Changlog v2:
- when level is PT_DIRECTORY_LEVEL, the 'offset' should be
'role.quadrant << 8', thanks Avi for point it out
- keep invlpg code in paging_tmpl.h address Avi's suggestion
- split kvm_sync_page() into kvm_sync_page() and kvm_sync_page_transient()
to clarify the code address Avi's suggestion