
+	struct vscsibk_info *info;
+	struct v2p_entry *v2p;
+	struct scatterlist *sgl;
+
+	uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE];
+
+	grant_handle_t grant_handles[VSCSI_MAX_GRANTS];
+	struct page *pages[VSCSI_MAX_GRANTS];
+
+	struct se_cmd se_cmd;
+
+	struct completion tmr_done;
+};
+
+#define VSCSI_DEFAULT_SESSION_TAGS	128
+
+struct scsiback_nexus {
+	/* Pointer to TCM session for I_T Nexus */
+	struct se_session *tvn_se_sess;
+};
+
+struct scsiback_tport {
+	/* SCSI protocol the tport is providing */
+	u8 tport_proto_id;
+	/* Binary World Wide unique Port Name for pvscsi Target port */
+	u64 tport_wwpn;
+	/* ASCII formatted WWPN for pvscsi Target port */
+	char tport_name[VSCSI_NAMELEN];
+	/* Returned by scsiback_make_tport() */
+	struct se_wwn tport_wwn;
+};
+
+struct scsiback_tpg {
+	/* scsiback port target portal group tag for TCM */
+	u16 tport_tpgt;
+	/* track number of TPG Port/Lun Links wrt explicit I_T Nexus shutdown */
+	int tv_tpg_port_count;
+	/* xen-pvscsi references to tpg_nexus, protected by tv_tpg_mutex */
+	int tv_tpg_fe_count;
+	/* list for scsiback_list */
+	struct list_head tv_tpg_list;
+	/* Used to protect access for tpg_nexus */
+	struct mutex tv_tpg_mutex;
+	/* Pointer to the TCM pvscsi I_T Nexus for this TPG endpoint */
+	struct scsiback_nexus *tpg_nexus;
+	/* Pointer back to scsiback_tport */
+	struct scsiback_tport *tport;
+	/* Returned by scsiback_make_tpg() */
+	struct se_portal_group se_tpg;
+	/* alias used in xenstore */
+	char param_alias[VSCSI_NAMELEN];
+	/* list of info structures related to this target portal group */
+	struct list_head info_list;
+};
+
+#define SCSIBACK_INVALID_HANDLE (~0)
+
+static bool log_print_stat;
+module_param(log_print_stat, bool, 0644);
+
+static int scsiback_max_buffer_pages = 1024;
+module_param_named(max_buffer_pages, scsiback_max_buffer_pages, int, 0644);
+MODULE_PARM_DESC(max_buffer_pages,
+"Maximum number of free pages to keep in backend buffer");
+
+/* Global spinlock to protect scsiback TPG list */
+static DEFINE_MUTEX(scsiback_mutex);
+static LIST_HEAD(scsiback_list);
+
+static void scsiback_get(struct vscsibk_info *info)
+{
+	atomic_inc(&info->nr_unreplied_reqs);
+}
+
+static void scsiback_put(struct vscsibk_info *info)
+{
+	if (atomic_dec_and_test(&info->nr_unreplied_reqs))
+		wake_up(&info->waiting_to_free);
+}
+
+static unsigned long vaddr_page(struct page *page)
+{
+	unsigned long pfn = page_to_pfn(page);
+
+	return (unsigned long)pfn_to_kaddr(pfn);
+}
+
+static unsigned long vaddr(struct vscsibk_pend *req, int seg)
+{
+	return vaddr_page(req->pages[seg]);
+}
+
+static void scsiback_print_status(char *sense_buffer, int errors,
+					struct vscsibk_pend *pending_req)
+{
+	struct scsiback_tpg *tpg = pending_req->v2p->tpg;
+
+	pr_err("[%s:%d] cmnd[0]=%02x -> st=%02x msg=%02x host=%02x\n",
+	       tpg->tport->tport_name, pending_req->v2p->lun,
+	       pending_req->cmnd[0], errors & 0xff, COMMAND_COMPLETE,
+	       host_byte(errors));
+}
+
+static void scsiback_fast_flush_area(struct vscsibk_pend *req)
+{
+	struct gnttab_unmap_grant_ref unmap[VSCSI_GRANT_BATCH];
+	struct page *pages[VSCSI_GRANT_BATCH];
+	unsigned int i, invcount = 0;
+	grant_handle_t handle;
+	int err;
+
+	kfree(req->sgl);
+	req->sgl = NULL;
+	req->n_sg = 0;
+
+	if (!req->n_grants)
+		return;
+
+	for (i = 0; i < req->n_grants; i++) {
+		handle = req->grant_handles[i];
+		if (handle == SCSIBACK_INVALID_HANDLE)
+			continue;
+		gnttab_set_unmap_op(&unmap[invcount], vaddr(req, i),
+				    GNTMAP_host_map, handle);
+		req->grant_handles[i] = SCSIBACK_INVALID_HANDLE;
+		pages[invcount] = req->pages[i];
+		put_page(pages[invcount]);
+		invcount++;
+		if (invcount < VSCSI_GRANT_BATCH)
+			continue;
+		err = gnttab_unmap_refs(unmap, NULL, pages, invcount);
+		BUG_ON(err);
+		invcount = 0;
+	}
+
+	if (invcount) {
+		err = gnttab_unmap_refs(unmap, NULL, pages, invcount);
+		BUG_ON(err);
+	}
+
+	gnttab_page_cache_put(&req->info->free_pages, req->pages,
+			      req->n_grants);
+	req->n_grants = 0;
+}
+
+static void scsiback_free_translation_entry(struct kref *kref)
+{
+	struct v2p_entry *entry = container_of(kref, struct v2p_entry, kref);
+	struct scsiback_tpg *tpg = entry->tpg;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_fe_count--;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	kfree(entry);
+}
+
+static int32_t scsiback_result(int32_t result)
+{
+	int32_t host_status;
+
+	switch (XEN_VSCSIIF_RSLT_HOST(result)) {
+	case DID_OK:
+		host_status = XEN_VSCSIIF_RSLT_HOST_OK;
+		break;
+	case DID_NO_CONNECT:
+		host_status = XEN_VSCSIIF_RSLT_HOST_NO_CONNECT;
+		break;
+	case DID_BUS_BUSY:
+		host_status = XEN_VSCSIIF_RSLT_HOST_BUS_BUSY;
+		break;
+	case DID_TIME_OUT:
+		host_status = XEN_VSCSIIF_RSLT_HOST_TIME_OUT;
+		break;
+	case DID_BAD_TARGET:
+		host_status = XEN_VSCSIIF_RSLT_HOST_BAD_TARGET;
+		break;
+	case DID_ABORT:
+		host_status = XEN_VSCSIIF_RSLT_HOST_ABORT;
+		break;
+	case DID_PARITY:
+		host_status = XEN_VSCSIIF_RSLT_HOST_PARITY;
+		break;
+	case DID_ERROR:
+		host_status = XEN_VSCSIIF_RSLT_HOST_ERROR;
+		break;
+	case DID_RESET:
+		host_status = XEN_VSCSIIF_RSLT_HOST_RESET;
+		break;
+	case DID_BAD_INTR:
+		host_status = XEN_VSCSIIF_RSLT_HOST_BAD_INTR;
+		break;
+	case DID_PASSTHROUGH:
+		host_status = XEN_VSCSIIF_RSLT_HOST_PASSTHROUGH;
+		break;
+	case DID_SOFT_ERROR:
+		host_status = XEN_VSCSIIF_RSLT_HOST_SOFT_ERROR;
+		break;
+	case DID_IMM_RETRY:
+		host_status = XEN_VSCSIIF_RSLT_HOST_IMM_RETRY;
+		break;
+	case DID_REQUEUE:
+		host_status = XEN_VSCSIIF_RSLT_HOST_REQUEUE;
+		break;
+	case DID_TRANSPORT_DISRUPTED:
+		host_status = XEN_VSCSIIF_RSLT_HOST_TRANSPORT_DISRUPTED;
+		break;
+	case DID_TRANSPORT_FAILFAST:
+		host_status = XEN_VSCSIIF_RSLT_HOST_TRANSPORT_FAILFAST;
+		break;
+	case DID_TRANSPORT_MARGINAL:
+		host_status = XEN_VSCSIIF_RSLT_HOST_TRANSPORT_MARGINAL;
+		break;
+	default:
+		host_status = XEN_VSCSIIF_RSLT_HOST_ERROR;
+		break;
+	}
+
+	return (host_status << 16) | (result & 0x00ffff);
+}
+
+static void scsiback_send_response(struct vscsibk_info *info,
+			char *sense_buffer, int32_t result, uint32_t resid,
+			uint16_t rqid)
+{
+	struct vscsiif_response *ring_res;
+	int notify;
+	struct scsi_sense_hdr sshdr;
+	unsigned long flags;
+	unsigned len;
+
+	spin_lock_irqsave(&info->ring_lock, flags);
+
+	ring_res = RING_GET_RESPONSE(&info->ring, info->ring.rsp_prod_pvt);
+	info->ring.rsp_prod_pvt++;
+
+	ring_res->rslt   = scsiback_result(result);
+	ring_res->rqid   = rqid;
+
+	if (sense_buffer != NULL &&
+	    scsi_normalize_sense(sense_buffer, VSCSIIF_SENSE_BUFFERSIZE,
+				 &sshdr)) {
+		len = min_t(unsigned, 8 + sense_buffer[7],
+			    VSCSIIF_SENSE_BUFFERSIZE);
+		memcpy(ring_res->sense_buffer, sense_buffer, len);
+		ring_res->sense_len = len;
+	} else {
+		ring_res->sense_len = 0;
+	}
+
+	ring_res->residual_len = resid;
+
+	RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&info->ring, notify);
+	spin_unlock_irqrestore(&info->ring_lock, flags);
+
+	if (notify)
+		notify_remote_via_irq(info->irq);
+}
+
+static void scsiback_do_resp_with_sense(char *sense_buffer, int32_t result,
+			uint32_t resid, struct vscsibk_pend *pending_req)
+{
+	scsiback_send_response(pending_req->info, sense_buffer, result,
+			       resid, pending_req->rqid);
+
+	if (pending_req->v2p)
+		kref_put(&pending_req->v2p->kref,
+			 scsiback_free_translation_entry);
+}
+
+static void scsiback_cmd_done(struct vscsibk_pend *pending_req)
+{
+	struct vscsibk_info *info = pending_req->info;
+	unsigned char *sense_buffer;
+	unsigned int resid;
+	int errors;
+
+	sense_buffer = pending_req->sense_buffer;
+	resid        = pending_req->se_cmd.residual_count;
+	errors       = pending_req->result;
+
+	if (errors && log_print_stat)
+		scsiback_print_status(sense_buffer, errors, pending_req);
+
+	scsiback_fast_flush_area(pending_req);
+	scsiback_do_resp_with_sense(sense_buffer, errors, resid, pending_req);
+	scsiback_put(info);
+	/*
+	 * Drop the extra KREF_ACK reference taken by target_submit_cmd_map_sgls()
+	 * ahead of scsiback_check_stop_free() ->  transport_generic_free_cmd()
+	 * final se_cmd->cmd_kref put.
+	 */
+	target_put_sess_cmd(&pending_req->se_cmd);
+}
+
+static void scsiback_cmd_exec(struct vscsibk_pend *pending_req)
+{
+	struct se_cmd *se_cmd = &pending_req->se_cmd;
+	struct se_session *sess = pending_req->v2p->tpg->tpg_nexus->tvn_se_sess;
+
+	scsiback_get(pending_req->info);
+	se_cmd->tag = pending_req->rqid;
+	target_init_cmd(se_cmd, sess, pending_req->sense_buffer,
+			pending_req->v2p->lun, pending_req->data_len, 0,
+			pending_req->sc_data_direction, TARGET_SCF_ACK_KREF);
+
+	if (target_submit_prep(se_cmd, pending_req->cmnd, pending_req->sgl,
+			       pending_req->n_sg, NULL, 0, NULL, 0, GFP_KERNEL))
+		return;
+
+	target_submit(se_cmd);
+}
+
+static int scsiback_gnttab_data_map_batch(struct gnttab_map_grant_ref *map,
+	struct page **pg, grant_handle_t *grant, int cnt)
+{
+	int err, i;
+
+	if (!cnt)
+		return 0;
+
+	err = gnttab_map_refs(map, NULL, pg, cnt);
+	for (i = 0; i < cnt; i++) {
+		if (unlikely(map[i].status != GNTST_okay)) {
+			pr_err("invalid buffer -- could not remap it\n");
+			map[i].handle = SCSIBACK_INVALID_HANDLE;
+			if (!err)
+				err = -ENOMEM;
+		} else {
+			get_page(pg[i]);
+		}
+		grant[i] = map[i].handle;
+	}
+	return err;
+}
+
+static int scsiback_gnttab_data_map_list(struct vscsibk_pend *pending_req,
+			struct scsiif_request_segment *seg, struct page **pg,
+			grant_handle_t *grant, int cnt, u32 flags)
+{
+	int mapcount = 0, i, err = 0;
+	struct gnttab_map_grant_ref map[VSCSI_GRANT_BATCH];
+	struct vscsibk_info *info = pending_req->info;
+
+	for (i = 0; i < cnt; i++) {
+		if (gnttab_page_cache_get(&info->free_pages, pg + mapcount)) {
+			gnttab_page_cache_put(&info->free_pages, pg, mapcount);
+			pr_err("no grant page\n");
+			return -ENOMEM;
+		}
+		gnttab_set_map_op(&map[mapcount], vaddr_page(pg[mapcount]),
+				  flags, seg[i].gref, info->domid);
+		mapcount++;
+		if (mapcount < VSCSI_GRANT_BATCH)
+			continue;
+		err = scsiback_gnttab_data_map_batch(map, pg, grant, mapcount);
+		pg += mapcount;
+		grant += mapcount;
+		pending_req->n_grants += mapcount;
+		if (err)
+			return err;
+		mapcount = 0;
+	}
+	err = scsiback_gnttab_data_map_batch(map, pg, grant, mapcount);
+	pending_req->n_grants += mapcount;
+	return err;
+}
+
+static int scsiback_gnttab_data_map(struct vscsiif_request *ring_req,
+					struct vscsibk_pend *pending_req)
+{
+	u32 flags;
+	int i, err, n_segs, i_seg = 0;
+	struct page **pg;
+	struct scsiif_request_segment *seg;
+	unsigned long end_seg = 0;
+	unsigned int nr_segments = (unsigned int)ring_req->nr_segments;
+	unsigned int nr_sgl = 0;
+	struct scatterlist *sg;
+	grant_handle_t *grant;
+
+	pending_req->n_sg = 0;
+	pending_req->n_grants = 0;
+	pending_req->data_len = 0;
+
+	nr_segments &= ~VSCSIIF_SG_GRANT;
+	if (!nr_segments)
+		return 0;
+
+	if (nr_segments > VSCSIIF_SG_TABLESIZE) {
+		pr_debug("invalid parameter nr_seg = %d\n",
+			ring_req->nr_segments);
+		return -EINVAL;
+	}
+
+	if (ring_req->nr_segments & VSCSIIF_SG_GRANT) {
+		err = scsiback_gnttab_data_map_list(pending_req, ring_req->seg,
+			pending_req->pages, pending_req->grant_handles,
+			nr_segments, GNTMAP_host_map | GNTMAP_readonly);
+		if (err)
+			return err;
+		nr_sgl = nr_segments;
+		nr_segments = 0;
+		for (i = 0; i < nr_sgl; i++) {
+			n_segs = ring_req->seg[i].length /
+				 sizeof(struct scsiif_request_segment);
+			if ((unsigned)ring_req->seg[i].offset +
+			    (unsigned)ring_req->seg[i].length > PAGE_SIZE ||
+			    n_segs * sizeof(struct scsiif_request_segment) !=
+			    ring_req->seg[i].length)
+				return -EINVAL;
+			nr_segments += n_segs;
+		}
+		if (nr_segments > SG_ALL) {
+			pr_debug("invalid nr_seg = %d\n", nr_segments);
+			return -EINVAL;
+		}
+	}
+
+	/* free of (sgl) in fast_flush_area() */
+	pending_req->sgl = kmalloc_objs(struct scatterlist, nr_segments);
+	if (!pending_req->sgl)
+		return -ENOMEM;
+
+	sg_init_table(pending_req->sgl, nr_segments);
+	pending_req->n_sg = nr_segments;
+
+	flags = GNTMAP_host_map;
+	if (pending_req->sc_data_direction == DMA_TO_DEVICE)
+		flags |= GNTMAP_readonly;
+
+	pg = pending_req->pages + nr_sgl;
+	grant = pending_req->grant_handles + nr_sgl;
+	if (!nr_sgl) {
+		seg = ring_req->seg;
+		err = scsiback_gnttab_data_map_list(pending_req, seg,
+			pg, grant, nr_segments, flags);
+		if (err)
+			return err;
+	} else {
+		for (i = 0; i < nr_sgl; i++) {
+			seg = (struct scsiif_request_segment *)(
+			      vaddr(pending_req, i) + ring_req->seg[i].offset);
+			n_segs = ring_req->seg[i].length /
+				 sizeof(struct scsiif_request_segment);
+			err = scsiback_gnttab_data_map_list(pending_req, seg,
+				pg, grant, n_segs, flags);
+			if (err)
+				return err;
+			pg += n_segs;
+			grant += n_segs;
+		}
+		end_seg = vaddr(pending_req, 0) + ring_req->seg[0].offset;
+		seg = (struct scsiif_request_segment *)end_seg;
+		end_seg += ring_req->seg[0].length;
+		pg = pending_req->pages + nr_sgl;
+	}
+
+	for_each_sg(pending_req->sgl, sg, nr_segments, i) {
+		sg_set_page(sg, pg[i], seg->length, seg->offset);
+		pending_req->data_len += seg->length;
+		seg++;
+		if (nr_sgl && (unsigned long)seg >= end_seg) {
+			i_seg++;
+			end_seg = vaddr(pending_req, i_seg) +
+				  ring_req->seg[i_seg].offset;
+			seg = (struct scsiif_request_segment *)end_seg;
+			end_seg += ring_req->seg[i_seg].length;
+		}
+		if (sg->offset >= PAGE_SIZE ||
+		    sg->length > PAGE_SIZE ||
+		    sg->offset + sg->length > PAGE_SIZE)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void scsiback_disconnect(struct vscsibk_info *info)
+{
+	wait_event(info->waiting_to_free,
+		atomic_read(&info->nr_unreplied_reqs) == 0);
+
+	unbind_from_irqhandler(info->irq, info);
+	info->irq = 0;
+	xenbus_unmap_ring_vfree(info->dev, info->ring.sring);
+}
+
+/*
+ * Send the error response for a request that did not reach the target core
+ * and return its tag.  Free the tag before the response drops the v2p
+ * reference that keeps the session alive, and snapshot what the response
+ * needs since returning the tag can let the slot be reused.
+ */
+static void scsiback_resp_and_free(struct vscsibk_pend *pending_req,
+				   int32_t result)
+{
+	struct vscsibk_info *info = pending_req->info;
+	struct v2p_entry *v2p = pending_req->v2p;
+	struct se_session *se_sess = v2p->tpg->tpg_nexus->tvn_se_sess;
+	u16 rqid = pending_req->rqid;
+
+	target_free_tag(se_sess, &pending_req->se_cmd);
+	scsiback_send_response(info, NULL, result, 0, rqid);
+	kref_put(&v2p->kref, scsiback_free_translation_entry);
+}
+
+static void scsiback_device_action(struct vscsibk_pend *pending_req,
+	enum tcm_tmreq_table act, int tag)
+{
+	struct scsiback_tpg *tpg = pending_req->v2p->tpg;
+	struct scsiback_nexus *nexus = tpg->tpg_nexus;
+	struct se_cmd *se_cmd = &pending_req->se_cmd;
+	u64 unpacked_lun = pending_req->v2p->lun;
+	int rc, err = XEN_VSCSIIF_RSLT_RESET_FAILED;
+
+	init_completion(&pending_req->tmr_done);
+
+	rc = target_submit_tmr(&pending_req->se_cmd, nexus->tvn_se_sess,
+			       &pending_req->sense_buffer[0],
+			       unpacked_lun, NULL, act, GFP_KERNEL,
+			       tag, TARGET_SCF_ACK_KREF);
+	if (rc)
+		goto err;
+
+	wait_for_completion(&pending_req->tmr_done);
+
+	err = (se_cmd->se_tmr_req->response == TMR_FUNCTION_COMPLETE) ?
+		XEN_VSCSIIF_RSLT_RESET_SUCCESS : XEN_VSCSIIF_RSLT_RESET_FAILED;
+
+	scsiback_do_resp_with_sense(NULL, err, 0, pending_req);
+	transport_generic_free_cmd(&pending_req->se_cmd, 0);
+	return;
+
+err:
+	scsiback_resp_and_free(pending_req, err);
+}
+
+/*
+  Perform virtual to physical translation
+*/
+static struct v2p_entry *scsiback_do_translation(struct vscsibk_info *info,
+			struct ids_tuple *v)
+{
+	struct v2p_entry *entry;
+	struct list_head *head = &(info->v2p_entry_lists);
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->v2p_lock, flags);
+	list_for_each_entry(entry, head, l) {
+		if ((entry->v.chn == v->chn) &&
+		    (entry->v.tgt == v->tgt) &&
+		    (entry->v.lun == v->lun)) {
+			kref_get(&entry->kref);
+			goto out;
+		}
+	}
+	entry = NULL;
+
+out:
+	spin_unlock_irqrestore(&info->v2p_lock, flags);
+	return entry;
+}
+
+static struct vscsibk_pend *scsiback_get_pend_req(struct vscsiif_back_ring *ring,
+				struct v2p_entry *v2p)
+{
+	struct scsiback_tpg *tpg = v2p->tpg;
+	struct scsiback_nexus *nexus = tpg->tpg_nexus;
+	struct se_session *se_sess = nexus->tvn_se_sess;
+	struct vscsibk_pend *req;
+	int tag, cpu, i;
+
+	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);
+	if (tag < 0) {
+		pr_err("Unable to obtain tag for vscsiif_request\n");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	req = &((struct vscsibk_pend *)se_sess->sess_cmd_map)[tag];
+	memset(req, 0, sizeof(*req));
+	req->se_cmd.map_tag = tag;
+	req->se_cmd.map_cpu = cpu;
+
+	for (i = 0; i < VSCSI_MAX_GRANTS; i++)
+		req->grant_handles[i] = SCSIBACK_INVALID_HANDLE;
+
+	return req;
+}
+
+static struct vscsibk_pend *prepare_pending_reqs(struct vscsibk_info *info,
+				struct vscsiif_back_ring *ring,
+				struct vscsiif_request *ring_req)
+{
+	struct vscsibk_pend *pending_req;
+	struct v2p_entry *v2p;
+	struct ids_tuple vir;
+
+	/* request range check from frontend */
+	if ((ring_req->sc_data_direction != DMA_BIDIRECTIONAL) &&
+		(ring_req->sc_data_direction != DMA_TO_DEVICE) &&
+		(ring_req->sc_data_direction != DMA_FROM_DEVICE) &&
+		(ring_req->sc_data_direction != DMA_NONE)) {
+		pr_debug("invalid parameter data_dir = %d\n",
+			ring_req->sc_data_direction);
+		return ERR_PTR(-EINVAL);
+	}
+	if (ring_req->cmd_len > VSCSIIF_MAX_COMMAND_SIZE) {
+		pr_debug("invalid parameter cmd_len = %d\n",
+			ring_req->cmd_len);
+		return ERR_PTR(-EINVAL);
+	}
+
+	vir.chn = ring_req->channel;
+	vir.tgt = ring_req->id;
+	vir.lun = ring_req->lun;
+
+	v2p = scsiback_do_translation(info, &vir);
+	if (!v2p) {
+		pr_debug("the v2p of (chn:%d, tgt:%d, lun:%d) doesn't exist.\n",
+			 vir.chn, vir.tgt, vir.lun);
+		return ERR_PTR(-ENODEV);
+	}
+
+	pending_req = scsiback_get_pend_req(ring, v2p);
+	if (IS_ERR(pending_req)) {
+		kref_put(&v2p->kref, scsiback_free_translation_entry);
+		return ERR_PTR(-ENOMEM);
+	}
+	pending_req->rqid = ring_req->rqid;
+	pending_req->info = info;
+	pending_req->v2p = v2p;
+	pending_req->sc_data_direction = ring_req->sc_data_direction;
+	pending_req->cmd_len = ring_req->cmd_len;
+	memcpy(pending_req->cmnd, ring_req->cmnd, pending_req->cmd_len);
+
+	return pending_req;
+}
+
+static int scsiback_do_cmd_fn(struct vscsibk_info *info,
+			      unsigned int *eoi_flags)
+{
+	struct vscsiif_back_ring *ring = &info->ring;
+	struct vscsiif_request ring_req;
+	struct vscsibk_pend *pending_req;
+	RING_IDX rc, rp;
+	int more_to_do;
+	uint32_t result;
+
+	rc = ring->req_cons;
+	rp = ring->sring->req_prod;
+	rmb();	/* guest system is accessing ring, too */
+
+	if (RING_REQUEST_PROD_OVERFLOW(ring, rp)) {
+		rc = ring->rsp_prod_pvt;
+		pr_warn("Dom%d provided bogus ring requests (%#x - %#x = %u). Halting ring processing\n",
+			   info->domid, rp, rc, rp - rc);
+		return -EINVAL;
+	}
+
+	while ((rc != rp)) {
+		*eoi_flags &= ~XEN_EOI_FLAG_SPURIOUS;
+
+		if (RING_REQUEST_CONS_OVERFLOW(ring, rc))
+			break;
+
+		RING_COPY_REQUEST(ring, rc, &ring_req);
+		ring->req_cons = ++rc;
+
+		pending_req = prepare_pending_reqs(info, ring, &ring_req);
+		if (IS_ERR(pending_req)) {
+			switch (PTR_ERR(pending_req)) {
+			case -ENODEV:
+				result = DID_NO_CONNECT;
+				break;
+			default:
+				result = DID_ERROR;
+				break;
+			}
+			scsiback_send_response(info, NULL, result << 16, 0,
+					       ring_req.rqid);
+			return 1;
+		}
+
+		switch (ring_req.act) {
+		case VSCSIIF_ACT_SCSI_CDB:
+			if (scsiback_gnttab_data_map(&ring_req, pending_req)) {
+				scsiback_fast_flush_area(pending_req);
+				scsiback_resp_and_free(pending_req,
+						       DID_ERROR << 16);
+			} else {
+				scsiback_cmd_exec(pending_req);
+			}
+			break;
+		case VSCSIIF_ACT_SCSI_ABORT:
+			scsiback_device_action(pending_req, TMR_ABORT_TASK,
+				ring_req.ref_rqid);
+			break;
+		case VSCSIIF_ACT_SCSI_RESET:
+			scsiback_device_action(pending_req, TMR_LUN_RESET, 0);
+			break;
+		default:
+			pr_err_ratelimited("invalid request\n");
+			scsiback_resp_and_free(pending_req, DID_ERROR << 16);
+			break;
+		}
+
+		/* Yield point for this unbounded loop. */
+		cond_resched();
+	}
+
+	gnttab_page_cache_shrink(&info->free_pages, scsiback_max_buffer_pages);
+
+	RING_FINAL_CHECK_FOR_REQUESTS(&info->ring, more_to_do);
+	return more_to_do;
+}
+
+static irqreturn_t scsiback_irq_fn(int irq, void *dev_id)
+{
+	struct vscsibk_info *info = dev_id;
+	int rc;
+	unsigned int eoi_flags = XEN_EOI_FLAG_SPURIOUS;
+
+	while ((rc = scsiback_do_cmd_fn(info, &eoi_flags)) > 0)
+		cond_resched();
+
+	/* In case of a ring error we keep the event channel masked. */
+	if (!rc)
+		xen_irq_lateeoi(irq, eoi_flags);
+
+	return IRQ_HANDLED;
+}
+
+static int scsiback_init_sring(struct vscsibk_info *info, grant_ref_t ring_ref,
+			evtchn_port_t evtchn)
+{
+	void *area;
+	struct vscsiif_sring *sring;
+	int err;
+
+	if (info->irq)
+		return -1;
+
+	err = xenbus_map_ring_valloc(info->dev, &ring_ref, 1, &area);
+	if (err)
+		return err;
+
+	sring = (struct vscsiif_sring *)area;
+	BACK_RING_INIT(&info->ring, sring, PAGE_SIZE);
+
+	err = bind_interdomain_evtchn_to_irq_lateeoi(info->dev, evtchn);
+	if (err < 0)
+		goto unmap_page;
+
+	info->irq = err;
+
+	err = request_threaded_irq(info->irq, NULL, scsiback_irq_fn,
+				   IRQF_ONESHOT, "vscsiif-backend", info);
+	if (err)
+		goto free_irq;
+
+	return 0;
+
+free_irq:
+	unbind_from_irqhandler(info->irq, info);
+	info->irq = 0;
+unmap_page:
+	xenbus_unmap_ring_vfree(info->dev, area);
+
+	return err;
+}
+
+static int scsiback_map(struct vscsibk_info *info)
+{
+	struct xenbus_device *dev = info->dev;
+	unsigned int ring_ref;
+	evtchn_port_t evtchn;
+	int err;
+
+	err = xenbus_gather(XBT_NIL, dev->otherend,
+			"ring-ref", "%u", &ring_ref,
+			"event-channel", "%u", &evtchn, NULL);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "reading %s ring", dev->otherend);
+		return err;
+	}
+
+	return scsiback_init_sring(info, ring_ref, evtchn);
+}
+
+/*
+  Check for a translation entry being present
+*/
+static struct v2p_entry *scsiback_chk_translation_entry(
+	struct vscsibk_info *info, struct ids_tuple *v)
