[Intel-gfx] [PATCH v2 3/3] drm/i915/selftests: Exercise adding requests to a full GGTT

[Chris Wilson]

A bug recently encountered involved the issue where are we were
submitting requests to different ppGTT, each would pin a segment of the
GGTT for its logical context and ring. However, this is invisible to
eviction as we do not tie the context/ring VMA to a request and so do
not automatically wait upon it them (instead they are marked as pinned,
prevent eviction entirely). Instead the eviction code must flush those
contexts by switching to the kernel context. This selftest tries to
fill the GGTT with contexts to exercise a path where the
switch-to-kernel-context failed to make forward progress and we fail
with ENOSPC.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/selftests/i915_gem_evict.c    | 121 +++++++++++++++++++++
 .../gpu/drm/i915/selftests/i915_live_selftests.h   |   1 +
 drivers/gpu/drm/i915/selftests/mock_context.c      |   6 +-
 3 files changed, 123 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_evict.c b/drivers/gpu/drm/i915/selftests/i915_gem_evict.c
index 5ea373221f49..53df8926be7f 100644
--- a/drivers/gpu/drm/i915/selftests/i915_gem_evict.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_evict.c
@@ -24,6 +24,8 @@
 
 #include "../i915_selftest.h"
 
+#include "mock_context.h"
+#include "mock_drm.h"
 #include "mock_gem_device.h"
 
 static int populate_ggtt(struct drm_i915_private *i915)
@@ -325,6 +327,116 @@ static int igt_evict_vm(void *arg)
 	return err;
 }
 
+static int igt_evict_contexts(void *arg)
+{
+	struct drm_i915_private *i915 = arg;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	struct reserved {
+		struct drm_mm_node node;
+		struct reserved *next;
+	} *reserved = NULL;
+	unsigned long count;
+	int err = 0;
+
+	/* Make the GGTT appear small (but leave just enough to function) */
+	count = 0;
+	mutex_lock(&i915->drm.struct_mutex);
+	do {
+		struct reserved *r;
+
+		r = kcalloc(1, sizeof(*r), GFP_KERNEL);
+		if (!r) {
+			err = -ENOMEM;
+			goto out_locked;
+		}
+
+		if (i915_gem_gtt_insert(&i915->ggtt.base, &r->node,
+					1ul << 20, 0, I915_COLOR_UNEVICTABLE,
+					16ul << 20, i915->ggtt.base.total,
+					PIN_NOEVICT)) {
+			kfree(r);
+			break;
+		}
+
+		r->next = reserved;
+		reserved = r;
+
+		count++;
+	} while (1);
+	mutex_unlock(&i915->drm.struct_mutex);
+	pr_info("Filled GGTT with %lu 1MiB nodes\n", count);
+
+	/* Overfill the GGTT with context objects and so try to evict one. */
+	for_each_engine(engine, i915, id) {
+		struct i915_sw_fence *fence;
+		struct drm_file *file;
+		unsigned long count = 0;
+		unsigned long timeout;
+
+		file = mock_file(i915);
+		if (IS_ERR(file))
+			return PTR_ERR(file);
+
+		timeout = round_jiffies_up(jiffies + HZ/2);
+		fence = i915_sw_fence_create_timer(timeout, GFP_KERNEL);
+		if (IS_ERR(fence))
+			return PTR_ERR(fence);
+
+		count = 0;
+		mutex_lock(&i915->drm.struct_mutex);
+		do {
+			struct drm_i915_gem_request *rq;
+			struct i915_gem_context *ctx;
+
+			ctx = live_context(i915, file);
+			if (!ctx)
+				break;
+
+			rq = i915_gem_request_alloc(engine, ctx);
+			if (IS_ERR(rq)) {
+				if (PTR_ERR(rq) != -ENOMEM) {
+					pr_err("Unexpected error from request alloc (ctx hw id %u, on %s): %d\n",
+					       ctx->hw_id, engine->name,
+					       (int)PTR_ERR(rq));
+					err = PTR_ERR(rq);
+				}
+				break;
+			}
+
+			i915_sw_fence_await_sw_fence_gfp(&rq->submit, fence,
+							 GFP_KERNEL);
+
+			i915_add_request(rq);
+			count++;
+		} while(!i915_sw_fence_done(fence));
+		mutex_unlock(&i915->drm.struct_mutex);
+
+		i915_sw_fence_timer_flush(fence);
+		pr_info("Submitted %lu contexts/requests on %s\n",
+			count, engine->name);
+
+		mock_file_free(i915, file);
+
+		if (err)
+			break;
+	}
+
+	mutex_lock(&i915->drm.struct_mutex);
+out_locked:
+	while (reserved) {
+		struct reserved *next = reserved->next;
+
+		drm_mm_remove_node(&reserved->node);
+		kfree(reserved);
+
+		reserved = next;
+	}
+	mutex_unlock(&i915->drm.struct_mutex);
+
+	return err;
+}
+
 int i915_gem_evict_mock_selftests(void)
 {
 	static const struct i915_subtest tests[] = {
@@ -348,3 +460,12 @@ int i915_gem_evict_mock_selftests(void)
 	drm_dev_unref(&i915->drm);
 	return err;
 }
+
+int i915_gem_evict_live_selftests(struct drm_i915_private *i915)
+{
+	static const struct i915_subtest tests[] = {
+		SUBTEST(igt_evict_contexts),
+	};
+
+	return i915_subtests(tests, i915);
+}
diff --git a/drivers/gpu/drm/i915/selftests/i915_live_selftests.h b/drivers/gpu/drm/i915/selftests/i915_live_selftests.h
index 64acd7eccc5c..54a73534b37e 100644
--- a/drivers/gpu/drm/i915/selftests/i915_live_selftests.h
+++ b/drivers/gpu/drm/i915/selftests/i915_live_selftests.h
@@ -15,6 +15,7 @@ selftest(objects, i915_gem_object_live_selftests)
 selftest(dmabuf, i915_gem_dmabuf_live_selftests)
 selftest(coherency, i915_gem_coherency_live_selftests)
 selftest(gtt, i915_gem_gtt_live_selftests)
+selftest(evict, i915_gem_evict_live_selftests)
 selftest(hugepages, i915_gem_huge_page_live_selftests)
 selftest(contexts, i915_gem_context_live_selftests)
 selftest(hangcheck, intel_hangcheck_live_selftests)
diff --git a/drivers/gpu/drm/i915/selftests/mock_context.c b/drivers/gpu/drm/i915/selftests/mock_context.c
index 098ce643ad07..bbf80d42e793 100644
--- a/drivers/gpu/drm/i915/selftests/mock_context.c
+++ b/drivers/gpu/drm/i915/selftests/mock_context.c
@@ -73,11 +73,7 @@ mock_context(struct drm_i915_private *i915,
 
 void mock_context_close(struct i915_gem_context *ctx)
 {
-	i915_gem_context_set_closed(ctx);
-
-	i915_ppgtt_close(&ctx->ppgtt->base);
-
-	i915_gem_context_put(ctx);
+	context_close(ctx);
 }
 
 void mock_init_contexts(struct drm_i915_private *i915)
-- 
2.15.0.rc0