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
  ...

6 files changed, 1293 insertions, 0 deletions

diff --git a/drivers/gpu/drm/hyperv/Kconfig b/drivers/gpu/drm/hyperv/Kconfig
new file mode 100644
index 000000000..86234f6a7
--- /dev/null
+++ b/drivers/gpu/drm/hyperv/Kconfig
@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config DRM_HYPERV
+	tristate "DRM Support for Hyper-V synthetic video device"
+	depends on DRM && PCI && HYPERV_VMBUS
+	select DRM_CLIENT_SELECTION
+	select DRM_KMS_HELPER
+	select DRM_GEM_SHMEM_HELPER
+	help
+	 This is a KMS driver for Hyper-V synthetic video device. Choose this
+	 option if you would like to enable drm driver for Hyper-V virtual
+	 machine. Unselect Hyper-V framebuffer driver (CONFIG_FB_HYPERV) so
+	 that DRM driver is used by default.
+
+	 If M is selected the module will be called hyperv_drm.
diff --git a/drivers/gpu/drm/hyperv/Makefile b/drivers/gpu/drm/hyperv/Makefile
new file mode 100644
index 000000000..265f12f2c
--- /dev/null
+++ b/drivers/gpu/drm/hyperv/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+hyperv_drm-y := \
+	hyperv_drm_drv.o \
+	hyperv_drm_modeset.o \
+	hyperv_drm_proto.o
+
+obj-$(CONFIG_DRM_HYPERV) += hyperv_drm.o
diff --git a/drivers/gpu/drm/hyperv/hyperv_drm.h b/drivers/gpu/drm/hyperv/hyperv_drm.h
new file mode 100644
index 000000000..78136ec2c
--- /dev/null
+++ b/drivers/gpu/drm/hyperv/hyperv_drm.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2021 Microsoft
+ */
+
+#ifndef _HYPERV_DRM_H_
+#define _HYPERV_DRM_H_
+
+#define VMBUS_MAX_PACKET_SIZE 0x4000
+
+struct hv_drm_device {
+	/* drm */
+	struct drm_device dev;
+	struct drm_plane plane;
+	struct drm_crtc crtc;
+	struct drm_encoder encoder;
+	struct drm_connector connector;
+
+	/* mode */
+	u32 screen_width_max;
+	u32 screen_height_max;
+	u32 preferred_width;
+	u32 preferred_height;
+	u32 screen_depth;
+
+	/* hw */
+	struct resource *mem;
+	void __iomem *vram;
+	unsigned long fb_base;
+	unsigned long fb_size;
+	struct completion wait;
+	u32 synthvid_version;
+	u32 mmio_megabytes;
+	bool dirt_needed;
+
+	u8 init_buf[VMBUS_MAX_PACKET_SIZE];
+	u8 recv_buf[VMBUS_MAX_PACKET_SIZE];
+
+	struct hv_device *hdev;
+};
+
+#define to_hv_drm(_dev) container_of(_dev, struct hv_drm_device, dev)
+
+/* hyperv_drm_modeset */
+int hv_drm_mode_config_init(struct hv_drm_device *hv);
+
+/* hyperv_drm_proto */
+int hv_drm_update_vram_location(struct hv_device *hdev, phys_addr_t vram_pp);
+int hv_drm_update_situation(struct hv_device *hdev, u8 active, u32 bpp,
+			    u32 w, u32 h, u32 pitch);
+int hv_drm_hide_hw_ptr(struct hv_device *hdev);
+int hv_drm_update_dirt(struct hv_device *hdev, struct drm_rect *rect);
+int hv_drm_connect_vsp(struct hv_device *hdev);
+
+#endif
diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_drv.c b/drivers/gpu/drm/hyperv/hyperv_drm_drv.c
new file mode 100644
index 000000000..0efd0593d
--- /dev/null
+++ b/drivers/gpu/drm/hyperv/hyperv_drm_drv.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2021 Microsoft
+ */
+
+#include <linux/aperture.h>
+#include <linux/efi.h>
+#include <linux/hyperv.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+
+#include <drm/clients/drm_client_setup.h>
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fbdev_shmem.h>
+#include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_print.h>
+#include <drm/drm_simple_kms_helper.h>
+
+#include "hyperv_drm.h"
+
+#define DRIVER_NAME "hyperv_drm"
+#define DRIVER_DESC "DRM driver for Hyper-V synthetic video device"
+#define DRIVER_MAJOR 1
+#define DRIVER_MINOR 0
+
+DEFINE_DRM_GEM_FOPS(hv_drm_fops);
+
+static struct drm_driver hv_drm_driver = {
+	.driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_ATOMIC,
+
+	.name		 = DRIVER_NAME,
+	.desc		 = DRIVER_DESC,
+	.major		 = DRIVER_MAJOR,
+	.minor		 = DRIVER_MINOR,
+
+	.fops		 = &hv_drm_fops,
+	DRM_GEM_SHMEM_DRIVER_OPS,
+	DRM_FBDEV_SHMEM_DRIVER_OPS,
+};
+
+static int hv_drm_pci_probe(struct pci_dev *pdev,
+			    const struct pci_device_id *ent)
+{
+	return 0;
+}
+
+static void hv_drm_pci_remove(struct pci_dev *pdev)
+{
+}
+
+static const struct pci_device_id hv_drm_pci_tbl[] = {
+	{
+		PCI_VDEVICE_SUB(MICROSOFT, PCI_DEVICE_ID_HYPERV_VIDEO,
+				0, 0),
+	},
+	{ /* end of list */ }
+};
+MODULE_DEVICE_TABLE(pci, hv_drm_pci_tbl);
+
+/*
+ * PCI stub to support gen1 VM.
