drm/i915/selftests: Serialise write to scratch with its vma binding

Add the missing serialisation on the request for a write into a vma to
wait until that vma is bound before being executed by the GPU.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191011193620.14026-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/selftest_workarounds.c

@@ -786,6 +786,14 @@ static int read_whitelisted_registers(struct i915_gem_context *ctx,
 	if (IS_ERR(rq))
 		return PTR_ERR(rq);
 
+	i915_vma_lock(results);
+	err = i915_request_await_object(rq, results->obj, true);
+	if (err == 0)
+		err = i915_vma_move_to_active(results, rq, EXEC_OBJECT_WRITE);
+	i915_vma_unlock(results);
+	if (err)
+		goto err_req;
+
 	srm = MI_STORE_REGISTER_MEM;
 	if (INTEL_GEN(ctx->i915) >= 8)
 		srm++;