+{
+	struct list_head *head = &(info->v2p_entry_lists);
+	struct v2p_entry *entry;
+
+	list_for_each_entry(entry, head, l)
+		if ((entry->v.chn == v->chn) &&
+		    (entry->v.tgt == v->tgt) &&
+		    (entry->v.lun == v->lun))
+			return entry;
+
+	return NULL;
+}
+
+/*
+  Add a new translation entry
+*/
+static int scsiback_add_translation_entry(struct vscsibk_info *info,
+					  char *phy, struct ids_tuple *v)
+{
+	int err = 0;
+	struct v2p_entry *new;
+	unsigned long flags;
+	char *lunp;
+	unsigned long long unpacked_lun;
+	struct se_lun *se_lun;
+	struct scsiback_tpg *tpg_entry, *tpg = NULL;
+	char *error = "doesn't exist";
+
+	lunp = strrchr(phy, ':');
+	if (!lunp) {
+		pr_err("illegal format of physical device %s\n", phy);
+		return -EINVAL;
+	}
+	*lunp = 0;
+	lunp++;
+	err = kstrtoull(lunp, 10, &unpacked_lun);
+	if (err < 0) {
+		pr_err("lun number not valid: %s\n", lunp);
+		return err;
+	}
+
+	mutex_lock(&scsiback_mutex);
+	list_for_each_entry(tpg_entry, &scsiback_list, tv_tpg_list) {
+		if (!strcmp(phy, tpg_entry->tport->tport_name) ||
+		    !strcmp(phy, tpg_entry->param_alias)) {
+			mutex_lock(&tpg_entry->se_tpg.tpg_lun_mutex);
+			hlist_for_each_entry(se_lun, &tpg_entry->se_tpg.tpg_lun_hlist, link) {
+				if (se_lun->unpacked_lun == unpacked_lun) {
+					if (!tpg_entry->tpg_nexus)
+						error = "nexus undefined";
+					else
+						tpg = tpg_entry;
+					break;
+				}
+			}
+			mutex_unlock(&tpg_entry->se_tpg.tpg_lun_mutex);
+			break;
+		}
+	}
+	if (tpg) {
+		mutex_lock(&tpg->tv_tpg_mutex);
+		tpg->tv_tpg_fe_count++;
+		mutex_unlock(&tpg->tv_tpg_mutex);
+	}
+	mutex_unlock(&scsiback_mutex);
+
+	if (!tpg) {
+		pr_err("%s:%llu %s\n", phy, unpacked_lun, error);
+		return -ENODEV;
+	}
+
+	new = kmalloc_obj(struct v2p_entry);
+	if (new == NULL) {
+		err = -ENOMEM;
+		goto out_free;
+	}
+
+	spin_lock_irqsave(&info->v2p_lock, flags);
+
+	/* Check double assignment to identical virtual ID */
+	if (scsiback_chk_translation_entry(info, v)) {
+		pr_warn("Virtual ID is already used. Assignment was not performed.\n");
+		err = -EEXIST;
+		goto out;
+	}
+
+	/* Create a new translation entry and add to the list */
+	kref_init(&new->kref);
+	new->v = *v;
+	new->tpg = tpg;
+	new->lun = unpacked_lun;
+	list_add_tail(&new->l, &info->v2p_entry_lists);
+
+out:
+	spin_unlock_irqrestore(&info->v2p_lock, flags);
+
+out_free:
+	if (err) {
+		mutex_lock(&tpg->tv_tpg_mutex);
+		tpg->tv_tpg_fe_count--;
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		kfree(new);
+	}
+
+	return err;
+}
+
+/*
+  Delete the translation entry specified
+*/
+static int scsiback_del_translation_entry(struct vscsibk_info *info,
+					  struct ids_tuple *v)
+{
+	struct v2p_entry *entry;
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->v2p_lock, flags);
+	/* Find out the translation entry specified */
+	entry = scsiback_chk_translation_entry(info, v);
+	if (entry)
+		list_del(&entry->l);
+
+	spin_unlock_irqrestore(&info->v2p_lock, flags);
+
+	if (!entry)
+		return -ENOENT;
+
+	kref_put(&entry->kref, scsiback_free_translation_entry);
+	return 0;
+}
+
+static void scsiback_do_add_lun(struct vscsibk_info *info, const char *state,
+				char *phy, struct ids_tuple *vir, int try)
+{
+	struct v2p_entry *entry;
+	unsigned long flags;
+	int err;
+
+	if (try) {
+		spin_lock_irqsave(&info->v2p_lock, flags);
+		entry = scsiback_chk_translation_entry(info, vir);
+		spin_unlock_irqrestore(&info->v2p_lock, flags);
+		if (entry)
+			return;
+	}
+	if (!scsiback_add_translation_entry(info, phy, vir)) {
+		if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
+				  "%d", XenbusStateInitialised)) {
+			pr_err("xenbus_printf error %s\n", state);
+			scsiback_del_translation_entry(info, vir);
+		}
+	} else if (!try) {
+		err = xenbus_printf(XBT_NIL, info->dev->nodename, state,
+			      "%d", XenbusStateClosed);
+		if (err)
+			xenbus_dev_error(info->dev, err,
+				"%s: writing %s", __func__, state);
+	}
+}
+
+static void scsiback_do_del_lun(struct vscsibk_info *info, const char *state,
+				struct ids_tuple *vir)
+{
+	if (!scsiback_del_translation_entry(info, vir)) {
+		if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
+				  "%d", XenbusStateClosed))
+			pr_err("xenbus_printf error %s\n", state);
+	}
+}
+
+#define VSCSIBACK_OP_ADD_OR_DEL_LUN	1
+#define VSCSIBACK_OP_UPDATEDEV_STATE	2
+
+static void scsiback_do_1lun_hotplug(struct vscsibk_info *info, int op,
+				     char *ent)
+{
+	int err;
+	struct ids_tuple vir;
+	char *val;
+	int device_state;
+	char phy[VSCSI_NAMELEN];
+	char str[64];
+	char state[64];
+	struct xenbus_device *dev = info->dev;
+
+	/* read status */
+	snprintf(state, sizeof(state), "vscsi-devs/%s/state", ent);
+	err = xenbus_scanf(XBT_NIL, dev->nodename, state, "%u", &device_state);
+	if (XENBUS_EXIST_ERR(err))
+		return;
+
+	/* physical SCSI device */
+	snprintf(str, sizeof(str), "vscsi-devs/%s/p-dev", ent);
+	val = xenbus_read(XBT_NIL, dev->nodename, str, NULL);
+	if (IS_ERR(val)) {
+		err = xenbus_printf(XBT_NIL, dev->nodename, state,
+			      "%d", XenbusStateClosed);
+		if (err)
+			xenbus_dev_error(info->dev, err,
+				"%s: writing %s", __func__, state);
+		return;
+	}
+	strscpy(phy, val, VSCSI_NAMELEN);
+	kfree(val);
+
+	/* virtual SCSI device */
+	snprintf(str, sizeof(str), "vscsi-devs/%s/v-dev", ent);
+	err = xenbus_scanf(XBT_NIL, dev->nodename, str, "%u:%u:%u:%u",
+			   &vir.hst, &vir.chn, &vir.tgt, &vir.lun);
+	if (XENBUS_EXIST_ERR(err)) {
+		err = xenbus_printf(XBT_NIL, dev->nodename, state,
+			      "%d", XenbusStateClosed);
+		if (err)
+			xenbus_dev_error(info->dev, err,
+				"%s: writing %s", __func__, state);
+		return;
+	}
+
+	switch (op) {
+	case VSCSIBACK_OP_ADD_OR_DEL_LUN:
+		switch (device_state) {
+		case XenbusStateInitialising:
+			scsiback_do_add_lun(info, state, phy, &vir, 0);
+			break;
+		case XenbusStateConnected:
+			scsiback_do_add_lun(info, state, phy, &vir, 1);
+			break;
+		case XenbusStateClosing:
+			scsiback_do_del_lun(info, state, &vir);
+			break;
+		default:
+			break;
+		}
+		break;
+
+	case VSCSIBACK_OP_UPDATEDEV_STATE:
+		if (device_state == XenbusStateInitialised) {
+			/* modify vscsi-devs/dev-x/state */
+			if (xenbus_printf(XBT_NIL, dev->nodename, state,
+					  "%d", XenbusStateConnected)) {
+				pr_err("xenbus_printf error %s\n", str);
+				scsiback_del_translation_entry(info, &vir);
+				xenbus_printf(XBT_NIL, dev->nodename, state,
+					      "%d", XenbusStateClosed);
+			}
+		}
+		break;
+	/* When it is necessary, processing is added here. */
+	default:
+		break;
+	}
+}
+
+static void scsiback_do_lun_hotplug(struct vscsibk_info *info, int op)
+{
+	int i;
+	char **dir;
+	unsigned int ndir = 0;
+
+	dir = xenbus_directory(XBT_NIL, info->dev->nodename, "vscsi-devs",
+			       &ndir);
+	if (IS_ERR(dir))
+		return;
+
+	for (i = 0; i < ndir; i++)
+		scsiback_do_1lun_hotplug(info, op, dir[i]);
+
+	kfree(dir);
+}
+
+static void scsiback_frontend_changed(struct xenbus_device *dev,
+					enum xenbus_state frontend_state)
+{
+	struct vscsibk_info *info = dev_get_drvdata(&dev->dev);
+
+	switch (frontend_state) {
+	case XenbusStateInitialising:
+		break;
+
+	case XenbusStateInitialised:
+		if (scsiback_map(info))
+			break;
+
+		scsiback_do_lun_hotplug(info, VSCSIBACK_OP_ADD_OR_DEL_LUN);
+		xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateConnected:
+		scsiback_do_lun_hotplug(info, VSCSIBACK_OP_UPDATEDEV_STATE);
+
+		if (dev->state == XenbusStateConnected)
+			break;
+
+		xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosing:
+		if (info->irq)
+			scsiback_disconnect(info);
+
+		xenbus_switch_state(dev, XenbusStateClosing);
+		break;
+
+	case XenbusStateClosed:
+		xenbus_switch_state(dev, XenbusStateClosed);
+		if (xenbus_dev_is_online(dev))
+			break;
+		fallthrough;	/* if not online */
+	case XenbusStateUnknown:
+		device_unregister(&dev->dev);
+		break;
+
+	case XenbusStateReconfiguring:
+		scsiback_do_lun_hotplug(info, VSCSIBACK_OP_ADD_OR_DEL_LUN);
+		xenbus_switch_state(dev, XenbusStateReconfigured);
+
+		break;
+
+	default:
+		xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
+					frontend_state);
+		break;
+	}
+}
+
+/*
+  Release the translation entry specfied
+*/
+static void scsiback_release_translation_entry(struct vscsibk_info *info)
+{
+	struct v2p_entry *entry, *tmp;
+	struct list_head *head = &(info->v2p_entry_lists);
+	struct list_head tmp_list;
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->v2p_lock, flags);
+
+	list_cut_before(&tmp_list, head, head);
+
+	spin_unlock_irqrestore(&info->v2p_lock, flags);
+
+	list_for_each_entry_safe(entry, tmp, &tmp_list, l) {
+		list_del(&entry->l);
+		kref_put(&entry->kref, scsiback_free_translation_entry);
+	}
+}
+
+static void scsiback_remove(struct xenbus_device *dev)
+{
+	struct vscsibk_info *info = dev_get_drvdata(&dev->dev);
+
+	if (info->irq)
+		scsiback_disconnect(info);
+
+	scsiback_release_translation_entry(info);
+
+	gnttab_page_cache_shrink(&info->free_pages, 0);
+
+	dev_set_drvdata(&dev->dev, NULL);
+	kfree(info);
+}
+
+static int scsiback_probe(struct xenbus_device *dev,
+			   const struct xenbus_device_id *id)
+{
+	int err;
+
+	struct vscsibk_info *info = kzalloc_obj(struct vscsibk_info);
+
+	pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
+
+	if (!info) {
+		xenbus_dev_fatal(dev, -ENOMEM, "allocating backend structure");
+		return -ENOMEM;
+	}
+	info->dev = dev;
+	dev_set_drvdata(&dev->dev, info);
+
+	info->domid = dev->otherend_id;
+	spin_lock_init(&info->ring_lock);
+	atomic_set(&info->nr_unreplied_reqs, 0);
+	init_waitqueue_head(&info->waiting_to_free);
+	info->dev = dev;
+	info->irq = 0;
+	INIT_LIST_HEAD(&info->v2p_entry_lists);
+	spin_lock_init(&info->v2p_lock);
+	gnttab_page_cache_init(&info->free_pages);
+
+	err = xenbus_printf(XBT_NIL, dev->nodename, "feature-sg-grant", "%u",
+			    SG_ALL);
+	if (err)
+		xenbus_dev_error(dev, err, "writing feature-sg-grant");
+
+	err = xenbus_switch_state(dev, XenbusStateInitWait);
+	if (err)
+		goto fail;
+
+	return 0;
+
+fail:
+	pr_warn("%s failed\n", __func__);
+	scsiback_remove(dev);
+
+	return err;
+}
+
+static char *scsiback_dump_proto_id(struct scsiback_tport *tport)
+{
+	switch (tport->tport_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return "SAS";
+	case SCSI_PROTOCOL_FCP:
+		return "FCP";
+	case SCSI_PROTOCOL_ISCSI:
+		return "iSCSI";
+	default:
+		break;
+	}
+
+	return "Unknown";
+}
+
+static char *scsiback_get_fabric_wwn(struct se_portal_group *se_tpg)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	struct scsiback_tport *tport = tpg->tport;
+
+	return &tport->tport_name[0];
+}
+
+static u16 scsiback_get_tag(struct se_portal_group *se_tpg)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	return tpg->tport_tpgt;
+}
+
+static struct se_wwn *
+scsiback_make_tport(struct target_fabric_configfs *tf,
+		     struct config_group *group,
+		     const char *name)
+{
+	struct scsiback_tport *tport;
+	char *ptr;
+	u64 wwpn = 0;
+	int off = 0;
+
+	tport = kzalloc_obj(struct scsiback_tport);
+	if (!tport)
+		return ERR_PTR(-ENOMEM);
+
+	tport->tport_wwpn = wwpn;
+	/*
+	 * Determine the emulated Protocol Identifier and Target Port Name
+	 * based on the incoming configfs directory name.
+	 */
+	ptr = strstr(name, "naa.");
+	if (ptr) {
+		tport->tport_proto_id = SCSI_PROTOCOL_SAS;
+		goto check_len;
+	}
+	ptr = strstr(name, "fc.");
+	if (ptr) {
+		tport->tport_proto_id = SCSI_PROTOCOL_FCP;
+		off = 3; /* Skip over "fc." */
+		goto check_len;
+	}
+	ptr = strstr(name, "iqn.");
+	if (ptr) {
+		tport->tport_proto_id = SCSI_PROTOCOL_ISCSI;
+		goto check_len;
+	}
+
+	pr_err("Unable to locate prefix for emulated Target Port: %s\n", name);
+	kfree(tport);
+	return ERR_PTR(-EINVAL);
+
+check_len:
+	if (strlen(name) >= VSCSI_NAMELEN) {
+		pr_err("Emulated %s Address: %s, exceeds max: %d\n", name,
+			scsiback_dump_proto_id(tport), VSCSI_NAMELEN);
+		kfree(tport);
+		return ERR_PTR(-EINVAL);
+	}
+	snprintf(&tport->tport_name[0], VSCSI_NAMELEN, "%s", &name[off]);
+
+	pr_debug("Allocated emulated Target %s Address: %s\n",
+		 scsiback_dump_proto_id(tport), name);
+
+	return &tport->tport_wwn;
+}
+
+static void scsiback_drop_tport(struct se_wwn *wwn)
+{
+	struct scsiback_tport *tport = container_of(wwn,
+				struct scsiback_tport, tport_wwn);
+
+	pr_debug("Deallocating emulated Target %s Address: %s\n",
+		 scsiback_dump_proto_id(tport), tport->tport_name);
+
+	kfree(tport);
+}
+
+static int scsiback_check_stop_free(struct se_cmd *se_cmd)
+{
+	return transport_generic_free_cmd(se_cmd, 0);
+}
+
+static void scsiback_release_cmd(struct se_cmd *se_cmd)
+{
+	target_free_tag(se_cmd->se_sess, se_cmd);
+}
+
+static int scsiback_write_pending(struct se_cmd *se_cmd)
+{
+	/* Go ahead and process the write immediately */
+	target_execute_cmd(se_cmd);
+
+	return 0;
+}
+
+static int scsiback_queue_data_in(struct se_cmd *se_cmd)
+{
+	struct vscsibk_pend *pending_req = container_of(se_cmd,
+				struct vscsibk_pend, se_cmd);
+
+	pending_req->result = SAM_STAT_GOOD;
+	scsiback_cmd_done(pending_req);
+	return 0;
+}
+
+static int scsiback_queue_status(struct se_cmd *se_cmd)
+{
+	struct vscsibk_pend *pending_req = container_of(se_cmd,
+				struct vscsibk_pend, se_cmd);
+
+	if (se_cmd->sense_buffer &&
+	    ((se_cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) ||
+	     (se_cmd->se_cmd_flags & SCF_EMULATED_TASK_SENSE)))
+		pending_req->result = SAM_STAT_CHECK_CONDITION;
+	else
+		pending_req->result = se_cmd->scsi_status;
+
+	scsiback_cmd_done(pending_req);
+	return 0;
+}
+
+static void scsiback_queue_tm_rsp(struct se_cmd *se_cmd)
+{
+	struct vscsibk_pend *pending_req = container_of(se_cmd,
+				struct vscsibk_pend, se_cmd);
+
+	complete(&pending_req->tmr_done);
+}
+
+static void scsiback_aborted_task(struct se_cmd *se_cmd)
+{
+}
+
+static ssize_t scsiback_tpg_param_alias_show(struct config_item *item,
+					     char *page)
+{
+	struct se_portal_group *se_tpg = param_to_tpg(item);
+	struct scsiback_tpg *tpg = container_of(se_tpg, struct scsiback_tpg,
+						se_tpg);
+	ssize_t rb;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	rb = snprintf(page, PAGE_SIZE, "%s\n", tpg->param_alias);
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	return rb;
+}
+
+static ssize_t scsiback_tpg_param_alias_store(struct config_item *item,
+					      const char *page, size_t count)
+{
+	struct se_portal_group *se_tpg = param_to_tpg(item);
+	struct scsiback_tpg *tpg = container_of(se_tpg, struct scsiback_tpg,
+						se_tpg);
+	int len;
+
+	if (strlen(page) >= VSCSI_NAMELEN) {
+		pr_err("param alias: %s, exceeds max: %d\n", page,
+			VSCSI_NAMELEN);
+		return -EINVAL;
+	}
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	len = snprintf(tpg->param_alias, VSCSI_NAMELEN, "%s", page);
+	if (tpg->param_alias[len - 1] == '\n')
+		tpg->param_alias[len - 1] = '\0';
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	return count;
+}
+
+CONFIGFS_ATTR(scsiback_tpg_param_, alias);
+
+static struct configfs_attribute *scsiback_param_attrs[] = {
+	&scsiback_tpg_param_attr_alias,
+	NULL,
+};
+
+static int scsiback_alloc_sess_cb(struct se_portal_group *se_tpg,
+				  struct se_session *se_sess, void *p)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+
+	tpg->tpg_nexus = p;
+	return 0;
+}
+
+static int scsiback_make_nexus(struct scsiback_tpg *tpg,
+				const char *name)
+{
+	struct scsiback_nexus *tv_nexus;
+	int ret = 0;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	if (tpg->tpg_nexus) {
+		pr_debug("tpg->tpg_nexus already exists\n");
+		ret = -EEXIST;
+		goto out_unlock;
+	}
+
+	tv_nexus = kzalloc_obj(struct scsiback_nexus);
+	if (!tv_nexus) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	tv_nexus->tvn_se_sess = target_setup_session(&tpg->se_tpg,
+						     VSCSI_DEFAULT_SESSION_TAGS,
+						     sizeof(struct vscsibk_pend),
+						     TARGET_PROT_NORMAL, name,
+						     tv_nexus, scsiback_alloc_sess_cb);
+	if (IS_ERR(tv_nexus->tvn_se_sess)) {
+		kfree(tv_nexus);
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+out_unlock:
+	mutex_unlock(&tpg->tv_tpg_mutex);
+	return ret;
+}
+
+static int scsiback_drop_nexus(struct scsiback_tpg *tpg)
+{
+	struct se_session *se_sess;
+	struct scsiback_nexus *tv_nexus;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tv_nexus = tpg->tpg_nexus;
+	if (!tv_nexus) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		return -ENODEV;
+	}
+
+	se_sess = tv_nexus->tvn_se_sess;
+	if (!se_sess) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		return -ENODEV;
+	}
+
+	if (tpg->tv_tpg_port_count != 0) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		pr_err("Unable to remove xen-pvscsi I_T Nexus with active TPG port count: %d\n",
+			tpg->tv_tpg_port_count);
+		return -EBUSY;
+	}
+
+	if (tpg->tv_tpg_fe_count != 0) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		pr_err("Unable to remove xen-pvscsi I_T Nexus with active TPG frontend count: %d\n",
+			tpg->tv_tpg_fe_count);
+		return -EBUSY;
+	}
+
+	pr_debug("Removing I_T Nexus to emulated %s Initiator Port: %s\n",
+		scsiback_dump_proto_id(tpg->tport),
+		tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
+
+	/*
+	 * Release the SCSI I_T Nexus to the emulated xen-pvscsi Target Port
+	 */
+	target_remove_session(se_sess);
+	tpg->tpg_nexus = NULL;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	kfree(tv_nexus);
+	return 0;
+}
+
+static ssize_t scsiback_tpg_nexus_show(struct config_item *item, char *page)
+{
+	struct se_portal_group *se_tpg = to_tpg(item);
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	struct scsiback_nexus *tv_nexus;
+	ssize_t ret;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tv_nexus = tpg->tpg_nexus;
+	if (!tv_nexus) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		return -ENODEV;
+	}
+	ret = snprintf(page, PAGE_SIZE, "%s\n",
+			tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	return ret;
+}
+
+static ssize_t scsiback_tpg_nexus_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct se_portal_group *se_tpg = to_tpg(item);
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	struct scsiback_tport *tport_wwn = tpg->tport;
+	unsigned char i_port[VSCSI_NAMELEN], *ptr, *port_ptr;
+	int ret;
+	/*
+	 * Shutdown the active I_T nexus if 'NULL' is passed.
+	 */
+	if (!strncmp(page, "NULL", 4)) {
+		ret = scsiback_drop_nexus(tpg);
+		return (!ret) ? count : ret;
+	}
+	/*
+	 * Otherwise make sure the passed virtual Initiator port WWN matches
+	 * the fabric protocol_id set in scsiback_make_tport(), and call
+	 * scsiback_make_nexus().
+	 */
+	if (strlen(page) >= VSCSI_NAMELEN) {
+		pr_err("Emulated NAA Sas Address: %s, exceeds max: %d\n",
+			page, VSCSI_NAMELEN);
+		return -EINVAL;
+	}
+	snprintf(&i_port[0], VSCSI_NAMELEN, "%s", page);
+
+	ptr = strstr(i_port, "naa.");
+	if (ptr) {
+		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_SAS) {
+			pr_err("Passed SAS Initiator Port %s does not match target port protoid: %s\n",
+				i_port, scsiback_dump_proto_id(tport_wwn));
+			return -EINVAL;
+		}
+		port_ptr = &i_port[0];
+		goto check_newline;
+	}
+	ptr = strstr(i_port, "fc.");
+	if (ptr) {
+		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_FCP) {
+			pr_err("Passed FCP Initiator Port %s does not match target port protoid: %s\n",
+				i_port, scsiback_dump_proto_id(tport_wwn));
+			return -EINVAL;
+		}
+		port_ptr = &i_port[3]; /* Skip over "fc." */
+		goto check_newline;
+	}
+	ptr = strstr(i_port, "iqn.");
+	if (ptr) {
+		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_ISCSI) {
+			pr_err("Passed iSCSI Initiator Port %s does not match target port protoid: %s\n",
+				i_port, scsiback_dump_proto_id(tport_wwn));
+			return -EINVAL;
+		}
+		port_ptr = &i_port[0];
+		goto check_newline;
+	}
+	pr_err("Unable to locate prefix for emulated Initiator Port: %s\n",
+		i_port);
+	return -EINVAL;
+	/*
+	 * Clear any trailing newline for the NAA WWN
+	 */
+check_newline:
+	if (i_port[strlen(i_port) - 1] == '\n')
+		i_port[strlen(i_port) - 1] = '\0';
+
+	ret = scsiback_make_nexus(tpg, port_ptr);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+CONFIGFS_ATTR(scsiback_tpg_, nexus);
+
+static struct configfs_attribute *scsiback_tpg_attrs[] = {
+	&scsiback_tpg_attr_nexus,
+	NULL,
+};
+
+static ssize_t
+scsiback_wwn_version_show(struct config_item *item, char *page)
+{
+	return sprintf(page, "xen-pvscsi fabric module %s on %s/%s on "
+		UTS_RELEASE"\n",
+		VSCSI_VERSION, utsname()->sysname, utsname()->machine);
+}
+
+CONFIGFS_ATTR_RO(scsiback_wwn_, version);
+
+static struct configfs_attribute *scsiback_wwn_attrs[] = {
+	&scsiback_wwn_attr_version,
+	NULL,
+};
+
+static int scsiback_port_link(struct se_portal_group *se_tpg,
+			       struct se_lun *lun)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_port_count++;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	return 0;
+}
+
+static void scsiback_port_unlink(struct se_portal_group *se_tpg,
+				  struct se_lun *lun)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_port_count--;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+}
+
+static struct se_portal_group *
+scsiback_make_tpg(struct se_wwn *wwn, const char *name)
+{
+	struct scsiback_tport *tport = container_of(wwn,
+			struct scsiback_tport, tport_wwn);
+
+	struct scsiback_tpg *tpg;
+	u16 tpgt;
+	int ret;
+
+	if (strstr(name, "tpgt_") != name)
+		return ERR_PTR(-EINVAL);
+	ret = kstrtou16(name + 5, 10, &tpgt);
+	if (ret)
+		return ERR_PTR(ret);
+
+	tpg = kzalloc_obj(struct scsiback_tpg);
+	if (!tpg)
+		return ERR_PTR(-ENOMEM);
+
+	mutex_init(&tpg->tv_tpg_mutex);
+	INIT_LIST_HEAD(&tpg->tv_tpg_list);
+	INIT_LIST_HEAD(&tpg->info_list);
+	tpg->tport = tport;
+	tpg->tport_tpgt = tpgt;
+
+	ret = core_tpg_register(wwn, &tpg->se_tpg, tport->tport_proto_id);
+	if (ret < 0) {
+		kfree(tpg);
+		return NULL;
+	}
+	mutex_lock(&scsiback_mutex);
+	list_add_tail(&tpg->tv_tpg_list, &scsiback_list);
+	mutex_unlock(&scsiback_mutex);
+
+	return &tpg->se_tpg;
+}
+
+static void scsiback_drop_tpg(struct se_portal_group *se_tpg)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+
+	mutex_lock(&scsiback_mutex);
+	list_del(&tpg->tv_tpg_list);
+	mutex_unlock(&scsiback_mutex);
+	/*
+	 * Release the virtual I_T Nexus for this xen-pvscsi TPG
+	 */
+	scsiback_drop_nexus(tpg);
+	/*
+	 * Deregister the se_tpg from TCM.
+	 */
+	core_tpg_deregister(se_tpg);
+	kfree(tpg);
+}
+
+static int scsiback_check_true(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static const struct target_core_fabric_ops scsiback_ops = {
+	.module				= THIS_MODULE,
+	.fabric_name			= "xen-pvscsi",
+	.tpg_get_wwn			= scsiback_get_fabric_wwn,
+	.tpg_get_tag			= scsiback_get_tag,
+	.tpg_check_demo_mode		= scsiback_check_true,
+	.tpg_check_demo_mode_cache	= scsiback_check_true,
+	.check_stop_free		= scsiback_check_stop_free,
+	.release_cmd			= scsiback_release_cmd,
+	.sess_get_initiator_sid		= NULL,
+	.write_pending			= scsiback_write_pending,
+	.queue_data_in			= scsiback_queue_data_in,
+	.queue_status			= scsiback_queue_status,
+	.queue_tm_rsp			= scsiback_queue_tm_rsp,
+	.aborted_task			= scsiback_aborted_task,
+	/*
+	 * Setup callers for generic logic in target_core_fabric_configfs.c
+	 */
+	.fabric_make_wwn		= scsiback_make_tport,
+	.fabric_drop_wwn		= scsiback_drop_tport,
+	.fabric_make_tpg		= scsiback_make_tpg,
+	.fabric_drop_tpg		= scsiback_drop_tpg,
+	.fabric_post_link		= scsiback_port_link,
+	.fabric_pre_unlink		= scsiback_port_unlink,
+
+	.tfc_wwn_attrs			= scsiback_wwn_attrs,
+	.tfc_tpg_base_attrs		= scsiback_tpg_attrs,
+	.tfc_tpg_param_attrs		= scsiback_param_attrs,
+
+	.default_compl_type		= TARGET_QUEUE_COMPL,
+	.default_submit_type		= TARGET_DIRECT_SUBMIT,
+	.direct_submit_supp		= 1,
+};
+
+static const struct xenbus_device_id scsiback_ids[] = {
+	{ "vscsi" },
+	{ "" }
+};
+
+static struct xenbus_driver scsiback_driver = {
+	.ids			= scsiback_ids,
+	.probe			= scsiback_probe,
+	.remove			= scsiback_remove,
+	.otherend_changed	= scsiback_frontend_changed
+};
+
+static int __init scsiback_init(void)
+{
+	int ret;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	pr_debug("xen-pvscsi: fabric module %s on %s/%s on "UTS_RELEASE"\n",
+		 VSCSI_VERSION, utsname()->sysname, utsname()->machine);
+
+	ret = xenbus_register_backend(&scsiback_driver);
+	if (ret)
+		goto out;
+
+	ret = target_register_template(&scsiback_ops);
+	if (ret)
+		goto out_unregister_xenbus;
+
+	return 0;
+
+out_unregister_xenbus:
+	xenbus_unregister_driver(&scsiback_driver);
+out:
+	pr_err("%s: error %d\n", __func__, ret);
+	return ret;
+}
+
+static void __exit scsiback_exit(void)
+{
+	target_unregister_template(&scsiback_ops);
+	xenbus_unregister_driver(&scsiback_driver);
+}
+
+module_init(scsiback_init);
+module_exit(scsiback_exit);
+
+MODULE_DESCRIPTION("Xen SCSI backend driver");
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS("xen-backend:vscsi");
+MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
diff --git a/drivers/xen/xenbus/Makefile b/drivers/xen/xenbus/Makefile
new file mode 100644
index 000000000..b0d696022
--- /dev/null
+++ b/drivers/xen/xenbus/Makefile
@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-y	+= xenbus.o
+
+xenbus-y := xenbus_client.o
+xenbus-y += xenbus_comms.o
+xenbus-y += xenbus_xs.o
+xenbus-y += xenbus_probe.o
+
+xenbus-$(CONFIG_XEN_BACKEND) += xenbus_probe_backend.o
+
+obj-y	+= xenbus_dev_frontend.o
+obj-$(CONFIG_XEN_BACKEND) += xenbus_dev_backend.o
+obj-$(CONFIG_XEN_XENBUS_FRONTEND) += xenbus_probe_frontend.o
diff --git a/drivers/xen/xenbus/xenbus.h b/drivers/xen/xenbus/xenbus.h
new file mode 100644
index 000000000..daba7f5e0
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus.h
@@ -0,0 +1,141 @@
+/*
+ * Private include for xenbus communications.
+ *
+ * Copyright (C) 2005 Rusty Russell, IBM Corporation
+ * Copyright (C) 2005 XenSource Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#ifndef _XENBUS_XENBUS_H
+#define _XENBUS_XENBUS_H
+
+#include <linux/mutex.h>
+#include <linux/uio.h>
+#include <xen/xenbus.h>
+
+#define XEN_BUS_ID_SIZE			20
+
+struct xen_bus_type {
+	char *root;
+	unsigned int levels;
+	int (*get_bus_id)(char bus_id[XEN_BUS_ID_SIZE], const char *nodename);
+	int (*probe)(struct xen_bus_type *bus, const char *type,
+		     const char *dir);
+	bool (*otherend_will_handle)(struct xenbus_watch *watch,
+				     const char *path, const char *token);
+	void (*otherend_changed)(struct xenbus_watch *watch, const char *path,
+				 const char *token);
+	struct bus_type bus;
+};
+
+enum xenstore_init {
+	XS_UNKNOWN,
+	XS_PV,
+	XS_HVM,
+	XS_LOCAL,
+};
+
+struct xs_watch_event {
+	struct list_head list;
+	unsigned int len;
+	struct xenbus_watch *handle;
+	const char *path;
+	const char *token;
+	char body[];
+};
+
+enum xb_req_state {
+	xb_req_state_queued,
+	xb_req_state_wait_reply,
+	xb_req_state_got_reply,
+	xb_req_state_aborted
+};
+
+struct xb_req_data {
+	struct list_head list;
+	wait_queue_head_t wq;
+	struct kref kref;
+	struct xsd_sockmsg msg;
+	uint32_t caller_req_id;
+	enum xsd_sockmsg_type type;
+	char *body;
+	const struct kvec *vec;
+	int num_vecs;
+	int err;
+	enum xb_req_state state;
+	bool user_req;
+	void (*cb)(struct xb_req_data *);
+	void *par;
+};
+
+extern enum xenstore_init xen_store_domain_type;
+extern const struct attribute_group *xenbus_dev_groups[];
+extern struct mutex xs_response_mutex;
+extern struct list_head xs_reply_list;
+extern struct list_head xb_write_list;
+extern wait_queue_head_t xb_waitq;
+extern struct mutex xb_write_mutex;
+
+int xs_init(void);
+int xb_init_comms(void);
+void xb_deinit_comms(void);
+int xs_watch_msg(struct xs_watch_event *event);
+void xs_request_exit(struct xb_req_data *req);
+void xs_free_req(struct kref *kref);
+
+int xenbus_match(struct device *_dev, const struct device_driver *_drv);
+int xenbus_dev_probe(struct device *_dev);
+void xenbus_dev_remove(struct device *_dev);
+int xenbus_register_driver_common(struct xenbus_driver *drv,
+				  struct xen_bus_type *bus,
+				  struct module *owner,
+				  const char *mod_name);
+int xenbus_probe_node(struct xen_bus_type *bus,
+		      const char *type,
+		      const char *nodename);
+int xenbus_probe_devices(struct xen_bus_type *bus);
+
+void xenbus_dev_changed(const char *node, struct xen_bus_type *bus);
+
+int xenbus_dev_freeze(struct device *dev);
+int xenbus_dev_restore(struct device *dev);
+int xenbus_dev_thaw(struct device *dev);
+
+void xenbus_otherend_changed(struct xenbus_watch *watch,
+			     const char *path, const char *token,
+			     int ignore_on_shutdown);
+
+int xenbus_read_otherend_details(struct xenbus_device *xendev,
+				 char *id_node, char *path_node);
+
+void xenbus_ring_ops_init(void);
+
+int xenbus_dev_request_and_reply(struct xsd_sockmsg *msg, void *par);
+void xenbus_dev_queue_reply(struct xb_req_data *req);
+
+extern unsigned int xb_dev_generation_id;
+
+#endif
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
new file mode 100644
index 000000000..27682cb5e
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -0,0 +1,974 @@
+/******************************************************************************
+ * Client-facing interface for the Xenbus driver.  In other words, the
+ * interface between the Xenbus and the device-specific code, be it the
+ * frontend or the backend of that driver.
+ *
+ * Copyright (C) 2005 XenSource Ltd
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/spinlock.h>
+#include <linux/vmalloc.h>
+#include <linux/export.h>
+#include <asm/xen/hypervisor.h>
+#include <xen/page.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/event_channel.h>
+#include <xen/balloon.h>
+#include <xen/events.h>
+#include <xen/grant_table.h>
+#include <xen/xenbus.h>
+#include <xen/xen.h>
+#include <xen/features.h>
+
+#include "xenbus.h"
+
+#define XENBUS_PAGES(_grants)	(DIV_ROUND_UP(_grants, XEN_PFN_PER_PAGE))
+
+#define XENBUS_MAX_RING_PAGES	(XENBUS_PAGES(XENBUS_MAX_RING_GRANTS))
+
+struct xenbus_map_node {
+	struct list_head next;
+	union {
+		struct {
+			struct vm_struct *area;
+		} pv;
+		struct {
+			struct page *pages[XENBUS_MAX_RING_PAGES];
+			unsigned long addrs[XENBUS_MAX_RING_GRANTS];
+			void *addr;
+		} hvm;
+	};
+	grant_handle_t handles[XENBUS_MAX_RING_GRANTS];
+	unsigned int   nr_handles;
+};
+
+struct map_ring_valloc {
+	struct xenbus_map_node *node;
+
+	/* Why do we need two arrays? See comment of __xenbus_map_ring */
+	unsigned long addrs[XENBUS_MAX_RING_GRANTS];
+	phys_addr_t phys_addrs[XENBUS_MAX_RING_GRANTS];
+
+	struct gnttab_map_grant_ref map[XENBUS_MAX_RING_GRANTS];
+	struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_GRANTS];
+
+	unsigned int idx;
+};
+
+static DEFINE_SPINLOCK(xenbus_valloc_lock);
+static LIST_HEAD(xenbus_valloc_pages);
+
+struct xenbus_ring_ops {
+	int (*map)(struct xenbus_device *dev, struct map_ring_valloc *info,
+		   grant_ref_t *gnt_refs, unsigned int nr_grefs,
+		   void **vaddr);
+	int (*unmap)(struct xenbus_device *dev, void *vaddr);
+};
+
+static const struct xenbus_ring_ops *ring_ops __read_mostly;
+
+const char *xenbus_strstate(enum xenbus_state state)
+{
+	static const char *const name[] = {
+		[ XenbusStateUnknown      ] = "Unknown",
+		[ XenbusStateInitialising ] = "Initialising",
+		[ XenbusStateInitWait     ] = "InitWait",
+		[ XenbusStateInitialised  ] = "Initialised",
+		[ XenbusStateConnected    ] = "Connected",
+		[ XenbusStateClosing      ] = "Closing",
+		[ XenbusStateClosed	  ] = "Closed",
+		[XenbusStateReconfiguring] = "Reconfiguring",
+		[XenbusStateReconfigured] = "Reconfigured",
+	};
+	return (state < ARRAY_SIZE(name)) ? name[state] : "INVALID";
+}
+EXPORT_SYMBOL_GPL(xenbus_strstate);
+
+/**
+ * xenbus_watch_path - register a watch
+ * @dev: xenbus device
+ * @path: path to watch
+ * @watch: watch to register
+ * @will_handle: events queuing determine callback
+ * @callback: callback to register
+ *
+ * Register a @watch on the given path, using the given xenbus_watch structure
+ * for storage, @will_handle function as the callback to determine if each
+ * event need to be queued, and the given @callback function as the callback.
+ * On success, the given @path will be saved as @watch->node, and remains the
+ * caller's to free.  On error, @watch->node will be NULL, the device will
+ * switch to %XenbusStateClosing, and the error will be saved in the store.
+ *
+ * Returns: %0 on success or -errno on error
+ */
+int xenbus_watch_path(struct xenbus_device *dev, const char *path,
+		      struct xenbus_watch *watch,
+		      bool (*will_handle)(struct xenbus_watch *,
+					  const char *, const char *),
+		      void (*callback)(struct xenbus_watch *,
+				       const char *, const char *))
+{
+	int err;
+
+	watch->node = path;
+	watch->will_handle = will_handle;
+	watch->callback = callback;
+
+	err = register_xenbus_watch(watch);
+
+	if (err) {
+		watch->node = NULL;
+		watch->will_handle = NULL;
+		watch->callback = NULL;
+		xenbus_dev_fatal(dev, err, "adding watch on %s", path);
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_watch_path);
+
+
+/**
+ * xenbus_watch_pathfmt - register a watch on a sprintf-formatted path
+ * @dev: xenbus device
+ * @watch: watch to register
+ * @will_handle: events queuing determine callback
+ * @callback: callback to register
+ * @pathfmt: format of path to watch
+ *
+ * Register a watch on the given @path, using the given xenbus_watch
+ * structure for storage, @will_handle function as the callback to determine if
+ * each event need to be queued, and the given @callback function as the
+ * callback.  On success, the watched path (@path/@path2) will be saved
+ * as @watch->node, and becomes the caller's to kfree().
+ * On error, watch->node will be NULL, so the caller has nothing to
+ * free, the device will switch to %XenbusStateClosing, and the error will be
+ * saved in the store.
+ *
+ * Returns: %0 on success or -errno on error
+ */
+int xenbus_watch_pathfmt(struct xenbus_device *dev,
+			 struct xenbus_watch *watch,
+			 bool (*will_handle)(struct xenbus_watch *,
+					const char *, const char *),
+			 void (*callback)(struct xenbus_watch *,
+					  const char *, const char *),
+			 const char *pathfmt, ...)
+{
+	int err;
+	va_list ap;
+	char *path;
+
+	va_start(ap, pathfmt);
+	path = kvasprintf(GFP_NOIO | __GFP_HIGH, pathfmt, ap);
+	va_end(ap);
+
+	if (!path) {
+		xenbus_dev_fatal(dev, -ENOMEM, "allocating path for watch");
+		return -ENOMEM;
+	}
+	err = xenbus_watch_path(dev, path, watch, will_handle, callback);
+
+	if (err)
+		kfree(path);
+	return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_watch_pathfmt);
+
+__printf(4, 5)
+static void xenbus_switch_fatal(struct xenbus_device *, int, int,
+				const char *, ...);
+
+static int
+__xenbus_switch_state(struct xenbus_device *dev,
+		      enum xenbus_state state, int depth)
+{
+	/* We check whether the state is currently set to the given value, and
+	   if not, then the state is set.  We don't want to unconditionally
+	   write the given state, because we don't want to fire watches
+	   unnecessarily.  Furthermore, if the node has gone, we don't write
+	   to it, as the device will be tearing down, and we don't want to
+	   resurrect that directory.
+
+	   Note that, because of this cached value of our state, this
+	   function will not take a caller's Xenstore transaction
+	   (something it was trying to in the past) because dev->state
+	   would not get reset if the transaction was aborted.
+	 */
+
+	struct xenbus_transaction xbt;
+	int current_state;
+	int err, abort;
+	bool vanished = false;
+
+	if (state == dev->state || dev->vanished)
+		return 0;
+
+again:
+	abort = 1;
+
+	err = xenbus_transaction_start(&xbt);
+	if (err) {
+		xenbus_switch_fatal(dev, depth, err, "starting transaction");
+		return 0;
+	}
+
+	err = xenbus_scanf(xbt, dev->nodename, "state", "%d", &current_state);
+	if (err != 1)
+		goto abort;
+	if (current_state != dev->state && current_state == XenbusStateInitialising) {
+		vanished = true;
+		goto abort;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename, "state", "%d", state);
+	if (err) {
+		xenbus_switch_fatal(dev, depth, err, "writing new state");
+		goto abort;
+	}
+
+	abort = 0;
+abort:
+	err = xenbus_transaction_end(xbt, abort);
+	if (err) {
+		if (err == -EAGAIN && !abort)
+			goto again;
+		xenbus_switch_fatal(dev, depth, err, "ending transaction");
+	} else if (!vanished)
+		dev->state = state;
+
+	return 0;
+}
+
+/**
+ * xenbus_switch_state - save the new state of a driver
+ * @dev: xenbus device
+ * @state: new state
+ *
+ * Advertise in the store a change of the given driver to the given new_state.
+ * On error, the device will switch to XenbusStateClosing, and the error
+ * will be saved in the store.
+ *
+ * Returns: %0 on success or -errno on error
+ */
+int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state state)
+{
+	return __xenbus_switch_state(dev, state, 0);
+}
+
+EXPORT_SYMBOL_GPL(xenbus_switch_state);
+
+int xenbus_frontend_closed(struct xenbus_device *dev)
+{
+	xenbus_switch_state(dev, XenbusStateClosed);
+	complete(&dev->down);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xenbus_frontend_closed);
+
+__printf(3, 0)
+static void xenbus_va_dev_error(struct xenbus_device *dev, int err,
+				const char *fmt, va_list ap)
+{
+	unsigned int len;
+	char *printf_buffer;
+	char *path_buffer;
+
+#define PRINTF_BUFFER_SIZE 4096
+
+	printf_buffer = kmalloc(PRINTF_BUFFER_SIZE, GFP_KERNEL);
+	if (!printf_buffer)
+		return;
+
+	len = sprintf(printf_buffer, "%i ", -err);
+	vsnprintf(printf_buffer + len, PRINTF_BUFFER_SIZE - len, fmt, ap);
+
+	dev_err(&dev->dev, "%s\n", printf_buffer);
+
+	path_buffer = kasprintf(GFP_KERNEL, "error/%s", dev->nodename);
+	if (path_buffer)
+		xenbus_write(XBT_NIL, path_buffer, "error", printf_buffer);
+
+	kfree(printf_buffer);
+	kfree(path_buffer);
+}
+
+/**
+ * xenbus_dev_error - place an error message into the store
+ * @dev: xenbus device
+ * @err: error to report
+ * @fmt: error message format
+ *
+ * Report the given negative errno into the store, along with the given
+ * formatted message.
+ */
+void xenbus_dev_error(struct xenbus_device *dev, int err, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	xenbus_va_dev_error(dev, err, fmt, ap);
+	va_end(ap);
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_error);
+
+/**
+ * xenbus_dev_fatal - put an error messages into the store and then shutdown
+ * @dev: xenbus device
+ * @err: error to report
+ * @fmt: error message format
+ *
+ * Equivalent to xenbus_dev_error(dev, err, fmt, args), followed by
+ * xenbus_switch_state(dev, XenbusStateClosing) to schedule an orderly
+ * closedown of this driver and its peer.
+ */
+
+void xenbus_dev_fatal(struct xenbus_device *dev, int err, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	xenbus_va_dev_error(dev, err, fmt, ap);
+	va_end(ap);
+
+	xenbus_switch_state(dev, XenbusStateClosing);
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_fatal);
+
+/*
+ * Equivalent to xenbus_dev_fatal(dev, err, fmt, args), but helps
+ * avoiding recursion within xenbus_switch_state.
+ */
+static void xenbus_switch_fatal(struct xenbus_device *dev, int depth, int err,
+				const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	xenbus_va_dev_error(dev, err, fmt, ap);
+	va_end(ap);
+
+	if (!depth)
+		__xenbus_switch_state(dev, XenbusStateClosing, 1);
+}
+
+/*
+ * xenbus_setup_ring
+ * @dev: xenbus device
+ * @vaddr: pointer to starting virtual address of the ring
+ * @nr_pages: number of pages to be granted
+ * @grefs: grant reference array to be filled in
+ *
+ * Allocate physically contiguous pages for a shared ring buffer and grant it
+ * to the peer of the given device. The ring buffer is initially filled with
+ * zeroes. The virtual address of the ring is stored at @vaddr and the
+ * grant references are stored in the @grefs array. In case of error @vaddr
+ * will be set to NULL and @grefs will be filled with INVALID_GRANT_REF.
+ */
+int xenbus_setup_ring(struct xenbus_device *dev, gfp_t gfp, void **vaddr,
+		      unsigned int nr_pages, grant_ref_t *grefs)
+{
+	unsigned long ring_size = nr_pages * XEN_PAGE_SIZE;
+	grant_ref_t gref_head;
+	unsigned int i;
+	void *addr;
+	int ret;
+
+	addr = *vaddr = alloc_pages_exact(ring_size, gfp | __GFP_ZERO);
+	if (!*vaddr) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	ret = gnttab_alloc_grant_references(nr_pages, &gref_head);
+	if (ret) {
+		xenbus_dev_fatal(dev, ret, "granting access to %u ring pages",
+				 nr_pages);
+		goto err;
+	}
+
+	for (i = 0; i < nr_pages; i++) {
+		unsigned long gfn;
+
+		if (is_vmalloc_addr(*vaddr))
+			gfn = pfn_to_gfn(vmalloc_to_pfn(addr));
+		else
+			gfn = virt_to_gfn(addr);
+
+		grefs[i] = gnttab_claim_grant_reference(&gref_head);
+		gnttab_grant_foreign_access_ref(grefs[i], dev->otherend_id,
+						gfn, 0);
+
+		addr += XEN_PAGE_SIZE;
+	}
+
+	return 0;
+
+ err:
+	if (*vaddr)
+		free_pages_exact(*vaddr, ring_size);
+	for (i = 0; i < nr_pages; i++)
+		grefs[i] = INVALID_GRANT_REF;
+	*vaddr = NULL;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xenbus_setup_ring);
+
+/*
+ * xenbus_teardown_ring
+ * @vaddr: starting virtual address of the ring
+ * @nr_pages: number of pages
+ * @grefs: grant reference array
+ *
+ * Remove grants for the shared ring buffer and free the associated memory.
+ * On return the grant reference array is filled with INVALID_GRANT_REF.
+ */
+void xenbus_teardown_ring(void **vaddr, unsigned int nr_pages,
+			  grant_ref_t *grefs)
+{
+	unsigned int i;
+
+	for (i = 0; i < nr_pages; i++) {
+		if (grefs[i] != INVALID_GRANT_REF) {
+			gnttab_end_foreign_access(grefs[i], NULL);
+			grefs[i] = INVALID_GRANT_REF;
+		}
+	}
+
+	if (*vaddr)
+		free_pages_exact(*vaddr, nr_pages * XEN_PAGE_SIZE);
+	*vaddr = NULL;
+}
+EXPORT_SYMBOL_GPL(xenbus_teardown_ring);
+
+/*
+ * Allocate an event channel for the given xenbus_device, assigning the newly
+ * created local port to *port.  Return 0 on success, or -errno on error.  On
+ * error, the device will switch to XenbusStateClosing, and the error will be
+ * saved in the store.
+ */
+int xenbus_alloc_evtchn(struct xenbus_device *dev, evtchn_port_t *port)
+{
+	struct evtchn_alloc_unbound alloc_unbound;
+	int err;
+
+	alloc_unbound.dom = DOMID_SELF;
+	alloc_unbound.remote_dom = dev->otherend_id;
+
+	err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
+					  &alloc_unbound);
+	if (err)
+		xenbus_dev_fatal(dev, err, "allocating event channel");
+	else
+		*port = alloc_unbound.port;
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_alloc_evtchn);
+
+
+/*
+ * Free an existing event channel. Returns 0 on success or -errno on error.
+ */
+int xenbus_free_evtchn(struct xenbus_device *dev, evtchn_port_t port)
+{
+	struct evtchn_close close;
+	int err;
+
+	close.port = port;
+
+	err = HYPERVISOR_event_channel_op(EVTCHNOP_close, &close);
+	if (err)
+		xenbus_dev_error(dev, err, "freeing event channel %u", port);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
+
+
+/**
+ * xenbus_map_ring_valloc - allocate & map pages of VA space
+ * @dev: xenbus device
+ * @gnt_refs: grant reference array
+ * @nr_grefs: number of grant references
+ * @vaddr: pointer to address to be filled out by mapping
+ *
+ * Map @nr_grefs pages of memory into this domain from another
+ * domain's grant table.  xenbus_map_ring_valloc allocates @nr_grefs
+ * pages of virtual address space, maps the pages to that address, and sets
+ * *vaddr to that address.  If an error is returned, device will switch to
+ * XenbusStateClosing and the error message will be saved in XenStore.
+ *
+ * Returns: %0 on success or -errno on error
+ */
+int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
+			   unsigned int nr_grefs, void **vaddr)
+{
+	int err;
+	struct map_ring_valloc *info;
+
+	*vaddr = NULL;
+
+	if (nr_grefs > XENBUS_MAX_RING_GRANTS)
+		return -EINVAL;
+
+	info = kzalloc_obj(*info);
+	if (!info)
+		return -ENOMEM;
+
+	info->node = kzalloc_obj(*info->node);
+	if (!info->node)
+		err = -ENOMEM;
+	else
+		err = ring_ops->map(dev, info, gnt_refs, nr_grefs, vaddr);
+
+	kfree(info->node);
+	kfree(info);
+	return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc);
+
+/* N.B. sizeof(phys_addr_t) doesn't always equal to sizeof(unsigned
+ * long), e.g. 32-on-64.  Caller is responsible for preparing the
+ * right array to feed into this function */
+static int __xenbus_map_ring(struct xenbus_device *dev,
+			     grant_ref_t *gnt_refs,
+			     unsigned int nr_grefs,
+			     grant_handle_t *handles,
+			     struct map_ring_valloc *info,
+			     unsigned int flags,
+			     bool *leaked)
+{
+	int i, j;
+
+	if (nr_grefs > XENBUS_MAX_RING_GRANTS)
+		return -EINVAL;
+
+	for (i = 0; i < nr_grefs; i++) {
+		gnttab_set_map_op(&info->map[i], info->phys_addrs[i], flags,
+				  gnt_refs[i], dev->otherend_id);
+		handles[i] = INVALID_GRANT_HANDLE;
+	}
+
+	gnttab_batch_map(info->map, i);
+
+	for (i = 0; i < nr_grefs; i++) {
+		if (info->map[i].status != GNTST_okay) {
+			xenbus_dev_fatal(dev, info->map[i].status,
+					 "mapping in shared page %d from domain %d",
+					 gnt_refs[i], dev->otherend_id);
+			goto fail;
+		} else
+			handles[i] = info->map[i].handle;
+	}
+
+	return 0;
+
+ fail:
+	for (i = j = 0; i < nr_grefs; i++) {
+		if (handles[i] != INVALID_GRANT_HANDLE) {
+			gnttab_set_unmap_op(&info->unmap[j],
+					    info->phys_addrs[i],
+					    GNTMAP_host_map, handles[i]);
+			j++;
+		}
+	}
+
+	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, info->unmap, j));
+
+	*leaked = false;
+	for (i = 0; i < j; i++) {
+		if (info->unmap[i].status != GNTST_okay) {
+			*leaked = true;
+			break;
+		}
+	}
+
+	return -ENOENT;
+}
+
+/**
+ * xenbus_unmap_ring - unmap memory from another domain
+ * @dev: xenbus device
+ * @handles: grant handle array
+ * @nr_handles: number of handles in the array
+ * @vaddrs: addresses to unmap
+ *
+ * Unmap memory in this domain that was imported from another domain.
+ *
+ * Returns: %0 on success or GNTST_* on error
+ * (see xen/include/interface/grant_table.h).
+ */
+static int xenbus_unmap_ring(struct xenbus_device *dev, grant_handle_t *handles,
+			     unsigned int nr_handles, unsigned long *vaddrs)
+{
+	struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_GRANTS];
+	int i;
+	int err;
+
+	if (nr_handles > XENBUS_MAX_RING_GRANTS)
+		return -EINVAL;
+
+	for (i = 0; i < nr_handles; i++)
+		gnttab_set_unmap_op(&unmap[i], vaddrs[i],
+				    GNTMAP_host_map, handles[i]);
+
+	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i));
+
+	err = GNTST_okay;
+	for (i = 0; i < nr_handles; i++) {
+		if (unmap[i].status != GNTST_okay) {
+			xenbus_dev_error(dev, unmap[i].status,
+					 "unmapping page at handle %d error %d",
+					 handles[i], unmap[i].status);
+			err = unmap[i].status;
+			break;
+		}
+	}
+
+	return err;
+}
+
+static void xenbus_map_ring_setup_grant_hvm(unsigned long gfn,
+					    unsigned int goffset,
+					    unsigned int len,
+					    void *data)
+{
+	struct map_ring_valloc *info = data;
+	unsigned long vaddr = (unsigned long)gfn_to_virt(gfn);
+
+	info->phys_addrs[info->idx] = vaddr;
+	info->addrs[info->idx] = vaddr;
+
+	info->idx++;
+}
+
+static int xenbus_map_ring_hvm(struct xenbus_device *dev,
+			       struct map_ring_valloc *info,
+			       grant_ref_t *gnt_ref,
+			       unsigned int nr_grefs,
+			       void **vaddr)
+{
+	struct xenbus_map_node *node = info->node;
+	int err;
+	void *addr;
+	bool leaked = false;
+	unsigned int nr_pages = XENBUS_PAGES(nr_grefs);
+
+	err = xen_alloc_unpopulated_pages(nr_pages, node->hvm.pages);
+	if (err)
+		goto out_err;
+
+	gnttab_foreach_grant(node->hvm.pages, nr_grefs,
+			     xenbus_map_ring_setup_grant_hvm,
+			     info);
+
+	err = __xenbus_map_ring(dev, gnt_ref, nr_grefs, node->handles,
+				info, GNTMAP_host_map, &leaked);
+	node->nr_handles = nr_grefs;
+
+	if (err)
+		goto out_free_ballooned_pages;
+
+	addr = vmap(node->hvm.pages, nr_pages, VM_MAP | VM_IOREMAP,
+		    PAGE_KERNEL);
+	if (!addr) {
+		err = -ENOMEM;
+		goto out_xenbus_unmap_ring;
+	}
+
+	node->hvm.addr = addr;
+
+	spin_lock(&xenbus_valloc_lock);
+	list_add(&node->next, &xenbus_valloc_pages);
+	spin_unlock(&xenbus_valloc_lock);
+
+	*vaddr = addr;
+	info->node = NULL;
+
+	return 0;
+
+ out_xenbus_unmap_ring:
+	if (!leaked)
+		xenbus_unmap_ring(dev, node->handles, nr_grefs, info->addrs);
+	else
+		pr_alert("leaking %p size %u page(s)",
+			 addr, nr_pages);
+ out_free_ballooned_pages:
+	if (!leaked)
+		xen_free_unpopulated_pages(nr_pages, node->hvm.pages);
+ out_err:
+	return err;
+}
+
+/**
+ * xenbus_unmap_ring_vfree - unmap a page of memory from another domain
+ * @dev: xenbus device
+ * @vaddr: addr to unmap
+ *
+ * Based on Rusty Russell's skeleton driver's unmap_page.
+ * Unmap a page of memory in this domain that was imported from another domain.
+ * Use xenbus_unmap_ring_vfree if you mapped in your memory with
+ * xenbus_map_ring_valloc (it will free the virtual address space).
+ *
+ * Returns: %0 on success or GNTST_* on error
+ * (see xen/include/interface/grant_table.h).
+ */
+int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
+{
+	return ring_ops->unmap(dev, vaddr);
+}
+EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree);
+
+#ifdef CONFIG_XEN_PV
+static int map_ring_apply(pte_t *pte, unsigned long addr, void *data)
+{
+	struct map_ring_valloc *info = data;
+
+	info->phys_addrs[info->idx++] = arbitrary_virt_to_machine(pte).maddr;
+	return 0;
+}
+
+static int xenbus_map_ring_pv(struct xenbus_device *dev,
+			      struct map_ring_valloc *info,
+			      grant_ref_t *gnt_refs,
+			      unsigned int nr_grefs,
+			      void **vaddr)
+{
+	struct xenbus_map_node *node = info->node;
+	struct vm_struct *area;
+	bool leaked = false;
+	int err = -ENOMEM;
+
+	area = get_vm_area(XEN_PAGE_SIZE * nr_grefs, VM_IOREMAP);
+	if (!area)
+		return -ENOMEM;
+	if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
+				XEN_PAGE_SIZE * nr_grefs, map_ring_apply, info))
+		goto failed;
+	err = __xenbus_map_ring(dev, gnt_refs, nr_grefs, node->handles,
+				info, GNTMAP_host_map | GNTMAP_contains_pte,
+				&leaked);
+	if (err)
+		goto failed;
+
+	node->nr_handles = nr_grefs;
+	node->pv.area = area;
+
+	spin_lock(&xenbus_valloc_lock);
+	list_add(&node->next, &xenbus_valloc_pages);
+	spin_unlock(&xenbus_valloc_lock);
+
+	*vaddr = area->addr;
+	info->node = NULL;
+
+	return 0;
+
+failed:
+	if (!leaked)
+		free_vm_area(area);
+	else
+		pr_alert("leaking VM area %p size %u page(s)", area, nr_grefs);
+
+	return err;
+}
+
+static int xenbus_unmap_ring_pv(struct xenbus_device *dev, void *vaddr)
+{
+	struct xenbus_map_node *node;
+	struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_GRANTS];
+	unsigned int level;
+	int i;
+	bool leaked = false;
+	int err;
+
+	spin_lock(&xenbus_valloc_lock);
+	list_for_each_entry(node, &xenbus_valloc_pages, next) {
+		if (node->pv.area->addr == vaddr) {
+			list_del(&node->next);
+			goto found;
+		}
+	}
+	node = NULL;
+ found:
+	spin_unlock(&xenbus_valloc_lock);
+
+	if (!node) {
+		xenbus_dev_error(dev, -ENOENT,
+				 "can't find mapped virtual address %p", vaddr);
+		return GNTST_bad_virt_addr;
+	}
+
+	for (i = 0; i < node->nr_handles; i++) {
+		unsigned long addr;
+
+		memset(&unmap[i], 0, sizeof(unmap[i]));
+		addr = (unsigned long)vaddr + (XEN_PAGE_SIZE * i);
+		unmap[i].host_addr = arbitrary_virt_to_machine(
+			lookup_address(addr, &level)).maddr;
+		unmap[i].dev_bus_addr = 0;
+		unmap[i].handle = node->handles[i];
+	}
+
+	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i));
+
+	err = GNTST_okay;
+	leaked = false;
+	for (i = 0; i < node->nr_handles; i++) {
+		if (unmap[i].status != GNTST_okay) {
+			leaked = true;
+			xenbus_dev_error(dev, unmap[i].status,
+					 "unmapping page at handle %d error %d",
+					 node->handles[i], unmap[i].status);
+			err = unmap[i].status;
+			break;
+		}
+	}
+
+	if (!leaked)
+		free_vm_area(node->pv.area);
+	else
+		pr_alert("leaking VM area %p size %u page(s)",
+			 node->pv.area, node->nr_handles);
+
+	kfree(node);
+	return err;
+}
+
+static const struct xenbus_ring_ops ring_ops_pv = {
+	.map = xenbus_map_ring_pv,
+	.unmap = xenbus_unmap_ring_pv,
+};
+#endif
+
+struct unmap_ring_hvm
+{
+	unsigned int idx;
+	unsigned long addrs[XENBUS_MAX_RING_GRANTS];
+};
+
+static void xenbus_unmap_ring_setup_grant_hvm(unsigned long gfn,
+					      unsigned int goffset,
+					      unsigned int len,
+					      void *data)
+{
+	struct unmap_ring_hvm *info = data;
+
+	info->addrs[info->idx] = (unsigned long)gfn_to_virt(gfn);
+
+	info->idx++;
+}
+
+static int xenbus_unmap_ring_hvm(struct xenbus_device *dev, void *vaddr)
+{
+	int rv;
+	struct xenbus_map_node *node;
+	void *addr;
+	struct unmap_ring_hvm info = {
+		.idx = 0,
+	};
+	unsigned int nr_pages;
+
+	spin_lock(&xenbus_valloc_lock);
+	list_for_each_entry(node, &xenbus_valloc_pages, next) {
+		addr = node->hvm.addr;
+		if (addr == vaddr) {
+			list_del(&node->next);
+			goto found;
+		}
+	}
+	node = addr = NULL;
+ found:
+	spin_unlock(&xenbus_valloc_lock);
+
+	if (!node) {
+		xenbus_dev_error(dev, -ENOENT,
+				 "can't find mapped virtual address %p", vaddr);
+		return GNTST_bad_virt_addr;
+	}
+
+	nr_pages = XENBUS_PAGES(node->nr_handles);
+
+	gnttab_foreach_grant(node->hvm.pages, node->nr_handles,
+			     xenbus_unmap_ring_setup_grant_hvm,
+			     &info);
+
+	rv = xenbus_unmap_ring(dev, node->handles, node->nr_handles,
+			       info.addrs);
+	if (!rv) {
+		vunmap(vaddr);
+		xen_free_unpopulated_pages(nr_pages, node->hvm.pages);
+	}
+	else
+		WARN(1, "Leaking %p, size %u page(s)\n", vaddr, nr_pages);
+
+	kfree(node);
+	return rv;
+}
+
+/**
+ * xenbus_read_driver_state - read state from a store path
+ * @dev: xenbus device pointer
+ * @path: path for driver
+ *
+ * Returns: the state of the driver rooted at the given store path, or
+ * XenbusStateUnknown if no state can be read.
+ */
+enum xenbus_state xenbus_read_driver_state(const struct xenbus_device *dev,
+					   const char *path)
+{
+	enum xenbus_state result;
+
+	if (dev && dev->vanished)
+		return XenbusStateUnknown;
+
+	int err = xenbus_gather(XBT_NIL, path, "state", "%d", &result, NULL);
+	if (err)
+		result = XenbusStateUnknown;
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(xenbus_read_driver_state);
+
+static const struct xenbus_ring_ops ring_ops_hvm = {
+	.map = xenbus_map_ring_hvm,
+	.unmap = xenbus_unmap_ring_hvm,
+};
+
+void __init xenbus_ring_ops_init(void)
+{
+#ifdef CONFIG_XEN_PV
+	if (xen_pv_domain())
+		ring_ops = &ring_ops_pv;
+	else
+#endif
+		ring_ops = &ring_ops_hvm;
+}
diff --git a/drivers/xen/xenbus/xenbus_comms.c b/drivers/xen/xenbus/xenbus_comms.c
new file mode 100644
index 000000000..82df2da1b
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus_comms.c
@@ -0,0 +1,483 @@
+/******************************************************************************
+ * xenbus_comms.c
+ *
+ * Low level code to talks to Xen Store: ringbuffer and event channel.
+ *
+ * Copyright (C) 2005 Rusty Russell, IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/wait.h>
+#include <linux/interrupt.h>
+#include <linux/kthread.h>
+#include <linux/sched.h>
+#include <linux/err.h>
+#include <xen/xenbus.h>
+#include <asm/xen/hypervisor.h>
+#include <xen/events.h>
+#include <xen/page.h>
+#include "xenbus.h"
+
+/* A list of replies. Currently only one will ever be outstanding. */
+LIST_HEAD(xs_reply_list);
+
+/* A list of write requests. */
+LIST_HEAD(xb_write_list);
+DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
+DEFINE_MUTEX(xb_write_mutex);
+
+/* Protect xenbus reader thread against save/restore. */
+DEFINE_MUTEX(xs_response_mutex);
+
+static int xenbus_irq;
+static struct task_struct *xenbus_task;
+
+static irqreturn_t wake_waiting(int irq, void *unused)
+{
+	wake_up(&xb_waitq);
+	return IRQ_HANDLED;
+}
+
+static int check_indexes(XENSTORE_RING_IDX cons, XENSTORE_RING_IDX prod)
+{
+	return ((prod - cons) <= XENSTORE_RING_SIZE);
+}
+
+static void *get_output_chunk(XENSTORE_RING_IDX cons,
+			      XENSTORE_RING_IDX prod,
+			      char *buf, uint32_t *len)
+{
+	*len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod);
+	if ((XENSTORE_RING_SIZE - (prod - cons)) < *len)
+		*len = XENSTORE_RING_SIZE - (prod - cons);
+	return buf + MASK_XENSTORE_IDX(prod);
+}
+
+static const void *get_input_chunk(XENSTORE_RING_IDX cons,
+				   XENSTORE_RING_IDX prod,
+				   const char *buf, uint32_t *len)
+{
+	*len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(cons);
+	if ((prod - cons) < *len)
+		*len = prod - cons;
+	return buf + MASK_XENSTORE_IDX(cons);
+}
+
+static int xb_data_to_write(void)
+{
+	struct xenstore_domain_interface *intf = xen_store_interface;
+
+	return (intf->req_prod - intf->req_cons) != XENSTORE_RING_SIZE &&
+		!list_empty(&xb_write_list);
+}
+
+/**
+ * xb_write - low level write
+ * @data: buffer to send
+ * @len: length of buffer
+ *
+ * Returns number of bytes written or -err.
+ */
+static int xb_write(const void *data, unsigned int len)
+{
+	struct xenstore_domain_interface *intf = xen_store_interface;
+	XENSTORE_RING_IDX cons, prod;
+	unsigned int bytes = 0;
+
+	while (len != 0) {
+		void *dst;
+		unsigned int avail;
+
+		/* Read indexes, then verify. */
+		cons = intf->req_cons;
+		prod = intf->req_prod;
+		if (!check_indexes(cons, prod)) {
+			intf->req_cons = intf->req_prod = 0;
+			return -EIO;
+		}
+		if (!xb_data_to_write())
+			return bytes;
+
+		/* Must write data /after/ reading the consumer index. */
+		virt_mb();
+
+		dst = get_output_chunk(cons, prod, intf->req, &avail);
+		if (avail == 0)
+			continue;
+		if (avail > len)
+			avail = len;
+
+		memcpy(dst, data, avail);
+		data += avail;
+		len -= avail;
+		bytes += avail;
+
+		/* Other side must not see new producer until data is there. */
+		virt_wmb();
+		intf->req_prod += avail;
+
+		/* Implies mb(): other side will see the updated producer. */
+		if (prod <= intf->req_cons)
+			notify_remote_via_evtchn(xen_store_evtchn);
+	}
+
+	return bytes;
+}
+
+static int xb_data_to_read(void)
+{
+	struct xenstore_domain_interface *intf = xen_store_interface;
+	return (intf->rsp_cons != intf->rsp_prod);
+}
+
+static int xb_read(void *data, unsigned int len)
+{
+	struct xenstore_domain_interface *intf = xen_store_interface;
+	XENSTORE_RING_IDX cons, prod;
+	unsigned int bytes = 0;
+
+	while (len != 0) {
+		unsigned int avail;
+		const char *src;
+
+		/* Read indexes, then verify. */
+		cons = intf->rsp_cons;
+		prod = intf->rsp_prod;
+		if (cons == prod)
+			return bytes;
+
+		if (!check_indexes(cons, prod)) {
+			intf->rsp_cons = intf->rsp_prod = 0;
+			return -EIO;
+		}
+
+		src = get_input_chunk(cons, prod, intf->rsp, &avail);
+		if (avail == 0)
+			continue;
+		if (avail > len)
+			avail = len;
+
+		/* Must read data /after/ reading the producer index. */
+		virt_rmb();
+
+		memcpy(data, src, avail);
+		data += avail;
+		len -= avail;
+		bytes += avail;
+
+		/* Other side must not see free space until we've copied out */
+		virt_mb();
+		intf->rsp_cons += avail;
+
+		/* Implies mb(): other side will see the updated consumer. */
+		if (intf->rsp_prod - cons >= XENSTORE_RING_SIZE)
+			notify_remote_via_evtchn(xen_store_evtchn);
+	}
+
+	return bytes;
+}
+
+static int process_msg(void)
+{
+	static struct {
+		struct xsd_sockmsg msg;
+		char *body;
+		union {
+			void *alloc;
+			struct xs_watch_event *watch;
+		};
+		bool in_msg;
+		bool in_hdr;
+		unsigned int read;
+	} state;
+	struct xb_req_data *req;
+	int err;
+	unsigned int len;
+
+	if (!state.in_msg) {
+		state.in_msg = true;
+		state.in_hdr = true;
+		state.read = 0;
+
+		/*
+		 * We must disallow save/restore while reading a message.
+		 * A partial read across s/r leaves us out of sync with
+		 * xenstored.
+		 * xs_response_mutex is locked as long as we are processing one
+		 * message. state.in_msg will be true as long as we are holding
+		 * the lock here.
+		 */
+		mutex_lock(&xs_response_mutex);
+
+		if (!xb_data_to_read()) {
+			/* We raced with save/restore: pending data 'gone'. */
+			mutex_unlock(&xs_response_mutex);
+			state.in_msg = false;
+			return 0;
+		}
+	}
+
+	if (state.in_hdr) {
+		if (state.read != sizeof(state.msg)) {
+			err = xb_read((void *)&state.msg + state.read,
+				      sizeof(state.msg) - state.read);
+			if (err < 0)
+				goto out;
+			state.read += err;
+			if (state.read != sizeof(state.msg))
+				return 0;
+			if (state.msg.len > XENSTORE_PAYLOAD_MAX) {
+				err = -EINVAL;
+				goto out;
+			}
+		}
+
+		len = state.msg.len + 1;
+		if (state.msg.type == XS_WATCH_EVENT)
+			len += sizeof(*state.watch);
+
+		state.alloc = kmalloc(len, GFP_NOIO | __GFP_HIGH);
+		if (!state.alloc)
+			return -ENOMEM;
+
+		if (state.msg.type == XS_WATCH_EVENT)
+			state.body = state.watch->body;
+		else
+			state.body = state.alloc;
+		state.in_hdr = false;
+		state.read = 0;
+	}
+
+	err = xb_read(state.body + state.read, state.msg.len - state.read);
+	if (err < 0)
+		goto out;
+
+	state.read += err;
+	if (state.read != state.msg.len)
+		return 0;
+
+	state.body[state.msg.len] = '\0';
+
+	if (state.msg.type == XS_WATCH_EVENT) {
+		state.watch->len = state.msg.len;
+		err = xs_watch_msg(state.watch);
+	} else {
+		err = -ENOENT;
+		mutex_lock(&xb_write_mutex);
+		list_for_each_entry(req, &xs_reply_list, list) {
+			if (req->msg.req_id == state.msg.req_id) {
+				list_del(&req->list);
+				err = 0;
+				break;
+			}
+		}
+		mutex_unlock(&xb_write_mutex);
+		if (err)
+			goto out;
+
+		if (req->state == xb_req_state_wait_reply) {
+			req->msg.req_id = req->caller_req_id;
+			req->msg.type = state.msg.type;
+			req->msg.len = state.msg.len;
+			req->body = state.body;
+			/* write body, then update state */
+			virt_wmb();
+			req->state = xb_req_state_got_reply;
+			req->cb(req);
+		}
+		kref_put(&req->kref, xs_free_req);
+	}
+
+	mutex_unlock(&xs_response_mutex);
+
+	state.in_msg = false;
+	state.alloc = NULL;
+	return err;
+
+ out:
+	mutex_unlock(&xs_response_mutex);
+	state.in_msg = false;
+	kfree(state.alloc);
+	state.alloc = NULL;
+	return err;
+}
+
+static int process_writes(void)
+{
+	static struct {
+		struct xb_req_data *req;
+		int idx;
+		unsigned int written;
+	} state;
+	void *base;
+	unsigned int len;
+	int err = 0;
+
+	if (!xb_data_to_write())
+		return 0;
+
+	mutex_lock(&xb_write_mutex);
+
+	if (!state.req) {
+		state.req = list_first_entry(&xb_write_list,
+					     struct xb_req_data, list);
+		state.idx = -1;
+		state.written = 0;
+	}
+
+	if (state.req->state == xb_req_state_aborted)
+		goto out_err;
+
+	while (state.idx < state.req->num_vecs) {
+		if (state.idx < 0) {
+			base = &state.req->msg;
+			len = sizeof(state.req->msg);
+		} else {
+			base = state.req->vec[state.idx].iov_base;
+			len = state.req->vec[state.idx].iov_len;
+		}
+		err = xb_write(base + state.written, len - state.written);
+		if (err < 0)
+			goto out_err;
+		state.written += err;
+		if (state.written != len)
+			goto out;
+
+		state.idx++;
+		state.written = 0;
+	}
+
+	list_del(&state.req->list);
+	state.req->state = xb_req_state_wait_reply;
+	list_add_tail(&state.req->list, &xs_reply_list);
+	state.req = NULL;
+
+ out:
+	mutex_unlock(&xb_write_mutex);
+
+	return 0;
+
+ out_err:
+	state.req->msg.type = XS_ERROR;
+	state.req->err = err;
+	list_del(&state.req->list);
+	if (state.req->state != xb_req_state_aborted) {
+		/* write err, then update state */
+		virt_wmb();
+		state.req->state = xb_req_state_got_reply;
+		wake_up(&state.req->wq);
+	}
+	kref_put(&state.req->kref, xs_free_req);
+
+	mutex_unlock(&xb_write_mutex);
+
+	state.req = NULL;
+
+	return err;
+}
+
+static int xb_thread_work(void)
+{
+	return xb_data_to_read() || xb_data_to_write();
+}
+
+static int xenbus_thread(void *unused)
+{
+	int err;
+
+	while (!kthread_should_stop()) {
+		if (wait_event_interruptible(xb_waitq, xb_thread_work()))
+			continue;
+
+		err = process_msg();
+		if (err == -ENOMEM)
+			schedule();
+		else if (err)
+			pr_warn_ratelimited("error %d while reading message\n",
+					    err);
+
+		err = process_writes();
+		if (err)
+			pr_warn_ratelimited("error %d while writing message\n",
+					    err);
+	}
+
+	xenbus_task = NULL;
+	return 0;
+}
+
+/**
+ * xb_init_comms - Set up interrupt handler off store event channel.
+ */
+int xb_init_comms(void)
+{
+	struct xenstore_domain_interface *intf = xen_store_interface;
+
+	if (intf->req_prod != intf->req_cons)
+		pr_err("request ring is not quiescent (%08x:%08x)!\n",
+		       intf->req_cons, intf->req_prod);
+
+	if (intf->rsp_prod != intf->rsp_cons) {
+		pr_warn("response ring is not quiescent (%08x:%08x): fixing up\n",
+			intf->rsp_cons, intf->rsp_prod);
+		/* breaks kdump */
+		if (!reset_devices)
+			intf->rsp_cons = intf->rsp_prod;
+	}
+
+	if (xenbus_irq) {
+		/* Already have an irq; assume we're resuming */
+		rebind_evtchn_irq(xen_store_evtchn, xenbus_irq);
+	} else {
+		int err;
+
+		err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting,
+						0, "xenbus", &xb_waitq);
+		if (err < 0) {
+			pr_err("request irq failed %i\n", err);
+			return err;
+		}
+
+		xenbus_irq = err;
+
+		if (!xenbus_task) {
+			xenbus_task = kthread_run(xenbus_thread, NULL,
+						  "xenbus");
+			if (IS_ERR(xenbus_task))
+				return PTR_ERR(xenbus_task);
+		}
+	}
+
+	return 0;
+}
+
+void xb_deinit_comms(void)
+{
+	unbind_from_irqhandler(xenbus_irq, &xb_waitq);
+	xenbus_irq = 0;
+}
diff --git a/drivers/xen/xenbus/xenbus_dev_backend.c b/drivers/xen/xenbus/xenbus_dev_backend.c
new file mode 100644
index 000000000..edba5fecd
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus_dev_backend.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/init.h>
+#include <linux/capability.h>
+
+#include <xen/xen.h>
+#include <xen/page.h>
+#include <xen/xenbus.h>
+#include <xen/xenbus_dev.h>
+#include <xen/grant_table.h>
+#include <xen/events.h>
+#include <asm/xen/hypervisor.h>
+
+#include "xenbus.h"
+
+static int xenbus_backend_open(struct inode *inode, struct file *filp)
+{
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	return nonseekable_open(inode, filp);
+}
+
+static long xenbus_alloc(domid_t domid)
+{
+	struct evtchn_alloc_unbound arg;
+	int err = -EEXIST;
+
+	xs_suspend();
+
+	/* If xenstored_ready is nonzero, that means we have already talked to
+	 * xenstore and set up watches. These watches will be restored by
+	 * xs_resume, but that requires communication over the port established
+	 * below that is not visible to anyone until the ioctl returns.
+	 *
+	 * This can be resolved by splitting the ioctl into two parts
+	 * (postponing the resume until xenstored is active) but this is
+	 * unnecessarily complex for the intended use where xenstored is only
+	 * started once - so return -EEXIST if it's already running.
+	 */
+	if (xenstored_ready)
+		goto out_err;
+
+	gnttab_grant_foreign_access_ref(GNTTAB_RESERVED_XENSTORE, domid,
+			virt_to_gfn(xen_store_interface), 0 /* writable */);
+
+	arg.dom = DOMID_SELF;
+	arg.remote_dom = domid;
+
+	err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound, &arg);
+	if (err)
+		goto out_err;
+
+	if (xen_store_evtchn > 0)
+		xb_deinit_comms();
+
+	xen_store_evtchn = arg.port;
+
+	xs_resume();
+
+	return arg.port;
+
+ out_err:
+	xs_suspend_cancel();
+	return err;
+}
+
+static long xenbus_backend_ioctl(struct file *file, unsigned int cmd,
+				 unsigned long data)
+{
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	switch (cmd) {
+	case IOCTL_XENBUS_BACKEND_EVTCHN:
+		if (xen_store_evtchn > 0)
+			return xen_store_evtchn;
+		return -ENODEV;
+	case IOCTL_XENBUS_BACKEND_SETUP:
+		return xenbus_alloc(data);
+	default:
+		return -ENOTTY;
+	}
+}
+
+static int xenbus_backend_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	size_t size = vma->vm_end - vma->vm_start;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if ((size > PAGE_SIZE) || (vma->vm_pgoff != 0))
+		return -EINVAL;
+
+	if (remap_pfn_range(vma, vma->vm_start,
+			    virt_to_pfn(xen_store_interface),
+			    size, vma->vm_page_prot))
+		return -EAGAIN;
+
+	return 0;
+}
+
+static const struct file_operations xenbus_backend_fops = {
+	.open = xenbus_backend_open,
+	.mmap = xenbus_backend_mmap,
+	.unlocked_ioctl = xenbus_backend_ioctl,
+};
+
+static struct miscdevice xenbus_backend_dev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "xen/xenbus_backend",
+	.fops = &xenbus_backend_fops,
+};
+
+static int __init xenbus_backend_init(void)
+{
+	int err;
+
+	if (!xen_initial_domain())
+		return -ENODEV;
+
+	err = misc_register(&xenbus_backend_dev);
+	if (err)
+		pr_err("Could not register xenbus backend device\n");
+	return err;
+}
+device_initcall(xenbus_backend_init);
diff --git a/drivers/xen/xenbus/xenbus_dev_frontend.c b/drivers/xen/xenbus/xenbus_dev_frontend.c
new file mode 100644
index 000000000..61db6932a
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
@@ -0,0 +1,724 @@
+/*
+ * Driver giving user-space access to the kernel's xenbus connection
+ * to xenstore.
+ *
+ * Copyright (c) 2005, Christian Limpach
+ * Copyright (c) 2005, Rusty Russell, IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Changes:
+ * 2008-10-07  Alex Zeffertt    Replaced /proc/xen/xenbus with xenfs filesystem
+ *                              and /proc/xen compatibility mount point.
+ *                              Turned xenfs into a loadable module.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/uio.h>
+#include <linux/notifier.h>
+#include <linux/wait.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/mount.h>
+#include <linux/pagemap.h>
+#include <linux/uaccess.h>
+#include <linux/init.h>
+#include <linux/namei.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/miscdevice.h>
+#include <linux/workqueue.h>
+
+#include <xen/xenbus.h>
+#include <xen/xen.h>
+#include <asm/xen/hypervisor.h>
+
+#include "xenbus.h"
+
+unsigned int xb_dev_generation_id;
+
+/*
+ * An element of a list of outstanding transactions, for which we're
+ * still waiting a reply.
+ */
+struct xenbus_transaction_holder {
+	struct list_head list;
+	struct xenbus_transaction handle;
+	unsigned int generation_id;
+};
+
+/*
+ * A buffer of data on the queue.
+ */
+struct read_buffer {
+	struct list_head list;
+	unsigned int cons;
+	unsigned int len;
+	char msg[] __counted_by(len);
+};
+
+struct xenbus_file_priv {
+	/*
+	 * msgbuffer_mutex is held while partial requests are built up
+	 * and complete requests are acted on.  It therefore protects
+	 * the "transactions" and "watches" lists, and the partial
+	 * request length and buffer.
+	 *
+	 * reply_mutex protects the reply being built up to return to
+	 * usermode.  It nests inside msgbuffer_mutex but may be held
+	 * alone during a watch callback.
+	 */
+	struct mutex msgbuffer_mutex;
+
+	/* In-progress transactions */
+	struct list_head transactions;
+
+	/* Active watches. */
+	struct list_head watches;
+
+	/* Partial request. */
+	unsigned int len;
+	union {
+		struct xsd_sockmsg msg;
+		char buffer[XENSTORE_PAYLOAD_MAX];
+	} u;
+
+	/* Response queue. */
+	struct mutex reply_mutex;
+	struct list_head read_buffers;
+	wait_queue_head_t read_waitq;
+
+	struct kref kref;
+
+	struct work_struct wq;
+};
+
+/* Read out any raw xenbus messages queued up. */
+static ssize_t xenbus_file_read(struct file *filp,
+			       char __user *ubuf,
+			       size_t len, loff_t *ppos)
+{
+	struct xenbus_file_priv *u = filp->private_data;
+	struct read_buffer *rb;
+	ssize_t i;
+	int ret;
+
+	mutex_lock(&u->reply_mutex);
+again:
+	while (list_empty(&u->read_buffers)) {
+		mutex_unlock(&u->reply_mutex);
+		if (filp->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+
+		ret = wait_event_interruptible(u->read_waitq,
+					       !list_empty(&u->read_buffers));
+		if (ret)
+			return ret;
+		mutex_lock(&u->reply_mutex);
+	}
+
+	rb = list_entry(u->read_buffers.next, struct read_buffer, list);
+	i = 0;
+	while (i < len) {
+		size_t sz = min_t(size_t, len - i, rb->len - rb->cons);
+
+		ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
+
+		i += sz - ret;
+		rb->cons += sz - ret;
+
+		if (ret != 0) {
+			if (i == 0)
+				i = -EFAULT;
+			goto out;
+		}
+
+		/* Clear out buffer if it has been consumed */
+		if (rb->cons == rb->len) {
+			list_del(&rb->list);
+			kfree(rb);
+			if (list_empty(&u->read_buffers))
+				break;
+			rb = list_entry(u->read_buffers.next,
+					struct read_buffer, list);
+		}
+	}
+	if (i == 0)
+		goto again;
+
+out:
+	mutex_unlock(&u->reply_mutex);
+	return i;
+}
+
+/*
+ * Add a buffer to the queue.  Caller must hold the appropriate lock
+ * if the queue is not local.  (Commonly the caller will build up
+ * multiple queued buffers on a temporary local list, and then add it
+ * to the appropriate list under lock once all the buffers have een
+ * successfully allocated.)
+ */
+static int queue_reply(struct list_head *queue, const void *data, size_t len)
+{
+	struct read_buffer *rb;
+
+	if (len == 0)
+		return 0;
+	if (len > XENSTORE_PAYLOAD_MAX)
+		return -EINVAL;
+
+	rb = kmalloc_flex(*rb, msg, len);
+	if (rb == NULL)
+		return -ENOMEM;
+
+	rb->cons = 0;
+	rb->len = len;
+
+	memcpy(rb->msg, data, len);
+
+	list_add_tail(&rb->list, queue);
+	return 0;
+}
+
+/*
+ * Free all the read_buffer s on a list.
