Intel 64 and IA-32 Architectures Software Developers Manual Volume 3B, System Programming Guide Part 2

Table Of Contents
Vol. 3 24-7
SUPPORT FOR ADDRESS TRANSLATION
Gbyte region of the guest-physical address space. Table 24-2 shows the format of an
EPT PDPTE.
Note that, if bits 2:0 of an EPT PDPTE are all 0, the entry is considered to be “not
present”; the logical processor ignores bits 63:3 of such an entry and will not use it
to reference an EPT page directory.
24.2.3.3 EPT Page-Directory Entries
An EPT page-directory entry (PDE) is identified using bits 47:21 of the guest-physical
address (see Section 24.2.2) and thus controls access to a 2-Mbyte region of the
guest-physical address space. It may do so either by referencing an EPT page table
or by mapping a single 2-Mbyte page; the value of bit 7 in the EPT PDE determines
which mechanism is used.
If bit 7 of the EPT PDE is 0, the entry references an EPT page table. Table 24-3 shows
the format of such an EPT PDE.
Table 24-2. Format of an EPT Page-Directory-Pointer-Table Entry (PDPTE)
Bit
Position(s)
Contents
0 Read access; indicates whether reads are allowed from the 1-GByte region
controlled by this entry
1 Write access; indicates whether writes are allowed to the 1-GByte region
controlled by this entry
2 Execute access; indicates whether instruction fetches are allowed from the 1-
GByte region controlled by this entry
7:3 Reserved (must be 0)
11:8 Ignored
N–1:12 Physical address of 4-KByte aligned EPT page directory referenced by this entry
1
NOTES:
1. N is the physical-address width supported by the logical processor.
51:N Reserved (must be 0)
63:52 Ignored