[PATCH] drm/i915/selftests: Check the context size

[Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>]

Add a redzone to our context image and check the HW does not write into
after a context save, to verify that we have the correct context size.
(This does vary with feature bits, so test with a live setup that should
match how we run userspace.)

Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/selftest_context.c | 133 +++++++++++++++++++++
 1 file changed, 133 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/selftest_context.c b/drivers/gpu/drm/i915/gt/selftest_context.c
index 6fbc72bc290e..69f2233104f1 100644
--- a/drivers/gpu/drm/i915/gt/selftest_context.c
+++ b/drivers/gpu/drm/i915/gt/selftest_context.c
@@ -5,6 +5,7 @@
  */
 
 #include "i915_selftest.h"
+#include "intel_engine_pm.h"
 #include "intel_gt.h"
 
 #include "gem/selftests/mock_context.h"
@@ -64,6 +65,137 @@ static int context_sync(struct intel_context *ce)
 	return err;
 }
 
+static int __live_context_size(struct intel_engine_cs *engine,
+			       struct i915_gem_context *fixme)
+{
+	struct intel_context *ce;
+	struct i915_request *rq;
+	void *vaddr;
+	int err;
+
+	ce = intel_context_create(fixme, engine);
+	if (IS_ERR(ce))
+		return PTR_ERR(ce);
+
+	err = intel_context_pin(ce);
+	if (err)
+		goto err;
+
+	vaddr = i915_gem_object_pin_map(ce->state->obj,
+					i915_coherent_map_type(engine->i915));
+	if (IS_ERR(vaddr)) {
+		err = PTR_ERR(vaddr);
+		intel_context_unpin(ce);
+		goto err;
+	}
+
+	if (HAS_EXECLISTS(engine->i915))
+		vaddr += LRC_HEADER_PAGES * PAGE_SIZE;
+
+	vaddr += engine->context_size - I915_GTT_PAGE_SIZE;
+	memset(vaddr, POISON_INUSE, I915_GTT_PAGE_SIZE);
+
+	rq = intel_context_create_request(ce);
+	intel_context_unpin(ce);
+	if (IS_ERR(rq)) {
+		err = PTR_ERR(rq);
+		goto err_unpin;
+	}
+
+	err = request_sync(rq);
+	if (err)
+		goto err_unpin;
+
+	/* Force the context switch */
+	rq = i915_request_create(engine->kernel_context);
+	if (IS_ERR(rq)) {
+		err = PTR_ERR(rq);
+		goto err_unpin;
+	}
+	err = request_sync(rq);
+	if (err)
+		goto err_unpin;
+
+	if (memchr_inv(vaddr, POISON_INUSE, I915_GTT_PAGE_SIZE)) {
+		pr_err("%s context overwrote trailing red-zone!", engine->name);
+		err = -EINVAL;
+	}
+
+err_unpin:
+	i915_gem_object_unpin_map(ce->state->obj);
+err:
+	intel_context_put(ce);
+	return err;
+}
+
+static int live_context_size(void *arg)
+{
+	struct intel_gt *gt = arg;
+	struct intel_engine_cs *engine;
+	struct i915_gem_context *fixme;
+	enum intel_engine_id id;
+	struct drm_file *file;
+	int err = 0;
+
+	/*
+	 * Check that are context sizes are correct by seeing if the
+	 * HW tries to write past the end of one.
+	 */
+
+	file = mock_file(gt->i915);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	mutex_lock(&gt->i915->drm.struct_mutex);
+
+	fixme = live_context(gt->i915, file);
+	if (IS_ERR(fixme)) {
+		err = PTR_ERR(fixme);
+		goto unlock;
+	}
+
+	for_each_engine(engine, gt->i915, id) {
+		struct {
+			struct drm_i915_gem_object *state;
+			void *pinned;
+		} saved;
+
+		if (!engine->context_size)
+			continue;
+
+		intel_engine_pm_get(engine);
+
+		/*
+		 * Hide the old default state -- we lie about the context size
+		 * and get confused when the default state is smaller than
+		 * expected. For our do nothing request, inheriting the
+		 * active state is sufficient, we are only checking that we
+		 * don't use more than we planned.
+		 */
+		saved.state = fetch_and_zero(&engine->default_state);
+		saved.pinned = fetch_and_zero(&engine->pinned_default_state);
+
+		engine->context_size += I915_GTT_PAGE_SIZE;
+
+		err = __live_context_size(engine, fixme);
+
+		engine->context_size -= I915_GTT_PAGE_SIZE;
+
+		engine->pinned_default_state = saved.pinned;
+		engine->default_state = saved.state;
+
+		intel_engine_pm_put(engine);
+
+		if (err)
+			break;
+	}
+
+unlock:
+	mutex_unlock(&gt->i915->drm.struct_mutex);
+	mock_file_free(gt->i915, file);
+	return err;
+}
+
 static int __live_active_context(struct intel_engine_cs *engine,
 				 struct i915_gem_context *fixme)
 {
@@ -303,6 +435,7 @@ static int live_remote_context(void *arg)
 int intel_context_live_selftests(struct drm_i915_private *i915)
 {
 	static const struct i915_subtest tests[] = {
+		SUBTEST(live_context_size),
 		SUBTEST(live_active_context),
 		SUBTEST(live_remote_context),
 	};
-- 
2.23.0.rc1

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