From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40513) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Yky2H-00049c-Jf for qemu-devel@nongnu.org; Wed, 22 Apr 2015 13:02:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Yky2C-0008Q3-SM for qemu-devel@nongnu.org; Wed, 22 Apr 2015 13:02:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40909) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Yky2C-0008PF-Ka for qemu-devel@nongnu.org; Wed, 22 Apr 2015 13:02:00 -0400 Date: Wed, 22 Apr 2015 18:01:56 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20150422170155.GE2386@work-vm> 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 * Daniel P. Berrange (berrange@redhat.com) 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. > > 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. I disagree; there should be a way for the admin not to have to do this manually; however it should interact well with existing management stuff. At the simplest, something that marks the two NICs in a discoverable way so that they can be seen that they're part of a set; with just that ID system then an installer or setup tool can notice them and offer to put them into a bond automatically; I'd assume it would be possible to add a rule somewhere that said anything with the same ID would automatically be added to the bond. However, I agree that you might be able to avoid having to do anything in the guest agent. Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK