[PATCH 1/2] drm/i915: Make bonded requests be alone in ELSP ports

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Mark bonded request pairs as single port submission to avoid potential
deadlocks due scheduling inversions.

Note that the master request is also marked as single port but potentially
already submitted in which case single port property will only apply after
subsequent preemption or time-slicing.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Suggested-by: Xiaogang Li <xiaogang.li at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_context.h |  2 +-
 drivers/gpu/drm/i915/gt/intel_lrc.c     | 28 +++++++++++++++++++------
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
index 07be021882cc..576d11c0cdd9 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.h
+++ b/drivers/gpu/drm/i915/gt/intel_context.h
@@ -212,7 +212,7 @@ intel_context_force_single_submission(const struct intel_context *ce)
 static inline void
 intel_context_set_single_submission(struct intel_context *ce)
 {
-	__set_bit(CONTEXT_FORCE_SINGLE_SUBMISSION, &ce->flags);
+	set_bit(CONTEXT_FORCE_SINGLE_SUBMISSION, &ce->flags);
 }
 
 static inline bool
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index de5be57ed6d2..3e367f6e4963 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1731,8 +1731,7 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
 
 static bool ctx_single_port_submission(const struct intel_context *ce)
 {
-	return (IS_ENABLED(CONFIG_DRM_I915_GVT) &&
-		intel_context_force_single_submission(ce));
+	return intel_context_force_single_submission(ce);
 }
 
 static bool can_merge_ctx(const struct intel_context *prev,
@@ -4926,9 +4925,23 @@ static void execlists_park(struct intel_engine_cs *engine)
 	cancel_timer(&engine->execlists.preempt);
 }
 
+static void
+mark_bonded_pair(struct i915_request *rq, struct i915_request *signal)
+{
+	intel_context_set_single_submission(rq->context);
+	intel_context_set_single_submission(signal->context);
+}
+
+static void
+execlists_bond_execute(struct i915_request *rq, struct dma_fence *signal)
+{
+	mark_bonded_pair(rq, to_request(signal));
+}
+
 void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
 {
 	engine->submit_request = execlists_submit_request;
+	engine->bond_execute = execlists_bond_execute;
 	engine->schedule = i915_schedule;
 	engine->execlists.tasklet.func = execlists_submission_tasklet;
 
@@ -5599,15 +5612,18 @@ virtual_find_bond(struct virtual_engine *ve,
 }
 
 static void
-virtual_bond_execute(struct i915_request *rq, struct dma_fence *signal)
+virtual_bond_execute(struct i915_request *rq, struct dma_fence *sigfence)
 {
 	struct virtual_engine *ve = to_virtual_engine(rq->engine);
+	struct i915_request *signal = to_request(sigfence);
 	intel_engine_mask_t allowed, exec;
 	struct ve_bond *bond;
 
-	allowed = ~to_request(signal)->engine->mask;
+	mark_bonded_pair(rq, signal);
+
+	allowed = ~signal->engine->mask;
 
-	bond = virtual_find_bond(ve, to_request(signal)->engine);
+	bond = virtual_find_bond(ve, signal->engine);
 	if (bond)
 		allowed &= bond->sibling_mask;
 
@@ -5617,7 +5633,7 @@ virtual_bond_execute(struct i915_request *rq, struct dma_fence *signal)
 		;
 
 	/* Prevent the master from being re-run on the bonded engines */
-	to_request(signal)->execution_mask &= ~allowed;
+	signal->execution_mask &= ~allowed;
 }
 
 struct intel_context *
-- 
2.20.1