Re: [Qemu-devel] [Qemu-stable] [PATCH 28/35] spapr: skip configuration section during migration of older machines

[Greg Kurz]

On Tue, 22 Mar 2016 17:35:18 -0500
Michael Roth <address@hidden> wrote:

> Quoting Greg Kurz (2016-03-22 02:49:35)
> > On Mon, 21 Mar 2016 12:28:26 -0500
> > Michael Roth <address@hidden> wrote:
> >   
> > > From: Greg Kurz <address@hidden>
> > > 
> > > Since QEMU 2.4, we have a configuration section in the migration stream.
> > > This must be skipped for older machines, like it is already done for x86.
> > > 
> > > This patch fixes the migration of pseries-2.3 from/to QEMU 2.3, but it
> > > breaks migration of the same machine from/to QEMU 2.4/2.4.1/2.5. We do
> > > that anyway because QEMU 2.3 is likely to be more widely deployed than
> > > newer QEMU versions.
> > > 
> > > Fixes: 61964c23e5ddd5a33f15699e45ce126f879e3e33
> > > Signed-off-by: Greg Kurz <address@hidden>
> > > Reviewed-by: Laurent Vivier <address@hidden>
> > > Reviewed-by: Juan Quintela <address@hidden>
> > > Signed-off-by: David Gibson <address@hidden>
> > > (cherry picked from commit 09b5e30da5b19f44768a5429f603caaede216757)
> > > 
> > > Conflicts:
> > >       hw/ppc/spapr.c
> > > 
> > > *remove dep on 5013c5474
> > > 
> > > Signed-off-by: Michael Roth <address@hidden>
> > > ---  
> > 
> > This will break migration of pseries-2.3 from QEMU 2.5 to QEMU 2.5.1. Maybe
> > this should be documented somewhere ?
> > 
> > Also, there's a companion patch to allow migration to succeed with manual
> > intervention on the destination:
> > 
> > commit 902c053d834e3b802ec736f170edf226d4a841ff
> > Author: Greg Kurz <address@hidden>
> > Date:   Thu Feb 18 12:32:25 2016 +0100
> > 
> >     migration: allow machine to enforce configuration section migration
> > 
> > Maybe worth to push to stable as well ?  
> 
> Yah, makes sense. I'll include this patch and document compatibility
> changes in the release notes.
> 
> Is this wording correct?
> 
> "Fixes migration between QEMU 2.3 and QEMU 2.5.1 when running
> pseries-2.3 machine model. Note that for migration of same
> pseries-2.3 machine to/from QEMU versions 2.4.x and 2.5, 
> the -machine enforce-config-section=on option now needs to be
> used."
> 

Of course this is also the case for older pseries (< 2.3) but the wording
is correct.

Thanks !

> >   
> > >  hw/ppc/spapr.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index 6bfb908..ff1537a 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -2327,6 +2327,7 @@ static void spapr_compat_2_3(Object *obj)
> > >  {
> > >      savevm_skip_section_footers();
> > >      global_state_set_optional();
> > > +    savevm_skip_configuration();
> > >  }
> > > 
> > >  static void spapr_compat_2_2(Object *obj)  
> >