CONFIG_KVM_GUEST is not available for the selected architecture x86.
Result is shown for architecture mips

KVM Guest Kernel

modulename: kvm.ko

configname: CONFIG_KVM_GUEST

Linux Kernel Configuration
└─>Kernel type
└─>KVM Guest Kernel
In linux kernel since version 2.6.26 (release Date: 2008-07-13)
Select this option if building a guest kernel for KVM (Trap & Emulate)
mode.
source code:
depends
CONFIG_BROKEN_ON_SMP
CONFIG_CPU_MIPS32_R2