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

[Vasant Hegde <vasant.hegde@amd.com>]

On 5/17/2026 5:42 PM, sashiko-bot@kernel.org wrote:

> 
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [High] PMU initialization fails for IOMMUs located on NUMA nodes without online CPUs.
> --
> 

Thanks for the review.

> commit ef1363d0a37870d7cf1f1095cd3ebf42cc5a8bdc
> Author: Vasant Hegde <vasant.hegde@amd.com>
> 
> x86/events/amd/iommu: Fix cpumask of IOMMU events
> 
> This commit changes the IOMMU PMU cpumask from a single global mask to a
> per-IOMMU mask based on the NUMA node of the IOMMU, allowing per-socket
> performance counter collection.
> 
>> diff --git a/arch/x86/events/amd/iommu.c b/arch/x86/events/amd/iommu.c
>> --- a/arch/x86/events/amd/iommu.c
>> +++ b/arch/x86/events/amd/iommu.c
> [ ... ]
>> @@ -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);
> 
> If the IOMMU resides on a CPU-less NUMA node (like a PCIe expansion switch
> or a memory-only CXL node), or if all CPUs on that node are currently
> offline, will cpumask_any_and() return a value greater than or equal to
> nr_cpu_ids?

If its CPU-less then put it back to CPU 0? Any suggestions ?

-Vasant