[Mesa-dev] [RFC] Linux Graphics Next: Explicit fences everywhere and no BO fences - initial proposal

[Daniel Vetter]

On Tue, Apr 27, 2021 at 06:27:27PM +0000, Simon Ser wrote:
> On Tuesday, April 27th, 2021 at 8:01 PM, Alex Deucher <alexdeucher at gmail.com> wrote:
> 
> > It's an upcoming requirement for windows[1], so you are likely to
> > start seeing this across all GPU vendors that support windows. I
> > think the timing depends on how quickly the legacy hardware support
> > sticks around for each vendor.
> 
> Hm, okay.
> 
> Will using the existing explicit synchronization APIs make it work
> properly? (e.g. IN_FENCE_FD + OUT_FENCE_PTR in KMS, EGL_KHR_fence_sync +
> EGL_ANDROID_native_fence_sync + EGL_KHR_wait_sync in EGL)

If you have hw which really _only_ supports userspace direct submission
(i.e. the ringbuffer has to be in the same gpu vm as everything else by
design, and can't be protected at all with e.g. read-only pte entries)
then all that stuff would be broken.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch