drm/i915/perf: Add preemption check while waiting for OA

While we're waiting for the OA configuration to apply, let's give a
chance to other contexts that might need to run other workloads.
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191114140224.21818-1-lionel.g.landwerlin@intel.com

drivers/gpu/drm/i915/i915_perf.c

@@ -1777,6 +1777,8 @@ static int alloc_noa_wait(struct i915_perf_stream *stream)
 	*cs++ = MI_MATH_ADD;
 	*cs++ = MI_MATH_STOREINV(MI_MATH_REG(JUMP_PREDICATE), MI_MATH_REG_CF);
 
+	*cs++ = MI_ARB_CHECK;
+
 	/*
 	 * Transfer the result into the predicate register to be used for the
 	 * predicated jump.