+ */
+static struct pci_driver hv_drm_pci_driver = {
+	.name =		KBUILD_MODNAME,
+	.id_table =	hv_drm_pci_tbl,
+	.probe =	hv_drm_pci_probe,
+	.remove =	hv_drm_pci_remove,
+};
+
+static int hv_drm_setup_vram(struct hv_drm_device *hv,
+			     struct hv_device *hdev)
+{
+	struct drm_device *dev = &hv->dev;
+	int ret;
+
+	hv->fb_size = (unsigned long)hv->mmio_megabytes * 1024 * 1024;
+
+	ret = vmbus_allocate_mmio(&hv->mem, hdev, 0, -1, hv->fb_size, 0x100000,
+				  true);
+	if (ret) {
+		drm_err(dev, "Failed to allocate mmio\n");
+		return -ENOMEM;
+	}
+
+	/*
+	 * Map the VRAM cacheable for performance. This is also required for VM
+	 * connect to display properly for ARM64 Linux VM, as the host also maps
+	 * the VRAM cacheable.
+	 */
+	hv->vram = ioremap_cache(hv->mem->start, hv->fb_size);
+	if (!hv->vram) {
+		drm_err(dev, "Failed to map vram\n");
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	hv->fb_base = hv->mem->start;
+	return 0;
+
+error:
+	vmbus_free_mmio(hv->mem->start, hv->fb_size);
+	return ret;
+}
+
+static int hv_drm_vmbus_probe(struct hv_device *hdev,
+			      const struct hv_vmbus_device_id *dev_id)
+{
+	struct hv_drm_device *hv;
+	struct drm_device *dev;
+	int ret;
+
+	hv = devm_drm_dev_alloc(&hdev->device, &hv_drm_driver,
+				struct hv_drm_device, dev);
+	if (IS_ERR(hv))
+		return PTR_ERR(hv);
+
+	dev = &hv->dev;
+	init_completion(&hv->wait);
+	hv_set_drvdata(hdev, hv);
+	hv->hdev = hdev;
+
+	ret = hv_drm_connect_vsp(hdev);
+	if (ret) {
+		drm_err(dev, "Failed to connect to vmbus.\n");
+		goto err_hv_set_drv_data;
+	}
+
+	aperture_remove_all_conflicting_devices(hv_drm_driver.name);
+
+	ret = hv_drm_setup_vram(hv, hdev);
+	if (ret)
+		goto err_vmbus_close;
+
+	/*
+	 * Should be done only once during init and resume. Failing to update
+	 * vram location is not fatal. Device will update dirty area till
+	 * preferred resolution only.
+	 */
+	ret = hv_drm_update_vram_location(hdev, hv->fb_base);
+	if (ret)
+		drm_warn(dev, "Failed to update vram location.\n");
+
+	ret = hv_drm_mode_config_init(hv);
+	if (ret)
+		goto err_free_mmio;
+
+	ret = drm_dev_register(dev, 0);
+	if (ret) {
+		drm_err(dev, "Failed to register drm driver.\n");
+		goto err_free_mmio;
+	}
+
+	/* If DRM panic path is stubbed out VMBus code must do the unload */
+	if (IS_ENABLED(CONFIG_DRM_PANIC))
+		vmbus_set_skip_unload(true);
+
+	drm_client_setup(dev, NULL);
+
+	return 0;
+
+err_free_mmio:
+	iounmap(hv->vram);
+	vmbus_free_mmio(hv->mem->start, hv->fb_size);
+err_vmbus_close:
+	vmbus_close(hdev->channel);
+err_hv_set_drv_data:
+	hv_set_drvdata(hdev, NULL);
+	return ret;
+}
+
+static void hv_drm_vmbus_remove(struct hv_device *hdev)
+{
+	struct drm_device *dev = hv_get_drvdata(hdev);
+	struct hv_drm_device *hv = to_hv_drm(dev);
+
+	vmbus_set_skip_unload(false);
+	drm_dev_unplug(dev);
+	drm_atomic_helper_shutdown(dev);
+	vmbus_close(hdev->channel);
+	hv_set_drvdata(hdev, NULL);
+
+	iounmap(hv->vram);
+	vmbus_free_mmio(hv->mem->start, hv->fb_size);
+}
+
+static void hv_drm_vmbus_shutdown(struct hv_device *hdev)
+{
+	drm_atomic_helper_shutdown(hv_get_drvdata(hdev));
+}
+
+static int hv_drm_vmbus_suspend(struct hv_device *hdev)
+{
+	struct drm_device *dev = hv_get_drvdata(hdev);
+	int ret;
+
+	ret = drm_mode_config_helper_suspend(dev);
+	if (ret)
+		return ret;
+
+	vmbus_close(hdev->channel);
+
+	return 0;
+}
+
+static int hv_drm_vmbus_resume(struct hv_device *hdev)
+{
+	struct drm_device *dev = hv_get_drvdata(hdev);
+	struct hv_drm_device *hv = to_hv_drm(dev);
+	int ret;
+
+	ret = hv_drm_connect_vsp(hdev);
+	if (ret)
+		return ret;
+
+	ret = hv_drm_update_vram_location(hdev, hv->fb_base);
+	if (ret)
+		return ret;
+
+	return drm_mode_config_helper_resume(dev);
+}
+
+static const struct hv_vmbus_device_id hv_drm_vmbus_tbl[] = {
+	/* Synthetic Video Device GUID */
+	{HV_SYNTHVID_GUID},
+	{}
+};
+MODULE_DEVICE_TABLE(vmbus, hv_drm_vmbus_tbl);
+
+static struct hv_driver hv_drm_hv_driver = {
+	.name = KBUILD_MODNAME,
+	.id_table = hv_drm_vmbus_tbl,
+	.probe = hv_drm_vmbus_probe,
+	.remove = hv_drm_vmbus_remove,
+	.shutdown = hv_drm_vmbus_shutdown,
+	.suspend = hv_drm_vmbus_suspend,
+	.resume = hv_drm_vmbus_resume,
+	.driver = {
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+
+static int __init hv_drm_init(void)
+{
+	int ret;
+
+	if (drm_firmware_drivers_only())
+		return -ENODEV;
+
+	ret = pci_register_driver(&hv_drm_pci_driver);
+	if (ret != 0)
+		return ret;
+
+	ret = vmbus_driver_register(&hv_drm_hv_driver);
+	if (ret)
+		pci_unregister_driver(&hv_drm_pci_driver);
+
+	return ret;
+}
+
+static void __exit hv_drm_exit(void)
+{
