[Xen-users] Re: NTP problem

[Ferenc Wagner <wferi@xxxxxxx>]

Linux student <mysublists@xxxxxxxxx> writes:

>> I'm not sure everybody else here knows Fedora kernels by heart.  I
>> don't, so you may want to give kernel versions for better support.
>>
>> But I suppose Fedora 10 uses a pvops domU kernel (2.6.26 or later),
>> which has no built-in support for dom0 clock sync.  You have to use
>> NTP or some other user space method for syncing the domU clock.
>
> According to xen docs "By default, the clocks in a Linux VM are
> synchronized to the clock running on the control domain, and cannot
> be independently changed.  This mode is a convenient default, since
> only the control domain needs to be running the NTP service to keep
> accurate time across all VMs."
>
> So logically speaking it should be Dom0 kernel controlling time
> related tasks not the DomU ?

That used to be the case with 2.6.18 (and various forward ports of
that official Xen patch).  But the incorporation of Xen into mainline
Linux (via paravirt ops) changed this.  The clock of pvops guests is
synced on domain boot to the dom0 clock, but runs independently after
that.
-- 
Cheers,
Feri.

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