On Thu, Aug 18, 2016 at 8:27 PM, Roman Kagan <rka...@virtuozzo.com> wrote:
> The protocol for virtio-balloon stats virtqueue doesn't allow more than
> one element in the virtqueue.
>
> So, instead of trying to compensate for guest misbehavior if it sends
> new data before the slot has been released by the host, just define the
> stats virtqueue length to 1 initially and rely on the generic virtio
> code to handle overflows.
Looks good to me, one nit inline.
> Signed-off-by: Roman Kagan <rka...@virtuozzo.com>
> Cc: "Michael S. Tsirkin" <m...@redhat.com>
> Cc: Ladi Prosek <lpro...@redhat.com>
> ---
> hw/virtio/virtio-balloon.c | 9 +--------
> 1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index 5af429a..0baf4b3 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -262,13 +262,6 @@ static void virtio_balloon_receive_stats(VirtIODevice
> *vdev, VirtQueue *vq)
> goto out;
> }
>
> - if (s->stats_vq_elem != NULL) {
> - /* This should never happen if the driver follows the spec. */
> - virtqueue_push(vq, s->stats_vq_elem, 0);
> - virtio_notify(vdev, vq);
> - g_free(s->stats_vq_elem);
> - }
> -
Worth adding an assert?
assert(s->stats_vq_elem == NULL); // enforced by one-element stats virtqueue
> s->stats_vq_elem = elem;
>
> /* Initialize the stats to get rid of any stale values. This is only
> @@ -443,7 +436,7 @@ static void virtio_balloon_device_realize(DeviceState
> *dev, Error **errp)
>
> s->ivq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> - s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats);
> + s->svq = virtio_add_queue(vdev, 1, virtio_balloon_receive_stats);
>
> reset_stats(s);
> }
> --
> 2.7.4
>
