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-rw-r--r--drivers/virtio/virtio_ring.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 99dc9480f3fe..36bb6a613728 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -251,9 +251,20 @@ add_head:
/* 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);