[PATCH v8 0/4] virtio-gpu: Add userptr support for compute workloads

[PATCH v8 0/4] virtio-gpu: Add userptr support for compute workloads

[Honglei Huang]

Hello,

This series adds virtio-gpu userptr support for ROCm native compute
contexts. The guest kernel pins an existing userspace mapping with
FOLL_LONGTERM and exposes it to the host as ordinary CREATE_BLOB
backing entries, avoiding a second shmem allocation and memcpy.

A non-zero userptr field selects that path. Probe
VIRTGPU_PARAM_USERPTR before using the field so an older guest kernel
rejects the request instead of silently creating a shmem blob.

GPU-readonly backing is requested with the virtio CREATE_BLOB wire
flag VIRTIO_GPU_BLOB_FLAG_USE_READONLY (also
VIRTGPU_BLOB_FLAG_USE_READONLY). The device MUST NOT write such a
resource. The guest accepts that flag and pins without FOLL_WRITE
only when the device advertised VIRTIO_GPU_F_BLOB_READONLY
(VIRTGPU_PARAM_BLOB_READONLY). Otherwise CREATE_BLOB fails, matching
the CROSS_DEVICE host-capability check.

Patches overview:
1. Add VIRTIO_GPU_CAPSET_ROCM capability for compute workloads
2. Extend DRM/virtio UAPI with userptr, PARAM_USERPTR,
   USE_READONLY, and F_BLOB_READONLY
3. Implement core userptr functionality with page management
4. Wire blob ioctl creation to userptr objects and probe the
   readonly feature

Tests:
- Full OPENCL CTS tests passed on ROCm 5.7.0 in V2000 platform.
- Near 70% percentage of OPENCL CTS tests passed on ROCm 7.0 W7900 platform.
- most HIP catch tests passed on ROCm 7.0 W7900 platform.
- Some AI applications enabled on ROCm 7.0 W7900 platform.
- latest ROCm 7.14 and ROCm 10 testing is ongoing.

V8 changes:
- Drop guest-only USERPTR ioctl flags; a non-zero userptr field
  selects the path
- Add VIRTGPU_PARAM_USERPTR so older kernels do not silently
  ignore the new field
- Request GPU-readonly backing with virtio wire flag USE_READONLY
- Accept USE_READONLY and omit FOLL_WRITE only if the host
  advertised VIRTIO_GPU_F_BLOB_READONLY
- Restore userptr blobs after hibernation without the shmem path

V7 changes:
- Mask guest-only DRM flags out of CREATE_BLOB wire blob_flags
- Clear userptr->pages after pin failure to avoid double-free
- DMA-map userptr SG only when virtio_gpu_use_dma_api() is required
- Use DMA_TO_DEVICE for readonly blobs
- Sync userptr SG for the device on TRANSFER_TO_HOST
- Mark writable pages dirty when unpinning
- Reject USERPTR unless blob_mem is VIRTGPU_BLOB_MEM_GUEST
- Disallow PRIME export of userptr objects
- Note that CAPSET_ROCM uses ID 8 because ID 7 is taken by VIRCL

V6 changes:
- Rebase onto drm-misc-next
- Keep USE_USERPTR / USERPTR_RDONLY as guest-only DRM flags; drop the
  virtio wire-header patch (5 patches down to 4)
- Fix userptr lifetime, DMA mapping, memlock accounting, alignment
  checks, and PRIME SG export
- Updated corresponding cover letter and commit messages

V5 changes:
    - Add VIRTIO_GPU_BLOB_FLAG_USERPTR_RDONLY definition to patch 2
    - Dropped unused VIRTIO_GPU_F_RESOURCE_USERPTR feature bit in patch 2
    - Included VIRTIO_GPU_BLOB_FLAG_USERPTR_RDONLY in VIRTGPU_BLOB_FLAG_USE_MASK in patch 5
    - Add check for userptr feature in patch 5 before creating userptr blob resource
    - Updated corresponding cover letter and commit messages

V4 changes:
    - Renamed VIRTIO_GPU_CAPSET_HSAKMT to VIRTIO_GPU_CAPSET_ROCM
    - Remove userptr feature probing cause it can reuse the guest
      blob resource code path, reduce patch count from 6 to 5
    - Updated corresponding commit messages
    - Consolidated userptr feature detection in final patch
    - Update corresponding cover letter content

V3 changes:
    - Split into focused patches for easier review
    - Removed complex interval tree userptr management
    - Simplified resource creation without deduplication
    - Added VIRTGPU_PARAM_RESOURCE_USERPTR for feature detection
    - Improved UAPI documentation and error handling
    - Enhanced code quality with proper cleanup paths
    - Removed MMU notifier dependencies for simplicity
    - Fixed resource lifecycle management issues

V2: - Split add HSAKMT context and blob userptr resource to two patches.
    - Remove MMU notifier related patches, cause use not moveable user space
      memory with MMU notifier is not a good idea.
    - Remove HSAKMT context check when create context, let all the context
      support the userptr feature.
    - Remove MMU notifier related content in cover letter.
    - Add more comments  for patch 6 in cover letter.

Previous version:
https://lore.kernel.org/dri-devel/20260917102540.1312102-1-honghuan@amd.com/

Honglei Huang (4):
  drm/virtio-gpu: Add VIRTIO_GPU_CAPSET_ROCM capability
  drm/virtgpu api: add blob userptr resource
  drm/virtio: implement userptr support for zero-copy memory access
  drm/virtio: wire blob ioctl creation to userptr objects

 drivers/gpu/drm/virtio/Makefile          |   3 +-
 drivers/gpu/drm/virtio/virtgpu_debugfs.c |   1 +
 drivers/gpu/drm/virtio/virtgpu_drv.h     |  43 +++
 drivers/gpu/drm/virtio/virtgpu_ioctl.c   |  35 ++-
 drivers/gpu/drm/virtio/virtgpu_kms.c     |   8 +-
 drivers/gpu/drm/virtio/virtgpu_object.c  |  22 ++
 drivers/gpu/drm/virtio/virtgpu_userptr.c | 365 +++++++++++++++++++++++
 drivers/gpu/drm/virtio/virtgpu_vq.c      |  33 +-
 include/uapi/drm/virtgpu_drm.h           |  13 +
 include/uapi/linux/virtio_gpu.h          |   7 +
 10 files changed, 513 insertions(+), 17 deletions(-)
 create mode 100644 drivers/gpu/drm/virtio/virtgpu_userptr.c


base-commit: 766bfba0f3bae329f99b42dcabc3ef11fa368f0b
-- 
2.34.1

[PATCH v8 1/4] drm/virtio-gpu: Add VIRTIO_GPU_CAPSET_ROCM capability

[Honglei Huang]

Add a new GPU capability set VIRTIO_GPU_CAPSET_ROCM to support
ROCm compute workloads in virtualized environments.

ROCm (Radeon Open Compute) is AMD's open-source software platform
for GPU compute and HPC workloads.

ID 7 is already used by VIRCL in the virgl/virtio-gpu stack, so
ROCm uses ID 8. A matching virtio-gpu specification change is in
progress to register this assignment.

Signed-off-by: Honglei Huang <honghuan@amd.com>
---
 include/uapi/linux/virtio_gpu.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/uapi/linux/virtio_gpu.h b/include/uapi/linux/virtio_gpu.h
index 4f530d9005..3d4dfadc9d 100644
--- a/include/uapi/linux/virtio_gpu.h
+++ b/include/uapi/linux/virtio_gpu.h
@@ -321,6 +321,7 @@ struct virtio_gpu_cmd_submit {
 #define VIRTIO_GPU_CAPSET_VENUS 4
 #define VIRTIO_GPU_CAPSET_CROSS_DOMAIN 5
 #define VIRTIO_GPU_CAPSET_DRM 6
+#define VIRTIO_GPU_CAPSET_ROCM 8
 
 /* VIRTIO_GPU_CMD_GET_CAPSET_INFO */
 struct virtio_gpu_get_capset_info {
-- 
2.34.1

[PATCH v8 2/4] drm/virtgpu api: add blob userptr resource

[Honglei Huang]

Add a userptr address field so userspace can request a blob backed
by an existing process mapping. A non-zero userptr selects that
path; probe VIRTGPU_PARAM_USERPTR before using the field.

GPU-readonly backing is requested with the virtio CREATE_BLOB wire
flag VIRTIO_GPU_BLOB_FLAG_USE_READONLY (also
VIRTGPU_BLOB_FLAG_USE_READONLY). The device MUST NOT write such a
resource. The guest pins without FOLL_WRITE only when the device
advertised VIRTIO_GPU_F_BLOB_READONLY (VIRTGPU_PARAM_BLOB_READONLY).

Signed-off-by: Honglei Huang <honghuan@amd.com>
---
 include/uapi/drm/virtgpu_drm.h  | 13 +++++++++++++
 include/uapi/linux/virtio_gpu.h |  6 ++++++
 2 files changed, 19 insertions(+)

diff --git a/include/uapi/drm/virtgpu_drm.h b/include/uapi/drm/virtgpu_drm.h
index 95587e12ae..80f73b3276 100644
--- a/include/uapi/drm/virtgpu_drm.h
+++ b/include/uapi/drm/virtgpu_drm.h
@@ -99,6 +99,8 @@ struct drm_virtgpu_execbuffer {
 #define VIRTGPU_PARAM_SUPPORTED_CAPSET_IDs 7 /* Bitmask of supported capability set ids */
 #define VIRTGPU_PARAM_EXPLICIT_DEBUG_NAME 8 /* Ability to set debug name from userspace */
 #define VIRTGPU_PARAM_BLOB_ALIGNMENT 9 /* Device alignment requirements for blobs */
+#define VIRTGPU_PARAM_USERPTR 10 /* CREATE_BLOB userptr field is supported */
+#define VIRTGPU_PARAM_BLOB_READONLY 11 /* VIRTGPU_BLOB_FLAG_USE_READONLY is honored */
 
 struct drm_virtgpu_getparam {
 	__u64 param;
@@ -186,6 +188,10 @@ struct drm_virtgpu_resource_create_blob {
 #define VIRTGPU_BLOB_FLAG_USE_MAPPABLE     0x0001
 #define VIRTGPU_BLOB_FLAG_USE_SHAREABLE    0x0002
 #define VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE 0x0004
+/* Wire flag: device MUST NOT write. Guest pins without FOLL_WRITE.
+ * Rejected unless VIRTGPU_PARAM_BLOB_READONLY is 1.
+ */
+#define VIRTGPU_BLOB_FLAG_USE_READONLY     0x0008
 	/* zero is invalid blob_mem */
 	__u32 blob_mem;
 	__u32 blob_flags;
@@ -205,6 +211,13 @@ struct drm_virtgpu_resource_create_blob {
 #define DRM_VIRTGPU_BLOB_FLAG_HINT_DEFER_MAPPING        0x0001
 	__u32 blob_hints;
 	__u32 pad2;
+
+	/*
+	 * Guest VA to pin as blob backing. Non-zero selects the userptr
+	 * path and is valid only with VIRTGPU_BLOB_MEM_GUEST. Must be 0
+	 * otherwise. Probe VIRTGPU_PARAM_USERPTR before using this field.
+	 */
+	__u64 userptr;
 };
 
 #define VIRTGPU_CONTEXT_PARAM_CAPSET_ID       0x0001
diff --git a/include/uapi/linux/virtio_gpu.h b/include/uapi/linux/virtio_gpu.h
index 3d4dfadc9d..33f5332e59 100644
--- a/include/uapi/linux/virtio_gpu.h
+++ b/include/uapi/linux/virtio_gpu.h
@@ -72,6 +72,10 @@
  * must be aligned to that value.
  */
 #define VIRTIO_GPU_F_BLOB_ALIGNMENT      5
+/*
+ * VIRTIO_GPU_BLOB_FLAG_USE_READONLY
+ */
+#define VIRTIO_GPU_F_BLOB_READONLY       6
 
 enum virtio_gpu_ctrl_type {
 	VIRTIO_GPU_UNDEFINED = 0,
@@ -415,6 +419,8 @@ struct virtio_gpu_resource_create_blob {
 #define VIRTIO_GPU_BLOB_FLAG_USE_MAPPABLE     0x0001
 #define VIRTIO_GPU_BLOB_FLAG_USE_SHAREABLE    0x0002
 #define VIRTIO_GPU_BLOB_FLAG_USE_CROSS_DEVICE 0x0004
+/* Device MUST NOT write. Driver may pin read-only guest pages. */
+#define VIRTIO_GPU_BLOB_FLAG_USE_READONLY     0x0008
 	/* zero is invalid blob mem */
 	__le32 blob_mem;
 	__le32 blob_flags;
-- 
2.34.1

[PATCH v8 3/4] drm/virtio: implement userptr support for zero-copy memory access

[Honglei Huang]

Add userptr blob objects so the guest kernel can pin an existing
userspace mapping and advertise it as CREATE_BLOB backing entries.

- New virtio_gpu_object_userptr type for userptr resources
- Pin pages with pin_user_pages_fast() and FOLL_LONGTERM
- Omit FOLL_WRITE when VIRTGPU_BLOB_FLAG_USE_READONLY is set
- Charge FOLL_LONGTERM pins against RLIMIT_MEMLOCK
- DMA-map the scatterlist only when virtio_gpu_use_dma_api() is
  required; use DMA_TO_DEVICE for USE_READONLY blobs
- Sync userptr SG for the device on TRANSFER_TO_HOST
- Mark writable pages dirty when unpinning
- Keep pages pinned until RESOURCE_UNREF is queued; drop them from
  cleanup_object() on the unref response or on create failure
- Clear userptr->pages on pin failure to avoid double-free on cleanup
- Reject unaligned or overflowing userptr ranges at create time
- Disallow PRIME export of userptr objects
- Save CREATE_BLOB params and restore userptr resources after
  hibernation without using the shmem restore path

Signed-off-by: Honglei Huang <honghuan@amd.com>
---
 drivers/gpu/drm/virtio/Makefile          |   3 +-
 drivers/gpu/drm/virtio/virtgpu_drv.h     |  43 +++
 drivers/gpu/drm/virtio/virtgpu_object.c  |  22 ++
 drivers/gpu/drm/virtio/virtgpu_userptr.c | 365 +++++++++++++++++++++++
 drivers/gpu/drm/virtio/virtgpu_vq.c      |  33 +-
 5 files changed, 456 insertions(+), 10 deletions(-)
 create mode 100644 drivers/gpu/drm/virtio/virtgpu_userptr.c

diff --git a/drivers/gpu/drm/virtio/Makefile b/drivers/gpu/drm/virtio/Makefile
index d2e1788a82..fe7332a621 100644
--- a/drivers/gpu/drm/virtio/Makefile
+++ b/drivers/gpu/drm/virtio/Makefile
@@ -6,6 +6,7 @@
 virtio-gpu-y := virtgpu_drv.o virtgpu_kms.o virtgpu_gem.o virtgpu_vram.o \
 	virtgpu_display.o virtgpu_vq.o \
 	virtgpu_fence.o virtgpu_object.o virtgpu_debugfs.o virtgpu_plane.o \
-	virtgpu_ioctl.o virtgpu_prime.o virtgpu_trace_points.o virtgpu_submit.o
+	virtgpu_ioctl.o virtgpu_prime.o virtgpu_trace_points.o virtgpu_submit.o \
+	virtgpu_userptr.o
 
 obj-$(CONFIG_DRM_VIRTIO_GPU) += virtio-gpu.o
diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index 9df4c71173..e0941cc187 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -105,6 +105,7 @@ struct virtio_gpu_object_params {
 	uint32_t blob_flags;
 	uint64_t blob_id;
 	uint32_t blob_hints;
+	uint64_t userptr;
 };
 
 struct virtio_gpu_object {
@@ -138,12 +139,42 @@ struct virtio_gpu_object_vram {
 	struct drm_mm_node vram_node;
 };
 
+struct virtio_gpu_object_userptr;
+
+struct virtio_gpu_object_userptr_ops {
+	int (*get_pages)(struct virtio_gpu_object_userptr *userptr);
+	void (*put_pages)(struct virtio_gpu_object_userptr *userptr);
+};
+
+struct virtio_gpu_object_userptr {
+	struct virtio_gpu_object base;
+	const struct virtio_gpu_object_userptr_ops *ops;
+	/* Protects pages and sgt. */
+	struct mutex lock;
+
+	uint64_t start;
+	uint32_t npages;
+	uint32_t bo_handle;
+	uint32_t flags;
+
+	struct virtio_gpu_device *vgdev;
+	struct drm_file *file;
+	struct page **pages;
+	struct sg_table *sgt;
+	bool dma_mapped;
+	enum dma_data_direction dma_dir;
+	struct mm_struct *mm;
+};
+
 #define to_virtio_gpu_shmem(virtio_gpu_object) \
 	container_of((virtio_gpu_object), struct virtio_gpu_object_shmem, base)
 
 #define to_virtio_gpu_vram(virtio_gpu_object) \
 	container_of((virtio_gpu_object), struct virtio_gpu_object_vram, base)
 
+#define to_virtio_gpu_userptr(virtio_gpu_object) \
+	container_of((virtio_gpu_object), struct virtio_gpu_object_userptr, base)
+
 struct virtio_gpu_object_array {
 	struct ww_acquire_ctx ticket;
 	struct list_head next;
@@ -284,6 +315,7 @@ struct virtio_gpu_device {
 	bool has_host_visible;
 	bool has_context_init;
 	bool has_blob_alignment;
+	bool has_blob_readonly;
 	bool hibernated;
 	struct virtio_shm_region host_visible_region;
 	struct drm_mm host_visible_mm;
@@ -562,4 +594,15 @@ void virtio_gpu_vram_map_deferred(struct virtio_gpu_object_vram *vram);
 int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
 				struct drm_file *file);
 
+/* virtgpu_userptr.c */
+int virtio_gpu_userptr_create(struct virtio_gpu_device *vgdev,
+			      struct drm_file *file,
+			      struct virtio_gpu_object_params *params,
+			      struct virtio_gpu_object **bo_ptr);
+bool virtio_gpu_is_userptr(struct virtio_gpu_object *bo);
+void virtio_gpu_userptr_dma_sync_for_device(struct virtio_gpu_object *bo);
+int virtio_gpu_userptr_restore(struct virtio_gpu_device *vgdev,
+			       struct virtio_gpu_object *bo,
+			       struct virtio_gpu_mem_entry **ents,
+			       unsigned int *nents);
 #endif
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
index 49899485be..ab21494b1c 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -91,6 +91,16 @@ void virtio_gpu_cleanup_object(struct virtio_gpu_object *bo)
 		drm_gem_free_mmap_offset(&vram->base.base.base);
 		drm_gem_object_release(&vram->base.base.base);
 		kfree(vram);
+	} else if (virtio_gpu_is_userptr(bo)) {
+		struct virtio_gpu_object_userptr *userptr =
+			to_virtio_gpu_userptr(bo);
+
+		mutex_lock(&userptr->lock);
+		userptr->ops->put_pages(userptr);
+		mutex_unlock(&userptr->lock);
+		mutex_destroy(&userptr->lock);
+		drm_gem_object_release(&userptr->base.base.base);
+		kfree(userptr);
 	} else {
 		drm_gem_object_release(&bo->base.base);
 		kfree(bo);
@@ -316,6 +326,18 @@ int virtio_gpu_object_restore_all(struct virtio_gpu_device *vgdev)
 			continue;
 		}
 
+		if (virtio_gpu_is_userptr(bo)) {
+			ret = virtio_gpu_userptr_restore(vgdev, bo, &ents,
+							 &nents);
+			if (ret)
+				break;
+
+			virtio_gpu_cmd_resource_create_blob(vgdev, bo,
+							    &bo->params,
+							    ents, nents);
+			continue;
+		}
+
 		if (bo->params.blob || bo->attached) {
 			ret = virtio_gpu_object_shmem_init(vgdev, bo, &ents,
 							   &nents);
diff --git a/drivers/gpu/drm/virtio/virtgpu_userptr.c b/drivers/gpu/drm/virtio/virtgpu_userptr.c
new file mode 100644
index 0000000000..ccfd96844e
--- /dev/null
+++ b/drivers/gpu/drm/virtio/virtgpu_userptr.c
@@ -0,0 +1,365 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/dma-mapping.h>
+#include <linux/limits.h>
+#include <linux/mm.h>
+#include <linux/overflow.h>
+#include <linux/pid.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/signal.h>
+#include <linux/vmalloc.h>
+
+#include "virtgpu_drv.h"
+#include <drm/drm_gem.h>
+
+static void virtio_gpu_userptr_free(struct drm_gem_object *obj)
+{
+	struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(obj);
+	struct virtio_gpu_device *vgdev = obj->dev->dev_private;
+
+	/*
+	 * Keep pages pinned until RESOURCE_UNREF completes. The response
+	 * callback calls virtio_gpu_cleanup_object(), which drops them.
+	 */
+	if (bo->created) {
+		virtio_gpu_remove_from_restore_list(bo);
+		virtio_gpu_cmd_unref_resource(vgdev, bo, false);
+		virtio_gpu_notify(vgdev);
+		return;
+	}
+
+	virtio_gpu_cleanup_object(bo);
+}
+
+static struct dma_buf *
+virtio_gpu_userptr_prime_export(struct drm_gem_object *obj, int flags)
+{
+	return ERR_PTR(-EINVAL);
+}
+
+static const struct drm_gem_object_funcs virtio_gpu_userptr_funcs = {
+	.open = virtio_gpu_gem_object_open,
+	.close = virtio_gpu_gem_object_close,
+	.free = virtio_gpu_userptr_free,
+	.export = virtio_gpu_userptr_prime_export,
+};
+
+bool virtio_gpu_is_userptr(struct virtio_gpu_object *bo)
+{
+	return bo->base.base.funcs == &virtio_gpu_userptr_funcs;
+}
+
+void virtio_gpu_userptr_dma_sync_for_device(struct virtio_gpu_object *bo)
+{
+	struct virtio_gpu_object_userptr *userptr = to_virtio_gpu_userptr(bo);
+	struct device *dev;
+
+	if (!userptr->dma_mapped)
+		return;
+
+	dev = drm_dev_dma_dev(userptr->base.base.base.dev);
+	dma_sync_sgtable_for_device(dev, userptr->sgt, DMA_TO_DEVICE);
+}
+
+static int
+virtio_gpu_userptr_get_pages(struct virtio_gpu_object_userptr *userptr)
+{
+	unsigned int flag = FOLL_LONGTERM;
+	unsigned int num_pages, pinned = 0;
+	int ret = 0;
+
+	if (userptr->pages)
+		return 0;
+
+	userptr->pages = kvmalloc_array(userptr->npages, sizeof(struct page *),
+					GFP_KERNEL);
+	if (!userptr->pages)
+		return -ENOMEM;
+
+	if (!(userptr->flags & VIRTGPU_BLOB_FLAG_USE_READONLY))
+		flag |= FOLL_WRITE;
+
+	do {
+		num_pages = userptr->npages - pinned;
+
+		ret = pin_user_pages_fast(userptr->start + pinned * PAGE_SIZE,
+					  num_pages, flag,
+					  userptr->pages + pinned);
+
+		if (ret < 0) {
+			if (pinned)
+				unpin_user_pages(userptr->pages, pinned);
+			kvfree(userptr->pages);
+			userptr->pages = NULL;
+			return ret;
+		}
+
+		pinned += ret;
+
+	} while (pinned < userptr->npages);
+
+	return 0;
+}
+
+static void
+virtio_gpu_userptr_unaccount(struct virtio_gpu_object_userptr *userptr)
+{
+	if (!userptr->mm)
+		return;
+
+	atomic64_sub(userptr->npages, &userptr->mm->pinned_vm);
+	mmdrop(userptr->mm);
+	userptr->mm = NULL;
+}
+
+static void
+virtio_gpu_userptr_put_pages(struct virtio_gpu_object_userptr *userptr)
+{
+	struct drm_device *dev = userptr->base.base.base.dev;
+
+	if (userptr->sgt) {
+		if (userptr->dma_mapped)
+			dma_unmap_sgtable(drm_dev_dma_dev(dev), userptr->sgt,
+					  userptr->dma_dir, 0);
+		userptr->dma_mapped = false;
+		sg_free_table(userptr->sgt);
+		kfree(userptr->sgt);
+		userptr->sgt = NULL;
+	}
+
+	if (userptr->pages) {
+		bool dirty = !(userptr->flags & VIRTGPU_BLOB_FLAG_USE_READONLY);
+
+		unpin_user_pages_dirty_lock(userptr->pages, userptr->npages,
+					    dirty);
+		kvfree(userptr->pages);
+		userptr->pages = NULL;
+	}
+
+	virtio_gpu_userptr_unaccount(userptr);
+}
+
+static int
+virtio_gpu_userptr_get_entries(struct virtio_gpu_device *vgdev,
+			       struct virtio_gpu_object_userptr *userptr,
+			       struct virtio_gpu_mem_entry **ents,
+			       unsigned int *nents)
+{
+	bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
+	struct scatterlist *sg;
+	unsigned int count;
+	int si;
+
+	count = use_dma_api ? userptr->sgt->nents : userptr->sgt->orig_nents;
+	if (!count)
+		return -EINVAL;
+
+	*ents = kvmalloc_array(count, sizeof(**ents), GFP_KERNEL);
+	if (!*ents)
+		return -ENOMEM;
+
+	if (use_dma_api) {
+		for_each_sgtable_dma_sg(userptr->sgt, sg, si) {
+			(*ents)[si].addr = cpu_to_le64(sg_dma_address(sg));
+			(*ents)[si].length = cpu_to_le32(sg_dma_len(sg));
+			(*ents)[si].padding = 0;
+		}
+	} else {
+		for_each_sgtable_sg(userptr->sgt, sg, si) {
+			(*ents)[si].addr = cpu_to_le64(sg_phys(sg));
+			(*ents)[si].length = cpu_to_le32(sg->length);
+			(*ents)[si].padding = 0;
+		}
+	}
+
+	*nents = count;
+	return 0;
+}
+
+int virtio_gpu_userptr_restore(struct virtio_gpu_device *vgdev,
+			       struct virtio_gpu_object *bo,
+			       struct virtio_gpu_mem_entry **ents,
+			       unsigned int *nents)
+{
+	struct virtio_gpu_object_userptr *userptr = to_virtio_gpu_userptr(bo);
+	int ret;
+
+	mutex_lock(&userptr->lock);
+	if (!userptr->sgt || !userptr->pages) {
+		mutex_unlock(&userptr->lock);
+		return -EINVAL;
+	}
+
+	if (userptr->dma_mapped) {
+		struct device *dev = drm_dev_dma_dev(vgdev->ddev);
+
+		dma_unmap_sgtable(dev, userptr->sgt, userptr->dma_dir, 0);
+		userptr->dma_mapped = false;
+		ret = dma_map_sgtable(dev, userptr->sgt, userptr->dma_dir, 0);
+		if (ret) {
+			mutex_unlock(&userptr->lock);
+			return ret;
+		}
+		userptr->dma_mapped = true;
+	}
+
+	ret = virtio_gpu_userptr_get_entries(vgdev, userptr, ents, nents);
+	mutex_unlock(&userptr->lock);
+	return ret;
+}
+
+static int
+virtio_gpu_userptr_init(struct drm_device *dev, struct drm_file *file,
+			struct virtio_gpu_object_userptr *userptr,
+			struct virtio_gpu_object_params *params,
+			const struct virtio_gpu_object_userptr_ops *ops)
+{
+	struct drm_gem_object *obj;
+	int ret;
+
+	userptr->start = params->userptr;
+	userptr->npages = params->size >> PAGE_SHIFT;
+	userptr->flags = params->blob_flags;
+
+	mutex_init(&userptr->lock);
+	userptr->vgdev = dev->dev_private;
+	userptr->file = file;
+	userptr->ops = ops;
+
+	/*
+	 * Allocate the resource id before GEM init so a failure here can
+	 * unwind with a plain kfree and does not need a special id=0 guard
+	 * in the shared resource_id_put helper.
+	 */
+	ret = virtio_gpu_resource_id_get(userptr->vgdev,
+					 &userptr->base.hw_res_handle);
+	if (ret) {
+		mutex_destroy(&userptr->lock);
+		return ret;
+	}
+
+	obj = &userptr->base.base.base;
+	obj->funcs = &virtio_gpu_userptr_funcs;
+
+	drm_gem_private_object_init(dev, obj, params->size);
+	INIT_LIST_HEAD(&userptr->base.restore_node);
+
+	return 0;
+}
+
+static const struct virtio_gpu_object_userptr_ops virtio_gpu_userptr_ops = {
+	.get_pages = virtio_gpu_userptr_get_pages,
+	.put_pages = virtio_gpu_userptr_put_pages,
+};
+
+int virtio_gpu_userptr_create(struct virtio_gpu_device *vgdev,
+			      struct drm_file *file,
+			      struct virtio_gpu_object_params *params,
+			      struct virtio_gpu_object **bo_ptr)
+{
+	struct virtio_gpu_object_userptr *userptr;
+	struct virtio_gpu_mem_entry *ents = NULL;
+	struct sg_table *sgt;
+	struct mm_struct *mm;
+	unsigned long lock_limit;
+	unsigned long start;
+	unsigned long end;
+	s64 new_pinned;
+	unsigned int nents;
+	int ret;
+
+	*bo_ptr = NULL;
+
+	if (!params->size || !IS_ALIGNED(params->size, PAGE_SIZE) ||
+	    params->userptr != (unsigned long)params->userptr)
+		return -EINVAL;
+
+	start = params->userptr;
+	if (!IS_ALIGNED(start, PAGE_SIZE) ||
+	    check_add_overflow(start, (unsigned long)params->size, &end))
+		return -EINVAL;
+
+	if (!can_do_mlock())
+		return -EPERM;
+
+	if (params->size >> PAGE_SHIFT > INT_MAX)
+		return -E2BIG;
+
+	if (!access_ok((void __user *)start, params->size))
+		return -EFAULT;
+
+	userptr = kzalloc_obj(*userptr);
+	if (!userptr)
+		return -ENOMEM;
+
+	ret = virtio_gpu_userptr_init(vgdev->ddev, file, userptr, params,
+				      &virtio_gpu_userptr_ops);
+	if (ret) {
+		kfree(userptr);
+		return ret;
+	}
+
+	mm = current->mm;
+	mmgrab(mm);
+	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+	new_pinned = atomic64_add_return(userptr->npages, &mm->pinned_vm);
+	if (new_pinned < 0 ||
+	    (new_pinned > lock_limit && !capable(CAP_IPC_LOCK))) {
+		atomic64_sub(userptr->npages, &mm->pinned_vm);
+		mmdrop(mm);
+		ret = new_pinned < 0 ? -EOVERFLOW : -ENOMEM;
+		goto err_cleanup;
+	}
+	userptr->mm = mm;
+
+	mutex_lock(&userptr->lock);
+	ret = userptr->ops->get_pages(userptr);
+	mutex_unlock(&userptr->lock);
+	if (ret)
+		goto err_cleanup;
+
+	sgt = drm_prime_pages_to_sg(vgdev->ddev, userptr->pages,
+				    userptr->npages);
+	if (IS_ERR(sgt)) {
+		ret = PTR_ERR(sgt);
+		goto err_cleanup;
+	}
+
+	userptr->sgt = sgt;
+
+	/*
+	 * Match shmem blobs: only DMA-map when the virtio DMA API is in
+	 * use. Mapping unconditionally can create SWIOTLB bounce buffers
+	 * that get copied back over guest pages on unmap even though the
+	 * host was given sg_phys() addresses.
+	 */
+	if (virtio_gpu_use_dma_api(vgdev->vdev)) {
+		enum dma_data_direction dir =
+			(userptr->flags & VIRTGPU_BLOB_FLAG_USE_READONLY) ?
+			DMA_TO_DEVICE : DMA_BIDIRECTIONAL;
+
+		ret = dma_map_sgtable(drm_dev_dma_dev(vgdev->ddev), sgt,
+				      dir, 0);
+		if (ret)
+			goto err_cleanup;
+
+		userptr->dma_dir = dir;
+		userptr->dma_mapped = true;
+	}
+
+	ret = virtio_gpu_userptr_get_entries(vgdev, userptr, &ents, &nents);
+	if (ret)
+		goto err_cleanup;
+
+	virtio_gpu_cmd_resource_create_blob(vgdev, &userptr->base, params, ents,
+					    nents);
+
+	userptr->base.params = *params;
+	virtio_gpu_add_object_to_restore_list(vgdev, &userptr->base);
+
+	*bo_ptr = &userptr->base;
+	return 0;
+
+err_cleanup:
+	virtio_gpu_cleanup_object(&userptr->base);
+	return ret;
+}
diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
index c02c03c10d..dcbd7bb7a6 100644
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -781,9 +781,14 @@ int virtio_gpu_panic_cmd_transfer_to_host_2d(struct virtio_gpu_device *vgdev,
 	struct virtio_gpu_vbuffer *vbuf;
 	bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
 
