linux-kernel - Re: [RFC v2] perf: Rewrite core context handling

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Date:   Wed, 24 Aug 2022 14:15:13 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ravi Bangoria <ravi.bangoria@....com>
Cc:     acme@...nel.org, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, namhyung@...nel.org, songliubraving@...com,
        eranian@...gle.com, alexey.budankov@...ux.intel.com,
        ak@...ux.intel.com, mark.rutland@....com, megha.dey@...el.com,
        frederic@...nel.org, maddy@...ux.ibm.com, irogers@...gle.com,
        kim.phillips@....com, linux-kernel@...r.kernel.org,
        santosh.shukla@....com
Subject: Re: [RFC v2] perf: Rewrite core context handling

On Mon, Jun 13, 2022 at 04:35:11PM +0200, Peter Zijlstra wrote:
>  void x86_pmu_update_cpu_context(struct pmu *pmu, int cpu)
>  {
> -	struct perf_cpu_context *cpuctx;
> +	/* XXX: Don't need this quirk anymore */
> +	/*struct perf_cpu_context *cpuctx;
>  
>  	if (!pmu->pmu_cpu_context)
>  		return;
>  
>  	cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
> -	cpuctx->ctx.pmu = pmu;
> +	cpuctx->ctx.pmu = pmu;*/
>  }

Confirmed; my ADL seems to work fine without all that.

---
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index fd043cd0e3c9..7a2d12ad6d1f 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2059,24 +2059,6 @@ void x86_pmu_show_pmu_cap(int num_counters, int num_counters_fixed,
 	pr_info("... event mask:             %016Lx\n", intel_ctrl);
 }
 
-/*
- * The generic code is not hybrid friendly. The hybrid_pmu->pmu
- * of the first registered PMU is unconditionally assigned to
- * each possible cpuctx->ctx.pmu.
- * Update the correct hybrid PMU to the cpuctx->ctx.pmu.
- */
-void x86_pmu_update_cpu_context(struct pmu *pmu, int cpu)
-{
-	/* XXX: Don't need this quirk anymore */
-	/*struct perf_cpu_context *cpuctx;
-
-	if (!pmu->pmu_cpu_context)
-		return;
-
-	cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
-	cpuctx->ctx.pmu = pmu;*/
-}
-
 static int __init init_hw_perf_events(void)
 {
 	struct x86_pmu_quirk *quirk;
@@ -2197,9 +2179,6 @@ static int __init init_hw_perf_events(void)
 						(hybrid_pmu->cpu_type == hybrid_big) ? PERF_TYPE_RAW : -1);
 			if (err)
 				break;
-
-			if (cpu_type == hybrid_pmu->cpu_type)
-				x86_pmu_update_cpu_context(&hybrid_pmu->pmu, raw_smp_processor_id());
 		}
 
 		if (i < x86_pmu.num_hybrid_pmus) {
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 8a72e6fe27a5..768771e5e4e9 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -4508,8 +4508,6 @@ static bool init_hybrid_pmu(int cpu)
 	cpumask_set_cpu(cpu, &pmu->supported_cpus);
 	cpuc->pmu = &pmu->pmu;
 
-	x86_pmu_update_cpu_context(&pmu->pmu, cpu);
-
 	return true;
 }
 
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 94fb65d7b291..9c835ecb232e 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -1175,8 +1175,6 @@ int x86_pmu_handle_irq(struct pt_regs *regs);
 void x86_pmu_show_pmu_cap(int num_counters, int num_counters_fixed,
 			  u64 intel_ctrl);
 
-void x86_pmu_update_cpu_context(struct pmu *pmu, int cpu);
-
 extern struct event_constraint emptyconstraint;
 
 extern struct event_constraint unconstrained;