[Xen-devel] Re: para virt cpuid?

[Jan Schneider <timberwolf@xxxxxxxxxxxxxxx>]

Ian Pratt <m+Ian.Pratt <at> cl.cam.ac.uk> writes:
> For some cpu features it may be possible to take a trap the first time
> they are used, and hence 'taint' the domain with a marker that says it
> can only be migrated to hosts that support the feature. I haven't
> thought through how widely this technique would work, though. We
> probably need to go through and audit all the post Pentium Pro features
> and decide a) whther they're visable to user space b) whether a trap can
> be generated on first use.

That shouldn't be too important, because migrations between different cpu's 
isn't
exactly what will be done in production environments.
So a simple global check that source-xen-hostA has the same cpu-featureset as
target-xen-hostB should be enough.
Xen should than issue a warning that the migration-target is equipped with a
different cpu/cpu-feautureset.
A check hat tracks used features would be slightly overkill, also it could be an
additional error-source.
I think KISS would be the right way for this topic.
Of course thats an personal opininion out of a production environment ;).



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