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[Philipp Hahn]

Am 25.03.2016 um 06:52 schrieb Tim Streit:
> Im having problems with my install.  Debian Jessie (8.3), but using libvirt and kernel from back ports (for enhanced vt-d support, passing through a USB card).  Guest is a windows xp sp3 box.  Initially I had hardware time set to UTC, and I set the RealTimeIsUtc=1 in the registry.  But it would periodically reset itself ahead 6 hours (CST), and since we just changed day light savings time now its jumping 5 hours.  Every morning.   I have a similarly configured system running a win7 guest, time works fine.
> 
> Someone on #kvm suggested that maybe I need to set my hwclock to local time, and so I went through all that - changed it, appended LOCAL to  /etc/adjtime etc. I then changed the RealTimeIsUtc=0, and for the first boot it seemed okay.
> 
> Now, whenever I boot, it is constantly 5 hours ahead.  I can reset it but when you reboot, its back.

Tell libvirt to give your VM a RTC with
  <clock offset='variable' basis='utc' adjustment='-18000'/>

That way your VM will have a RTC 5h behind UTC and Windows is free to
adjust the offset as it likes when the day-light saving occurs. When
that happens the "adjustment" changes and libvirt will persist that in
the XML.

See <https://libvirt.org/formatdomain.html#elementsTime>.

Philipp