Re: [PATCH] x86/events/amd/iommu: Fix cpumask of IOMMU events

["Jörg Rödel" <joro@8bytes.org>]

On Sun, May 17, 2026 at 11:40:26AM +0000, Vasant Hegde wrote:
> IOMMU performance counters are accessed via MMIO space. Currently IOMMU
> PMUs uses a single global cpumask (iommu_cpumask) shared across all AMD
> IOMMU PMU instances. This prevents collecting per-socket numbers
> (ex: perf stat --per-socket).
> 
> Fix this by adjusting cpumask based on IOMMUs NUMA node.
> 
> Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>

Acked-by: Joerg Roedel <joerg.roedel@amd.com>

> ---
>  arch/x86/events/amd/iommu.c | 29 +++++++++++++++++++++++------
>  drivers/iommu/amd/init.c    |  7 +++++++
>  include/linux/amd-iommu.h   |  1 +
>  3 files changed, 31 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/events/amd/iommu.c b/arch/x86/events/amd/iommu.c
> index 07b110e8418a..b1848300028d 100644
> --- a/arch/x86/events/amd/iommu.c
> +++ b/arch/x86/events/amd/iommu.c
> @@ -10,6 +10,7 @@
>  
>  #define pr_fmt(fmt)	"perf/amd_iommu: " fmt
>  
> +#include <linux/device.h>
>  #include <linux/perf_event.h>
>  #include <linux/init.h>
>  #include <linux/cpumask.h>
> @@ -43,6 +44,7 @@ struct perf_amd_iommu {
>  	u8 max_counters;
>  	u64 cntr_assign_mask;
>  	raw_spinlock_t lock;
> +	cpumask_t cpumask;
>  };
>  
>  static LIST_HEAD(perf_amd_iommu_list);
> @@ -131,13 +133,15 @@ static struct amd_iommu_event_desc amd_iommu_v2_event_descs[] = {
>  /*---------------------------------------------
>   * sysfs cpumask attributes
>   *---------------------------------------------*/
> -static cpumask_t iommu_cpumask;
> -
>  static ssize_t _iommu_cpumask_show(struct device *dev,
>  				   struct device_attribute *attr,
>  				   char *buf)
>  {
> -	return cpumap_print_to_pagebuf(true, buf, &iommu_cpumask);
> +	struct pmu *pmu = dev_get_drvdata(dev);
> +	struct perf_amd_iommu *perf_iommu =
> +			container_of(pmu, struct perf_amd_iommu, pmu);
> +
> +	return cpumap_print_to_pagebuf(true, buf, &perf_iommu->cpumask);
>  }
>  static DEVICE_ATTR(cpumask, S_IRUGO, _iommu_cpumask_show, NULL);
>  
> @@ -420,7 +424,8 @@ static const struct pmu iommu_pmu __initconst = {
>  static __init int init_one_iommu(unsigned int idx)
>  {
>  	struct perf_amd_iommu *perf_iommu;
> -	int ret;
> +	struct device *dev;
> +	int node, cpu, ret;
>  
>  	perf_iommu = kzalloc_obj(struct perf_amd_iommu);
>  	if (!perf_iommu)
> @@ -440,6 +445,20 @@ static __init int init_one_iommu(unsigned int idx)
>  		return -EINVAL;
>  	}
>  
> +	dev = amd_iommu_idx_to_dev(idx);
> +	node = dev ? dev_to_node(dev) : NUMA_NO_NODE;
> +	if (node != NUMA_NO_NODE)
> +		cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
> +	else
> +		cpu = cpumask_any(cpu_online_mask);
> +
> +	if (cpu >= nr_cpu_ids) {
> +		pr_warn("Failed to find online CPU for IOMMU %d.\n", idx);
> +		kfree(perf_iommu);
> +		return -ENODEV;
> +	}
> +	cpumask_set_cpu(cpu, &perf_iommu->cpumask);
> +
>  	snprintf(perf_iommu->name, IOMMU_NAME_SIZE, "amd_iommu_%u", idx);
>  
>  	ret = perf_pmu_register(&perf_iommu->pmu, perf_iommu->name, -1);
> @@ -483,8 +502,6 @@ static __init int amd_iommu_pc_init(void)
>  		return -ENODEV;
>  	}
>  
> -	/* Init cpumask attributes to only core 0 */
> -	cpumask_set_cpu(0, &iommu_cpumask);
>  	return 0;
>  }
>  
> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
> index 3bdb380d23e9..2c35d171b5ae 100644
> --- a/drivers/iommu/amd/init.c
> +++ b/drivers/iommu/amd/init.c
> @@ -3939,6 +3939,13 @@ struct amd_iommu *get_amd_iommu(unsigned int idx)
>  	return NULL;
>  }
>  
> +struct device *amd_iommu_idx_to_dev(unsigned int idx)
> +{
> +	struct amd_iommu *iommu = get_amd_iommu(idx);
> +
> +	return iommu ? &iommu->dev->dev : NULL;
> +}
> +
>  /****************************************************************************
>   *
>   * IOMMU EFR Performance Counter support functionality. This code allows
> diff --git a/include/linux/amd-iommu.h b/include/linux/amd-iommu.h
> index edcee9f5335a..6b8d6b53b4e9 100644
> --- a/include/linux/amd-iommu.h
> +++ b/include/linux/amd-iommu.h
> @@ -67,6 +67,7 @@ int amd_iommu_pc_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr, u8 fxn,
>  int amd_iommu_pc_get_reg(struct amd_iommu *iommu, u8 bank, u8 cntr, u8 fxn,
>  		u64 *value);
>  struct amd_iommu *get_amd_iommu(unsigned int idx);
> +struct device *amd_iommu_idx_to_dev(unsigned int idx);
>  
>  #ifdef CONFIG_KVM_AMD_SEV
>  int amd_iommu_snp_disable(void);
> -- 
> 2.31.1
>