Merge branch 'net-2.6' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

drivers/vhost/vhost.c

@@ -1035,7 +1035,12 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
 /* This actually signals the guest, using eventfd. */
 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
 {
-	__u16 flags = 0;
+	__u16 flags;
+	/* Flush out used index updates. This is paired
+	 * with the barrier that the Guest executes when enabling
+	 * interrupts. */
+	smp_mb();
+
 	if (get_user(flags, &vq->avail->flags)) {
 		vq_err(vq, "Failed to get flags");
 		return;