CONFIG_ARCH_S390_31 is not available for thedefaultarchitecture x86.
Result is shown for architecture s390

CONFIG_ARCH_S390_31 (not configurable)

modulename: entry.ko

configname: CONFIG_ARCH_S390_31

Linux Kernel Configuration
└─>Base setup
└─>ARCH_S390_31
In linux kernel since version 2.6.12  
source code:
arch/s390/kernel/