Hi Gerd, > > On Thu, Jul 29, 2021 at 01:16:57AM -0700, Vivek Kasireddy wrote: > > This feature enables the Guest to wait to know when a resource > > is completely consumed by the Host. > > virtio spec update? > > What are the exact semantics? [Kasireddy, Vivek] As of now, this is still a RFC version. If everyone (Weston Upstream, drm upstream and you) agree that this is a reasonable way to solve https://gitlab.freedesktop.org/wayland/weston/-/issues/514 then I'd go ahead and send out the spec updates and cleaner versions of these patches -- with more documentation. > > Why a new command? Can't you simply fence one of the commands sent > anyway (set_scanout probably for page-flip updates)? [Kasireddy, Vivek] Yes, I think I could add a fence (and an out_fence) to set-scanout-blob. > > (feature flag is probably needed even in case we don't need a new > command to make sure the host sends the completion when processing > the command is actually done, i.e. in case of qemu the recently added > fence support is there). [Kasireddy, Vivek] The recently added fence support was for resource_flush and specifically for GTK-UI or similar backends. I tried using the same mechanism for Wayland-UI backend but ran into the above Weston issue. This feature (OUT_FENCE) is a potential solution for this issue. Thanks, Vivek > > take care, > Gerd
