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| -rw-r--r-- | virtio-gpu.tex | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/virtio-gpu.tex b/virtio-gpu.tex index ccae624..631aaf2 100644 --- a/virtio-gpu.tex +++ b/virtio-gpu.tex @@ -35,6 +35,7 @@ control queue. \begin{description} \item[VIRTIO_GPU_F_VIRGL (0)] virgl 3D mode is supported. \item[VIRTIO_GPU_F_EDID (1)] EDID is supported. +\item[VIRTIO_GPU_F_RESOURCE_SHARED 2)] shared resources are supported. \end{description} \subsection{Device configuration layout}\label{sec:Device Types / GPU Device / Device configuration layout} @@ -103,6 +104,8 @@ work. This is like a GART in a real GPU. \begin{itemize*} \item Create a host resource using VIRTIO_GPU_CMD_RESOURCE_CREATE_2D. + In case VIRTIO_GPU_F_RESOURCE_SHARED is negotiated the driver can + also use VIRTIO_GPU_CMD_RESOURCE_CREATE_2D_SHARED. \item Allocate a framebuffer from guest ram, and attach it as backing storage to the resource just created, using VIRTIO_GPU_CMD_RESOURCE_ATTACH_BACKING. Scatter lists are @@ -166,6 +169,28 @@ Then VIRTIO_GPU_CMD_UPDATE_CURSOR can be sent to the cursorq to set the pointer shape and position. To move the pointer without updating the shape use VIRTIO_GPU_CMD_MOVE_CURSOR instead. +\subsubsection{Device Operation: Shared resources} + +In case VIRTIO_GPU_F_RESOURCE_SHARED is negotiated the driver can use +the VIRTIO_GPU_CMD_RESOURCE_CREATE_2D_SHARED command to create shared +resources. Normal resources have both a guest buffer and host buffer +for the resource and the VIRTIO_GPU_CMD_TRANSFER_* commands are used +to transfer data between host and guest. Shared (guest allocated) +buffers CAN be used directly by the host, to remove or reduce the data +copies needed. + +The driver MUST attach backing storage to a shared resource before +using it. Any changes on the shared resource MAY be instantly visible +on the host. + +Otherwise the shared resources are used like normal resources. +Especially the driver must send explicit VIRTIO_GPU_CMD_TRANSFER_* +commands to the device for both normal and shared resources. Reason: +The device might have to flush caches. The device MAY also choose to +not create mapping for the shared resource. Especially for small +resources it might be more efficient to just copy the data instead of +establishing a shared mapping. + \subsubsection{Device Operation: Request header}\label{sec:Device Types / GPU Device / Device Operation / Device Operation: Request header} All requests and responses on the virt queues have a fixed header @@ -186,6 +211,7 @@ enum virtio_gpu_ctrl_type { VIRTIO_GPU_CMD_GET_CAPSET_INFO, VIRTIO_GPU_CMD_GET_CAPSET, VIRTIO_GPU_CMD_GET_EDID, + VIRTIO_GPU_CMD_RESOURCE_CREATE_2D_SHARED, /* 3d commands (OpenGL) */ VIRTIO_GPU_CMD_CTX_CREATE = 0x0200, @@ -215,6 +241,7 @@ enum virtio_gpu_ctrl_type { VIRTIO_GPU_RESP_ERR_INVALID_RESOURCE_ID, VIRTIO_GPU_RESP_ERR_INVALID_CONTEXT_ID, VIRTIO_GPU_RESP_ERR_INVALID_PARAMETER, + VIRTIO_GPU_RESP_ERR_NO_BACKING_STORAGE, }; #define VIRTIO_GPU_FLAG_FENCE (1 << 0) |