PT_FIRST_AVAIL_BITS_SHIFT  183 arch/x86/kvm/mmu.c #define SPTE_HOST_WRITEABLE	(1ULL << PT_FIRST_AVAIL_BITS_SHIFT)
PT_FIRST_AVAIL_BITS_SHIFT  184 arch/x86/kvm/mmu.c #define SPTE_MMU_WRITEABLE	(1ULL << (PT_FIRST_AVAIL_BITS_SHIFT + 1))