[Intel-gfx] [PATCH] drm/i915: Skip context_barrier emission for unused contexts

[Chris Wilson]

The intent was to skip unused HW contexts by checking ce->state.
However, this only works for execlists where the ppGTT pointers is
stored inside the HW context. For gen7, the ppGTT is alongside the
logical state and must be updated on all active engines but, crucially,
only on active engines. As we need different checks, and to keep
context_barrier_task() agnostic, pass in the predicate.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110836
Fixes: 62c8e423450d ("drm/i915: Skip unused contexts for context_barrier_task()")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c   | 15 ++++++++++++++-
 .../drm/i915/gem/selftests/i915_gem_context.c | 19 +++++++++++++++----
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 08721ef62e4e..6819b598d226 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -902,6 +902,7 @@ static void cb_retire(struct i915_active *base)
 I915_SELFTEST_DECLARE(static intel_engine_mask_t context_barrier_inject_fault);
 static int context_barrier_task(struct i915_gem_context *ctx,
 				intel_engine_mask_t engines,
+				bool (*skip)(struct intel_context *ce, void *data),
 				int (*emit)(struct i915_request *rq, void *data),
 				void (*task)(void *data),
 				void *data)
@@ -931,7 +932,10 @@ static int context_barrier_task(struct i915_gem_context *ctx,
 			break;
 		}
 
-		if (!(ce->engine->mask & engines) || !ce->state)
+		if (!(ce->engine->mask & engines))
+			continue;
+
+		if (skip && skip(ce, data))
 			continue;
 
 		rq = intel_context_create_request(ce);
@@ -1058,6 +1062,14 @@ static int emit_ppgtt_update(struct i915_request *rq, void *data)
 	return 0;
 }
 
+static bool skip_ppgtt_update(struct intel_context *ce, void *data)
+{
+	if (HAS_LOGICAL_RING_CONTEXTS(ce->engine->i915))
+		return !ce->state;
+	else
+		return !atomic_read(&ce->pin_count);
+}
+
 static int set_ppgtt(struct drm_i915_file_private *file_priv,
 		     struct i915_gem_context *ctx,
 		     struct drm_i915_gem_context_param *args)
@@ -1103,6 +1115,7 @@ static int set_ppgtt(struct drm_i915_file_private *file_priv,
 	 * only indirectly through the context.
 	 */
 	err = context_barrier_task(ctx, ALL_ENGINES,
+				   skip_ppgtt_update,
 				   emit_ppgtt_update,
 				   set_ppgtt_barrier,
 				   old);
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
index 1bc3b8026400..41105f6ed206 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
@@ -1619,6 +1619,11 @@ __engine_name(struct drm_i915_private *i915, intel_engine_mask_t engines)
 	return "none";
 }
 
+static bool skip_unused_engines(struct intel_context *ce, void *data)
+{
+	return !ce->state;
+}
+
 static void mock_barrier_task(void *data)
 {
 	unsigned int *counter = data;
@@ -1651,7 +1656,7 @@ static int mock_context_barrier(void *arg)
 
 	counter = 0;
 	err = context_barrier_task(ctx, 0,
-				   NULL, mock_barrier_task, &counter);
+				   NULL, NULL, mock_barrier_task, &counter);
 	if (err) {
 		pr_err("Failed at line %d, err=%d\n", __LINE__, err);
 		goto out;
@@ -1664,7 +1669,10 @@ static int mock_context_barrier(void *arg)
 
 	counter = 0;
 	err = context_barrier_task(ctx, ALL_ENGINES,
-				   NULL, mock_barrier_task, &counter);
+				   skip_unused_engines,
+				   NULL,
+				   mock_barrier_task,
+				   &counter);
 	if (err) {
 		pr_err("Failed at line %d, err=%d\n", __LINE__, err);
 		goto out;
@@ -1685,7 +1693,7 @@ static int mock_context_barrier(void *arg)
 	counter = 0;
 	context_barrier_inject_fault = BIT(RCS0);
 	err = context_barrier_task(ctx, ALL_ENGINES,
-				   NULL, mock_barrier_task, &counter);
+				   NULL, NULL, mock_barrier_task, &counter);
 	context_barrier_inject_fault = 0;
 	if (err == -ENXIO)
 		err = 0;
@@ -1700,7 +1708,10 @@ static int mock_context_barrier(void *arg)
 
 	counter = 0;
 	err = context_barrier_task(ctx, ALL_ENGINES,
-				   NULL, mock_barrier_task, &counter);
+				   skip_unused_engines,
+				   NULL,
+				   mock_barrier_task,
+				   &counter);
 	if (err) {
 		pr_err("Failed at line %d, err=%d\n", __LINE__, err);
 		goto out;
-- 
2.20.1