-	if (virtio_gpu_is_shmem(bo) && use_dma_api)
-		dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
-					    bo->base.sgt, DMA_TO_DEVICE);
+	if (use_dma_api) {
+		if (virtio_gpu_is_shmem(bo))
+			dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
+						    bo->base.sgt,
+						    DMA_TO_DEVICE);
+		else if (virtio_gpu_is_userptr(bo))
+			virtio_gpu_userptr_dma_sync_for_device(bo);
+	}
 
 	cmd_p = virtio_gpu_panic_alloc_cmd_resp(vgdev, &vbuf, sizeof(*cmd_p));
 	memset(cmd_p, 0, sizeof(*cmd_p));
@@ -812,9 +817,14 @@ void virtio_gpu_cmd_transfer_to_host_2d(struct virtio_gpu_device *vgdev,
 	struct virtio_gpu_vbuffer *vbuf;
 	bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
 
-	if (virtio_gpu_is_shmem(bo) && use_dma_api)
-		dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
-					    bo->base.sgt, DMA_TO_DEVICE);
+	if (use_dma_api) {
+		if (virtio_gpu_is_shmem(bo))
+			dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
+						    bo->base.sgt,
+						    DMA_TO_DEVICE);
+		else if (virtio_gpu_is_userptr(bo))
+			virtio_gpu_userptr_dma_sync_for_device(bo);
+	}
 
 	cmd_p = virtio_gpu_alloc_cmd(vgdev, &vbuf, sizeof(*cmd_p));
 	memset(cmd_p, 0, sizeof(*cmd_p));
@@ -1245,9 +1255,14 @@ void virtio_gpu_cmd_transfer_to_host_3d(struct virtio_gpu_device *vgdev,
 	struct virtio_gpu_vbuffer *vbuf;
 	bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
 
-	if (virtio_gpu_is_shmem(bo) && use_dma_api)
-		dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
-					    bo->base.sgt, DMA_TO_DEVICE);
+	if (use_dma_api) {
+		if (virtio_gpu_is_shmem(bo))
+			dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
+						    bo->base.sgt,
+						    DMA_TO_DEVICE);
+		else if (virtio_gpu_is_userptr(bo))
+			virtio_gpu_userptr_dma_sync_for_device(bo);
+	}
 
 	cmd_p = virtio_gpu_alloc_cmd(vgdev, &vbuf, sizeof(*cmd_p));
 	memset(cmd_p, 0, sizeof(*cmd_p));
-- 
2.34.1

[PATCH v8 4/4] drm/virtio: wire blob ioctl creation to userptr objects

[Honglei Huang]

Integrate userptr into the blob resource creation ioctl.

- A non-zero userptr selects virtio_gpu_userptr_create()
- Reject userptr unless blob_mem is VIRTGPU_BLOB_MEM_GUEST
- Reject VIRTGPU_BLOB_FLAG_USE_READONLY unless the device
  advertised VIRTIO_GPU_F_BLOB_READONLY
- Advertise VIRTGPU_PARAM_USERPTR and VIRTGPU_PARAM_BLOB_READONLY

Signed-off-by: Honglei Huang <honghuan@amd.com>
---
 drivers/gpu/drm/virtio/virtgpu_debugfs.c |  1 +
 drivers/gpu/drm/virtio/virtgpu_ioctl.c   | 35 ++++++++++++++++++++----
 drivers/gpu/drm/virtio/virtgpu_kms.c     |  8 ++++--
 3 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_debugfs.c b/drivers/gpu/drm/virtio/virtgpu_debugfs.c
index 3a68a16b58..b8b9b40584 100644
--- a/drivers/gpu/drm/virtio/virtgpu_debugfs.c
+++ b/drivers/gpu/drm/virtio/virtgpu_debugfs.c
@@ -55,6 +55,7 @@ static int virtio_gpu_features(struct seq_file *m, void *data)
 			    vgdev->has_resource_assign_uuid);
 
 	virtio_gpu_add_bool(m, "blob resources", vgdev->has_resource_blob);
+	virtio_gpu_add_bool(m, "blob readonly", vgdev->has_blob_readonly);
 	virtio_gpu_add_bool(m, "context init", vgdev->has_context_init);
 	virtio_gpu_add_int(m, "cap sets", vgdev->num_capsets);
 	virtio_gpu_add_int(m, "scanouts", vgdev->num_scanouts);
diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 3d8e4ccdb7..3dc058e50e 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -36,7 +36,10 @@
 
 #define VIRTGPU_BLOB_FLAG_USE_MASK (VIRTGPU_BLOB_FLAG_USE_MAPPABLE | \
 				    VIRTGPU_BLOB_FLAG_USE_SHAREABLE | \
-				    VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE)
+				    VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE | \
+				    VIRTGPU_BLOB_FLAG_USE_READONLY)
+
+#define VIRTGPU_BLOB_HINT_MASK DRM_VIRTGPU_BLOB_FLAG_HINT_DEFER_MAPPING
 
 /* Must be called with &virtio_gpu_fpriv.struct_mutex held. */
 static void virtio_gpu_create_context_locked(struct virtio_gpu_device *vgdev,
@@ -122,6 +125,12 @@ static int virtio_gpu_getparam_ioctl(struct drm_device *dev, void *data,
 			return -ENOENT;
 		value = vgdev->blob_alignment;
 		break;
+	case VIRTGPU_PARAM_USERPTR:
+		value = 1;
+		break;
+	case VIRTGPU_PARAM_BLOB_READONLY:
+		value = vgdev->has_blob_readonly ? 1 : 0;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -453,11 +462,23 @@ static int verify_blob(struct virtio_gpu_device *vgdev,
 	if (rc_blob->blob_flags & ~VIRTGPU_BLOB_FLAG_USE_MASK)
 		return -EINVAL;
 
+	if (rc_blob->blob_hints & ~VIRTGPU_BLOB_HINT_MASK)
+		return -EINVAL;
+
 	if (rc_blob->blob_flags & VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE) {
 		if (!vgdev->has_resource_assign_uuid)
 			return -EINVAL;
 	}
 
+	if (rc_blob->blob_flags & VIRTGPU_BLOB_FLAG_USE_READONLY) {
+		if (!vgdev->has_blob_readonly)
+			return -EINVAL;
+	}
+
+	if (rc_blob->userptr &&
+	    rc_blob->blob_mem != VIRTGPU_BLOB_MEM_GUEST)
+		return -EINVAL;
+
 	switch (rc_blob->blob_mem) {
 	case VIRTGPU_BLOB_MEM_GUEST:
 		*guest_blob = true;
@@ -495,6 +516,7 @@ static int verify_blob(struct virtio_gpu_device *vgdev,
 	params->blob = true;
 	params->blob_flags = rc_blob->blob_flags;
 	params->blob_hints = rc_blob->blob_hints;
+	params->userptr = rc_blob->userptr;
 
 	if (vgdev->has_blob_alignment &&
 	    !IS_ALIGNED(params->size, vgdev->blob_alignment))
@@ -518,9 +540,10 @@ static int virtio_gpu_resource_create_blob_ioctl(struct drm_device *dev,
 	struct virtio_gpu_fpriv *vfpriv = file->driver_priv;
 	struct drm_virtgpu_resource_create_blob *rc_blob = data;
 
-	if (verify_blob(vgdev, vfpriv, &params, rc_blob,
-			&guest_blob, &host3d_blob))
-		return -EINVAL;
+	ret = verify_blob(vgdev, vfpriv, &params, rc_blob,
+			  &guest_blob, &host3d_blob);
+	if (ret)
+		return ret;
 
 	if (vgdev->has_virgl_3d)
 		virtio_gpu_create_context(dev, file);
@@ -538,7 +561,9 @@ static int virtio_gpu_resource_create_blob_ioctl(struct drm_device *dev,
 				      vfpriv->ctx_id, NULL, NULL);
 	}
 
-	if (guest_blob)
+	if (guest_blob && params.userptr)
+		ret = virtio_gpu_userptr_create(vgdev, file, &params, &bo);
+	else if (guest_blob)
 		ret = virtio_gpu_object_create(vgdev, &params, &bo, NULL);
 	else if (!guest_blob && host3d_blob)
 		ret = virtio_gpu_vram_create(vgdev, &params, &bo);
diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c
index 1d4d3bf46a..06c2bded49 100644
--- a/drivers/gpu/drm/virtio/virtgpu_kms.c
+++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
@@ -249,15 +249,19 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
 		vgdev->blob_alignment = blob_alignment;
 	}
 
+	if (virtio_has_feature(vgdev->vdev, VIRTIO_GPU_F_BLOB_READONLY))
+		vgdev->has_blob_readonly = true;
+
 	DRM_INFO("features: %cvirgl %cedid %cresource_blob %chost_visible",
 		 vgdev->has_virgl_3d    ? '+' : '-',
 		 vgdev->has_edid        ? '+' : '-',
 		 vgdev->has_resource_blob ? '+' : '-',
 		 vgdev->has_host_visible ? '+' : '-');
 
-	DRM_INFO("features: %ccontext_init %cblob_alignment\n",
+	DRM_INFO("features: %ccontext_init %cblob_alignment %cblob_readonly\n",
 		 vgdev->has_context_init ? '+' : '-',
-		 vgdev->has_blob_alignment ? '+' : '-');
+		 vgdev->has_blob_alignment ? '+' : '-',
+		 vgdev->has_blob_readonly ? '+' : '-');
 
 	ret = virtio_gpu_find_vqs(vgdev);
 	if (ret) {
-- 
2.34.1

Re: [PATCH v8 2/4] drm/virtgpu api: add blob userptr resource

[Akihiko Odaki]

On 2026/09/18 18:59, Honglei Huang wrote:
> Add a userptr address field so userspace can request a blob backed
> by an existing process mapping. A non-zero userptr selects that
> path; probe VIRTGPU_PARAM_USERPTR before using the field.
> 
> GPU-readonly backing is requested with the virtio CREATE_BLOB wire
> flag VIRTIO_GPU_BLOB_FLAG_USE_READONLY (also
> VIRTGPU_BLOB_FLAG_USE_READONLY). The device MUST NOT write such a
> resource. The guest pins without FOLL_WRITE only when the device
> advertised VIRTIO_GPU_F_BLOB_READONLY (VIRTGPU_PARAM_BLOB_READONLY).
> 
> Signed-off-by: Honglei Huang <honghuan@amd.com>
> ---
>   include/uapi/drm/virtgpu_drm.h  | 13 +++++++++++++
>   include/uapi/linux/virtio_gpu.h |  6 ++++++
>   2 files changed, 19 insertions(+)
> 
> diff --git a/include/uapi/drm/virtgpu_drm.h b/include/uapi/drm/virtgpu_drm.h
> index 95587e12ae..80f73b3276 100644
> --- a/include/uapi/drm/virtgpu_drm.h
> +++ b/include/uapi/drm/virtgpu_drm.h
> @@ -99,6 +99,8 @@ struct drm_virtgpu_execbuffer {
>   #define VIRTGPU_PARAM_SUPPORTED_CAPSET_IDs 7 /* Bitmask of supported capability set ids */
>   #define VIRTGPU_PARAM_EXPLICIT_DEBUG_NAME 8 /* Ability to set debug name from userspace */
>   #define VIRTGPU_PARAM_BLOB_ALIGNMENT 9 /* Device alignment requirements for blobs */
> +#define VIRTGPU_PARAM_USERPTR 10 /* CREATE_BLOB userptr field is supported */
> +#define VIRTGPU_PARAM_BLOB_READONLY 11 /* VIRTGPU_BLOB_FLAG_USE_READONLY is honored */
>   
>   struct drm_virtgpu_getparam {
>   	__u64 param;
> @@ -186,6 +188,10 @@ struct drm_virtgpu_resource_create_blob {
>   #define VIRTGPU_BLOB_FLAG_USE_MAPPABLE     0x0001
>   #define VIRTGPU_BLOB_FLAG_USE_SHAREABLE    0x0002
>   #define VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE 0x0004
> +/* Wire flag: device MUST NOT write. Guest pins without FOLL_WRITE.
> + * Rejected unless VIRTGPU_PARAM_BLOB_READONLY is 1.
> + */

According to Documentation/process/coding-style.rst, the preferred style 
for long (multi-line) comments is:

	/*
	 * This is the preferred style for multi-line
	 * comments in the Linux kernel source code.
	 * Please use it consistently.
	 *
	 * Description:  A column of asterisks on the left side,
	 * with beginning and ending almost-blank lines.
	 */

So please avoid putting text on the same line as the opening /*.

Furthermore, because this is a UAPI header (defining the interface 
between userspace and the kernel, rather than the guest and the host), 
it should use terminology appropriate for userspace. Kernel-internal 
implementation details like FOLL_WRITE and terms like "guest" shouldn't 
be mentioned here.

That being said, I don't think this comment is necessary in the first 
place. Anyone who needs to know the exact behavior will look at the 
virtio specification. I recommend just dropping the comment entirely.

