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

[Greg Kurz]

On Fri, 19 Feb 2016 15:41:10 +0100
Laurent Vivier <address@hidden> wrote:

> On 18/02/2016 12:32, 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.  
> 
> I've tested all possible combinations, with and without these patches.
> The result is here:
> 
> http://wiki.qemu.org/Migration/Compatibility/pseries
> 

Excellent ! Thanks for setting this up.

> - Migration is totally broken in qemu-2.2

Hmm... I get another error with qemu-2.2:

htab_load() bad index -65536 (0+8454 entries) in htab stream (htab_shift=26)
qemu: warning: error while loading state section id 20
qemu-system-ppc64: load of migration failed: Invalid argument

but my command line is different from yours.

> - without these patches, migration cannot be done from/to qemu-2.3
> - with these patches, qemu-2.3 can migrate to/from qemu-2.6
> - 1st patch breaks pseries-2.2, pseries-2.3 migration from/to
>   qemu-2.4/2.5 but 2nd patch allows to fix this manually.
> 
> Feel free to update the page.
> 
> Laurent
>