drm/i915/guc: Selftest for stealing of guc ids

Testing the stealing of guc ids is hard from user space as we have 64k
guc_ids. Add a selftest, which artificially reduces the number of guc
ids, and forces a steal.

The test creates a spinner which is used to block all subsequent
submissions until it completes. Next, a loop creates a context and a NOP
request each iteration until the guc_ids are exhausted (request creation
returns -EAGAIN). The spinner is ended, unblocking all requests created
in the loop. At this point all guc_ids are exhausted but are available
to steal. Try to create another request which should successfully steal
a guc_id. Wait on last request to complete, idle GPU, verify a guc_id
was stolen via a counter, and exit the test. Test also artificially
reduces the number of guc_ids so the test runs in a timely manner.

v2:
 (John Harrison)
  - s/stole/stolen
  - Fix some wording in test description
  - Rework indexing into context array
  - Add test description to commit message
  - Fix typo in commit message
 (Checkpatch)
  - s/guc/(guc) in NUMBER_MULTI_LRC_GUC_ID
v3:
 (John Harrison)
  - Set array value to NULL after extracting error
  - Fix a few typos in comments / error messages
  - Delete redundant comment in commit message

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211214170500.28569-8-matthew.brost@intel.com

drivers/gpu/drm/i915/gt/uc/intel_guc.h

@@ -94,6 +94,11 @@ struct intel_guc {
 		 * @guc_ids: used to allocate new guc_ids, single-lrc
 		 */
 		struct ida guc_ids;
+		/**
+		 * @num_guc_ids: Number of guc_ids, selftest feature to be able
+		 * to reduce this number while testing.
+		 */
+		int num_guc_ids;
 		/**
 		 * @guc_ids_bitmap: used to allocate new guc_ids, multi-lrc
 		 */
@@ -202,6 +207,13 @@ struct intel_guc {
 		 */
 		struct delayed_work work;
 	} timestamp;
+
+#ifdef CONFIG_DRM_I915_SELFTEST
+	/**
+	 * @number_guc_id_stolen: The number of guc_ids that have been stolen
+	 */
+	int number_guc_id_stolen;
+#endif
 };
 
 static inline struct intel_guc *log_to_guc(struct intel_guc_log *log)

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

@@ -145,7 +145,8 @@ guc_create_parallel(struct intel_engine_cs **engines,
  * use should be low and 1/16 should be sufficient. Minimum of 32 guc_ids for
  * multi-lrc.
  */
-#define NUMBER_MULTI_LRC_GUC_ID		(GUC_MAX_LRC_DESCRIPTORS / 16)
+#define NUMBER_MULTI_LRC_GUC_ID(guc)	\
+	((guc)->submission_state.num_guc_ids / 16)
 
 /*
  * Below is a set of functions which control the GuC scheduling state which
@@ -1775,7 +1776,7 @@ int intel_guc_submission_init(struct intel_guc *guc)
 		  destroyed_worker_func);
 
 	guc->submission_state.guc_ids_bitmap =
-		bitmap_zalloc(NUMBER_MULTI_LRC_GUC_ID, GFP_KERNEL);
+		bitmap_zalloc(NUMBER_MULTI_LRC_GUC_ID(guc), GFP_KERNEL);
 	if (!guc->submission_state.guc_ids_bitmap)
 		return -ENOMEM;
 
@@ -1869,13 +1870,13 @@ static int new_guc_id(struct intel_guc *guc, struct intel_context *ce)
 
 	if (intel_context_is_parent(ce))
 		ret = bitmap_find_free_region(guc->submission_state.guc_ids_bitmap,
-					      NUMBER_MULTI_LRC_GUC_ID,
+					      NUMBER_MULTI_LRC_GUC_ID(guc),
 					      order_base_2(ce->parallel.number_children
 							   + 1));
 	else
 		ret = ida_simple_get(&guc->submission_state.guc_ids,
-				     NUMBER_MULTI_LRC_GUC_ID,
-				     GUC_MAX_LRC_DESCRIPTORS,
+				     NUMBER_MULTI_LRC_GUC_ID(guc),
+				     guc->submission_state.num_guc_ids,
 				     GFP_KERNEL | __GFP_RETRY_MAYFAIL |
 				     __GFP_NOWARN);
 	if (unlikely(ret < 0))
@@ -1941,6 +1942,10 @@ static int steal_guc_id(struct intel_guc *guc, struct intel_context *ce)
 
 		set_context_guc_id_invalid(cn);
 