> +#define VIRTGPU_BLOB_FLAG_USE_READONLY     0x0008
>   	/* zero is invalid blob_mem */
>   	__u32 blob_mem;
>   	__u32 blob_flags;
> @@ -205,6 +211,13 @@ struct drm_virtgpu_resource_create_blob {
>   #define DRM_VIRTGPU_BLOB_FLAG_HINT_DEFER_MAPPING        0x0001
>   	__u32 blob_hints;
>   	__u32 pad2;
> +
> +	/*
> +	 * Guest VA to pin as blob backing. Non-zero selects the userptr
> +	 * path and is valid only with VIRTGPU_BLOB_MEM_GUEST. Must be 0
> +	 * otherwise. Probe VIRTGPU_PARAM_USERPTR before using this field.
> +	 */

This comment is useful since it discusses UAPI specifics. However, 
please avoid the term "Guest VA". Since guest userspace has no concept 
of a "host" or "PA" (physical address), simply saying "address" is 
sufficient and more concise.

Regards,
Akihiko Odaki

> +	__u64 userptr;
>   };
>   
>   #define VIRTGPU_CONTEXT_PARAM_CAPSET_ID       0x0001
> diff --git a/include/uapi/linux/virtio_gpu.h b/include/uapi/linux/virtio_gpu.h
> index 3d4dfadc9d..33f5332e59 100644
> --- a/include/uapi/linux/virtio_gpu.h
> +++ b/include/uapi/linux/virtio_gpu.h
> @@ -72,6 +72,10 @@
>    * must be aligned to that value.
>    */
>   #define VIRTIO_GPU_F_BLOB_ALIGNMENT      5
> +/*
> + * VIRTIO_GPU_BLOB_FLAG_USE_READONLY
> + */
> +#define VIRTIO_GPU_F_BLOB_READONLY       6
>   
>   enum virtio_gpu_ctrl_type {
>   	VIRTIO_GPU_UNDEFINED = 0,
> @@ -415,6 +419,8 @@ struct virtio_gpu_resource_create_blob {
>   #define VIRTIO_GPU_BLOB_FLAG_USE_MAPPABLE     0x0001
>   #define VIRTIO_GPU_BLOB_FLAG_USE_SHAREABLE    0x0002
>   #define VIRTIO_GPU_BLOB_FLAG_USE_CROSS_DEVICE 0x0004
> +/* Device MUST NOT write. Driver may pin read-only guest pages. */
> +#define VIRTIO_GPU_BLOB_FLAG_USE_READONLY     0x0008
>   	/* zero is invalid blob mem */
>   	__le32 blob_mem;
>   	__le32 blob_flags;

Re: [PATCH v8 2/4] drm/virtgpu api: add blob userptr resource

[Huang, Honglei]

On 9/18/2026 8:12 PM, Akihiko Odaki wrote:
> On 2026/09/18 18:59, Honglei Huang wrote:
>> Add a userptr address field so userspace can request a blob backed
>> by an existing process mapping. A non-zero userptr selects that
>> path; probe VIRTGPU_PARAM_USERPTR before using the field.
>>
>> GPU-readonly backing is requested with the virtio CREATE_BLOB wire
>> flag VIRTIO_GPU_BLOB_FLAG_USE_READONLY (also
>> VIRTGPU_BLOB_FLAG_USE_READONLY). The device MUST NOT write such a
>> resource. The guest pins without FOLL_WRITE only when the device
>> advertised VIRTIO_GPU_F_BLOB_READONLY (VIRTGPU_PARAM_BLOB_READONLY).
>>
>> Signed-off-by: Honglei Huang <honghuan@amd.com>
>> ---
>>   include/uapi/drm/virtgpu_drm.h  | 13 +++++++++++++
>>   include/uapi/linux/virtio_gpu.h |  6 ++++++
>>   2 files changed, 19 insertions(+)
>>
>> diff --git a/include/uapi/drm/virtgpu_drm.h b/include/uapi/drm/ 
>> virtgpu_drm.h
>> index 95587e12ae..80f73b3276 100644
>> --- a/include/uapi/drm/virtgpu_drm.h
>> +++ b/include/uapi/drm/virtgpu_drm.h
>> @@ -99,6 +99,8 @@ struct drm_virtgpu_execbuffer {
>>   #define VIRTGPU_PARAM_SUPPORTED_CAPSET_IDs 7 /* Bitmask of supported 
>> capability set ids */
>>   #define VIRTGPU_PARAM_EXPLICIT_DEBUG_NAME 8 /* Ability to set debug 
>> name from userspace */
>>   #define VIRTGPU_PARAM_BLOB_ALIGNMENT 9 /* Device alignment 
>> requirements for blobs */
>> +#define VIRTGPU_PARAM_USERPTR 10 /* CREATE_BLOB userptr field is 
>> supported */
>> +#define VIRTGPU_PARAM_BLOB_READONLY 11 /* 
>> VIRTGPU_BLOB_FLAG_USE_READONLY is honored */
>>   struct drm_virtgpu_getparam {
>>       __u64 param;
>> @@ -186,6 +188,10 @@ struct drm_virtgpu_resource_create_blob {
>>   #define VIRTGPU_BLOB_FLAG_USE_MAPPABLE     0x0001
>>   #define VIRTGPU_BLOB_FLAG_USE_SHAREABLE    0x0002
>>   #define VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE 0x0004
>> +/* Wire flag: device MUST NOT write. Guest pins without FOLL_WRITE.
>> + * Rejected unless VIRTGPU_PARAM_BLOB_READONLY is 1.
>> + */
> 
> According to Documentation/process/coding-style.rst, the preferred style 
> for long (multi-line) comments is:
> 
>      /*
>       * This is the preferred style for multi-line
>       * comments in the Linux kernel source code.
>       * Please use it consistently.
>       *
>       * Description:  A column of asterisks on the left side,
>       * with beginning and ending almost-blank lines.
>       */
> 
> So please avoid putting text on the same line as the opening /*.
> 
> Furthermore, because this is a UAPI header (defining the interface 
> between userspace and the kernel, rather than the guest and the host), 
> it should use terminology appropriate for userspace. Kernel-internal 
> implementation details like FOLL_WRITE and terms like "guest" shouldn't 
> be mentioned here.
> 
> That being said, I don't think this comment is necessary in the first 
> place. Anyone who needs to know the exact behavior will look at the 
> virtio specification. I recommend just dropping the comment entirely.
> 

Thanks for the review, will remove this comment here.

>> +#define VIRTGPU_BLOB_FLAG_USE_READONLY     0x0008
>>       /* zero is invalid blob_mem */
>>       __u32 blob_mem;
>>       __u32 blob_flags;
>> @@ -205,6 +211,13 @@ struct drm_virtgpu_resource_create_blob {
>>   #define DRM_VIRTGPU_BLOB_FLAG_HINT_DEFER_MAPPING        0x0001
>>       __u32 blob_hints;
>>       __u32 pad2;
>> +
>> +    /*
>> +     * Guest VA to pin as blob backing. Non-zero selects the userptr
>> +     * path and is valid only with VIRTGPU_BLOB_MEM_GUEST. Must be 0
>> +     * otherwise. Probe VIRTGPU_PARAM_USERPTR before using this field.
>> +     */
> 
> This comment is useful since it discusses UAPI specifics. However, 
> please avoid the term "Guest VA". Since guest userspace has no concept 
> of a "host" or "PA" (physical address), simply saying "address" is 
> sufficient and more concise.

Got it, will modify the comment in next version.

Regards,
Honglei

> 
> Regards,
> Akihiko Odaki
> 
>> +    __u64 userptr;
>>   };
>>   #define VIRTGPU_CONTEXT_PARAM_CAPSET_ID       0x0001
>> diff --git a/include/uapi/linux/virtio_gpu.h b/include/uapi/linux/ 
>> virtio_gpu.h
>> index 3d4dfadc9d..33f5332e59 100644
>> --- a/include/uapi/linux/virtio_gpu.h
>> +++ b/include/uapi/linux/virtio_gpu.h
>> @@ -72,6 +72,10 @@
>>    * must be aligned to that value.
>>    */
>>   #define VIRTIO_GPU_F_BLOB_ALIGNMENT      5
>> +/*
>> + * VIRTIO_GPU_BLOB_FLAG_USE_READONLY
>> + */
>> +#define VIRTIO_GPU_F_BLOB_READONLY       6
>>   enum virtio_gpu_ctrl_type {
>>       VIRTIO_GPU_UNDEFINED = 0,
>> @@ -415,6 +419,8 @@ struct virtio_gpu_resource_create_blob {
>>   #define VIRTIO_GPU_BLOB_FLAG_USE_MAPPABLE     0x0001
>>   #define VIRTIO_GPU_BLOB_FLAG_USE_SHAREABLE    0x0002
>>   #define VIRTIO_GPU_BLOB_FLAG_USE_CROSS_DEVICE 0x0004
>> +/* Device MUST NOT write. Driver may pin read-only guest pages. */
>> +#define VIRTIO_GPU_BLOB_FLAG_USE_READONLY     0x0008
>>       /* zero is invalid blob mem */
>>       __le32 blob_mem;
>>       __le32 blob_flags;
> 

Re: [PATCH v8 3/4] drm/virtio: implement userptr support for zero-copy memory access

[Akihiko Odaki]

