[PATCH v4 5/7] drm/i915/guc: Look for a guilty context when an engine reset fails

[John.C.Harrison at Intel.com]

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

Engine resets are supposed to never fail. But in the case when one
does (due to unknown reasons that normally come down to a missing
w/a), it is useful to get as much information out of the system as
possible. Given that the GuC intentionally dies on such a situation,
it is not possible to get a guilty context notification back. So do a
manual search instead. Given that GuC is dead, this is safe because
GuC won't be changing the engine state asynchronously.

v2: Change comment to be less alarming (Tvrtko)

Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
Acked-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
---
 .../gpu/drm/i915/gt/uc/intel_guc_submission.c   | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index ad4b2848b0f83..b6b4061e4b633 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -4755,11 +4755,24 @@ static void reset_fail_worker_func(struct work_struct *w)
 	guc->submission_state.reset_fail_mask = 0;
 	spin_unlock_irqrestore(&guc->submission_state.lock, flags);
 
-	if (likely(reset_fail_mask))
+	if (likely(reset_fail_mask)) {
+		struct intel_engine_cs *engine;
+		enum intel_engine_id id;
+
+		/*
+		 * GuC is toast at this point - it dead loops after sending the failed
+		 * reset notification. So need to manually determine the guilty context.
+		 * Note that it should be reliable to do this here because the GuC is
+		 * toast and will not be scheduling behind the KMD's back.
+		 */
+		for_each_engine_masked(engine, gt, reset_fail_mask, id)
+			intel_guc_find_hung_context(engine);
+
 		intel_gt_handle_error(gt, reset_fail_mask,
 				      I915_ERROR_CAPTURE,
-				      "GuC failed to reset engine mask=0x%x\n",
+				      "GuC failed to reset engine mask=0x%x",
 				      reset_fail_mask);
+	}
 }
 
 int intel_guc_engine_failure_process_msg(struct intel_guc *guc,
-- 
2.39.0