Everybody know about these sweet line(s):

clocksource/0: Time went backwards: delta=-5802595381342 shadow=440273248432 offset=11586903

To prevent this, add this line to your sysctl.conf

xen.independent_wallclock=1

Next is, to add

extra="clocksource=jiffies"

to the config of your XEN domain (like /srv/xen/build.conf).

After all this, you can reboot the vm’s or to get it working for your current kernel config type this in each vm:

sysctl -p
echo "jiffies" > /sys/devices/system/clocksource/clocksource0/current_clocksource

At the moment i only know this from debian-based systems.