On Thu, Mar 11, 2021 at 10:41:00AM -0500, Liang, Kan wrote: > > > On 3/11/2021 7:34 AM, Peter Zijlstra wrote: > > On Wed, Mar 10, 2021 at 08:37:52AM -0800, [email protected] wrote: > > > @@ -2092,9 +2105,37 @@ static int __init init_hw_perf_events(void) > > > if (err) > > > goto out1; > > > - err = perf_pmu_register(&pmu, "cpu", PERF_TYPE_RAW); > > > - if (err) > > > - goto out2; > > > + if (!is_hybrid()) { > > > + err = perf_pmu_register(&pmu, "cpu", PERF_TYPE_RAW); > > > + if (err) > > > + goto out2; > > > + } else { > > > + u8 cpu_type = get_hybrid_cpu_type(smp_processor_id()); > > > + struct x86_hybrid_pmu *hybrid_pmu; > > > + int i; > > > + > > > + for (i = 0; i < x86_pmu.num_hybrid_pmus; i++) { > > > + hybrid_pmu = &x86_pmu.hybrid_pmu[i]; > > > + > > > + hybrid_pmu->pmu = pmu; > > > + hybrid_pmu->pmu.type = -1; > > > + hybrid_pmu->pmu.attr_update = x86_pmu.attr_update; > > > + hybrid_pmu->pmu.capabilities |= > > > PERF_PMU_CAP_HETEROGENEOUS_CPUS; > > > + > > > + /* Only register the PMU for the boot CPU */ > > > > Why ?! > > > AFAICT we could register them all here. That instantly fixes that > > CPU_STARTING / CPU_DEAD fail elsewhere in this patch. > > It's possible that all CPUs of a certain type all offline, but I cannot know > the information here, because the boot CPU is the only online CPU. I don't > know the status of the other CPUs. > > If we unconditionally register all PMUs, users may see a PMU in > /sys/devices, but they cannot use it, because there is no available CPU. > Is it acceptable that registering an empty PMU?
Sure. That's what it has a cpumask for after all. ISTR that being the case with some dodgy RAPL thing on SPR as well.
