Re: [Xen-devel] [PATCH 10/24] xen: mask XSAVE from cpuid

Arjan van de Ven
2009-03-16T00:11:18Z

On Sun, 15 Mar 2009 17:05:26 -0700
Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> Arjan van de Ven wrote:
> > This is indicative of something that might be a huge bug in Xen:
> > Xen should never ever pass through CPUID bits it does not know.
> > If Xen does not honor that, there is a fundamental and eternally
> > recurring problem.... every time something new gets introduced Xen
> > likely breaks.
>
> Yes, I'd agree; Xen should whitelist cpu capabilities rather than
> blacklist them. Jan expressed the opposite opinion (on the grounds
> that it precludes using features which don't require special OS or
> hypervisor support without Xen modifications).

Well.. pretty much all new instructions need Xen modifications due to
the need to be emulate to deal with traps/vmexits/etc right?
So I don't quite see many cpuid bits that would NOT involve some Xen
modification or another ;)

--
Arjan van de Ven Intel Open Source Technology Centre
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