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

[Greg Kurz]

On Mon, 22 Feb 2016 12:09:12 +1100
David Gibson <address@hidden> wrote:

> 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.
> 

And the patches even got reviewed by Juan ! Please merge ! :)