On Wed, 22 Mar 2023 18:24:33 +0100 Halil Pasic <pa...@linux.ibm.com> wrote:
> > > --- a/hw/s390x/virtio-ccw.c > > > +++ b/hw/s390x/virtio-ccw.c > > > @@ -237,6 +237,7 @@ static int virtio_ccw_set_vqs(SubchDev *sch, > > > VqInfoBlock *info, > > > return -EINVAL; > > > } > > > virtio_queue_set_num(vdev, index, num); > > > + virtio_init_region_cache(vdev, index); > > > > Hmm... this is not wrong, but looking at it again, I see that the guest > > has no way to change num after our last call to > > virtio_init_region_cache() (while setting up the queue addresses.) IOW, > > this introduces an extra round trip that is not really needed. > > > > I don't quite understand. AFAIU the virtio_init_region_cache() would see > the (new) queue addresses but not the new size (num). Yes virtio-ccw > already knows the new num but it is yet to call > to put it into vdev->vq[n].vring.num from where > virtio_init_region_cache() picks it up. > > If we were to first virtio_queue_set_num() and only then the address > I would understand. But with the code as is, I don't. Am I missing > something? Connie: have you had a chance to have yet another look at this? I would like to understand the reason for seeing this differently. Regards, Halil
