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Date: Wed, 18 Mar 2015 14:08:56 +0100
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH V4 06/19] virtio-ccw: using
 VIRTIO_NO_VECTOR instead of 0 for invalid virtqueue
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To: Jason Wang <jasowang@redhat.com>
Cc: cornelia.huck@de.ibm.com, Christian Borntraeger <borntraeger@de.ibm.com>, Alexander Graf <agraf@suse.de>, qemu-devel@nongnu.org, Richard Henderson <rth@twiddle.net>

On Wed, Mar 18, 2015 at 05:34:56PM +0800, Jason Wang wrote:
> There's no need to use vector 0 for invalid virtqueue. So this patch
> changes to use VIRTIO_NO_VECTOR instead.
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> CC: Christian Borntraeger <borntraeger@de.ibm.com>
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Alexander Graf <agraf@suse.de>
> Signed-off-by: Jason Wang <jasowang@redhat.com>

I don't know what does this actually do.
Cornelia?

> ---
>  hw/s390x/virtio-ccw.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
> index 130535c..c8b87aa 100644
> --- a/hw/s390x/virtio-ccw.c
> +++ b/hw/s390x/virtio-ccw.c
> @@ -281,7 +281,7 @@ static int virtio_ccw_set_vqs(SubchDev *sch, uint64_t addr, uint32_t align,
>  
>      virtio_queue_set_addr(vdev, index, addr);
>      if (!addr) {
> -        virtio_queue_set_vector(vdev, index, 0);
> +        virtio_queue_set_vector(vdev, index, VIRTIO_NO_VECTOR);
>      } else {
>          /* Fail if we don't have a big enough queue. */
>          /* TODO: Add interface to handle vring.num changing */

Right below this, we have
    /* tell notify handler in case of config change */
    vdev->config_vector = VIRTIO_PCI_QUEUE_MAX;

which also does not seem to make sense.

These changes need some testing though.

> -- 
> 2.1.0