CONFIG_MEMORY_HOTPLUG_SPARSE (not configurable)

modulename: memory.ko

configname: CONFIG_MEMORY_HOTPLUG_SPARSE

Linux Kernel Configuration
└─>MEMORY_HOTPLUG_SPARSE
In linux kernel since version 2.6.19 (release Date: 2006-11-29)  
source code:
drivers/base//memory.c

is selected by
CONFIG_VIRTIO_MEM