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

Table Of Contents
20-14 Vol. 3
VIRTUAL-MACHINE CONTROL STRUCTURES
Table 20-7 lists the secondary processor-based VM-execution controls. See Chapter
21 for more details of how these controls affect processor behavior in VMX non-root
operation.
All other bits in these fields are reserved to 0. Software should consult the VMX capa-
bility MSR IA32_VMX_PROCBASED_CTLS2 (see Appendix G.3.3) to determine how to
set reserved bits. Failure to clear reserved bits causes subsequent VM entries to fail
(see Section 22.2).
If a logical processor supports the 1-setting of bit 31 of the primary processor-based
VM-execution controls but software has set that bit is 0, VM entry and VMX non-root
operation function as if all the secondary processor-based VM-execution controls
were 0. However, the logical processor will maintain the secondary processor-based
VM-execution controls as written by VMWRITE.
20.6.3 Exception Bitmap
The exception bitmap is a 32-bit field that contains one bit for each exception.
When an exception occurs, its vector is used to select a bit in this field. If the bit is 1,
the exception causes a VM exit. If the bit is 0, the exception is delivered normally
through the IDT, using the descriptor corresponding to the exception’s vector.
Whether a page fault (exception with vector 14) causes a VM exit is determined by
bit 14 in the exception bitmap as well as the error code produced by the page fault
Table 20-7. Definitions of Secondary Processor-Based VM-Execution Controls
Bit Position(s) Name Description
0 Virtualize APIC
accesses
If this control is 1, a VM exit occurs on any attempt to access
data on the page with the APIC-access address. See Section
21.2.
1 Enable EPT If this control is 1, extended page tables (EPT) are enabled.
See Chapter 24.
2 Descriptor-table
exiting
This control determines whether executions of LGDT, LIDT,
LLDT, LTR, SGDT, SIDT, SLDT, and STR cause VM exits.
3 Enable RDTSCP If this control is 0, any execution of RDTSCP causes and
invalid-opcode exception (#UD).
4 Virtualize x2APIC
mode
Setting this control to 1 causes RDMSR and WRMSR to MSR
808H to use the TPR shadow, which is maintained on the
virtual-APIC page. See Section 21.4.
5 Enable VPID If this control is 1, cached translations of linear addresses are
associated with a virtual-processor identifier (VPID). See
Chapter 24.1.
6 WBINVD exiting This control determines whether executions of WBINVD
cause VM exits.