Re: [Xen-devel] [PATCH v9 10/10] xen: add new Xen cpuid node for max address width info

[Juergen Gross <jgross@xxxxxxxx>]

On 22/09/17 16:47, Jan Beulich wrote:
>>>> On 22.09.17 at 13:41, <jgross@xxxxxxxx> wrote:
>> --- a/xen/arch/x86/traps.c
>> +++ b/xen/arch/x86/traps.c
>> @@ -929,6 +929,13 @@ 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;
>> +        break;
> 
> The subleaf check here should be mirrored ...
> 
>> --- a/xen/include/public/arch-x86/cpuid.h
>> +++ b/xen/include/public/arch-x86/cpuid.h
>> @@ -85,6 +85,15 @@
>>  #define XEN_HVM_CPUID_IOMMU_MAPPINGS   (1u << 2)
>>  #define XEN_HVM_CPUID_VCPU_ID_PRESENT  (1u << 3) /* vcpu id is present in 
>> EBX 
>> */
>>  
>> -#define XEN_CPUID_MAX_NUM_LEAVES 4
>> +/*
>> + * Leaf 6 (0x40000x05)
>> + * PV-specific parameters
>> + * EAX: bits 0-7: max machine address width
>> + */
> 
> ... in the comment here. This is easily doable while committing,

Up to now there is no example for this: the time leaf isn't documented
and the HVM leaf from which I copied the subleaf check doesn't have
anything related to it in the comments.

Do you have any special format recommendations?

And should I add related comments to the HVM leaf section?

> but I'd like to be certain Andrew in particular has no objections
> to this new leaf before putting this in.

Sure.


Juergen


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