From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=33899 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1P0K9p-0001Tp-SY for qemu-devel@nongnu.org; Mon, 27 Sep 2010 16:18:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1P0K9o-0003NN-LC for qemu-devel@nongnu.org; Mon, 27 Sep 2010 16:18:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:16087) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1P0K9o-0003NH-Cp for qemu-devel@nongnu.org; Mon, 27 Sep 2010 16:18:40 -0400 From: Alex Williamson In-Reply-To: <20100927130004.GA8169@redhat.com> References: <20100927130004.GA8169@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Mon, 27 Sep 2010 14:18:37 -0600 Message-ID: <1285618717.4951.32.camel@x201> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH] net: delay freeing peer host device List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: qemu-devel@nongnu.org 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 > --- > 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 {