On Mon, Sep 20, 2010 at 11:41:45AM -0500, Anthony Liguori wrote:
> On 09/20/2010 11:30 AM, Michael S. Tsirkin wrote:
> >With -netdev, virtio devices present offload
> >features to guest, depending on the backend used.
> >Thus, removing host ntedev peer while guest is
> >active leads to guest-visible inconsistency and/or crashes.
> >See e.g. https://bugzilla.redhat.com/show_bug.cgi?id=623735
> >
> >As a solution, while guest (NIC) peer device exists,
> >we must prevent the host peer from being deleted.
> >
> >This patch does this by adding peer_deleted flag in nic state:
> >if host device is going away while guest device
> >is around, set this flag and keep host device around
> >for as long as guest device exists.
>
> Having an unclear life cycle really worries me.
>
> Wouldn't the more correct solution be to avoid removing the netdev
> device until after the peer has successfully been removed?
>
> Regards,
>
> Anthony Liguori
This is exactly what the patch does.
> >Signed-off-by: Michael S. Tsirkin<m...@redhat.com>
> >---
> > net.c | 21 ++++++++++++++++++++-
> > net.h | 1 +
> > 2 files changed, 21 insertions(+), 1 deletions(-)
> >
> >diff --git a/net.c b/net.c
> >index 3d0fde7..10855d1 100644
> >--- a/net.c
> >+++ b/net.c
> >@@ -286,12 +286,31 @@ void qemu_del_vlan_client(VLANClientState *vc)
> > if (vc->vlan) {
> > QTAILQ_REMOVE(&vc->vlan->clients, vc, next);
> > } else {
> >+ /* Even if client will not be deleted yet, remove it from list so it
> >+ * does not appear in monitor. */
> >+ QTAILQ_REMOVE(&non_vlan_clients, vc, next);
> >+ /* Detect that guest-visible (NIC) peer is active, and delay
> >deletion.
> >+ * */
> >+ if (vc->peer&& vc->peer->info->type == NET_CLIENT_TYPE_NIC) {
> >+ NICState *nic = DO_UPCAST(NICState, nc, vc->peer);
> >+ assert(!nic->peer_deleted);
> >+ nic->peer_deleted = true;
> >+ return;
> >+ }
> > if (vc->send_queue) {
> > qemu_del_net_queue(vc->send_queue);
> > }
> >- QTAILQ_REMOVE(&non_vlan_clients, vc, next);
> > if (vc->peer) {
> > vc->peer->peer = NULL;
> >+ /* If this is a guest-visible (NIC) device,
> >+ * and peer has already been removed from monitor,
> >+ * delete it here. */
> >+ if (vc->info->type == NET_CLIENT_TYPE_NIC) {
> >+ NICState *nic = DO_UPCAST(NICState, nc, vc);
> >+ if (nic->peer_deleted) {
> >+ qemu_del_vlan_client(vc->peer);
> >+ }
> >+ }
> > }
> > }
> >
> >diff --git a/net.h b/net.h
> >index 518cf9c..44c31a9 100644
> >--- a/net.h
> >+++ b/net.h
> >@@ -72,6 +72,7 @@ typedef struct NICState {
> > VLANClientState nc;
> > NICConf *conf;
> > void *opaque;
> >+ bool peer_deleted;
> > } NICState;
> >
> > struct VLANState {
