On Wed, Oct 06, 2010 at 11:35:08AM -0500, Anthony Liguori wrote:
> On 10/06/2010 11:04 AM, Michael S. Tsirkin wrote:
> >With -netdev, virtio devices present offload
> >features to guest, depending on the backend used.
> >Thus, removing host netdev peer while guest is
> >active leads to guest-visible inconsistency and/or crashes.
> >
> >As a solution, while guest (NIC) peer device exists,
> >we 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 a shell of
> >the host device around for as long as guest device exists.
> >
> >The link is put down so all packets will get discarded.
> >
> >At the moment, management can detect that device deletion
> >is delayed by doing info net. As a next step, we shall add
> >commands that control hotplug/unplug without
> >removing the device, and an event to report that
> >guest has responded to the hotplug event.
> >
> >Signed-off-by: Michael S. Tsirkin<m...@redhat.com>
>
> I don't think this is a very good idea. Making netdev_del
> conditionally succeed is going to break management tools and is very
> non-intuitive.
>
> Regards,
>
> Anthony Liguori
But this is not what this does. With this patch netdev_del always
succeeds, and clears the device state leaving just an empty shell around.
The shell goes away together with the NIC.
> >---
> >
> > Changes from v3:
> > make sure ->cleanup is called for NICs
> > Changes from v2:
> > fix crash on repeated netdev_del
> >
> > net.c | 49 ++++++++++++++++++++++++++++++++++++++++++-------
> > net.h | 1 +
> > 2 files changed, 43 insertions(+), 7 deletions(-)
> >
> >diff --git a/net.c b/net.c
> >index 3d0fde7..ed74c7f 100644
> >--- a/net.c
> >+++ b/net.c
> >@@ -281,29 +281,64 @@ NICState *qemu_new_nic(NetClientInfo *info,
> > return nic;
> > }
> >
> >-void qemu_del_vlan_client(VLANClientState *vc)
> >+static void qemu_cleanup_vlan_client(VLANClientState *vc)
> > {
> > if (vc->vlan) {
> > QTAILQ_REMOVE(&vc->vlan->clients, vc, next);
> > } else {
> >- 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 (vc->info->cleanup) {
> > vc->info->cleanup(vc);
> > }
> >+}
> >
> >+static void qemu_free_vlan_client(VLANClientState *vc)
> >+{
> >+ if (!vc->vlan) {
> >+ if (vc->send_queue) {
> >+ qemu_del_net_queue(vc->send_queue);
> >+ }
> >+ if (vc->peer) {
> >+ vc->peer->peer = NULL;
> >+ }
> >+ }
> > qemu_free(vc->name);
> > qemu_free(vc->model);
> > qemu_free(vc);
> > }
> >
> >+void qemu_del_vlan_client(VLANClientState *vc)
> >+{
> >+ /* If there is a peer NIC, delete and cleanup client, but do not free.
> >*/
> >+ if (!vc->vlan&& vc->peer&& vc->peer->info->type ==
> >NET_CLIENT_TYPE_NIC) {
> >+ NICState *nic = DO_UPCAST(NICState, nc, vc->peer);
> >+ if (nic->peer_deleted) {
> >+ return;
> >+ }
> >+ nic->peer_deleted = true;
> >+ /* Let NIC know peer is gone. */
> >+ vc->peer->link_down = true;
> >+ if (vc->peer->info->link_status_changed) {
> >+ vc->peer->info->link_status_changed(vc->peer);
> >+ }
> >+ qemu_cleanup_vlan_client(vc);
> >+ return;
> >+ }
> >+
> >+ /* If this is a peer NIC and peer has already been deleted, free it
> >now. */
> >+ if (!vc->vlan&& vc->peer&& vc->info->type == NET_CLIENT_TYPE_NIC) {
> >+ NICState *nic = DO_UPCAST(NICState, nc, vc);
> >+ if (nic->peer_deleted) {
> >+ qemu_free_vlan_client(vc->peer);
> >+ }
> >+ }
> >+
> >+ qemu_cleanup_vlan_client(vc);
> >+ qemu_free_vlan_client(vc);
> >+}
> >+
> > VLANClientState *
> > qemu_find_vlan_client_by_name(Monitor *mon, int vlan_id,
> > const char *client_str)
> >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 {
