Re: [PATCH V2] virtio-pci: fix queue_enable write

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

On Wed, Jun 10, 2020 at 10:57:26AM +0200, Stefano Garzarella wrote:
> On Wed, Jun 10, 2020 at 01:43:51PM +0800, Jason Wang wrote:
> > Spec said: The driver uses this to selectively prevent the device from
> > executing requests from this virtqueue. 1 - enabled; 0 - disabled.
> > 
> > Though write 0 to queue_enable is forbidden by the spec, we should not
> > assume that the value is 1.
> > 
> > Fix this by ignore the write value other than 1.
> > 
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > ---
> > Changes from V1:
> > - fix typo
> > - warn wrong value through virtio_error
> > ---
> >  hw/virtio/virtio-pci.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> > 
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index d028c17c24..7bc8c1c056 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -1273,16 +1273,20 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
> >          virtio_queue_set_vector(vdev, vdev->queue_sel, val);
> >          break;
> >      case VIRTIO_PCI_COMMON_Q_ENABLE:
> > -        virtio_queue_set_num(vdev, vdev->queue_sel,
> > -                             proxy->vqs[vdev->queue_sel].num);
> > -        virtio_queue_set_rings(vdev, vdev->queue_sel,
> > +        if (val == 1) {
> 
> Does it have to be 1 or can it be any value other than 0?
> 
> Thanks,
> Stefano

spec says 1

> > +            virtio_queue_set_num(vdev, vdev->queue_sel,
> > +                                 proxy->vqs[vdev->queue_sel].num);
> > +            virtio_queue_set_rings(vdev, vdev->queue_sel,
> >                         ((uint64_t)proxy->vqs[vdev->queue_sel].desc[1]) << 32 |
> >                         proxy->vqs[vdev->queue_sel].desc[0],
> >                         ((uint64_t)proxy->vqs[vdev->queue_sel].avail[1]) << 32 |
> >                         proxy->vqs[vdev->queue_sel].avail[0],
> >                         ((uint64_t)proxy->vqs[vdev->queue_sel].used[1]) << 32 |
> >                         proxy->vqs[vdev->queue_sel].used[0]);
> > -        proxy->vqs[vdev->queue_sel].enabled = 1;
> > +            proxy->vqs[vdev->queue_sel].enabled = 1;
> > +        } else {
> > +            virtio_error(vdev, "wrong value for queue_enable %"PRIx64, val);
> > +        }
> >          break;
> >      case VIRTIO_PCI_COMMON_Q_DESCLO:
> >          proxy->vqs[vdev->queue_sel].desc[0] = val;
> > -- 
> > 2.20.1
> > 
> >