Re: [Qemu-devel] [PATCH v3 0/2] Fix migration of old pseries

[David Gibson]

On Fri, Feb 19, 2016 at 08:59:44AM +0100, Greg Kurz wrote:
> On Fri, 19 Feb 2016 11:11:47 +1100
> David Gibson <address@hidden> wrote:
> 
> > On Thu, Feb 18, 2016 at 12:32:11PM +0100, Greg Kurz wrote:
> > > QEMU 2.4 broke the migration of old pseries machine with the addition
> > > of configuration sections, which are sent unconditionally.
> > > 
> > > We assume that QEMU 2.3 is more deployed than any newer release (based on
> > > the versions currently shipped by most distros). This v3 series hence
> > > reverses the logic from v2: it now fully fixes migration of old pseries
> > > from/to QEMU 2.3 and provides a manual workaround for the QEMU 
> > > 2.4/2.4.1/2.5
> > > case.
> > > 
> > > With this series, I could migrate the same pseries-2.3 instance in a full
> > > 2.3->2.6->2.5->2.6->2.4->2.6->2.3 cycle.  
> > 
> > Sorry, I've lost track slightly here.  Does this series apply on top
> > of, or instead of your earlier series that peeks for the config
> > section?
> > 
> 
> This v3 series applies instead of the v2 that peeks for the config section.

Ok, thanks for the clarification.

> It was suggested by Laurent during review, and motivated by your decision
> to favor fixing 2.3 over 2.4.
> 
> As shown in Laurent's detailed test report, migration from/to 2.3.x now works
> out of the box and 2.4.x/2.5 requires qom-set.
> 
> I was also feeling a bit uncomfortable with all these machine properties to
> disable the configuration section, which was explicitly coded to be 
> non-optional
> according to the changelog of commit 61964c23. The logic inversion in v3 seem
> to be friendlier with the configuration section design.
> 
> Juan, could you share your thoughts ?

With an ack from Juan I'll be happy to merge this to ppc-for-2.6.

-- 
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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