drm/i915/execlists: Disable preemption under GVT

Preempt-to-busy uses a GPU semaphore to enforce an idle-barrier across
preemption, but mediated gvt does not fully support semaphores.

v2: Fiddle around with the flags and settle on using has-semaphores for
the core bits so that we retain the ability to preempt our own
semaphores.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Xiaolin Zhang <xiaolin.zhang@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190709091233.8573-1-chris@chris-wilson.co.uk

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

@@ -829,6 +829,8 @@ int intel_engine_init_common(struct intel_engine_cs *engine)
 	struct drm_i915_private *i915 = engine->i915;
 	int ret;
 
+	engine->set_default_submission(engine);
+
 	/* We may need to do things with the shrinker which
 	 * require us to immediately switch back to the default
 	 * context. This can cause a problem as pinning the
@@ -847,8 +849,6 @@ int intel_engine_init_common(struct intel_engine_cs *engine)
 
 	engine->emit_fini_breadcrumb_dw = ret;
 
-	engine->set_default_submission(engine);
-
 	return 0;
 
 err_unpin:

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

@@ -306,6 +306,9 @@ static inline bool need_preempt(const struct intel_engine_cs *engine,
 {
 	int last_prio;
 
+	if (!intel_engine_has_semaphores(engine))
+		return false;
+
 	/*
 	 * Check if the current priority hint merits a preemption attempt.
 	 *
@@ -904,6 +907,9 @@ need_timeslice(struct intel_engine_cs *engine, const struct i915_request *rq)
 {
 	int hint;
 
+	if (!intel_engine_has_semaphores(engine))
+		return false;
+
 	if (list_is_last(&rq->sched.link, &engine->active.requests))
 		return false;
 
@@ -2656,7 +2662,8 @@ static u32 *gen8_emit_fini_breadcrumb(struct i915_request *request, u32 *cs)
 	*cs++ = MI_USER_INTERRUPT;
 
 	*cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
-	cs = emit_preempt_busywait(request, cs);
+	if (intel_engine_has_semaphores(request->engine))
+		cs = emit_preempt_busywait(request, cs);
 
 	request->tail = intel_ring_offset(request, cs);
 	assert_ring_tail_valid(request->ring, request->tail);
@@ -2680,7 +2687,8 @@ static u32 *gen8_emit_fini_breadcrumb_rcs(struct i915_request *request, u32 *cs)
 	*cs++ = MI_USER_INTERRUPT;
 
 	*cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
-	cs = emit_preempt_busywait(request, cs);
+	if (intel_engine_has_semaphores(request->engine))
+		cs = emit_preempt_busywait(request, cs);
 
 	request->tail = intel_ring_offset(request, cs);
 	assert_ring_tail_valid(request->ring, request->tail);
@@ -2728,10 +2736,11 @@ void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
 	engine->unpark = NULL;
 
 	engine->flags |= I915_ENGINE_SUPPORTS_STATS;
-	if (!intel_vgpu_active(engine->i915))
+	if (!intel_vgpu_active(engine->i915)) {
 		engine->flags |= I915_ENGINE_HAS_SEMAPHORES;
-	if (HAS_LOGICAL_RING_PREEMPTION(engine->i915))
-		engine->flags |= I915_ENGINE_HAS_PREEMPTION;
+		if (HAS_LOGICAL_RING_PREEMPTION(engine->i915))
+			engine->flags |= I915_ENGINE_HAS_PREEMPTION;
+	}
 }
 
 static void execlists_destroy(struct intel_engine_cs *engine)
@@ -3419,7 +3428,6 @@ intel_execlists_create_virtual(struct i915_gem_context *ctx,
 	ve->base.class = OTHER_CLASS;
 	ve->base.uabi_class = I915_ENGINE_CLASS_INVALID;
 	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
@@ -3516,8 +3524,12 @@ intel_execlists_create_virtual(struct i915_gem_context *ctx,
 		ve->base.emit_fini_breadcrumb = sibling->emit_fini_breadcrumb;
 		ve->base.emit_fini_breadcrumb_dw =
 			sibling->emit_fini_breadcrumb_dw;
+
+		ve->base.flags = sibling->flags;
 	}
 
+	ve->base.flags |= I915_ENGINE_IS_VIRTUAL;
+
 	return &ve->context;
 
 err_put:

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

@@ -269,6 +269,9 @@ static int live_timeslice_preempt(void *arg)
 		enum intel_engine_id id;
 
 		for_each_engine(engine, i915, id) {
+			if (!intel_engine_has_preemption(engine))
+				continue;
+
 			memset(vaddr, 0, PAGE_SIZE);
 
 			err = slice_semaphore_queue(engine, vma, count);
@@ -354,6 +357,9 @@ static int live_busywait_preempt(void *arg)
 		struct igt_live_test t;
 		u32 *cs;
 
+		if (!intel_engine_has_preemption(engine))
+			continue;
+
 		if (!intel_engine_can_store_dword(engine))
 			continue;