+	vmbus_driver_unregister(&hv_drm_hv_driver);
+	pci_unregister_driver(&hv_drm_pci_driver);
+}
+
+module_init(hv_drm_init);
+module_exit(hv_drm_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Deepak Rawat <drawat.floss@gmail.com>");
+MODULE_DESCRIPTION("DRM driver for Hyper-V synthetic video device");
diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c b/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
new file mode 100644
index 000000000..1855749c1
--- /dev/null
+++ b/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2021 Microsoft
+ */
+
+#include <linux/hyperv.h>
+
+#include <drm/drm_atomic.h>
+#include <drm/drm_crtc_helper.h>
+#include <drm/drm_damage_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_edid.h>
+#include <drm/drm_format_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_gem_atomic_helper.h>
+#include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_probe_helper.h>
+#include <drm/drm_panic.h>
+#include <drm/drm_plane.h>
+#include <drm/drm_print.h>
+#include <drm/drm_vblank.h>
+#include <drm/drm_vblank_helper.h>
+
+#include "hyperv_drm.h"
+
+static int hv_drm_blit_to_vram_rect(struct drm_framebuffer *fb,
+				    const struct iosys_map *vmap,
+				    struct drm_rect *rect)
+{
+	struct hv_drm_device *hv = to_hv_drm(fb->dev);
+	struct iosys_map dst = IOSYS_MAP_INIT_VADDR_IOMEM(hv->vram);
+	int idx;
+
+	if (!drm_dev_enter(&hv->dev, &idx))
+		return -ENODEV;
+
+	iosys_map_incr(&dst, drm_fb_clip_offset(fb->pitches[0], fb->format, rect));
+	drm_fb_memcpy(&dst, fb->pitches, vmap, fb, rect);
+
+	drm_dev_exit(idx);
+
+	return 0;
+}
+
+static int hv_drm_connector_get_modes(struct drm_connector *connector)
+{
+	struct hv_drm_device *hv = to_hv_drm(connector->dev);
+	int count;
+
+	count = drm_add_modes_noedid(connector,
+				     connector->dev->mode_config.max_width,
+				     connector->dev->mode_config.max_height);
+	drm_set_preferred_mode(connector, hv->preferred_width,
+			       hv->preferred_height);
+
+	return count;
+}
+
+static const struct drm_connector_helper_funcs hv_drm_connector_helper_funcs = {
+	.get_modes = hv_drm_connector_get_modes,
+};
+
+static const struct drm_connector_funcs hv_drm_connector_funcs = {
+	.fill_modes = drm_helper_probe_single_connector_modes,
+	.destroy = drm_connector_cleanup,
+	.reset = drm_atomic_helper_connector_reset,
+	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+static inline int hv_drm_conn_init(struct hv_drm_device *hv)
+{
+	drm_connector_helper_add(&hv->connector, &hv_drm_connector_helper_funcs);
+	return drm_connector_init(&hv->dev, &hv->connector,
+				  &hv_drm_connector_funcs,
+				  DRM_MODE_CONNECTOR_VIRTUAL);
+}
+
+static int hv_drm_check_size(struct hv_drm_device *hv, int w, int h,
+			     struct drm_framebuffer *fb)
+{
+	u32 pitch = w * (hv->screen_depth / 8);
+
+	if (fb)
+		pitch = fb->pitches[0];
+
+	if (pitch * h > hv->fb_size)
+		return -EINVAL;
+
+	return 0;
+}
+
+static const uint32_t hv_drm_formats[] = {
+	DRM_FORMAT_XRGB8888,
+};
+
+static const uint64_t hv_drm_modifiers[] = {
+	DRM_FORMAT_MOD_LINEAR,
+	DRM_FORMAT_MOD_INVALID
+};
+
+static void hv_drm_crtc_helper_atomic_enable(struct drm_crtc *crtc,
+					     struct drm_atomic_commit *state)
+{
+	struct hv_drm_device *hv = to_hv_drm(crtc->dev);
+	struct drm_plane *plane = &hv->plane;
+	struct drm_plane_state *plane_state = plane->state;
+	struct drm_crtc_state *crtc_state = crtc->state;
+
+	hv_drm_hide_hw_ptr(hv->hdev);
+	hv_drm_update_situation(hv->hdev, 1,  hv->screen_depth,
+				crtc_state->mode.hdisplay,
+				crtc_state->mode.vdisplay,
+				plane_state->fb->pitches[0]);
+
+	drm_crtc_vblank_on(crtc);
+}
+
+static const struct drm_crtc_helper_funcs hv_drm_crtc_helper_funcs = {
+	.atomic_check = drm_crtc_helper_atomic_check,
+	.atomic_flush = drm_crtc_vblank_atomic_flush,
+	.atomic_enable = hv_drm_crtc_helper_atomic_enable,
+	.atomic_disable = drm_crtc_vblank_atomic_disable,
+};
+
+static const struct drm_crtc_funcs hv_drm_crtc_funcs = {
+	.reset = drm_atomic_helper_crtc_reset,
+	.destroy = drm_crtc_cleanup,
+	.set_config = drm_atomic_helper_set_config,
+	.page_flip = drm_atomic_helper_page_flip,
+	.atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
+	DRM_CRTC_VBLANK_TIMER_FUNCS,
+};
+
+static int hv_drm_plane_atomic_check(struct drm_plane *plane,
+				     struct drm_atomic_commit *state)
+{
+	struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane);
+	struct hv_drm_device *hv = to_hv_drm(plane->dev);
+	struct drm_framebuffer *fb = plane_state->fb;
+	struct drm_crtc *crtc = plane_state->crtc;
+	struct drm_crtc_state *crtc_state = NULL;
+	int ret;
+
+	if (crtc)
