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

21-2 Vol. 3
VMX NON-ROOT OPERATION
• Certain exceptions have priority over VM exits. These include invalid-opcode
exceptions, faults based on privilege level, and general-protection exceptions
that are based on checking I/O permission bits in the task-state segment (TSS).
For example, execution of RDMSR with CPL = 3 generates a general-protection
exception and not a VM exit.
1
• Faults incurred while fetching instruction operands have priority over VM exits
that are conditioned based on the contents of those operands (see LMSW in
Section 21.1.3).
• VM exits caused by execution of the INS and OUTS instructions (resulting either
because the “unconditional I/O exiting” VM-execution control is 1 or because the
“use I/O bitmaps control is 1) have priority over the following faults:
— A general-protection fault due to the relevant segment (ES for INS; DS for
OUTS unless overridden by an instruction prefix) being unusable
— A general-protection fault due to an offset beyond the limit of the relevant
segment
— An alignment-check exception
• Fault-like VM exits have priority over exceptions other than those mentioned
above. For example, RDMSR of a non-existent MSR with CPL = 0 generates a
VM exit and not a general-protection exception.
When Section 21.1.2 or Section 21.1.3 (below) identify an instruction execution that
may lead to a VM exit, it is assumed that the instruction does not incur a fault that
takes priority over a VM exit.
21.1.2 Instructions That Cause VM Exits Unconditionally
The following instructions cause VM exits when they are executed in VMX non-root
operation: CPUID, GETSEC,
2
INVD, and XSETBV.
3
This is also true of instructions
introduced with VMX, which include: INVEPT, INVVPID, VMCALL,
4
VMCLEAR,
VMLAUNCH, VMPTRLD, VMPTRST, VMREAD, VMRESUME, VMWRITE, VMXOFF, and
VMXON.
1. MOV DR is an exception to this rule; see Section 21.1.3.
2. An execution of GETSEC in VMX non-root operation causes a VM exit if CR4.SMXE[Bit 14] = 1
regardless of the value of CPL or RAX. An execution of GETSEC causes an invalid-opcode excep-
tion (#UD) if CR4.SMXE[Bit 14] = 0.
3. An execution of XSETBV in VMX non-root operation causes a VM exit if CR4.OSXSAVE[Bit 18] =
1 regardless of the value of CPL, RAX, RCX, or RDX. An execution of XSETBV causes an invalid-
opcode exception (#UD) if CR4.OSXSAVE[Bit 18] = 0.
4. Under the dual-monitor treatment of SMIs and SMM, executions of VMCALL cause SMM VM exits
in VMX root operation outside SMM. See Section 25.15.2.