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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.01.17 at 17:28, <andrew.cooper3@xxxxxxxxxx> wrote:
> 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?

Sounds reasonable, together with a brief comment.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel