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Re: [Qemu-ppc] [RFC PATCH] spapr: support time base offset migration

From: Benjamin Herrenschmidt
Subject: Re: [Qemu-ppc] [RFC PATCH] spapr: support time base offset migration
Date: Fri, 06 Sep 2013 00:26:59 +1000

On Thu, 2013-09-05 at 16:14 +0200, Andreas Färber wrote:

> Are you thinking of POWER8 having a different frequency than POWER8 in
> compat mode? Because migration from one -cpu to another is not supported
> elsewhere.
> Even if we want to migrate from one POWER7 revision to another, we
> should let the destination use the revision of the source (guest ABI!),
> via property if need be. Anything else will lead to confusion as to what
> is supported and what is not. That -cpu host is the default for
> convenience shouldn't relieve admins/libvirt to think about sensible
> setups like they have to on x86.

Besides POWER8 uses 512Mhz too :-) It's been architected so it's
unlikely to change from now on.


> Andreas
> > 
> > But yes, without frequency adjustment I see where you're coming from. We 
> > still only need the timebase the guest sees, not the offset. But we also 
> > need the host wall clock to allow for adjustments :).
> > 
> > 
> > Alex
> > 

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