On 2026/09/18 18:59, Honglei Huang wrote:
> Add userptr blob objects so the guest kernel can pin an existing
> userspace mapping and advertise it as CREATE_BLOB backing entries.
> 
> - New virtio_gpu_object_userptr type for userptr resources
> - Pin pages with pin_user_pages_fast() and FOLL_LONGTERM
> - Omit FOLL_WRITE when VIRTGPU_BLOB_FLAG_USE_READONLY is set
> - Charge FOLL_LONGTERM pins against RLIMIT_MEMLOCK
> - DMA-map the scatterlist only when virtio_gpu_use_dma_api() is
>    required; use DMA_TO_DEVICE for USE_READONLY blobs
> - Sync userptr SG for the device on TRANSFER_TO_HOST
> - Mark writable pages dirty when unpinning
> - Keep pages pinned until RESOURCE_UNREF is queued; drop them from
>    cleanup_object() on the unref response or on create failure
> - Clear userptr->pages on pin failure to avoid double-free on cleanup
> - Reject unaligned or overflowing userptr ranges at create time
> - Disallow PRIME export of userptr objects
> - Save CREATE_BLOB params and restore userptr resources after
>    hibernation without using the shmem restore path
> 
> Signed-off-by: Honglei Huang <honghuan@amd.com>
> ---
>   drivers/gpu/drm/virtio/Makefile          |   3 +-
>   drivers/gpu/drm/virtio/virtgpu_drv.h     |  43 +++
>   drivers/gpu/drm/virtio/virtgpu_object.c  |  22 ++
>   drivers/gpu/drm/virtio/virtgpu_userptr.c | 365 +++++++++++++++++++++++
>   drivers/gpu/drm/virtio/virtgpu_vq.c      |  33 +-
>   5 files changed, 456 insertions(+), 10 deletions(-)
>   create mode 100644 drivers/gpu/drm/virtio/virtgpu_userptr.c
> 
> diff --git a/drivers/gpu/drm/virtio/Makefile b/drivers/gpu/drm/virtio/Makefile
> index d2e1788a82..fe7332a621 100644
> --- a/drivers/gpu/drm/virtio/Makefile
> +++ b/drivers/gpu/drm/virtio/Makefile
> @@ -6,6 +6,7 @@
>   virtio-gpu-y := virtgpu_drv.o virtgpu_kms.o virtgpu_gem.o virtgpu_vram.o \
>   	virtgpu_display.o virtgpu_vq.o \
>   	virtgpu_fence.o virtgpu_object.o virtgpu_debugfs.o virtgpu_plane.o \
> -	virtgpu_ioctl.o virtgpu_prime.o virtgpu_trace_points.o virtgpu_submit.o
> +	virtgpu_ioctl.o virtgpu_prime.o virtgpu_trace_points.o virtgpu_submit.o \
> +	virtgpu_userptr.o
>   
>   obj-$(CONFIG_DRM_VIRTIO_GPU) += virtio-gpu.o
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
> index 9df4c71173..e0941cc187 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
> @@ -105,6 +105,7 @@ struct virtio_gpu_object_params {
>   	uint32_t blob_flags;
>   	uint64_t blob_id;
>   	uint32_t blob_hints;
> +	uint64_t userptr;
>   };
>   
>   struct virtio_gpu_object {
> @@ -138,12 +139,42 @@ struct virtio_gpu_object_vram {
>   	struct drm_mm_node vram_node;
>   };
>   
> +struct virtio_gpu_object_userptr;
> +
> +struct virtio_gpu_object_userptr_ops {
> +	int (*get_pages)(struct virtio_gpu_object_userptr *userptr);
> +	void (*put_pages)(struct virtio_gpu_object_userptr *userptr);
> +};
> +
> +struct virtio_gpu_object_userptr {
> +	struct virtio_gpu_object base;
> +	const struct virtio_gpu_object_userptr_ops *ops;
> +	/* Protects pages and sgt. */
> +	struct mutex lock;
> +
> +	uint64_t start;
> +	uint32_t npages;
> +	uint32_t bo_handle;
> +	uint32_t flags;
> +
> +	struct virtio_gpu_device *vgdev;
> +	struct drm_file *file;
> +	struct page **pages;
> +	struct sg_table *sgt;
> +	bool dma_mapped;
> +	enum dma_data_direction dma_dir;
> +	struct mm_struct *mm;
> +};
> +
>   #define to_virtio_gpu_shmem(virtio_gpu_object) \
>   	container_of((virtio_gpu_object), struct virtio_gpu_object_shmem, base)
>   
>   #define to_virtio_gpu_vram(virtio_gpu_object) \
>   	container_of((virtio_gpu_object), struct virtio_gpu_object_vram, base)
>   
> +#define to_virtio_gpu_userptr(virtio_gpu_object) \
> +	container_of((virtio_gpu_object), struct virtio_gpu_object_userptr, base)
> +
>   struct virtio_gpu_object_array {
>   	struct ww_acquire_ctx ticket;
>   	struct list_head next;
> @@ -284,6 +315,7 @@ struct virtio_gpu_device {
>   	bool has_host_visible;
>   	bool has_context_init;
>   	bool has_blob_alignment;
> +	bool has_blob_readonly;
>   	bool hibernated;
>   	struct virtio_shm_region host_visible_region;
>   	struct drm_mm host_visible_mm;
> @@ -562,4 +594,15 @@ void virtio_gpu_vram_map_deferred(struct virtio_gpu_object_vram *vram);
>   int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
>   				struct drm_file *file);
>   
> +/* virtgpu_userptr.c */
> +int virtio_gpu_userptr_create(struct virtio_gpu_device *vgdev,
> +			      struct drm_file *file,
> +			      struct virtio_gpu_object_params *params,
> +			      struct virtio_gpu_object **bo_ptr);
> +bool virtio_gpu_is_userptr(struct virtio_gpu_object *bo);
> +void virtio_gpu_userptr_dma_sync_for_device(struct virtio_gpu_object *bo);
> +int virtio_gpu_userptr_restore(struct virtio_gpu_device *vgdev,
> +			       struct virtio_gpu_object *bo,
> +			       struct virtio_gpu_mem_entry **ents,
> +			       unsigned int *nents);
>   #endif
> diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
> index 49899485be..ab21494b1c 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_object.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_object.c
> @@ -91,6 +91,16 @@ void virtio_gpu_cleanup_object(struct virtio_gpu_object *bo)
>   		drm_gem_free_mmap_offset(&vram->base.base.base);
>   		drm_gem_object_release(&vram->base.base.base);
>   		kfree(vram);
> +	} else if (virtio_gpu_is_userptr(bo)) {
> +		struct virtio_gpu_object_userptr *userptr =
> +			to_virtio_gpu_userptr(bo);
> +
> +		mutex_lock(&userptr->lock);
> +		userptr->ops->put_pages(userptr);
> +		mutex_unlock(&userptr->lock);
> +		mutex_destroy(&userptr->lock);
> +		drm_gem_object_release(&userptr->base.base.base);
> +		kfree(userptr);
>   	} else {
>   		drm_gem_object_release(&bo->base.base);
>   		kfree(bo);
> @@ -316,6 +326,18 @@ int virtio_gpu_object_restore_all(struct virtio_gpu_device *vgdev)
>   			continue;
>   		}
>   
> +		if (virtio_gpu_is_userptr(bo)) {
> +			ret = virtio_gpu_userptr_restore(vgdev, bo, &ents,
> +							 &nents);
> +			if (ret)
> +				break;
> +
> +			virtio_gpu_cmd_resource_create_blob(vgdev, bo,
> +							    &bo->params,
> +							    ents, nents);
> +			continue;
> +		}
> +
>   		if (bo->params.blob || bo->attached) {
>   			ret = virtio_gpu_object_shmem_init(vgdev, bo, &ents,
>   							   &nents);
> diff --git a/drivers/gpu/drm/virtio/virtgpu_userptr.c b/drivers/gpu/drm/virtio/virtgpu_userptr.c
> new file mode 100644
> index 0000000000..ccfd96844e
> --- /dev/null
> +++ b/drivers/gpu/drm/virtio/virtgpu_userptr.c
> @@ -0,0 +1,365 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/dma-mapping.h>
> +#include <linux/limits.h>
> +#include <linux/mm.h>
> +#include <linux/overflow.h>
> +#include <linux/pid.h>
> +#include <linux/sched/mm.h>
> +#include <linux/sched/signal.h>
> +#include <linux/vmalloc.h>
> +
> +#include "virtgpu_drv.h"
> +#include <drm/drm_gem.h>
> +
> +static void virtio_gpu_userptr_free(struct drm_gem_object *obj)
> +{
> +	struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(obj);
> +	struct virtio_gpu_device *vgdev = obj->dev->dev_private;
> +
> +	/*
> +	 * Keep pages pinned until RESOURCE_UNREF completes. The response
> +	 * callback calls virtio_gpu_cleanup_object(), which drops them.
> +	 */
> +	if (bo->created) {
> +		virtio_gpu_remove_from_restore_list(bo);
> +		virtio_gpu_cmd_unref_resource(vgdev, bo, false);
> +		virtio_gpu_notify(vgdev);
> +		return;
> +	}
> +
> +	virtio_gpu_cleanup_object(bo);
> +}
> +
> +static struct dma_buf *
> +virtio_gpu_userptr_prime_export(struct drm_gem_object *obj, int flags)
> +{
> +	return ERR_PTR(-EINVAL);
> +}
> +
> +static const struct drm_gem_object_funcs virtio_gpu_userptr_funcs = {
> +	.open = virtio_gpu_gem_object_open,
> +	.close = virtio_gpu_gem_object_close,
> +	.free = virtio_gpu_userptr_free,
> +	.export = virtio_gpu_userptr_prime_export,
> +};
> +
> +bool virtio_gpu_is_userptr(struct virtio_gpu_object *bo)
> +{
> +	return bo->base.base.funcs == &virtio_gpu_userptr_funcs;
> +}
> +
> +void virtio_gpu_userptr_dma_sync_for_device(struct virtio_gpu_object *bo)
> +{
> +	struct virtio_gpu_object_userptr *userptr = to_virtio_gpu_userptr(bo);
> +	struct device *dev;
> +
> +	if (!userptr->dma_mapped)
> +		return;
> +
> +	dev = drm_dev_dma_dev(userptr->base.base.base.dev);
> +	dma_sync_sgtable_for_device(dev, userptr->sgt, DMA_TO_DEVICE);
> +}
> +
> +static int
> +virtio_gpu_userptr_get_pages(struct virtio_gpu_object_userptr *userptr)
> +{
> +	unsigned int flag = FOLL_LONGTERM;
> +	unsigned int num_pages, pinned = 0;
> +	int ret = 0;
> +
> +	if (userptr->pages)
> +		return 0;
> +
> +	userptr->pages = kvmalloc_array(userptr->npages, sizeof(struct page *),
> +					GFP_KERNEL);
> +	if (!userptr->pages)
> +		return -ENOMEM;
> +
> +	if (!(userptr->flags & VIRTGPU_BLOB_FLAG_USE_READONLY))
> +		flag |= FOLL_WRITE;
> +
> +	do {
> +		num_pages = userptr->npages - pinned;
> +
> +		ret = pin_user_pages_fast(userptr->start + pinned * PAGE_SIZE,
> +					  num_pages, flag,
> +					  userptr->pages + pinned);
> +
> +		if (ret < 0) {
> +			if (pinned)
> +				unpin_user_pages(userptr->pages, pinned);
> +			kvfree(userptr->pages);
> +			userptr->pages = NULL;
> +			return ret;
> +		}
> +
> +		pinned += ret;
> +
> +	} while (pinned < userptr->npages);
> +
> +	return 0;
> +}
> +
> +static void
> +virtio_gpu_userptr_unaccount(struct virtio_gpu_object_userptr *userptr)
> +{
> +	if (!userptr->mm)
> +		return;
> +
> +	atomic64_sub(userptr->npages, &userptr->mm->pinned_vm);
> +	mmdrop(userptr->mm);
> +	userptr->mm = NULL;
> +}
> +
> +static void
> +virtio_gpu_userptr_put_pages(struct virtio_gpu_object_userptr *userptr)
> +{
> +	struct drm_device *dev = userptr->base.base.base.dev;
> +
> +	if (userptr->sgt) {
> +		if (userptr->dma_mapped)
> +			dma_unmap_sgtable(drm_dev_dma_dev(dev), userptr->sgt,
> +					  userptr->dma_dir, 0);
> +		userptr->dma_mapped = false;
> +		sg_free_table(userptr->sgt);
> +		kfree(userptr->sgt);
> +		userptr->sgt = NULL;
> +	}
> +
> +	if (userptr->pages) {
> +		bool dirty = !(userptr->flags & VIRTGPU_BLOB_FLAG_USE_READONLY);
> +
> +		unpin_user_pages_dirty_lock(userptr->pages, userptr->npages,
> +					    dirty);
> +		kvfree(userptr->pages);
> +		userptr->pages = NULL;
> +	}
> +
> +	virtio_gpu_userptr_unaccount(userptr);
> +}
> +
> +static int
> +virtio_gpu_userptr_get_entries(struct virtio_gpu_device *vgdev,
> +			       struct virtio_gpu_object_userptr *userptr,
> +			       struct virtio_gpu_mem_entry **ents,
> +			       unsigned int *nents)
> +{
> +	bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
> +	struct scatterlist *sg;
> +	unsigned int count;
> +	int si;
> +
> +	count = use_dma_api ? userptr->sgt->nents : userptr->sgt->orig_nents;
> +	if (!count)
> +		return -EINVAL;
> +
> +	*ents = kvmalloc_array(count, sizeof(**ents), GFP_KERNEL);
> +	if (!*ents)
> +		return -ENOMEM;
> +
> +	if (use_dma_api) {
> +		for_each_sgtable_dma_sg(userptr->sgt, sg, si) {
> +			(*ents)[si].addr = cpu_to_le64(sg_dma_address(sg));
> +			(*ents)[si].length = cpu_to_le32(sg_dma_len(sg));
> +			(*ents)[si].padding = 0;
> +		}
> +	} else {
> +		for_each_sgtable_sg(userptr->sgt, sg, si) {
> +			(*ents)[si].addr = cpu_to_le64(sg_phys(sg));
> +			(*ents)[si].length = cpu_to_le32(sg->length);
> +			(*ents)[si].padding = 0;
> +		}
> +	}
> +
> +	*nents = count;
> +	return 0;
> +}
> +
> +int virtio_gpu_userptr_restore(struct virtio_gpu_device *vgdev,
> +			       struct virtio_gpu_object *bo,
> +			       struct virtio_gpu_mem_entry **ents,
> +			       unsigned int *nents)
> +{
> +	struct virtio_gpu_object_userptr *userptr = to_virtio_gpu_userptr(bo);
> +	int ret;
> +
> +	mutex_lock(&userptr->lock);
> +	if (!userptr->sgt || !userptr->pages) {
> +		mutex_unlock(&userptr->lock);
> +		return -EINVAL;
> +	}
> +
> +	if (userptr->dma_mapped) {
> +		struct device *dev = drm_dev_dma_dev(vgdev->ddev);
> +
> +		dma_unmap_sgtable(dev, userptr->sgt, userptr->dma_dir, 0);
> +		userptr->dma_mapped = false;
> +		ret = dma_map_sgtable(dev, userptr->sgt, userptr->dma_dir, 0);

This maps with attributes 0, allowing bounce buffers instead of
"zero-copy memory access". It is also unclear what coherence guarantee 
the UAPI is intended to provide.

> +		if (ret) {
> +			mutex_unlock(&userptr->lock);
> +			return ret;
> +		}
> +		userptr->dma_mapped = true;
> +	}
> +
> +	ret = virtio_gpu_userptr_get_entries(vgdev, userptr, ents, nents);
> +	mutex_unlock(&userptr->lock);
> +	return ret;
> +}
> +
> +static int
> +virtio_gpu_userptr_init(struct drm_device *dev, struct drm_file *file,
> +			struct virtio_gpu_object_userptr *userptr,
> +			struct virtio_gpu_object_params *params,
> +			const struct virtio_gpu_object_userptr_ops *ops)
> +{
> +	struct drm_gem_object *obj;
> +	int ret;
> +
> +	userptr->start = params->userptr;
> +	userptr->npages = params->size >> PAGE_SHIFT;
> +	userptr->flags = params->blob_flags;
> +
> +	mutex_init(&userptr->lock);
> +	userptr->vgdev = dev->dev_private;
> +	userptr->file = file;
> +	userptr->ops = ops;
> +
> +	/*
> +	 * Allocate the resource id before GEM init so a failure here can
> +	 * unwind with a plain kfree and does not need a special id=0 guard
> +	 * in the shared resource_id_put helper.
> +	 */
> +	ret = virtio_gpu_resource_id_get(userptr->vgdev,
> +					 &userptr->base.hw_res_handle);
> +	if (ret) {
> +		mutex_destroy(&userptr->lock);
> +		return ret;
> +	}
> +
> +	obj = &userptr->base.base.base;
> +	obj->funcs = &virtio_gpu_userptr_funcs;
> +
> +	drm_gem_private_object_init(dev, obj, params->size);
> +	INIT_LIST_HEAD(&userptr->base.restore_node);
> +
> +	return 0;
> +}
> +
> +static const struct virtio_gpu_object_userptr_ops virtio_gpu_userptr_ops = {
> +	.get_pages = virtio_gpu_userptr_get_pages,
> +	.put_pages = virtio_gpu_userptr_put_pages,
> +};
> +
> +int virtio_gpu_userptr_create(struct virtio_gpu_device *vgdev,
> +			      struct drm_file *file,
> +			      struct virtio_gpu_object_params *params,
> +			      struct virtio_gpu_object **bo_ptr)
> +{
> +	struct virtio_gpu_object_userptr *userptr;
> +	struct virtio_gpu_mem_entry *ents = NULL;
> +	struct sg_table *sgt;
> +	struct mm_struct *mm;
> +	unsigned long lock_limit;
> +	unsigned long start;
> +	unsigned long end;
> +	s64 new_pinned;
> +	unsigned int nents;
> +	int ret;
> +
> +	*bo_ptr = NULL;
> +
> +	if (!params->size || !IS_ALIGNED(params->size, PAGE_SIZE) ||
> +	    params->userptr != (unsigned long)params->userptr)
> +		return -EINVAL;
> +
> +	start = params->userptr;
> +	if (!IS_ALIGNED(start, PAGE_SIZE) ||
> +	    check_add_overflow(start, (unsigned long)params->size, &end))
> +		return -EINVAL;
> +
> +	if (!can_do_mlock())
> +		return -EPERM;
> +
> +	if (params->size >> PAGE_SHIFT > INT_MAX)
> +		return -E2BIG;
> +
> +	if (!access_ok((void __user *)start, params->size))
> +		return -EFAULT;
> +
> +	userptr = kzalloc_obj(*userptr);
> +	if (!userptr)
> +		return -ENOMEM;
> +
> +	ret = virtio_gpu_userptr_init(vgdev->ddev, file, userptr, params,
> +				      &virtio_gpu_userptr_ops);
> +	if (ret) {
> +		kfree(userptr);
> +		return ret;
> +	}
> +
> +	mm = current->mm;
> +	mmgrab(mm);
> +	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> +	new_pinned = atomic64_add_return(userptr->npages, &mm->pinned_vm);
> +	if (new_pinned < 0 ||
> +	    (new_pinned > lock_limit && !capable(CAP_IPC_LOCK))) {
> +		atomic64_sub(userptr->npages, &mm->pinned_vm);
> +		mmdrop(mm);
> +		ret = new_pinned < 0 ? -EOVERFLOW : -ENOMEM;
> +		goto err_cleanup;
> +	}
> +	userptr->mm = mm;
> +
> +	mutex_lock(&userptr->lock);
> +	ret = userptr->ops->get_pages(userptr);
> +	mutex_unlock(&userptr->lock);
> +	if (ret)
> +		goto err_cleanup;
> +
> +	sgt = drm_prime_pages_to_sg(vgdev->ddev, userptr->pages,
> +				    userptr->npages);
> +	if (IS_ERR(sgt)) {
> +		ret = PTR_ERR(sgt);
> +		goto err_cleanup;
> +	}
> +
> +	userptr->sgt = sgt;
> +
> +	/*
> +	 * Match shmem blobs: only DMA-map when the virtio DMA API is in
> +	 * use. Mapping unconditionally can create SWIOTLB bounce buffers
> +	 * that get copied back over guest pages on unmap even though the
> +	 * host was given sg_phys() addresses.
> +	 */
> +	if (virtio_gpu_use_dma_api(vgdev->vdev)) {
> +		enum dma_data_direction dir =
> +			(userptr->flags & VIRTGPU_BLOB_FLAG_USE_READONLY) ?
> +			DMA_TO_DEVICE : DMA_BIDIRECTIONAL;
> +
> +		ret = dma_map_sgtable(drm_dev_dma_dev(vgdev->ddev), sgt,
> +				      dir, 0);
> +		if (ret)
> +			goto err_cleanup;
> +
> +		userptr->dma_dir = dir;
> +		userptr->dma_mapped = true;
> +	}
> +
> +	ret = virtio_gpu_userptr_get_entries(vgdev, userptr, &ents, &nents);
> +	if (ret)
> +		goto err_cleanup;
> +
> +	virtio_gpu_cmd_resource_create_blob(vgdev, &userptr->base, params, ents,
> +					    nents);
> +
> +	userptr->base.params = *params;
> +	virtio_gpu_add_object_to_restore_list(vgdev, &userptr->base);
> +
> +	*bo_ptr = &userptr->base;
> +	return 0;
> +
> +err_cleanup:
> +	virtio_gpu_cleanup_object(&userptr->base);
> +	return ret;
> +}
> diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
> index c02c03c10d..dcbd7bb7a6 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_vq.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
> @@ -781,9 +781,14 @@ int virtio_gpu_panic_cmd_transfer_to_host_2d(struct virtio_gpu_device *vgdev,
>   	struct virtio_gpu_vbuffer *vbuf;
>   	bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
>   
> -	if (virtio_gpu_is_shmem(bo) && use_dma_api)
> -		dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
> -					    bo->base.sgt, DMA_TO_DEVICE);
> +	if (use_dma_api) {
> +		if (virtio_gpu_is_shmem(bo))
> +			dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
> +						    bo->base.sgt,
> +						    DMA_TO_DEVICE);
> +		else if (virtio_gpu_is_userptr(bo))
> +			virtio_gpu_userptr_dma_sync_for_device(bo);
> +	}
>   
>   	cmd_p = virtio_gpu_panic_alloc_cmd_resp(vgdev, &vbuf, sizeof(*cmd_p));
>   	memset(cmd_p, 0, sizeof(*cmd_p));
> @@ -812,9 +817,14 @@ void virtio_gpu_cmd_transfer_to_host_2d(struct virtio_gpu_device *vgdev,
>   	struct virtio_gpu_vbuffer *vbuf;
>   	bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
>   
> -	if (virtio_gpu_is_shmem(bo) && use_dma_api)
> -		dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
> -					    bo->base.sgt, DMA_TO_DEVICE);
> +	if (use_dma_api) {
> +		if (virtio_gpu_is_shmem(bo))
> +			dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
> +						    bo->base.sgt,
> +						    DMA_TO_DEVICE);
> +		else if (virtio_gpu_is_userptr(bo))
> +			virtio_gpu_userptr_dma_sync_for_device(bo);
> +	}
>   
>   	cmd_p = virtio_gpu_alloc_cmd(vgdev, &vbuf, sizeof(*cmd_p));
>   	memset(cmd_p, 0, sizeof(*cmd_p));
> @@ -1245,9 +1255,14 @@ void virtio_gpu_cmd_transfer_to_host_3d(struct virtio_gpu_device *vgdev,
>   	struct virtio_gpu_vbuffer *vbuf;
>   	bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
>   
> -	if (virtio_gpu_is_shmem(bo) && use_dma_api)
> -		dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
> -					    bo->base.sgt, DMA_TO_DEVICE);
> +	if (use_dma_api) {
> +		if (virtio_gpu_is_shmem(bo))
> +			dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
> +						    bo->base.sgt,
> +						    DMA_TO_DEVICE);
> +		else if (virtio_gpu_is_userptr(bo))
> +			virtio_gpu_userptr_dma_sync_for_device(bo);

