Commit a72caae2 authored by Jason Wang's avatar Jason Wang Committed by Rusty Russell

virtio: correct the memory barrier in virtqueue_kick_prepare()

Use virtio_mb() to make sure the available index to be exposed before
checking the the avail event. Otherwise we may get stale value of
avail event in guest and never kick the host after.

Note: this fixes a bug introduced by ee7cd898.
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: stable@kernel.org
parent 4dbc5d9f
......@@ -308,9 +308,9 @@ bool virtqueue_kick_prepare(struct virtqueue *_vq)
bool needs_kick;
START_USE(vq);
/* Descriptors and available array need to be set before we expose the
* new available array entries. */
virtio_wmb(vq);
/* We need to expose available array entries before checking avail
* event. */
virtio_mb(vq);
old = vq->vring.avail->idx - vq->num_added;
new = vq->vring.avail->idx;
......
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