Volume 4: Base IA-32 Instruction Reference
4:373
STI—Set Interrupt Flag
Description
Sets the interrupt flag (IF) in the EFLAGS register.
In the IA-32 System
Environment,
after the IF flag is set, the processor begins responding to external
maskable interrupts after the next instruction is executed. If the STI instruction is
followed by a CLI instruction (which clears the IF flag) the effect of the STI instruction is
negated.
In the Itanium System Environment, the processor will immediately
respond do interrupts after STI, unless execution of STI results in a trap or
intercept. External interrupts are enabled for IA-32 instructions if PSR.i and
(~CFLG.if or EFLAG.if).
The IF flag and the STI and CLI instruction have no affect on the generation of
exceptions and NMI interrupts.
The following decision table indicates the action of the STI instruction (bottom of the
table) depending on the processor’s mode of operating and the CPL and IOPL of the
currently running program or procedure (top of the table).
Notes:
XDon't care.
NAction in Column 1 not taken.
YAction in Column 1 taken.
Operation
OLD_IF <- IF;
IF PE=0 (* Executing in real-address mode *)
THEN
IF
1; (* Set Interrupt Flag *)
ELSE (* Executing in protected mode or virtual-8086 mode *)
IF VM=0 (* Executing in protected mode*)
THEN
IF CR4.PVI = 0
THEN
IF CPL <= IOPL
THEN IF <- 1
ELSE #GP(0);
FI;
ELSE (*PVI is 1 *)
Opcode
Instruction
Description
FB
STI
Set interrupt flag; interrupts enabled at the end of the next
instruction
PE =
0
1
1
1
VM =
X
0
0
1
CPL
X
IOPL
> IOPL
=3
IOPL
X
X
X
=3
IF
1
Y
Y
N
Y
#GP(0)
N
N
Y
N
Summary of Contents for ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Page 1: ......
Page 11: ...x Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 13: ...1 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 33: ...1 22 Volume 1 Part 1 Introduction to the Intel Itanium Architecture ...
Page 57: ...1 46 Volume 1 Part 1 Execution Environment ...
Page 147: ...1 136 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 149: ...1 138 Volume 1 Part 2 About the Optimization Guide ...
Page 191: ...1 180 Volume 1 Part 2 Predication Control Flow and Instruction Stream ...
Page 230: ......
Page 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 264: ...2 16 Volume 2 Part 1 Intel Itanium System Environment ...
Page 380: ...2 132 Volume 2 Part 1 Interruptions ...
Page 398: ...2 150 Volume 2 Part 1 Register Stack Engine ...
Page 486: ...2 238 Volume 2 Part 1 IA 32 Interruption Vector Descriptions ...
Page 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 754: ...2 506 Volume 2 Part 2 About the System Programmer s Guide ...
Page 796: ...2 548 Volume 2 Part 2 Interruptions and Serialization ...
Page 808: ...2 560 Volume 2 Part 2 Context Management ...
Page 842: ...2 594 Volume 2 Part 2 Floating point System Software ...
Page 850: ...2 602 Volume 2 Part 2 IA 32 Application Support ...
Page 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Page 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Page 891: ......
Page 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
Page 1295: ...3 396 Volume 3 Resource and Dependency Semantics ...
Page 1296: ......
Page 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1494: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 1647: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 1884: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 1885: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 1886: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1898: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...