KVM에서 EPT 는 Guest OS가 gfn을 access할 때,
VM Exit가 발생하며, 이에 매칭되는 pfn을 생성한다.
I have tried to log EPT construction status at VM startup, that is to
add some codes in function __direct_map (arch/x86/kvm/mmu.c).
__direct_map constructs the EPT paging structure when a guest page
firstly touched, and I can get related gfn and pfn here.