+		crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
+
+	ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
+						  DRM_PLANE_NO_SCALING,
+						  DRM_PLANE_NO_SCALING,
+						  false, false);
+	if (ret)
+		return ret;
+
+	if (!plane_state->visible)
+		return 0;
+
+	if (fb->pitches[0] * fb->height > hv->fb_size) {
+		drm_err(&hv->dev, "fb size requested by %s for %dX%d (pitch %d) greater than %ld\n",
+			current->comm, fb->width, fb->height, fb->pitches[0], hv->fb_size);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void hv_drm_plane_atomic_update(struct drm_plane *plane,
+				       struct drm_atomic_commit *state)
+{
+	struct hv_drm_device *hv = to_hv_drm(plane->dev);
+	struct drm_plane_state *old_state = drm_atomic_get_old_plane_state(state, plane);
+	struct drm_plane_state *new_state = drm_atomic_get_new_plane_state(state, plane);
+	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(new_state);
+	struct drm_rect damage;
+	struct drm_rect dst_clip;
+	struct drm_atomic_helper_damage_iter iter;
+
+	drm_atomic_helper_damage_iter_init(&iter, old_state, new_state);
+	drm_atomic_for_each_plane_damage(&iter, &damage) {
+		dst_clip = new_state->dst;
+
+		if (!drm_rect_intersect(&dst_clip, &damage))
+			continue;
+
+		hv_drm_blit_to_vram_rect(new_state->fb, &shadow_plane_state->data[0], &damage);
+		hv_drm_update_dirt(hv->hdev, &damage);
+	}
+}
+
+static int hv_drm_plane_get_scanout_buffer(struct drm_plane *plane,
+					   struct drm_scanout_buffer *sb)
+{
+	struct hv_drm_device *hv = to_hv_drm(plane->dev);
+	struct iosys_map map = IOSYS_MAP_INIT_VADDR_IOMEM(hv->vram);
+
+	if (plane->state && plane->state->fb) {
+		sb->format = plane->state->fb->format;
+		sb->width = plane->state->fb->width;
+		sb->height = plane->state->fb->height;
+		sb->pitch[0] = plane->state->fb->pitches[0];
+		sb->map[0] = map;
+		return 0;
+	}
+	return -ENODEV;
+}
+
+static void hv_drm_plane_panic_flush(struct drm_plane *plane)
+{
+	struct hv_drm_device *hv = to_hv_drm(plane->dev);
+	struct drm_rect rect;
+
+	if (plane->state && plane->state->fb) {
+		rect.x1 = 0;
+		rect.y1 = 0;
+		rect.x2 = plane->state->fb->width;
+		rect.y2 = plane->state->fb->height;
+
+		hv_drm_update_dirt(hv->hdev, &rect);
+	}
+
+	vmbus_initiate_unload(true);
+}
+
+static const struct drm_plane_helper_funcs hv_drm_plane_helper_funcs = {
+	DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
+	.atomic_check = hv_drm_plane_atomic_check,
+	.atomic_update = hv_drm_plane_atomic_update,
+	.get_scanout_buffer = hv_drm_plane_get_scanout_buffer,
+	.panic_flush = hv_drm_plane_panic_flush,
+};
+
+static const struct drm_plane_funcs hv_drm_plane_funcs = {
+	.update_plane		= drm_atomic_helper_update_plane,
+	.disable_plane		= drm_atomic_helper_disable_plane,
+	.destroy		= drm_plane_cleanup,
+	DRM_GEM_SHADOW_PLANE_FUNCS,
+};
+
+static const struct drm_encoder_funcs hv_drm_simple_encoder_funcs_cleanup = {
+	.destroy = drm_encoder_cleanup,
+};
+
+static inline int hv_drm_pipe_init(struct hv_drm_device *hv)
+{
+	struct drm_device *dev = &hv->dev;
+	struct drm_encoder *encoder = &hv->encoder;
+	struct drm_plane *plane = &hv->plane;
+	struct drm_crtc *crtc = &hv->crtc;
+	struct drm_connector *connector = &hv->connector;
+	int ret;
+
+	ret = drm_universal_plane_init(dev, plane, 0,
+				       &hv_drm_plane_funcs,
+				       hv_drm_formats, ARRAY_SIZE(hv_drm_formats),
+				       hv_drm_modifiers,
+				       DRM_PLANE_TYPE_PRIMARY, NULL);
+	if (ret)
+		return ret;
+	drm_plane_helper_add(plane, &hv_drm_plane_helper_funcs);
+	drm_plane_enable_fb_damage_clips(plane);
+
+	ret = drm_crtc_init_with_planes(dev, crtc, plane, NULL,
+					&hv_drm_crtc_funcs, NULL);
+	if (ret)
+		return ret;
+	drm_crtc_helper_add(crtc, &hv_drm_crtc_helper_funcs);
+
+	encoder->possible_crtcs = drm_crtc_mask(crtc);
+	ret = drm_encoder_init(dev, encoder,
+			       &hv_drm_simple_encoder_funcs_cleanup,
+			       DRM_MODE_ENCODER_NONE, NULL);
+	if (ret)
+		return ret;
+
+	ret = hv_drm_conn_init(hv);
+	if (ret) {
+		drm_err(dev, "Failed to initialized connector.\n");
+		return ret;
+	}
+
+	return drm_connector_attach_encoder(connector, encoder);
+}
+
+static enum drm_mode_status
+hv_drm_mode_valid(struct drm_device *dev,
+		  const struct drm_display_mode *mode)
+{
+	struct hv_drm_device *hv = to_hv_drm(dev);
+
+	if (hv_drm_check_size(hv, mode->hdisplay, mode->vdisplay, NULL))
+		return MODE_BAD;
+
+	return MODE_OK;
+}
+
+static const struct drm_mode_config_funcs hv_drm_mode_config_funcs = {
+	.fb_create = drm_gem_fb_create_with_dirty,
+	.mode_valid = hv_drm_mode_valid,
+	.atomic_check = drm_atomic_helper_check,
+	.atomic_commit = drm_atomic_helper_commit,
