Re: [Xen-devel] [PATCHv2] x86info: dump kvm cpuid's

[Ian Campbell <ijc@xxxxxxxxxxxxxx>]

On Tue, 2012-05-01 at 16:04 +0300, Gleb Natapov wrote:
> > BTW, according to arch/x86/include/asm/kvm_para.h unsurprisingly KVM has
> > a signature too 'KVMKVMKVM'.
> > 
> > >   cpu->stepping = eax & 0xf;
> > >   cpu->model = (eax >> 4) & 0xf;
> > >   cpu->family = (eax >> 8) & 0xf;
> > > @@ -29,6 +29,19 @@ void get_cpu_info_basics(struct cpudata *cpu)
> > >  
> > >   cpuid(cpu->number, 0xC0000000, &maxei, NULL, NULL, NULL);
> > >   cpu->maxei2 = maxei;
> > > + if (ecx & 0x80000000) {
> > > +         cpuid(cpu->number, 0x40000000, &maxhv, NULL, NULL, NULL);
> > > +         /*
> > > +          * KVM up to linux 3.4 reports 0 as the max hypervisor leaf,
> > > +          * where it really means 0x40000001.
> > 
> > This is something where I definitely think you want to check the
> > signature first.
> In theory yes, but in practice what will this break?

I've got no idea -- but what's the harm in checking?

Ian.

-- 
Ian Campbell
Current Noise: Hypocrisy - Roswell 47

Angels we have heard on High
Tell us to go out and Buy.
                -- Tom Lehrer


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