[PATCH v1 2/4] powerpc/64s/perf: add power_pmu_running to query whether perf is being used

[Madhavan Srinivasan]

On 8/16/21 12:59 PM, Nicholas Piggin wrote:
> Interrupt handling code would like to know whether perf is enabled, to
> know whether it should enable MSR[EE] to improve PMI coverage.
>
> Cc: Madhavan Srinivasan <maddy at linux.ibm.com>
> Cc: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>   arch/powerpc/include/asm/hw_irq.h |  2 ++
>   arch/powerpc/perf/core-book3s.c   | 13 +++++++++++++
>   2 files changed, 15 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
> index 21cc571ea9c2..2d5c0d3ccbb6 100644
> --- a/arch/powerpc/include/asm/hw_irq.h
> +++ b/arch/powerpc/include/asm/hw_irq.h
> @@ -306,6 +306,8 @@ static inline bool lazy_irq_pending_nocheck(void)
>   	return __lazy_irq_pending(local_paca->irq_happened);
>   }
>   
> +bool power_pmu_running(void);
> +
>   /*
>    * This is called by asynchronous interrupts to conditionally
>    * re-enable hard interrupts after having cleared the source
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index bb0ee716de91..76114a9afb2b 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -2380,6 +2380,19 @@ static void perf_event_interrupt(struct pt_regs *regs)
>   	perf_sample_event_took(sched_clock() - start_clock);
>   }
>   
> +bool power_pmu_running(void)
> +{
> +	struct cpu_hw_events *cpuhw;
> +
> +	/* Could this simply test local_paca->pmcregs_in_use? */
> +
> +	if (!ppmu)
> +		return false;


This covers only when perf platform driver is not registered,
but we should also check for MMCR0[32], since pmu sprs can be
accessed via sysfs.

Maddy


> +
> +	cpuhw = this_cpu_ptr(&cpu_hw_events);
> +	return cpuhw->n_events;
> +}
> +
>   static int power_pmu_prepare_cpu(unsigned int cpu)
>   {
>   	struct cpu_hw_events *cpuhw = &per_cpu(cpu_hw_events, cpu);