STUI - Set User Interrupt Flag

Opcode/ Instruction

Op/ En

64/32 bit Mode Support

CPUID Feature Flag

Description

F3 0F 01 EF STUI

ZO

V/I

UINTR

Set user interrupt flag.

Instruction Operand Encoding

Op/En

Tuple

Operand 1

Operand 2

Operand 3

Operand 4

ZO

N/A

N/A

N/A

N/A

N/A

Description

STUI sets the user interrupt flag (UIF). Its effect takes place immediately; a user interrupt may be delivered on the instruction boundary following STUI. (This is in contrast with STI, whose effect is delayed by one instruction).

An execution of STUI inside a transactional region causes a transactional abort; the abort loads EAX as it would have had it been due to an execution of STI.

Operation 

UIF := 1;

Flags Affected

None.

Protected Mode Exceptions

#UD

The STUI instruction is not recognized in protected mode.

Real-Address Mode Exceptions

#UD

The STUI instruction is not recognized in real-address mode.

Virtual-8086 Mode Exceptions

#UD

The STUI instruction is not recognized in virtual-8086 mode.

Compatibility Mode Exceptions

#UD

The STUI instruction is not recognized in compatibility mode.

64-Bit Mode Exceptions

#UD

If the LOCK prefix is used. If executed inside an enclave. If CR4.UINTR = 0. If CPUID.07H.0H:EDX.UINTR[bit 5] = 0.