I've seen very similar problem on our installation. Have you tried to run with kvm-clock explicitly disabled (either via no-kvmclock in guest kernel or with -kvm-clock in qemu) ?No, I haven't tried it yet (I've confirmed kvm-clock is currently being used). I'll have a look at it. Did it help your issue?
My results were inconclusive, but there way a guy two months ago who had the same problem and disabling kvm-clock resolved this for him.
I wonder if it'll help you as well. -- mg