CONFIG_IA64_XEN_GUEST is not available for thedefaultarchitecture x86.
Result is shown for architecture ia64
default or selected kernelversion does not have config value CONFIG_IA64_XEN_GUEST.
Result is shown for kernelversion 6.5.1

Xen guest

configname: CONFIG_IA64_XEN_GUEST

System type
└─>Xen guest
In linux kernel since version 2.6.28 (release Date: 2008-12-24)  
Build a kernel that runs on Xen guest domain. At this moment only
16KB page size in supported.

selects
CONFIG_SWIOTLB

depends
CONFIG_XEN