[Intel-gfx] [PATCH i-g-t] i915/gem_ctx_persistence: Check precision of hostile cancellation

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-02-25 18:08:14)
> 
> On 24/02/2020 21:56, Chris Wilson wrote:
> > Check that if we have to remove a hostile request from a non-persistent
> > context, we do so without harming any other concurrent users.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> > +     /* All other spinners should be left unharmed */
> > +     gem_quiescent_gpu(i915);
> > +     igt_assert_eq(sync_fence_wait(fence, reset_timeout_ms), 0);
> > +     igt_assert_eq(sync_fence_status(fence), 1);
> 
> I don't quite get this test. Why would other spinners be unharmed? They 
> are non-preemptible as well. And non-persistent spinner is alone on the 
> engine. So what aspect you wanted to test?

Per-engine reset. Termination of the non-persistent context should be
clean and precise, we don't allow creation of non-persistent contexts
unless we have that level of surgical precision. Otherwise it becomes a
new attack vector.
-Chris