Re: [Qemu-devel] [Qemu-ppc] [PATCH] spapr/ppc: fix backward migration to QEMU 2.9

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Jun 20, 2017 at 04:19:01PM +0200, Greg Kurz wrote:
> On Tue, 20 Jun 2017 15:08:47 +0200
> Laurent Vivier <lvivier@redhat.com> wrote:
> 
> > On 19/06/2017 19:05, Greg Kurz wrote:
> > > Commit c783b0012708 ("ppc: Rework CPU compatibility testing across
> > > migration") added a subsection to the vmstate description of CPUs.
> > > This subsection is sent when the CPU compat_pvr field is non-zero,
> > > which is likely to happen after CAS negociation (since QEMU 2.9) or
> > > even before CAS negociation if the user explicitely asked for compat
> > > mode.
> > > 
> > > This breaks backward migration of existing pseries-2.9 machine types
> > > since they don't know about this "compat" subsection:
> > > 
> > > qemu-system-ppc64: error while loading state for instance 0x0 of
> > >  device 'cpu'
> > > 
> > > This patch reverts to the behavior of simply ignoring the PVR when
> > > migrating older machines (ie, let the migration succeed if the user
> > > is sure that the CPU on the destination is close enough to work).
> > > 
> > > Signed-off-by: Greg Kurz <groug@kaod.org>  
> > 
> > Reviewed-by: Laurent Vivier <lvivier@redhat.com>
> > 
> > but I think it should be merged with patch ("ppc: Rework CPU
> > compatibility testing across migration") that is not merged and in the
> > maintainer tree.
> > 
> 
> I agree this would be better for bisect.

As suggested, folded into the existing patch.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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