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

Table Of Contents
24-4 Vol. 3
SUPPORT FOR ADDRESS TRANSLATION
A 4-KByte naturally aligned EPT PML4 table is located at the physical address
specified in bits 51:12 of the extended-page-table pointer (EPTP), a VM-
execution control field (see Table 20-8 in Section 20.6.11). An EPT PML4 entry is
selected from this table using a physical address defined as follows:
Bits 63:52 are all 0.
Bits 51:12 are from the EPTP.
Bits 11:3 are bits 47:39 of the guest-physical address.
Bits 2:0 are all 0.
A 4-KByte naturally aligned EPT page-directory-pointer table is located at the
physical address specified in bits 51:12 of the EPT PML4 entry (see Table 24-1).
An EPT page-directory-pointer-table entry (PDPTE) is selected from this table
using a physical address defined as follows:
Bits 63:52 are all 0.
Bits 51:12 are from the EPT PML4 entry.
Bits 11:3 are bits 38:30 of the guest-physical address.
Bits 2:0 are all 0.
A 4-KByte naturally aligned EPT page directory is located at the physical address
specified in bits 51:12 of the EPT PDPTE (see Table 24-2). An EPT page-directory
entry (PDE) is selected from this table using a physical address defined as
follows:
Bits 63:52 are all 0.
Bits 51:12 are from the EPT PDPTE.
Bits 11:3 are bits 29:21 of the guest-physical address.
Bits 2:0 are all 0.
Use of the EPT PDE depends on the value of bit 7 in that entry:
If bit 7 of the EPT PDE is 0:
A 4-KByte naturally aligned EPT page table is located at the physical address
specified in bits 51:12 of the EPT PDE (see Table 24-3). An EPT page-table
entry (PTE) is selected from this table using a physical address defined as
follows:
2. No processors supporting the Intel 64 architecture support more than 48 physical-address bits.
Thus, no such processor can produce a guest-physical address with more than 48 bits. An
attempt to use such an address will cause a page fault. An attempt to load CR3 with such an
address causes a general-protection fault. If PAE paging is being used, an attempt to load CR3
that would load a PDPTE with such an address causes a general-protection fault.
3. Future processors may include support for other EPT page-walk lengths. Software should read
the VMX capability MSR IA32_VMX_EPT_VPID_CAP (see Appendix G.10) to determine what EPT
page-walk lengths are supported.