This defines a virtgpu shared memory region, with the possibilty
of more in the future. This is required to implement VK/GL coherent
memory semantics, among other things.
Signed-off-by: Gurchetan Singh <>
---
virtio-gpu.tex | 71 +++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 67 insertions(+), 4 deletions(-)
diff --git a/virtio-gpu.tex b/virtio-gpu.tex
index 97f7865..8f0c63c 100644
--- a/virtio-gpu.tex
+++ b/virtio-gpu.tex
@@ -88,13 +88,31 @@ \subsubsection{Events}
information is available or all displays are disabled the driver MAY
choose to use a fallback, such as 1024x768 at display 0.
+The driver SHOULD query all shared memory regions supported by the device.
+If the device supports shared memory, the \field{shmid} of a region MUST
+(see \ref{sec:Basic Facilities of a Virtio Device /
+Shared Memory Regions}~\nameref{sec:Basic Facilities of a Virtio Device /
+Shared Memory Regions}) be one of the following:
+
+\begin{lstlisting}
+enum virtio_gpu_shm_id {
+ VIRTIO_GPU_SHM_ID_UNDEFINED = 0,
+ VIRTIO_GPU_SHM_ID_HOST_VISIBLE = 1,
+};
+\end{lstlisting}
+
+The shared memory region with VIRTIO_GPU_SHM_ID_HOST_VISIBLE is referred as
+the "host visible memory region". The device MUST support the
+VIRTIO_GPU_CMD_RESOURCE_MAP_BLOB and VIRTIO_GPU_CMD_RESOURCE_UNMAP_BLOB
+if the host visible memory region is available.
+
\subsection{Device Operation}\label{sec:Device Types / GPU Device / Device Operation}
The virtio-gpu is based around the concept of resources private to the
-host, the guest must DMA transfer into these resources. This is a
-design requirement in order to interface with future 3D rendering. In
-the unaccelerated 2D mode there is no support for DMA transfers from
-resources, just to them.
+host. The guest must DMA transfer into these resources, unless shared memory
+regions are supported. This is a design requirement in order to interface with
+future 3D rendering. In the unaccelerated 2D mode there is no support for DMA
+transfers from resources, just to them.
Resources are initially simple 2D resources, consisting of a width,
height and format along with an identifier. The guest must then attach
@@ -201,6 +219,8 @@ \subsubsection{Device Operation: Request header}\label{sec:Device Types / GPU De
VIRTIO_GPU_CMD_TRANSFER_TO_HOST_3D,
VIRTIO_GPU_CMD_TRANSFER_FROM_HOST_3D,
VIRTIO_GPU_CMD_SUBMIT_3D,
+ VIRTIO_GPU_CMD_RESOURCE_MAP_BLOB,
+ VIRTIO_GPU_CMD_RESOURCE_UNMAP_BLOB,
/* cursor commands */
VIRTIO_GPU_CMD_UPDATE_CURSOR = 0x0300,
@@ -213,6 +233,7 @@ \subsubsection{Device Operation: Request header}\label{sec:Device Types / GPU De
VIRTIO_GPU_RESP_OK_CAPSET,
VIRTIO_GPU_RESP_OK_EDID,
VIRTIO_GPU_RESP_OK_RESOURCE_UUID,
+ VIRTIO_GPU_RESP_OK_MAP_INFO,
/* error responses */
VIRTIO_GPU_RESP_ERR_UNSPEC = 0x1200,
@@ -618,6 +639,48 @@ \subsubsection{Device Operation: controlq (3d)}\label{sec:Device Types / GPU Dev
\item[VIRTIO_GPU_CMD_SUBMIT_3D]
Submit rendering commands (mesa gallium command stream).
+\item[VIRTIO_GPU_CMD_RESOURCE_MAP_BLOB] maps a host-only
+ blob resource into an offset in the host visible memory region. Request
+ data is \field{struct virtio_gpu_resource_map_blob}. Response type
+ is VIRTIO_GPU_RESP_OK_MAP_INFO. Support is optional and negotiated
+ using the VIRTIO_GPU_F_RESOURCE_BLOB feature flag and checking for
+ the presence of the host visible memory region.
+
+\begin{lstlisting}
+struct virtio_gpu_resource_map_blob {
+ struct virtio_gpu_ctrl_hdr hdr;
+ le32 resource_id;
+ le32 padding;
+ le64 offset;
+};
+
+#define VIRTIO_GPU_MAP_CACHE_MASK 0x0f
+#define VIRTIO_GPU_MAP_CACHE_NONE 0x00
+#define VIRTIO_GPU_MAP_CACHE_CACHED 0x01
+#define VIRTIO_GPU_MAP_CACHE_UNCACHED 0x02
+#define VIRTIO_GPU_MAP_CACHE_WC 0x03
+struct virtio_gpu_resp_map_info {
+ struct virtio_gpu_ctrl_hdr hdr;
+ u32 map_info;
+ u32 padding;
+};
+\end{lstlisting}
+
+\item[VIRTIO_GPU_CMD_RESOURCE_UNMAP_BLOB] unmaps a
+ host-only blob resource from the host visible memory region. Request data
+ is \field{struct virtio_gpu_resource_unmap_blob}. Response type is
+ VIRTIO_GPU_RESP_OK_NODATA. Support is optional and negotiated
+ using the VIRTIO_GPU_F_RESOURCE_BLOB feature flag and checking for
+ the presence of the host visible memory region.
+
+\begin{lstlisting}
+struct virtio_gpu_resource_unmap_blob {
+ struct virtio_gpu_ctrl_hdr hdr;
+ le32 resource_id;
+ le32 padding;
+};
+\end{lstlisting}
+
\end{description}
\subsubsection{Device Operation: cursorq}\label{sec:Device Types / GPU Device / Device Operation / Device Operation: cursorq}
--
2.26.2.761.g0e0b3e54be-goog
