diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 99dc9480f3fe5cea635465198720d13b0798e7b6..36bb6a613728397309e64ca2031cbf96bb95cced 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -251,9 +251,20 @@ int virtqueue_add_buf(struct virtqueue *_vq,
 
 	/* Put entry in available array (but don't update avail->idx until they
 	 * do sync). */
-	avail = ((vq->vring.avail->idx + vq->num_added++) & (vq->vring.num-1));
+	avail = (vq->vring.avail->idx & (vq->vring.num-1));
 	vq->vring.avail->ring[avail] = head;
 
+	/* Descriptors and available array need to be set before we expose the
+	 * new available array entries. */
+	virtio_wmb(vq);
+	vq->vring.avail->idx++;
+	vq->num_added++;
+
+	/* This is very unlikely, but theoretically possible.  Kick
+	 * just in case. */
+	if (unlikely(vq->num_added == (1 << 16) - 1))
+		virtqueue_kick(_vq);
+
 	pr_debug("Added buffer head %i to %p\n", head, vq);
 	END_USE(vq);
 
@@ -283,13 +294,10 @@ bool virtqueue_kick_prepare(struct virtqueue *_vq)
 	 * new available array entries. */
 	virtio_wmb(vq);
 
-	old = vq->vring.avail->idx;
-	new = vq->vring.avail->idx = old + vq->num_added;
+	old = vq->vring.avail->idx - vq->num_added;
+	new = vq->vring.avail->idx;
 	vq->num_added = 0;
 
-	/* Need to update avail index before checking if we should notify */
-	virtio_mb(vq);
-
 	if (vq->event) {
 		needs_kick = vring_need_event(vring_avail_event(&vq->vring),
 					      new, old);