[Intel-gfx] [PATCH v2] drm/i915/gt: Disable arbitration on no-preempt requests

[Chris Wilson]

If a request is submitted and known to require no preemption, disable
arbitration around the batch which prevents the HW from handling a
preemption request during the payload.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 6 +++---
 drivers/gpu/drm/i915/gt/gen8_engine_cs.c       | 3 +++
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 19eeb3f8c5e8..4f10fda829c4 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -2534,6 +2534,9 @@ static int eb_submit(struct i915_execbuffer *eb, struct i915_vma *batch)
 {
 	int err;
 
+	if (intel_context_nopreempt(eb->context))
+		__set_bit(I915_FENCE_FLAG_NOPREEMPT, &eb->request->fence.flags);
+
 	err = eb_move_to_gpu(eb);
 	if (err)
 		return err;
@@ -2574,9 +2577,6 @@ static int eb_submit(struct i915_execbuffer *eb, struct i915_vma *batch)
 			return err;
 	}
 
-	if (intel_context_nopreempt(eb->context))
-		__set_bit(I915_FENCE_FLAG_NOPREEMPT, &eb->request->fence.flags);
-
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/i915/gt/gen8_engine_cs.c b/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
index 1972dd5dca00..2e36e0a9d8a6 100644
--- a/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
@@ -427,6 +427,9 @@ int gen8_emit_bb_start(struct i915_request *rq,
 {
 	u32 *cs;
 
+	if (unlikely(i915_request_has_nopreempt(rq)))
+		return gen8_emit_bb_start_noarb(rq, offset, len, flags);
+
 	cs = intel_ring_begin(rq, 6);
 	if (IS_ERR(cs))
 		return PTR_ERR(cs);
-- 
2.20.1