CONFIG_VIRTUAL_MEM_MAP is not available for thedefaultarchitecture x86.
Result is shown for architecture ia64

Virtual mem map

configname: CONFIG_VIRTUAL_MEM_MAP

IA-64 Linux Kernel Configuration
└─>Processor type and features
└─>Virtual mem map
In linux kernel since version 2.6.12  
Say Y to compile the kernel with support for a virtual mem map.
This code also only takes effect if a memory hole of greater than
1 Gb is found during boot. You must turn this option on if you
require the DISCONTIGMEM option for your machine. If you are
unsure, say Y.

depends
 or  NOT CONFIG_SPARSEMEM