Re: [PATCH] virtio-net: not enable vq reset feature unconditionally

[Michael S. Tsirkin]

On Sat, May 06, 2023 at 10:13:36AM +0800, Xuan Zhuo wrote:
> On Thu,  4 May 2023 12:14:47 +0200, =?utf-8?q?Eugenio_P=C3=A9rez?= 
> <eperezma@redhat.com> wrote:
> > The commit 93a97dc5200a ("virtio-net: enable vq reset feature") enables
> > unconditionally vq reset feature as long as the device is emulated.
> > This makes impossible to actually disable the feature, and it causes
> > migration problems from qemu version previous than 7.2.
> >
> > The entire final commit is unneeded as device system already enable or
> > disable the feature properly.
> >
> > This reverts commit 93a97dc5200a95e63b99cb625f20b7ae802ba413.
> > Fixes: 93a97dc5200a ("virtio-net: enable vq reset feature")
> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> >
> > ---
> > Tested by checking feature bit at  /sys/devices/pci.../virtio0/features
> > enabling and disabling queue_reset virtio-net feature and vhost=on/off
> > on net device backend.
> 
> Do you mean that this feature cannot be closed?
> 
> I tried to close in the guest, it was successful.
> 
> In addition, in this case, could you try to repair the problem instead of
> directly revert.
> 
> Thanks.

What does you patch accomplish though? If it's not needed
let's not do it.

> > ---
> >  hw/net/virtio-net.c | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> > index 53e1c32643..4ea33b6e2e 100644
> > --- a/hw/net/virtio-net.c
> > +++ b/hw/net/virtio-net.c
> > @@ -805,7 +805,6 @@ static uint64_t virtio_net_get_features(VirtIODevice 
> > *vdev, uint64_t features,
> >      }
> >
> >      if (!get_vhost_net(nc->peer)) {
> > -        virtio_add_feature(&features, VIRTIO_F_RING_RESET);
> >          return features;
> >      }
> >
> > --
> > 2.31.1
> >