Re: [Qemu-devel] [PATCH] dataplane: support viostor virtio-pci status bit setting

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

On Thu, Jan 17, 2013 at 04:46:54PM +0100, Stefan Hajnoczi wrote:
> The viostor virtio-blk driver for Windows does not use the
> VIRTIO_CONFIG_S_DRIVER bit.  It only sets the VIRTIO_CONFIG_S_DRIVER_OK
> bit.
> 
> The viostor driver refreshes the virtio-pci status byte sometimes while
> the guest is running.  We misinterpret 0x4 (VIRTIO_CONFIG_S_DRIVER_OK)
> as an indication that virtio-blk-data-plane should be stopped since 0x2
> (VIRTIO_CONFIG_S_DRIVER) is missing.  The result is that the device
> becomes unresponsive.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

I think you actually want

  if (s->dataplane && !(status & VIRTIO_CONFIG_S_DRIVER_OK)))

so stop on any error.

This is also consistent with what vhost-net does.


> ---
>  hw/virtio-blk.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
> index df57b35..34913ee 100644
> --- a/hw/virtio-blk.c
> +++ b/hw/virtio-blk.c
> @@ -571,7 +571,8 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
>      uint32_t features;
>  
>  #ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
> -    if (s->dataplane && !(status & VIRTIO_CONFIG_S_DRIVER)) {
> +    if (s->dataplane && !(status & (VIRTIO_CONFIG_S_DRIVER |
> +                                    VIRTIO_CONFIG_S_DRIVER_OK))) {
>          virtio_blk_data_plane_stop(s->dataplane);
>      }
>  #endif
> -- 
> 1.8.0.2