The ICC_IAR0 characteristics are:
The PE reads this register to obtain the INTID of the signaled Group 0 interrupt. This read acts as an acknowledge for the interrupt.
AArch32 System register ICC_IAR0 performs the same function as AArch64 System register ICC_IAR0_EL1.
This register is present only when AArch32 is supported at EL0 and FEAT_GICv3 is implemented. Otherwise, direct accesses to ICC_IAR0 are UNDEFINED.
To allow software to ensure appropriate observability of actions initiated by GIC register accesses, the PE and CPU interface logic must ensure that reads of this register are self-synchronising when interrupts are masked by the PE (that is when PSTATE.{I,F} == {0,0}). This ensures that the effect of activating an interrupt on the signaling of interrupt exceptions is observed when a read of this register is architecturally executed so that no spurious interrupt exception occurs if interrupts are unmasked by an instruction immediately following the read. For more information, see 'Observability of the effects of accesses to the GIC registers' in ARM® Generic Interrupt Controller Architecture Specification, GIC architecture version 3.0 and version 4.0 (ARM IHI 0069).
ICC_IAR0 is a 32-bit register.
31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
RES0 | INTID |
Reserved, RES0.
The INTID of the signaled interrupt.
This is the INTID of the highest priority pending interrupt, if that interrupt is of sufficient priority for it to be signaled to the PE, and if it can be acknowledged at the current Security state and Exception level.
If the highest priority pending interrupt is not observable, this field contains a special INTID to indicate the reason. These special INTIDs can be one of: 1020, 1021, or 1023. For more information, see 'Special INTIDs' in ARM® Generic Interrupt Controller Architecture Specification, GIC architecture version 3.0 and version 4.0 (ARM IHI 0069).
This field has either 16 or 24 bits implemented. The number of implemented bits can be found in ICC_CTLR.IDbits and ICC_MCTLR.IDbits. If only 16 bits are implemented, bits [23:16] of this register are RES0.
Accesses to this register use the following encodings in the System register encoding space:
coproc | opc1 | CRn | CRm | opc2 |
---|---|---|---|---|
0b1111 | 0b000 | 0b1100 | 0b1000 | 0b000 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && !ELUsingAArch32(EL3) && SCR_EL3.FIQ == '1' then UNDEFINED; elsif Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && ELUsingAArch32(EL3) && PSTATE.M != M32_Monitor && SCR.FIQ == '1' then UNDEFINED; elsif EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then AArch32.TakeHypTrapException(0x03); elsif ICC_SRE.SRE == '0' then UNDEFINED; elsif EL2Enabled() && !ELUsingAArch32(EL2) && ICH_HCR_EL2.TALL0 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && ICH_HCR.TALL0 == '1' then AArch32.TakeHypTrapException(0x03); elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.FMO == '1' then return ICV_IAR0; elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.FMO == '1' then return ICV_IAR0; elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && SCR_EL3.FIQ == '1' then if Halted() && EDSCR.SDD == '1' then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) && PSTATE.M != M32_Monitor && SCR.FIQ == '1' then if Halted() && EDSCR.SDD == '1' then UNDEFINED; else AArch32.TakeMonitorTrapException(); else return ICC_IAR0; elsif PSTATE.EL == EL2 then if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && !ELUsingAArch32(EL3) && SCR_EL3.FIQ == '1' then UNDEFINED; elsif Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && ELUsingAArch32(EL3) && SCR.FIQ == '1' then UNDEFINED; elsif ICC_HSRE.SRE == '0' then UNDEFINED; elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && SCR_EL3.FIQ == '1' then if Halted() && EDSCR.SDD == '1' then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) && SCR.FIQ == '1' then if Halted() && EDSCR.SDD == '1' then UNDEFINED; else AArch32.TakeMonitorTrapException(); else return ICC_IAR0; elsif PSTATE.EL == EL3 then if ICC_MSRE.SRE == '0' then UNDEFINED; else return ICC_IAR0;
30/06/2021 15:21; 2a17f7750cfd1ab239f20f6cf29877ba8041794f
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