On Mon, 2010-09-27 at 15:00 +0200, 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>
> ---
> net.c | 40 +++++++++++++++++++++++++++++++++-------
> net.h | 1 +
> 2 files changed, 34 insertions(+), 7 deletions(-)
>
> diff --git a/net.c b/net.c
> index 3d0fde7..edb87af 100644
> --- a/net.c
> +++ b/net.c
> @@ -281,29 +281,55 @@ NICState *qemu_new_nic(NetClientInfo *info,
> return nic;
> }
>
> -void qemu_del_vlan_client(VLANClientState *vc)
> +static void qemu_free_vlan_client(VLANClientState *vc)
> {
> if (vc->vlan) {
> QTAILQ_REMOVE(&vc->vlan->clients, vc, next);
> } else {
> + QTAILQ_REMOVE(&non_vlan_clients, vc, next);
> 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);
> - }
> -
> 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);
Are we potentially introducing more races here? Now we have the tap
trying to call link change on a peer device that's potentially in the
middle of going away. Thanks,
Alex
> + }
> + if (vc->info->cleanup) {
> + vc->info->cleanup(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_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 {