+};
+
+int hv_drm_mode_config_init(struct hv_drm_device *hv)
+{
+	struct drm_device *dev = &hv->dev;
+	int ret;
+
+	ret = drmm_mode_config_init(dev);
+	if (ret) {
+		drm_err(dev, "Failed to initialized mode setting.\n");
+		return ret;
+	}
+
+	dev->mode_config.min_width = 0;
+	dev->mode_config.min_height = 0;
+	dev->mode_config.max_width = hv->screen_width_max;
+	dev->mode_config.max_height = hv->screen_height_max;
+
+	dev->mode_config.preferred_depth = hv->screen_depth;
+	dev->mode_config.prefer_shadow = 0;
+
+	dev->mode_config.funcs = &hv_drm_mode_config_funcs;
+
+	ret = hv_drm_pipe_init(hv);
+	if (ret) {
+		drm_err(dev, "Failed to initialized pipe.\n");
+		return ret;
+	}
+
+	ret = drm_vblank_init(dev, 1);
+	if (ret)
+		return ret;
+
+	drm_mode_config_reset(dev);
+
+	return 0;
+}
diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
new file mode 100644
index 000000000..f0ef627b4
--- /dev/null
+++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
@@ -0,0 +1,604 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2021 Microsoft
+ */
+
+#include <linux/hyperv.h>
+
+#include <drm/drm_print.h>
+#include <drm/drm_simple_kms_helper.h>
+
+#include "hyperv_drm.h"
+
+#define VMBUS_RING_BUFSIZE VMBUS_RING_SIZE(256 * 1024)
+#define VMBUS_VSP_TIMEOUT (10 * HZ)
+
+#define SYNTHVID_VERSION(major, minor) ((minor) << 16 | (major))
+#define SYNTHVID_VER_GET_MAJOR(ver) (ver & 0x0000ffff)
+#define SYNTHVID_VER_GET_MINOR(ver) ((ver & 0xffff0000) >> 16)
+
+/* Support for VERSION_WIN7 is removed. #define is retained for reference. */
+#define SYNTHVID_VERSION_WIN7 SYNTHVID_VERSION(3, 0)
+#define SYNTHVID_VERSION_WIN8 SYNTHVID_VERSION(3, 2)
+#define SYNTHVID_VERSION_WIN10 SYNTHVID_VERSION(3, 5)
+
+#define SYNTHVID_DEPTH_WIN8 32
+#define SYNTHVID_WIDTH_WIN8 1600
+#define SYNTHVID_HEIGHT_WIN8 1200
+#define SYNTHVID_FB_SIZE_WIN8 (8 * 1024 * 1024)
+
+enum pipe_msg_type {
+	PIPE_MSG_INVALID,
+	PIPE_MSG_DATA,
+	PIPE_MSG_MAX
+};
+
+enum synthvid_msg_type {
+	SYNTHVID_ERROR			= 0,
+	SYNTHVID_VERSION_REQUEST	= 1,
+	SYNTHVID_VERSION_RESPONSE	= 2,
+	SYNTHVID_VRAM_LOCATION		= 3,
+	SYNTHVID_VRAM_LOCATION_ACK	= 4,
+	SYNTHVID_SITUATION_UPDATE	= 5,
+	SYNTHVID_SITUATION_UPDATE_ACK	= 6,
+	SYNTHVID_POINTER_POSITION	= 7,
+	SYNTHVID_POINTER_SHAPE		= 8,
+	SYNTHVID_FEATURE_CHANGE		= 9,
+	SYNTHVID_DIRT			= 10,
+	SYNTHVID_RESOLUTION_REQUEST	= 13,
+	SYNTHVID_RESOLUTION_RESPONSE	= 14,
+
+	SYNTHVID_MAX			= 15
+};
+
+struct pipe_msg_hdr {
+	u32 type;
+	u32 size; /* size of message after this field */
+} __packed;
+
+struct hvd_screen_info {
+	u16 width;
+	u16 height;
+} __packed;
+
+struct synthvid_msg_hdr {
+	u32 type;
+	u32 size;  /* size of this header + payload after this field */
+} __packed;
+
+struct synthvid_version_req {
+	u32 version;
+} __packed;
+
+struct synthvid_version_resp {
+	u32 version;
+	u8 is_accepted;
+	u8 max_video_outputs;
+} __packed;
+
+struct synthvid_vram_location {
+	u64 user_ctx;
+	u8 is_vram_gpa_specified;
+	u64 vram_gpa;
+} __packed;
+
+struct synthvid_vram_location_ack {
+	u64 user_ctx;
+} __packed;
+
+struct video_output_situation {
+	u8 active;
+	u32 vram_offset;
+	u8 depth_bits;
+	u32 width_pixels;
+	u32 height_pixels;
+	u32 pitch_bytes;
+} __packed;
+
+struct synthvid_situation_update {
+	u64 user_ctx;
+	u8 video_output_count;
+	struct video_output_situation video_output[1];
+} __packed;
+
+struct synthvid_situation_update_ack {
+	u64 user_ctx;
+} __packed;
+
+struct synthvid_pointer_position {
+	u8 is_visible;
+	u8 video_output;
+	s32 image_x;
+	s32 image_y;
+} __packed;
+
+#define SYNTHVID_CURSOR_MAX_X 96
+#define SYNTHVID_CURSOR_MAX_Y 96
+#define SYNTHVID_CURSOR_ARGB_PIXEL_SIZE 4
+#define SYNTHVID_CURSOR_MAX_SIZE (SYNTHVID_CURSOR_MAX_X * \
+	SYNTHVID_CURSOR_MAX_Y * SYNTHVID_CURSOR_ARGB_PIXEL_SIZE)
+#define SYNTHVID_CURSOR_COMPLETE (-1)
+
+struct synthvid_pointer_shape {
+	u8 part_idx;
+	u8 is_argb;
+	u32 width; /* SYNTHVID_CURSOR_MAX_X at most */
+	u32 height; /* SYNTHVID_CURSOR_MAX_Y at most */
+	u32 hot_x; /* hotspot relative to upper-left of pointer image */
+	u32 hot_y;
+	u8 data[4];
+} __packed;
+
+struct synthvid_feature_change {
+	u8 is_dirt_needed;
+	u8 is_ptr_pos_needed;
+	u8 is_ptr_shape_needed;
+	u8 is_situ_needed;
+} __packed;
+
+struct rect {
+	s32 x1, y1; /* top left corner */
+	s32 x2, y2; /* bottom right corner, exclusive */
+} __packed;
+
+struct synthvid_dirt {
+	u8 video_output;
+	u8 dirt_count;
+	struct rect rect[1];
+} __packed;
+
+#define SYNTHVID_EDID_BLOCK_SIZE	128
+#define	SYNTHVID_MAX_RESOLUTION_COUNT	64
+
+struct synthvid_supported_resolution_req {
+	u8 maximum_resolution_count;
+} __packed;
+
