virtio-net: purge outstanding packets when starting vhost

whenever we start vhost, virtio could have outstanding packets queued, when they complete later we'll modify the ring while vhost is processing it. To prevent this, purge outstanding packets on vhost start. Cc: [email protected] Cc: Jason Wang <[email protected]> Signed-off-by: Michael S. Tsirkin <[email protected]> Signed-off-by: Stefan Hajnoczi <[email protected]>
damnya · Sep 4, 2014 · 086abc1 · 086abc1
1 parent ca77d85
commit 086abc1
Showing 1 changed file with 14 additions and 1 deletion.
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
@@ -125,10 +125,23 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
         return;
     }
     if (!n->vhost_started) {
-        int r;
+        int r, i;
+
         if (!vhost_net_query(get_vhost_net(nc->peer), vdev)) {
             return;
         }
+
+        /* Any packets outstanding? Purge them to avoid touching rings
+         * when vhost is running.
+         */
+        for (i = 0;  i < queues; i++) {
+            NetClientState *qnc = qemu_get_subqueue(n->nic, i);
+
+            /* Purge both directions: TX and RX. */
+            qemu_net_queue_purge(qnc->peer->incoming_queue, qnc);
+            qemu_net_queue_purge(qnc->incoming_queue, qnc->peer);
+        }
+
         n->vhost_started = 1;
         r = vhost_net_start(vdev, n->nic->ncs, queues);
         if (r < 0) {