From 0bc76c8d0899f1f3a2bc5092ae9de7a900213a3b Mon Sep 17 00:00:00 2001 From: Maxime Coquelin Date: Thu, 16 Nov 2017 19:48:35 +0100 Subject: vhost: restore avail index from vring used index on disconnection vhost_virtqueue_stop() gets avail index value from the backend, except if the backend is not responding. It happens when the backend crashes, and in this case, internal state of the virtio queue is inconsistent, making packets to corrupt the vring state. With a Linux guest, it results in following error message on backend reconnection: [ 22.444905] virtio_net virtio0: output.0:id 0 is not a head! [ 22.446746] net enp0s3: Unexpected TXQ (0) queue failure: -5 [ 22.476360] net enp0s3: Unexpected TXQ (0) queue failure: -5 Fixes: 283e2c2adcb8 ("net: virtio-net discards TX data after link down") Cc: qemu-stable@nongnu.org Signed-off-by: Maxime Coquelin Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin (cherry picked from commit 2ae39a113af311cb56a0c35b7f212dafcef15303) Signed-off-by: Michael Roth --- hw/virtio/vhost.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index b737ca915b..76f6e1fcaa 100644 --- a/hw/virtio/vhost.c +++ b/hw/virtio/vhost.c @@ -1137,6 +1137,10 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev, r = dev->vhost_ops->vhost_get_vring_base(dev, &state); if (r < 0) { VHOST_OPS_DEBUG("vhost VQ %d ring restore failed: %d", idx, r); + /* Connection to the backend is broken, so let's sync internal + * last avail idx to the device used idx. + */ + virtio_queue_restore_last_avail_idx(vdev, idx); } else { virtio_queue_set_last_avail_idx(vdev, idx, state.num); } -- cgit v1.2.3