On Wed, Oct 27, 2010 at 02:59:16PM +0800, Jason Wang wrote:
> Michael S. Tsirkin writes:
> > On Wed, Oct 27, 2010 at 12:43:51AM +0800, Jason Wang wrote:
> > > When hot-unplug a virtio nic with vhost-net backend, guest may
> > > continue to program the nic even if its peer have been deleted. We can
> > > not set features at this time as vhost_net_ack_features() may still
> > > try to use the tap related vhost_net structure which have been freed
> > > in tap_cleanup(). And setting offload features for a deleted backend
> > > is also meaningless in this situation
> > >
> > > Signed-off-by: Jason Wang <jasow...@redhat.com>
> >
> > Hmm. Actually, this is not enough.
> > We really must stop and cleanup vhost net.
> >
>
> But this patch just prevent the guest from programming a nic with its
> vhost-net backend deleted. The vhost net was still stopped and cleaned
> when the peer have been removed.
No, I think it was cleanup but not stopped first. E.g. try to migrate at
this point and see it crash. I suspect we also leak fds for notifiers
and what not.
> > Two issues are
> > 1. vhost_net_stop needs virtio device pointer
> > 2. virtio net has a vhost_started flag
> >
> > Two ways to fix it that I see:
> > 1. add a callback in nic and invoke when peer_deleted is set
> > 2. add vhost_started and virtio device pointers in vhost
> >
> > Path 1 seems easier ...
> >
> > MST
> >
> > > ---
> > > hw/virtio-net.c | 3 +++
> > > 1 files changed, 3 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> > > index 7e1688c..68c8e48 100644
> > > --- a/hw/virtio-net.c
> > > +++ b/hw/virtio-net.c
> > > @@ -245,6 +245,9 @@ static void virtio_net_set_features(VirtIODevice
> *vdev, uint32_t features)
> > > {
> > > VirtIONet *n = to_virtio_net(vdev);
> > >
> > > + if (n->nic->peer_deleted)
> > > + return;
> > > +
> > > n->mergeable_rx_bufs = !!(features & (1 << VIRTIO_NET_F_MRG_RXBUF));
> > >
> > > if (n->has_vnet_hdr) {
> >