+ * Caller must have sole reference to list.
+ */
+static void queue_cleanup(struct list_head *list)
+{
+	struct read_buffer *rb;
+
+	while (!list_empty(list)) {
+		rb = list_entry(list->next, struct read_buffer, list);
+		list_del(list->next);
+		kfree(rb);
+	}
+}
+
+struct watch_adapter {
+	struct list_head list;
+	struct xenbus_watch watch;
+	struct xenbus_file_priv *dev_data;
+	char *token;
+};
+
+static void free_watch_adapter(struct watch_adapter *watch)
+{
+	kfree(watch->watch.node);
+	kfree(watch->token);
+	kfree(watch);
+}
+
+static struct watch_adapter *alloc_watch_adapter(const char *path,
+						 const char *token)
+{
+	struct watch_adapter *watch;
+
+	watch = kzalloc_obj(*watch);
+	if (watch == NULL)
+		goto out_fail;
+
+	watch->watch.node = kstrdup(path, GFP_KERNEL);
+	if (watch->watch.node == NULL)
+		goto out_free;
+
+	watch->token = kstrdup(token, GFP_KERNEL);
+	if (watch->token == NULL)
+		goto out_free;
+
+	return watch;
+
+out_free:
+	free_watch_adapter(watch);
+
+out_fail:
+	return NULL;
+}
+
+static void watch_fired(struct xenbus_watch *watch,
+			const char *path,
+			const char *token)
+{
+	struct watch_adapter *adap;
+	struct xsd_sockmsg hdr;
+	const char *token_caller;
+	int path_len, tok_len, body_len;
+	int ret;
+	LIST_HEAD(staging_q);
+
+	adap = container_of(watch, struct watch_adapter, watch);
+
+	token_caller = adap->token;
+
+	path_len = strlen(path) + 1;
+	tok_len = strlen(token_caller) + 1;
+	body_len = path_len + tok_len;
+
+	hdr.type = XS_WATCH_EVENT;
+	hdr.len = body_len;
+
+	mutex_lock(&adap->dev_data->reply_mutex);
+
+	ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
+	if (!ret)
+		ret = queue_reply(&staging_q, path, path_len);
+	if (!ret)
+		ret = queue_reply(&staging_q, token_caller, tok_len);
+
+	if (!ret) {
+		/* success: pass reply list onto watcher */
+		list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
+		wake_up(&adap->dev_data->read_waitq);
+	} else
+		queue_cleanup(&staging_q);
+
+	mutex_unlock(&adap->dev_data->reply_mutex);
+}
+
+static void xenbus_worker(struct work_struct *wq)
+{
+	struct xenbus_file_priv *u;
+	struct xenbus_transaction_holder *trans, *tmp;
+	struct watch_adapter *watch, *tmp_watch;
+	struct read_buffer *rb, *tmp_rb;
+
+	u = container_of(wq, struct xenbus_file_priv, wq);
+
+	/*
+	 * No need for locking here because there are no other users,
+	 * by definition.
+	 */
+
+	list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
+		xenbus_transaction_end(trans->handle, 1);
+		list_del(&trans->list);
+		kfree(trans);
+	}
+
+	list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
+		unregister_xenbus_watch(&watch->watch);
+		list_del(&watch->list);
+		free_watch_adapter(watch);
+	}
+
+	list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) {
+		list_del(&rb->list);
+		kfree(rb);
+	}
+	kfree(u);
+}
+
+static void xenbus_file_free(struct kref *kref)
+{
+	struct xenbus_file_priv *u;
+
+	/*
+	 * We might be called in xenbus_thread().
+	 * Use workqueue to avoid deadlock.
+	 */
+	u = container_of(kref, struct xenbus_file_priv, kref);
+	schedule_work(&u->wq);
+}
+
+static struct xenbus_transaction_holder *xenbus_get_transaction(
+	struct xenbus_file_priv *u, uint32_t tx_id)
+{
+	struct xenbus_transaction_holder *trans;
+
+	list_for_each_entry(trans, &u->transactions, list)
+		if (trans->handle.id == tx_id)
+			return trans;
+
+	return NULL;
+}
+
+void xenbus_dev_queue_reply(struct xb_req_data *req)
+{
+	struct xenbus_file_priv *u = req->par;
+	struct xenbus_transaction_holder *trans = NULL;
+	int rc;
+	LIST_HEAD(staging_q);
+
+	xs_request_exit(req);
+
+	mutex_lock(&u->msgbuffer_mutex);
+
+	if (req->type == XS_TRANSACTION_START) {
+		trans = xenbus_get_transaction(u, 0);
+		if (WARN_ON(!trans))
+			goto out;
+		if (req->msg.type == XS_ERROR) {
+			list_del(&trans->list);
+			kfree(trans);
+		} else {
+			rc = kstrtou32(req->body, 10, &trans->handle.id);
+			if (WARN_ON(rc))
+				goto out;
+		}
+	} else if (req->type == XS_TRANSACTION_END) {
+		trans = xenbus_get_transaction(u, req->msg.tx_id);
+		if (WARN_ON(!trans))
+			goto out;
+		list_del(&trans->list);
+		kfree(trans);
+	}
+
+	mutex_unlock(&u->msgbuffer_mutex);
+
+	mutex_lock(&u->reply_mutex);
+	rc = queue_reply(&staging_q, &req->msg, sizeof(req->msg));
+	if (!rc)
+		rc = queue_reply(&staging_q, req->body, req->msg.len);
+	if (!rc) {
+		list_splice_tail(&staging_q, &u->read_buffers);
+		wake_up(&u->read_waitq);
+	} else {
+		queue_cleanup(&staging_q);
+	}
+	mutex_unlock(&u->reply_mutex);
+
+	kfree(req->body);
+	kref_put(&req->kref, xs_free_req);
+
+	kref_put(&u->kref, xenbus_file_free);
+
+	return;
+
+ out:
+	mutex_unlock(&u->msgbuffer_mutex);
+}
+
+static int xenbus_command_reply(struct xenbus_file_priv *u,
+				unsigned int msg_type, const char *reply)
+{
+	struct {
+		struct xsd_sockmsg hdr;
+		char body[16];
+	} msg;
+	int rc;
+
+	msg.hdr = u->u.msg;
+	msg.hdr.type = msg_type;
+	msg.hdr.len = strlen(reply) + 1;
+	if (msg.hdr.len > sizeof(msg.body))
+		return -E2BIG;
+	memcpy(&msg.body, reply, msg.hdr.len);
+
+	mutex_lock(&u->reply_mutex);
+	rc = queue_reply(&u->read_buffers, &msg, sizeof(msg.hdr) + msg.hdr.len);
+	wake_up(&u->read_waitq);
+	mutex_unlock(&u->reply_mutex);
+
+	if (!rc)
+		kref_put(&u->kref, xenbus_file_free);
+
+	return rc;
+}
+
+static int xenbus_write_transaction(unsigned msg_type,
+				    struct xenbus_file_priv *u)
+{
+	int rc;
+	struct xenbus_transaction_holder *trans = NULL;
+	struct {
+		struct xsd_sockmsg hdr;
+		char body[];
+	} *msg = (void *)u->u.buffer;
+
+	if (msg_type == XS_TRANSACTION_START) {
+		trans = kzalloc_obj(*trans);
+		if (!trans) {
+			rc = -ENOMEM;
+			goto out;
+		}
+		trans->generation_id = xb_dev_generation_id;
+		list_add(&trans->list, &u->transactions);
+	} else if (msg->hdr.tx_id != 0 &&
+		   !xenbus_get_transaction(u, msg->hdr.tx_id))
+		return xenbus_command_reply(u, XS_ERROR, "ENOENT");
+	else if (msg_type == XS_TRANSACTION_END &&
+		 !(msg->hdr.len == 2 &&
+		   (!strcmp(msg->body, "T") || !strcmp(msg->body, "F"))))
+		return xenbus_command_reply(u, XS_ERROR, "EINVAL");
+	else if (msg_type == XS_TRANSACTION_END) {
+		trans = xenbus_get_transaction(u, msg->hdr.tx_id);
+		if (trans && trans->generation_id != xb_dev_generation_id) {
+			list_del(&trans->list);
+			kfree(trans);
+			if (!strcmp(msg->body, "T"))
+				return xenbus_command_reply(u, XS_ERROR,
+							    "EAGAIN");
+			else
+				return xenbus_command_reply(u,
+							    XS_TRANSACTION_END,
+							    "OK");
+		}
+	}
+
+	rc = xenbus_dev_request_and_reply(&msg->hdr, u);
+	if (rc && trans) {
+		list_del(&trans->list);
+		kfree(trans);
+	}
+
+out:
+	return rc;
+}
+
+static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
+{
+	struct watch_adapter *watch;
+	char *path, *token;
+	int err, rc;
+
+	path = u->u.buffer + sizeof(u->u.msg);
+	token = memchr(path, 0, u->u.msg.len);
+	if (token == NULL) {
+		rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
+		goto out;
+	}
+	token++;
+	if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
+		rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
+		goto out;
+	}
+
+	if (msg_type == XS_WATCH) {
+		watch = alloc_watch_adapter(path, token);
+		if (watch == NULL) {
+			rc = -ENOMEM;
+			goto out;
+		}
+
+		watch->watch.callback = watch_fired;
+		watch->dev_data = u;
+
+		err = register_xenbus_watch(&watch->watch);
+		if (err) {
+			free_watch_adapter(watch);
+			rc = err;
+			goto out;
+		}
+		list_add(&watch->list, &u->watches);
+	} else {
+		list_for_each_entry(watch, &u->watches, list) {
+			if (!strcmp(watch->token, token) &&
+			    !strcmp(watch->watch.node, path)) {
+				unregister_xenbus_watch(&watch->watch);
+				list_del(&watch->list);
+				free_watch_adapter(watch);
+				break;
+			}
+		}
+	}
+
+	/* Success.  Synthesize a reply to say all is OK. */
+	rc = xenbus_command_reply(u, msg_type, "OK");
+
+out:
+	return rc;
+}
+
+static ssize_t xenbus_file_write(struct file *filp,
+				const char __user *ubuf,
+				size_t len, loff_t *ppos)
+{
+	struct xenbus_file_priv *u = filp->private_data;
+	uint32_t msg_type;
+	int rc = len;
+	int ret;
+
+	/*
+	 * We're expecting usermode to be writing properly formed
+	 * xenbus messages.  If they write an incomplete message we
+	 * buffer it up.  Once it is complete, we act on it.
+	 */
+
+	/*
+	 * Make sure concurrent writers can't stomp all over each
+	 * other's messages and make a mess of our partial message
+	 * buffer.  We don't make any attemppt to stop multiple
+	 * writers from making a mess of each other's incomplete
+	 * messages; we're just trying to guarantee our own internal
+	 * consistency and make sure that single writes are handled
+	 * atomically.
+	 */
+	mutex_lock(&u->msgbuffer_mutex);
+
+	/* Get this out of the way early to avoid confusion */
+	if (len == 0)
+		goto out;
+
+	/* Can't write a xenbus message larger we can buffer */
+	if (len > sizeof(u->u.buffer) - u->len) {
+		/* On error, dump existing buffer */
+		u->len = 0;
+		rc = -EINVAL;
+		goto out;
+	}
+
+	ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
+
+	if (ret != 0) {
+		rc = -EFAULT;
+		goto out;
+	}
+
+	/* Deal with a partial copy. */
+	len -= ret;
+	rc = len;
+
+	u->len += len;
+
+	/* Return if we haven't got a full message yet */
+	if (u->len < sizeof(u->u.msg))
+		goto out;	/* not even the header yet */
+
+	/* If we're expecting a message that's larger than we can
+	   possibly send, dump what we have and return an error. */
+	if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
+		rc = -E2BIG;
+		u->len = 0;
+		goto out;
+	}
+
+	if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
+		goto out;	/* incomplete data portion */
+
+	/*
+	 * OK, now we have a complete message.  Do something with it.
+	 */
+
+	kref_get(&u->kref);
+
+	msg_type = u->u.msg.type;
+
+	switch (msg_type) {
+	case XS_WATCH:
+	case XS_UNWATCH:
+		/* (Un)Ask for some path to be watched for changes */
+		ret = xenbus_write_watch(msg_type, u);
+		break;
+
+	default:
+		/* Send out a transaction */
+		ret = xenbus_write_transaction(msg_type, u);
+		break;
+	}
+	if (ret != 0) {
+		rc = ret;
+		kref_put(&u->kref, xenbus_file_free);
+	}
+
+	/* Buffered message consumed */
+	u->len = 0;
+
+ out:
+	mutex_unlock(&u->msgbuffer_mutex);
+	return rc;
+}
+
+static int xenbus_file_open(struct inode *inode, struct file *filp)
+{
+	struct xenbus_file_priv *u;
+
+	if (xen_store_evtchn == 0)
+		return -ENOENT;
+
+	stream_open(inode, filp);
+
+	u = kzalloc_obj(*u);
+	if (u == NULL)
+		return -ENOMEM;
+
+	kref_init(&u->kref);
+
+	INIT_LIST_HEAD(&u->transactions);
+	INIT_LIST_HEAD(&u->watches);
+	INIT_LIST_HEAD(&u->read_buffers);
+	init_waitqueue_head(&u->read_waitq);
+	INIT_WORK(&u->wq, xenbus_worker);
+
+	mutex_init(&u->reply_mutex);
+	mutex_init(&u->msgbuffer_mutex);
+
+	filp->private_data = u;
+
+	return 0;
+}
+
+static int xenbus_file_release(struct inode *inode, struct file *filp)
+{
+	struct xenbus_file_priv *u = filp->private_data;
+
+	kref_put(&u->kref, xenbus_file_free);
+
+	return 0;
+}
+
+static __poll_t xenbus_file_poll(struct file *file, poll_table *wait)
+{
+	struct xenbus_file_priv *u = file->private_data;
+
+	poll_wait(file, &u->read_waitq, wait);
+	if (!list_empty(&u->read_buffers))
+		return EPOLLIN | EPOLLRDNORM;
+	return 0;
+}
+
+const struct file_operations xen_xenbus_fops = {
+	.read = xenbus_file_read,
+	.write = xenbus_file_write,
+	.open = xenbus_file_open,
+	.release = xenbus_file_release,
+	.poll = xenbus_file_poll,
+};
+EXPORT_SYMBOL_GPL(xen_xenbus_fops);
+
+static struct miscdevice xenbus_dev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "xen/xenbus",
+	.fops = &xen_xenbus_fops,
+};
+
+static int __init xenbus_init(void)
+{
+	int err;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	err = misc_register(&xenbus_dev);
+	if (err)
+		pr_err("Could not register xenbus frontend device\n");
+	return err;
+}
+device_initcall(xenbus_init);
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
new file mode 100644
index 000000000..9a8c83326
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -0,0 +1,1129 @@
+/******************************************************************************
+ * Talks to Xen Store to figure out what devices we have.
+ *
+ * Copyright (C) 2005 Rusty Russell, IBM Corporation
+ * Copyright (C) 2005 Mike Wray, Hewlett-Packard
+ * Copyright (C) 2005, 2006 XenSource Ltd
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#define dev_fmt pr_fmt
+
+#define DPRINTK(fmt, args...)				\
+	pr_debug("xenbus_probe (%s:%d) " fmt ".\n",	\
+		 __func__, __LINE__, ##args)
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/string.h>
+#include <linux/ctype.h>
+#include <linux/fcntl.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/notifier.h>
+#include <linux/kthread.h>
+#include <linux/mutex.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#include <asm/page.h>
+#include <asm/xen/hypervisor.h>
+
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/events.h>
+#include <xen/xen-ops.h>
+#include <xen/page.h>
+
+#include <xen/hvm.h>
+
+#include "xenbus.h"
+
+
+static int xs_init_irq = -1;
+int xen_store_evtchn;
+EXPORT_SYMBOL_GPL(xen_store_evtchn);
+
+struct xenstore_domain_interface *xen_store_interface;
+EXPORT_SYMBOL_GPL(xen_store_interface);
+
+#define XS_INTERFACE_READY \
+	((xen_store_interface != NULL) && \
+	 (xen_store_interface->connection == XENSTORE_CONNECTED))
+
+enum xenstore_init xen_store_domain_type;
+EXPORT_SYMBOL_GPL(xen_store_domain_type);
+
+static unsigned long xen_store_gfn;
+
+static BLOCKING_NOTIFIER_HEAD(xenstore_chain);
+
+/* If something in array of ids matches this device, return it. */
+static const struct xenbus_device_id *
+match_device(const struct xenbus_device_id *arr, struct xenbus_device *dev)
+{
+	for (; *arr->devicetype != '\0'; arr++) {
+		if (!strcmp(arr->devicetype, dev->devicetype))
+			return arr;
+	}
+	return NULL;
+}
+
+int xenbus_match(struct device *_dev, const struct device_driver *_drv)
+{
+	const struct xenbus_driver *drv = to_xenbus_driver(_drv);
+
+	if (!drv->ids)
+		return 0;
+
+	return match_device(drv->ids, to_xenbus_device(_dev)) != NULL;
+}
+EXPORT_SYMBOL_GPL(xenbus_match);
+
+
+static void free_otherend_details(struct xenbus_device *dev)
+{
+	kfree(dev->otherend);
+	dev->otherend = NULL;
+}
+
+
+static void free_otherend_watch(struct xenbus_device *dev)
+{
+	if (dev->otherend_watch.node) {
+		unregister_xenbus_watch(&dev->otherend_watch);
+		kfree(dev->otherend_watch.node);
+		dev->otherend_watch.node = NULL;
+	}
+}
+
+
+static int talk_to_otherend(struct xenbus_device *dev)
+{
+	struct xenbus_driver *drv = to_xenbus_driver(dev->dev.driver);
+
+	free_otherend_watch(dev);
+	free_otherend_details(dev);
+
+	return drv->read_otherend_details(dev);
+}
+
+
+
+static int watch_otherend(struct xenbus_device *dev)
+{
+	struct xen_bus_type *bus =
+		container_of(dev->dev.bus, struct xen_bus_type, bus);
+
+	return xenbus_watch_pathfmt(dev, &dev->otherend_watch,
+				    bus->otherend_will_handle,
+				    bus->otherend_changed,
+				    "%s/%s", dev->otherend, "state");
+}
+
+
+int xenbus_read_otherend_details(struct xenbus_device *xendev,
+				 char *id_node, char *path_node)
+{
+	int err = xenbus_gather(XBT_NIL, xendev->nodename,
+				id_node, "%i", &xendev->otherend_id,
+				path_node, NULL, &xendev->otherend,
+				NULL);
+	if (err) {
+		xenbus_dev_fatal(xendev, err,
+				 "reading other end details from %s",
+				 xendev->nodename);
+		return err;
+	}
+	if (strlen(xendev->otherend) == 0 ||
+	    !xenbus_exists(XBT_NIL, xendev->otherend, "")) {
+		xenbus_dev_fatal(xendev, -ENOENT,
+				 "unable to read other end from %s.  "
+				 "missing or inaccessible.",
+				 xendev->nodename);
+		free_otherend_details(xendev);
+		return -ENOENT;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xenbus_read_otherend_details);
+
+void xenbus_otherend_changed(struct xenbus_watch *watch,
+			     const char *path, const char *token,
+			     int ignore_on_shutdown)
+{
+	struct xenbus_device *dev =
+		container_of(watch, struct xenbus_device, otherend_watch);
+	struct xenbus_driver *drv = to_xenbus_driver(dev->dev.driver);
+	enum xenbus_state state;
+
+	/* Protect us against watches firing on old details when the otherend
+	   details change, say immediately after a resume. */
+	if (!dev->otherend ||
+	    strncmp(dev->otherend, path, strlen(dev->otherend))) {
+		dev_dbg(&dev->dev, "Ignoring watch at %s\n", path);
+		return;
+	}
+
+	state = xenbus_read_driver_state(dev, dev->otherend);
+
+	dev_dbg(&dev->dev, "state is %d, (%s), %s, %s\n",
+		state, xenbus_strstate(state), dev->otherend_watch.node, path);
+
+	/*
+	 * Ignore xenbus transitions during shutdown. This prevents us doing
+	 * work that can fail e.g., when the rootfs is gone.
+	 */
+	if (system_state > SYSTEM_RUNNING) {
+		if (ignore_on_shutdown && (state == XenbusStateClosing))
+			xenbus_frontend_closed(dev);
+		return;
+	}
+
+	if (drv->otherend_changed)
+		drv->otherend_changed(dev, state);
+}
+EXPORT_SYMBOL_GPL(xenbus_otherend_changed);
+
+#define XENBUS_SHOW_STAT(name)						\
+static ssize_t name##_show(struct device *_dev,				\
+			   struct device_attribute *attr,		\
+			   char *buf)					\
+{									\
+	struct xenbus_device *dev = to_xenbus_device(_dev);		\
+									\
+	return sprintf(buf, "%d\n", atomic_read(&dev->name));		\
+}									\
+static DEVICE_ATTR_RO(name)
+
+XENBUS_SHOW_STAT(event_channels);
+XENBUS_SHOW_STAT(events);
+XENBUS_SHOW_STAT(spurious_events);
+XENBUS_SHOW_STAT(jiffies_eoi_delayed);
+
+static ssize_t spurious_threshold_show(struct device *_dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct xenbus_device *dev = to_xenbus_device(_dev);
+
+	return sprintf(buf, "%d\n", dev->spurious_threshold);
+}
+
+static ssize_t spurious_threshold_store(struct device *_dev,
+					struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct xenbus_device *dev = to_xenbus_device(_dev);
+	unsigned int val;
+	ssize_t ret;
+
+	ret = kstrtouint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	dev->spurious_threshold = val;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(spurious_threshold);
+
+static struct attribute *xenbus_attrs[] = {
+	&dev_attr_event_channels.attr,
+	&dev_attr_events.attr,
+	&dev_attr_spurious_events.attr,
+	&dev_attr_jiffies_eoi_delayed.attr,
+	&dev_attr_spurious_threshold.attr,
+	NULL
+};
+
+static const struct attribute_group xenbus_group = {
+	.name = "xenbus",
+	.attrs = xenbus_attrs,
+};
+
+int xenbus_dev_probe(struct device *_dev)
+{
+	struct xenbus_device *dev = to_xenbus_device(_dev);
+	struct xenbus_driver *drv = to_xenbus_driver(_dev->driver);
+	const struct xenbus_device_id *id;
+	int err;
+
+	DPRINTK("%s", dev->nodename);
+
+	if (!drv->probe) {
+		err = -ENODEV;
+		goto fail;
+	}
+
+	id = match_device(drv->ids, dev);
+	if (!id) {
+		err = -ENODEV;
+		goto fail;
+	}
+
+	err = talk_to_otherend(dev);
+	if (err) {
+		dev_warn(&dev->dev, "talk_to_otherend on %s failed.\n",
+			 dev->nodename);
+		return err;
+	}
+
+	if (!try_module_get(drv->driver.owner)) {
+		dev_warn(&dev->dev, "failed to acquire module reference on '%s'\n",
+			 drv->driver.name);
+		err = -ESRCH;
+		goto fail;
+	}
+
+	down(&dev->reclaim_sem);
+	err = drv->probe(dev, id);
+	up(&dev->reclaim_sem);
+	if (err)
+		goto fail_put;
+
+	err = watch_otherend(dev);
+	if (err) {
+		dev_warn(&dev->dev, "watch_otherend on %s failed.\n",
+		       dev->nodename);
+		goto fail_remove;
+	}
+
+	dev->spurious_threshold = 1;
+	if (sysfs_create_group(&dev->dev.kobj, &xenbus_group))
+		dev_warn(&dev->dev, "sysfs_create_group on %s failed.\n",
+			 dev->nodename);
+
+	return 0;
+fail_remove:
+	if (drv->remove) {
+		down(&dev->reclaim_sem);
+		drv->remove(dev);
+		up(&dev->reclaim_sem);
+	}
+fail_put:
+	module_put(drv->driver.owner);
+fail:
+	xenbus_dev_error(dev, err, "xenbus_dev_probe on %s", dev->nodename);
+	return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_probe);
+
+void xenbus_dev_remove(struct device *_dev)
+{
+	struct xenbus_device *dev = to_xenbus_device(_dev);
+	struct xenbus_driver *drv = to_xenbus_driver(_dev->driver);
+
+	DPRINTK("%s", dev->nodename);
+
+	sysfs_remove_group(&dev->dev.kobj, &xenbus_group);
+
+	free_otherend_watch(dev);
+
+	if (drv->remove) {
+		down(&dev->reclaim_sem);
+		drv->remove(dev);
+		up(&dev->reclaim_sem);
+	}
+
+	module_put(drv->driver.owner);
+
+	free_otherend_details(dev);
+
+	/*
+	 * If the toolstack has forced the device state to closing then set
+	 * the state to closed now to allow it to be cleaned up.
+	 * Similarly, if the driver does not support re-bind, set the
+	 * closed.
