p4d_flags
return p4d_flags(p4d) & _PAGE_PRESENT;
return (p4d_flags(p4d) & ~ignore_flags) != 0;
#define p4d_pgprot(x) __pgprot(p4d_flags(x))
*nx |= p4d_flags(*p4d) & _PAGE_NX;
*rw &= p4d_flags(*p4d) & _PAGE_RW;