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WFI

Wait For Interrupt is a hint instruction that indicates that the PE can enter a low-power state and remain there until a wakeup event occurs. For more information, see Wait For Interrupt.

As described in Wait For Interrupt, the execution of a WFI instruction that would otherwise cause entry to a low-power state can be trapped to a higher Exception level. See:

313029282726252423222120191817161514131211109876543210
11010101000000110010000001111111
CRmop2

System

WFI

// Empty.

Operation

if !InterruptPending() then
    if PSTATE.EL == EL0 then
        // Check for traps described by the OS which may be EL1 or EL2.
        AArch64.CheckForWFxTrap(EL1, FALSE);
    if PSTATE.EL IN {EL0, EL1} && EL2Enabled() && !IsInHost() then
        // Check for traps described by the Hypervisor.
        AArch64.CheckForWFxTrap(EL2, FALSE);
    if HaveEL(EL3) && PSTATE.EL != EL3 then
        // Check for traps described by the Secure Monitor.
        AArch64.CheckForWFxTrap(EL3, FALSE);
    WaitForInterrupt();
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