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

Table Of Contents
24-10 Vol. 3
SUPPORT FOR ADDRESS TRANSLATION
Note that, if bits 2:0 of an EPT PTE 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 map a 4-KByte page.
24.2.4 EPT-Induced VM Exits
Accesses using guest-physical addresses may cause VM exits due to EPT miscon-
figurations and EPT violations. An EPT misconfiguration occurs when, in the
course of translation a guest-physical address, the logical processor encounters an
EPT paging-structure entry that contains an unsupported value. An EPT violation
occurs when there is no EPT misconfiguration but the EPT paging-structure entries
disallow an access using the guest-physical address.
Note that EPT misconfigurations and EPT violations occur only due to an attempt to
access memory with a guest-physical address. Loading CR3 with a guest-physical
address with the MOV to CR3 instruction can cause neither an EPT configuration nor
an EPT violation until that address is used to access a paging structure.
1
24.2.4.1 EPT Misconfigurations
AN EPT misconfiguration occurs if any of the following is identified while translating a
guest-physical address:
The value of bits 2:0 of an EPT paging-structure entry is either 010b (write-only)
or 110b (write/execute).
The value of bits 2:0 of an EPT paging-structure entry is 100b (execute-only) and
this value is not supported by the logical processor. Software should read the
N–1:12 Physical address of the 4-KByte page referenced by this entry
1
51:N Reserved (must be 0)
63:52 Ignored
NOTES:
1. N is the physical-address width supported by the logical processor.
1. If the logical processor is using PAE paging—because CR4.PAE = 1 and IA32_EFER.LMA = 0—the
MOV to CR3 instruction loads the PDPTEs from memory using the guest-physical address being
loaded into CR3. In this case, therefore, the MOV to CR3 instruction may cause an EPT misconfig-
uration or an EPT violation.
Table 24-5. Format of an EPT Page-Table Entry (Contd.)
Bit
Position(s)
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