+	 */
+	if (!drv->allow_rebind ||
+	    xenbus_read_driver_state(dev, dev->nodename) == XenbusStateClosing)
+		xenbus_switch_state(dev, XenbusStateClosed);
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_remove);
+
+int xenbus_register_driver_common(struct xenbus_driver *drv,
+				  struct xen_bus_type *bus,
+				  struct module *owner, const char *mod_name)
+{
+	drv->driver.name = drv->name ? drv->name : drv->ids[0].devicetype;
+	drv->driver.bus = &bus->bus;
+	drv->driver.owner = owner;
+	drv->driver.mod_name = mod_name;
+
+	return driver_register(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(xenbus_register_driver_common);
+
+void xenbus_unregister_driver(struct xenbus_driver *drv)
+{
+	driver_unregister(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(xenbus_unregister_driver);
+
+struct xb_find_info {
+	struct xenbus_device *dev;
+	const char *nodename;
+};
+
+static int cmp_dev(struct device *dev, void *data)
+{
+	struct xenbus_device *xendev = to_xenbus_device(dev);
+	struct xb_find_info *info = data;
+
+	if (!strcmp(xendev->nodename, info->nodename)) {
+		info->dev = xendev;
+		get_device(dev);
+		return 1;
+	}
+	return 0;
+}
+
+static struct xenbus_device *xenbus_device_find(const char *nodename,
+						struct bus_type *bus)
+{
+	struct xb_find_info info = { .dev = NULL, .nodename = nodename };
+
+	bus_for_each_dev(bus, NULL, &info, cmp_dev);
+	return info.dev;
+}
+
+static int cleanup_dev(struct device *dev, void *data)
+{
+	struct xenbus_device *xendev = to_xenbus_device(dev);
+	struct xb_find_info *info = data;
+	int len = strlen(info->nodename);
+
+	DPRINTK("%s", info->nodename);
+
+	/* Match the info->nodename path, or any subdirectory of that path. */
+	if (strncmp(xendev->nodename, info->nodename, len))
+		return 0;
+
+	/* If the node name is longer, ensure it really is a subdirectory. */
+	if ((strlen(xendev->nodename) > len) && (xendev->nodename[len] != '/'))
+		return 0;
+
+	info->dev = xendev;
+	get_device(dev);
+	return 1;
+}
+
+static void xenbus_cleanup_devices(const char *path, struct bus_type *bus)
+{
+	struct xb_find_info info = { .nodename = path };
+
+	do {
+		info.dev = NULL;
+		bus_for_each_dev(bus, NULL, &info, cleanup_dev);
+		if (info.dev) {
+			dev_warn(&info.dev->dev,
+				 "device forcefully removed from xenstore\n");
+			info.dev->vanished = true;
+			device_unregister(&info.dev->dev);
+			put_device(&info.dev->dev);
+		}
+	} while (info.dev);
+}
+
+static void xenbus_dev_release(struct device *dev)
+{
+	if (dev)
+		kfree(to_xenbus_device(dev));
+}
+
+static ssize_t nodename_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s\n", to_xenbus_device(dev)->nodename);
+}
+static DEVICE_ATTR_RO(nodename);
+
+static ssize_t devtype_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s\n", to_xenbus_device(dev)->devicetype);
+}
+static DEVICE_ATTR_RO(devtype);
+
+static ssize_t modalias_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s:%s\n", dev->bus->name,
+		       to_xenbus_device(dev)->devicetype);
+}
+static DEVICE_ATTR_RO(modalias);
+
+static ssize_t state_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s\n",
+			xenbus_strstate(to_xenbus_device(dev)->state));
+}
+static DEVICE_ATTR_RO(state);
+
+static struct attribute *xenbus_dev_attrs[] = {
+	&dev_attr_nodename.attr,
+	&dev_attr_devtype.attr,
+	&dev_attr_modalias.attr,
+	&dev_attr_state.attr,
+	NULL,
+};
+
+static const struct attribute_group xenbus_dev_group = {
+	.attrs = xenbus_dev_attrs,
+};
+
+const struct attribute_group *xenbus_dev_groups[] = {
+	&xenbus_dev_group,
+	NULL,
+};
+EXPORT_SYMBOL_GPL(xenbus_dev_groups);
+
+int xenbus_probe_node(struct xen_bus_type *bus,
+		      const char *type,
+		      const char *nodename)
+{
+	char devname[XEN_BUS_ID_SIZE];
+	int err;
+	struct xenbus_device *xendev;
+	size_t name_len, type_len;
+	char *tmpstring;
+
+	enum xenbus_state state = xenbus_read_driver_state(NULL, nodename);
+
+	if (state != XenbusStateInitialising) {
+		/* Device is not new, so ignore it.  This can happen if a
+		   device is going away after switching to Closed.  */
+		return 0;
+	}
+
+	name_len = strlen(nodename);
+	type_len = strlen(type);
+	xendev = kzalloc(sizeof(*xendev) + name_len + 1 + type_len + 1, GFP_KERNEL);
+	if (!xendev)
+		return -ENOMEM;
+
+	xendev->state = XenbusStateInitialising;
+
+	/* Copy the strings into the extra space. */
+
+	tmpstring = (char *)(xendev + 1);
+	memcpy(tmpstring, nodename, name_len);
+	xendev->nodename = tmpstring;
+
+	tmpstring += name_len + 1;
+	memcpy(tmpstring, type, type_len);
+	xendev->devicetype = tmpstring;
+	init_completion(&xendev->down);
+
+	xendev->dev.bus = &bus->bus;
+	xendev->dev.release = xenbus_dev_release;
+
+	err = bus->get_bus_id(devname, xendev->nodename);
+	if (err)
+		goto fail;
+
+	dev_set_name(&xendev->dev, "%s", devname);
+	sema_init(&xendev->reclaim_sem, 1);
+
+	/* Register with generic device framework. */
+	err = device_register(&xendev->dev);
+	if (err) {
+		put_device(&xendev->dev);
+		xendev = NULL;
+		goto fail;
+	}
+
+	return 0;
+fail:
+	kfree(xendev);
+	return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_probe_node);
+
+static int xenbus_probe_device_type(struct xen_bus_type *bus, const char *type)
+{
+	int err = 0;
+	char **dir;
+	unsigned int dir_n = 0;
+	int i;
+
+	dir = xenbus_directory(XBT_NIL, bus->root, type, &dir_n);
+	if (IS_ERR(dir))
+		return PTR_ERR(dir);
+
+	for (i = 0; i < dir_n; i++) {
+		err = bus->probe(bus, type, dir[i]);
+		if (err)
+			break;
+	}
+
+	kfree(dir);
+	return err;
+}
+
+int xenbus_probe_devices(struct xen_bus_type *bus)
+{
+	int err = 0;
+	char **dir;
+	unsigned int i, dir_n;
+
+	dir = xenbus_directory(XBT_NIL, bus->root, "", &dir_n);
+	if (IS_ERR(dir))
+		return PTR_ERR(dir);
+
+	for (i = 0; i < dir_n; i++) {
+		err = xenbus_probe_device_type(bus, dir[i]);
+		if (err)
+			break;
+	}
+
+	kfree(dir);
+	return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_probe_devices);
+
+static unsigned int char_count(const char *str, char c)
+{
+	unsigned int i, ret = 0;
+
+	for (i = 0; str[i]; i++)
+		if (str[i] == c)
+			ret++;
+	return ret;
+}
+
+static int strsep_len(const char *str, char c, unsigned int len)
+{
+	unsigned int i;
+
+	for (i = 0; str[i]; i++)
+		if (str[i] == c) {
+			if (len == 0)
+				return i;
+			len--;
+		}
+	return (len == 0) ? i : -ERANGE;
+}
+
+void xenbus_dev_changed(const char *node, struct xen_bus_type *bus)
+{
+	int exists, rootlen;
+	struct xenbus_device *dev;
+	char type[XEN_BUS_ID_SIZE];
+	const char *p, *root;
+
+	if (char_count(node, '/') < 2)
+		return;
+
+	exists = xenbus_exists(XBT_NIL, node, "");
+	if (!exists) {
+		xenbus_cleanup_devices(node, &bus->bus);
+		return;
+	}
+
+	/* backend/<type>/... or device/<type>/... */
+	p = strchr(node, '/') + 1;
+	snprintf(type, XEN_BUS_ID_SIZE, "%.*s", (int)strcspn(p, "/"), p);
+	type[XEN_BUS_ID_SIZE-1] = '\0';
+
+	rootlen = strsep_len(node, '/', bus->levels);
+	if (rootlen < 0)
+		return;
+	root = kasprintf(GFP_KERNEL, "%.*s", rootlen, node);
+	if (!root)
+		return;
+
+	dev = xenbus_device_find(root, &bus->bus);
+	/*
+	 * Backend domain crash results in not coordinated frontend removal,
+	 * without going through XenbusStateClosing. If this is a new instance
+	 * of the same device Xen tools will have reset the state to
+	 * XenbusStateInitializing.
+	 * It might be that the backend crashed early during the init phase of
+	 * device setup, in which case the known state would have been
+	 * XenbusStateInitializing. So test the backend domid to match the
+	 * saved one. In case the new backend happens to have the same domid as
+	 * the old one, we can just carry on, as there is no inconsistency
+	 * resulting in this case.
+	 */
+	if (dev && !strcmp(bus->root, "device")) {
+		enum xenbus_state state = xenbus_read_driver_state(dev, dev->nodename);
+		unsigned int backend = xenbus_read_unsigned(root, "backend-id",
+							    dev->otherend_id);
+
+		if (state == XenbusStateInitialising &&
+		    (state != dev->state ||
+		     (dev->otherend && backend != dev->otherend_id))) {
+			/*
+			 * State has been reset, assume the old one vanished
+			 * and new one needs to be probed.
+			 */
+			dev_warn(&dev->dev,
+				 "state reset occurred (xenstore state %u, local state %u, xenstore backend %u, local backend %u), reconnecting\n",
+				 state, dev->state, backend, dev->otherend_id);
+			dev->vanished = true;
+		}
+		if (dev->vanished) {
+			device_unregister(&dev->dev);
+			put_device(&dev->dev);
+			dev = NULL;
+		}
+	}
+	if (!dev)
+		xenbus_probe_node(bus, type, root);
+	else
+		put_device(&dev->dev);
+
+	kfree(root);
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_changed);
+
+int xenbus_dev_freeze(struct device *dev)
+{
+	int err = 0;
+	struct xenbus_driver *drv;
+	struct xenbus_device *xdev
+		= container_of(dev, struct xenbus_device, dev);
+
+	DPRINTK("%s", xdev->nodename);
+
+	if (dev->driver == NULL)
+		return 0;
+	drv = to_xenbus_driver(dev->driver);
+	if (drv->suspend)
+		err = drv->suspend(xdev);
+	if (err)
+		dev_warn(dev, "freeze failed: %i\n", err);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_freeze);
+
+int xenbus_dev_restore(struct device *dev)
+{
+	int err;
+	struct xenbus_driver *drv;
+	struct xenbus_device *xdev
+		= container_of(dev, struct xenbus_device, dev);
+
+	DPRINTK("%s", xdev->nodename);
+
+	if (dev->driver == NULL)
+		return 0;
+	drv = to_xenbus_driver(dev->driver);
+	err = talk_to_otherend(xdev);
+	if (err) {
+		dev_warn(dev, "restore (talk_to_otherend) failed: %i\n", err);
+		return err;
+	}
+
+	xdev->state = XenbusStateInitialising;
+
+	if (drv->resume) {
+		err = drv->resume(xdev);
+		if (err) {
+			dev_warn(dev, "restore failed: %i\n", err);
+			return err;
+		}
+	}
+
+	err = watch_otherend(xdev);
+	if (err) {
+		dev_warn(dev, "restore (watch_otherend) failed: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_restore);
+
+int xenbus_dev_thaw(struct device *dev)
+{
+	/* Do nothing */
+	DPRINTK("thaw");
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_thaw);
+
+/* A flag to determine if xenstored is 'ready' (i.e. has started) */
+int xenstored_ready;
+
+
+int register_xenstore_notifier(struct notifier_block *nb)
+{
+	int ret = 0;
+
+	if (xenstored_ready > 0)
+		ret = nb->notifier_call(nb, 0, NULL);
+	else
+		blocking_notifier_chain_register(&xenstore_chain, nb);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(register_xenstore_notifier);
+
+void unregister_xenstore_notifier(struct notifier_block *nb)
+{
+	blocking_notifier_chain_unregister(&xenstore_chain, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_xenstore_notifier);
+
+static void xenbus_probe(void)
+{
+	xenstored_ready = 1;
+
+	if (!xen_store_interface)
+		xen_store_interface = memremap(xen_store_gfn << XEN_PAGE_SHIFT,
+					       XEN_PAGE_SIZE, MEMREMAP_WB);
+	/*
+	 * Now it is safe to free the IRQ used for xenstore late
+	 * initialization. No need to unbind: it is about to be
+	 * bound again from xb_init_comms. Note that calling
+	 * unbind_from_irqhandler now would result in xen_evtchn_close()
+	 * being called and the event channel not being enabled again
+	 * afterwards, resulting in missed event notifications.
+	 */
+	if (xs_init_irq >= 0)
+		free_irq(xs_init_irq, &xb_waitq);
+
+	/*
+	 * In the HVM case, xenbus_init() deferred its call to
+	 * xs_init() in case callbacks were not operational yet.
+	 * So do it now.
+	 */
+	if (xen_store_domain_type == XS_HVM)
+		xs_init();
+
+	/* Notify others that xenstore is up */
+	blocking_notifier_call_chain(&xenstore_chain, 0, NULL);
+}
+
+/*
+ * Returns true when XenStore init must be deferred in order to
+ * allow the PCI platform device to be initialised, before we
+ * can actually have event channel interrupts working.
+ */
+static bool xs_hvm_defer_init_for_callback(void)
+{
+#ifdef CONFIG_X86
+	return xen_store_domain_type == XS_HVM &&
+		!xen_have_vector_callback;
+#else
+	return false;
+#endif
+}
+
+static int xenbus_probe_thread(void *unused)
+{
+	DEFINE_WAIT(w);
+
+	/*
+	 * We actually just want to wait for *any* trigger of xb_waitq,
+	 * and run xenbus_probe() the moment it occurs.
+	 */
+	prepare_to_wait(&xb_waitq, &w, TASK_INTERRUPTIBLE);
+	schedule();
+	finish_wait(&xb_waitq, &w);
+
+	DPRINTK("probing");
+	xenbus_probe();
+	return 0;
+}
+
+static int __init xenbus_probe_initcall(void)
+{
+	if (!xen_domain())
+		return -ENODEV;
+
+	/*
+	 * Probe XenBus here in the XS_PV case, and also XS_HVM unless we
+	 * need to wait for the platform PCI device to come up or
+	 * xen_store_interface is not ready.
+	 */
+	if (xen_store_domain_type == XS_PV ||
+	    (xen_store_domain_type == XS_HVM &&
+	     !xs_hvm_defer_init_for_callback() &&
+	     XS_INTERFACE_READY))
+		xenbus_probe();
+
+	/*
+	 * For XS_LOCAL or when xen_store_interface is not ready, spawn a
+	 * thread which will wait for xenstored or a xenstore-stubdom to be
+	 * started, then probe.  It will be triggered when communication
+	 * starts happening, by waiting on xb_waitq.
+	 */
+	if (xen_store_domain_type == XS_LOCAL || !XS_INTERFACE_READY) {
+		struct task_struct *probe_task;
+
+		probe_task = kthread_run(xenbus_probe_thread, NULL,
+					 "xenbus_probe");
+		if (IS_ERR(probe_task))
+			return PTR_ERR(probe_task);
+	}
+	return 0;
+}
+device_initcall(xenbus_probe_initcall);
+
+int xen_set_callback_via(uint64_t via)
+{
+	struct xen_hvm_param a;
+	int ret;
+
+	a.domid = DOMID_SELF;
+	a.index = HVM_PARAM_CALLBACK_IRQ;
+	a.value = via;
+
+	ret = HYPERVISOR_hvm_op(HVMOP_set_param, &a);
+	if (ret)
+		return ret;
+
+	/*
+	 * If xenbus_probe_initcall() deferred the xenbus_probe()
+	 * due to the callback not functioning yet, we can do it now.
+	 */
+	if (!xenstored_ready && xs_hvm_defer_init_for_callback())
+		xenbus_probe();
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xen_set_callback_via);
+
+/* Set up event channel for xenstored which is run as a local process
+ * (this is normally used only in dom0)
+ */
+static int __init xenstored_local_init(void)
+{
+	int err = -ENOMEM;
+	unsigned long page = 0;
+	struct evtchn_alloc_unbound alloc_unbound;
+
+	/* Allocate Xenstore page */
+	page = get_zeroed_page(GFP_KERNEL);
+	if (!page)
+		goto out_err;
+
+	xen_store_gfn = virt_to_gfn((void *)page);
+
+	/* Next allocate a local port which xenstored can bind to */
+	alloc_unbound.dom        = DOMID_SELF;
+	alloc_unbound.remote_dom = DOMID_SELF;
+
+	err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
+					  &alloc_unbound);
+	if (err == -ENOSYS)
+		goto out_err;
+
+	BUG_ON(err);
+	xen_store_evtchn = alloc_unbound.port;
+
+	return 0;
+
+ out_err:
+	if (page != 0)
+		free_page(page);
+	return err;
+}
+
+static int xenbus_resume_cb(struct notifier_block *nb,
+			    unsigned long action, void *data)
+{
+	int err = 0;
+
+	if (xen_hvm_domain()) {
+		uint64_t v = 0;
+
+		err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
+		if (!err && v)
+			xen_store_evtchn = v;
+		else
+			pr_warn("Cannot update xenstore event channel: %d\n",
+				err);
+	} else
+		xen_store_evtchn = xen_start_info->store_evtchn;
+
+	return err;
+}
+
+static struct notifier_block xenbus_resume_nb = {
+	.notifier_call = xenbus_resume_cb,
+};
+
+static irqreturn_t xenbus_late_init(int irq, void *unused)
+{
+	int err;
+	uint64_t v = 0;
+
+	err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
+	if (err || !v || !~v)
+		return IRQ_HANDLED;
+	xen_store_gfn = (unsigned long)v;
+
+	wake_up(&xb_waitq);
+	return IRQ_HANDLED;
+}
+
+static int __init xenbus_init(void)
+{
+	int err;
+	uint64_t v = 0;
+	bool wait = false;
+	xen_store_domain_type = XS_UNKNOWN;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	xenbus_ring_ops_init();
+
+	if (xen_pv_domain())
+		xen_store_domain_type = XS_PV;
+	if (xen_hvm_domain())
+	{
+		xen_store_domain_type = XS_HVM;
+		err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
+		if (err)
+			goto out_error;
+		xen_store_evtchn = (int)v;
+		if (!v && xen_initial_domain())
+			xen_store_domain_type = XS_LOCAL;
+	}
+	if (xen_pv_domain() && !xen_start_info->store_evtchn)
+		xen_store_domain_type = XS_LOCAL;
+	if (xen_pv_domain() && xen_start_info->store_evtchn)
+		xenstored_ready = 1;
+
+	switch (xen_store_domain_type) {
+	case XS_LOCAL:
+		err = xenstored_local_init();
+		if (err)
+			goto out_error;
+		xen_store_interface = gfn_to_virt(xen_store_gfn);
+		break;
+	case XS_PV:
+		xen_store_evtchn = xen_start_info->store_evtchn;
+		xen_store_gfn = xen_start_info->store_mfn;
+		xen_store_interface = gfn_to_virt(xen_store_gfn);
+		break;
+	case XS_HVM:
+		err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
+		if (err)
+			goto out_error;
+		/*
+		 * Uninitialized hvm_params are zero and return no error.
+		 * Although it is theoretically possible to have
+		 * HVM_PARAM_STORE_PFN set to zero on purpose, in reality it is
+		 * not zero when valid. If zero, it means that Xenstore hasn't
+		 * been properly initialized. Instead of attempting to map a
+		 * wrong guest physical address return error.
+		 *
+		 * Also recognize all bits set as an invalid/uninitialized value.
+		 */
+		if (!v) {
+			err = -ENOENT;
+			goto out_error;
+		}
+		if (v == ~0ULL) {
+			wait = true;
+		} else {
+			/* Avoid truncation on 32-bit. */
+#if BITS_PER_LONG == 32
+			if (v > ULONG_MAX) {
+				pr_err("%s: cannot handle HVM_PARAM_STORE_PFN=%llx > ULONG_MAX\n",
+				       __func__, v);
+				err = -EINVAL;
+				goto out_error;
+			}
+#endif
+			xen_store_gfn = (unsigned long)v;
+			xen_store_interface =
+				memremap(xen_store_gfn << XEN_PAGE_SHIFT,
+					 XEN_PAGE_SIZE, MEMREMAP_WB);
+			if (!xen_store_interface) {
+				pr_err("%s: cannot map HVM_PARAM_STORE_PFN=%llx\n",
+				       __func__, v);
+				err = -EINVAL;
+				goto out_error;
+			}
+			if (xen_store_interface->connection != XENSTORE_CONNECTED)
+				wait = true;
+		}
+		if (wait) {
+			err = bind_evtchn_to_irqhandler(xen_store_evtchn,
+							xenbus_late_init,
+							0, "xenstore_late_init",
+							&xb_waitq);
+			if (err < 0) {
+				pr_err("xenstore_late_init couldn't bind irq err=%d\n",
+				       err);
+				goto out_error;
+			}
+
+			xs_init_irq = err;
+		}
+		break;
+	default:
+		pr_warn("Xenstore state unknown\n");
+		break;
+	}
+
+	/*
+	 * HVM domains may not have a functional callback yet. In that
+	 * case let xs_init() be called from xenbus_probe(), which will
+	 * get invoked at an appropriate time.
+	 */
+	if (xen_store_domain_type != XS_HVM) {
+		err = xs_init();
+		if (err) {
+			pr_warn("Error initializing xenstore comms: %i\n", err);
+			goto out_error;
+		}
+	}
+
+	if ((xen_store_domain_type != XS_LOCAL) &&
+	    (xen_store_domain_type != XS_UNKNOWN))
+		xen_resume_notifier_register(&xenbus_resume_nb);
+
+#ifdef CONFIG_XEN_COMPAT_XENFS
+	/*
+	 * Create xenfs mountpoint in /proc for compatibility with
+	 * utilities that expect to find "xenbus" under "/proc/xen".
+	 */
+	proc_create_mount_point("xen");
+#endif
+	return 0;
+
+out_error:
+	xen_store_domain_type = XS_UNKNOWN;
+	return err;
+}
+
+postcore_initcall(xenbus_init);
+
+MODULE_LICENSE("GPL");
diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c
new file mode 100644
index 000000000..5ebb72330
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus_probe_backend.c
@@ -0,0 +1,316 @@
+/******************************************************************************
+ * Talks to Xen Store to figure out what devices we have (backend half).
+ *
+ * Copyright (C) 2005 Rusty Russell, IBM Corporation
+ * Copyright (C) 2005 Mike Wray, Hewlett-Packard
+ * Copyright (C) 2005, 2006 XenSource Ltd
+ * Copyright (C) 2007 Solarflare Communications, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#define DPRINTK(fmt, ...)				\
+	pr_debug("(%s:%d) " fmt "\n",			\
+		 __func__, __LINE__, ##__VA_ARGS__)
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/string.h>
+#include <linux/ctype.h>
+#include <linux/fcntl.h>
+#include <linux/mm.h>
+#include <linux/notifier.h>
+#include <linux/export.h>
+#include <linux/semaphore.h>
+
+#include <asm/page.h>
+#include <asm/xen/hypervisor.h>
+#include <asm/hypervisor.h>
+#include <xen/xenbus.h>
+#include <xen/features.h>
+
+#include "xenbus.h"
+
+/* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */
+static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
+{
+	int domid, err;
+	const char *devid, *type, *frontend;
+	unsigned int typelen;
+
+	type = strchr(nodename, '/');
+	if (!type)
+		return -EINVAL;
+	type++;
+	typelen = strcspn(type, "/");
+	if (!typelen || type[typelen] != '/')
+		return -EINVAL;
+
+	devid = strrchr(nodename, '/') + 1;
+
+	err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid,
+			    "frontend", NULL, &frontend,
+			    NULL);
+	if (err)
+		return err;
+	if (strlen(frontend) == 0)
+		err = -ERANGE;
+	if (!err && !xenbus_exists(XBT_NIL, frontend, ""))
+		err = -ENOENT;
+	kfree(frontend);
+
+	if (err)
+		return err;
+
+	if (snprintf(bus_id, XEN_BUS_ID_SIZE, "%.*s-%i-%s",
+		     typelen, type, domid, devid) >= XEN_BUS_ID_SIZE)
+		return -ENOSPC;
+	return 0;
+}
+
+static int xenbus_uevent_backend(const struct device *dev,
+				 struct kobj_uevent_env *env)
+{
+	const struct xenbus_device *xdev;
+	const struct xenbus_driver *drv;
+	const struct xen_bus_type *bus;
+
+	DPRINTK("");
+
+	if (dev == NULL)
+		return -ENODEV;
+
+	xdev = to_xenbus_device(dev);
+	bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);
+
+	if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype))
+		return -ENOMEM;
+
+	/* stuff we want to pass to /sbin/hotplug */
+	if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype))
+		return -ENOMEM;
+
+	if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename))
+		return -ENOMEM;
+
+	if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root))
+		return -ENOMEM;
+
+	if (dev->driver) {
+		drv = to_xenbus_driver(dev->driver);
+		if (drv && drv->uevent)
+			return drv->uevent(xdev, env);
+	}
+
+	return 0;
+}
+
+/* backend/<typename>/<frontend-uuid>/<name> */
+static int xenbus_probe_backend_unit(struct xen_bus_type *bus,
+				     const char *dir,
+				     const char *type,
+				     const char *name)
+{
+	char *nodename;
+	int err;
+
+	nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name);
+	if (!nodename)
+		return -ENOMEM;
+
+	DPRINTK("%s\n", nodename);
+
+	err = xenbus_probe_node(bus, type, nodename);
+	kfree(nodename);
+	return err;
+}
+
+/* backend/<typename>/<frontend-domid> */
+static int xenbus_probe_backend(struct xen_bus_type *bus, const char *type,
+				const char *domid)
+{
+	char *nodename;
+	int err = 0;
+	char **dir;
+	unsigned int i, dir_n = 0;
+
+	DPRINTK("");
+
+	nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid);
+	if (!nodename)
+		return -ENOMEM;
+
+	dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n);
+	if (IS_ERR(dir)) {
+		kfree(nodename);
+		return PTR_ERR(dir);
+	}
+
+	for (i = 0; i < dir_n; i++) {
+		err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]);
+		if (err)
+			break;
+	}
+	kfree(dir);
+	kfree(nodename);
+	return err;
+}
+
+static bool frontend_will_handle(struct xenbus_watch *watch,
+				 const char *path, const char *token)
+{
+	return watch->nr_pending == 0;
+}
+
+static void frontend_changed(struct xenbus_watch *watch,
+			     const char *path, const char *token)
+{
+	xenbus_otherend_changed(watch, path, token, 0);
+}
+
+static struct xen_bus_type xenbus_backend = {
+	.root = "backend",
+	.levels = 3,		/* backend/type/<frontend>/<id> */
+	.get_bus_id = backend_bus_id,
+	.probe = xenbus_probe_backend,
+	.otherend_will_handle = frontend_will_handle,
+	.otherend_changed = frontend_changed,
+	.bus = {
+		.name		= "xen-backend",
+		.match		= xenbus_match,
+		.uevent		= xenbus_uevent_backend,
+		.probe		= xenbus_dev_probe,
+		.remove		= xenbus_dev_remove,
+		.dev_groups	= xenbus_dev_groups,
+	},
+};
+
+static void backend_changed(struct xenbus_watch *watch,
+			    const char *path, const char *token)
+{
+	DPRINTK("");
+
+	xenbus_dev_changed(path, &xenbus_backend);
+}
+
+static struct xenbus_watch be_watch = {
+	.node = "backend",
+	.callback = backend_changed,
+};
+
+static int read_frontend_details(struct xenbus_device *xendev)
+{
+	return xenbus_read_otherend_details(xendev, "frontend-id", "frontend");
+}
+
+int xenbus_dev_is_online(struct xenbus_device *dev)
+{
+	return !!xenbus_read_unsigned(dev->nodename, "online", 0);
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_is_online);
+
+int __xenbus_register_backend(struct xenbus_driver *drv, struct module *owner,
+			      const char *mod_name)
+{
+	drv->read_otherend_details = read_frontend_details;
+
+	return xenbus_register_driver_common(drv, &xenbus_backend,
+					     owner, mod_name);
+}
+EXPORT_SYMBOL_GPL(__xenbus_register_backend);
+
+static int backend_probe_and_watch(struct notifier_block *notifier,
+				   unsigned long event,
+				   void *data)
+{
+	/* Enumerate devices in xenstore and watch for changes. */
+	xenbus_probe_devices(&xenbus_backend);
+	register_xenbus_watch(&be_watch);
+
+	return NOTIFY_DONE;
+}
+
+static int backend_reclaim_memory(struct device *dev, void *data)
+{
+	const struct xenbus_driver *drv;
+	struct xenbus_device *xdev;
+
+	if (!dev->driver)
+		return 0;
+	drv = to_xenbus_driver(dev->driver);
+	if (drv && drv->reclaim_memory) {
+		xdev = to_xenbus_device(dev);
+		if (down_trylock(&xdev->reclaim_sem))
+			return 0;
+		drv->reclaim_memory(xdev);
+		up(&xdev->reclaim_sem);
+	}
+	return 0;
+}
+
+/*
+ * Returns 0 always because we are using shrinker to only detect memory
+ * pressure.
+ */
+static unsigned long backend_shrink_memory_count(struct shrinker *shrinker,
+				struct shrink_control *sc)
+{
+	bus_for_each_dev(&xenbus_backend.bus, NULL, NULL,
+			backend_reclaim_memory);
+	return 0;
+}
+
+static int __init xenbus_probe_backend_init(void)
+{
+	struct shrinker *backend_memory_shrinker;
+	static struct notifier_block xenstore_notifier = {
+		.notifier_call = backend_probe_and_watch
+	};
+	int err;
+
+	DPRINTK("");
+
+	/* Register ourselves with the kernel bus subsystem */
+	err = bus_register(&xenbus_backend.bus);
+	if (err)
+		return err;
+
+	register_xenstore_notifier(&xenstore_notifier);
+
+	backend_memory_shrinker = shrinker_alloc(0, "xen-backend");
+	if (!backend_memory_shrinker) {
+		pr_warn("shrinker allocation failed\n");
+		return 0;
+	}
+
+	backend_memory_shrinker->count_objects = backend_shrink_memory_count;
+
+	shrinker_register(backend_memory_shrinker);
+
+	return 0;
+}
+subsys_initcall(xenbus_probe_backend_init);
diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c b/drivers/xen/xenbus/xenbus_probe_frontend.c
new file mode 100644
index 000000000..ca0460973
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -0,0 +1,515 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#define DPRINTK(fmt, ...)				\
+	pr_debug("(%s:%d) " fmt "\n",			\
+		 __func__, __LINE__, ##__VA_ARGS__)
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/string.h>
+#include <linux/ctype.h>
+#include <linux/fcntl.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/notifier.h>
+#include <linux/kthread.h>
+#include <linux/mutex.h>
+#include <linux/io.h>
+#include <linux/module.h>
+
+#include <asm/page.h>
+#include <asm/xen/hypervisor.h>
+#include <xen/xenbus.h>
+#include <xen/events.h>
+#include <xen/page.h>
+#include <xen/xen.h>
+
+#include <xen/platform_pci.h>
+
+#include "xenbus.h"
+
+
+
+/* device/<type>/<id> => <type>-<id> */
+static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
+{
+	nodename = strchr(nodename, '/');
+	if (!nodename || strlen(nodename + 1) >= XEN_BUS_ID_SIZE) {
+		pr_warn("bad frontend %s\n", nodename);
+		return -EINVAL;
+	}
+
+	strscpy(bus_id, nodename + 1, XEN_BUS_ID_SIZE);
+	if (!strchr(bus_id, '/')) {
+		pr_warn("bus_id %s no slash\n", bus_id);
+		return -EINVAL;
+	}
+	*strchr(bus_id, '/') = '-';
+	return 0;
+}
+
+/* device/<typename>/<name> */
+static int xenbus_probe_frontend(struct xen_bus_type *bus, const char *type,
+				 const char *name)
+{
+	char *nodename;
+	int err;
+
+	/* ignore console/0 */
+	if (!strncmp(type, "console", 7) && !strncmp(name, "0", 1)) {
+		DPRINTK("Ignoring buggy device entry console/0");
+		return 0;
+	}
+
+	nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, name);
+	if (!nodename)
+		return -ENOMEM;
+
+	DPRINTK("%s", nodename);
+
+	err = xenbus_probe_node(bus, type, nodename);
+	kfree(nodename);
+	return err;
+}
+
+static int xenbus_uevent_frontend(const struct device *_dev,
+				  struct kobj_uevent_env *env)
+{
+	const struct xenbus_device *dev = to_xenbus_device(_dev);
+
+	if (add_uevent_var(env, "MODALIAS=xen:%s", dev->devicetype))
+		return -ENOMEM;
+
+	return 0;
+}
+
+
+static void backend_changed(struct xenbus_watch *watch,
+			    const char *path, const char *token)
+{
+	xenbus_otherend_changed(watch, path, token, 1);
+}
+
+static void xenbus_frontend_delayed_restore(struct work_struct *w)
+{
+	struct xenbus_device *xdev = container_of(w, struct xenbus_device, work);
+
+	xenbus_dev_restore(&xdev->dev);
+}
+
+static int xenbus_frontend_dev_restore(struct device *dev)
+{
+	/*
+	 * If xenstored is running in this domain, we cannot access the backend
+	 * state at the moment, so we need to defer xenbus_dev_resume
+	 */
+	if (xen_store_domain_type == XS_LOCAL) {
+		struct xenbus_device *xdev = to_xenbus_device(dev);
+
+		schedule_work(&xdev->work);
+
+		return 0;
+	}
+
+	return xenbus_dev_restore(dev);
+}
+
+static int xenbus_frontend_dev_probe(struct device *dev)
+{
+	if (xen_store_domain_type == XS_LOCAL) {
+		struct xenbus_device *xdev = to_xenbus_device(dev);
+		INIT_WORK(&xdev->work, xenbus_frontend_delayed_restore);
+	}
+
+	return xenbus_dev_probe(dev);
+}
+
+static void xenbus_frontend_dev_shutdown(struct device *_dev)
+{
+	struct xenbus_device *dev = to_xenbus_device(_dev);
+	unsigned long timeout = 5*HZ;
+
+	DPRINTK("%s", dev->nodename);
+
+	get_device(&dev->dev);
+	if (dev->state != XenbusStateConnected) {
+		pr_info("%s: %s: %s != Connected, skipping\n",
+			__func__, dev->nodename, xenbus_strstate(dev->state));
+		goto out;
+	}
+	xenbus_switch_state(dev, XenbusStateClosing);
+	timeout = wait_for_completion_timeout(&dev->down, timeout);
+	if (!timeout)
+		pr_info("%s: %s timeout closing device\n",
+			__func__, dev->nodename);
+ out:
+	put_device(&dev->dev);
+}
+
+static const struct dev_pm_ops xenbus_pm_ops = {
+	.freeze		= xenbus_dev_freeze,
+	.thaw		= xenbus_dev_thaw,
+	.restore	= xenbus_frontend_dev_restore,
+};
+
+static struct xen_bus_type xenbus_frontend = {
+	.root = "device",
+	.levels = 2,		/* device/type/<id> */
+	.get_bus_id = frontend_bus_id,
+	.probe = xenbus_probe_frontend,
+	.otherend_changed = backend_changed,
+	.bus = {
+		.name		= "xen",
+		.match		= xenbus_match,
+		.uevent		= xenbus_uevent_frontend,
+		.probe		= xenbus_frontend_dev_probe,
+		.remove		= xenbus_dev_remove,
+		.shutdown	= xenbus_frontend_dev_shutdown,
+		.dev_groups	= xenbus_dev_groups,
+
+		.pm		= &xenbus_pm_ops,
+	},
+};
+
+static void frontend_changed(struct xenbus_watch *watch,
+			     const char *path, const char *token)
+{
+	DPRINTK("");
+
+	xenbus_dev_changed(path, &xenbus_frontend);
+}
+
+
+/* We watch for devices appearing and vanishing. */
+static struct xenbus_watch fe_watch = {
+	.node = "device",
+	.callback = frontend_changed,
+};
+
+static int read_backend_details(struct xenbus_device *xendev)
+{
+	return xenbus_read_otherend_details(xendev, "backend-id", "backend");
+}
+
+static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
+{
+	struct xenbus_device *xendev = to_xenbus_device(dev);
+	struct device_driver *drv = data;
+	struct xenbus_driver *xendrv;
+
+	/*
+	 * A device with no driver will never connect. We care only about
+	 * devices which should currently be in the process of connecting.
