[libvirt-users] How to use rtc_timeoffset (XL toolkit option) in Libvirt and Xen/libxl hypervisor?

[Volo M.]

Hello techs,

We used XL toolkit for Xen hypervisor for starting Windows hvm VMs and the
option rtc_timeoffset worked perfectly with XL. It helped us to set correct
Timezone time/offset for Windows HVM VMs from inside virtual_machine xen
config.

For example:
Below option WORKS perfectly with XL toolkit.
[***@hw12xen ~]# cat goillltawdlssq.xl.cfg | grep offset
rtc_timeoffset = "7200" # +2 hours to UTC time (or +/-3600=+/-1 hour to
UTC time)
[***@hw12xen ~]#

Now we try to migrate all the Windows hvm VMs to using Libvirt and Xen
4.6.6 (or 4.4).
But as we see it's impossible to make VMs using correct time/offset set in
XML config like below:

below Libvirt option DOESN'T WORK as we expect...
[***@hw12xen ~]# cat goillltawdlssq.var.xml | grep offset
<clock offset='variable' adjustment='7200' />
[***@hw12xen ~]#

Can you please explain if there's something we're doing wrong way or it's
just a bug like described here:
https://bugzilla.redhat.com/show_bug.cgi?id=1212191 ?

Thanks in advance.

[Jim Fehlig]

Post by Volo M.
Hello techs,
We used XL toolkit for Xen hypervisor for starting Windows hvm VMs and the
option rtc_timeoffset worked perfectly with XL. It helped us to set correct
Timezone time/offset for Windows HVM VMs from inside virtual_machine xen config.
Below option WORKS perfectly with XL toolkit.
rtc_timeoffset = "7200"   # +2 hours to UTC time (or +/-3600=+/-1 hour to UTC time)
Now we try to migrate all the Windows hvm VMs to using Libvirt and Xen 4.6.6 (or
4.4).
But as we see it's impossible to make VMs using correct time/offset set in XML
below Libvirt option DOESN'T WORK as we expect...
  <clock offset='variable' adjustment='7200' />
Can you please explain if there's something we're doing wrong way or it's just a
https://bugzilla.redhat.com/show_bug.cgi?id=1212191   ?

No, you're not doing anything wrong. And yes, you've hit that bug, although I'd
prefer to call it an enhancement request. Xen's rtc_timeoffset setting is
currently not supported by the libvirt libxl driver.

Regards,
Jim

[Volo M.]

Jim,

Thanks a lot for your confirmation.
Could you also please explain if the issue can be ever fixed, if it's
possible to make some patch to fix it?
Is it libvirt-specific bug or Libvirt development team rely on some other
developers of libxl code...etc?
I'm asking because XL tools works fine and I wonder if XL uses the same
libxl libraries , doesn't it?
Lastly is the issue is going be fixed in near time? Can you answer my
questions and ask for some patch for
enhancement request or I should better send a separate email to development
team ("libvir-***@redhat.com
<https://www.redhat.com/mailman/listinfo/libvir-list>") ?
Thanks a lot in advance for your answers...

Post by Jim Fehlig

Post by Volo M.
Hello techs,
We used XL toolkit for Xen hypervisor for starting Windows hvm VMs and
the option rtc_timeoffset worked perfectly with XL. It helped us to set
correct Timezone time/offset for Windows HVM VMs from inside
virtual_machine xen config.
Below option WORKS perfectly with XL toolkit.
rtc_timeoffset = "7200" # +2 hours to UTC time (or +/-3600=+/-1 hour to
UTC time)
Now we try to migrate all the Windows hvm VMs to using Libvirt and Xen
4.6.6 (or 4.4).
But as we see it's impossible to make VMs using correct time/offset set
below Libvirt option DOESN'T WORK as we expect...
<clock offset='variable' adjustment='7200' />
Can you please explain if there's something we're doing wrong way or it's
https://bugzilla.redhat.com/show_bug.cgi?id=1212191 ?

No, you're not doing anything wrong. And yes, you've hit that bug,
although I'd prefer to call it an enhancement request. Xen's rtc_timeoffset
setting is currently not supported by the libvirt libxl driver.
Regards,
Jim

[Jim Fehlig]

Post by Volo M.
Jim,
Thanks a lot for your confirmation.
Could you also please explain if the issue can be ever fixed, if it's possible
to make some patch to fix it?

Yes, it can be fixed. I just submitted a patch to the libvirt dev list

https://www.redhat.com/archives/libvir-list/2018-February/msg00981.html

Please test it and provide feedback if you are able to do so. Thanks!

Regards,
Jim