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

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Date: Mon, 1 Jul 2024 15:02:32 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
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

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.