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Re: [Xen-devel] [XEN-3.4] pv_ops dom0 time/clock handling

To: Daniel Schroeder <sec@xxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [XEN-3.4] pv_ops dom0 time/clock handling
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Wed, 27 May 2009 13:31:23 -0700
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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Daniel Schroeder wrote:
Wed May 27 09:33:12 CEST 2009
Mi Mai 27 11:33:13 CEST 2009

That does look like some kind of TZ issue, but I'm not sure where it would be.

btw: i have checked with 32 bit pvops and 64 bit pvops dom0 and the time
 in the domU is correct with the 64bit pvops dom0 kernel...this wasnt
the same domU...so, next step for me, is to copy the domU to the 64bit
system and try again...to verify, that this only happens for me with
32bit pvops dom0...

How odd.

One difference between pvops time handling and the -xen kernels, is that
they defaulted to slaving the domU time off the hypervisor at all times,
so a system time change would propagate into guests.  I don't implement
that in pvops kernels, so they'll maintain independent time unless you
explicitly sync with some mechanism like ntp.
hmm...does this mean, that i have to use ntp in domU if i use the pvops
kernel? Because time changes in dom0 doesnt propagate into domUs?

It will set its initial time-of-day clock from the hypervisor's at boot, but then proceed independently (but the timebase is derived from the hypervisor's clock). If you want it to track a reference, you need to run ntp.

   J

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