Re: [PATCH 7/7] perf/x86/intel/uncore: Implement lazy setup for MSR/MMIO PMU

["Mi, Dapeng" <dapeng1.mi@linux.intel.com>]

On 5/13/2026 7:30 AM, Zide Chen wrote:
> MSR and MMIO uncore PMUs are currently registered at module init time
> and appear in sysfs even when no PMU boxes are functional.
>
> Apply the same lazy registration model used by PCI uncore PMUs: the
> PMU is registered when the first box is successfully initialized, and
> unregistered when the last box exits.  If a box fails to initialize on
> a subsequent die, the PMU is marked broken but remains registered to
> avoid disrupting any in-flight perf events.
>
> Box allocation and free remain at module init/exit time to avoid
> repeated kfree/alloc cycles across CPU offline/online events.
>
> Signed-off-by: Zide Chen <zide.chen@intel.com>
> ---
>  arch/x86/events/intel/uncore.c | 72 ++++++----------------------------
>  1 file changed, 12 insertions(+), 60 deletions(-)
>
> diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
> index 399f434e1a7d..2aaac0b49bb6 100644
> --- a/arch/x86/events/intel/uncore.c
> +++ b/arch/x86/events/intel/uncore.c
> @@ -1564,8 +1564,11 @@ static void uncore_box_unref(struct intel_uncore_type **types, int die)
>  		for (i = 0; i < type->num_boxes; i++, pmu++) {
>  			box = pmu->boxes[die];
>  			if (box && box->cpu >= 0 &&
> -			    atomic_dec_return(&box->cpu_refcnt) == 0)
> +			    atomic_dec_return(&box->cpu_refcnt) == 0) {
> +				if (atomic_dec_return(&pmu->die_refcnt) == 0)
> +					uncore_pmu_unregister(pmu);
>  				uncore_box_exit(box);
> +			}
>  		}
>  	}
>  }
> @@ -1659,7 +1662,7 @@ static int uncore_box_ref(struct intel_uncore_type **types,
>  			box = pmu->boxes[die];
>  			if (box && box->cpu >= 0 &&
>  			    atomic_inc_return(&box->cpu_refcnt) == 1)
> -				uncore_box_init(box);
> +				uncore_box_setup(pmu, box);
>  		}
>  	}
>  	return 0;
> @@ -1690,67 +1693,16 @@ static int uncore_event_cpu_online(unsigned int cpu)
>  	return 0;
>  }
>  
> -static int __init type_pmu_register(struct intel_uncore_type *type)
> +static int __init uncore_cpu_mmio_init(struct intel_uncore_type **types)

The name seems a little bit weird, could we name it to a more generic name?
maybe uncore_pmu_types_init() or something similar? Thanks.


>  {
> -	int i, ret;
> -
> -	for (i = 0; i < type->num_boxes; i++) {
> -		ret = uncore_pmu_register(&type->pmus[i]);
> -		if (ret)
> -			return ret;
> -	}
> -	return 0;
> -}
> -
> -static int __init uncore_msr_pmus_register(void)
> -{
> -	struct intel_uncore_type **types = uncore_msr_uncores;
> -	int ret;
> -
> -	for (; *types; types++) {
> -		ret = type_pmu_register(*types);
> -		if (ret)
> -			return ret;
> -	}
> -	return 0;
> -}
> -
> -static int __init uncore_cpu_init(void)
> -{
> -	int ret;
> -
> -	ret = uncore_types_init(uncore_msr_uncores);
> -	if (ret)
> -		goto err;
> -
> -	ret = uncore_msr_pmus_register();
> -	if (ret)
> -		goto err;
> -	return 0;
> -err:
> -	uncore_types_exit(uncore_msr_uncores);
> -	uncore_msr_uncores = empty_uncore;
> -	return ret;
> -}
> -
> -static int __init uncore_mmio_init(void)
> -{
> -	struct intel_uncore_type **types = uncore_mmio_uncores;
>  	int ret;
>  
>  	ret = uncore_types_init(types);
> -	if (ret)
> -		goto err;
> +	if (!ret)
> +		return 0;
>  
> -	for (; *types; types++) {
> -		ret = type_pmu_register(*types);
> -		if (ret)
> -			goto err;
> -	}
> -	return 0;
> -err:
> -	uncore_types_exit(uncore_mmio_uncores);
> -	uncore_mmio_uncores = empty_uncore;
> +	uncore_types_exit(types);
> +	types = empty_uncore;
>  	return ret;
>  }
>  
> @@ -2052,12 +2004,12 @@ static int __init intel_uncore_init(void)
>  
>  	if (uncore_init->cpu_init) {
>  		uncore_init->cpu_init();
> -		cret = uncore_cpu_init();
> +		cret = uncore_cpu_mmio_init(uncore_msr_uncores);
>  	}
>  
>  	if (uncore_init->mmio_init) {
>  		uncore_init->mmio_init();
> -		mret = uncore_mmio_init();
> +		mret = uncore_cpu_mmio_init(uncore_mmio_uncores);
>  	}
>  
>  	if (cret && pret && mret) {