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

Table Of Contents
24-16 Vol. 3
SUPPORT FOR ADDRESS TRANSLATION
Dual-tagged translations. Each of these is a mapping from a linear page
number to the physical page frame to which it translates, along with
information about access privileges and memory typing.
Dual-tagged paging-structure-cache entries. Each of these is a mapping from
the upper portion of a linear address to the physical address of the paging
structure used to translate the corresponding region of the linear-address
space, along with information about access privileges.
The information in dual-tagged mappings about access privileges and memory
typing is derived from both guest paging structures and EPT paging structures.
24.3.2 Creating and Using Cached Translation Information
The following items detail the creation of the mappings described in the previous
section:
The following items describe the creation of mappings while EPT is not in use
(including execution outside VMX non-root operation):
VPID-tagged mappings may be created. They are derived from the paging
structures referenced (directly or indirectly) by the current value of CR3 and
are associated with the current VPID.
No VPID-tagged mappings are created with information derived from paging-
structure entries that are not present (bit 0 is 0) or that set reserved bits. For
example, if a PTE is not present, no VPID-tagged mapping will be created for
any linear page number whose translation would use that PTE.
No EPTP-tagged or dual-tagged mappings are created while EPT is not in use.
The following items describe the creation of mappings while EPT is in use:
EPTP-tagged mappings may be created. They are derived from the EPT
paging structures referenced (directly or indirectly) by the current EPTP and
are associated with that EPTP.
Dual-tagged mappings may be created. They are derived from the paging
structures referenced (directly or indirectly) by the current value of CR3 and
from the EPT paging structures referenced (directly or indirectly) by the
current EPTP. They are associated with the current VPID and the current
EPTP.
1
No EPTP-tagged mappings or dual-tagged mappings are created with
information derived from EPT paging-structure entries that are not present
(bits 2:0 are all 0) or that are misconfigured (see Section 24.2.4.1).
1. At any given time, a logical processor may cache dual-tagged mappings for a VPID that are asso-
ciated with different EPTPs. Similarly, it may cache dual-tagged mappings for an EPTP that are
associated with different VPIDs.