linux-kernel - Re: [PATCH v6 03/10] perf/x86/rapl: Remove the cpu_to_rapl

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Message-ID: <52e578d0-a885-4d6c-836d-fc3ec0f491b2@amd.com>
Date: Mon, 28 Oct 2024 14:49:13 +0530
From: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
To: "Gautham R. Shenoy" <gautham.shenoy@....com>
Cc: peterz@...radead.org, mingo@...hat.com, rui.zhang@...el.com,
 acme@...nel.org, namhyung@...nel.org, mark.rutland@....com,
 alexander.shishkin@...ux.intel.com, jolsa@...nel.org, irogers@...gle.com,
 adrian.hunter@...el.com, kan.liang@...ux.intel.com, tglx@...utronix.de,
 bp@...en8.de, dave.hansen@...ux.intel.com, ananth.narayan@....com,
 kprateek.nayak@....com, ravi.bangoria@....com, x86@...nel.org,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 03/10] perf/x86/rapl: Remove the cpu_to_rapl_pmu()
 function

Hello Gautham,

On 10/28/2024 2:23 PM, Gautham R. Shenoy wrote:
> Hello Dhananjay,
> 
> On Fri, Oct 25, 2024 at 11:13:41AM +0000, Dhananjay Ugwekar wrote:
>> Prepare for the addition of RAPL core energy counter support.
>> Post which, one CPU might be mapped to more than one rapl_pmu
>> (package/die one and a core one). So, remove the cpu_to_rapl_pmu()
>> function.
>>
>> Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
>> ---
>>  arch/x86/events/rapl.c | 19 ++++++-------------
>>  1 file changed, 6 insertions(+), 13 deletions(-)
>>
>> diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
>> index f70c49ca0ef3..d20c5b1dd0ad 100644
>> --- a/arch/x86/events/rapl.c
>> +++ b/arch/x86/events/rapl.c
>> @@ -162,17 +162,6 @@ static inline unsigned int get_rapl_pmu_idx(int cpu)
>>  					 topology_logical_die_id(cpu);
>>  }
>>  
>> -static inline struct rapl_pmu *cpu_to_rapl_pmu(unsigned int cpu)
>> -{
>> -	unsigned int rapl_pmu_idx = get_rapl_pmu_idx(cpu);
>> -
>> -	/*
>> -	 * The unsigned check also catches the '-1' return value for non
>> -	 * existent mappings in the topology map.
>> -	 */
> 
> 
> See the comment here why rapl_pmu_idx should be an "unsigned int".
> 
> 
>> -	return rapl_pmu_idx < rapl_pmus->nr_rapl_pmu ? rapl_pmus->pmus[rapl_pmu_idx] : NULL;
>> -}
>> -
>>  static inline u64 rapl_read_counter(struct perf_event *event)
>>  {
>>  	u64 raw;
>> @@ -348,7 +337,7 @@ static void rapl_pmu_event_del(struct perf_event *event, int flags)
>>  static int rapl_pmu_event_init(struct perf_event *event)
>>  {
>>  	u64 cfg = event->attr.config & RAPL_EVENT_MASK;
>> -	int bit, ret = 0;
>> +	int bit, rapl_pmu_idx, ret = 0;
> 
> Considering that, shouldn't rapl_pmu_idx be an "unsigned int" no?

Correct, with unsigned int we will be able to check for negative values as well with the 
"if (rapl_pmu_idx >= rapl_pmus->nr_rapl_pmu)" check. Will fix this in next version.

Thanks,
Dhananjay

> 
> --
> Thanks and Regards
> gautham.
> 
> 
>>  	struct rapl_pmu *pmu;
>>  
>>  	/* only look at RAPL events */
>> @@ -376,8 +365,12 @@ static int rapl_pmu_event_init(struct perf_event *event)
>>  	if (event->attr.sample_period) /* no sampling */
>>  		return -EINVAL;
>>  
>> +	rapl_pmu_idx = get_rapl_pmu_idx(event->cpu);
>> +	if (rapl_pmu_idx >= rapl_pmus->nr_rapl_pmu)
>> +		return -EINVAL;
>> +
>>  	/* must be done before validate_group */
>> -	pmu = cpu_to_rapl_pmu(event->cpu);
>> +	pmu = rapl_pmus->pmus[rapl_pmu_idx];
>>  	if (!pmu)
>>  		return -EINVAL;
>>  	event->pmu_private = pmu;
>> -- 
>> 2.34.1
>>