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SubjectRe: [PATCH 1/4] perf/x86/intel/lbr: use setup_clear_cpu_cap instead of clear_cpu_cap
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On 6/22/2022 2:57 PM, Liang, Kan wrote:
>
>
> On 6/22/2022 10:58 AM, Dave Hansen wrote:
>> On 6/22/22 07:48, Maxim Levitsky wrote:
>>> clear_cpu_cap(&boot_cpu_data) is very similar to setup_clear_cpu_cap
>>> except that the latter also sets a bit in 'cpu_caps_cleared' which
>>> later clears the same cap in secondary cpus, which is likely
>>> what is meant here.
>>>
>>> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
>>
>> Seems like a:
>>
>> Fixes: 47125db27e47 ("perf/x86/intel/lbr: Support Architectural LBR")
>>
>> would be in order.
>>
>> Kan, does this change look right to you?
>
> For the current implementation, the Arch LBR feature should be either
> supported by all the CPUs or disabled on all the CPUs. It cannot be only
> enabled for partial CPUs, even in a hybrid platform.
> So the current code only check the boot CPU via static_cpu_has().
>
> Ideally, Yes, I think it may be better to clear the bit for all CPUs,
> which makes the capability consistent among CPUs.
>

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>

Thanks,
Kan


> Thanks,
> Kan
>>
>>>   arch/x86/events/intel/lbr.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
>>> index 13179f31fe10fa..b08715172309a7 100644
>>> --- a/arch/x86/events/intel/lbr.c
>>> +++ b/arch/x86/events/intel/lbr.c
>>> @@ -1860,7 +1860,7 @@ void __init intel_pmu_arch_lbr_init(void)
>>>       return;
>>>   clear_arch_lbr:
>>> -    clear_cpu_cap(&boot_cpu_data, X86_FEATURE_ARCH_LBR);
>>> +    setup_clear_cpu_cap(X86_FEATURE_ARCH_LBR);
>>>   }
>>>   /**
>>

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