diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 03874b50ada9..05f44ca35a06 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3703,6 +3703,9 @@ static int wait_for_engines(struct drm_i915_private *i915)
 
 int i915_gem_wait_for_idle(struct drm_i915_private *i915, unsigned int flags)
 {
+	GEM_TRACE("flags=%x (%s)\n",
+		  flags, flags & I915_WAIT_LOCKED ? "locked" : "unlocked");
+
 	/* If the device is asleep, we have no requests outstanding */
 	if (!READ_ONCE(i915->gt.awake))
 		return 0;
@@ -3719,6 +3722,7 @@ int i915_gem_wait_for_idle(struct drm_i915_private *i915, unsigned int flags)
 				return err;
 		}
 		i915_retire_requests(i915);
+		GEM_BUG_ON(i915->gt.active_requests);
 
 		return wait_for_engines(i915);
 	} else {
@@ -4901,6 +4905,7 @@ static void assert_kernel_context_is_current(struct drm_i915_private *i915)
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
 
+	GEM_BUG_ON(i915->gt.active_requests);
 	for_each_engine(engine, i915, id) {
 		GEM_BUG_ON(__i915_gem_active_peek(&engine->timeline.last_request));
 		GEM_BUG_ON(engine->last_retired_context->gem_context != kctx);
@@ -4932,6 +4937,8 @@ int i915_gem_suspend(struct drm_i915_private *dev_priv)
 	struct drm_device *dev = &dev_priv->drm;
 	int ret;
 
+	GEM_TRACE("\n");
+
 	intel_runtime_pm_get(dev_priv);
 	intel_suspend_gt_powersave(dev_priv);
 
diff --git a/drivers/gpu/drm/i915/i915_gem.h b/drivers/gpu/drm/i915/i915_gem.h
index 5bf24cfc218c..62ee4e385365 100644
--- a/drivers/gpu/drm/i915/i915_gem.h
+++ b/drivers/gpu/drm/i915/i915_gem.h
@@ -63,9 +63,12 @@ struct drm_i915_private;
 #if IS_ENABLED(CONFIG_DRM_I915_TRACE_GEM)
 #define GEM_TRACE(...) trace_printk(__VA_ARGS__)
 #define GEM_TRACE_DUMP() ftrace_dump(DUMP_ALL)
+#define GEM_TRACE_DUMP_ON(expr) \
+	do { if (expr) ftrace_dump(DUMP_ALL); } while (0)
 #else
 #define GEM_TRACE(...) do { } while (0)
 #define GEM_TRACE_DUMP() do { } while (0)
+#define GEM_TRACE_DUMP_ON(expr) BUILD_BUG_ON_INVALID(expr)
 #endif
 
 #define I915_NUM_ENGINES 8
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index b69b18ef8120..45393f6e0208 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -576,30 +576,72 @@ last_request_on_engine(struct i915_timeline *timeline,
 {
 	struct i915_request *rq;
 
-	if (timeline == &engine->timeline)
-		return NULL;
+	GEM_BUG_ON(timeline == &engine->timeline);
 
 	rq = i915_gem_active_raw(&timeline->last_request,
 				 &engine->i915->drm.struct_mutex);
-	if (rq && rq->engine == engine)
+	if (rq && rq->engine == engine) {
+		GEM_TRACE("last request for %s on engine %s: %llx:%d\n",
+			  timeline->name, engine->name,
+			  rq->fence.context, rq->fence.seqno);
+		GEM_BUG_ON(rq->timeline != timeline);
 		return rq;
+	}
 
 	return NULL;
 }
 
-static bool engine_has_idle_kernel_context(struct intel_engine_cs *engine)
+static bool engine_has_kernel_context_barrier(struct intel_engine_cs *engine)
 {
-	struct list_head * const active_rings = &engine->i915->gt.active_rings;
+	struct drm_i915_private *i915 = engine->i915;
+	const struct intel_context * const ce =
+		to_intel_context(i915->kernel_context, engine);
+	struct i915_timeline *barrier = ce->ring->timeline;
 	struct intel_ring *ring;
+	bool any_active = false;
 
-	lockdep_assert_held(&engine->i915->drm.struct_mutex);
+	lockdep_assert_held(&i915->drm.struct_mutex);
+	list_for_each_entry(ring, &i915->gt.active_rings, active_link) {
+		struct i915_request *rq;
+
+		rq = last_request_on_engine(ring->timeline, engine);
+		if (!rq)
+			continue;
 
-	list_for_each_entry(ring, active_rings, active_link) {
-		if (last_request_on_engine(ring->timeline, engine))
+		any_active = true;
+
+		if (rq->gem_context == i915->kernel_context)
+			continue;
+
+		/*
+		 * Was this request submitted after the previous
+		 * switch-to-kernel-context?
+		 */
+		if (!i915_timeline_sync_is_later(barrier, &rq->fence)) {
+			GEM_TRACE("%s needs barrier for %llx:%d\n",
+				  ring->timeline->name,
+				  rq->fence.context,
+				  rq->fence.seqno);
 			return false;
+		}
+
+		GEM_TRACE("%s has barrier after %llx:%d\n",
+			  ring->timeline->name,
+			  rq->fence.context,
+			  rq->fence.seqno);
 	}
 
-	return intel_engine_has_kernel_context(engine);
+	/*
+	 * If any other timeline was still active and behind the last barrier,
+	 * then our last switch-to-kernel-context must still be queued and
+	 * will run last (leaving the engine in the kernel context when it
+	 * eventually idles).
+	 */
+	if (any_active)
+		return true;
+
+	/* The engine is idle; check that it is idling in the kernel context. */
+	return engine->last_retired_context == ce;
 }
 
 int i915_gem_switch_to_kernel_context(struct drm_i915_private *i915)
@@ -607,7 +649,10 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *i915)
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
 
+	GEM_TRACE("\n");
+
 	lockdep_assert_held(&i915->drm.struct_mutex);
+	GEM_BUG_ON(!i915->kernel_context);
 
 	i915_retire_requests(i915);
 
@@ -615,9 +660,12 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *i915)
 		struct intel_ring *ring;
 		struct i915_request *rq;
 
-		if (engine_has_idle_kernel_context(engine))
+		GEM_BUG_ON(!to_intel_context(i915->kernel_context, engine));
+		if (engine_has_kernel_context_barrier(engine))
 			continue;
 
+		GEM_TRACE("emit barrier on %s\n", engine->name);
+
 		rq = i915_request_alloc(engine, i915->kernel_context);
 		if (IS_ERR(rq))
 			return PTR_ERR(rq);
@@ -627,10 +675,20 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *i915)
 			struct i915_request *prev;
 
 			prev = last_request_on_engine(ring->timeline, engine);
-			if (prev)
-				i915_sw_fence_await_sw_fence_gfp(&rq->submit,
-								 &prev->submit,
-								 I915_FENCE_GFP);
+			if (!prev)
+				continue;
+
+			if (prev->gem_context == i915->kernel_context)
+				continue;
+
+			GEM_TRACE("add barrier on %s for %llx:%d\n",
+				  engine->name,
+				  prev->fence.context,
+				  prev->fence.seqno);
+			i915_sw_fence_await_sw_fence_gfp(&rq->submit,
+							 &prev->submit,
+							 I915_FENCE_GFP);
+			i915_timeline_sync_set(rq->timeline, &prev->fence);
 		}
 
 		/*
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index fc499bcbd105..f187250e60c6 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -320,6 +320,7 @@ static void advance_ring(struct i915_request *request)
 		 * is just about to be. Either works, if we miss the last two
 		 * noops - they are safe to be replayed on a reset.
 		 */
+		GEM_TRACE("marking %s as inactive\n", ring->timeline->name);
 		tail = READ_ONCE(request->tail);
 		list_del(&ring->active_link);
 	} else {
@@ -1095,8 +1096,10 @@ void __i915_request_add(struct i915_request *request, bool flush_caches)
 	i915_gem_active_set(&timeline->last_request, request);
 
 	list_add_tail(&request->ring_link, &ring->request_list);
-	if (list_is_first(&request->ring_link, &ring->request_list))
+	if (list_is_first(&request->ring_link, &ring->request_list)) {
+		GEM_TRACE("marking %s as active\n", ring->timeline->name);
 		list_add(&ring->active_link, &request->i915->gt.active_rings);
+	}
 	request->emitted_jiffies = jiffies;
 
 	/*
diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/selftests/i915_gem_context.c
index ddb03f009232..98a33a8fb046 100644
--- a/drivers/gpu/drm/i915/selftests/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_context.c
@@ -26,6 +26,7 @@
 #include "igt_flush_test.h"
 
 #include "mock_drm.h"
+#include "mock_gem_device.h"
 #include "huge_gem_object.h"
 
 #define DW_PER_PAGE (PAGE_SIZE / sizeof(u32))
@@ -420,6 +421,130 @@ static int igt_ctx_exec(void *arg)
 	return err;
 }
 
