default or selected kernelversion does not have config value CONFIG_GENERIC_SMP_IDLE_THREAD.
Result is shown for kernelversion 6.9-rc5
CONFIG_GENERIC_SMP_IDLE_THREAD (not configurable)
configname: CONFIG_GENERIC_SMP_IDLE_THREAD
Linux Kernel Configuration
└─>General architecture-dependent options
└─>GENERIC_SMP_IDLE_THREAD