CONFIG_CPU_LOONGSON2EF is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_CPU_LOONGSON2EF (not configurable)

configname: CONFIG_CPU_LOONGSON2EF

Linux Kernel Configuration
└─>CPU selection
└─>CPU_LOONGSON2EF
In linux kernel since version 4.14.326 (release Date: 2023-09-23)