drm/i915: Use same test for eviction and submitting kernel context

During evict, we wish to idle the GPU if we see that the GGTT is full.
However, our test for idle in i915_gem_evict_something() and in
i915_gem_switch_to_kernel_context() do not match leading to
disappointment - we never believe that we are idle and keep trying to
flush the GGTT ad infinitum.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103438
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171024220855.30155-2-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/i915_gem_context.c

@@ -897,7 +897,7 @@ int i915_switch_context(struct drm_i915_gem_request *req)
 	return do_rcs_switch(req);
 }
 
-static bool engine_has_kernel_context(struct intel_engine_cs *engine)
+static bool engine_has_idle_kernel_context(struct intel_engine_cs *engine)
 {
 	struct i915_gem_timeline *timeline;
 
@@ -913,8 +913,7 @@ static bool engine_has_kernel_context(struct intel_engine_cs *engine)
 			return false;
 	}
 
-	return (!engine->last_retired_context ||
-		i915_gem_context_is_kernel(engine->last_retired_context));
+	return intel_engine_has_kernel_context(engine);
 }
 
 int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
@@ -931,7 +930,7 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
 		struct drm_i915_gem_request *req;
 		int ret;
 
-		if (engine_has_kernel_context(engine))
+		if (engine_has_idle_kernel_context(engine))
 			continue;
 
 		req = i915_gem_request_alloc(engine, dev_priv->kernel_context);

drivers/gpu/drm/i915/i915_gem_evict.c

@@ -46,7 +46,7 @@ static bool ggtt_is_idle(struct drm_i915_private *i915)
 	       return false;
 
        for_each_engine(engine, i915, id) {
-	       if (engine->last_retired_context != i915->kernel_context)
+	       if (!intel_engine_has_kernel_context(engine))
 		       return false;
        }
 
@@ -73,6 +73,7 @@ static int ggtt_flush(struct drm_i915_private *i915)
 	if (err)
 		return err;
 
+	GEM_BUG_ON(!ggtt_is_idle(i915));
 	return 0;
 }
 

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -1585,6 +1585,12 @@ bool intel_engines_are_idle(struct drm_i915_private *dev_priv)
 	return true;
 }
 
+bool intel_engine_has_kernel_context(const struct intel_engine_cs *engine)
+{
+	return (!engine->last_retired_context ||
+		i915_gem_context_is_kernel(engine->last_retired_context));
+}
+
 void intel_engines_reset_default_submission(struct drm_i915_private *i915)
 {
 	struct intel_engine_cs *engine;

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -866,6 +866,8 @@ static inline u32 *gen8_emit_pipe_control(u32 *batch, u32 flags, u32 offset)
 bool intel_engine_is_idle(struct intel_engine_cs *engine);
 bool intel_engines_are_idle(struct drm_i915_private *dev_priv);
 
+bool intel_engine_has_kernel_context(const struct intel_engine_cs *engine);
+
 void intel_engines_mark_idle(struct drm_i915_private *i915);
 void intel_engines_reset_default_submission(struct drm_i915_private *i915);