[libvirt-users] How to force the use of virtio as the guest network driver

I'm running KVM on a standard Debian Lenny host, and I seem to be hitting the problem identified here: http://serverfault.com/questions/123566/is-anyone-using-kvm-in-production My symptom is that using rsync over SSH to transfer files into the guest gets slower and slower, and then grinds to a halt, and the machine becomes unreachable. It seems that I should be using the virtio driver, but I can't seem to make it load. The KVM guest has the virtio module, (a la find /lib/modules -name \*virtio\*) but when I try to force it by setting <model type="virtio"/> in the XML configuration, it seems to make no difference. I see that as per http://libvirt.org/formatdomain.html , "qemu -net nic,model=? /dev/null" returns the following: "ne2k_isa i82551 i82557b i82559er ne2k_pci pcnet rtl8139", but I have no qemu-kvm binary. Not sure if that's a telling symptom or not. Host kernel is 2.6.26-2-openvz-amd64, KVM version is 72+dfsg-5~lenny5, libvirt version is 0.4.6-10, all of which look good enough to use virtio according to http://wiki.libvirt.org/page/Virtio . Thanks, Tony Lewis