[Intel-gfx] [PATCH v4] drm/i915/execlists: Disable preemption under GVT

[Chris Wilson]

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

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_engine_cs.c |  4 ++--
 drivers/gpu/drm/i915/gt/intel_lrc.c       | 21 ++++++++++++++++-----
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 4961f74fd902..d6fbc47727c1 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -830,6 +830,8 @@ 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
@@ -857,8 +859,6 @@ 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:
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index c8a0c9b32764..8017efb36f7b 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -294,6 +294,9 @@ static inline bool need_preempt(const struct intel_engine_cs *engine,
 {
 	int last_prio;
 
+	if (!intel_engine_has_preemption(engine))
+		return false;
+
 	/*
 	 * Check if the current priority hint merits a preemption attempt.
 	 *
@@ -890,6 +893,9 @@ need_timeslice(struct intel_engine_cs *engine, const struct i915_request *rq)
 {
 	int hint;
 
+	if (!intel_engine_has_preemption(engine))
+		return false;
+
 	if (list_is_last(&rq->sched.link, &engine->active.requests))
 		return false;
 
@@ -2600,7 +2606,8 @@ 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_preemption(request->engine))
+		cs = emit_preempt_busywait(request, cs);
 
 	request->tail = intel_ring_offset(request, cs);
 	assert_ring_tail_valid(request->ring, request->tail);
@@ -2624,7 +2631,8 @@ 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_preemption(request->engine))
+		cs = emit_preempt_busywait(request, cs);
 
 	request->tail = intel_ring_offset(request, cs);
 	assert_ring_tail_valid(request->ring, request->tail);
@@ -2672,10 +2680,11 @@ 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)
@@ -3463,6 +3472,8 @@ 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;
 	}
 
 	return &ve->context;
-- 
2.20.1