+struct synthvid_supported_resolution_resp {
+	u8 edid_block[SYNTHVID_EDID_BLOCK_SIZE];
+	u8 resolution_count;
+	u8 default_resolution_index;
+	u8 is_standard;
+	struct hvd_screen_info supported_resolution[SYNTHVID_MAX_RESOLUTION_COUNT];
+} __packed;
+
+struct synthvid_msg {
+	struct pipe_msg_hdr pipe_hdr;
+	struct synthvid_msg_hdr vid_hdr;
+	union {
+		struct synthvid_version_req ver_req;
+		struct synthvid_version_resp ver_resp;
+		struct synthvid_vram_location vram;
+		struct synthvid_vram_location_ack vram_ack;
+		struct synthvid_situation_update situ;
+		struct synthvid_situation_update_ack situ_ack;
+		struct synthvid_pointer_position ptr_pos;
+		struct synthvid_pointer_shape ptr_shape;
+		struct synthvid_feature_change feature_chg;
+		struct synthvid_dirt dirt;
+		struct synthvid_supported_resolution_req resolution_req;
+		struct synthvid_supported_resolution_resp resolution_resp;
+	};
+} __packed;
+
+static inline bool hv_drm_version_ge(u32 ver1, u32 ver2)
+{
+	if (SYNTHVID_VER_GET_MAJOR(ver1) > SYNTHVID_VER_GET_MAJOR(ver2) ||
+	    (SYNTHVID_VER_GET_MAJOR(ver1) == SYNTHVID_VER_GET_MAJOR(ver2) &&
+	     SYNTHVID_VER_GET_MINOR(ver1) >= SYNTHVID_VER_GET_MINOR(ver2)))
+		return true;
+
+	return false;
+}
+
+static inline int hv_drm_sendpacket(struct hv_device *hdev, struct synthvid_msg *msg)
+{
+	static atomic64_t request_id = ATOMIC64_INIT(0);
+	struct hv_drm_device *hv = hv_get_drvdata(hdev);
+	int ret;
+
+	msg->pipe_hdr.type = PIPE_MSG_DATA;
+	msg->pipe_hdr.size = msg->vid_hdr.size;
+
+	ret = vmbus_sendpacket(hdev->channel, msg,
+			       msg->vid_hdr.size + sizeof(struct pipe_msg_hdr),
+			       atomic64_inc_return(&request_id),
+			       VM_PKT_DATA_INBAND, 0);
+
+	if (ret)
+		drm_err_ratelimited(&hv->dev, "Unable to send packet via vmbus; error %d\n", ret);
+
+	return ret;
+}
+
+static int hv_drm_negotiate_version(struct hv_device *hdev, u32 ver)
+{
+	struct hv_drm_device *hv = hv_get_drvdata(hdev);
+	struct synthvid_msg *msg = (struct synthvid_msg *)hv->init_buf;
+	struct drm_device *dev = &hv->dev;
+	unsigned long t;
+
+	memset(msg, 0, sizeof(struct synthvid_msg));
+	msg->vid_hdr.type = SYNTHVID_VERSION_REQUEST;
+	msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
+		sizeof(struct synthvid_version_req);
+	msg->ver_req.version = ver;
+	hv_drm_sendpacket(hdev, msg);
+
+	t = wait_for_completion_timeout(&hv->wait, VMBUS_VSP_TIMEOUT);
+	if (!t) {
+		drm_err(dev, "Time out on waiting version response\n");
+		return -ETIMEDOUT;
+	}
+
+	if (!msg->ver_resp.is_accepted) {
+		drm_err(dev, "Version request not accepted\n");
+		return -ENODEV;
+	}
+
+	hv->synthvid_version = ver;
+	drm_info(dev, "Synthvid Version major %d, minor %d\n",
+		 SYNTHVID_VER_GET_MAJOR(ver), SYNTHVID_VER_GET_MINOR(ver));
+
+	return 0;
+}
+
+int hv_drm_update_vram_location(struct hv_device *hdev, phys_addr_t vram_pp)
+{
+	struct hv_drm_device *hv = hv_get_drvdata(hdev);
+	struct synthvid_msg *msg = (struct synthvid_msg *)hv->init_buf;
+	struct drm_device *dev = &hv->dev;
+	unsigned long t;
+
+	memset(msg, 0, sizeof(struct synthvid_msg));
+	msg->vid_hdr.type = SYNTHVID_VRAM_LOCATION;
+	msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
+		sizeof(struct synthvid_vram_location);
+	msg->vram.user_ctx = vram_pp;
+	msg->vram.vram_gpa = vram_pp;
+	msg->vram.is_vram_gpa_specified = 1;
+	hv_drm_sendpacket(hdev, msg);
+
+	t = wait_for_completion_timeout(&hv->wait, VMBUS_VSP_TIMEOUT);
+	if (!t) {
+		drm_err(dev, "Time out on waiting vram location ack\n");
+		return -ETIMEDOUT;
+	}
+	if (msg->vram_ack.user_ctx != vram_pp) {
+		drm_err(dev, "Unable to set VRAM location\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+int hv_drm_update_situation(struct hv_device *hdev, u8 active, u32 bpp,
+			    u32 w, u32 h, u32 pitch)
+{
+	struct synthvid_msg msg;
+
+	memset(&msg, 0, sizeof(struct synthvid_msg));
+
+	msg.vid_hdr.type = SYNTHVID_SITUATION_UPDATE;
+	msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
+		sizeof(struct synthvid_situation_update);
+	msg.situ.user_ctx = 0;
+	msg.situ.video_output_count = 1;
+	msg.situ.video_output[0].active = active;
+	/* vram_offset should always be 0 */
+	msg.situ.video_output[0].vram_offset = 0;
+	msg.situ.video_output[0].depth_bits = bpp;
+	msg.situ.video_output[0].width_pixels = w;
+	msg.situ.video_output[0].height_pixels = h;
+	msg.situ.video_output[0].pitch_bytes = pitch;
+
+	hv_drm_sendpacket(hdev, &msg);
+
+	return 0;
+}
+
+/*
+ * Hyper-V supports a hardware cursor feature. It's not used by Linux VM,
+ * but the Hyper-V host still draws a point as an extra mouse pointer,
+ * which is unwanted, especially when Xorg is running.
