[Intel-gfx] [PATCH] drm/i915/gt: Prevent timeslicing into unpreemptible requests

[Chris Wilson]

Quoting Chris Wilson (2020-05-27 14:02:14)
> We have a I915_REQUEST_NOPREEMPT flag that we set when we must prevent
> the HW from preempting during the course of this request. We need to
> honour this flag and protect the HW even if we have a heartbeat request,
> or other maximum priority barrier, pending. As such, restrict the
> timeslicing check to avoid preempting into the topmost priority band,
> leaving the unpreemptable requests in blissful peace running
> uninterrupted on the HW.
> 

Fixes: 2a98f4e65bba ("drm/i915: add infrastructure to hold off preemption on a request")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
-Chris