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Re: [Xen-users] Clock (time) issue

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Clock (time) issue
From: Mark Adams <mark@xxxxxxxxxxxxxxxxxx>
Date: Mon, 4 Oct 2010 13:00:51 +0100
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On Mon, Oct 04, 2010 at 11:01:10AM +0100, Mark Adams wrote:
> Hi All,
> Im running Xen 4.0.1-rc6 Debian squeeze with pvops 2.6.32-21 kernel.
> Today I noticed (when kerberos to the domain controllers stopped
> working..) that the clock was 50 minutes out in dom0 -- This caused the
> HVM windows domain controllers to have the wrong time.
> I'm not sure if this is a kernel issue or a xen issue, but the only
> thing related is I can see the following in the kernel log:
> Oct  2 18:50:33 havhost1 kernel: [623480.977748] Clocksource tsc unstable 
> (delta = -2999660303788 ns)
> But I also see in the dmesg log that xen is using it's own clock.
> [    7.676563] Switching to clocksource xen
> I can't identify anything else in the logs to indicate when the time
> might have changed. I have a few other dom0 at the same level that
> haven't decided to change the time.
> Can anyone confirm whether xen controls the time or the kernel? Also
> when I corrected the time in dom0 it was still wrong in HVM domU -- How
> long does it take for this to propogate? (I rebooted the VM's to correct
> it immediately).
> Any other pointers on how to ensure stability of clocks from dom0 to
> domU HVM hosts (and pv for that matter..) would be appreciated.

Some further info on this, It appears the HVM domU (windows server 2008)
unexpectedly shut down at 18:51, after the unstable clocksource error.
qemu-dm logs show a reset "reset requested in cpu_handle_ioreq." and
xend.log shows a reboot 

[2010-10-02 18:51:03 1759] INFO (XendDomainInfo:2088) Domain has shutdown: 
name=ha-dc1 id=2 reason=reboot.

This is like someone issuing "xm reboot domain" is it not? Is it
possible that xen could have issued this reboot itself due to a crash? I
can't see any crash logs.


> Cheers,
> Mark 
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