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

[Stefano Garzarella]

On Wed, Jun 10, 2020 at 05:42:54AM -0400, Michael S. Tsirkin wrote:
> 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

I was confused by "The driver MUST NOT write a 0 to queue_enable.",
interpreting it as "can write anything other than 0".

But as Jason also wrote in the commit message, the driver should write
1 to enable, so

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

Thanks,
Stefano