From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43957) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YudVP-00077P-H7 for qemu-devel@nongnu.org; Tue, 19 May 2015 05:08:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YudVL-0006C8-Mj for qemu-devel@nongnu.org; Tue, 19 May 2015 05:08:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40693) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YudVL-0006Bg-Fl for qemu-devel@nongnu.org; Tue, 19 May 2015 05:08:03 -0400 Date: Tue, 19 May 2015 11:07:55 +0200 From: "Michael S. Tsirkin" Message-ID: <20150519110454-mutt-send-email-mst@redhat.com> References: <20150422092304.GE32086@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150422092304.GE32086@redhat.com> Subject: Re: [Qemu-devel] [RFC 0/7] Live Migration with Pass-through Devices proposal List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: Chen Fan , libvir-list@redhat.com, qemu-devel@nongnu.org, izumi.taku@jp.fujitsu.com On Wed, Apr 22, 2015 at 10:23:04AM +0100, Daniel P. Berrange wrote: > On Fri, Apr 17, 2015 at 04:53:02PM +0800, Chen Fan wrote: > > backgrond: > > Live migration is one of the most important features of virtualization technology. > > With regard to recent virtualization techniques, performance of network I/O is critical. > > Current network I/O virtualization (e.g. Para-virtualized I/O, VMDq) has a significant > > performance gap with native network I/O. Pass-through network devices have near > > native performance, however, they have thus far prevented live migration. No existing > > methods solve the problem of live migration with pass-through devices perfectly. > > > > There was an idea to solve the problem in website: > > https://www.kernel.org/doc/ols/2008/ols2008v2-pages-261-267.pdf > > Please refer to above document for detailed information. > > > > So I think this problem maybe could be solved by using the combination of existing > > technology. and the following steps are we considering to implement: > > > > - before boot VM, we anticipate to specify two NICs for creating bonding device > > (one plugged and one virtual NIC) in XML. here we can specify the NIC's mac addresses > > in XML, which could facilitate qemu-guest-agent to find the network interfaces in guest. > > > > - when qemu-guest-agent startup in guest it would send a notification to libvirt, > > then libvirt will call the previous registered initialize callbacks. so through > > the callback functions, we can create the bonding device according to the XML > > configuration. and here we use netcf tool which can facilitate to create bonding device > > easily. > > I'm not really clear on why libvirt/guest agent needs to be involved in this. > I think configuration of networking is really something that must be left to > the guest OS admin to control. I don't think the guest agent should be trying > to reconfigure guest networking itself, as that is inevitably going to conflict > with configuration attempted by things in the guest like NetworkManager or > systemd-networkd. There should not be a conflict. guest agent should just give NM the information, and have NM do the right thing. > IOW, if you want to do this setup where the guest is given multiple NICs connected > to the same host LAN, then I think we should just let the gues admin configure > bonding in whatever manner they decide is best for their OS install. > > > - during migration, unplug the passthroughed NIC. then do native migration. > > > > - on destination side, check whether need to hotplug new NIC according to specified XML. > > usually, we use migrate "--xml" command option to specify the destination host NIC mac > > address to hotplug a new NIC, because source side passthrough NIC mac address is different, > > then hotplug the deivce according to the destination XML configuration. > > Regards, > Daniel Users are actually asking for this functionality. Configuring everything manually is possible but error prone. We probably should leave manual configuration as an option for the 10% of people who want to tweak guest networking config, but this does not mean we shouldn't have it all work out of the box for 90% of people that just want networking to go fast with no tweaks. > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| > |: http://libvirt.org -o- http://virt-manager.org :| > |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|