This code is ineffective since the transfer ioctl rejects 
VIRTGPU_BLOB_MEM_GUEST.

Regards,
Akihiko Odaki

Re: [PATCH v8 4/4] drm/virtio: wire blob ioctl creation to userptr objects

[Akihiko Odaki]

On 2026/09/18 18:59, Honglei Huang wrote:
> Integrate userptr into the blob resource creation ioctl.
> 
> - A non-zero userptr selects virtio_gpu_userptr_create()
> - Reject userptr unless blob_mem is VIRTGPU_BLOB_MEM_GUEST
> - Reject VIRTGPU_BLOB_FLAG_USE_READONLY unless the device
>    advertised VIRTIO_GPU_F_BLOB_READONLY
> - Advertise VIRTGPU_PARAM_USERPTR and VIRTGPU_PARAM_BLOB_READONLY
> 
> Signed-off-by: Honglei Huang <honghuan@amd.com>
> ---
>   drivers/gpu/drm/virtio/virtgpu_debugfs.c |  1 +
>   drivers/gpu/drm/virtio/virtgpu_ioctl.c   | 35 ++++++++++++++++++++----
>   drivers/gpu/drm/virtio/virtgpu_kms.c     |  8 ++++--
>   3 files changed, 37 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/virtio/virtgpu_debugfs.c b/drivers/gpu/drm/virtio/virtgpu_debugfs.c
> index 3a68a16b58..b8b9b40584 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_debugfs.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_debugfs.c
> @@ -55,6 +55,7 @@ static int virtio_gpu_features(struct seq_file *m, void *data)
>   			    vgdev->has_resource_assign_uuid);
>   
>   	virtio_gpu_add_bool(m, "blob resources", vgdev->has_resource_blob);
> +	virtio_gpu_add_bool(m, "blob readonly", vgdev->has_blob_readonly);
>   	virtio_gpu_add_bool(m, "context init", vgdev->has_context_init);
>   	virtio_gpu_add_int(m, "cap sets", vgdev->num_capsets);
>   	virtio_gpu_add_int(m, "scanouts", vgdev->num_scanouts);
> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> index 3d8e4ccdb7..3dc058e50e 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> @@ -36,7 +36,10 @@
>   
>   #define VIRTGPU_BLOB_FLAG_USE_MASK (VIRTGPU_BLOB_FLAG_USE_MAPPABLE | \
>   				    VIRTGPU_BLOB_FLAG_USE_SHAREABLE | \
> -				    VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE)
> +				    VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE | \
> +				    VIRTGPU_BLOB_FLAG_USE_READONLY)
> +
> +#define VIRTGPU_BLOB_HINT_MASK DRM_VIRTGPU_BLOB_FLAG_HINT_DEFER_MAPPING
>   
>   /* Must be called with &virtio_gpu_fpriv.struct_mutex held. */
>   static void virtio_gpu_create_context_locked(struct virtio_gpu_device *vgdev,
> @@ -122,6 +125,12 @@ static int virtio_gpu_getparam_ioctl(struct drm_device *dev, void *data,
>   			return -ENOENT;
>   		value = vgdev->blob_alignment;
>   		break;
> +	case VIRTGPU_PARAM_USERPTR:
> +		value = 1;
> +		break;
> +	case VIRTGPU_PARAM_BLOB_READONLY:
> +		value = vgdev->has_blob_readonly ? 1 : 0;
> +		break;
>   	default:
>   		return -EINVAL;
>   	}
> @@ -453,11 +462,23 @@ static int verify_blob(struct virtio_gpu_device *vgdev,
>   	if (rc_blob->blob_flags & ~VIRTGPU_BLOB_FLAG_USE_MASK)
>   		return -EINVAL;
>   
> +	if (rc_blob->blob_hints & ~VIRTGPU_BLOB_HINT_MASK)
> +		return -EINVAL;
> +
>   	if (rc_blob->blob_flags & VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE) {
>   		if (!vgdev->has_resource_assign_uuid)
>   			return -EINVAL;
>   	}
>   
> +	if (rc_blob->blob_flags & VIRTGPU_BLOB_FLAG_USE_READONLY) {
> +		if (!vgdev->has_blob_readonly)
> +			return -EINVAL;
> +	}
> +
> +	if (rc_blob->userptr &&
> +	    rc_blob->blob_mem != VIRTGPU_BLOB_MEM_GUEST)
> +		return -EINVAL;
> +
>   	switch (rc_blob->blob_mem) {
>   	case VIRTGPU_BLOB_MEM_GUEST:
>   		*guest_blob = true;
> @@ -495,6 +516,7 @@ static int verify_blob(struct virtio_gpu_device *vgdev,
>   	params->blob = true;
>   	params->blob_flags = rc_blob->blob_flags;
>   	params->blob_hints = rc_blob->blob_hints;
> +	params->userptr = rc_blob->userptr;
>   
>   	if (vgdev->has_blob_alignment &&
>   	    !IS_ALIGNED(params->size, vgdev->blob_alignment))
> @@ -518,9 +540,10 @@ static int virtio_gpu_resource_create_blob_ioctl(struct drm_device *dev,
>   	struct virtio_gpu_fpriv *vfpriv = file->driver_priv;
>   	struct drm_virtgpu_resource_create_blob *rc_blob = data;
>   
> -	if (verify_blob(vgdev, vfpriv, &params, rc_blob,
> -			&guest_blob, &host3d_blob))
> -		return -EINVAL;
> +	ret = verify_blob(vgdev, vfpriv, &params, rc_blob,
> +			  &guest_blob, &host3d_blob);
> +	if (ret)
> +		return ret;
>   
>   	if (vgdev->has_virgl_3d)
>   		virtio_gpu_create_context(dev, file);
> @@ -538,7 +561,9 @@ static int virtio_gpu_resource_create_blob_ioctl(struct drm_device *dev,
>   				      vfpriv->ctx_id, NULL, NULL);
>   	}
>   
> -	if (guest_blob)
> +	if (guest_blob && params.userptr)
> +		ret = virtio_gpu_userptr_create(vgdev, file, &params, &bo);
> +	else if (guest_blob)
>   		ret = virtio_gpu_object_create(vgdev, &params, &bo, NULL);
>   	else if (!guest_blob && host3d_blob)
>   		ret = virtio_gpu_vram_create(vgdev, &params, &bo);
> diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c
> index 1d4d3bf46a..06c2bded49 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_kms.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
> @@ -249,15 +249,19 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
>   		vgdev->blob_alignment = blob_alignment;
>   	}
>   
> +	if (virtio_has_feature(vgdev->vdev, VIRTIO_GPU_F_BLOB_READONLY))

This hits BUG(). It queries queries VIRTIO_GPU_F_BLOB_READONLY, but the 
feature is absent from the driver’s features[]. virtio_has_feature() 
validates device-specific queries through 
virtio_check_driver_offered_feature(), which executes BUG() for an 
unregistered feature. This affects ordinary probe regardless of host 
support.

Please add the feature to the array and ensure that the patch is 
properly tested before submission.

Regards,
Akihiko Odaki

> +		vgdev->has_blob_readonly = true;
> +
>   	DRM_INFO("features: %cvirgl %cedid %cresource_blob %chost_visible",
>   		 vgdev->has_virgl_3d    ? '+' : '-',
>   		 vgdev->has_edid        ? '+' : '-',
>   		 vgdev->has_resource_blob ? '+' : '-',
>   		 vgdev->has_host_visible ? '+' : '-');
>   
> -	DRM_INFO("features: %ccontext_init %cblob_alignment\n",
> +	DRM_INFO("features: %ccontext_init %cblob_alignment %cblob_readonly\n",
>   		 vgdev->has_context_init ? '+' : '-',
> -		 vgdev->has_blob_alignment ? '+' : '-');
> +		 vgdev->has_blob_alignment ? '+' : '-',
> +		 vgdev->has_blob_readonly ? '+' : '-');
>   
>   	ret = virtio_gpu_find_vqs(vgdev);
>   	if (ret) {

Re: [PATCH v8 3/4] drm/virtio: implement userptr support for zero-copy memory access

[Huang, Honglei]

On 9/19/2026 4:59 PM, Akihiko Odaki wrote:
> On 2026/09/18 18:59, Honglei Huang wrote:
>> Add userptr blob objects so the guest kernel can pin an existing
>> userspace mapping and advertise it as CREATE_BLOB backing entries.
>>
>> - New virtio_gpu_object_userptr type for userptr resources
>> - Pin pages with pin_user_pages_fast() and FOLL_LONGTERM
>> - Omit FOLL_WRITE when VIRTGPU_BLOB_FLAG_USE_READONLY is set
>> - Charge FOLL_LONGTERM pins against RLIMIT_MEMLOCK
>> - DMA-map the scatterlist only when virtio_gpu_use_dma_api() is
>>    required; use DMA_TO_DEVICE for USE_READONLY blobs
>> - Sync userptr SG for the device on TRANSFER_TO_HOST
>> - Mark writable pages dirty when unpinning
>> - Keep pages pinned until RESOURCE_UNREF is queued; drop them from
>>    cleanup_object() on the unref response or on create failure
>> - Clear userptr->pages on pin failure to avoid double-free on cleanup
>> - Reject unaligned or overflowing userptr ranges at create time
>> - Disallow PRIME export of userptr objects
>> - Save CREATE_BLOB params and restore userptr resources after
>>    hibernation without using the shmem restore path
>>
>> Signed-off-by: Honglei Huang <honghuan@amd.com>
>> ---
>>   drivers/gpu/drm/virtio/Makefile          |   3 +-
>>   drivers/gpu/drm/virtio/virtgpu_drv.h     |  43 +++
>>   drivers/gpu/drm/virtio/virtgpu_object.c  |  22 ++
>>   drivers/gpu/drm/virtio/virtgpu_userptr.c | 365 +++++++++++++++++++++++
>>   drivers/gpu/drm/virtio/virtgpu_vq.c      |  33 +-
>>   5 files changed, 456 insertions(+), 10 deletions(-)
>>   create mode 100644 drivers/gpu/drm/virtio/virtgpu_userptr.c
>>
>> diff --git a/drivers/gpu/drm/virtio/Makefile b/drivers/gpu/drm/virtio/ 
>> Makefile
>> index d2e1788a82..fe7332a621 100644
>> --- a/drivers/gpu/drm/virtio/Makefile
>> +++ b/drivers/gpu/drm/virtio/Makefile
>> @@ -6,6 +6,7 @@
>>   virtio-gpu-y := virtgpu_drv.o virtgpu_kms.o virtgpu_gem.o 
>> virtgpu_vram.o \
>>       virtgpu_display.o virtgpu_vq.o \
>>       virtgpu_fence.o virtgpu_object.o virtgpu_debugfs.o 
>> virtgpu_plane.o \
>> -    virtgpu_ioctl.o virtgpu_prime.o virtgpu_trace_points.o 
>> virtgpu_submit.o
>> +    virtgpu_ioctl.o virtgpu_prime.o virtgpu_trace_points.o 
>> virtgpu_submit.o \
>> +    virtgpu_userptr.o
>>   obj-$(CONFIG_DRM_VIRTIO_GPU) += virtio-gpu.o
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/ 
>> virtio/virtgpu_drv.h
>> index 9df4c71173..e0941cc187 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
>> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
>> @@ -105,6 +105,7 @@ struct virtio_gpu_object_params {
>>       uint32_t blob_flags;
>>       uint64_t blob_id;
>>       uint32_t blob_hints;
>> +    uint64_t userptr;
>>   };
>>   struct virtio_gpu_object {
>> @@ -138,12 +139,42 @@ struct virtio_gpu_object_vram {
>>       struct drm_mm_node vram_node;
>>   };
>> +struct virtio_gpu_object_userptr;
>> +
>> +struct virtio_gpu_object_userptr_ops {
>> +    int (*get_pages)(struct virtio_gpu_object_userptr *userptr);
>> +    void (*put_pages)(struct virtio_gpu_object_userptr *userptr);
>> +};
>> +
>> +struct virtio_gpu_object_userptr {
>> +    struct virtio_gpu_object base;
>> +    const struct virtio_gpu_object_userptr_ops *ops;
>> +    /* Protects pages and sgt. */
>> +    struct mutex lock;
>> +
>> +    uint64_t start;
>> +    uint32_t npages;
>> +    uint32_t bo_handle;
>> +    uint32_t flags;
>> +
>> +    struct virtio_gpu_device *vgdev;
>> +    struct drm_file *file;
>> +    struct page **pages;
>> +    struct sg_table *sgt;
>> +    bool dma_mapped;
>> +    enum dma_data_direction dma_dir;
>> +    struct mm_struct *mm;
>> +};
>> +
>>   #define to_virtio_gpu_shmem(virtio_gpu_object) \
>>       container_of((virtio_gpu_object), struct 
>> virtio_gpu_object_shmem, base)
>>   #define to_virtio_gpu_vram(virtio_gpu_object) \
>>       container_of((virtio_gpu_object), struct virtio_gpu_object_vram, 
>> base)
>> +#define to_virtio_gpu_userptr(virtio_gpu_object) \
>> +    container_of((virtio_gpu_object), struct 
>> virtio_gpu_object_userptr, base)
>> +
>>   struct virtio_gpu_object_array {
>>       struct ww_acquire_ctx ticket;
>>       struct list_head next;
>> @@ -284,6 +315,7 @@ struct virtio_gpu_device {
>>       bool has_host_visible;
>>       bool has_context_init;
>>       bool has_blob_alignment;
>> +    bool has_blob_readonly;
>>       bool hibernated;
>>       struct virtio_shm_region host_visible_region;
>>       struct drm_mm host_visible_mm;
>> @@ -562,4 +594,15 @@ void virtio_gpu_vram_map_deferred(struct 
>> virtio_gpu_object_vram *vram);
>>   int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
>>                   struct drm_file *file);
>> +/* virtgpu_userptr.c */
>> +int virtio_gpu_userptr_create(struct virtio_gpu_device *vgdev,
>> +                  struct drm_file *file,
>> +                  struct virtio_gpu_object_params *params,
>> +                  struct virtio_gpu_object **bo_ptr);
>> +bool virtio_gpu_is_userptr(struct virtio_gpu_object *bo);
>> +void virtio_gpu_userptr_dma_sync_for_device(struct virtio_gpu_object 
>> *bo);
>> +int virtio_gpu_userptr_restore(struct virtio_gpu_device *vgdev,
>> +                   struct virtio_gpu_object *bo,
>> +                   struct virtio_gpu_mem_entry **ents,
>> +                   unsigned int *nents);
>>   #endif
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/ 
>> drm/virtio/virtgpu_object.c
>> index 49899485be..ab21494b1c 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_object.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_object.c
>> @@ -91,6 +91,16 @@ void virtio_gpu_cleanup_object(struct 
>> virtio_gpu_object *bo)
>>           drm_gem_free_mmap_offset(&vram->base.base.base);
>>           drm_gem_object_release(&vram->base.base.base);
>>           kfree(vram);
>> +    } else if (virtio_gpu_is_userptr(bo)) {
>> +        struct virtio_gpu_object_userptr *userptr =
>> +            to_virtio_gpu_userptr(bo);
>> +
>> +        mutex_lock(&userptr->lock);
>> +        userptr->ops->put_pages(userptr);
>> +        mutex_unlock(&userptr->lock);
>> +        mutex_destroy(&userptr->lock);
>> +        drm_gem_object_release(&userptr->base.base.base);
>> +        kfree(userptr);
>>       } else {
>>           drm_gem_object_release(&bo->base.base);
>>           kfree(bo);
>> @@ -316,6 +326,18 @@ int virtio_gpu_object_restore_all(struct 
>> virtio_gpu_device *vgdev)
>>               continue;
>>           }
>> +        if (virtio_gpu_is_userptr(bo)) {
>> +            ret = virtio_gpu_userptr_restore(vgdev, bo, &ents,
>> +                             &nents);
>> +            if (ret)
>> +                break;
>> +
>> +            virtio_gpu_cmd_resource_create_blob(vgdev, bo,
>> +                                &bo->params,
>> +                                ents, nents);
>> +            continue;
>> +        }
>> +
>>           if (bo->params.blob || bo->attached) {
>>               ret = virtio_gpu_object_shmem_init(vgdev, bo, &ents,
>>                                  &nents);
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_userptr.c b/drivers/gpu/ 
>> drm/virtio/virtgpu_userptr.c
>> new file mode 100644
>> index 0000000000..ccfd96844e
>> --- /dev/null
>> +++ b/drivers/gpu/drm/virtio/virtgpu_userptr.c
>> @@ -0,0 +1,365 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +#include <linux/dma-mapping.h>
>> +#include <linux/limits.h>
>> +#include <linux/mm.h>
>> +#include <linux/overflow.h>
>> +#include <linux/pid.h>
>> +#include <linux/sched/mm.h>
>> +#include <linux/sched/signal.h>
>> +#include <linux/vmalloc.h>
>> +
>> +#include "virtgpu_drv.h"
>> +#include <drm/drm_gem.h>
>> +
>> +static void virtio_gpu_userptr_free(struct drm_gem_object *obj)
>> +{
>> +    struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(obj);
>> +    struct virtio_gpu_device *vgdev = obj->dev->dev_private;
>> +
>> +    /*
>> +     * Keep pages pinned until RESOURCE_UNREF completes. The response
>> +     * callback calls virtio_gpu_cleanup_object(), which drops them.
>> +     */
>> +    if (bo->created) {
>> +        virtio_gpu_remove_from_restore_list(bo);
>> +        virtio_gpu_cmd_unref_resource(vgdev, bo, false);
>> +        virtio_gpu_notify(vgdev);
>> +        return;
>> +    }
>> +
>> +    virtio_gpu_cleanup_object(bo);
>> +}
>> +
>> +static struct dma_buf *
>> +virtio_gpu_userptr_prime_export(struct drm_gem_object *obj, int flags)
>> +{
>> +    return ERR_PTR(-EINVAL);
>> +}
>> +
>> +static const struct drm_gem_object_funcs virtio_gpu_userptr_funcs = {
>> +    .open = virtio_gpu_gem_object_open,
>> +    .close = virtio_gpu_gem_object_close,
>> +    .free = virtio_gpu_userptr_free,
>> +    .export = virtio_gpu_userptr_prime_export,
>> +};
>> +
>> +bool virtio_gpu_is_userptr(struct virtio_gpu_object *bo)
>> +{
>> +    return bo->base.base.funcs == &virtio_gpu_userptr_funcs;
>> +}
>> +
>> +void virtio_gpu_userptr_dma_sync_for_device(struct virtio_gpu_object 
>> *bo)
>> +{
>> +    struct virtio_gpu_object_userptr *userptr = 
>> to_virtio_gpu_userptr(bo);
>> +    struct device *dev;
>> +
>> +    if (!userptr->dma_mapped)
>> +        return;
>> +
>> +    dev = drm_dev_dma_dev(userptr->base.base.base.dev);
>> +    dma_sync_sgtable_for_device(dev, userptr->sgt, DMA_TO_DEVICE);
>> +}
>> +
>> +static int
>> +virtio_gpu_userptr_get_pages(struct virtio_gpu_object_userptr *userptr)
>> +{
>> +    unsigned int flag = FOLL_LONGTERM;
>> +    unsigned int num_pages, pinned = 0;
>> +    int ret = 0;
>> +
>> +    if (userptr->pages)
>> +        return 0;
>> +
>> +    userptr->pages = kvmalloc_array(userptr->npages, sizeof(struct 
>> page *),
>> +                    GFP_KERNEL);
>> +    if (!userptr->pages)
>> +        return -ENOMEM;
>> +
>> +    if (!(userptr->flags & VIRTGPU_BLOB_FLAG_USE_READONLY))
>> +        flag |= FOLL_WRITE;
>> +
>> +    do {
>> +        num_pages = userptr->npages - pinned;
>> +
>> +        ret = pin_user_pages_fast(userptr->start + pinned * PAGE_SIZE,
>> +                      num_pages, flag,
>> +                      userptr->pages + pinned);
>> +
>> +        if (ret < 0) {
>> +            if (pinned)
>> +                unpin_user_pages(userptr->pages, pinned);
>> +            kvfree(userptr->pages);
>> +            userptr->pages = NULL;
>> +            return ret;
>> +        }
>> +
>> +        pinned += ret;
>> +
>> +    } while (pinned < userptr->npages);
>> +
>> +    return 0;
>> +}
>> +
>> +static void
>> +virtio_gpu_userptr_unaccount(struct virtio_gpu_object_userptr *userptr)
>> +{
>> +    if (!userptr->mm)
>> +        return;
>> +
>> +    atomic64_sub(userptr->npages, &userptr->mm->pinned_vm);
>> +    mmdrop(userptr->mm);
>> +    userptr->mm = NULL;
>> +}
>> +
>> +static void
>> +virtio_gpu_userptr_put_pages(struct virtio_gpu_object_userptr *userptr)
>> +{
>> +    struct drm_device *dev = userptr->base.base.base.dev;
>> +
>> +    if (userptr->sgt) {
>> +        if (userptr->dma_mapped)
>> +            dma_unmap_sgtable(drm_dev_dma_dev(dev), userptr->sgt,
>> +                      userptr->dma_dir, 0);
>> +        userptr->dma_mapped = false;
>> +        sg_free_table(userptr->sgt);
>> +        kfree(userptr->sgt);
>> +        userptr->sgt = NULL;
>> +    }
>> +
>> +    if (userptr->pages) {
>> +        bool dirty = !(userptr->flags & VIRTGPU_BLOB_FLAG_USE_READONLY);
>> +
>> +        unpin_user_pages_dirty_lock(userptr->pages, userptr->npages,
>> +                        dirty);
>> +        kvfree(userptr->pages);
>> +        userptr->pages = NULL;
>> +    }
>> +
>> +    virtio_gpu_userptr_unaccount(userptr);
>> +}
>> +
>> +static int
>> +virtio_gpu_userptr_get_entries(struct virtio_gpu_device *vgdev,
>> +                   struct virtio_gpu_object_userptr *userptr,
>> +                   struct virtio_gpu_mem_entry **ents,
>> +                   unsigned int *nents)
>> +{
>> +    bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
>> +    struct scatterlist *sg;
>> +    unsigned int count;
>> +    int si;
>> +
>> +    count = use_dma_api ? userptr->sgt->nents : userptr->sgt- 
>> >orig_nents;
>> +    if (!count)
>> +        return -EINVAL;
>> +
>> +    *ents = kvmalloc_array(count, sizeof(**ents), GFP_KERNEL);
>> +    if (!*ents)
>> +        return -ENOMEM;
>> +
>> +    if (use_dma_api) {
>> +        for_each_sgtable_dma_sg(userptr->sgt, sg, si) {
>> +            (*ents)[si].addr = cpu_to_le64(sg_dma_address(sg));
>> +            (*ents)[si].length = cpu_to_le32(sg_dma_len(sg));
>> +            (*ents)[si].padding = 0;
>> +        }
>> +    } else {
>> +        for_each_sgtable_sg(userptr->sgt, sg, si) {
>> +            (*ents)[si].addr = cpu_to_le64(sg_phys(sg));
>> +            (*ents)[si].length = cpu_to_le32(sg->length);
>> +            (*ents)[si].padding = 0;
>> +        }
>> +    }
>> +
>> +    *nents = count;
>> +    return 0;
>> +}
>> +
>> +int virtio_gpu_userptr_restore(struct virtio_gpu_device *vgdev,
>> +                   struct virtio_gpu_object *bo,
>> +                   struct virtio_gpu_mem_entry **ents,
>> +                   unsigned int *nents)
>> +{
>> +    struct virtio_gpu_object_userptr *userptr = 
>> to_virtio_gpu_userptr(bo);
>> +    int ret;
>> +
>> +    mutex_lock(&userptr->lock);
>> +    if (!userptr->sgt || !userptr->pages) {
>> +        mutex_unlock(&userptr->lock);
>> +        return -EINVAL;
>> +    }
>> +
>> +    if (userptr->dma_mapped) {
>> +        struct device *dev = drm_dev_dma_dev(vgdev->ddev);
>> +
>> +        dma_unmap_sgtable(dev, userptr->sgt, userptr->dma_dir, 0);
>> +        userptr->dma_mapped = false;
>> +        ret = dma_map_sgtable(dev, userptr->sgt, userptr->dma_dir, 0);
> 
> This maps with attributes 0, allowing bounce buffers instead of
> "zero-copy memory access". It is also unclear what coherence guarantee 
> the UAPI is intended to provide.


This is a good point, will modify the commit and patch tittle to remove
ero-copy memory access.
And in virtio_gpu_object_shmem_init it also uses dma_map_sgtable(..., 
0), so keep 0 here.

