CONFIG_S390_IOMMU (not configurable)

modulename: s390-iommu.ko

configname: CONFIG_S390_IOMMU

Linux Kernel Configuration
└─>Device Drivers
└─>IOMMU Hardware Support
└─>PCI support
└─>S390_IOMMU
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Support for the IOMMU API for s390 PCI devices.

source code: