From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48232) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YujEB-00070t-R7 for qemu-devel@nongnu.org; Tue, 19 May 2015 11:14:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YujE6-0006yd-2V for qemu-devel@nongnu.org; Tue, 19 May 2015 11:14:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46425) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YujE5-0006yU-RX for qemu-devel@nongnu.org; Tue, 19 May 2015 11:14:38 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t4JFEaK6032075 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Tue, 19 May 2015 11:14:36 -0400 Date: Tue, 19 May 2015 17:14:33 +0200 From: "Michael S. Tsirkin" Message-ID: <20150519171255-mutt-send-email-mst@redhat.com> References: <20150422092304.GE32086@redhat.com> <20150519110454-mutt-send-email-mst@redhat.com> <555B4575.1040709@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <555B4575.1040709@redhat.com> Subject: Re: [Qemu-devel] [libvirt] [RFC 0/7] Live Migration with Pass-through Devices proposal List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laine Stump Cc: libvir-list@redhat.com, qemu-devel@nongnu.org On Tue, May 19, 2015 at 10:15:17AM -0400, Laine Stump wrote: > On 05/19/2015 05:07 AM, Michael S. Tsirkin wrote: > > 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. > > That assumes the guest will have NM running. Unless you want to severely > limit the scope of usefulness, you also need to handle systems that have > NM disabled, and among those the different styles of system network > config. It gets messy very fast. Systems with system network config can just do the configuration manually, they won't be worse off than they are now. > > > > Users are actually asking for this functionality. > > > > Configuring everything manually is possible but error > > prone. > > Yes, but attempting to do it automatically is also error prone (due to > the myriad of different guest network config systems, even just within > the seemingly narrow category of "Linux guests"). Pick your poison :-) Make it work well for RHEL guests. Others will work with less integration. -- MST