[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@xxxxxxx>
---
 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