+	 */
+	if (!dev->driver)
+		return 0;
+
+	/* Is this search limited to a particular driver? */
+	if (drv && (dev->driver != drv))
+		return 0;
+
+	xendrv = to_xenbus_driver(dev->driver);
+
+	if (ignore_nonessential && xendrv->not_essential)
+		return 0;
+
+	return (xendev->state < XenbusStateConnected ||
+		(xendev->state == XenbusStateConnected &&
+		 xendrv->is_ready && !xendrv->is_ready(xendev)));
+}
+static int essential_device_connecting(struct device *dev, void *data)
+{
+	return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
+}
+static int non_essential_device_connecting(struct device *dev, void *data)
+{
+	return is_device_connecting(dev, data, false);
+}
+
+static int exists_essential_connecting_device(struct device_driver *drv)
+{
+	return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
+				essential_device_connecting);
+}
+static int exists_non_essential_connecting_device(struct device_driver *drv)
+{
+	return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
+				non_essential_device_connecting);
+}
+
+static int print_device_status(struct device *dev, void *data)
+{
+	struct xenbus_device *xendev = to_xenbus_device(dev);
+	struct device_driver *drv = data;
+
+	/* Is this operation limited to a particular driver? */
+	if (drv && (dev->driver != drv))
+		return 0;
+
+	if (!dev->driver) {
+		/* Information only: is this too noisy? */
+		pr_info("Device with no driver: %s\n", xendev->nodename);
+	} else if (xendev->state < XenbusStateConnected) {
+		enum xenbus_state rstate = XenbusStateUnknown;
+		if (xendev->otherend)
+			rstate = xenbus_read_driver_state(xendev, xendev->otherend);
+		pr_warn("Timeout connecting to device: %s (local state %d, remote state %d)\n",
+			xendev->nodename, xendev->state, rstate);
+	}
+
+	return 0;
+}
+
+/* We only wait for device setup after most initcalls have run. */
+static int ready_to_wait_for_devices;
+
+static bool wait_loop(unsigned long start, unsigned int max_delay,
+		     unsigned int *seconds_waited)
+{
+	if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
+		if (!*seconds_waited)
+			pr_warn("Waiting for devices to initialise: ");
+		*seconds_waited += 5;
+		pr_cont("%us...", max_delay - *seconds_waited);
+		if (*seconds_waited == max_delay) {
+			pr_cont("\n");
+			return true;
+		}
+	}
+
+	schedule_timeout_interruptible(HZ/10);
+
+	return false;
+}
+/*
+ * On a 5-minute timeout, wait for all devices currently configured.  We need
+ * to do this to guarantee that the filesystems and / or network devices
+ * needed for boot are available, before we can allow the boot to proceed.
+ *
+ * This needs to be on a late_initcall, to happen after the frontend device
+ * drivers have been initialised, but before the root fs is mounted.
+ *
+ * A possible improvement here would be to have the tools add a per-device
+ * flag to the store entry, indicating whether it is needed at boot time.
+ * This would allow people who knew what they were doing to accelerate their
+ * boot slightly, but of course needs tools or manual intervention to set up
+ * those flags correctly.
+ */
+static void wait_for_devices(struct xenbus_driver *xendrv)
+{
+	unsigned long start = jiffies;
+	struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
+	unsigned int seconds_waited = 0;
+
+	if (!ready_to_wait_for_devices || !xen_domain())
+		return;
+
+	while (exists_non_essential_connecting_device(drv))
+		if (wait_loop(start, 30, &seconds_waited))
+			break;
+
+	/* Skips PVKB and PVFB check.*/
+	while (exists_essential_connecting_device(drv))
+		if (wait_loop(start, 270, &seconds_waited))
+			break;
+
+	if (seconds_waited)
+		printk("\n");
+
+	bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
+			 print_device_status);
+}
+
+int __xenbus_register_frontend(struct xenbus_driver *drv, struct module *owner,
+			       const char *mod_name)
+{
+	int ret;
+
+	drv->read_otherend_details = read_backend_details;
+
+	ret = xenbus_register_driver_common(drv, &xenbus_frontend,
+					    owner, mod_name);
+	if (ret)
+		return ret;
+
+	/* If this driver is loaded as a module wait for devices to attach. */
+	wait_for_devices(drv);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
+
+static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
+static int backend_state;
+
+static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
+					const char *path, const char *token)
+{
+	if (xenbus_scanf(XBT_NIL, path, "", "%i",
+			 &backend_state) != 1)
+		backend_state = XenbusStateUnknown;
+	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
+	       path, xenbus_strstate(backend_state));
+	wake_up(&backend_state_wq);
+}
+
+static void xenbus_reset_wait_for_backend(char *be, int expected)
+{
+	long timeout;
+	timeout = wait_event_interruptible_timeout(backend_state_wq,
+			backend_state == expected, 5 * HZ);
+	if (timeout <= 0)
+		pr_info("backend %s timed out\n", be);
+}
+
+/*
+ * Reset frontend if it is in Connected or Closed state.
+ * Wait for backend to catch up.
+ * State Connected happens during kdump, Closed after kexec.
+ */
+static void xenbus_reset_frontend(char *fe, char *be, int be_state)
+{
+	struct xenbus_watch be_watch;
+
+	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
+			be, xenbus_strstate(be_state));
+
+	memset(&be_watch, 0, sizeof(be_watch));
+	be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
+	if (!be_watch.node)
+		return;
+
+	be_watch.callback = xenbus_reset_backend_state_changed;
+	backend_state = XenbusStateUnknown;
+
+	pr_info("triggering reconnect on %s\n", be);
+	register_xenbus_watch(&be_watch);
+
+	/* fall through to forward backend to state XenbusStateInitialising */
+	switch (be_state) {
+	case XenbusStateConnected:
+		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
+		xenbus_reset_wait_for_backend(be, XenbusStateClosing);
+		fallthrough;
+
+	case XenbusStateClosing:
+		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
+		xenbus_reset_wait_for_backend(be, XenbusStateClosed);
+		fallthrough;
+
+	case XenbusStateClosed:
+		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
+		xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
+	}
+
+	unregister_xenbus_watch(&be_watch);
+	pr_info("reconnect done on %s\n", be);
+	kfree(be_watch.node);
+}
+
+static void xenbus_check_frontend(char *class, char *dev)
+{
+	int be_state, fe_state, err;
+	char *backend, *frontend;
+
+	frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
+	if (!frontend)
+		return;
+
+	err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
+	if (err != 1)
+		goto out;
+
+	switch (fe_state) {
+	case XenbusStateConnected:
+	case XenbusStateClosed:
+		printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
+				frontend, xenbus_strstate(fe_state));
+		backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
+		if (IS_ERR_OR_NULL(backend))
+			goto out;
+		err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
+		if (err == 1)
+			xenbus_reset_frontend(frontend, backend, be_state);
+		kfree(backend);
+		break;
+	default:
+		break;
+	}
+out:
+	kfree(frontend);
+}
+
+static void xenbus_reset_state(void)
+{
+	char **devclass, **dev;
+	int devclass_n, dev_n;
+	int i, j;
+
+	devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
+	if (IS_ERR(devclass))
+		return;
+
+	for (i = 0; i < devclass_n; i++) {
+		dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
+		if (IS_ERR(dev))
+			continue;
+		for (j = 0; j < dev_n; j++)
+			xenbus_check_frontend(devclass[i], dev[j]);
+		kfree(dev);
+	}
+	kfree(devclass);
+}
+
+static int frontend_probe_and_watch(struct notifier_block *notifier,
+				   unsigned long event,
+				   void *data)
+{
+	/* reset devices in Connected or Closed state */
+	if (xen_hvm_domain())
+		xenbus_reset_state();
+	/* Enumerate devices in xenstore and watch for changes. */
+	xenbus_probe_devices(&xenbus_frontend);
+	register_xenbus_watch(&fe_watch);
+
+	return NOTIFY_DONE;
+}
+
+
+static int __init xenbus_probe_frontend_init(void)
+{
+	static struct notifier_block xenstore_notifier = {
+		.notifier_call = frontend_probe_and_watch
+	};
+	int err;
+
+	DPRINTK("");
+
+	/* Register ourselves with the kernel bus subsystem */
+	err = bus_register(&xenbus_frontend.bus);
+	if (err)
+		return err;
+
+	register_xenstore_notifier(&xenstore_notifier);
+
+	return 0;
+}
+subsys_initcall(xenbus_probe_frontend_init);
+
+#ifndef MODULE
+static int __init boot_wait_for_devices(void)
+{
+	if (!xen_has_pv_devices())
+		return -ENODEV;
+
+	ready_to_wait_for_devices = 1;
+	wait_for_devices(NULL);
+	return 0;
+}
+
+late_initcall(boot_wait_for_devices);
+#endif
+
+MODULE_DESCRIPTION("Xen PV-device frontend support");
+MODULE_LICENSE("GPL");
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
new file mode 100644
index 000000000..62274d377
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -0,0 +1,941 @@
+/******************************************************************************
+ * xenbus_xs.c
+ *
+ * This is the kernel equivalent of the "xs" library.  We don't need everything
+ * and we use xenbus_comms for communication.
+ *
+ * Copyright (C) 2005 Rusty Russell, IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/unistd.h>
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/uio.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/fcntl.h>
+#include <linux/kthread.h>
+#include <linux/reboot.h>
+#include <linux/rwsem.h>
+#include <linux/mutex.h>
+#include <asm/xen/hypervisor.h>
+#ifdef CONFIG_X86
+#include <asm/cpuid/api.h>
+#endif
+#include <xen/xenbus.h>
+#include <xen/xen.h>
+#include "xenbus.h"
+
+/*
+ * Framework to protect suspend/resume handling against normal Xenstore
+ * message handling:
+ * During suspend/resume there must be no open transaction and no pending
+ * Xenstore request.
+ * New watch events happening in this time can be ignored by firing all watches
+ * after resume.
+ */
+
+/* Lock protecting enter/exit critical region. */
+static DEFINE_SPINLOCK(xs_state_lock);
+/* Number of users in critical region (protected by xs_state_lock). */
+static unsigned int xs_state_users;
+/* Suspend handler waiting or already active (protected by xs_state_lock)? */
+static int xs_suspend_active;
+/* Unique Xenstore request id (protected by xs_state_lock). */
+static uint32_t xs_request_id;
+
+/* Wait queue for all callers waiting for critical region to become usable. */
+static DECLARE_WAIT_QUEUE_HEAD(xs_state_enter_wq);
+/* Wait queue for suspend handling waiting for critical region being empty. */
+static DECLARE_WAIT_QUEUE_HEAD(xs_state_exit_wq);
+
+/* List of registered watches, and a lock to protect it. */
+static LIST_HEAD(watches);
+static DEFINE_SPINLOCK(watches_lock);
+
+/* List of pending watch callback events, and a lock to protect it. */
+static LIST_HEAD(watch_events);
+static DEFINE_SPINLOCK(watch_events_lock);
+
+/* Protect watch (de)register against save/restore. */
+static DECLARE_RWSEM(xs_watch_rwsem);
+
+/*
+ * Details of the xenwatch callback kernel thread. The thread waits on the
+ * watch_events_waitq for work to do (queued on watch_events list). When it
+ * wakes up it acquires the xenwatch_mutex before reading the list and
+ * carrying out work.
+ */
+static pid_t xenwatch_pid;
+static DEFINE_MUTEX(xenwatch_mutex);
+static DECLARE_WAIT_QUEUE_HEAD(watch_events_waitq);
+
+static void xs_suspend_enter(void)
+{
+	spin_lock(&xs_state_lock);
+	xs_suspend_active++;
+	spin_unlock(&xs_state_lock);
+	wait_event(xs_state_exit_wq, xs_state_users == 0);
+}
+
+static void xs_suspend_exit(void)
+{
+	xb_dev_generation_id++;
+	spin_lock(&xs_state_lock);
+	xs_suspend_active--;
+	spin_unlock(&xs_state_lock);
+	wake_up_all(&xs_state_enter_wq);
+}
+
+void xs_free_req(struct kref *kref)
+{
+	struct xb_req_data *req = container_of(kref, struct xb_req_data, kref);
+	kfree(req);
+}
+
+static uint32_t xs_request_enter(struct xb_req_data *req)
+{
+	uint32_t rq_id;
+
+	req->type = req->msg.type;
+
+	spin_lock(&xs_state_lock);
+
+	while (!xs_state_users && xs_suspend_active) {
+		spin_unlock(&xs_state_lock);
+		wait_event(xs_state_enter_wq, xs_suspend_active == 0);
+		spin_lock(&xs_state_lock);
+	}
+
+	if (req->type == XS_TRANSACTION_START && !req->user_req)
+		xs_state_users++;
+	xs_state_users++;
+	rq_id = xs_request_id++;
+
+	spin_unlock(&xs_state_lock);
+
+	return rq_id;
+}
+
+void xs_request_exit(struct xb_req_data *req)
+{
+	spin_lock(&xs_state_lock);
+	xs_state_users--;
+	if ((req->type == XS_TRANSACTION_START && req->msg.type == XS_ERROR) ||
+	    (req->type == XS_TRANSACTION_END && !req->user_req &&
+	     !WARN_ON_ONCE(req->msg.type == XS_ERROR &&
+			   !strcmp(req->body, "ENOENT"))))
+		xs_state_users--;
+	spin_unlock(&xs_state_lock);
+
+	if (xs_suspend_active && !xs_state_users)
+		wake_up(&xs_state_exit_wq);
+}
+
+static int get_error(const char *errorstring)
+{
+	unsigned int i;
+
+	for (i = 0; strcmp(errorstring, xsd_errors[i].errstring) != 0; i++) {
+		if (i == ARRAY_SIZE(xsd_errors) - 1) {
+			pr_warn("xen store gave: unknown error %s\n",
+				errorstring);
+			return EINVAL;
+		}
+	}
+	return xsd_errors[i].errnum;
+}
+
+static bool xenbus_ok(void)
+{
+	switch (xen_store_domain_type) {
+	case XS_LOCAL:
+		switch (system_state) {
+		case SYSTEM_POWER_OFF:
+		case SYSTEM_RESTART:
+		case SYSTEM_HALT:
+			return false;
+		default:
+			break;
+		}
+		return true;
+	case XS_PV:
+	case XS_HVM:
+		/* FIXME: Could check that the remote domain is alive,
+		 * but it is normally initial domain. */
+		return true;
+	default:
+		break;
+	}
+	return false;
+}
+
+static bool test_reply(struct xb_req_data *req)
+{
+	if (req->state == xb_req_state_got_reply || !xenbus_ok()) {
+		/* read req->state before all other fields */
+		virt_rmb();
+		return true;
+	}
+
+	/* Make sure to reread req->state each time. */
+	barrier();
+
+	return false;
+}
+
+static void *read_reply(struct xb_req_data *req)
+{
+	do {
+		wait_event(req->wq, test_reply(req));
+
+		if (!xenbus_ok())
+			/*
+			 * If we are in the process of being shut-down there is
+			 * no point of trying to contact XenBus - it is either
+			 * killed (xenstored application) or the other domain
+			 * has been killed or is unreachable.
+			 */
+			return ERR_PTR(-EIO);
+		if (req->err)
+			return ERR_PTR(req->err);
+
+	} while (req->state != xb_req_state_got_reply);
+
+	return req->body;
+}
+
+static void xs_send(struct xb_req_data *req, struct xsd_sockmsg *msg)
+{
+	bool notify;
+
+	req->msg = *msg;
+	req->err = 0;
+	req->state = xb_req_state_queued;
+	init_waitqueue_head(&req->wq);
+
+	/* Save the caller req_id and restore it later in the reply */
+	req->caller_req_id = req->msg.req_id;
+	req->msg.req_id = xs_request_enter(req);
+
+	/*
+	 * Take 2nd ref.  One for this thread, and the second for the
+	 * xenbus_thread.
+	 */
+	kref_get(&req->kref);
+
+	mutex_lock(&xb_write_mutex);
+	list_add_tail(&req->list, &xb_write_list);
+	notify = list_is_singular(&xb_write_list);
+	mutex_unlock(&xb_write_mutex);
+
+	if (notify)
+		wake_up(&xb_waitq);
+}
+
+static void *xs_wait_for_reply(struct xb_req_data *req, struct xsd_sockmsg *msg)
+{
+	void *ret;
+
+	ret = read_reply(req);
+
+	xs_request_exit(req);
+
+	msg->type = req->msg.type;
+	msg->len = req->msg.len;
+
+	mutex_lock(&xb_write_mutex);
+	if (req->state == xb_req_state_queued ||
+	    req->state == xb_req_state_wait_reply)
+		req->state = xb_req_state_aborted;
+
+	kref_put(&req->kref, xs_free_req);
+	mutex_unlock(&xb_write_mutex);
+
+	return ret;
+}
+
+static void xs_wake_up(struct xb_req_data *req)
+{
+	wake_up(&req->wq);
+}
+
+int xenbus_dev_request_and_reply(struct xsd_sockmsg *msg, void *par)
+{
+	struct xb_req_data *req;
+	struct kvec *vec;
+
+	req = kmalloc(sizeof(*req) + sizeof(*vec), GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+
+	vec = (struct kvec *)(req + 1);
+	vec->iov_len = msg->len;
+	vec->iov_base = msg + 1;
+
+	req->vec = vec;
+	req->num_vecs = 1;
+	req->cb = xenbus_dev_queue_reply;
+	req->par = par;
+	req->user_req = true;
+	kref_init(&req->kref);
+
+	xs_send(req, msg);
+
+	return 0;
+}
+EXPORT_SYMBOL(xenbus_dev_request_and_reply);
+
+/* Send message to xs, get kmalloc'ed reply.  ERR_PTR() on error. */
+static void *xs_talkv(struct xenbus_transaction t,
+		      enum xsd_sockmsg_type type,
+		      const struct kvec *iovec,
+		      unsigned int num_vecs,
+		      unsigned int *len)
+{
+	struct xb_req_data *req;
+	struct xsd_sockmsg msg;
+	void *ret = NULL;
+	unsigned int i;
+	int err;
+
+	req = kmalloc_obj(*req, GFP_NOIO | __GFP_HIGH);
+	if (!req)
+		return ERR_PTR(-ENOMEM);
+
+	req->vec = iovec;
+	req->num_vecs = num_vecs;
+	req->cb = xs_wake_up;
+	req->user_req = false;
+	kref_init(&req->kref);
+
+	msg.req_id = 0;
+	msg.tx_id = t.id;
+	msg.type = type;
+	msg.len = 0;
+	for (i = 0; i < num_vecs; i++)
+		msg.len += iovec[i].iov_len;
+
+	xs_send(req, &msg);
+
+	ret = xs_wait_for_reply(req, &msg);
+	if (len)
+		*len = msg.len;
+
+	if (IS_ERR(ret))
+		return ret;
+
+	if (msg.type == XS_ERROR) {
+		err = get_error(ret);
+		kfree(ret);
+		return ERR_PTR(-err);
+	}
+
+	if (msg.type != type) {
+		pr_warn_ratelimited("unexpected type [%d], expected [%d]\n",
+				    msg.type, type);
+		kfree(ret);
+		return ERR_PTR(-EINVAL);
+	}
+	return ret;
+}
+
+/* Simplified version of xs_talkv: single message. */
+static void *xs_single(struct xenbus_transaction t,
+		       enum xsd_sockmsg_type type,
+		       const char *string,
+		       unsigned int *len)
+{
+	struct kvec iovec;
+
+	iovec.iov_base = (void *)string;
+	iovec.iov_len = strlen(string) + 1;
+	return xs_talkv(t, type, &iovec, 1, len);
+}
+
+/* Many commands only need an ack, don't care what it says. */
+static int xs_error(char *reply)
+{
+	if (IS_ERR(reply))
+		return PTR_ERR(reply);
+	kfree(reply);
+	return 0;
+}
+
+static unsigned int count_strings(const char *strings, unsigned int len)
+{
+	unsigned int num;
+	const char *p;
+
+	for (p = strings, num = 0; p < strings + len; p += strlen(p) + 1)
+		num++;
+
+	return num;
+}
+
+/* Return the path to dir with /name appended. Buffer must be kfree()'ed. */
+static char *join(const char *dir, const char *name)
+{
+	char *buffer;
+
+	if (strlen(name) == 0)
+		buffer = kasprintf(GFP_NOIO | __GFP_HIGH, "%s", dir);
+	else
+		buffer = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/%s", dir, name);
+	return buffer ?: ERR_PTR(-ENOMEM);
+}
+
+static char **split_strings(char *strings, unsigned int len, unsigned int *num)
+{
+	char *p, **ret;
+
+	if (len && strings[len - 1]) {
+		pr_err_once("malformed XS_DIRECTORY reply\n");
+		kfree(strings);
+		return ERR_PTR(-EIO);
+	}
+
+	/* Count the strings. */
+	*num = count_strings(strings, len);
+
+	/* Transfer to one big alloc for easy freeing. */
+	ret = kmalloc(*num * sizeof(char *) + len, GFP_NOIO | __GFP_HIGH);
+	if (!ret) {
+		kfree(strings);
+		return ERR_PTR(-ENOMEM);
+	}
+	memcpy(&ret[*num], strings, len);
+	kfree(strings);
+
+	strings = (char *)&ret[*num];
+	for (p = strings, *num = 0; p < strings + len; p += strlen(p) + 1)
+		ret[(*num)++] = p;
+
+	return ret;
+}
+
+char **xenbus_directory(struct xenbus_transaction t,
+			const char *dir, const char *node, unsigned int *num)
+{
+	char *strings, *path;
+	unsigned int len;
+
+	path = join(dir, node);
+	if (IS_ERR(path))
+		return ERR_CAST(path);
+
+	strings = xs_single(t, XS_DIRECTORY, path, &len);
+	kfree(path);
+	if (IS_ERR(strings))
+		return ERR_CAST(strings);
+
+	return split_strings(strings, len, num);
+}
+EXPORT_SYMBOL_GPL(xenbus_directory);
+
+/* Check if a path exists. Return 1 if it does. */
+int xenbus_exists(struct xenbus_transaction t,
+		  const char *dir, const char *node)
+{
+	char **d;
+	int dir_n;
+
+	d = xenbus_directory(t, dir, node, &dir_n);
+	if (IS_ERR(d))
+		return 0;
+	kfree(d);
+	return 1;
+}
+EXPORT_SYMBOL_GPL(xenbus_exists);
+
+/* Get the value of a single file.
+ * Returns a kmalloced value: call free() on it after use.
+ * len indicates length in bytes.
+ */
+void *xenbus_read(struct xenbus_transaction t,
+		  const char *dir, const char *node, unsigned int *len)
+{
+	char *path;
+	void *ret;
+
+	path = join(dir, node);
+	if (IS_ERR(path))
+		return ERR_CAST(path);
+
+	ret = xs_single(t, XS_READ, path, len);
+	kfree(path);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xenbus_read);
+
+/* Write the value of a single file.
+ * Returns -err on failure.
+ */
+int xenbus_write(struct xenbus_transaction t,
+		 const char *dir, const char *node, const char *string)
+{
+	const char *path;
+	struct kvec iovec[2];
+	int ret;
+
+	path = join(dir, node);
+	if (IS_ERR(path))
+		return PTR_ERR(path);
+
+	iovec[0].iov_base = (void *)path;
+	iovec[0].iov_len = strlen(path) + 1;
+	iovec[1].iov_base = (void *)string;
+	iovec[1].iov_len = strlen(string);
+
+	ret = xs_error(xs_talkv(t, XS_WRITE, iovec, ARRAY_SIZE(iovec), NULL));
+	kfree(path);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xenbus_write);
+
+/* Destroy a file or directory (directories must be empty). */
+int xenbus_rm(struct xenbus_transaction t, const char *dir, const char *node)
+{
+	char *path;
+	int ret;
+
+	path = join(dir, node);
+	if (IS_ERR(path))
+		return PTR_ERR(path);
+
+	ret = xs_error(xs_single(t, XS_RM, path, NULL));
+	kfree(path);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xenbus_rm);
+
+/* Start a transaction: changes by others will not be seen during this
+ * transaction, and changes will not be visible to others until end.
+ */
+int xenbus_transaction_start(struct xenbus_transaction *t)
+{
+	char *id_str;
+
+	id_str = xs_single(XBT_NIL, XS_TRANSACTION_START, "", NULL);
+	if (IS_ERR(id_str))
+		return PTR_ERR(id_str);
+
+	t->id = simple_strtoul(id_str, NULL, 0);
+	kfree(id_str);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xenbus_transaction_start);
+
+/* End a transaction.
+ * If abort is true, transaction is discarded instead of committed.
+ */
+int xenbus_transaction_end(struct xenbus_transaction t, bool abort)
+{
+	return xs_error(xs_single(t, XS_TRANSACTION_END, abort ? "F" : "T",
+				  NULL));
+}
+EXPORT_SYMBOL_GPL(xenbus_transaction_end);
+
+/* Single read and scanf: returns -errno or num scanned. */
+int xenbus_scanf(struct xenbus_transaction t,
+		 const char *dir, const char *node, const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+	char *val;
+
+	val = xenbus_read(t, dir, node, NULL);
+	if (IS_ERR(val))
+		return PTR_ERR(val);
+
+	va_start(ap, fmt);
+	ret = vsscanf(val, fmt, ap);
+	va_end(ap);
+	kfree(val);
+	/* Distinctive errno. */
+	if (ret == 0)
+		return -ERANGE;
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xenbus_scanf);
+
+/* Read an (optional) unsigned value. */
+unsigned int xenbus_read_unsigned(const char *dir, const char *node,
+				  unsigned int default_val)
+{
+	unsigned int val;
+	int ret;
+
+	ret = xenbus_scanf(XBT_NIL, dir, node, "%u", &val);
+	if (ret <= 0)
+		val = default_val;
+
+	return val;
+}
+EXPORT_SYMBOL_GPL(xenbus_read_unsigned);
+
+/* Single printf and write: returns -errno or 0. */
+int xenbus_printf(struct xenbus_transaction t,
+		  const char *dir, const char *node, const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+	char *buf;
+
+	va_start(ap, fmt);
+	buf = kvasprintf(GFP_NOIO | __GFP_HIGH, fmt, ap);
+	va_end(ap);
+
+	if (!buf)
+		return -ENOMEM;
+
+	ret = xenbus_write(t, dir, node, buf);
+
+	kfree(buf);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xenbus_printf);
+
+/* Takes tuples of names, scanf-style args, and void **, NULL terminated. */
+int xenbus_gather(struct xenbus_transaction t, const char *dir, ...)
