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

Table Of Contents
24-6 Vol. 3
SUPPORT FOR ADDRESS TRANSLATION
24.2.3.1 EPT PML4 Entries
An EPT PML4 entry is identified using bits 47:39 of the guest-physical address (see
Section 24.2.2) and thus controls access to a 512-Gbyte region of the guest-physical
address space. Table 24-1 shows the format of an EPT PML4 entry.
Note that, if bits 2:0 of an EPT PML4 entry 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-pointer table.
24.2.3.2 EPT Page-Directory-Pointer-Table Entries
An EPT page-directory-pointer-table entry (PDPTE) is identified using bits 47:30 of
the guest-physical address (see Section 24.2.2) and thus controls access to a 1-
Table 24-1. Format of an EPT PML4 Entry
Bit
Position(s)
Contents
0 Read access; indicates whether reads are allowed from the 512-GByte region
controlled by this entry
1 Write access; indicates whether writes are allowed to the 512-GByte region
controlled by this entry
2 Execute access; indicates whether instruction fetches are allowed from the 512-
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-pointer table referenced
by this entry
1
NOTES:
1. N is the physical-address width supported by the processor. Software can determine a processor’s
physical-address width by executing CPUID with 80000008H in EAX. The physical-address width
is returned in bits 7:0 of EAX.
51:N Reserved (must be 0)
63:52 Ignored