Regards,
Honglei

> 
>> +        if (ret) {
>> +            mutex_unlock(&userptr->lock);
>> +            return ret;
>> +        }
>> +        userptr->dma_mapped = true;
>> +    }
>> +
>> +    ret = virtio_gpu_userptr_get_entries(vgdev, userptr, ents, nents);
>> +    mutex_unlock(&userptr->lock);
>> +    return ret;
>> +}
>> +
>> +static int
>> +virtio_gpu_userptr_init(struct drm_device *dev, struct drm_file *file,
>> +            struct virtio_gpu_object_userptr *userptr,
>> +            struct virtio_gpu_object_params *params,
>> +            const struct virtio_gpu_object_userptr_ops *ops)
>> +{
>> +    struct drm_gem_object *obj;
>> +    int ret;
>> +
>> +    userptr->start = params->userptr;
>> +    userptr->npages = params->size >> PAGE_SHIFT;
>> +    userptr->flags = params->blob_flags;
>> +
>> +    mutex_init(&userptr->lock);
>> +    userptr->vgdev = dev->dev_private;
>> +    userptr->file = file;
>> +    userptr->ops = ops;
>> +
>> +    /*
>> +     * Allocate the resource id before GEM init so a failure here can
>> +     * unwind with a plain kfree and does not need a special id=0 guard
>> +     * in the shared resource_id_put helper.
>> +     */
>> +    ret = virtio_gpu_resource_id_get(userptr->vgdev,
>> +                     &userptr->base.hw_res_handle);
>> +    if (ret) {
>> +        mutex_destroy(&userptr->lock);
>> +        return ret;
>> +    }
>> +
>> +    obj = &userptr->base.base.base;
>> +    obj->funcs = &virtio_gpu_userptr_funcs;
>> +
>> +    drm_gem_private_object_init(dev, obj, params->size);
>> +    INIT_LIST_HEAD(&userptr->base.restore_node);
>> +
>> +    return 0;
>> +}
>> +
>> +static const struct virtio_gpu_object_userptr_ops 
>> virtio_gpu_userptr_ops = {
>> +    .get_pages = virtio_gpu_userptr_get_pages,
>> +    .put_pages = virtio_gpu_userptr_put_pages,
>> +};
>> +
>> +int virtio_gpu_userptr_create(struct virtio_gpu_device *vgdev,
>> +                  struct drm_file *file,
>> +                  struct virtio_gpu_object_params *params,
>> +                  struct virtio_gpu_object **bo_ptr)
>> +{
>> +    struct virtio_gpu_object_userptr *userptr;
>> +    struct virtio_gpu_mem_entry *ents = NULL;
>> +    struct sg_table *sgt;
>> +    struct mm_struct *mm;
>> +    unsigned long lock_limit;
>> +    unsigned long start;
>> +    unsigned long end;
>> +    s64 new_pinned;
>> +    unsigned int nents;
>> +    int ret;
>> +
>> +    *bo_ptr = NULL;
>> +
>> +    if (!params->size || !IS_ALIGNED(params->size, PAGE_SIZE) ||
>> +        params->userptr != (unsigned long)params->userptr)
>> +        return -EINVAL;
>> +
>> +    start = params->userptr;
>> +    if (!IS_ALIGNED(start, PAGE_SIZE) ||
>> +        check_add_overflow(start, (unsigned long)params->size, &end))
>> +        return -EINVAL;
>> +
>> +    if (!can_do_mlock())
>> +        return -EPERM;
>> +
>> +    if (params->size >> PAGE_SHIFT > INT_MAX)
>> +        return -E2BIG;
>> +
>> +    if (!access_ok((void __user *)start, params->size))
>> +        return -EFAULT;
>> +
>> +    userptr = kzalloc_obj(*userptr);
>> +    if (!userptr)
>> +        return -ENOMEM;
>> +
>> +    ret = virtio_gpu_userptr_init(vgdev->ddev, file, userptr, params,
>> +                      &virtio_gpu_userptr_ops);
>> +    if (ret) {
>> +        kfree(userptr);
>> +        return ret;
>> +    }
>> +
>> +    mm = current->mm;
>> +    mmgrab(mm);
>> +    lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>> +    new_pinned = atomic64_add_return(userptr->npages, &mm->pinned_vm);
>> +    if (new_pinned < 0 ||
>> +        (new_pinned > lock_limit && !capable(CAP_IPC_LOCK))) {
>> +        atomic64_sub(userptr->npages, &mm->pinned_vm);
>> +        mmdrop(mm);
>> +        ret = new_pinned < 0 ? -EOVERFLOW : -ENOMEM;
>> +        goto err_cleanup;
>> +    }
>> +    userptr->mm = mm;
>> +
>> +    mutex_lock(&userptr->lock);
>> +    ret = userptr->ops->get_pages(userptr);
>> +    mutex_unlock(&userptr->lock);
>> +    if (ret)
>> +        goto err_cleanup;
>> +
>> +    sgt = drm_prime_pages_to_sg(vgdev->ddev, userptr->pages,
>> +                    userptr->npages);
>> +    if (IS_ERR(sgt)) {
>> +        ret = PTR_ERR(sgt);
>> +        goto err_cleanup;
>> +    }
>> +
>> +    userptr->sgt = sgt;
>> +
>> +    /*
>> +     * Match shmem blobs: only DMA-map when the virtio DMA API is in
>> +     * use. Mapping unconditionally can create SWIOTLB bounce buffers
>> +     * that get copied back over guest pages on unmap even though the
>> +     * host was given sg_phys() addresses.
>> +     */
>> +    if (virtio_gpu_use_dma_api(vgdev->vdev)) {
>> +        enum dma_data_direction dir =
>> +            (userptr->flags & VIRTGPU_BLOB_FLAG_USE_READONLY) ?
>> +            DMA_TO_DEVICE : DMA_BIDIRECTIONAL;
>> +
>> +        ret = dma_map_sgtable(drm_dev_dma_dev(vgdev->ddev), sgt,
>> +                      dir, 0);
>> +        if (ret)
>> +            goto err_cleanup;
>> +
>> +        userptr->dma_dir = dir;
>> +        userptr->dma_mapped = true;
>> +    }
>> +
>> +    ret = virtio_gpu_userptr_get_entries(vgdev, userptr, &ents, &nents);
>> +    if (ret)
>> +        goto err_cleanup;
>> +
>> +    virtio_gpu_cmd_resource_create_blob(vgdev, &userptr->base, 
>> params, ents,
>> +                        nents);
>> +
>> +    userptr->base.params = *params;
>> +    virtio_gpu_add_object_to_restore_list(vgdev, &userptr->base);
>> +
>> +    *bo_ptr = &userptr->base;
>> +    return 0;
>> +
>> +err_cleanup:
>> +    virtio_gpu_cleanup_object(&userptr->base);
>> +    return ret;
>> +}
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/ 
>> virtio/virtgpu_vq.c
>> index c02c03c10d..dcbd7bb7a6 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_vq.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
>> @@ -781,9 +781,14 @@ int 
>> virtio_gpu_panic_cmd_transfer_to_host_2d(struct virtio_gpu_device *vgdev,
>>       struct virtio_gpu_vbuffer *vbuf;
>>       bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
>> -    if (virtio_gpu_is_shmem(bo) && use_dma_api)
>> -        dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
>> -                        bo->base.sgt, DMA_TO_DEVICE);
>> +    if (use_dma_api) {
>> +        if (virtio_gpu_is_shmem(bo))
>> +            dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
>> +                            bo->base.sgt,
>> +                            DMA_TO_DEVICE);
>> +        else if (virtio_gpu_is_userptr(bo))
>> +            virtio_gpu_userptr_dma_sync_for_device(bo);
>> +    }
>>       cmd_p = virtio_gpu_panic_alloc_cmd_resp(vgdev, &vbuf, 
>> sizeof(*cmd_p));
>>       memset(cmd_p, 0, sizeof(*cmd_p));
>> @@ -812,9 +817,14 @@ void virtio_gpu_cmd_transfer_to_host_2d(struct 
>> virtio_gpu_device *vgdev,
>>       struct virtio_gpu_vbuffer *vbuf;
>>       bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
>> -    if (virtio_gpu_is_shmem(bo) && use_dma_api)
>> -        dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
>> -                        bo->base.sgt, DMA_TO_DEVICE);
>> +    if (use_dma_api) {
>> +        if (virtio_gpu_is_shmem(bo))
>> +            dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
>> +                            bo->base.sgt,
>> +                            DMA_TO_DEVICE);
>> +        else if (virtio_gpu_is_userptr(bo))
>> +            virtio_gpu_userptr_dma_sync_for_device(bo);
>> +    }
>>       cmd_p = virtio_gpu_alloc_cmd(vgdev, &vbuf, sizeof(*cmd_p));
>>       memset(cmd_p, 0, sizeof(*cmd_p));
>> @@ -1245,9 +1255,14 @@ void virtio_gpu_cmd_transfer_to_host_3d(struct 
>> virtio_gpu_device *vgdev,
>>       struct virtio_gpu_vbuffer *vbuf;
>>       bool use_dma_api = virtio_gpu_use_dma_api(vgdev->vdev);
>> -    if (virtio_gpu_is_shmem(bo) && use_dma_api)
>> -        dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
>> -                        bo->base.sgt, DMA_TO_DEVICE);
>> +    if (use_dma_api) {
>> +        if (virtio_gpu_is_shmem(bo))
>> +            dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
>> +                            bo->base.sgt,
>> +                            DMA_TO_DEVICE);
>> +        else if (virtio_gpu_is_userptr(bo))
>> +            virtio_gpu_userptr_dma_sync_for_device(bo);
> 
> This code is ineffective since the transfer ioctl rejects 
> VIRTGPU_BLOB_MEM_GUEST.
> 
> Regards,
> Akihiko Odaki

Re: [PATCH v8 4/4] drm/virtio: wire blob ioctl creation to userptr objects

[Huang, Honglei]

On 9/19/2026 10:28 PM, Akihiko Odaki wrote:
> On 2026/09/18 18:59, Honglei Huang wrote:
>> Integrate userptr into the blob resource creation ioctl.
>>
>> - A non-zero userptr selects virtio_gpu_userptr_create()
>> - Reject userptr unless blob_mem is VIRTGPU_BLOB_MEM_GUEST
>> - Reject VIRTGPU_BLOB_FLAG_USE_READONLY unless the device
>>    advertised VIRTIO_GPU_F_BLOB_READONLY
>> - Advertise VIRTGPU_PARAM_USERPTR and VIRTGPU_PARAM_BLOB_READONLY
>>
>> Signed-off-by: Honglei Huang <honghuan@amd.com>
>> ---
>>   drivers/gpu/drm/virtio/virtgpu_debugfs.c |  1 +
>>   drivers/gpu/drm/virtio/virtgpu_ioctl.c   | 35 ++++++++++++++++++++----
>>   drivers/gpu/drm/virtio/virtgpu_kms.c     |  8 ++++--
>>   3 files changed, 37 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_debugfs.c b/drivers/gpu/ 
>> drm/virtio/virtgpu_debugfs.c
>> index 3a68a16b58..b8b9b40584 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_debugfs.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_debugfs.c
>> @@ -55,6 +55,7 @@ static int virtio_gpu_features(struct seq_file *m, 
>> void *data)
>>                   vgdev->has_resource_assign_uuid);
>>       virtio_gpu_add_bool(m, "blob resources", vgdev->has_resource_blob);
>> +    virtio_gpu_add_bool(m, "blob readonly", vgdev->has_blob_readonly);
>>       virtio_gpu_add_bool(m, "context init", vgdev->has_context_init);
>>       virtio_gpu_add_int(m, "cap sets", vgdev->num_capsets);
>>       virtio_gpu_add_int(m, "scanouts", vgdev->num_scanouts);
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/ 
>> virtio/virtgpu_ioctl.c
>> index 3d8e4ccdb7..3dc058e50e 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
>> @@ -36,7 +36,10 @@
>>   #define VIRTGPU_BLOB_FLAG_USE_MASK (VIRTGPU_BLOB_FLAG_USE_MAPPABLE | \
>>                       VIRTGPU_BLOB_FLAG_USE_SHAREABLE | \
>> -                    VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE)
>> +                    VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE | \
>> +                    VIRTGPU_BLOB_FLAG_USE_READONLY)
>> +
>> +#define VIRTGPU_BLOB_HINT_MASK DRM_VIRTGPU_BLOB_FLAG_HINT_DEFER_MAPPING
>>   /* Must be called with &virtio_gpu_fpriv.struct_mutex held. */
>>   static void virtio_gpu_create_context_locked(struct 
>> virtio_gpu_device *vgdev,
>> @@ -122,6 +125,12 @@ static int virtio_gpu_getparam_ioctl(struct 
>> drm_device *dev, void *data,
>>               return -ENOENT;
>>           value = vgdev->blob_alignment;
>>           break;
>> +    case VIRTGPU_PARAM_USERPTR:
>> +        value = 1;
>> +        break;
>> +    case VIRTGPU_PARAM_BLOB_READONLY:
>> +        value = vgdev->has_blob_readonly ? 1 : 0;
>> +        break;
>>       default:
>>           return -EINVAL;
>>       }
>> @@ -453,11 +462,23 @@ static int verify_blob(struct virtio_gpu_device 
>> *vgdev,
>>       if (rc_blob->blob_flags & ~VIRTGPU_BLOB_FLAG_USE_MASK)
>>           return -EINVAL;
>> +    if (rc_blob->blob_hints & ~VIRTGPU_BLOB_HINT_MASK)
>> +        return -EINVAL;
>> +
>>       if (rc_blob->blob_flags & VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE) {
>>           if (!vgdev->has_resource_assign_uuid)
>>               return -EINVAL;
>>       }
>> +    if (rc_blob->blob_flags & VIRTGPU_BLOB_FLAG_USE_READONLY) {
>> +        if (!vgdev->has_blob_readonly)
>> +            return -EINVAL;
>> +    }
>> +
>> +    if (rc_blob->userptr &&
>> +        rc_blob->blob_mem != VIRTGPU_BLOB_MEM_GUEST)
>> +        return -EINVAL;
>> +
>>       switch (rc_blob->blob_mem) {
>>       case VIRTGPU_BLOB_MEM_GUEST:
>>           *guest_blob = true;
>> @@ -495,6 +516,7 @@ static int verify_blob(struct virtio_gpu_device 
>> *vgdev,
>>       params->blob = true;
>>       params->blob_flags = rc_blob->blob_flags;
>>       params->blob_hints = rc_blob->blob_hints;
>> +    params->userptr = rc_blob->userptr;
>>       if (vgdev->has_blob_alignment &&
>>           !IS_ALIGNED(params->size, vgdev->blob_alignment))
>> @@ -518,9 +540,10 @@ static int 
>> virtio_gpu_resource_create_blob_ioctl(struct drm_device *dev,
>>       struct virtio_gpu_fpriv *vfpriv = file->driver_priv;
>>       struct drm_virtgpu_resource_create_blob *rc_blob = data;
>> -    if (verify_blob(vgdev, vfpriv, &params, rc_blob,
>> -            &guest_blob, &host3d_blob))
>> -        return -EINVAL;
>> +    ret = verify_blob(vgdev, vfpriv, &params, rc_blob,
>> +              &guest_blob, &host3d_blob);
>> +    if (ret)
>> +        return ret;
>>       if (vgdev->has_virgl_3d)
>>           virtio_gpu_create_context(dev, file);
>> @@ -538,7 +561,9 @@ static int 
>> virtio_gpu_resource_create_blob_ioctl(struct drm_device *dev,
>>                         vfpriv->ctx_id, NULL, NULL);
>>       }
>> -    if (guest_blob)
>> +    if (guest_blob && params.userptr)
>> +        ret = virtio_gpu_userptr_create(vgdev, file, &params, &bo);
>> +    else if (guest_blob)
>>           ret = virtio_gpu_object_create(vgdev, &params, &bo, NULL);
>>       else if (!guest_blob && host3d_blob)
>>           ret = virtio_gpu_vram_create(vgdev, &params, &bo);
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/ 
>> virtio/virtgpu_kms.c
>> index 1d4d3bf46a..06c2bded49 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_kms.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
>> @@ -249,15 +249,19 @@ int virtio_gpu_init(struct virtio_device *vdev, 
>> struct drm_device *dev)
>>           vgdev->blob_alignment = blob_alignment;
>>       }
>> +    if (virtio_has_feature(vgdev->vdev, VIRTIO_GPU_F_BLOB_READONLY))
> 
> This hits BUG(). It queries queries VIRTIO_GPU_F_BLOB_READONLY, but the 
> feature is absent from the driver’s features[]. virtio_has_feature() 
> validates device-specific queries through 
> virtio_check_driver_offered_feature(), which executes BUG() for an 
> unregistered feature. This affects ordinary probe regardless of host 
> support.
> 
> Please add the feature to the array and ensure that the patch is 
> properly tested before submission.

Really thanks for the point out, we did test in previous version patch,
but for passing AI review I have to added the VIRTIO_GPU_F_BLOB_READONLY 
before send out, the AI review are so many, to address it I made many 
changes, resulted in this issue being overlooked. And I have tested the 
V9, the guest boot is OK, basic function is ok.

And due to the changing for virtio gpu, many other components need to be 
changed, need some times to give qemu/virglrender... code. We have a
lot of parallel tasks here. But I will keep changing code until you are 
satisfied.

Regards,
Honglei


> 
> Regards,
> Akihiko Odaki
> 
>> +        vgdev->has_blob_readonly = true;
>> +
>>       DRM_INFO("features: %cvirgl %cedid %cresource_blob %chost_visible",
>>            vgdev->has_virgl_3d    ? '+' : '-',
>>            vgdev->has_edid        ? '+' : '-',
>>            vgdev->has_resource_blob ? '+' : '-',
>>            vgdev->has_host_visible ? '+' : '-');
>> -    DRM_INFO("features: %ccontext_init %cblob_alignment\n",
>> +    DRM_INFO("features: %ccontext_init %cblob_alignment 
>> %cblob_readonly\n",
>>            vgdev->has_context_init ? '+' : '-',
>> -         vgdev->has_blob_alignment ? '+' : '-');
>> +         vgdev->has_blob_alignment ? '+' : '-',
>> +         vgdev->has_blob_readonly ? '+' : '-');
>>       ret = virtio_gpu_find_vqs(vgdev);
>>       if (ret) {
>