Re: [Qemu-ppc] [Qemu-devel] [PATCH] target-ppc: Add @cpu_dt_id into migration stream

[Alexander Graf]

On 08.04.14 03:26, Alexey Kardashevskiy wrote:
> On 03/28/2014 12:07 AM, Alexey Kardashevskiy wrote:
> > On 03/27/2014 11:57 PM, Peter Maydell wrote:
> > > On 27 March 2014 12:49, Alexey Kardashevskiy <address@hidden> wrote:
> > > > On 03/27/2014 11:37 PM, Andreas Färber wrote:
> > > > > Am 27.03.2014 03:41, schrieb Alexey Kardashevskiy:
> > > > > > This should prevent the destination guest from misbehaving when
> > > > > > the threads number is different in "-smp" command.
> > > > > Sorry, I don't understand. When migrating, surely -smp needs to be the
> > > > > same on source and destination, so how can they differ?
> > > >
> > > > The idea is that "-smp" does not migrate and if we run source and
> > > > destination guests with different numbers in -smp, we end up with weird
> > > > machine
> > > Yes, so don't do that. As I understand it:
> > >   (1) if you don't run QEMU with the exact same command line
> > >       and config at both ends then migration won't work
> > >   (2) we don't guarantee to detect and cleanly fail if you
> > >       don't do (1)
> > >
> > > It would probably be nice if we did detect config mismatches,
> > Yep, we do not send the device tree (as libvirt does). Pure command line
> > matching won't work.
> >
> > > but that seems to me like a problem we should be addressing
> > > more globally than just for one particular config item for
> > > one particular target...
>
> Ok. So. Let's assume I want to implement migration of "-smp" parameters.
> What would be the correct way of doing this in terms of the current QOM
> principles? Thanks.

You don't. The migration protocol doesn't migrate configuration. If you 
want to start to transfer VM configuration (which I'd be all in for), do 
it properly and transfer _all_ configuration.


Alex