kvm linux guest hanging for minutes at a time

Thomas Fjellstrom
2011-08-07T14:13:57Z

Occasionally when there's heavy cpu and/or io load, a kvm guest will lock up
for minutes at a time, last occurrence was for about 12 minutes or so, and the
guest itself reported:

[1992982.639514] Clocksource tsc unstable (delta = -747307707123 ns)

in dmesg after it came back. The only other hint as to what is going on is
that the irq count for "local timer requests", virtio-input and virtio-
requests spikes rather high. Also one of the cpu cores on the host was pegged
the entire time.

The last thing to cause a hang was an "aptitude upgrade" in the guest, which
was a bit behind, so it had to update over 300 packages.

The host is running 2.6.38-1-amd64 (2.6.38+32) from debian, qemu-kvm 0.14.0,
and the guest was running 2.6.38-2-amd64 (not sure on the + number).

Is this a known problem, thats hopefully fixed in newer kernels and qemu/kvm
packages?

Thanks