From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44760) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WuYcU-0001pc-Pj for qemu-devel@nongnu.org; Tue, 10 Jun 2014 22:50:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WuYcO-0006NM-KN for qemu-devel@nongnu.org; Tue, 10 Jun 2014 22:50:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49826) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WuYcO-0006N4-7z for qemu-devel@nongnu.org; Tue, 10 Jun 2014 22:50:28 -0400 Message-ID: <5397C3DC.1010406@redhat.com> Date: Wed, 11 Jun 2014 10:50:04 +0800 From: Jason Wang MIME-Version: 1.0 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> In-Reply-To: <20140610101032.GJ7423@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit 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: "Michael S. Tsirkin" , Amit Shah Cc: Juan Quintela , qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , Liuyongan , aliguori@amazon.com, Amos Kong 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? >> >> >> Amit > Since we don't know guest addresses, this looks like the only way to me. > Yes and this method were also used by Xen and HyperV.