[PATCH v3 03/19] virtio-gpu api: blob resources

[Gurchetan Singh]

From: Gerd Hoffmann <kraxel at redhat.com>

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 at redhat.com>
Co-developed-by: Gurchetan Singh <gurchetansingh at chromium.org>
Signed-off-by: Gurchetan Singh <gurchetansingh at chromium.org>
Acked-by: Tomeu Vizoso <tomeu.vizoso at collabora.com>
Acked-by: Chia-I Wu <olvaffe at gmail.com>
Acked-by: Lingfeng Yang <lfy at google.com>
Link: https://gitlab.freedesktop.org/virgl/virglrenderer/-/merge_requests/374
---
 include/uapi/linux/virtio_gpu.h | 43 +++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/include/uapi/linux/virtio_gpu.h b/include/uapi/linux/virtio_gpu.h
index 747a5c5cc4e60..4ddf2fe342ed0 100644
--- a/include/uapi/linux/virtio_gpu.h
+++ b/include/uapi/linux/virtio_gpu.h
@@ -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
-- 
2.26.2