+ *
+ * Hide the unwanted pointer, by setting msg.ptr_pos.is_visible = 1 and setting
+ * the msg.ptr_shape.data. Note: setting msg.ptr_pos.is_visible to 0 doesn't
+ * work in tests.
+ *
+ * The hv_drm_hide_hw_ptr() is also called in the handler of the
+ * SYNTHVID_FEATURE_CHANGE event, otherwise the host still draws an extra
+ * unwanted mouse pointer after the VM Connection window is closed and reopened.
+ */
+int hv_drm_hide_hw_ptr(struct hv_device *hdev)
+{
+	struct synthvid_msg msg;
+
+	memset(&msg, 0, sizeof(struct synthvid_msg));
+	msg.vid_hdr.type = SYNTHVID_POINTER_POSITION;
+	msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
+		sizeof(struct synthvid_pointer_position);
+	msg.ptr_pos.is_visible = 1;
+	msg.ptr_pos.video_output = 0;
+	msg.ptr_pos.image_x = 0;
+	msg.ptr_pos.image_y = 0;
+	hv_drm_sendpacket(hdev, &msg);
+
+	memset(&msg, 0, sizeof(struct synthvid_msg));
+	msg.vid_hdr.type = SYNTHVID_POINTER_SHAPE;
+	msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
+		sizeof(struct synthvid_pointer_shape);
+	msg.ptr_shape.part_idx = SYNTHVID_CURSOR_COMPLETE;
+	msg.ptr_shape.is_argb = 1;
+	msg.ptr_shape.width = 1;
+	msg.ptr_shape.height = 1;
+	msg.ptr_shape.hot_x = 0;
+	msg.ptr_shape.hot_y = 0;
+	msg.ptr_shape.data[0] = 0;
+	msg.ptr_shape.data[1] = 1;
+	msg.ptr_shape.data[2] = 1;
+	msg.ptr_shape.data[3] = 1;
+	hv_drm_sendpacket(hdev, &msg);
+
+	return 0;
+}
+
+int hv_drm_update_dirt(struct hv_device *hdev, struct drm_rect *rect)
+{
+	struct hv_drm_device *hv = hv_get_drvdata(hdev);
+	struct synthvid_msg msg;
+
+	if (!hv->dirt_needed)
+		return 0;
+
+	memset(&msg, 0, sizeof(struct synthvid_msg));
+
+	msg.vid_hdr.type = SYNTHVID_DIRT;
+	msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
+		sizeof(struct synthvid_dirt);
+	msg.dirt.video_output = 0;
+	msg.dirt.dirt_count = 1;
+	msg.dirt.rect[0].x1 = rect->x1;
+	msg.dirt.rect[0].y1 = rect->y1;
+	msg.dirt.rect[0].x2 = rect->x2;
+	msg.dirt.rect[0].y2 = rect->y2;
+
+	hv_drm_sendpacket(hdev, &msg);
+
+	return 0;
+}
+
+static int hv_drm_get_supported_resolution(struct hv_device *hdev)
+{
+	struct hv_drm_device *hv = hv_get_drvdata(hdev);
+	struct synthvid_msg *msg = (struct synthvid_msg *)hv->init_buf;
+	struct drm_device *dev = &hv->dev;
+	unsigned long t;
+	u8 index;
+	int i;
+
+	memset(msg, 0, sizeof(struct synthvid_msg));
+	msg->vid_hdr.type = SYNTHVID_RESOLUTION_REQUEST;
+	msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
+		sizeof(struct synthvid_supported_resolution_req);
+	msg->resolution_req.maximum_resolution_count =
+		SYNTHVID_MAX_RESOLUTION_COUNT;
+	hv_drm_sendpacket(hdev, msg);
+
+	t = wait_for_completion_timeout(&hv->wait, VMBUS_VSP_TIMEOUT);
+	if (!t) {
+		drm_err(dev, "Time out on waiting resolution response\n");
+		return -ETIMEDOUT;
+	}
+
+	if (msg->resolution_resp.resolution_count == 0 ||
+	    msg->resolution_resp.resolution_count >
+	    SYNTHVID_MAX_RESOLUTION_COUNT) {
+		drm_err(dev, "Invalid resolution count: %d\n",
+			msg->resolution_resp.resolution_count);
+		return -ENODEV;
+	}
+
+	index = msg->resolution_resp.default_resolution_index;
+	if (index >= msg->resolution_resp.resolution_count) {
+		drm_err(dev, "Invalid resolution index: %d\n", index);
+		return -ENODEV;
+	}
+
+	for (i = 0; i < msg->resolution_resp.resolution_count; i++) {
+		hv->screen_width_max = max_t(u32, hv->screen_width_max,
+			msg->resolution_resp.supported_resolution[i].width);
+		hv->screen_height_max = max_t(u32, hv->screen_height_max,
+			msg->resolution_resp.supported_resolution[i].height);
+	}
+
+	hv->preferred_width =
+		msg->resolution_resp.supported_resolution[index].width;
+	hv->preferred_height =
+		msg->resolution_resp.supported_resolution[index].height;
+
+	return 0;
+}
+
+static void hv_drm_receive_sub(struct hv_device *hdev, u32 bytes_recvd)
+{
+	struct hv_drm_device *hv = hv_get_drvdata(hdev);
+	struct synthvid_msg *msg;
+	size_t hdr_size;
+	size_t need;
+
+	if (!hv)
+		return;
+
+	hdr_size = sizeof(struct pipe_msg_hdr) +
+		   sizeof(struct synthvid_msg_hdr);
+	if (bytes_recvd < hdr_size) {
+		drm_err_ratelimited(&hv->dev,
+				    "synthvid packet too small for header: %u\n",
+				    bytes_recvd);
+		return;
+	}
+
+	msg = (struct synthvid_msg *)hv->recv_buf;
+	need = hdr_size;
+
+	switch (msg->vid_hdr.type) {
+	case SYNTHVID_VERSION_RESPONSE:
+		need += sizeof(struct synthvid_version_resp);
+		break;
+	case SYNTHVID_RESOLUTION_RESPONSE:
+		/*
+		 * The resolution response is variable length: the host
+		 * fills resolution_count entries, not the full
+		 * SYNTHVID_MAX_RESOLUTION_COUNT array. Require the fixed
+		 * prefix first so resolution_count can be read, then
+		 * demand exactly the count-sized array.
