Re: [RFC PATCH v2 6/8] vdpa: handle VIRTIO_NET_CTRL_ANNOUNCE in vhost_vdpa_net_handle_ctrl_avail

[Jason Wang]

On Thu, Oct 20, 2022 at 3:01 PM Eugenio Perez Martin
<eperezma@redhat.com> wrote:
>
> On Thu, Oct 20, 2022 at 6:35 AM Jason Wang <jasowang@redhat.com> wrote:
> >
> > On Wed, Oct 19, 2022 at 8:52 PM Eugenio Pérez <eperezma@redhat.com> wrote:
> > >
> > > Since this capability is emulated by qemu shadowed CVQ cannot forward it
> > > to the device.
> >
> > I wonder what happens for a device that has GUEST_ANNOUNCE support on its 
> > own?
> >
>
> If SVQ is enabled the feature is always emulated by qemu by this series.
>
> if SVQ is disabled then the device is the one in charge of all of it.

Ok, I see.

>
> > > Process all that command within qemu.
> > >
> > > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > > ---
> > >  net/vhost-vdpa.c | 15 ++++++++++++---
> > >  1 file changed, 12 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> > > index 3374c21b4d..5fda405a66 100644
> > > --- a/net/vhost-vdpa.c
> > > +++ b/net/vhost-vdpa.c
> > > @@ -488,9 +488,18 @@ static int 
> > > vhost_vdpa_net_handle_ctrl_avail(VhostShadowVirtqueue *svq,
> > >      out.iov_len = iov_to_buf(elem->out_sg, elem->out_num, 0,
> > >                               s->cvq_cmd_out_buffer,
> > >                               vhost_vdpa_net_cvq_cmd_len());
> > > -    dev_written = vhost_vdpa_net_cvq_add(s, out.iov_len, sizeof(status));
> > > -    if (unlikely(dev_written < 0)) {
> > > -        goto out;
> > > +    if (*(uint8_t *)s->cvq_cmd_out_buffer == VIRTIO_NET_CTRL_ANNOUNCE) {
> >
> > Interesting, I thought we can do better by forbidding the code that
> > goes into vhost-vDPA specific code, everything should be set at
> > virtio-net.c level.
> >
>
> Do you mean to move the SVQ processing to each handle_output? It's
> somehow on the roadmap but I'm not sure if it has more priority than
> implementing the different features.

Right, but I think we need to find a way to eliminate the casting here.

Thanks

>
> Thanks!
>
>
> > Thanks
> >
> > > +        /*
> > > +         * Guest announce capability is emulated by qemu, so dont 
> > > forward to
> > > +         * the device.
> > > +         */
> > > +        dev_written = sizeof(status);
> > > +        *s->status = VIRTIO_NET_OK;
> > > +    } else {
> > > +        dev_written = vhost_vdpa_net_cvq_add(s, out.iov_len, 
> > > sizeof(status));
> > > +        if (unlikely(dev_written < 0)) {
> > > +            goto out;
> > > +        }
> > >      }
> > >
> > >      if (unlikely(dev_written < sizeof(status))) {
> > > --
> > > 2.31.1
> > >
> >
>