From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56621) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WvQiW-00019m-6d for qemu-devel@nongnu.org; Fri, 13 Jun 2014 08:36:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WvQiN-0001Fc-I3 for qemu-devel@nongnu.org; Fri, 13 Jun 2014 08:36:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:13086) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WvQiN-0001FW-83 for qemu-devel@nongnu.org; Fri, 13 Jun 2014 08:36:15 -0400 Date: Fri, 13 Jun 2014 18:05:50 +0530 From: Amit Shah Message-ID: <20140613123550.GD1071@grmbl.mre> References: <1400565704-11592-1-git-send-email-jasowang@redhat.com> <1400565704-11592-4-git-send-email-jasowang@redhat.com> <20140610062033.GG27148@grmbl.mre> <20140610101032.GJ7423@redhat.com> <5397C3DC.1010406@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5397C3DC.1010406@redhat.com> Subject: Re: [Qemu-devel] [PATCH V2 3/3] virtio-net: announce self by guest List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jason Wang Cc: Juan Quintela , "Michael S. Tsirkin" , qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , Liuyongan , aliguori@amazon.com, Amos Kong On (Wed) 11 Jun 2014 [10:50:04], Jason Wang wrote: > On 06/10/2014 06:10 PM, Michael S. Tsirkin wrote: > > On Tue, Jun 10, 2014 at 11:50:33AM +0530, Amit Shah wrote: > >> On (Tue) 20 May 2014 [14:01:44], Jason Wang wrote: > >>> It's hard to track all mac addresses and their configurations (e.g > >>> vlan or ipv6) in qemu. Without this information, it's impossible to > >>> build proper garp packet after migration. The only possible solution > >>> to this is let guest (who knows all configurations) to do this. > >>> > >>> So, this patch introduces a new readonly config status bit of virtio-net, > >>> VIRTIO_NET_S_ANNOUNCE which is used to notify guest to announce > >>> presence of its link through config update interrupt.When guest has > >>> done the announcement, it should ack the notification through > >>> VIRTIO_NET_CTRL_ANNOUNCE_ACK cmd. This feature is negotiated by a new > >>> feature bit VIRTIO_NET_F_ANNOUNCE (which has already been supported by > >>> Linux guest). > >>> > >>> During load, a counter of announcing rounds is set so that after the vm is > >>> running it can trigger rounds of config interrupts to notify the guest to build > >>> and send the correct garps. > >> Live migration is supposed to be transparent to guests. > >> > >> Doing things this way makes the guest involved in live migration. > >> It's not desirable. > > I'm not sure there's a problem. > > As long as guest doesn't use networking, it does not > > need to be involved. If guest does want to use networking, > > it needs to be involved, but then it's accessing the > > device anyway. > > > >> For networking, this may well be not possible. > >> Are there any ways of doing this w/o involving the guest that have > >> been considered? > >> > > Since we don't know guest addresses, this looks like the only way to me. I was afraid of that. > Yes and this method were also used by Xen and HyperV. Well there's precedent, but that didn't stop us from trying for something better in the past ;-) Amit