[PATCH 1/2] virtio-gpu: add resource create blob

Blob resources are size-based containers for host, guest, or
host+guest allocations.  These resources are designed with
mulit-process 3D support in mind, but also usable in virtio-gpu 2d
with system memory allocation (also known as dumb allocation, but
since that's reserved in a DRM/KMS world, went with system).

Many hypercalls are reused, since a image view into the blob resource
is possible.

Blob resources are both forward and backward looking.

Co-authored-by: Gerd Hoffman <>
Co-authored-by: Chia-I-Wu <>
Signed-off-by: Gurchetan Singh <>
---
 virtio-gpu.tex | 101 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)

diff --git a/virtio-gpu.tex b/virtio-gpu.tex
index e70532f..6f374bd 100644
--- a/virtio-gpu.tex
+++ b/virtio-gpu.tex
@@ -36,6 +36,7 @@ \subsection{Feature bits}\label{sec:Device Types / GPU Device / Feature bits}
 \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_UUID (2)] assigning resources UUIDs for export to other virtio devices is supported.
+\item[VIRTIO_GPU_F_RESOURCE_BLOB (3)] creating size-based blob resources is supported.
 \end{description}
 
 \subsection{Device configuration layout}\label{sec:Device Types / GPU Device / Device configuration layout}
@@ -188,6 +189,7 @@ \subsubsection{Device Operation: Request header}\label{sec:Device Types / GPU De
         VIRTIO_GPU_CMD_GET_CAPSET,
         VIRTIO_GPU_CMD_GET_EDID,
         VIRTIO_GPU_CMD_RESOURCE_ASSIGN_UUID,
+        VIRTIO_GPU_CMD_RESOURCE_CREATE_BLOB,
 
         /* 3d commands (OpenGL) */
         VIRTIO_GPU_CMD_CTX_CREATE = 0x0200,
@@ -498,6 +500,105 @@ \subsubsection{Device Operation: controlq}\label{sec:Device Types / GPU Device /
 other devices are not visible in the attached backing until they are transferred
 into the backing.
 
+\item[VIRTIO_GPU_CMD_RESOURCE_CREATE_BLOB] Creates a virtio-gpu blob
+  resource. Request data is \field{struct
+  virtio_gpu_resource_create_blob}, followed by \field{struct
+  virtio_gpu_mem_entry} entries. Response type is
+  VIRTIO_GPU_RESP_OK_NODATA. Support is optional and negotiated
+  using the VIRTIO_GPU_F_RESOURCE_BLOB feature flag.
+
+\begin{lstlisting}
+#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_MEM_HOSTSYS           0x0004
+#define VIRTIO_GPU_BLOB_MEM_HOSTSYS_GUEST     0x0005
+
+#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
+
+struct virtio_gpu_resource_create_blob {
+       struct virtio_gpu_ctrl_hdr hdr;
+       le32 resource_id;
+       le32 blob_mem;
+       le32 blob_flags;
+       le32 nr_entries;
+       le64 blob_id;
+       le64 size;
+};
+
+\end{lstlisting}
+
+A blob resource is a container for:
+
+  \begin{itemize*}
+  \item a guest memory allocation (referred to as a
+  "guest-only blob resource").
+  \item a host memory allocation (referred to as a
+  "host-only blob resource").
+  \item a guest memory and host memory allocation (referred
+  to as a "default blob resource").
+  \end{itemize*}
+
+The memory properties of the blob resource MUST be described by
+\field{blob_mem}, which MUST be non-zero.
+
+For default and guest-only blob resources, \field{nents} guest
+system pages are assigned to the resource.  For default blob
+resources, these guest pages are used for transfer operations.
+
+Host allocations depend on whether VIRTIO_GPU_F_VIRGL is supported.
+If VIRTIO_GPU_F_VIRGL is not supported, then:
+
+  \begin{itemize*}
+  \item \field{blob_mem} MUST be VIRTIO_GPU_BLOB_MEM_HOSTSYS for host-only
+  blob resources
+  \item \field{blob_mem} MUST be VIRTIO_GPU_BLOB_MEM_HOSTSYS_GUEST for
+  default blob resources
+  \end{itemize*}
+
+For the above above cases, host system memory is allocated by the device.
+
+If VIRTIO_GPU_F_VIRGL is supported, then:
+
+  \begin{itemize*}
+  \item \field{blob_mem} MUST be VIRTIO_GPU_BLOB_MEM_HOST3D for host-only
+  blob resources
+  \item \field{blob_mem} MUST be VIRTIO_GPU_BLOB_MEM_HOST3D_GUEST for
+  default resources
+  \end{itemize*}
+
+For the above cases, the virtio-gpu resource MUST be created from the
+rendering context local object identified by the \field{blob_id}. The
+actual allocation is done via VIRTIO_GPU_CMD_SUBMIT_3D.
+
+VIRTIO_GPU_BLOB_MEM_GUEST is valid regardless whether VIRTIO_GPU_F_VIRGL
+is supported or not.
+
+The driver MUST inform the device if the blob resource is used for
+memory access, sharing between driver instances and/or sharing with
+other devices. This is done via the \field{blob_flags} field.
+
+If VIRTIO_GPU_F_VIRGL is set, both VIRTIO_GPU_CMD_TRANSFER_TO_HOST_3D
+and VIRTIO_GPU_CMD_TRANSFER_FROM_HOST_3D may be used to update the
+resource. There is no restriction on the image/buffer view the driver
+has on the blob resource.
+
+VIRTIO_GPU_CMD_TRANSFER_TO_HOST_2D, VIRTIO_GPU_CMD_SET_SCANOUT and
+VIRTIO_GPU_CMD_RESOURCE_FLUSH MAY be used with blob resources as well,
+subject to the following restrictions:
+
+  \begin{itemize*}
+  \item the driver MUST have a 4-byte per pixel 2D image view of the
+        blob resource.
+  \item the device MUST have a 4-byte per pixel 2D image view of the
+        blob resource, or create one if does not exist.
+  \end{itemize*}
+
+For host-only blob resources, transfer operations MAY synchronize
+caches.
+
 \end{description}
 
 \subsubsection{Device Operation: controlq (3d)}\label{sec:Device Types / GPU Device / Device Operation / Device Operation: controlq (3d)}
-- 
2.24.1