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[Xen-ia64-devel] RE: Xen-ia64-devel Digest, Vol 11, Issue 22
- To: <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
- From: "Luck, Tony" <tony.luck@xxxxxxxxx>
- Date: Fri, 10 Feb 2006 11:36:19 -0800
- Delivery-date: Fri, 10 Feb 2006 19:47:50 +0000
- List-id: Discussion of the ia64 port of Xen <xen-ia64-devel.lists.xensource.com>
- Thread-index: AcYuK2BYTZdSlj7yQ7+1jCQnmgWKdgATQKDw
- Thread-topic: Xen-ia64-devel Digest, Vol 11, Issue 22
> > > during boot, linux kernel tries to synchronize itc of all processors.
> > > However currently itc is not virtualized:
> > > (XEN) vcpu_set_itc: Setting ar.itc is currently disabled
> > >
> > > What should we do ?
> > > a) virtualize ITC
> > > b) para-virtualize ITC (ie, modifying linux kernel)
> > > c) pre-synchronize ITC
> > >
> > > I really prefer c).
> > I'm not sure I understand c). Aren't the ITCs already
> > pre-synchronized by xen in smp_callin()? Thanks,
> Correct, but Linux is not aware of this.
> After more thoughs, I really think this is the best solution.
What if you are running on h/w where ITC cannot be synchronized
because different cpus are driven from different clock sources?
Solution d) might be to tell the guest that itc isn't syncronized
(even on systems where it could be).
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