Re: [Xen-devel] Question re live migrate on Xen 4.2 re different cpu capabilities

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.02.13 at 16:59, Alex Bligh <alex@xxxxxxxxxxx> wrote:
> What I want to do is take a particular set of cpu features (which for the
> sake of argument I will do by booting a kvm domain), and say "mask off
> any additional cpuid flags beyond these", so if a new feature gets
> introduced in the Xen codebase, it won't show in the guest. I think the
> only thing I can do at the moment is check the Xen code for every cpu
> feature Xen knows about, remove those I still want, and mask off the rest.
> What I actually want to do is to say "please don't expose any features
> other than these ones, and only expose these if the host supports them",
> so that if we change versions of Xen to one supporting another feature,
> we won't need to poke around in every domain config.

You're heading in a slightly wrong direction here: You don't really
care what features Xen know about or supports. What you do care
about is what features your DomU-s get to see. And that's where
the masking comes into play (and why this can be done on a per
guest basis as well as at the host level).

Jan


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