Re: [PATCH 12/12] vdpa: fix network breakage after cancelling migration

[Michael Tokarev]

13.03.2024 21:12, Michael Tokarev пишет:
> 14.02.2024 14:28, Si-Wei Liu wrote:
> > Fix an issue where cancellation of ongoing migration ends up
> > with no network connectivity.
> >
> > When canceling migration, SVQ will be switched back to the
> > passthrough mode, but the right call fd is not programed to
> > the device and the svq's own call fd is still used. At the
> > point of this transitioning period, the shadow_vqs_enabled
> > hadn't been set back to false yet, causing the installation
> > of call fd inadvertently bypassed.
> >
> > Fixes: a8ac88585da1 ("vhost: Add Shadow VirtQueue call forwarding capabilities")
> > Cc: Eugenio Pérez <eperezma@redhat.com>
> > Acked-by: Jason Wang <jasowang@redhat.com>
> > Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> > ---
> >   hw/virtio/vhost-vdpa.c | 10 +++++++++-
> >   1 file changed, 9 insertions(+), 1 deletion(-)
>
> Is this a -stable material?
>
> If yes, is it also applicable for stable-7.2 (mentioned commit is in 7.2.0),
> which lacks v7.2.0-2327-gb276524386 "vdpa: Remember last call fd set",
> or should this one also be picked up?

Aha, this does not actually work without v8.2.0-171-gf6fe3e333f
"vdpa: move memory listener to vhost_vdpa_shared".

/mjt

> > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> > index 004110f..dfeca8b 100644
> > --- a/hw/virtio/vhost-vdpa.c
> > +++ b/hw/virtio/vhost-vdpa.c
> > @@ -1468,7 +1468,15 @@ static int vhost_vdpa_set_vring_call(struct vhost_dev 
> > *dev,
> >       /* Remember last call fd because we can switch to SVQ anytime. */
> >       vhost_svq_set_svq_call_fd(svq, file->fd);
> > -    if (v->shadow_vqs_enabled) {
> > +    /*
> > +     * When SVQ is transitioning to off, shadow_vqs_enabled has
> > +     * not been set back to false yet, but the underlying call fd
> > +     * will have to switch back to the guest notifier to signal the
> > +     * passthrough virtqueues. In other situations, SVQ's own call
> > +     * fd shall be used to signal the device model.
> > +     */
> > +    if (v->shadow_vqs_enabled &&
> > +        v->shared->svq_switching != SVQ_TSTATE_DISABLING) {
> >           return 0;
> >       }