mirror of
https://github.com/xemu-project/xemu.git
synced 2024-11-27 05:20:50 +00:00
bd59f2a182
This matches the nomenclature that is generally used. Also commonly used is client/server, but it is not as clear because sometimes the front-end exposes a passive (server) socket that the back-end connects to. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210226143413.188046-4-pbonzini@redhat.com> Message-Id: <20220321153037.3622127-7-alex.bennee@linaro.org> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
244 lines
6.2 KiB
ReStructuredText
244 lines
6.2 KiB
ReStructuredText
=======================
|
|
Vhost-user-gpu Protocol
|
|
=======================
|
|
|
|
..
|
|
Licence: This work is licensed under the terms of the GNU GPL,
|
|
version 2 or later. See the COPYING file in the top-level
|
|
directory.
|
|
|
|
.. contents:: Table of Contents
|
|
|
|
Introduction
|
|
============
|
|
|
|
The vhost-user-gpu protocol is aiming at sharing the rendering result
|
|
of a virtio-gpu, done from a vhost-user back-end process to a vhost-user
|
|
front-end process (such as QEMU). It bears a resemblance to a display
|
|
server protocol, if you consider QEMU as the display server and the
|
|
back-end as the client, but in a very limited way. Typically, it will
|
|
work by setting a scanout/display configuration, before sending flush
|
|
events for the display updates. It will also update the cursor shape
|
|
and position.
|
|
|
|
The protocol is sent over a UNIX domain stream socket, since it uses
|
|
socket ancillary data to share opened file descriptors (DMABUF fds or
|
|
shared memory). The socket is usually obtained via
|
|
``VHOST_USER_GPU_SET_SOCKET``.
|
|
|
|
Requests are sent by the *back-end*, and the optional replies by the
|
|
*front-end*.
|
|
|
|
Wire format
|
|
===========
|
|
|
|
Unless specified differently, numbers are in the machine native byte
|
|
order.
|
|
|
|
A vhost-user-gpu message (request and reply) consists of 3 header
|
|
fields and a payload.
|
|
|
|
+---------+-------+------+---------+
|
|
| request | flags | size | payload |
|
|
+---------+-------+------+---------+
|
|
|
|
Header
|
|
------
|
|
|
|
:request: ``u32``, type of the request
|
|
|
|
:flags: ``u32``, 32-bit bit field:
|
|
|
|
- Bit 2 is the reply flag - needs to be set on each reply
|
|
|
|
:size: ``u32``, size of the payload
|
|
|
|
Payload types
|
|
-------------
|
|
|
|
Depending on the request type, **payload** can be:
|
|
|
|
VhostUserGpuCursorPos
|
|
^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
+------------+---+---+
|
|
| scanout-id | x | y |
|
|
+------------+---+---+
|
|
|
|
:scanout-id: ``u32``, the scanout where the cursor is located
|
|
|
|
:x/y: ``u32``, the cursor position
|
|
|
|
VhostUserGpuCursorUpdate
|
|
^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
+-----+-------+-------+--------+
|
|
| pos | hot_x | hot_y | cursor |
|
|
+-----+-------+-------+--------+
|
|
|
|
:pos: a ``VhostUserGpuCursorPos``, the cursor location
|
|
|
|
:hot_x/hot_y: ``u32``, the cursor hot location
|
|
|
|
:cursor: ``[u32; 64 * 64]``, 64x64 RGBA cursor data (PIXMAN_a8r8g8b8 format)
|
|
|
|
VhostUserGpuScanout
|
|
^^^^^^^^^^^^^^^^^^^
|
|
|
|
+------------+---+---+
|
|
| scanout-id | w | h |
|
|
+------------+---+---+
|
|
|
|
:scanout-id: ``u32``, the scanout configuration to set
|
|
|
|
:w/h: ``u32``, the scanout width/height size
|
|
|
|
VhostUserGpuUpdate
|
|
^^^^^^^^^^^^^^^^^^
|
|
|
|
+------------+---+---+---+---+------+
|
|
| scanout-id | x | y | w | h | data |
|
|
+------------+---+---+---+---+------+
|
|
|
|
:scanout-id: ``u32``, the scanout content to update
|
|
|
|
:x/y/w/h: ``u32``, region of the update
|
|
|
|
:data: RGB data (PIXMAN_x8r8g8b8 format)
|
|
|
|
VhostUserGpuDMABUFScanout
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
+------------+---+---+---+---+-----+-----+--------+-------+--------+
|
|
| scanout-id | x | y | w | h | fdw | fwh | stride | flags | fourcc |
|
|
+------------+---+---+---+---+-----+-----+--------+-------+--------+
|
|
|
|
:scanout-id: ``u32``, the scanout configuration to set
|
|
|
|
:x/y: ``u32``, the location of the scanout within the DMABUF
|
|
|
|
:w/h: ``u32``, the scanout width/height size
|
|
|
|
:fdw/fdh/stride/flags: ``u32``, the DMABUF width/height/stride/flags
|
|
|
|
:fourcc: ``i32``, the DMABUF fourcc
|
|
|
|
|
|
C structure
|
|
-----------
|
|
|
|
In QEMU the vhost-user-gpu message is implemented with the following struct:
|
|
|
|
.. code:: c
|
|
|
|
typedef struct VhostUserGpuMsg {
|
|
uint32_t request; /* VhostUserGpuRequest */
|
|
uint32_t flags;
|
|
uint32_t size; /* the following payload size */
|
|
union {
|
|
VhostUserGpuCursorPos cursor_pos;
|
|
VhostUserGpuCursorUpdate cursor_update;
|
|
VhostUserGpuScanout scanout;
|
|
VhostUserGpuUpdate update;
|
|
VhostUserGpuDMABUFScanout dmabuf_scanout;
|
|
struct virtio_gpu_resp_display_info display_info;
|
|
uint64_t u64;
|
|
} payload;
|
|
} QEMU_PACKED VhostUserGpuMsg;
|
|
|
|
Protocol features
|
|
-----------------
|
|
|
|
None yet.
