Re: [PATCH RFCv2 01/20] kvm: kvm_get_writable_id_regs

[Eric Auger]

Hi Richard,

On 12/12/24 14:59, Richard Henderson wrote:
> On 12/6/24 05:21, Cornelia Huck wrote:
>> +#define NR_ID_REGS (3 * 8 * 8)
>> +
>> +typedef struct IdRegMap {
>> +    uint64_t regs[NR_ID_REGS];
>> +} IdRegMap;
>> +
>
> Where does the NR_ID_REGS come from?  In particular the * 3?
> IIRC, all of the id registers are in op0=3, op1=0, crn=0, crm={0-7},
> op2={0-7}.

According to the KVM API and code,

"The Feature ID space is defined as the AArch64 System register space
with +op0==3, op1=={0, 1, 3}, CRn==0, CRm=={0-7}, op2=={0-7}."


hence that choice

See:
https://lore.kernel.org/all/20230919175017.538312-3-jingzhangos@google.com/

Definitively we can add a comment

Thanks

Eric

>
> Whatever the actual answer, some comments would be good.
>
>
> r~
>