Re: [Qemu-devel] [PATCH] virtio_error: don't invoke status callbacks

[Ilya Maximets]

On 13.12.2017 23:03, Michael S. Tsirkin wrote:
> Backends don't need to know what frontend requested a reset,
> and notifying then from virtio_error is messy because
> virtio_error itself might be invoked from backend.
> 
> Let's just set the status directly.
> 
> Reported-by: Ilya Maximets <address@hidden>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
> 
> Ilya this should fix the crash you are seeing
I tested it and it really fixes the QEMU crash.
Thanks. 

> but
> the error itself still shows there's something wrong.
> So I'd like to defer applying that patch until we
> figure out what corrupted guest index.
> 
> If you know pls let me know!

It looks like virtio driver crash caused by the same issue that was fixed in 
recent
patches from Maxime Coquelin:

  2ae39a113af3 ("vhost: restore avail index from vring used index on 
disconnection")
  2d4ba6cc741d ("virtio: Add queue interface to restore avail index from vring 
used index")

Applying above patches on top of 2.10.1 fixes virtio driver's crash.

> 
>  hw/virtio/virtio.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index ad564b0..d6002ee 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2469,7 +2469,7 @@ void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice 
> *vdev, const char *fmt, ...)
>      va_end(ap);
>  
>      if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
> -        virtio_set_status(vdev, vdev->status | VIRTIO_CONFIG_S_NEEDS_RESET);
> +        vdev->status = vdev->status | VIRTIO_CONFIG_S_NEEDS_RESET;
>          virtio_notify_config(vdev);
>      }
>  
>