Bug#599161: xen-linux-system-2.6.32-5-xen-amd64: Clock moved forward 50 minutes, caused Xen HVM domU restart

Hello,

I can confirm that there are problems with the clock in PV domUs.

I've setups like as follows:
* Debian lenny dom0s running Debian squeeze and Debian lenny domUs (PV)
* Debian squeeze doms running Debian squeeze and Debian lenny domUs (PV)

I only have clock/time problems with my squeeze domUs. They use 2.6.32-5-amd64
and 2.6.32-5-686 kernels from Debian squeeze. It doesn't matter if they run on
lenny (2.6.26-*-xen-686) or squeeze (2.6.32-*-xen-686) dom0s.

With my Debian lenny dom0s I've set clocksource=jiffies and my lenny domUs
also have clocksource=jiffies and independent_wallclock set to 0. All is fine
here. I've running ntpd on the dom0s and the domUs use the time from the
dom0s. (I've tested to change the time in the dom0 and the time change also
show up in the domUs.) so I've no Problems with lenny domUs and time.

With debian squeeze there's no clocksource jiffies anymore, so I use the
default clocksource=xen in squeeze doms and squeeze domUs. Also there's no
independent_wallclock anymore.

So here's the problem I see: The time in my squeeze domUs is running slightly
slower than the time on my dom0. Changing the time on the dom0 doesn't change
the time in the squeeze domUs. But I can run ntpdate/ntp in my squeeze domUs
and time gets correct.

I'm wondering if I can set the former behavior of the domU clock to use the
dom0s clock?

On Sun, 2011-09-25 at 15:09 +0200, Markus Hochholdinger wrote:
> I can confirm that there are problems with the clock in PV domUs.

> I'm wondering if I can set the former behavior of the domU clock to use
> the dom0s clock?
I'm afraid that the old "dependent" wallclock mode is not available with
the upstream kernel so no. The current recommendation is to run ntpd in
your guests.