Re: [PATCH V2 5/7] perf/x86/intel/uncore: Move die_to_cpu() to uncore.c

[Mi, Dapeng]

Reviewed-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>


On 5/27/2026 11:11 PM, Zide Chen wrote:
> Move die_to_cpu() into uncore.c so it can be reused by the MSR
> initialization path, preparing for the introduction of an MSR global
> initialization callback.
>
> Move the cpus_read_{lock,unlock}() out of the API, in order to make
> it possible to be called when the lock is being held.
>
> Add the uncore_ prefix for consistency with other uncore APIs.
>
> Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
>
> V2:
> - Move cpus_read_{lock,unlock}() out of uncore_die_to_cpu() and rely
>   on callers to manage the lock. (Sashiko)
> - Remove "No functional change intended" from the changelog.
> ---
>  arch/x86/events/intel/uncore.c       | 19 +++++++++++++++++++
>  arch/x86/events/intel/uncore.h       |  1 +
>  arch/x86/events/intel/uncore_snbep.c | 23 +++--------------------
>  3 files changed, 23 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
> index e9cc1ba921c5..22256ded2d67 100644
> --- a/arch/x86/events/intel/uncore.c
> +++ b/arch/x86/events/intel/uncore.c
> @@ -83,6 +83,25 @@ int uncore_device_to_die(struct pci_dev *dev)
>  	return -1;
>  }
>  
> +/*
> + * Using cpus_read_lock() to ensure cpu is not going down between
> + * looking at cpu_online_mask.
> + *
> + * The lock must be held by the caller.
> + */
> +int uncore_die_to_cpu(int die)
> +{
> +	int res = 0, cpu;
> +
> +	for_each_online_cpu(cpu) {
> +		if (topology_logical_die_id(cpu) == die) {
> +			res = cpu;
> +			break;
> +		}
> +	}
> +	return res;
> +}
> +
>  static void uncore_free_pcibus_map(void)
>  {
>  	struct pci2phy_map *map, *tmp;
> diff --git a/arch/x86/events/intel/uncore.h b/arch/x86/events/intel/uncore.h
> index c35918c01afa..94c68e3417b6 100644
> --- a/arch/x86/events/intel/uncore.h
> +++ b/arch/x86/events/intel/uncore.h
> @@ -235,6 +235,7 @@ struct pci2phy_map *__find_pci2phy_map(int segment);
>  int uncore_pcibus_to_dieid(struct pci_bus *bus);
>  int uncore_die_to_segment(int die);
>  int uncore_device_to_die(struct pci_dev *dev);
> +int uncore_die_to_cpu(int die);
>  
>  ssize_t uncore_event_show(struct device *dev,
>  			  struct device_attribute *attr, char *buf);
> diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c
> index c9ce206fcbb6..772b78237424 100644
> --- a/arch/x86/events/intel/uncore_snbep.c
> +++ b/arch/x86/events/intel/uncore_snbep.c
> @@ -3704,25 +3704,6 @@ static int skx_msr_cpu_bus_read(int cpu, u64 *topology)
>  	return 0;
>  }
>  
> -static int die_to_cpu(int die)
> -{
> -	int res = 0, cpu, current_die;
> -	/*
> -	 * Using cpus_read_lock() to ensure cpu is not going down between
> -	 * looking at cpu_online_mask.
> -	 */
> -	cpus_read_lock();
> -	for_each_online_cpu(cpu) {
> -		current_die = topology_logical_die_id(cpu);
> -		if (current_die == die) {
> -			res = cpu;
> -			break;
> -		}
> -	}
> -	cpus_read_unlock();
> -	return res;
> -}
> -
>  enum {
>  	IIO_TOPOLOGY_TYPE,
>  	UPI_TOPOLOGY_TYPE,
> @@ -3794,8 +3775,9 @@ static int skx_pmu_get_topology(struct intel_uncore_type *type,
>  	int die, ret = -EPERM;
>  	u64 cpu_bus_msr;
>  
> +	cpus_read_lock();
>  	for (die = 0; die < uncore_max_dies(); die++) {
> -		ret = skx_msr_cpu_bus_read(die_to_cpu(die), &cpu_bus_msr);
> +		ret = skx_msr_cpu_bus_read(uncore_die_to_cpu(die), &cpu_bus_msr);
>  		if (ret)
>  			break;
>  
> @@ -3807,6 +3789,7 @@ static int skx_pmu_get_topology(struct intel_uncore_type *type,
>  		if (ret)
>  			break;
>  	}
> +	cpus_read_unlock();
>  
>  	return ret;
>  }