[PATCH 1/2] drm/i915/guc: Fix for potential false positives in GuC hang selftest

[John.C.Harrison at Intel.com]

From: John Harrison <John.C.Harrison at Intel.com>

Noticed that the hangcheck selftest is submitting a non-preemptoble
spinner. That means that even if the GuC does not die, the heartbeat
will still kick in and trigger a reset. Which is rather defeating the
purpose of the test - to verify that the heartbeat will kick in if the
GuC itself has died. The test is deliberately killing the GuC, so it
should never hit the case of a non-dead GuC. But it is not impossible
that the kill might fail at some future point due to other driver
re-work.

So, make the spinner pre-emptible. That way the heartbeat can get
through if the GuC is alive and context switching. Thus a reset only
happens if the GuC dies. Thus, if the kill should stop working the
test will now fail rather than claim to pass.

Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
---
 drivers/gpu/drm/i915/gt/uc/selftest_guc_hangcheck.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/uc/selftest_guc_hangcheck.c b/drivers/gpu/drm/i915/gt/uc/selftest_guc_hangcheck.c
index 34b5d952e2bcb..26fdc392fce6c 100644
--- a/drivers/gpu/drm/i915/gt/uc/selftest_guc_hangcheck.c
+++ b/drivers/gpu/drm/i915/gt/uc/selftest_guc_hangcheck.c
@@ -74,7 +74,7 @@ static int intel_hang_guc(void *arg)
 		goto err;
 	}
 
-	rq = igt_spinner_create_request(&spin, ce, MI_NOOP);
+	rq = igt_spinner_create_request(&spin, ce, MI_ARB_CHECK);
 	intel_context_put(ce);
 	if (IS_ERR(rq)) {
 		ret = PTR_ERR(rq);
-- 
2.41.0