On Tue, May 25, 2021 at 2:18 PM Jason Ekstrand <jason@xxxxxxxxxxxxxx> wrote: > Modern userspace APIs like Vulkan are built on an explicit > synchronization model. This doesn't always play nicely with the > implicit synchronization used in the kernel and assumed by X11 and > Wayland. The client -> compositor half of the synchronization isn't too > bad, at least on intel, because we can control whether or not i915 > synchronizes on the buffer and whether or not it's considered written. We might have an important use case for this half, for virtio-gpu and Chrome OS. When the guest compositor acts as a proxy to connect guest apps to the host compositor, implicit fencing requires the guest compositor to do a wait before forwarding the buffer to the host compositor. With this patch, the guest compositor can extract the dma-fence from the buffer, and if the fence is a virtio-gpu fence, forward both the fence and the buffer to the host compositor. It will allow us to convert a guest-side wait into a host-side wait.
