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

CONFIG_CPU_SUPPORTS_HIGHMEM (not configurable)

configname: CONFIG_CPU_SUPPORTS_HIGHMEM

Linux Kernel Configuration
└─>Kernel type
└─>CPU_SUPPORTS_HIGHMEM
In linux kernel since version 2.6.15 (release Date: 2006-01-02)