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.

This UNOFFICIAL, mechanically-separated, non-verified reference is provided for convenience, but it may be incomplete or broken in various obvious or non-obvious ways. Refer to Intel® 64 and IA-32 Architectures Software Developer’s Manual for anything serious.