drm/i915/selftests: Add initial GuC selftest for scrubbing lost G2H

While debugging an issue with full GT resets I went down a rabbit hole
thinking the scrubbing of lost G2H wasn't working correctly. This proved
to be incorrect as this was working just fine but this chase inspired me
to write a selftest to prove that this works. This simple selftest
injects errors dropping various G2H and then issues a full GT reset
proving that the scrubbing of these G2H doesn't blow up.

v2:
 (Daniel Vetter)
  - Use ifdef instead of macros for selftests
v3:
 (Checkpatch)
  - A space after 'switch' statement
v4:
 (Daniele)
  - A comment saying GT won't idle if G2H are lost

Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210909164744.31249-12-matthew.brost@intel.com

drivers/gpu/drm/i915/gt/intel_context_types.h

@@ -198,6 +198,24 @@ struct intel_context {
 	 */
 	u8 guc_prio;
 	u32 guc_prio_count[GUC_CLIENT_PRIORITY_NUM];
+
+#ifdef CONFIG_DRM_I915_SELFTEST
+	/**
+	 * @drop_schedule_enable: Force drop of schedule enable G2H for selftest
+	 */
+	bool drop_schedule_enable;
+
+	/**
+	 * @drop_schedule_disable: Force drop of schedule disable G2H for
+	 * selftest
+	 */
+	bool drop_schedule_disable;
+
+	/**
+	 * @drop_deregister: Force drop of deregister G2H for selftest
+	 */
+	bool drop_deregister;
+#endif
 };
 
 #endif /* __INTEL_CONTEXT_TYPES__ */

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c

@@ -2639,6 +2639,13 @@ int intel_guc_deregister_done_process_msg(struct intel_guc *guc,
 
 	trace_intel_context_deregister_done(ce);
 
+#ifdef CONFIG_DRM_I915_SELFTEST
+	if (unlikely(ce->drop_deregister)) {
+		ce->drop_deregister = false;
+		return 0;
+	}
+#endif
+
 	if (context_wait_for_deregister_to_register(ce)) {
 		struct intel_runtime_pm *runtime_pm =
 			&ce->engine->gt->i915->runtime_pm;
@@ -2693,10 +2700,24 @@ int intel_guc_sched_done_process_msg(struct intel_guc *guc,
 	trace_intel_context_sched_done(ce);
 
 	if (context_pending_enable(ce)) {
+#ifdef CONFIG_DRM_I915_SELFTEST
+		if (unlikely(ce->drop_schedule_enable)) {
+			ce->drop_schedule_enable = false;
+			return 0;
+		}
+#endif
+
 		clr_context_pending_enable(ce);
 	} else if (context_pending_disable(ce)) {
 		bool banned;
 
+#ifdef CONFIG_DRM_I915_SELFTEST
+		if (unlikely(ce->drop_schedule_disable)) {
+			ce->drop_schedule_disable = false;
+			return 0;
+		}
+#endif
+
 		/*
 		 * Unpin must be done before __guc_signal_context_fence,
 		 * otherwise a race exists between the requests getting
@@ -3073,3 +3094,7 @@ bool intel_guc_virtual_engine_has_heartbeat(const struct intel_engine_cs *ve)
 
 	return false;
 }
+
+#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
+#include "selftest_guc.c"
+#endif

