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[Qemu-devel] Re: The State of the SaveVM format
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] Re: The State of the SaveVM format |
Date: |
Wed, 9 Sep 2009 12:33:27 +0300 |
User-agent: |
Mutt/1.5.19 (2009-01-05) |
On Wed, Sep 09, 2009 at 11:22:50AM +0200, Juan Quintela wrote:
> "Michael S. Tsirkin" <address@hidden> wrote:
> > On Wed, Sep 09, 2009 at 10:47:27AM +0200, Juan Quintela wrote:
> >> More problems: Going from newer versions to old versions
> >> - I think that everybody thinks that this is a nice to have, but that it
> >> will took a lot to make it work, and there are more urgent things to
> >> do.
> >
> > It's actually easy if you make whatever is new in the new version an
> > optional feature. Then to save in an old format, qemu is started with
> > the feature disabled.
>
> That only works if invariants are maintained. That is not true in
> general. And furthermore, you are deciding that if you find a bug, and
> fix needs a new field -> just live with the bug.
Clarification: add an *option* to live with the bug, off by default.
> If you can recreate the state without the new field, then _why_ did
> you added it in the 1st place?
>
> Later, Juan.