linux-kernel - Re: [RESEND PATCH 05/12] perf/x86: Add config

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Date: Mon, 24 Jun 2024 11:36:28 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: mingo@...nel.org, acme@...nel.org, namhyung@...nel.org,
 irogers@...gle.com, adrian.hunter@...el.com,
 alexander.shishkin@...ux.intel.com, linux-kernel@...r.kernel.org,
 ak@...ux.intel.com, eranian@...gle.com,
 Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: Re: [RESEND PATCH 05/12] perf/x86: Add config_mask to represent
 EVENTSEL bitmask



On 2024-06-24 4:28 a.m., Peter Zijlstra wrote:
> On Fri, Jun 21, 2024 at 02:34:35PM -0400, Liang, Kan wrote:
>>
>>
>> On 2024-06-20 12:16 p.m., Liang, Kan wrote:
>>>
>>>
>>> On 2024-06-20 3:44 a.m., Peter Zijlstra wrote:
>>>> On Tue, Jun 18, 2024 at 08:10:37AM -0700, kan.liang@...ux.intel.com wrote:
>>>>> From: Kan Liang <kan.liang@...ux.intel.com>
>>>>>
>>>>> Different vendors may support different fields in EVENTSEL MSR, such as
>>>>> Intel would introduce new fields umask2 and eq bits in EVENTSEL MSR
>>>>> since Perfmon version 6. However, a fixed mask X86_RAW_EVENT_MASK is
>>>>> used to filter the attr.config.
>>>>>
>>>>
>>>>> @@ -1231,6 +1233,11 @@ static inline int x86_pmu_num_counters_fixed(struct pmu *pmu)
>>>>>  	return hweight64(hybrid(pmu, fixed_cntr_mask64));
>>>>>  }
>>>>>  
>>>>> +static inline u64 x86_pmu_get_event_config(struct perf_event *event)
>>>>> +{
>>>>> +	return event->attr.config & hybrid(event->pmu, config_mask);
>>>>> +}
>>>>
>>>> Seriously, we're going to be having such major event encoding
>>>> differences between cores on a single chip?
>>>
>>> For LNL, no. But ARL-H may have an event encoding differences.
>>> I will double check.
>>
>> There are two generations of e-core on ARL-H. The event encoding is
>> different.
>>
>> The new fields umask2 and eq bits are enumerated by CPUID.(EAX=23H,
>> ECX=0H):EBX. They are supported by CPU 11 but not CPU 12.
>>
>> CPU 11:
>>    0x00000023 0x00: eax=0x0000000f ebx=0x00000003 ecx=0x00000008
>> edx=0x00000000
>> CPU 12:
>>    0x00000023 0x00: eax=0x0000000b ebx=0x00000000 ecx=0x00000006
>> edx=0x00000000
>>
> 
> *groan*...
> 
> So we're going to be having 3 PMUs on that thing I suppose. Oh well.

Yes, 3 PMUs. 1 PMU For p-core. The other 2 PMUs are for two different
types of e-cores.

Thanks,
Kan