Re: [PATCH] virtio-net: failover: add missing remove_migration_state_change_notifier()

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Apr 27, 2021 at 03:02:34PM +0100, Dr. David Alan Gilbert wrote:
> * Laurent Vivier (lvivier@redhat.com) wrote:
> > In the failover case configuration, virtio_net_device_realize() uses an
> > add_migration_state_change_notifier() to add a state notifier, but this
> > notifier is not removed by the unrealize function when the virtio-net
> > card is unplugged.
> > 
> > If the card is unplugged and a migration is started, the notifier is
> > called and as it is not valid anymore QEMU crashes.
> > 
> > This patch fixes the problem by adding the
> > remove_migration_state_change_notifier() in virtio_net_device_unrealize().
> > 
> > The problem can be reproduced with:
> > 
> >   $ qemu-system-x86_64 -enable-kvm -m 1g -M q35 \
> >     -device pcie-root-port,slot=4,id=root1 \
> >     -device pcie-root-port,slot=5,id=root2 \
> >     -device virtio-net-pci,id=net1,mac=52:54:00:6f:55:cc,failover=on,bus=root1 \
> >     -monitor stdio disk.qcow2
> >   (qemu) device_del net1
> >   (qemu) migrate "exec:gzip -c > STATEFILE.gz"
> > 
> >   Thread 1 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
> >   0x0000000000000000 in ?? ()
> >   (gdb) bt
> >   #0  0x0000000000000000 in  ()
> >   #1  0x0000555555d726d7 in notifier_list_notify (...)
> >       at .../util/notify.c:39
> >   #2  0x0000555555842c1a in migrate_fd_connect (...)
> >       at .../migration/migration.c:3975
> >   #3  0x0000555555950f7d in migration_channel_connect (...)
> >       error@entry=0x0) at .../migration/channel.c:107
> >   #4  0x0000555555910922 in exec_start_outgoing_migration (...)
> >       at .../migration/exec.c:42
> > 
> > Reported-by: Igor Mammedov <imammedo@redhat.com>
> > Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> 
> Yep, I think that's OK.
> 
> 
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

net stuff so I expect Jason will merge this ...

> > ---
> >  hw/net/virtio-net.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> > index 66b9ff451185..914051feb75b 100644
> > --- a/hw/net/virtio-net.c
> > +++ b/hw/net/virtio-net.c
> > @@ -3373,6 +3373,7 @@ static void virtio_net_device_unrealize(DeviceState *dev)
> >  
> >      if (n->failover) {
> >          device_listener_unregister(&n->primary_listener);
> > +        remove_migration_state_change_notifier(&n->migration_state);
> >      }
> >  
> >      max_queues = n->multiqueue ? n->max_queues : 1;
> > -- 
> > 2.30.2
> > 
> -- 
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK