Re: [PATCH V2 6/7] perf/x86/intel/uncore: Fix uncore_die_to_cpu() for offline dies

[Mi, Dapeng]

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


On 5/27/2026 11:11 PM, Zide Chen wrote:
> If the die is offline when uncore_die_to_cpu() is called, it silently
> returns 0, which is misleading.  Return -1 in this case to indicate
> that all CPUs on the die are offline and the caller can take care of
> it accordingly.
>
> Opportunistically, replace -EPERM with -ENODEV, as -ENODEV is
> the appropriate error when no CPUs are online across all dies.
>
> Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
> ---
>  arch/x86/events/intel/uncore.c       | 2 +-
>  arch/x86/events/intel/uncore_snbep.c | 9 +++++++--
>  2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
> index 22256ded2d67..4b3a1fa5b41b 100644
> --- a/arch/x86/events/intel/uncore.c
> +++ b/arch/x86/events/intel/uncore.c
> @@ -91,7 +91,7 @@ int uncore_device_to_die(struct pci_dev *dev)
>   */
>  int uncore_die_to_cpu(int die)
>  {
> -	int res = 0, cpu;
> +	int res = -1, cpu;
>  
>  	for_each_online_cpu(cpu) {
>  		if (topology_logical_die_id(cpu) == die) {
> diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c
> index 772b78237424..334dc384b5b9 100644
> --- a/arch/x86/events/intel/uncore_snbep.c
> +++ b/arch/x86/events/intel/uncore_snbep.c
> @@ -3772,12 +3772,17 @@ static void pmu_free_topology(struct intel_uncore_type *type)
>  static int skx_pmu_get_topology(struct intel_uncore_type *type,
>  				 int (*topology_cb)(struct intel_uncore_type*, int, int, u64))
>  {
> -	int die, ret = -EPERM;
> +	int die, ret = -ENODEV;
>  	u64 cpu_bus_msr;
> +	int cpu;
>  
>  	cpus_read_lock();
>  	for (die = 0; die < uncore_max_dies(); die++) {
> -		ret = skx_msr_cpu_bus_read(uncore_die_to_cpu(die), &cpu_bus_msr);
> +		cpu = uncore_die_to_cpu(die);
> +		if (cpu == -1)
> +			continue;
> +
> +		ret = skx_msr_cpu_bus_read(cpu, &cpu_bus_msr);
>  		if (ret)
>  			break;
>