Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 179 insertions, 0 deletions

diff --git a/Documentation/misc-devices/uacce.rst b/Documentation/misc-devices/uacce.rst
new file mode 100644
index 000000000..5f78d413e
--- /dev/null
+++ b/Documentation/misc-devices/uacce.rst
@@ -0,0 +1,179 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Uacce (Unified/User-space-access-intended Accelerator Framework)
+================================================================
+
+Introduction
+------------
+
+Uacce (Unified/User-space-access-intended Accelerator Framework) targets to
+provide Shared Virtual Addressing (SVA) between accelerators and processes.
+So accelerator can access any data structure of the main cpu.
+This differs from the data sharing between cpu and io device, which share
+only data content rather than address.
+Because of the unified address, hardware and user space of process can
+share the same virtual address in the communication.
+Uacce takes the hardware accelerator as a heterogeneous processor, while
+IOMMU share the same CPU page tables and as a result the same translation
+from va to pa.
+
+::
+
+         __________________________       __________________________
+        |                          |     |                          |
+        |  User application (CPU)  |     |   Hardware Accelerator   |
+        |__________________________|     |__________________________|
+
+                     |                                 |
+                     | va                              | va
+                     V                                 V
+                 __________                        __________
+                |          |                      |          |
+                |   MMU    |                      |  IOMMU   |
+                |__________|                      |__________|
+                     |                                 |
+                     |                                 |
+                     V pa                              V pa
+                 _______________________________________
+                |                                       |
+                |              Memory                   |
+                |_______________________________________|
+
+
+
+Architecture
+------------
+
+Uacce is the kernel module, taking charge of iommu and address sharing.
+The user drivers and libraries are called WarpDrive.
+
+The uacce device, built around the IOMMU SVA API, can access multiple
+address spaces, including the one without PASID.
+
+A virtual concept, queue, is used for the communication. It provides a
+FIFO-like interface. And it maintains a unified address space between the
+application and all involved hardware.
+
+::
+
+                             ___________________                  ________________
+                            |                   |   user API     |                |
+                            | WarpDrive library | ------------>  |  user driver   |
+                            |___________________|                |________________|
+                                     |                                    |
+                                     |                                    |
+                                     | queue fd                           |
+                                     |                                    |
+                                     |                                    |
+                                     v                                    |
+     ___________________         _________                                |
+    |                   |       |         |                               | mmap memory
+    | Other framework   |       |  uacce  |                               | r/w interface
+    | crypto/nic/others |       |_________|                               |
+    |___________________|                                                 |
+             |                       |                                    |
+             | register              | register                           |
+             |                       |                                    |
+             |                       |                                    |
+             |                _________________       __________          |
+             |               |                 |     |          |         |
+              -------------  |  Device Driver  |     |  IOMMU   |         |
+                             |_________________|     |__________|         |
+                                     |                                    |
+                                     |                                    V
+                                     |                            ___________________
+                                     |                           |                   |
+                                     --------------------------  |  Device(Hardware) |
+                                                                 |___________________|
+
+
+How does it work
+----------------
+
+Uacce uses mmap and IOMMU to play the trick.
+
+Uacce creates a chrdev for every device registered to it. New queue is
+created when user application open the chrdev. The file descriptor is used
+as the user handle of the queue.
+The accelerator device present itself as an Uacce object, which exports as
+a chrdev to the user space. The user application communicates with the
+hardware by ioctl (as control path) or share memory (as data path).
+
+The control path to the hardware is via file operation, while data path is
+via mmap space of the queue fd.
+
+The queue file address space:
+
+::
+
+   /**
+   * enum uacce_qfrt: qfrt type
+   * @UACCE_QFRT_MMIO: device mmio region
+   * @UACCE_QFRT_DUS: device user share region
+   */
+  enum uacce_qfrt {
+          UACCE_QFRT_MMIO = 0,
+          UACCE_QFRT_DUS = 1,
+  };
+
+All regions are optional and differ from device type to type.
+Each region can be mmapped only once, otherwise -EEXIST returns.
+
+The device mmio region is mapped to the hardware mmio space. It is generally
+used for doorbell or other notification to the hardware. It is not fast enough
+as data channel.
+
+The device user share region is used for share data buffer between user process
+and device.
+
+
+The Uacce register API
+----------------------
+
+The register API is defined in uacce.h.
+
+::
+
+  struct uacce_interface {
+    char name[UACCE_MAX_NAME_SIZE];
+    unsigned int flags;
+    const struct uacce_ops *ops;
+  };
+
+According to the IOMMU capability, uacce_interface flags can be:
+
+::
+
+  /**
+   * UACCE Device flags:
+   * UACCE_DEV_SVA: Shared Virtual Addresses
+   *              Support PASID
+   *              Support device page faults (PCI PRI or SMMU Stall)
+   */
+  #define UACCE_DEV_SVA               BIT(0)
+
+  struct uacce_device *uacce_alloc(struct device *parent,
+                                   struct uacce_interface *interface);
+  int uacce_register(struct uacce_device *uacce);
+  void uacce_remove(struct uacce_device *uacce);
+
+uacce_register results can be:
+
+a. If uacce module is not compiled, ERR_PTR(-ENODEV)
+
+b. Succeed with the desired flags
+
+c. Succeed with the negotiated flags, for example
+
+  uacce_interface.flags = UACCE_DEV_SVA but uacce->flags = ~UACCE_DEV_SVA
+
+  So user driver need check return value as well as the negotiated uacce->flags.
+
+
+The user driver
+---------------
+
+The queue file mmap space will need a user driver to wrap the communication
+protocol. Uacce provides some attributes in sysfs for the user driver to
+match the right accelerator accordingly.
+More details in Documentation/ABI/testing/sysfs-driver-uacce.