[Xen-devel] Re: Xen HVM cpuid problem

[Christoph Egger <Christoph.Egger@xxxxxxx>]

On Tuesday 13 May 2008 14:56:00 Keir Fraser wrote:
> All HVM guests receive a default configuration from libxc's
> xc_cpuid_apply_policy(). You must update your tools if you have updated
> your hypervisor to recent xen-unstable. Otherwise you will indeed get bogus
> CPUID behaviour.

Tnx. Updating the tools fixed it. I should get used on updating the tools more 
regularly. Sorry for the noise.

Christoph

>
>  -- Keir
>
> On 13/5/08 13:41, "Christoph Egger" <Christoph.Egger@xxxxxxx> wrote:
> > Hi Keir,
> >
> > For HVM guests, all cpuid Fn's going through domain_cpuid()
> > iterate over the loop and then return 0 for all four registers.
> >
> > Guests OS's and cpuid tools in HVM which query for
> > cpuid Fn 0000.0000 %eax and 8000.0000 %eax, see the value 0 and think,
> > Xen emulates oldish 386/486 CPUs.
> >
> > This leads to strange boot failures, "your CPU does not support long
> > mode" or "minimum required CPU is a 486DX CPU" when launching 32bit or
> > 64bit HVM guests.
> >
> > To reproduce this, cpuid is NOT explicitely configured
> > in the guest config file.
> >
> > BTW: Is there a reason for not handling cpuid in one central place?
> >
> > Christoph



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