+static const char *__engine_name(struct drm_i915_private *i915,
+				 unsigned int engines)
+{
+	struct intel_engine_cs *engine;
+	unsigned int tmp;
+
+	if (engines == ALL_ENGINES)
+		return "all";
+
+	for_each_engine_masked(engine, i915, engines, tmp)
+		return engine->name;
+
+	return "none";
+}
+
+static int __igt_switch_to_kernel_context(struct drm_i915_private *i915,
+					  struct i915_gem_context *ctx,
+					  unsigned int engines)
+{
+	struct intel_engine_cs *engine;
+	unsigned int tmp;
+	int err;
+
+	GEM_TRACE("Testing %s\n", __engine_name(i915, engines));
+	for_each_engine_masked(engine, i915, engines, tmp) {
+		struct i915_request *rq;
+
+		rq = i915_request_alloc(engine, ctx);
+		if (IS_ERR(rq))
+			return PTR_ERR(rq);
+
+		i915_request_add(rq);
+	}
+
+	err = i915_gem_switch_to_kernel_context(i915);
+	if (err)
+		return err;
+
+	for_each_engine_masked(engine, i915, engines, tmp) {
+		if (!engine_has_kernel_context_barrier(engine)) {
+			pr_err("kernel context not last on engine %s!\n",
+			       engine->name);
+			return -EINVAL;
+		}
+	}
+
+	err = i915_gem_wait_for_idle(i915, I915_WAIT_LOCKED);
+	if (err)
+		return err;
+
+	GEM_BUG_ON(i915->gt.active_requests);
+	for_each_engine_masked(engine, i915, engines, tmp) {
+		if (engine->last_retired_context->gem_context != i915->kernel_context) {
+			pr_err("engine %s not idling in kernel context!\n",
+			       engine->name);
+			return -EINVAL;
+		}
+	}
+
+	err = i915_gem_switch_to_kernel_context(i915);
+	if (err)
+		return err;
+
+	if (i915->gt.active_requests) {
+		pr_err("switch-to-kernel-context emitted %d requests even though it should already be idling in the kernel context\n",
+		       i915->gt.active_requests);
+		return -EINVAL;
+	}
+
+	for_each_engine_masked(engine, i915, engines, tmp) {
+		if (!intel_engine_has_kernel_context(engine)) {
+			pr_err("kernel context not last on engine %s!\n",
+			       engine->name);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static int igt_switch_to_kernel_context(void *arg)
+{
+	struct drm_i915_private *i915 = arg;
+	struct intel_engine_cs *engine;
+	struct i915_gem_context *ctx;
+	enum intel_engine_id id;
+	int err;
+
+	/*
+	 * A core premise of switching to the kernel context is that
+	 * if an engine is already idling in the kernel context, we
+	 * do not emit another request and wake it up. The other being
+	 * that we do indeed end up idling in the kernel context.
+	 */
+
+	mutex_lock(&i915->drm.struct_mutex);
+	ctx = kernel_context(i915);
+	if (IS_ERR(ctx)) {
+		err = PTR_ERR(ctx);
+		goto out_unlock;
+	}
+
+	/* First check idling each individual engine */
+	for_each_engine(engine, i915, id) {
+		err = __igt_switch_to_kernel_context(i915, ctx, BIT(id));
+		if (err)
+			goto out_unlock;
+	}
+
+	/* Now en masse */
+	err = __igt_switch_to_kernel_context(i915, ctx, ALL_ENGINES);
+	if (err)
+		goto out_unlock;
+
+out_unlock:
+	GEM_TRACE_DUMP_ON(err);
+	if (igt_flush_test(i915, I915_WAIT_LOCKED))
+		err = -EIO;
+	mutex_unlock(&i915->drm.struct_mutex);
+
+	kernel_context_close(ctx);
+	return err;
+}
+
 static int fake_aliasing_ppgtt_enable(struct drm_i915_private *i915)
 {
 	struct drm_i915_gem_object *obj;
@@ -447,9 +572,28 @@ static void fake_aliasing_ppgtt_disable(struct drm_i915_private *i915)
 	i915_gem_fini_aliasing_ppgtt(i915);
 }
 
+int i915_gem_context_mock_selftests(void)
+{
+	static const struct i915_subtest tests[] = {
+		SUBTEST(igt_switch_to_kernel_context),
+	};
+	struct drm_i915_private *i915;
+	int err;
+
+	i915 = mock_gem_device();
+	if (!i915)
+		return -ENOMEM;
+
+	err = i915_subtests(tests, i915);
+
+	drm_dev_unref(&i915->drm);
+	return err;
+}
+
 int i915_gem_context_live_selftests(struct drm_i915_private *dev_priv)
 {
 	static const struct i915_subtest tests[] = {
+		SUBTEST(igt_switch_to_kernel_context),
 		SUBTEST(igt_ctx_exec),
 	};
 	bool fake_alias = false;
diff --git a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
index d16d74178e9d..1b70208eeea7 100644
--- a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
+++ b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
@@ -24,3 +24,4 @@ selftest(vma, i915_vma_mock_selftests)
 selftest(evict, i915_gem_evict_mock_selftests)
 selftest(gtt, i915_gem_gtt_mock_selftests)
 selftest(hugepages, i915_gem_huge_page_mock_selftests)
+selftest(contexts, i915_gem_context_mock_selftests)
