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Date: Wed, 10 Sep 2014 15:09:01 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 06/10] parallel: adding vmstate for
	save/restore
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: amit.shah@redhat.com, dgilbert@redhat.com, qemu-devel@nongnu.org, Pavel.Dovgaluk@ispras.ru, quintela@redhat.com

On Tue, Sep 09, 2014 at 03:40:07PM +0200, Paolo Bonzini wrote:
> Il 09/09/2014 15:32, Juan Quintela ha scritto:
> > This breaks migration with old machine type, but as far as I can see,
> > parallel is only added when used, and if we are using it, we need this,
> > right?
> 
> Yes.


Presumably, your next statement means that guests can typically recover
if parallel state is discarded in migration?

>  But again, it only breaks backwards migration, which is not
> supported upstream.
> 
> Paolo

Upstream doesn't provide support for old versions period.
We do our best to make it easy for downstreams to support
cross version migration and they care about both direction,
so I don't see why make an exception here.

So if guests can recover, it seems worth it to
stay bug for bug compatible for old machine types.


> > If my understanding is correct:
> > 
> > Acked-by: Juan Quintela <quintela@redhat.com>
> > 
>