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Re: [Xen-devel] Domain Save Image Format proposal (draft B)

David Vrabel writes ("Domain Save Image Format proposal (draft B)"):
> Here is a draft of a proposal for a new domain save image format.  It
> does not currently cover all use cases (e.g., images for HVM guest are
> not considered).

I think this is a good start.  I've made some other comments already.

> Overview
> ========

I would like to make another perhaps controversial suggestion.  We
should explicitly specify that the receiver may advertise its
capabilities to the sender, so that backwards-migration _can_ be
supported if we choose to do so.

In practice I think that means a capability advertisement block.
Probably, one bit per version, one bit per record type, etc.

I greatly prefer doing forward-compatibility with new record type
enums etc. than with version numbers.  Version numbers presuppose a
strict global order on all the implementations' capabilities, which is
of course not necessarily true in free software.


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