I have a system running openSUSE 11.2 with Desktop and XEN kernel, as well as Windows 7 (not by choice though…). I have noticed a strange time issue, with Windows 7 and the desktop kernel the time is correct (like for example now: 1:32 PM) but in the XEN kernel it is ahead several hours (6:32 PM). If it was an issue between openSUSE and windows then I would think that it is a problem with the system clock but I don’t know what would cause a time issue between kernels like that. I’m not sure if this is a bug in the XEN kernel or what.
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Are you possibly only going to the Xen kernel after being booted to
windows? Do the times show wrong a bit more consistently in windows if
you prevent any network connection (to synchronize time to the world) when
booting into windows? I do not know how much the kernel has to do with
getting the original time… hwclock will get the time from your hardware
clock but I think the system does that as well on bootup and then either
uses that directly (if your local time is set in the hardware clock) or
calculates your timezone offset (if your hardware clock is set to be using
UTC). Windows always uses the local time in the hardware clock and will
set the local time back in there so a boot from windows to *nix usually
munges things up if the Linux side is set to treat the hardware clock as
UTC. When booting from *nix to windows the system will often sync with
the world before you see the clock. NTP does not normally allow this kind
of behavior though since if you’re off by more than one thousand seconds
(17-ish minutes) the time source is declared to be INSANE (literally) and
synchronization of time stops.
Anyway… knowing how you boot to Linux/windows from windows/Linux could
help identify the problem, or maybe this is a bug in how the OS is setup
with each kernel.
On 02/11/2010 11:36 AM, vendion wrote:
> I have a system running openSUSE 11.2 with Desktop and XEN kernel, as
> well as Windows 7 (not by choice though…). I have noticed a strange
> time issue, with Windows 7 and the desktop kernel the time is correct
> (like for example now: 1:32 PM) but in the XEN kernel it is ahead
> several hours (6:32 PM). If it was an issue between openSUSE and
> windows then I would think that it is a problem with the system clock
> but I don’t know what would cause a time issue between kernels like
> that. I’m not sure if this is a bug in the XEN kernel or what.
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I’ve seen clocks in VMs do odd things if the CPU speed is dynamically changing. Also be sure that the clocks are set to the same standard. ie either both local or both UTC A five hour difference assuming you are in eastern USA indicates that one is local the other UTC.
I only boot into the windows partition once or twice a month, if not even that, I mostly go from the Desktop kernel to the XEN kernel and the time problem was happening there which is why I’m wondering if it is a problem with the XEN kernel. If it helps I do have my system clock set for local time in YaST, did that when I installed openSUSE 11.2. To add on I never have time issues when going from Desktop kernel/Windows or Windows/Desktop kernel which to me kind of points the finger to XEN, hence this thread.
The problem is not exactly with the VM guests, it is with the host, openSUSE 11.2 XEN kernel. The time in the guest OS are sometimes correct even though the host has the wrong time, not sure if NTP is coming to play for this or not I will disable that in the guests to check.
If you run Windows at all to have the correct time in all OS’s you must user the local setting. All Os’s must use the same underlying assumption on how the hardware clock is set.
Yes I know that and that is how it is set up but the XEN kernel doesn’t like something about it.