CONFIG_SWIOTLB_XEN (not configurable)

modulename: pci-swiotlb-xen.ko

and/or

swiotlb-xen.ko

configname: CONFIG_SWIOTLB_XEN

Linux Kernel Configuration
└─>Device Drivers
└─>Xen driver support
└─>SWIOTLB_XEN
In linux kernel since version 2.6.36 (release Date: 2010-10-20)  
source code:
arch/x86/xen/pci-swiotlb-xen.c
selects
CONFIG_SWIOTLB

depends
CONFIG_XEN

is depended by
CONFIG_XEN
CONFIG_PCI_XEN