Re: [Xen-devel] [PATCH v3A 2/3] tools/libxc: allow controlling the max C-state sub-state

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.06.14 at 17:02, <Ian.Campbell@xxxxxxxxxx> wrote:
> On Mon, 2014-06-23 at 16:43 +0100, Jan Beulich wrote:
>> --- a/xen/include/public/sysctl.h
>> +++ b/xen/include/public/sysctl.h
>> @@ -354,7 +354,11 @@ struct xen_sysctl_pm_op {
>>      /* set/reset scheduler power saving option */
>>      #define XEN_SYSCTL_pm_op_set_sched_opt_smt    0x21
>>  
>> -    /* cpuidle max_cstate access command */
>> +    /*
>> +     * cpuidle max C-state and max C-sub-state access command:
>> +     * Set cpuid to 0 for max C-state.
>> +     * Set cpuid to 1 for max C-sub-state.
> 
> This seems pretty nasty. Since the sysctl interface is not fixed can't
> we just turn the existing get/set_max_cstate fields into structs? Or
> (less preferably) define C-sub-states to have bit 31 set.
> 
> Can we at least get some named constants instead of 0 and 1?

Any/all of this would be fine with me; what I suggested was merely
an approach with as little changes as possible for an interface that
wasn't defined/implemented well in the first place.

Jan


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