drm/i915/gt: Confirm the context survives execution

Repeat our sanitychecks from before execution to after execution. One
expects that if we were to see these, the gpu would already be on fire,
but the timing may be informative.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201015190816.31763-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_engine_pm.c

@@ -17,6 +17,25 @@
 #include "intel_ring.h"
 #include "shmem_utils.h"
 
+static void dbg_poison_ce(struct intel_context *ce)
+{
+	if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
+		return;
+
+	if (ce->state) {
+		struct drm_i915_gem_object *obj = ce->state->obj;
+		int type = i915_coherent_map_type(ce->engine->i915);
+		void *map;
+
+		map = i915_gem_object_pin_map(obj, type);
+		if (!IS_ERR(map)) {
+			memset(map, CONTEXT_REDZONE, obj->base.size);
+			i915_gem_object_flush_map(obj);
+			i915_gem_object_unpin_map(obj);
+		}
+	}
+}
+
 static int __engine_unpark(struct intel_wakeref *wf)
 {
 	struct intel_engine_cs *engine =
@@ -32,20 +51,14 @@ static int __engine_unpark(struct intel_wakeref *wf)
 	if (ce) {
 		GEM_BUG_ON(test_bit(CONTEXT_VALID_BIT, &ce->flags));
 
+		/* Flush all pending HW writes before we touch the context */
+		while (unlikely(intel_context_inflight(ce)))
+			intel_engine_flush_submission(engine);
+
 		/* First poison the image to verify we never fully trust it */
-		if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM) && ce->state) {
-			struct drm_i915_gem_object *obj = ce->state->obj;
-			int type = i915_coherent_map_type(engine->i915);
-			void *map;
-
-			map = i915_gem_object_pin_map(obj, type);
-			if (!IS_ERR(map)) {
-				memset(map, CONTEXT_REDZONE, obj->base.size);
-				i915_gem_object_flush_map(obj);
-				i915_gem_object_unpin_map(obj);
-			}
-		}
+		dbg_poison_ce(ce);
 
+		/* Scrub the context image after our loss of control */
 		ce->ops->reset(ce);
 	}
 

drivers/gpu/drm/i915/gt/intel_lrc.c

@@ -1215,7 +1215,8 @@ static void intel_engine_context_out(struct intel_engine_cs *engine)
 
 static void
 execlists_check_context(const struct intel_context *ce,
-			const struct intel_engine_cs *engine)
+			const struct intel_engine_cs *engine,
+			const char *when)
 {
 	const struct intel_ring *ring = ce->ring;
 	u32 *regs = ce->lrc_reg_state;
@@ -1250,7 +1251,7 @@ execlists_check_context(const struct intel_context *ce,
 		valid = false;
 	}
 
-	WARN_ONCE(!valid, "Invalid lrc state found before submission\n");
+	WARN_ONCE(!valid, "Invalid lrc state found %s submission\n", when);
 }
 
 static void restore_default_state(struct intel_context *ce,
@@ -1346,7 +1347,7 @@ __execlists_schedule_in(struct i915_request *rq)
 		reset_active(rq, engine);
 
 	if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
-		execlists_check_context(ce, engine);
+		execlists_check_context(ce, engine, "before");
 
 	if (ce->tag) {
 		/* Use a fixed tag for OA and friends */
@@ -1417,6 +1418,9 @@ __execlists_schedule_out(struct i915_request *rq,
 	 * refrain from doing non-trivial work here.
 	 */
 
+	if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
+		execlists_check_context(ce, engine, "after");
+
 	/*
 	 * If we have just completed this context, the engine may now be
 	 * idle and we want to re-enter powersaving.
@@ -4080,6 +4084,8 @@ static void reset_csb_pointers(struct intel_engine_cs *engine)
 
 static void execlists_sanitize(struct intel_engine_cs *engine)
 {
+	GEM_BUG_ON(execlists_active(&engine->execlists));
+
 	/*
 	 * Poison residual state on resume, in case the suspend didn't!
 	 *