+{
+	va_list ap;
+	const char *name;
+	int ret = 0;
+
+	va_start(ap, dir);
+	while (ret == 0 && (name = va_arg(ap, char *)) != NULL) {
+		const char *fmt = va_arg(ap, char *);
+		void *result = va_arg(ap, void *);
+		char *p;
+
+		p = xenbus_read(t, dir, name, NULL);
+		if (IS_ERR(p)) {
+			ret = PTR_ERR(p);
+			break;
+		}
+		if (fmt) {
+			if (sscanf(p, fmt, result) == 0)
+				ret = -EINVAL;
+			kfree(p);
+		} else
+			*(char **)result = p;
+	}
+	va_end(ap);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xenbus_gather);
+
+static int xs_watch(const char *path, const char *token)
+{
+	struct kvec iov[2];
+
+	iov[0].iov_base = (void *)path;
+	iov[0].iov_len = strlen(path) + 1;
+	iov[1].iov_base = (void *)token;
+	iov[1].iov_len = strlen(token) + 1;
+
+	return xs_error(xs_talkv(XBT_NIL, XS_WATCH, iov,
+				 ARRAY_SIZE(iov), NULL));
+}
+
+static int xs_unwatch(const char *path, const char *token)
+{
+	struct kvec iov[2];
+
+	iov[0].iov_base = (char *)path;
+	iov[0].iov_len = strlen(path) + 1;
+	iov[1].iov_base = (char *)token;
+	iov[1].iov_len = strlen(token) + 1;
+
+	return xs_error(xs_talkv(XBT_NIL, XS_UNWATCH, iov,
+				 ARRAY_SIZE(iov), NULL));
+}
+
+static struct xenbus_watch *find_watch(const char *token)
+{
+	struct xenbus_watch *i, *cmp;
+
+	cmp = (void *)simple_strtoul(token, NULL, 16);
+
+	list_for_each_entry(i, &watches, list)
+		if (i == cmp)
+			return i;
+
+	return NULL;
+}
+
+int xs_watch_msg(struct xs_watch_event *event)
+{
+	if (count_strings(event->body, event->len) != 2) {
+		kfree(event);
+		return -EINVAL;
+	}
+	event->path = (const char *)event->body;
+	event->token = (const char *)strchr(event->body, '\0') + 1;
+
+	spin_lock(&watches_lock);
+	event->handle = find_watch(event->token);
+	if (event->handle != NULL &&
+			(!event->handle->will_handle ||
+			 event->handle->will_handle(event->handle,
+				 event->path, event->token))) {
+		spin_lock(&watch_events_lock);
+		list_add_tail(&event->list, &watch_events);
+		event->handle->nr_pending++;
+		wake_up(&watch_events_waitq);
+		spin_unlock(&watch_events_lock);
+	} else
+		kfree(event);
+	spin_unlock(&watches_lock);
+
+	return 0;
+}
+
+static void xs_reset_watches(void)
+{
+	int err;
+
+	if (!xen_hvm_domain() || xen_initial_domain())
+		return;
+
+	if (!xenbus_read_unsigned("control",
+				  "platform-feature-xs_reset_watches", 0))
+		return;
+
+	err = xs_error(xs_single(XBT_NIL, XS_RESET_WATCHES, "", NULL));
+	if (err && err != -EEXIST)
+		pr_warn("xs_reset_watches failed: %d\n", err);
+}
+
+/* Register callback to watch this node. */
+int register_xenbus_watch(struct xenbus_watch *watch)
+{
+	/* Pointer in ascii is the token. */
+	char token[sizeof(watch) * 2 + 1];
+	int err;
+
+	sprintf(token, "%lX", (long)watch);
+
+	watch->nr_pending = 0;
+
+	down_read(&xs_watch_rwsem);
+
+	spin_lock(&watches_lock);
+	BUG_ON(find_watch(token));
+	list_add(&watch->list, &watches);
+	spin_unlock(&watches_lock);
+
+	err = xs_watch(watch->node, token);
+
+	if (err) {
+		spin_lock(&watches_lock);
+		list_del(&watch->list);
+		spin_unlock(&watches_lock);
+	}
+
+	up_read(&xs_watch_rwsem);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(register_xenbus_watch);
+
+void unregister_xenbus_watch(struct xenbus_watch *watch)
+{
+	struct xs_watch_event *event, *tmp;
+	char token[sizeof(watch) * 2 + 1];
+	int err;
+
+	sprintf(token, "%lX", (long)watch);
+
+	down_read(&xs_watch_rwsem);
+
+	spin_lock(&watches_lock);
+	BUG_ON(!find_watch(token));
+	list_del(&watch->list);
+	spin_unlock(&watches_lock);
+
+	err = xs_unwatch(watch->node, token);
+	if (err)
+		pr_warn("Failed to release watch %s: %i\n", watch->node, err);
+
+	up_read(&xs_watch_rwsem);
+
+	/* Make sure there are no callbacks running currently (unless
+	   its us) */
+	if (current->pid != xenwatch_pid)
+		mutex_lock(&xenwatch_mutex);
+
+	/* Cancel pending watch events. */
+	spin_lock(&watch_events_lock);
+	if (watch->nr_pending) {
+		list_for_each_entry_safe(event, tmp, &watch_events, list) {
+			if (event->handle != watch)
+				continue;
+			list_del(&event->list);
+			kfree(event);
+		}
+		watch->nr_pending = 0;
+	}
+	spin_unlock(&watch_events_lock);
+
+	if (current->pid != xenwatch_pid)
+		mutex_unlock(&xenwatch_mutex);
+}
+EXPORT_SYMBOL_GPL(unregister_xenbus_watch);
+
+void xs_suspend(void)
+{
+	xs_suspend_enter();
+
+	mutex_lock(&xs_response_mutex);
+	down_write(&xs_watch_rwsem);
+}
+
+void xs_resume(void)
+{
+	struct xenbus_watch *watch;
+	char token[sizeof(watch) * 2 + 1];
+
+	xb_init_comms();
+
+	mutex_unlock(&xs_response_mutex);
+
+	xs_suspend_exit();
+
+	/* No need for watches_lock: the xs_watch_rwsem is sufficient. */
+	list_for_each_entry(watch, &watches, list) {
+		sprintf(token, "%lX", (long)watch);
+		xs_watch(watch->node, token);
+	}
+
+	up_write(&xs_watch_rwsem);
+}
+
+void xs_suspend_cancel(void)
+{
+	up_write(&xs_watch_rwsem);
+	mutex_unlock(&xs_response_mutex);
+
+	xs_suspend_exit();
+}
+
+static int xenwatch_thread(void *unused)
+{
+	struct xs_watch_event *event;
+
+	xenwatch_pid = current->pid;
+
+	for (;;) {
+		wait_event_interruptible(watch_events_waitq,
+					 !list_empty(&watch_events));
+
+		if (kthread_should_stop())
+			break;
+
+		mutex_lock(&xenwatch_mutex);
+
+		spin_lock(&watch_events_lock);
+		event = list_first_entry_or_null(&watch_events,
+				struct xs_watch_event, list);
+		if (event) {
+			list_del(&event->list);
+			event->handle->nr_pending--;
+		}
+		spin_unlock(&watch_events_lock);
+
+		if (event) {
+			event->handle->callback(event->handle, event->path,
+						event->token);
+			kfree(event);
+		}
+
+		mutex_unlock(&xenwatch_mutex);
+	}
+
+	return 0;
+}
+
+/*
+ * Wake up all threads waiting for a xenstore reply. In case of shutdown all
+ * pending replies will be marked as "aborted" in order to let the waiters
+ * return in spite of xenstore possibly no longer being able to reply. This
+ * will avoid blocking shutdown by a thread waiting for xenstore but being
+ * necessary for shutdown processing to proceed.
+ */
+static int xs_reboot_notify(struct notifier_block *nb,
+			    unsigned long code, void *unused)
+{
+	struct xb_req_data *req;
+
+	mutex_lock(&xb_write_mutex);
+	list_for_each_entry(req, &xs_reply_list, list)
+		wake_up(&req->wq);
+	list_for_each_entry(req, &xb_write_list, list)
+		wake_up(&req->wq);
+	mutex_unlock(&xb_write_mutex);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block xs_reboot_nb = {
+	.notifier_call = xs_reboot_notify,
+};
+
+int xs_init(void)
+{
+	int err;
+	struct task_struct *task;
+
+	err = register_reboot_notifier(&xs_reboot_nb);
+	if (err)
+		return err;
+
+	/* Initialize the shared memory rings to talk to xenstored */
+	err = xb_init_comms();
+	if (err)
+		goto err_unregister_reboot_notifier;
+
+	task = kthread_run(xenwatch_thread, NULL, "xenwatch");
+	if (IS_ERR(task)) {
+		err = PTR_ERR(task);
+		goto err_unregister_reboot_notifier;
+	}
+
+	/* shutdown watches for kexec boot */
+	xs_reset_watches();
+
+	return 0;
+
+err_unregister_reboot_notifier:
+	unregister_reboot_notifier(&xs_reboot_nb);
+	return err;
+}
diff --git a/drivers/xen/xenfs/Makefile b/drivers/xen/xenfs/Makefile
new file mode 100644
index 000000000..8490644df
--- /dev/null
+++ b/drivers/xen/xenfs/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_XENFS) += xenfs.o
+
+xenfs-y			  = super.o
+xenfs-$(CONFIG_XEN_DOM0) += xenstored.o
+xenfs-$(CONFIG_XEN_SYMS) += xensyms.o
diff --git a/drivers/xen/xenfs/super.c b/drivers/xen/xenfs/super.c
new file mode 100644
index 000000000..37ea7c5c0
--- /dev/null
+++ b/drivers/xen/xenfs/super.c
@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  xenfs.c - a filesystem for passing info between the a domain and
+ *  the hypervisor.
+ *
+ * 2008-10-07  Alex Zeffertt    Replaced /proc/xen/xenbus with xenfs filesystem
+ *                              and /proc/xen compatibility mount point.
+ *                              Turned xenfs into a loadable module.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/fs_context.h>
+#include <linux/magic.h>
+
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+
+#include "xenfs.h"
+#include "../privcmd.h"
+
+#include <asm/xen/hypervisor.h>
+
+MODULE_DESCRIPTION("Xen filesystem");
+MODULE_LICENSE("GPL");
+
+static ssize_t capabilities_read(struct file *file, char __user *buf,
+				 size_t size, loff_t *off)
+{
+	char *tmp = "";
+
+	if (xen_initial_domain())
+		tmp = "control_d\n";
+
+	return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
+}
+
+static const struct file_operations capabilities_file_ops = {
+	.read = capabilities_read,
+	.llseek = default_llseek,
+};
+
+static int xenfs_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+	static const struct tree_descr xenfs_files[] = {
+		[2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
+		{ "capabilities", &capabilities_file_ops, S_IRUGO },
+		{ "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
+		{""},
+	};
+
+	static const struct tree_descr xenfs_init_files[] = {
+		[2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
+		{ "capabilities", &capabilities_file_ops, S_IRUGO },
+		{ "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
+		{ "xsd_kva", &xsd_kva_file_ops, S_IRUSR|S_IWUSR},
+		{ "xsd_port", &xsd_port_file_ops, S_IRUSR|S_IWUSR},
+#ifdef CONFIG_XEN_SYMS
+		{ "xensyms", &xensyms_ops, S_IRUSR},
+#endif
+		{""},
+	};
+
+	return simple_fill_super(sb, XENFS_SUPER_MAGIC,
+			xen_initial_domain() ? xenfs_init_files : xenfs_files);
+}
+
+static int xenfs_get_tree(struct fs_context *fc)
+{
+	return get_tree_single(fc, xenfs_fill_super);
+}
+
+static const struct fs_context_operations xenfs_context_ops = {
+	.get_tree	= xenfs_get_tree,
+};
+
+static int xenfs_init_fs_context(struct fs_context *fc)
+{
+	fc->ops = &xenfs_context_ops;
+	return 0;
+}
+
+static struct file_system_type xenfs_type = {
+	.owner =	THIS_MODULE,
+	.name =		"xenfs",
+	.init_fs_context = xenfs_init_fs_context,
+	.kill_sb =	kill_anon_super,
+};
+MODULE_ALIAS_FS("xenfs");
+
+static int __init xenfs_init(void)
+{
+	if (xen_domain())
+		return register_filesystem(&xenfs_type);
+
+	return 0;
+}
+
+static void __exit xenfs_exit(void)
+{
+	if (xen_domain())
+		unregister_filesystem(&xenfs_type);
+}
+
+module_init(xenfs_init);
+module_exit(xenfs_exit);
+
diff --git a/drivers/xen/xenfs/xenfs.h b/drivers/xen/xenfs/xenfs.h
new file mode 100644
index 000000000..cfe4874b8
--- /dev/null
+++ b/drivers/xen/xenfs/xenfs.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _XENFS_XENBUS_H
+#define _XENFS_XENBUS_H
+
+extern const struct file_operations xsd_kva_file_ops;
+extern const struct file_operations xsd_port_file_ops;
+extern const struct file_operations xensyms_ops;
+
+#endif	/* _XENFS_XENBUS_H */
diff --git a/drivers/xen/xenfs/xenstored.c b/drivers/xen/xenfs/xenstored.c
new file mode 100644
index 000000000..f59235f9f
--- /dev/null
+++ b/drivers/xen/xenfs/xenstored.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+
+#include <xen/page.h>
+#include <xen/xenbus.h>
+
+#include "xenfs.h"
+
+static ssize_t xsd_read(struct file *file, char __user *buf,
+			    size_t size, loff_t *off)
+{
+	const char *str = (const char *)file->private_data;
+	return simple_read_from_buffer(buf, size, off, str, strlen(str));
+}
+
+static int xsd_release(struct inode *inode, struct file *file)
+{
+	kfree(file->private_data);
+	return 0;
+}
+
+static int xsd_kva_open(struct inode *inode, struct file *file)
+{
+	file->private_data = (void *)kasprintf(GFP_KERNEL, "0x%p",
+					       xen_store_interface);
+	if (!file->private_data)
+		return -ENOMEM;
+	return 0;
+}
+
+static int xsd_kva_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	size_t size = vma->vm_end - vma->vm_start;
+
+	if ((size > PAGE_SIZE) || (vma->vm_pgoff != 0))
+		return -EINVAL;
+
+	if (remap_pfn_range(vma, vma->vm_start,
+			    virt_to_pfn(xen_store_interface),
+			    size, vma->vm_page_prot))
+		return -EAGAIN;
+
+	return 0;
+}
+
+const struct file_operations xsd_kva_file_ops = {
+	.open = xsd_kva_open,
+	.mmap = xsd_kva_mmap,
+	.read = xsd_read,
+	.release = xsd_release,
+};
+
+static int xsd_port_open(struct inode *inode, struct file *file)
+{
+	file->private_data = (void *)kasprintf(GFP_KERNEL, "%d",
+					       xen_store_evtchn);
+	if (!file->private_data)
+		return -ENOMEM;
+	return 0;
+}
+
+const struct file_operations xsd_port_file_ops = {
+	.open = xsd_port_open,
+	.read = xsd_read,
+	.release = xsd_release,
+};
diff --git a/drivers/xen/xenfs/xensyms.c b/drivers/xen/xenfs/xensyms.c
new file mode 100644
index 000000000..088b7f02c
--- /dev/null
+++ b/drivers/xen/xenfs/xensyms.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/seq_file.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/slab.h>
+#include <xen/interface/platform.h>
+#include <asm/xen/hypercall.h>
+#include <xen/xen-ops.h>
+#include "xenfs.h"
+
+
+#define XEN_KSYM_NAME_LEN 127 /* Hypervisor may have different name length */
+
+struct xensyms {
+	struct xen_platform_op op;
+	char *name;
+	uint32_t namelen;
+};
+
+/* Grab next output page from the hypervisor */
+static int xensyms_next_sym(struct xensyms *xs)
+{
+	int ret;
+	struct xenpf_symdata *symdata = &xs->op.u.symdata;
+	uint64_t symnum;
+
+	memset(xs->name, 0, xs->namelen);
+	symdata->namelen = xs->namelen;
+
+	symnum = symdata->symnum;
+
+	ret = HYPERVISOR_platform_op(&xs->op);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * If hypervisor's symbol didn't fit into the buffer then allocate
+	 * a larger buffer and try again.
+	 */
+	if (unlikely(symdata->namelen > xs->namelen)) {
+		kfree(xs->name);
+
+		xs->namelen = symdata->namelen;
+		xs->name = kzalloc(xs->namelen, GFP_KERNEL);
+		if (!xs->name)
+			return -ENOMEM;
+
+		set_xen_guest_handle(symdata->name, xs->name);
+		symdata->symnum = symnum; /* Rewind */
+
+		ret = HYPERVISOR_platform_op(&xs->op);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (symdata->symnum == symnum)
+		/* End of symbols */
+		return 1;
+
+	return 0;
+}
+
+static void *xensyms_start(struct seq_file *m, loff_t *pos)
+{
+	struct xensyms *xs = m->private;
+
+	xs->op.u.symdata.symnum = *pos;
+
+	if (xensyms_next_sym(xs))
+		return NULL;
+
+	return m->private;
+}
+
+static void *xensyms_next(struct seq_file *m, void *p, loff_t *pos)
+{
+	struct xensyms *xs = m->private;
+
+	*pos = xs->op.u.symdata.symnum;
+
+	if (xensyms_next_sym(xs))
+		return NULL;
+
+	return p;
+}
+
+static int xensyms_show(struct seq_file *m, void *p)
+{
+	struct xensyms *xs = m->private;
+	struct xenpf_symdata *symdata = &xs->op.u.symdata;
+
+	seq_printf(m, "%016llx %c %s\n", symdata->address,
+		   symdata->type, xs->name);
+
+	return 0;
+}
+
+static void xensyms_stop(struct seq_file *m, void *p)
+{
+}
+
+static const struct seq_operations xensyms_seq_ops = {
+	.start = xensyms_start,
+	.next = xensyms_next,
+	.show = xensyms_show,
+	.stop = xensyms_stop,
+};
+
+static int xensyms_open(struct inode *inode, struct file *file)
+{
+	struct seq_file *m;
+	struct xensyms *xs;
+	int ret;
+
+	ret = seq_open_private(file, &xensyms_seq_ops,
+			       sizeof(struct xensyms));
+	if (ret)
+		return ret;
+
+	m = file->private_data;
+	xs = m->private;
+
+	xs->namelen = XEN_KSYM_NAME_LEN + 1;
+	xs->name = kzalloc(xs->namelen, GFP_KERNEL);
+	if (!xs->name) {
+		seq_release_private(inode, file);
+		return -ENOMEM;
+	}
+	set_xen_guest_handle(xs->op.u.symdata.name, xs->name);
+	xs->op.cmd = XENPF_get_symbol;
+	xs->op.u.symdata.namelen = xs->namelen;
+
+	return 0;
+}
+
+static int xensyms_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *m = file->private_data;
+	struct xensyms *xs = m->private;
+
+	kfree(xs->name);
+	return seq_release_private(inode, file);
+}
+
+const struct file_operations xensyms_ops = {
+	.open = xensyms_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = xensyms_release
+};
diff --git a/drivers/xen/xlate_mmu.c b/drivers/xen/xlate_mmu.c
new file mode 100644
index 000000000..8efd7b552
--- /dev/null
+++ b/drivers/xen/xlate_mmu.c
@@ -0,0 +1,295 @@
+/*
+ * MMU operations common to all auto-translated physmap guests.
+ *
+ * Copyright (C) 2015 Citrix Systems R&D Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+#include <asm/xen/hypercall.h>
+#include <asm/xen/hypervisor.h>
+
+#include <xen/xen.h>
+#include <xen/xen-ops.h>
+#include <xen/page.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/memory.h>
+#include <xen/balloon.h>
+
+typedef void (*xen_gfn_fn_t)(unsigned long gfn, void *data);
+
+/* Break down the pages in 4KB chunk and call fn for each gfn */
+static void xen_for_each_gfn(struct page **pages, unsigned nr_gfn,
+			     xen_gfn_fn_t fn, void *data)
+{
+	unsigned long xen_pfn = 0;
+	struct page *page;
+	int i;
+
+	for (i = 0; i < nr_gfn; i++) {
+		if ((i % XEN_PFN_PER_PAGE) == 0) {
+			page = pages[i / XEN_PFN_PER_PAGE];
+			xen_pfn = page_to_xen_pfn(page);
+		}
+		fn(pfn_to_gfn(xen_pfn++), data);
+	}
+}
+
+struct remap_data {
+	xen_pfn_t *fgfn; /* foreign domain's gfn */
+	int nr_fgfn; /* Number of foreign gfn left to map */
+	pgprot_t prot;
+	domid_t  domid;
+	struct vm_area_struct *vma;
+	int index;
+	struct page **pages;
+	struct xen_remap_gfn_info *info;
+	int *err_ptr;
+	int mapped;
+
+	/* Hypercall parameters */
+	int h_errs[XEN_PFN_PER_PAGE];
+	xen_ulong_t h_idxs[XEN_PFN_PER_PAGE];
+	xen_pfn_t h_gpfns[XEN_PFN_PER_PAGE];
+
+	int h_iter;	/* Iterator */
+};
+
+static void setup_hparams(unsigned long gfn, void *data)
+{
+	struct remap_data *info = data;
+
+	info->h_idxs[info->h_iter] = *info->fgfn;
+	info->h_gpfns[info->h_iter] = gfn;
+	info->h_errs[info->h_iter] = 0;
+
+	info->h_iter++;
+	info->fgfn++;
+}
+
+static int remap_pte_fn(pte_t *ptep, unsigned long addr, void *data)
+{
+	struct remap_data *info = data;
+	struct page *page = info->pages[info->index++];
+	pte_t pte = pte_mkspecial(pfn_pte(page_to_pfn(page), info->prot));
+	int rc, nr_gfn;
+	uint32_t i;
+	struct xen_add_to_physmap_range xatp = {
+		.domid = DOMID_SELF,
+		.foreign_domid = info->domid,
+		.space = XENMAPSPACE_gmfn_foreign,
+	};
+
+	nr_gfn = min_t(typeof(info->nr_fgfn), XEN_PFN_PER_PAGE, info->nr_fgfn);
+	info->nr_fgfn -= nr_gfn;
+
+	info->h_iter = 0;
+	xen_for_each_gfn(&page, nr_gfn, setup_hparams, info);
+	BUG_ON(info->h_iter != nr_gfn);
+
+	set_xen_guest_handle(xatp.idxs, info->h_idxs);
+	set_xen_guest_handle(xatp.gpfns, info->h_gpfns);
+	set_xen_guest_handle(xatp.errs, info->h_errs);
+	xatp.size = nr_gfn;
+
+	rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap_range, &xatp);
+
+	/* info->err_ptr expect to have one error status per Xen PFN */
+	for (i = 0; i < nr_gfn; i++) {
+		int err = (rc < 0) ? rc : info->h_errs[i];
+
+		*(info->err_ptr++) = err;
+		if (!err)
+			info->mapped++;
+	}
+
+	/*
+	 * Note: The hypercall will return 0 in most of the case if even if
+	 * all the fgmfn are not mapped. We still have to update the pte
+	 * as the userspace may decide to continue.
+	 */
+	if (!rc)
+		set_pte_at(info->vma->vm_mm, addr, ptep, pte);
+
+	return 0;
+}
+
+int xen_xlate_remap_gfn_array(struct vm_area_struct *vma,
+			      unsigned long addr,
+			      xen_pfn_t *gfn, int nr,
+			      int *err_ptr, pgprot_t prot,
+			      unsigned domid,
+			      struct page **pages)
+{
+	int err;
+	struct remap_data data;
+	unsigned long range = DIV_ROUND_UP(nr, XEN_PFN_PER_PAGE) << PAGE_SHIFT;
+
+	/* Kept here for the purpose of making sure code doesn't break
+	   x86 PVOPS */
+	BUG_ON(!((vma->vm_flags & (VM_PFNMAP | VM_IO)) == (VM_PFNMAP | VM_IO)));
+
+	data.fgfn = gfn;
+	data.nr_fgfn = nr;
+	data.prot  = prot;
+	data.domid = domid;
+	data.vma   = vma;
+	data.pages = pages;
+	data.index = 0;
+	data.err_ptr = err_ptr;
+	data.mapped = 0;
+
+	err = apply_to_page_range(vma->vm_mm, addr, range,
+				  remap_pte_fn, &data);
+	return err < 0 ? err : data.mapped;
+}
+EXPORT_SYMBOL_GPL(xen_xlate_remap_gfn_array);
+
+static void unmap_gfn(unsigned long gfn, void *data)
+{
+	struct xen_remove_from_physmap xrp;
+
+	xrp.domid = DOMID_SELF;
+	xrp.gpfn = gfn;
+	(void)HYPERVISOR_memory_op(XENMEM_remove_from_physmap, &xrp);
+}
+
+int xen_xlate_unmap_gfn_range(struct vm_area_struct *vma,
+			      int nr, struct page **pages)
+{
+	xen_for_each_gfn(pages, nr, unmap_gfn, NULL);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_xlate_unmap_gfn_range);
+
+struct map_balloon_pages {
+	xen_pfn_t *pfns;
+	unsigned int idx;
+};
+
+static void setup_balloon_gfn(unsigned long gfn, void *data)
+{
+	struct map_balloon_pages *info = data;
+
+	info->pfns[info->idx++] = gfn;
+}
+
+/**
+ * xen_xlate_map_ballooned_pages - map a new set of ballooned pages
+ * @gfns: returns the array of corresponding GFNs
+ * @virt: returns the virtual address of the mapped region
+ * @nr_grant_frames: number of GFNs
+ * @return 0 on success, error otherwise
+ *
+ * This allocates a set of ballooned pages and maps them into the
+ * kernel's address space.
+ */
+int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, void **virt,
+					 unsigned long nr_grant_frames)
+{
+	struct page **pages;
+	xen_pfn_t *pfns;
+	void *vaddr;
+	struct map_balloon_pages data;
+	int rc;
+	unsigned long nr_pages;
+
+	BUG_ON(nr_grant_frames == 0);
+	nr_pages = DIV_ROUND_UP(nr_grant_frames, XEN_PFN_PER_PAGE);
+	pages = kzalloc_objs(pages[0], nr_pages);
+	if (!pages)
+		return -ENOMEM;
+
+	pfns = kzalloc_objs(pfns[0], nr_grant_frames);
+	if (!pfns) {
+		kfree(pages);
+		return -ENOMEM;
+	}
+	rc = xen_alloc_unpopulated_pages(nr_pages, pages);
+	if (rc) {
+		pr_warn("%s Couldn't balloon alloc %ld pages rc:%d\n", __func__,
+			nr_pages, rc);
+		kfree(pages);
+		kfree(pfns);
+		return rc;
+	}
+
+	data.pfns = pfns;
+	data.idx = 0;
+	xen_for_each_gfn(pages, nr_grant_frames, setup_balloon_gfn, &data);
+
+	vaddr = vmap(pages, nr_pages, 0, PAGE_KERNEL);
+	if (!vaddr) {
+		pr_warn("%s Couldn't map %ld pages rc:%d\n", __func__,
+			nr_pages, rc);
+		xen_free_unpopulated_pages(nr_pages, pages);
+		kfree(pages);
+		kfree(pfns);
+		return -ENOMEM;
+	}
+	kfree(pages);
+
+	*gfns = pfns;
+	*virt = vaddr;
+
+	return 0;
+}
+
+struct remap_pfn {
+	struct mm_struct *mm;
+	struct page **pages;
+	pgprot_t prot;
+	unsigned long i;
+};
+
+static int remap_pfn_fn(pte_t *ptep, unsigned long addr, void *data)
+{
+	struct remap_pfn *r = data;
+	struct page *page = r->pages[r->i];
+	pte_t pte = pte_mkspecial(pfn_pte(page_to_pfn(page), r->prot));
+
+	set_pte_at(r->mm, addr, ptep, pte);
+	r->i++;
+
+	return 0;
+}
+
+/* Used by the privcmd module, but has to be built-in on ARM */
+int xen_remap_vma_range(struct vm_area_struct *vma, unsigned long addr, unsigned long len)
+{
+	struct remap_pfn r = {
+		.mm = vma->vm_mm,
+		.pages = vma->vm_private_data,
+		.prot = vma->vm_page_prot,
+	};
+
+	return apply_to_page_range(vma->vm_mm, addr, len, remap_pfn_fn, &r);
+}
+EXPORT_SYMBOL_GPL(xen_remap_vma_range);