Re: [Xen-devel] [PATCH v2 07/25] x86/cpuid: Dispatch cpuid_hypervisor_leaves() from guest_cpuid()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 09/01/17 16:21, Jan Beulich wrote:
>>>> On 09.01.17 at 12:03, <andrew.cooper3@xxxxxxxxxx> wrote:
>> --- a/xen/arch/x86/cpuid.c
>> +++ b/xen/arch/x86/cpuid.c
>> @@ -346,7 +346,10 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
>>      case 0x40000000 ... 0x400000ff:
>>          if ( is_viridian_domain(d) )
>>              return cpuid_viridian_leaves(v, leaf, subleaf, res);
>> -        break;
>> +
>> +        /* Fallthrough. */
>> +    case 0x40000100 ... 0x4fffffff:
>> +        return cpuid_hypervisor_leaves(v, leaf, subleaf, res);
> Based on what was the upper bound here chosen? It would be rather
> helpful if you could leave a pointer to whatever source here in a
> comment. I would have expected 0x4000ffff or 0x7fffffff here ...

Intel reserves 0x40000000 ... 0x4fffffff for hypervisor use.

AMD only reserves 0x40000000 ... 0x400000ff for hypervisor use, but we
already use space beyond that region.

I could clip at 0x400001ff, as that is the realistic upper bound we
currently use?

~Andrew

>
> Other than that
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> Jan
>


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