Re: [PATCH v4 3/7] perf/x86/amd/core: Detect PerfMonV2 support

[Sandipan Das]

On 5/9/2022 6:31 PM, Like Xu wrote:
> On 27/4/2022 7:31 pm, Sandipan Das wrote:
> 
>>       x86_pmu.num_counters    = AMD64_NUM_COUNTERS_CORE;
> 
> Thus boot_cpu_has(X86_FEATURE_PERFCTR_CORE) is true.
> 
>> +
>> +    /* Check for Performance Monitoring v2 support */
>> +    if (boot_cpu_has(X86_FEATURE_PERFMON_V2)) {
>> +        /* Update PMU version for later usage */
>> +        x86_pmu.version = 2;
> 
> Is it safe to assume that once AMD CPU has the PERFMON_V2 (or further) bit,
> 
> it must also have the PERFCTR_CORE bit set ?
> 

Yes, always. There won't be a case where PERFCTR_CORE is absent
but PERFMON_V2 is present.

- Sandipan