Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6:
  vhost: fix barrier pairing

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index e69d238c5af0..49fa953aaf6e 100644
--- a/drivers/vhost/vhost.c
+++ b/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;