CONFIG_HOTPLUG_CPU is not available for the selected architecture x86.
Result is shown for architecture s390

CONFIG_HOTPLUG_CPU (not configurable)

modulename: hotplug.ko

and/or

hotplug-cpu.ko

and/or

cpu_hotplug.ko

and/or

cpu-hotplug.ko

configname: CONFIG_HOTPLUG_CPU

Linux Kernel Configuration
└─>Processor type and features
└─>HOTPLUG_CPU
In linux kernel since version 2.6.12 )
source code:
arch/arm/mach-imx/hotplug.c