Re: [Qemu-devel] [PATCH 8/9] virtio: check for vring setup in virtio_queue_update_used_idx

[Philippe Mathieu-Daudé]

On 01/27/2017 12:40 PM, Paolo Bonzini wrote:
> If the vring has not been set up, it is not necessary for vring_used_idx
> to do anything (as is already the case when the caller is virtio_load).
> This is harmless for now, but it will be a problem when the
> MemoryRegionCache has not been set up.
>
> Signed-off-by: Paolo Bonzini <address@hidden>

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

> ---
>  hw/virtio/virtio.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 32bf364..23fac1e 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2154,7 +2154,9 @@ void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, 
> int n, uint16_t idx)
>
>  void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
>  {
> -    vdev->vq[n].used_idx = vring_used_idx(&vdev->vq[n]);
> +    if (vdev->vq[n].vring.desc) {
> +        vdev->vq[n].used_idx = vring_used_idx(&vdev->vq[n]);
> +    }
>  }
>
>  void virtio_queue_invalidate_signalled_used(VirtIODevice *vdev, int n)