On Tue, May 19, 2015 at 03:21:49PM +0100, Daniel P. Berrange 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:
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
On Fri, Apr 17, 2015 at 04:53:02PM +0800, Chen Fan wrote: 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
On Wed, Apr 22, 2015 at 10:23:04AM +0100, Daniel P. Berrange wrote: 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.
Using NM is up to users. On some of my VMs, I bring up links manually after each boot. We can provide the into to guest, and teach NM use that. If someone will write bash scripts to use this info, that's also fine.
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 :-)
Also note I'm not debating the usefulness of the overall concept or the need for automation. It simply doesn't belong in libvirt or lower - it is a job for the higher level management applications to define a policy for that fits in with the way they are managing the virtual machines and the networking.
Regards, Daniel
Users are asking for this automation, so it's useful to them. We can always tell them no. Saying no because we seem unable to be able to decide where this useful functionality fits does not look like a good reason.
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