linux-hardening - Re: [PATCH v3 05/10] perf/x86/rapl: Move cpumask variable to rapl

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Message-ID: <1dec4dbb-e64a-40ad-8160-68326f0e31d0@amd.com>
Date: Tue, 2 Jul 2024 15:46:31 +0530
From: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: mingo@...hat.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,
 x86@...nel.org, kees@...nel.org, gustavoars@...nel.org, rui.zhang@...el.com,
 oleksandr@...alenko.name, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
 ananth.narayan@....com, gautham.shenoy@....com, kprateek.nayak@....com,
 ravi.bangoria@....com, sandipan.das@....com, linux-pm@...r.kernel.org
Subject: Re: [PATCH v3 05/10] perf/x86/rapl: Move cpumask variable to
 rapl_pmus struct

Hello Peter,

On 7/1/2024 6:32 PM, Peter Zijlstra wrote:
> On Mon, Jun 24, 2024 at 05:59:02AM +0000, Dhananjay Ugwekar wrote:
>> This patch is in preparation for addition of per-core energy counter
>> support for AMD CPUs.
>>
>> Per-core energy counter PMU will need a separate cpumask. It seems like
>> a better approach to add the cpumask inside the rapl_pmus struct, instead
>> of creating another global cpumask variable for per-core PMU. This way, in
>> future, if there is a need for a new PMU with a different scope (e.g. CCD),
>> adding a new global cpumask variable won't be necessary.
>>
>> No functional change.
>>
>> Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
>> ---
>>  arch/x86/events/rapl.c | 12 ++++++------
>>  1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
>> index e5e878146542..be139e9f9ee0 100644
>> --- a/arch/x86/events/rapl.c
>> +++ b/arch/x86/events/rapl.c
>> @@ -119,6 +119,7 @@ struct rapl_pmu {
>>  
>>  struct rapl_pmus {
>>  	struct pmu		pmu;
>> +	cpumask_t		cpumask;
>>  	unsigned int		nr_rapl_pmu;
>>  	struct rapl_pmu		*rapl_pmu[] __counted_by(nr_rapl_pmu);
>>  };
> 
> Yikes no, please use cpumask_var_t and alloc_cpumask_var() and friends.

Ah yes!, I did not know about this API, will use this in the next version.

Thanks,
Dhananjay