RADIX_PTE_INDEX_SIZE    8 arch/powerpc/include/asm/book3s/64/radix-4k.h #define RADIX_PTE_INDEX_SIZE   9  // size: 8B <<  9 =  4KB, maps 2^9  x    4K =   2MB
RADIX_PTE_INDEX_SIZE    8 arch/powerpc/include/asm/book3s/64/radix-64k.h #define RADIX_PTE_INDEX_SIZE   5  // size: 8B <<  5 = 256B, maps 2^5  x   64K =   2MB