Re: [Xen-devel] [PATCH v10 10/11] xen: add new Xen cpuid node for max address width info

[Juergen Gross <jgross@xxxxxxxx>]

On 28/09/17 11:40, Jan Beulich wrote:
>>>> On 28.09.17 at 11:04, <jgross@xxxxxxxx> wrote:
>> On 28/09/17 10:59, Jan Beulich wrote:
>>>>>> On 25.09.17 at 12:00, <jgross@xxxxxxxx> wrote:
>>>> --- a/xen/arch/x86/traps.c
>>>> +++ b/xen/arch/x86/traps.c
>>>> @@ -930,6 +930,13 @@ void cpuid_hypervisor_leaves(const struct vcpu *v, 
>>>> uint32_t leaf,
>>>>          res->b = v->vcpu_id;
>>>>          break;
>>>>  
>>>> +    case 5: /* PV-specific parameters */
>>>> +        if ( is_hvm_domain(d) || subleaf != 0 )
>>>> +            break;
>>>> +
>>>> +        res->a = generic_flsl(get_upper_mfn_bound()) + PAGE_SHIFT;
>>>
>>> While preparing to commit this I wondered why this isn't just
>>> flsl(). Can you explain this, or can I just change it?
>>
>> It is meant to be similar to CPUID leaf 0x80000008: the width of the
>> max. machine address, not that of the max. MFN.
> 
> I don't see how this addresses the question: Just to repeat with
> slightly different wording - why are you using generic_flsl() instead
> of just flsl()?

Oh, sorry, just got the question wrong.

No specific reason for generic_flsl().

I'm just about to send the last 3 patches as a V11, so no need for you
to modify the patch.


Juergen

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