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Re: [Xen-devel] [PATCH] Handle older Xen save files where arbytes are in

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Handle older Xen save files where arbytes are in the wrong format.
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Fri, 13 Feb 2009 09:18:51 +0000
Cc: "Keir.Fraser@xxxxxxxxxxxx" <Keir.Fraser@xxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Zhai, Edwin" <edwin.zhai@xxxxxxxxx>, John Levon <levon@xxxxxxxxxxxxxxxxx>
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At 13:41 -0500 on 12 Feb (1234446081), Keir Fraser wrote:
> On 12/02/2009 18:20, "John Levon" <levon@xxxxxxxxxxxxxxxxx> wrote:
> 
> >>> What happens with a new-format image on an old Xen?
> >> 
> >> Doesn't work
> > 
> > Sure, but doesn't work how? There's a world of difference between
> > "crashes mysteriously" and "useful error message".
> 
> Mmm.. Most of the changes will cause restore failure rather than apparently
> successful restore but you end up with a broken guest. I suppose this
> segmentation change may act like the latter. I don't think there's been much
> conscious effort to make new-on-old fail cleanly though.

There is some code in there that checks that the changeset of Xen is the
same as the one the image was saved on -- it only works if hg was
available when Xen was built, and is certainly too strict.  It could be
replaced with something more useful like the Xen version number. 

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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