6 files changed, 21 insertions, 7 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index 42f45744d859..2c454f227c2e 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -142,7 +142,6 @@ intel_context_init(struct intel_context *ce,
 	ce->engine = engine;
 	ce->ops = engine->cops;
 	ce->sseu = engine->sseu;
-	ce->saturated = 0;
 
 	INIT_LIST_HEAD(&ce->signal_link);
 	INIT_LIST_HEAD(&ce->signals);
@@ -223,7 +222,6 @@ void intel_context_enter_engine(struct intel_context *ce)
 
 void intel_context_exit_engine(struct intel_context *ce)
 {
-	ce->saturated = 0;
 	intel_engine_pm_put(ce->engine);
 }
 
diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index e95be4be9612..08049ee91cee 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -53,8 +53,6 @@ struct intel_context {
 	atomic_t pin_count;
 	struct mutex pin_mutex; /* guards pinning and associated on-gpuing */
 
-	intel_engine_mask_t saturated; /* submitting semaphores too late? */
-
 	/**
 	 * active: Active tracker for the rq activity (inc. external) on this
 	 * intel_context object.
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
index d14e352b0b17..2ce00d3dc42a 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
@@ -100,6 +100,8 @@ static int __engine_park(struct intel_wakeref *wf)
 	struct intel_engine_cs *engine =
 		container_of(wf, typeof(*engine), wakeref);
 
+	engine->saturated = 0;
+
 	/*
 	 * If one and only one request is completed between pm events,
 	 * we know that we are inside the kernel context and it is
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
index b2faca8e5dec..868b220214f8 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
@@ -298,6 +298,8 @@ struct intel_engine_cs {
 	struct intel_context *kernel_context; /* pinned */
 	struct intel_context *preempt_context; /* pinned; optional */
 
+	intel_engine_mask_t saturated; /* submitting semaphores too late? */
+
 	unsigned long serial;
 
 	unsigned long wakeref_serial;
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index c400c66d0ee5..df58d1d838f7 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -3102,7 +3102,6 @@ static void virtual_context_exit(struct intel_context *ce)
 	struct virtual_engine *ve = container_of(ce, typeof(*ve), context);
 	unsigned int n;
 
-	ce->saturated = 0;
 	for (n = 0; n < ve->num_siblings; n++)
 		intel_engine_pm_put(ve->siblings[n]);
 }
@@ -3302,6 +3301,21 @@ intel_execlists_create_virtual(struct i915_gem_context *ctx,
 	ve->base.instance = I915_ENGINE_CLASS_INVALID_VIRTUAL;
 	ve->base.flags = I915_ENGINE_IS_VIRTUAL;
 
+	/*
+	 * The decision on whether to submit a request using semaphores
+	 * depends on the saturated state of the engine. We only compute
+	 * this during HW submission of the request, and we need for this
+	 * state to be globally applied to all requests being submitted
+	 * to this engine. Virtual engines encompass more than one physical
+	 * engine and so we cannot accurately tell in advance if one of those
+	 * engines is already saturated and so cannot afford to use a semaphore
+	 * and be pessimized in priority for doing so -- if we are the only
+	 * context using semaphores after all other clients have stopped, we
+	 * will be starved on the saturated system. Such a global switch for
+	 * semaphores is less than ideal, but alas is the current compromise.
+	 */
+	ve->base.saturated = ALL_ENGINES;
+
 	snprintf(ve->base.name, sizeof(ve->base.name), "virtual");
 
 	intel_engine_init_active(&ve->base, ENGINE_VIRTUAL);
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 7418e8f1ed6a..0c2b53b8a3d1 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -407,7 +407,7 @@ void __i915_request_submit(struct i915_request *request)
 	 */
 	if (request->sched.semaphores &&
 	    i915_sw_fence_signaled(&request->semaphore))
-		request->hw_context->saturated |= request->sched.semaphores;
+		engine->saturated |= request->sched.semaphores;
 
 	/* We may be recursing from the signal callback of another i915 fence */
 	spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING);
@@ -787,7 +787,7 @@ already_busywaiting(struct i915_request *rq)
 	 *
 	 * See the are-we-too-late? check in __i915_request_submit().
 	 */
-	return rq->sched.semaphores | rq->hw_context->saturated;
+	return rq->sched.semaphores | rq->engine->saturated;
 }
 
 static int