|
|
|
|
As the protocol may need to evolve, new messages and communication
|
|
changes are negotiated thanks to preliminary
|
|
``VHOST_USER_GPU_GET_PROTOCOL_FEATURES`` and
|
|
``VHOST_USER_GPU_SET_PROTOCOL_FEATURES`` requests.
|
|
|
|
Communication
|
|
=============
|
|
|
|
Message types
|
|
-------------
|
|
|
|
``VHOST_USER_GPU_GET_PROTOCOL_FEATURES``
|
|
:id: 1
|
|
:request payload: N/A
|
|
:reply payload: ``u64``
|
|
|
|
Get the supported protocol features bitmask.
|
|
|
|
``VHOST_USER_GPU_SET_PROTOCOL_FEATURES``
|
|
:id: 2
|
|
:request payload: ``u64``
|
|
:reply payload: N/A
|
|
|
|
Enable protocol features using a bitmask.
|
|
|
|
``VHOST_USER_GPU_GET_DISPLAY_INFO``
|
|
:id: 3
|
|
:request payload: N/A
|
|
:reply payload: ``struct virtio_gpu_resp_display_info`` (from virtio specification)
|
|
|
|
Get the preferred display configuration.
|
|
|
|
``VHOST_USER_GPU_CURSOR_POS``
|
|
:id: 4
|
|
:request payload: ``VhostUserGpuCursorPos``
|
|
:reply payload: N/A
|
|
|
|
Set/show the cursor position.
|
|
|
|
``VHOST_USER_GPU_CURSOR_POS_HIDE``
|
|
:id: 5
|
|
:request payload: ``VhostUserGpuCursorPos``
|
|
:reply payload: N/A
|
|
|
|
Set/hide the cursor.
|
|
|
|
``VHOST_USER_GPU_CURSOR_UPDATE``
|
|
:id: 6
|
|
:request payload: ``VhostUserGpuCursorUpdate``
|
|
:reply payload: N/A
|
|
|
|
Update the cursor shape and location.
|
|
|
|
``VHOST_USER_GPU_SCANOUT``
|
|
:id: 7
|
|
:request payload: ``VhostUserGpuScanout``
|
|
:reply payload: N/A
|
|
|
|
Set the scanout resolution. To disable a scanout, the dimensions
|
|
width/height are set to 0.
|
|
|
|
``VHOST_USER_GPU_UPDATE``
|
|
:id: 8
|
|
:request payload: ``VhostUserGpuUpdate``
|
|
:reply payload: N/A
|
|
|
|
Update the scanout content. The data payload contains the graphical bits.
|
|
The display should be flushed and presented.
|
|
|
|
``VHOST_USER_GPU_DMABUF_SCANOUT``
|
|
:id: 9
|
|
:request payload: ``VhostUserGpuDMABUFScanout``
|
|
:reply payload: N/A
|
|
|
|
Set the scanout resolution/configuration, and share a DMABUF file
|
|
descriptor for the scanout content, which is passed as ancillary
|
|
data. To disable a scanout, the dimensions width/height are set
|
|
to 0, there is no file descriptor passed.
|
|
|
|
``VHOST_USER_GPU_DMABUF_UPDATE``
|
|
:id: 10
|
|
:request payload: ``VhostUserGpuUpdate``
|
|
:reply payload: empty payload
|
|
|
|
The display should be flushed and presented according to updated
|
|
region from ``VhostUserGpuUpdate``.
|
|
|
|
Note: there is no data payload, since the scanout is shared thanks
|
|
to DMABUF, that must have been set previously with
|
|
``VHOST_USER_GPU_DMABUF_SCANOUT``.
|