drm/i915/gt: Disable arbitration on no-preempt requests

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@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210108204026.20682-7-chris@chris-wilson.co.uk

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;
 }
 

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);