Yiwei Zhang <zzyi...@gmail.com> writes:
> Venus and later native contexts have their own fence context along with
> multiple timelines within. Fences wtih VIRTIO_GPU_FLAG_INFO_RING_IDX in
> the flags must be dispatched to be created on the target context. Fence
> signaling also has to be handled on the specific timeline within that
> target context.
>
> Before this change, venus fencing is completely broken if the host
> driver doesn't support implicit fencing with external memory objects.
> Frames can go backwards along with random artifacts on screen if the
> host driver doesn't attach an implicit fence to the render target. The
> symptom could be hidden by certain guest wsi backend that waits on a
> venus native VkFence object for the actual payload with limited present
> modes or under special configs. e.g. x11 mailbox or xwayland.
>
> After this change, everything related to venus fencing starts making
> sense. Confirmed this via guest and host side perfetto tracing.
>
> Changes since v1:
> - Minor commit msg updates based on feedbacks from BALATON
>
> Cc: qemu-sta...@nongnu.org
> Fixes: 94d0ea1c1928 ("virtio-gpu: Support Venus context")
> Signed-off-by: Yiwei Zhang <zzyi...@gmail.com>
Queued to virtio-gpu/next (in maintainer/may-2025), thanks.
<snip>
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
