Is it possible to live migrate guest OS'es between different versions of kvm/qemu-kvm?

[Nils Cant <nils.cant@kangaroot.net>]

Hi,

I currently have a couple of Debian KVM servers with all a different 
version of kvm or qemu-kvm.

I can live migrate a guest OS from one server to the other just fine, as 
long as the version of qemu-kvm is the same. (Thanks to Gleb Natapov who 
helped me solve my ARP announce problem yesterday)

However, when I try to migrate a guest to a server running a newer (or 
older) version of qemu-kvm, I run into problems. I think this is because 
the xml configuration differs slightly between version.

For example, if I try to migrate from a server running qemu-kvm 0.11.0 
to one running qemu-kvm 0.12.4, I get the following error:

virt01:~# virsh migrate --live testserver qemu+ssh://192.168.1.7/system
error: internal error unable to reserve PCI address 0:0:3

When migrating from kvm 85 to qemu-kvm 0.11.0:

virt02:~# virsh migrate --live testserver qemu+ssh://192.168.1.2/system
error: Unknown failure

Migrating one from 0.12.4 to 0.11.0 just completely breaks libvirt, 
forcing me to kill -9 libvirtd and the kvm instance, etc.

I believe this is caused in part because different versions of qemu-kvm 
need different xml configurations. To run my testserver on 0.12.4 for 
example, I need to delete the lines with the PCI id's, just to be able 
to start the it.

So, is there a way to make this work? Perhaps without libvirt? Or tell 
libvirt to not send the config file when doing a live migrate, and use 
the xml in /etc/libvirt/qemu instead somehow?

Thanks in advance,

Nils