PV_MOD4M
#define MR4M(pte) (((pte) >> PG_M_SHIFT4M) & (PV_MOD4M | PV_REF4M))
rv = VM_MDPAGE_PVHEAD(pg)->pv_flags & PV_MOD4M;
VM_MDPAGE_PVHEAD(pg)->pv_flags &= ~PV_MOD4M;
return (VM_MDPAGE_PVHEAD(pg)->pv_flags & PV_MOD4M ||
pv_syncflags4m(pg) & PV_MOD4M);