diff --git a/hw/virtio-net.c b/hw/virtio-net.c index 6e48997c0e4aadafd35ef73783394afef29dbabd..5c0093e879df5dde1f94fef47efceb099cac427e 100644 --- a/hw/virtio-net.c +++ b/hw/virtio-net.c @@ -379,7 +379,15 @@ static int virtio_net_has_buffers(VirtIONet *n, int bufsize) (n->mergeable_rx_bufs && !virtqueue_avail_bytes(n->rx_vq, bufsize, 0))) { virtio_queue_set_notification(n->rx_vq, 1); - return 0; + + /* To avoid a race condition where the guest has made some buffers + * available after the above check but before notification was + * enabled, check for available buffers again. + */ + if (virtio_queue_empty(n->rx_vq) || + (n->mergeable_rx_bufs && + !virtqueue_avail_bytes(n->rx_vq, bufsize, 0))) + return 0; } virtio_queue_set_notification(n->rx_vq, 0);