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RE: [Xen-users] 'lowest common denominator' cpuid feature set

To: "Keith Coleman" <list.keith@xxxxxxxxxxx>
Subject: RE: [Xen-users] 'lowest common denominator' cpuid feature set
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Wed, 18 Nov 2009 12:20:06 +1100
Cc: Xen Users <xen-users@xxxxxxxxxxxxxxxxxxx>
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Thread-topic: [Xen-users] 'lowest common denominator' cpuid feature set
> On Tue, Nov 17, 2009 at 5:56 PM, James Harper
> <james.harper@xxxxxxxxxxxxxxxx> wrote:
> > I want to be able to test live migration... I have an intel box and
an
> > amd box, so live migration between them won't 'just work'. From what
> > I've read though, I should be able to use cpuid to turn off all the
cpu
> > features which might be different between them. Is this do-able? I'm
> > willing to accept any resulting loss of performance etc.
> >
> 
> James,
> 
> You can use localhost as the migration target to eliminate CPU and
> shared storage requirements.

I've seen problems with device usage (fail to bind to vbd because it is
already in use because the 'source' instance is still using it). That
was a while ago though.

> 
> It's possible to mask cpu features resulting in a generic vcpu that
> should run on intel or amd. The following excerpt is taken from the
> xen sample config file xmexample.hvm:
> 
> From the xmexample.hvm
> #  Downgrade the cpuid to make a better compatibility for migration :

That worked perfectly - migrated from the AMD machine to the Intel
machine and back again.

Thanks

James

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