+		 */
+		need += offsetof(struct synthvid_supported_resolution_resp,
+				 supported_resolution);
+		if (bytes_recvd < need)
+			break;
+		if (msg->resolution_resp.resolution_count >
+		    SYNTHVID_MAX_RESOLUTION_COUNT) {
+			drm_err_ratelimited(&hv->dev,
+					    "synthvid resolution count too large: %u\n",
+					    msg->resolution_resp.resolution_count);
+			return;
+		}
+		need += msg->resolution_resp.resolution_count *
+			sizeof(struct hvd_screen_info);
+		break;
+	case SYNTHVID_VRAM_LOCATION_ACK:
+		need += sizeof(struct synthvid_vram_location_ack);
+		break;
+	case SYNTHVID_FEATURE_CHANGE:
+		/*
+		 * Not a completion-driving message: validate its own payload
+		 * and consume it here rather than falling through to the
+		 * memcpy/complete shared by the wait-event responses.
+		 */
+		if (bytes_recvd < need +
+		    sizeof(struct synthvid_feature_change)) {
+			drm_err_ratelimited(&hv->dev,
+					    "synthvid feature change packet too small: %u\n",
+					    bytes_recvd);
+			return;
+		}
+		hv->dirt_needed = msg->feature_chg.is_dirt_needed;
+		if (hv->dirt_needed)
+			hv_drm_hide_hw_ptr(hv->hdev);
+		return;
+	default:
+		return;
+	}
+
+	/*
+	 * Shared completion path for the wait-event responses
+	 * (VERSION_RESPONSE, RESOLUTION_RESPONSE, VRAM_LOCATION_ACK):
+	 * require the type-specific payload before handing the buffer to
+	 * the waiter.
+	 */
+	if (bytes_recvd < need) {
+		drm_err_ratelimited(&hv->dev,
+				    "synthvid packet too small for type %u: %u < %zu\n",
+				    msg->vid_hdr.type, bytes_recvd, need);
+		return;
+	}
+	memcpy(hv->init_buf, msg, bytes_recvd);
+	complete(&hv->wait);
+}
+
+static void hv_drm_receive(void *ctx)
+{
+	struct hv_device *hdev = ctx;
+	struct hv_drm_device *hv = hv_get_drvdata(hdev);
+	struct synthvid_msg *recv_buf;
+	u32 bytes_recvd;
+	u64 req_id;
+	int ret;
+
+	if (!hv)
+		return;
+
+	recv_buf = (struct synthvid_msg *)hv->recv_buf;
+
+	do {
+		ret = vmbus_recvpacket(hdev->channel, recv_buf,
+				       VMBUS_MAX_PACKET_SIZE,
+				       &bytes_recvd, &req_id);
+		if (ret) {
+			/*
+			 * A nonzero return (e.g. -ENOBUFS for an oversized
+			 * packet) is itself a malformed message: bytes_recvd
+			 * then reports the required length rather than a copied
+			 * payload, so it must not be forwarded to the
+			 * sub-handler. Channel recovery is not attempted.
+			 */
+			drm_err_ratelimited(&hv->dev,
+					    "vmbus_recvpacket failed: %d (need %u)\n",
+					    ret, bytes_recvd);
+		} else if (bytes_recvd > 0 &&
+			   recv_buf->pipe_hdr.type == PIPE_MSG_DATA) {
+			hv_drm_receive_sub(hdev, bytes_recvd);
+		}
+	} while (bytes_recvd > 0 && ret == 0);
+}
+
+int hv_drm_connect_vsp(struct hv_device *hdev)
+{
+	struct hv_drm_device *hv = hv_get_drvdata(hdev);
+	struct drm_device *dev = &hv->dev;
+	int ret;
+
+	ret = vmbus_open(hdev->channel, VMBUS_RING_BUFSIZE, VMBUS_RING_BUFSIZE,
+			 NULL, 0, hv_drm_receive, hdev);
+	if (ret) {
+		drm_err(dev, "Unable to open vmbus channel\n");
+		return ret;
+	}
+
+	/* Negotiate the protocol version with host */
+	switch (vmbus_proto_version) {
+	case VERSION_WIN10:
+	case VERSION_WIN10_V5:
+		ret = hv_drm_negotiate_version(hdev, SYNTHVID_VERSION_WIN10);
+		if (!ret)
+			break;
+		fallthrough;
+	case VERSION_WIN8:
+	case VERSION_WIN8_1:
+		ret = hv_drm_negotiate_version(hdev, SYNTHVID_VERSION_WIN8);
+		break;
+	default:
+		ret = hv_drm_negotiate_version(hdev, SYNTHVID_VERSION_WIN10);
+		break;
+	}
+
+	if (ret) {
+		drm_err(dev, "Synthetic video device version not accepted %d\n", ret);
+		goto error;
+	}
+
+	hv->screen_depth = SYNTHVID_DEPTH_WIN8;
+
+	if (hv_drm_version_ge(hv->synthvid_version, SYNTHVID_VERSION_WIN10)) {
+		ret = hv_drm_get_supported_resolution(hdev);
+		if (ret)
+			drm_err(dev, "Failed to get supported resolution from host, use default\n");
+	}
+
+	if (!hv->screen_width_max) {
+		hv->screen_width_max = SYNTHVID_WIDTH_WIN8;
+		hv->screen_height_max = SYNTHVID_HEIGHT_WIN8;
+		hv->preferred_width = SYNTHVID_WIDTH_WIN8;
+		hv->preferred_height = SYNTHVID_HEIGHT_WIN8;
+	}
+
+	hv->mmio_megabytes = hdev->channel->offermsg.offer.mmio_megabytes;
+
+	return 0;
+
+error:
+	vmbus_close(hdev->channel);
+	return ret;
+}