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[PULL,3/7] vhost: restore avail index from vring used index on disconnection

Message ID 1512148088-28733-4-git-send-email-mst@redhat.com
State New
Headers show
Series [PULL,1/7] i386/msi: Correct mask of destination ID in MSI address | expand

Commit Message

Michael S. Tsirkin Dec. 1, 2017, 5:08 p.m. UTC 
From: Maxime Coquelin <maxime.coquelin@redhat.com>

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 <maxime.coquelin@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/vhost.c | 4 ++++
 1 file changed, 4 insertions(+)
diff mbox series

Patch

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index ddc42f0..5404194 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1138,6 +1138,10 @@  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);
     }