+#ifdef CONFIG_DRM_I915_SELFTEST
+		guc->number_guc_id_stolen++;
+#endif
+
 		return 0;
 	} else {
 		return -EAGAIN;
@@ -3779,6 +3784,7 @@ static bool __guc_submission_selected(struct intel_guc *guc)
 
 void intel_guc_submission_init_early(struct intel_guc *guc)
 {
+	guc->submission_state.num_guc_ids = GUC_MAX_LRC_DESCRIPTORS;
 	guc->submission_supported = __guc_submission_supported(guc);
 	guc->submission_selected = __guc_submission_selected(guc);
 }

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

@@ -3,8 +3,21 @@
  * Copyright <EFBFBD><EFBFBD> 2021 Intel Corporation
  */
 
+#include "selftests/igt_spinner.h"
 #include "selftests/intel_scheduler_helpers.h"
 
+static int request_add_spin(struct i915_request *rq, struct igt_spinner *spin)
+{
+	int err = 0;
+
+	i915_request_get(rq);
+	i915_request_add(rq);
+	if (spin && !igt_wait_for_spinner(spin, rq))
+		err = -ETIMEDOUT;
+
+	return err;
+}
+
 static struct i915_request *nop_user_request(struct intel_context *ce,
 					     struct i915_request *from)
 {
@@ -110,10 +123,170 @@ err:
 	return ret;
 }
 
+/*
+ * intel_guc_steal_guc_ids - Test to exhaust all guc_ids and then steal one
+ *
+ * This test creates a spinner which is used to block all subsequent submissions
+ * until it completes. Next, a loop creates a context and a NOP request each
+ * iteration until the guc_ids are exhausted (request creation returns -EAGAIN).
+ * The spinner is ended, unblocking all requests created in the loop. At this
+ * point all guc_ids are exhausted but are available to steal. Try to create
+ * another request which should successfully steal a guc_id. Wait on last
+ * request to complete, idle GPU, verify a guc_id was stolen via a counter, and
+ * exit the test. Test also artificially reduces the number of guc_ids so the
+ * test runs in a timely manner.
+ */
+static int intel_guc_steal_guc_ids(void *arg)
+{
+	struct intel_gt *gt = arg;
+	struct intel_guc *guc = &gt->uc.guc;
+	int ret, sv, context_index = 0;
+	intel_wakeref_t wakeref;
+	struct intel_engine_cs *engine;
+	struct intel_context **ce;
+	struct igt_spinner spin;
+	struct i915_request *spin_rq = NULL, *rq, *last = NULL;
+	int number_guc_id_stolen = guc->number_guc_id_stolen;
+
+	ce = kzalloc(sizeof(*ce) * GUC_MAX_LRC_DESCRIPTORS, GFP_KERNEL);
+	if (!ce) {
+		pr_err("Context array allocation failed\n");
+		return -ENOMEM;
+	}
+
+	wakeref = intel_runtime_pm_get(gt->uncore->rpm);
+	engine = intel_selftest_find_any_engine(gt);
+	sv = guc->submission_state.num_guc_ids;
+	guc->submission_state.num_guc_ids = 4096;
+
+	/* Create spinner to block requests in below loop */
+	ce[context_index] = intel_context_create(engine);
+	if (IS_ERR(ce[context_index])) {
+		ret = PTR_ERR(ce[context_index]);
+		ce[context_index] = NULL;
+		pr_err("Failed to create context: %d\n", ret);
+		goto err_wakeref;
+	}
+	ret = igt_spinner_init(&spin, engine->gt);
+	if (ret) {
+		pr_err("Failed to create spinner: %d\n", ret);
+		goto err_contexts;
+	}
+	spin_rq = igt_spinner_create_request(&spin, ce[context_index],
+					     MI_ARB_CHECK);
+	if (IS_ERR(spin_rq)) {
+		ret = PTR_ERR(spin_rq);
+		pr_err("Failed to create spinner request: %d\n", ret);
+		goto err_contexts;
+	}
+	ret = request_add_spin(spin_rq, &spin);
+	if (ret) {
+		pr_err("Failed to add Spinner request: %d\n", ret);
+		goto err_spin_rq;
+	}
+
+	/* Use all guc_ids */
+	while (ret != -EAGAIN) {
+		ce[++context_index] = intel_context_create(engine);
+		if (IS_ERR(ce[context_index])) {
+			ret = PTR_ERR(ce[context_index--]);
+			ce[context_index] = NULL;
+			pr_err("Failed to create context: %d\n", ret);
+			goto err_spin_rq;
+		}
+
+		rq = nop_user_request(ce[context_index], spin_rq);
+		if (IS_ERR(rq)) {
+			ret = PTR_ERR(rq);
+			rq = NULL;
+			if (ret != -EAGAIN) {
+				pr_err("Failed to create request, %d: %d\n",
+				       context_index, ret);
+				goto err_spin_rq;
+			}
+		} else {
+			if (last)
+				i915_request_put(last);
+			last = rq;
+		}
+	}
+
+	/* Release blocked requests */
+	igt_spinner_end(&spin);
+	ret = intel_selftest_wait_for_rq(spin_rq);
+	if (ret) {
+		pr_err("Spin request failed to complete: %d\n", ret);
+		i915_request_put(last);
+		goto err_spin_rq;
+	}
+	i915_request_put(spin_rq);
+	igt_spinner_fini(&spin);
+	spin_rq = NULL;
+
+	/* Wait for last request */
+	ret = i915_request_wait(last, 0, HZ * 30);
+	i915_request_put(last);
+	if (ret < 0) {
+		pr_err("Last request failed to complete: %d\n", ret);
+		goto err_spin_rq;
+	}
+
+	/* Try to steal guc_id */
+	rq = nop_user_request(ce[context_index], NULL);
+	if (IS_ERR(rq)) {
+		ret = PTR_ERR(rq);
+		pr_err("Failed to steal guc_id, %d: %d\n", context_index, ret);
+		goto err_spin_rq;
+	}
+
+	/* Wait for request with stolen guc_id */
+	ret = i915_request_wait(rq, 0, HZ);
+	i915_request_put(rq);
+	if (ret < 0) {
+		pr_err("Request with stolen guc_id failed to complete: %d\n",
+		       ret);
+		goto err_spin_rq;
+	}
+
+	/* Wait for idle */
+	ret = intel_gt_wait_for_idle(gt, HZ * 30);
+	if (ret < 0) {
+		pr_err("GT failed to idle: %d\n", ret);
+		goto err_spin_rq;
+	}
+
+	/* Verify a guc_id was stolen */
+	if (guc->number_guc_id_stolen == number_guc_id_stolen) {
+		pr_err("No guc_id was stolen");
+		ret = -EINVAL;
+	} else {
+		ret = 0;
+	}
+
+err_spin_rq:
+	if (spin_rq) {
+		igt_spinner_end(&spin);
+		intel_selftest_wait_for_rq(spin_rq);
+		i915_request_put(spin_rq);
+		igt_spinner_fini(&spin);
+		intel_gt_wait_for_idle(gt, HZ * 30);
+	}
+err_contexts:
+	for (; context_index >= 0 && ce[context_index]; --context_index)
+		intel_context_put(ce[context_index]);
+err_wakeref:
+	intel_runtime_pm_put(gt->uncore->rpm, wakeref);
+	kfree(ce);
+	guc->submission_state.num_guc_ids = sv;
+
+	return ret;
+}
+
 int intel_guc_live_selftests(struct drm_i915_private *i915)
 {
 	static const struct i915_subtest tests[] = {
 		SUBTEST(intel_guc_scrub_ctbs),
+		SUBTEST(intel_guc_steal_guc_ids),
 	};
 	struct intel_gt *gt = &i915->gt;