Re: [Qemu-devel] [PATCH] vhost: fix invalid downcast

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jul 13, 2018 at 05:04:05PM +0300, Yury Kotov wrote:
> virtio_queue_get_desc_addr returns 64-bit hwaddr while int is usually 32-bit.
> If returned hwaddr is not equal to 0 but least-significant 32 bits are
> equal to 0 then this code will not actually stop running queue.
> 
> Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>

So IIUC

Fixes: fb20fbb764aa1 ("vhost: avoid to start/stop virtqueue which is not ready")
And 
Cc: qemu-stable@nongnu.org

> ---
>  hw/virtio/vhost.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index b129cb9..7edeee7 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1071,10 +1071,8 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev,
>          .index = vhost_vq_index,
>      };
>      int r;
> -    int a;
>  
> -    a = virtio_queue_get_desc_addr(vdev, idx);
> -    if (a == 0) {
> +    if (virtio_queue_get_desc_addr(vdev, idx) == 0) {
>          /* Don't stop the virtqueue which might have not been started */
>          return;
>      }
> -- 
> 2.7.4