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This an incremental refactor towards multiple dma-fence contexts
in virtio-gpu. Since all fences are still allocated using
&virtio_gpu_fence_driver.context, nothing should break and every
processed fence will be signaled.
The overall idea is every 3D context can allocate a number of
dma-fence contexts. Each dma-fence context refers to it's own
timeline.
For example, consider the following case where virgl submits
commands to the GPU (fence ids 1, 3) and does a metadata query with
the CPU (fence id 5). In a different process, gfxstream submits
commands to the GPU (fence ids 2, 4).
fence_id (&dma_fence.seqno) | 1 2 3 4 5
----------------------------------|-----------
fence_ctx 0 (virgl gpu) | 1 3
fence_ctx 1 (virgl metadata query)| 5
fence_ctx 2 (gfxstream gpu) | 2 4
With multiple fence contexts, we can wait for the metadata query
to finish without waiting for the virgl gpu to finish. virgl gpu
does not have to wait for gfxstream gpu. The fence id still is the
monotonically increasing sequence number, but it's only revelant to
the specific dma-fence context.
To fully enable this feature, we'll need to:
- have each 3d context allocate a number of fence contexts. Not
too hard with explicit context initialization on the horizon.
- have guest userspace specify fence context when performing
ioctls.
- tag each fence emitted to the host with the fence context
information. virtio_gpu_ctrl_hdr has padding + flags available,
so that should be easy.
This change goes in the direction specified above, by:
- looking up the virtgpu_fence given a fence_id
- signalling all prior fences in a given context
- signalling current fence
v2: fix grammar in comment
v3: add r-b tags
Reviewed-by: Anthoine Bourgeois <anthoine.bourgeois@gmail.com>
Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20201201021623.619-3-gurchetansingh@chromium.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.