On Thu, Jun 19, 2025 at 11:45 PM Alex Bennée <alex.ben...@linaro.org> wrote:
>
> Yiwei Zhang <zzyi...@gmail.com> writes:
>
> > On Sun, Jun 8, 2025 at 1:24 AM Akihiko Odaki
> > <od...@rsg.ci.i.u-tokyo.ac.jp> wrote:
> >>
> >> On 2025/06/06 1:26, Alex Bennée wrote:
> >> > From: Yiwei Zhang <zzyi...@gmail.com>
> >> >
> >> > 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.
> >> >
> >> > Cc: qemu-sta...@nongnu.org
> >> > Fixes: 94d0ea1c1928 ("virtio-gpu: Support Venus context")
> >>
> >> I suggest moving this in the front of the patch series to ease backporting.
> >>
> >> I also wonder if "[PULL 11/17] ui/gtk-gl-area: Remove extra draw call in
> >> refresh" requires Cc: qemu-sta...@nongnu.org. Fixing -display gtk,gl=on
> >> for Wayland sounds as important as this patch.
> >>
> >> Regards,
> >> Akihiko Odaki
> >
> > Hi Alex,
> >
> > +1 for Akihiko's point. I'm also curious when will the venus fix land
> > in-tree?
>
> We have a problem that there are two contradictory bugs - one that shows
> up in the x86/kvm case and one in the aarch64/tcg case. Both are caused
> by the weird lifetime semantics of the virgl resource vs QEMU memory
> region and we haven't found a solution that solves both yet.Sounds like irrelevant to the venus fix. Might be worth filing a virglrenderer issue with some details. More eyes would be helpful if this turns out to be some known kvm issue seen before on other vmms. > > I'm currently busy with other stuff and need to do a sweep of my other > maintainer trees for 10.1. Once I've done that I'll have another go at > coming up with a solution unless someone else beats me to it. Understood. Hope there's a chance to move the venus fix up in the queue to land first when you get to this again. Thanks! > > -- > Alex Bennée > Virtualisation Tech Lead @ Linaro