drivers/gpu/drm/i915/gt/uc/selftest_guc.c

@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright �� 2021 Intel Corporation
+ */
+
+#include "selftests/intel_scheduler_helpers.h"
+
+static struct i915_request *nop_user_request(struct intel_context *ce,
+					     struct i915_request *from)
+{
+	struct i915_request *rq;
+	int ret;
+
+	rq = intel_context_create_request(ce);
+	if (IS_ERR(rq))
+		return rq;
+
+	if (from) {
+		ret = i915_sw_fence_await_dma_fence(&rq->submit,
+						    &from->fence, 0,
+						    I915_FENCE_GFP);
+		if (ret < 0) {
+			i915_request_put(rq);
+			return ERR_PTR(ret);
+		}
+	}
+
+	i915_request_get(rq);
+	i915_request_add(rq);
+
+	return rq;
+}
+
+static int intel_guc_scrub_ctbs(void *arg)
+{
+	struct intel_gt *gt = arg;
+	int ret = 0;
+	int i;
+	struct i915_request *last[3] = {NULL, NULL, NULL}, *rq;
+	intel_wakeref_t wakeref;
+	struct intel_engine_cs *engine;
+	struct intel_context *ce;
+
+	wakeref = intel_runtime_pm_get(gt->uncore->rpm);
+	engine = intel_selftest_find_any_engine(gt);
+
+	/* Submit requests and inject errors forcing G2H to be dropped */
+	for (i = 0; i < 3; ++i) {
+		ce = intel_context_create(engine);
+		if (IS_ERR(ce)) {
+			ret = PTR_ERR(ce);
+			pr_err("Failed to create context, %d: %d\n", i, ret);
+			goto err;
+		}
+
+		switch (i) {
+		case 0:
+			ce->drop_schedule_enable = true;
+			break;
+		case 1:
+			ce->drop_schedule_disable = true;
+			break;
+		case 2:
+			ce->drop_deregister = true;
+			break;
+		}
+
+		rq = nop_user_request(ce, NULL);
+		intel_context_put(ce);
+
+		if (IS_ERR(rq)) {
+			ret = PTR_ERR(rq);
+			pr_err("Failed to create request, %d: %d\n", i, ret);
+			goto err;
+		}
+
+		last[i] = rq;
+	}
+
+	for (i = 0; i < 3; ++i) {
+		ret = i915_request_wait(last[i], 0, HZ);
+		if (ret < 0) {
+			pr_err("Last request failed to complete: %d\n", ret);
+			goto err;
+		}
+		i915_request_put(last[i]);
+		last[i] = NULL;
+	}
+
+	/* Force all H2G / G2H to be submitted / processed */
+	intel_gt_retire_requests(gt);
+	msleep(500);
+
+	/* Scrub missing G2H */
+	intel_gt_handle_error(engine->gt, -1, 0, "selftest reset");
+
+	/* GT will not idle if G2H are lost */
+	ret = intel_gt_wait_for_idle(gt, HZ);
+	if (ret < 0) {
+		pr_err("GT failed to idle: %d\n", ret);
+		goto err;
+	}
+
+err:
+	for (i = 0; i < 3; ++i)
+		if (last[i])
+			i915_request_put(last[i]);
+	intel_runtime_pm_put(gt->uncore->rpm, wakeref);
+
+	return ret;
+}
+
+int intel_guc_live_selftests(struct drm_i915_private *i915)
+{
+	static const struct i915_subtest tests[] = {
+		SUBTEST(intel_guc_scrub_ctbs),
+	};
+	struct intel_gt *gt = &i915->gt;
+
+	if (intel_gt_is_wedged(gt))
+		return 0;
+
+	if (!intel_uc_uses_guc_submission(&gt->uc))
+		return 0;
+
+	return intel_gt_live_subtests(tests, gt);
+}

drivers/gpu/drm/i915/selftests/i915_live_selftests.h

@@ -47,5 +47,6 @@ selftest(execlists, intel_execlists_live_selftests)
 selftest(ring_submission, intel_ring_submission_live_selftests)
 selftest(perf, i915_perf_live_selftests)
 selftest(slpc, intel_slpc_live_selftests)
+selftest(guc, intel_guc_live_selftests)
 /* Here be dragons: keep last to run last! */
 selftest(late_gt_pm, intel_gt_pm_late_selftests)

drivers/gpu/drm/i915/selftests/intel_scheduler_helpers.c

@@ -14,6 +14,18 @@
 #define REDUCED_PREEMPT		10
 #define WAIT_FOR_RESET_TIME	10000
 
+struct intel_engine_cs *intel_selftest_find_any_engine(struct intel_gt *gt)
+{
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+
+	for_each_engine(engine, gt, id)
+		return engine;
+
+	pr_err("No valid engine found!\n");
+	return NULL;
+}
+
 int intel_selftest_modify_policy(struct intel_engine_cs *engine,
 				 struct intel_selftest_saved_policy *saved,
 				 u32 modify_type)

drivers/gpu/drm/i915/selftests/intel_scheduler_helpers.h

@@ -10,6 +10,7 @@
 
 struct i915_request;
 struct intel_engine_cs;
+struct intel_gt;
 
 struct intel_selftest_saved_policy {
 	u32 flags;
@@ -23,6 +24,7 @@ enum selftest_scheduler_modify {
 	SELFTEST_SCHEDULER_MODIFY_FAST_RESET,
 };
 
+struct intel_engine_cs *intel_selftest_find_any_engine(struct intel_gt *gt);
 int intel_selftest_modify_policy(struct intel_engine_cs *engine,
 				 struct intel_selftest_saved_policy *saved,
 				 enum selftest_scheduler_modify modify_type);