default or selected kernelversion does not have config value CONFIG_CXL_BASE.
Result is shown for kernelversion 6.9.9

CONFIG_CXL_BASE (not configurable)

modulename: pci-cxl.ko

and/or

base.ko

configname: CONFIG_CXL_BASE

Linux Kernel Configuration
└─>Device Drivers
└─>Misc devices
└─>CXL_BASE
In linux kernel since version 3.10 (release Date: 2013-06-30)  
source code:
arch/powerpc/platforms/powernv/pci-cxl.c

is depended by
CONFIG_CXL