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

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-02-25 18:18:12)
> 
> On 25/02/2020 18:11, Chris Wilson wrote:
> > 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.
> 
> If it is just engine reset then it does what it says on the tin.

I shall update the description to clarify that then :)
-Chris