Re: [PATCH 3/3] tools/power turbostat: allow turbostat to work when aperf is not available

[David Arcari <darcari@redhat.com>]

On 12/1/25 3:11 PM, Len Brown wrote:
> Something like this?

Yes - this works.  It's actually nice and clean and actually mitigates 
the need for patch 0001.  Clearly an improvement over my patch 3.

How would you like to proceed?  I could resubmit a single v2 patch (with 
an appropriate explanation).

I'd rather not attempt to solve the retry issue.  It's really a second 
order issue and I don't think I'm the appropriate person to do that work.

-DA

> 
> diff --git a/tools/power/x86/turbostat/turbostat.c
> b/tools/power/x86/turbostat/turbostat.c
> index 5bc47ad5da09..4a847e7e9c65 100644
> --- a/tools/power/x86/turbostat/turbostat.c
> +++ b/tools/power/x86/turbostat/turbostat.c
> @@ -8530,7 +8530,7 @@ void rapl_perf_init(void)
>   /* Assumes msr_counter_info is populated */
>   static int has_amperf_access(void)
>   {
> -       return msr_counter_arch_infos[MSR_ARCH_INFO_APERF_INDEX].present &&
> +       return has_aperf &&
> msr_counter_arch_infos[MSR_ARCH_INFO_APERF_INDEX].present &&
>              msr_counter_arch_infos[MSR_ARCH_INFO_MPERF_INDEX].present;
>   }
> 
> 
> On Mon, Dec 1, 2025 at 2:53 PM Len Brown <lenb@kernel.org> wrote:
>>
>>> ...add_msr_perf_counter() returns -1
>>
>> good.  and then add_msr_counter() succeeds because...
>>
>>> rdmsr returns zero for MSR_IA32_APERF and MSR_IA32_MPERF.
>>
>> Your patch is a good suggestion -- though it checks for APERF only and
>> not for MPERF.
>>
>> We already ran CPUID and cleared has_aperf, so I'm thinking we should
>> be heading this off earlier.  Let me send you a test patch later today.
>>
>> thanks,
>> Len Brown, Intel Open Source Technology Center
> 
> 
>