vhost: copy_from_user -> __copy_from_user

copy_from_user is pretty high on perf top profile,
replacing it with __copy_from_user helps.
It's also safe because we do access_ok checks during setup.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index b0cc7f8..2ab2912 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1171,7 +1171,7 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
                               i, vq->num, head);
                        return -EINVAL;
                }
-               ret = copy_from_user(&desc, vq->desc + i, sizeof desc);
+               ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
                if (unlikely(ret)) {
                        vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
                               i, vq->desc + i);