Vol. 3A 4-25
PAGING
Table 4-16. Format of an IA-32e Page-Directory-Pointer-Table Entry (PDPTE) that References a Page Directory
Bit
Position(s)
Contents
0 (P)
Present; must be 1 to reference a page directory
1 (R/W)
Read/write; if 0, writes may not be allowed to the 1-GByte region controlled by this entry (see Section 4.6)
2 (U/S)
User/supervisor; if 0, user-mode accesses are not allowed to the 1-GByte region controlled by this entry (see Section
3 (PWT)
Page-level write-through; indirectly determines the memory type used to access the page directory referenced by
this entry (see Section 4.9.2)
4 (PCD)
Page-level cache disable; indirectly determines the memory type used to access the page directory referenced by
this entry (see Section 4.9.2)
5 (A)
Accessed; indicates whether this entry has been used for linear-address translation (see Section 4.8)
6
Ignored
7 (PS)
Page size; must be 0 (otherwise, this entry maps a 1-GByte page; see Table 4-15)
11:8
Ignored
(M–1):12
Physical address of 4-KByte aligned page directory referenced by this entry
51:M
Reserved (must be 0)
62:52
Ignored
63 (XD)
If IA32_EFER.NXE = 1, execute-disable (if 1, instruction fetches are not allowed from the 1-GByte region controlled
by this entry; see Section 4.6); otherwise, reserved (must be 0)
Table 4-17. Format of an IA-32e Page-Directory Entry that Maps a 2-MByte Page
Bit
Position(s)
Contents
0 (P)
Present; must be 1 to map a 2-MByte page
1 (R/W)
Read/write; if 0, writes may not be allowed to the 2-MByte page referenced by this entry (see Section 4.6)
2 (U/S)
User/supervisor; if 0, user-mode accesses are not allowed to the 2-MByte page referenced by this entry (see Section
3 (PWT)
Page-level write-through; indirectly determines the memory type used to access the 2-MByte page referenced by
this entry (see Section 4.9.2)
4 (PCD)
Page-level cache disable; indirectly determines the memory type used to access the 2-MByte page referenced by
this entry (see Section 4.9.2)
5 (A)
Accessed; indicates whether software has accessed the 2-MByte page referenced by this entry (see Section 4.8)
6 (D)
Dirty; indicates whether software has written to the 2-MByte page referenced by this entry (see Section 4.8)
7 (PS)
Page size; must be 1 (otherwise, this entry references a page table; see Table 4-18)
8 (G)
Global; if CR4.PGE = 1, determines whether the translation is global (see Section 4.10); ignored otherwise