Re: [Xen-devel] [PATCH 06/13] libx86: Introduce a helper to serialise a cpuid_policy object

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.07.18 at 10:42, <wei.liu2@xxxxxxxxxx> wrote:
> On Tue, Jul 03, 2018 at 09:55:19PM +0100, Andrew Cooper wrote:
>> --- a/xen/include/public/arch-x86/xen.h
>> +++ b/xen/include/public/arch-x86/xen.h
>> @@ -314,6 +314,17 @@ struct xen_arch_domainconfig {
>>  #define XEN_ACPI_GPE0_CPUHP_BIT      2
>>  #endif
>>  
>> +/*
>> + * Representations of architectural CPUID information.  Used as the
>> + * serialised version of Xen's internal representation.
>> + */
>> +typedef struct xen_cpuid_leaf {
>> +#define XEN_CPUID_NO_SUBLEAF 0xffffffffu
>> +    uint32_t leaf, subleaf;
>> +    uint32_t a, b, c, d;
>> +} xen_cpuid_leaf_t;
>> +DEFINE_XEN_GUEST_HANDLE(xen_cpuid_leaf_t);
>> +
> 
> Is putting this in public header while leaving
> CPUID_MAX_SERIALISED_LEAVES in a private header useful?
> 
> How does an external user know how big a buffer it needs to provide to
> accommodate the return structure?

Yeah, this is indeed hard to tell from this patch alone. And going
over the titles of the remainder of the series it's also not clear
where a use of this structure in a domctl/sysctl would appear.

Jan



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