CONFIG_ARM_VIRT_EXT is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_ARM_VIRT_EXT (not configurable)

modulename: hyp-stub.ko

configname: CONFIG_ARM_VIRT_EXT

Linux Kernel Configuration
└─>ARM_VIRT_EXT
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Enable the kernel to make use of the ARM Virtualization
Extensions to install hypervisors without run-time firmware
assistance.

A compliant bootloader is required in order to make maximum
use of this feature. Refer to Documentation/arch/arm/booting.rst for
details.

source code: