[Xen-devel] Re: Xen HVM cpuid problem

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

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.

 -- 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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