vmlaunch

Launch Virtual Machine

VMLAUNCH

Launches a VM managed by the current VMCS.

Details

Launches a virtual machine using the current VMCS. The instruction reads guest state from the current VMCS, validates it, and transitions to VMX non-root mode; on success, control transfers to the guest; on failure, returns to the instruction with CF/ZF set. This is a privileged instruction (CPL=0) available only in VMX root mode on processors with VMX support.

Pseudocode Operation

if (CPL != 0 || VMX_ROOT == 0) raise #UD
if (!validate_vmcs_state()) { RFLAGS.CF ← 1; RFLAGS.ZF ← 0; } else { load_guest_state_from_vmcs(); VMX_ROOT ← 0; transfer_control_to_guest(); }

Example

VMLAUNCH

Encoding

Binary Layout
0F
+0
01
+1
C2
+2
 
Format VMX
Opcode 0F 01 C2
Extension VMX

Operands

Reference (Intel® SDM)

Instruction Forms

Opcode Instruction Op/En 64/32-bit Mode CPUID Description
0F 01 C2 VMLAUNCH ZO Launch virtual machine managed by current VMCS.
0F 01 C3 VMRESUME ZO Resume virtual machine managed by current VMCS.

Description

Effects a VM entry managed by the current VMCS. • VMLAUNCH fails if the launch state of current VMCS is not “clear”. If the instruction is successful, it sets the launch state to “launched.” • VMRESUME fails if the launch state of the current VMCS is not “launched.” If VM entry is attempted, the logical processor performs a series of consistency checks as detailed in Chapter 29, “VM Entries.” Failure to pass checks on the VMX controls or on the host-state area passes control to the instruction following the VMLAUNCH or VMRESUME instruction. If these pass but checks on the guest-state area fail, the logical processor loads state from the host-state area of the VMCS, passing control to the instruction referenced by the RIP field in the host-state area. VM entry is not allowed when events are blocked by MOV SS or POP SS. Neither VMLAUNCH nor VMRESUME should be used immediately after either MOV to SS or POP to SS.

Operation

IF (not in VMX operation) or (CR0.PE = 0) or (RFLAGS.VM = 1) or (IA32_EFER.LMA = 1 and CS.L = 0)
THEN #UD;
ELSIF in VMX non-root operation
THEN VMexit;
ELSIF CPL > 0
THEN #GP(0);
ELSIF current-VMCS pointer is not valid
THEN VMfailInvalid;
ELSIF events are being blocked by MOV SS
THEN VMfailValid(VM entry with events blocked by MOV SS);
ELSIF (VMLAUNCH and launch state of current VMCS is not “clear”)
THEN VMfailValid(VMLAUNCH with non-clear VMCS);
ELSIF (VMRESUME and launch state of current VMCS is not “launched”)
THEN VMfailValid(VMRESUME with non-launched VMCS);
ELSE
Check settings of VMX controls and host-state area;
IF invalid settings
THEN VMfailValid(VM entry with invalid VMX-control field(s)) or
VMfailValid(VM entry with invalid host-state field(s)) or
VMfailValid(VM entry with invalid executive-VMCS pointer)) or
VMfailValid(VM entry with non-launched executive VMCS) or
VMfailValid(VM entry with executive-VMCS pointer not VMXON pointer) or





VMfailValid(VM entry with invalid VM-execution control fields in executive
VMCS)
as appropriate;
ELSE
Attempt to load guest state and PDPTRs as appropriate;
clear address-range monitoring;
IF failure in checking guest state or PDPTRs
THEN VM entry fails (see Section 29.8);
ELSE
Attempt to load MSRs from VM-entry MSR-load area;
IF failure
THEN VM entry fails
(see Section 29.8);
ELSE
IF VMLAUNCH
THEN launch state of VMCS := “launched”;
FI;
IF in SMM and “entry to SMM” VM-entry control is 0
THEN
IF “deactivate dual-monitor treatment” VM-entry
control is 0
THEN SMM-transfer VMCS pointer :=
current-VMCS pointer;
FI;
IF executive-VMCS pointer is VMXON pointer
THEN current-VMCS pointer :=
VMCS-link pointer;
ELSE current-VMCS pointer :=
executive-VMCS pointer;
FI;
leave SMM;
FI;
VM entry succeeds;
FI;
FI;
FI;
FI;
Further details of the operation of the VM-entry appear in Chapter 29.

Flags Affected

See the operation section and Section 33.2.

Exceptions

Protected Mode Exceptions

#GP(0) If the current privilege level is not 0. #UD If executed outside VMX operation.

Real-Address Mode Exceptions

#UD The VMLAUNCH and VMRESUME instructions are not recognized in real-address mode.

Virtual-8086 Mode Exceptions

#UD The VMLAUNCH and VMRESUME instructions are not recognized in virtual-8086 mode. VMLAUNCH/VMRESUME—Launch/Resume Virtual Machine 33-15 Vol. 3C

Compatibility Mode Exceptions

#UD The VMLAUNCH and VMRESUME instructions are not recognized in compatibility mode.

64-Bit Mode Exceptions

#GP(0) If the current privilege level is not 0. #UD If executed outside VMX operation.