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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Fri, 06 Sep 2013 00:26:59 +1000
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Subject: Re: [Qemu-devel] [RFC PATCH] spapr: support time base offset
	migration
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To: Andreas =?ISO-8859-1?Q?F=E4rber?= <afaerber@suse.de>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>, qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>, qemu-ppc@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, Paul Mackerras <paulus@samba.org>, David Gibson <david@gibson.dropbear.id.au>

On Thu, 2013-09-05 at 16:14 +0200, Andreas F=C3=A4rber wrote:

> Are you thinking of POWER8 having a different frequency than POWER8 in
> compat mode? Because migration from one -cpu to another is not supporte=
d
> elsewhere.
>=20
> 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 wha=
t
> 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.

Cheers,
Ben.

> Andreas
>=20
> >=20
> > 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 a=
lso need the host wall clock to allow for adjustments :).
> >=20
> >=20
> > Alex
> >=20
>=20
>=20