WFE
Wait For Event
Wait For Event is a hint instruction that indicates that the PE can
enter a low-power state and remain there until a wakeup event
occurs. Wakeup events include the event signaled as a result of
executing the SEV instruction on any PE in the multiprocessor
system.
For more information, see Wait For Event and
Send Event.
As described in Wait For Event and Send Event,
the execution of a WFE instruction that
would otherwise cause entry to a low-power state can be trapped
to a higher Exception level, see HCR.TWE,
SCR.TWE, and SCTLR.nTWE.
For more information about the CONSTRAINED UNPREDICTABLE behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors.
It has encodings from the following instruction sets:
A32 (
A1
)
and
T32 (
T1
and
T2
)
.
!= 1111
0
0
1
1
0
0
1
0
0
0
0
0
(1)
(1)
(1)
(1)
(0)
(0)
(0)
(0)
0
0
0
0
0
0
1
0
WFE{<c>}{<q>}
// No additional decoding required
1
0
1
1
1
1
1
1
0
0
1
0
0
0
0
0
WFE{<c>}{<q>}
// No additional decoding required
1
1
1
1
0
0
1
1
1
0
1
0
(1)
(1)
(1)
(1)
1
0
(0)
0
(0)
0
0
0
0
0
0
0
0
0
1
0
WFE{<c>}.W
// No additional decoding required
<c>
See Standard assembler syntax fields.
<q>
See Standard assembler syntax fields.
if ConditionPassed() then
EncodingSpecificOperations();
if IsEventRegisterSet() then
ClearEventRegister();
else
if HaveEL(EL3) && EL3SDDUndefPriority() then
// Check for traps described by the Secure Monitor.
// If the trap is enabled, the instruction will be UNDEFINED because EDSCR.SDD is 1.
AArch32_CheckForWFxTrap(EL3, WFxType_WFE);
end;
if PSTATE.EL == EL0 then
// Check for traps described by the OS.
AArch32_CheckForWFxTrap(EL1, WFxType_WFE);
end;
if PSTATE.EL IN {EL0, EL1} && EL2Enabled() && !IsInHost() then
// Check for traps described by the Hypervisor.
AArch32_CheckForWFxTrap(EL2, WFxType_WFE);
end;
if HaveEL(EL3) && PSTATE.M != M32_Monitor then
// Check for traps described by the Secure Monitor.
AArch32_CheckForWFxTrap(EL3, WFxType_WFE);
end;
WaitForEvent();
end;
end;
2026-03-12 12:23:09
2025-09_rel_asl1