On Tue, May 19, 2015 at 04:03:04PM +0100, Dr. David Alan Gilbert wrote: > * Daniel P. Berrange (berrange@xxxxxxxxxx) wrote: > > 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. > > > > Also OpenStack already has a way to pass guest information about the > > required network setup, via cloud-init, so it would not be interested > > in any thing that used the QEMU guest agent to configure network > > manager. Which is really just another example of why this does not > > belong anywhere in libvirt or lower. The decision to use NM is a > > policy decision that will always be wrong for a non-negligble set > > of use cases and as such does not belong in libvirt or QEMU. It is > > the job of higher level apps to make that kind of policy decision. > > This is exactly my worry though; why should every higher level management > system have it's own way of communicating network config for hotpluggable > devices. You shoudln't need to reconfigure a VM to move it between them. > > This just makes it hard to move it between management layers; there needs > to be some standardisation (or abstraction) of this; if libvirt isn't the place > to do it, then what is? NB, openstack isn't really defining a custom thing for networking here. It is actually integrating with the standard cloud-init guest tools for this task. Also note that OpenStack has defined a mechanism that works for guest images regardless of what hypervisor they are running on - ie does not rely on any QEMU or libvirt specific functionality here. Regards, Daniel -- |: 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 :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list