Re: [PATCH v7 13/13] xen/cpufreq: Adapt SET/GET_CPUFREQ_CPPC xen_sysctl_pm_op for amd-cppc driver

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.08.2025 08:35, Jan Beulich wrote:
> On 28.08.2025 06:06, Penny, Zheng wrote:
>>> -----Original Message-----
>>> From: Jan Beulich <jbeulich@xxxxxxxx>
>>> Sent: Tuesday, August 26, 2025 12:03 AM
>>>
>>> On 22.08.2025 12:52, Penny Zheng wrote:
>>>> --- a/xen/include/public/sysctl.h
>>>> +++ b/xen/include/public/sysctl.h
>>>> @@ -336,8 +336,14 @@ struct xen_ondemand {
>>>>      uint32_t up_threshold;
>>>>  };
>>>>
>>>> +#define CPUFREQ_POLICY_UNKNOWN      0
>>>> +#define CPUFREQ_POLICY_POWERSAVE    1
>>>> +#define CPUFREQ_POLICY_PERFORMANCE  2
>>>> +#define CPUFREQ_POLICY_ONDEMAND     3
>>>
>>> Without XEN_ prefixes they shouldn't appear in a public header. But do we
>>> need ...
>>>
>>>>  struct xen_get_cppc_para {
>>>>      /* OUT */
>>>> +    uint32_t policy; /* CPUFREQ_POLICY_xxx */
>>>
>>> ... the new field at all? Can't you synthesize the kind-of-governor into 
>>> struct
>>> xen_get_cpufreq_para's respective field? You invoke both sub-ops from xenpm
>>> now anyway ...
>>>
>>
>> Maybe I could borrow governor field to indicate policy info, like the 
>> following in print_cpufreq_para(), then we don't need to add the new filed 
>> "policy"
>> ```
>> +    /* Translate governor info to policy info in CPPC active mode */
>> +    if ( is_cppc_active )
>> +    {
>> +        if ( !strncmp(p_cpufreq->u.s.scaling_governor,
>> +                      "ondemand", CPUFREQ_NAME_LEN) )
>> +            printf("cppc policy           : ondemand\n");
>> +        else if ( !strncmp(p_cpufreq->u.s.scaling_governor,
>> +                           "performance", CPUFREQ_NAME_LEN) )
>> +            printf("cppc policy           : performance\n");
>> +
>> +        else if ( !strncmp(p_cpufreq->u.s.scaling_governor,
>> +                           "powersave", CPUFREQ_NAME_LEN) )
>> +            printf("cppc policy           : powersave\n");
>> +        else
>> +            printf("cppc policy           : unknown\n");
>> +    }
>> +
>> ```
> 
> Something like this is what I was thinking of, yes.

Albeit - why the complicated if/else sequence? Why not simply print
the field the hypercall returned?

Jan