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virtio-gpu api: blob resources

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A blob resource is a container for:
   - VIRTIO_GPU_BLOB_MEM_GUEST: a guest memory allocation
     (referred to as a "guest-only blob resource")

   - VIRTIO_GPU_BLOB_MEM_HOST3D: a host3d memory allocation
     (referred to as a "host-only blob resource")

   - VIRTIO_GPU_BLOB_MEM_HOST3D_GUEST: a guest + host3d memory allocation
     (referred to as a "default blob resource").

The memory properties of the blob resource must be described by
`blob_mem`.

For default and guest only blob resources set, `nents` guest system
pages are assigned to the resource.  For default blob resources,
these guest pages are used for transfer operations. Attach/detach is
also possible to allow swap-in/swap-out, but isn't required since it
may not be applicable to future blob mem types
(shared guest/guest vram).

Host allocations depend on whether the 3D is supported. If 3D is not
supported, the only valid field for `blob_mem` is
VIRTIO_GPU_BLOB_MEM_GUEST.

If 3D is supported, the virtio-gpu resource is created from the
context local object identified by the `blob_id`. The actual host
allocation done by the CMD_SUBMIT_3D.

Userspace must specify if the blob resource is intended to be used
for userspace mapping, sharing between virtio-gpu contexts and/or
sharing between virtio devices. This is done via `blob_flags`.

For 3D hosts, both VIRTIO_GPU_CMD_TRANSFER_TO_HOST_3D and
VIRTIO_GPU_CMD_TRANSFER_FROM_HOST_3D may be used to update
the host resource. There is no restriction on the image/buffer
view the guest/host userspace has on the blob resource.

VIRTIO_GPU_CMD_SET_SCANOUT_BLOB / VIRTIO_GPU_CMD_RESOURCE_FLUSH may
be used with blob resources as well.  The modifier is intentionally
left out of SCANOUT_BLOB, and auxilary blobs are also left out
as a simplification.

The use case for blob resources is zero-copy, needed for coherent
memory in virglrenderer. Host only blob resources are not mappable
without the feature described in the next patch, but are shareable.

Future work:
   - Emulated coherent `blob_mem` type for QEMU/vhost-user
   - A `blob_mem` type for guest-only resources imported in
     cache-coherent FOSS GPU/display drivers.
   - Display integration involving the blob model using seamless
     Wayland windows.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Acked-by: Chia-I Wu <olvaffe@gmail.com>
Acked-by: Lingfeng Yang <lfy@google.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200924003214.662-3-gurchetansingh@chromium.org
Co-developed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
This commit is contained in:
Gerd Hoffmann 2020-09-23 17:31:58 -07:00
parent 0ce0729656
commit ff886cbdcc
1 changed files with 43 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
include/uapi/linux/virtio_gpu.h
View File

@ -55,6 +55,11 @@
*/
#define VIRTIO_GPU_F_RESOURCE_UUID 2
/*
* VIRTIO_GPU_CMD_RESOURCE_CREATE_BLOB
*/
#define VIRTIO_GPU_F_RESOURCE_BLOB 3
enum virtio_gpu_ctrl_type {
VIRTIO_GPU_UNDEFINED = 0,
@ -71,6 +76,8 @@ enum virtio_gpu_ctrl_type {
VIRTIO_GPU_CMD_GET_CAPSET,
VIRTIO_GPU_CMD_GET_EDID,
VIRTIO_GPU_CMD_RESOURCE_ASSIGN_UUID,
VIRTIO_GPU_CMD_RESOURCE_CREATE_BLOB,
VIRTIO_GPU_CMD_SET_SCANOUT_BLOB,
/* 3d commands */
VIRTIO_GPU_CMD_CTX_CREATE = 0x0200,
@ -359,4 +366,40 @@ struct virtio_gpu_resp_resource_uuid {
__u8 uuid[16];
};
/* VIRTIO_GPU_CMD_RESOURCE_CREATE_BLOB */
struct virtio_gpu_resource_create_blob {
struct virtio_gpu_ctrl_hdr hdr;
__le32 resource_id;
#define VIRTIO_GPU_BLOB_MEM_GUEST 0x0001
#define VIRTIO_GPU_BLOB_MEM_HOST3D 0x0002
#define VIRTIO_GPU_BLOB_MEM_HOST3D_GUEST 0x0003
#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
/* zero is invalid blob mem */
__le32 blob_mem;
__le32 blob_flags;
__le64 blob_id;
__le64 size;
__le32 nr_entries;
/*
* sizeof(nr_entries * virtio_gpu_mem_entry) bytes follow
*/
};
/* VIRTIO_GPU_CMD_SET_SCANOUT_BLOB */
struct virtio_gpu_set_scanout_blob {
struct virtio_gpu_ctrl_hdr hdr;
struct virtio_gpu_rect r;
__le32 scanout_id;
__le32 resource_id;
__le32 width;
__le32 height;
__le32 format;
__le32 padding;
__le32 strides[4];
__le32 offsets[4];
};
#endif