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Subject: Re: [Qemu-devel] [RFC PATCH] spapr: support time base offset
	migration
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To: Alexander Graf <agraf@suse.de>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "qemu-ppc@nongnu.org" <qemu-ppc@nongnu.org>, Paolo Bonzini <pbonzini@redhat.com>, Paul Mackerras <paulus@samba.org>, Andreas =?ISO-8859-1?Q?F=E4rber?= <afaerber@suse.de>, David Gibson <david@gibson.dropbear.id.au>

On Mon, 2013-09-09 at 11:32 +0200, Alexander Graf wrote:
> On 09.09.2013, at 11:29, Benjamin Herrenschmidt wrote:
> 
> > On Mon, 2013-09-09 at 08:06 +0200, Alexander Graf wrote:
> >> I think it's ok to restrict live migration to machines with the same
> >> tb frequency when kvm is enabled. Whether you implement it through a
> >> hardcoded 512Mhz or through a timebase value that gets live migrated
> >> and then compared is up to you - both ways work for me :).
> > 
> > The latter might be handy if we want to support migration on 970, though
> > we don't have the TBU40 stuff there so adjusting the TB in the host
> > kernel would be ... problematic.
> 
> Well, we could save/restore TB when we enter/exit the guest, no? 

Hard to do without introducing drift...

> But I really only want to have something that doesn't block the door for someone who wants to enable things.
> 
> 
> Alex