drm/i915: Remove has-kernel-context

We can no longer assume execution ordering, and in particular we cannot
assume which context will execute last. One side-effect of this is that
we cannot determine if the kernel-context is resident on the GPU, so
remove the routines that claimed to do so.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190308093657.8640-4-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_active.h

@@ -108,19 +108,6 @@ i915_active_request_set_retire_fn(struct i915_active_request *active,
 	active->retire = fn ?: i915_active_retire_noop;
 }
 
-static inline struct i915_request *
-__i915_active_request_peek(const struct i915_active_request *active)
-{
-	/*
-	 * Inside the error capture (running with the driver in an unknown
-	 * state), we want to bend the rules slightly (a lot).
-	 *
-	 * Work is in progress to make it safer, in the meantime this keeps
-	 * the known issue from spamming the logs.
-	 */
-	return rcu_dereference_protected(active->request, 1);
-}
-
 /**
  * i915_active_request_raw - return the active request
  * @active - the active tracker

drivers/gpu/drm/i915/i915_gem.c

@@ -2828,23 +2828,6 @@ i915_gem_retire_work_handler(struct work_struct *work)
 				   round_jiffies_up_relative(HZ));
 }
 
-static void assert_kernel_context_is_current(struct drm_i915_private *i915)
-{
-	struct intel_engine_cs *engine;
-	enum intel_engine_id id;
-
-	if (i915_reset_failed(i915))
-		return;
-
-	i915_retire_requests(i915);
-
-	for_each_engine(engine, i915, id) {
-		GEM_BUG_ON(__i915_active_request_peek(&engine->timeline.last_request));
-		GEM_BUG_ON(engine->last_retired_context !=
-			   to_intel_context(i915->kernel_context, engine));
-	}
-}
-
 static bool switch_to_kernel_context_sync(struct drm_i915_private *i915,
 					  unsigned long mask)
 {
@@ -2864,9 +2847,7 @@ static bool switch_to_kernel_context_sync(struct drm_i915_private *i915,
 				   I915_GEM_IDLE_TIMEOUT))
 		result = false;
 
-	if (result) {
-		assert_kernel_context_is_current(i915);
-	} else {
+	if (!result) {
 		/* Forcibly cancel outstanding work and leave the gpu quiet. */
 		dev_err(i915->drm.dev,
 			"Failed to idle engines, declaring wedged!\n");

drivers/gpu/drm/i915/i915_gem_evict.c

@@ -38,25 +38,15 @@ I915_SELFTEST_DECLARE(static struct igt_evict_ctl {
 
 static bool ggtt_is_idle(struct drm_i915_private *i915)
 {
-       struct intel_engine_cs *engine;
-       enum intel_engine_id id;
-
-       if (i915->gt.active_requests)
-	       return false;
-
-       for_each_engine(engine, i915, id) {
-	       if (!intel_engine_has_kernel_context(engine))
-		       return false;
-       }
-
-       return true;
+	return !i915->gt.active_requests;
 }
 
 static int ggtt_flush(struct drm_i915_private *i915)
 {
 	int err;
 
-	/* Not everything in the GGTT is tracked via vma (otherwise we
+	/*
+	 * Not everything in the GGTT is tracked via vma (otherwise we
 	 * could evict as required with minimal stalling) so we are forced
 	 * to idle the GPU and explicitly retire outstanding requests in
 	 * the hopes that we can then remove contexts and the like only

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -1090,37 +1090,6 @@ bool intel_engines_are_idle(struct drm_i915_private *i915)
 	return true;
 }
 
-/**
- * intel_engine_has_kernel_context:
- * @engine: the engine
- *
- * Returns true if the last context to be executed on this engine, or has been
- * executed if the engine is already idle, is the kernel context
- * (#i915.kernel_context).
- */
-bool intel_engine_has_kernel_context(const struct intel_engine_cs *engine)
-{
-	const struct intel_context *kernel_context =
-		to_intel_context(engine->i915->kernel_context, engine);
-	struct i915_request *rq;
-
-	lockdep_assert_held(&engine->i915->drm.struct_mutex);
-
-	if (!engine->context_size)
-		return true;
-
-	/*
-	 * Check the last context seen by the engine. If active, it will be
-	 * the last request that remains in the timeline. When idle, it is
-	 * the last executed context as tracked by retirement.
-	 */
-	rq = __i915_active_request_peek(&engine->timeline.last_request);
-	if (rq)
-		return rq->hw_context == kernel_context;
-	else
-		return engine->last_retired_context == kernel_context;
-}
-
 void intel_engines_reset_default_submission(struct drm_i915_private *i915)
 {
 	struct intel_engine_cs *engine;

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -935,7 +935,6 @@ void intel_engines_sanitize(struct drm_i915_private *i915, bool force);
 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_engine_lost_context(struct intel_engine_cs *engine);
 
 void intel_engines_park(struct drm_i915_private *i915);