CONFIG_MACH_LOONGSON64 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

Loongson-2/3 family of machines

configname: CONFIG_MACH_LOONGSON64

System type
└─>Loongson-2/3 family of machines
In linux kernel since version 3.10 (release Date: 2013-06-30)  
This enables the support of Loongson-2/3 family of machines.

Loongson-2 is a family of single-core CPUs and Loongson-3 is a
family of multi-core CPUs. They are both 64-bit general-purpose
MIPS-compatible CPUs. Loongson-2/3 are developed by the Institute
of Computing Technology (ICT), Chinese Academy of Sciences (CAS)
in the People's Republic of China. The chief architect is Professor
Weiwu Hu.


is selected by
CONFIG_SWIOTLB