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# ICH_LRC<n>, Interrupt Controller List Registers, n = 0 - 15

The ICH_LRC<n> characteristics are:

## Purpose

Provides interrupt context information for the virtual CPU interface.

## Configuration

AArch32 System register ICH_LRC<n> bits [31:0] are architecturally mapped to AArch64 System register ICH_LR<n>_EL2[63:32].

This register is present only when EL2 is capable of using AArch32, GICv3 is implemented and (EL2 is implemented or EL3 is implemented). Otherwise, direct accesses to ICH_LRC<n> are UNDEFINED.

If EL2 is not implemented, this register is RES0 from EL3.

If list register n is not implemented, then accesses to this register are UNDEFINED.

## Attributes

ICH_LRC<n> is a 32-bit register.

## Field descriptions

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
State | HW | Group | RES0 | Priority | RES0 | pINTID

#### State, bits [31:30]

The state of the interrupt:

State | Meaning
--- | ---
0b00 | Invalid (Inactive).
0b01 | Pending.
0b10 | Active.
0b11 | Pending and active.

The GIC updates these state bits as virtual interrupts proceed through the interrupt life cycle. Entries in the invalid state are ignored, except for the purpose of generating virtual maintenance interrupts.

For hardware interrupts, the pending and active state is held in the physical Distributor rather than the virtual CPU interface. A hypervisor must only use the pending and active state for software originated interrupts, which are typically associated with virtual devices, or SGIs.

The reset behavior of this field is:

- On a Warm reset, this field resets to 0.

#### HW, bit [29]

Indicates whether this virtual interrupt maps directly to a hardware interrupt, meaning that it corresponds to a physical interrupt. Deactivation of the virtual interrupt also causes the deactivation of the physical interrupt with the INTID that the pINTID field indicates.

HW | Meaning
--- | ---
0b0 | The interrupt is triggered entirely by software. No notification is sent to the Distributor when the virtual interrupt is deactivated.
0b1 | The interrupt maps directly to a hardware interrupt. A deactivate interrupt request is sent to the Distributor when the virtual interrupt is deactivated, using the pINTID field from this register to indicate the physical INTID. If ICH_VMCR.VEOIM is 0, this request corresponds to a write to ICC_EOIR0 or ICC_EOIR1. Otherwise, it corresponds to a write to ICC_DIR.

The reset behavior of this field is:

- On a Warm reset, this field resets to 0.

#### Group, bit [28]

Indicates the group for this virtual interrupt.

Group | Meaning
--- | ---
0b0 | This is a Group 0 virtual interrupt. ICH_VMCR.VFIQEn determines whether it is signaled as a virtual IRQ or as a virtual FIQ, and ICH_VMCR.VENG0 enables signaling of this interrupt to the virtual machine.
0b1 | This is a Group 1 virtual interrupt, signaled as a virtual IRQ. ICH_VMCR.VENG1 enables the signaling of this interrupt to the virtual machine. If ICH_VMCR.VCBPR is 0, then ICC_BPR1 determines if a pending Group 1 interrupt has sufficient priority to preempt current execution. Otherwise, ICH_LR<n> determines preemption.

The reset behavior of this field is:

- On a Warm reset, this field resets to 0.

#### Bits [27:24]

Reserved, RES0.

#### Priority, bits [23:16]

The priority of this interrupt.

It is IMPLEMENTATION DEFINED how many bits of priority are implemented, though at least five bits must be implemented. Unimplemented bits are RES0 and start from bit[16] up to bit[18]. The number of implemented bits can be discovered from ICH_VTR.PRIbits.

The reset behavior of this field is:

- On a Warm reset, this field resets to 0.

#### Bits [15:13]

Reserved, RES0.

#### pINTID, bits [12:0]

Physical INTID, for hardware interrupts.

When ICH_LRC<n>.HW is 0 (there is no corresponding physical interrupt), this field has the following meaning:

- Bits[12:10] : RES0.
- Bit[9] : EOI. If this bit is 1, then when the interrupt identified by vINTID is deactivated, an EOI maintenance interrupt is asserted.
- Bits[8:0] : Reserved, RES0.

When ICH_LRC<n>.HW is 1 (there is a corresponding physical interrupt):

- This field indicates the physical INTID. This field is only required to implement enough bits to hold a valid value for the implemented INTID size. Any unused higher order bits are RES0.
- When ICC_CTLR_EL1.ExtRange is 0, then bits[44:42] of this field are RES0.
- If the value of pINTID is not a valid INTID, behavior is UNPREDICTABLE. If the value of pINTID indicates a PPI, this field applies to the PPI associated with this same physical PE ID as the virtual CPU interface requesting the deactivation.

A hardware physical identifier is only required in List Registers for interrupts that require deactivation. This means only 13 bits of Physical INTID are required, regardless of the number specified by ICC_CTLR.IDbits.

The reset behavior of this field is:

- On a Warm reset, this field resets to 0.

## Accessing ICH_LRC<n>

ICH_LR<n> and ICH_LRC<n> can be updated independently.

Accesses to this register use the following encodings in the System register encoding space:

#### MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>} ; Where m = 0-15

coproc | opc1 | CRn | CRm | opc2
--- | --- | --- | --- | ---
0b1111 | 0b100 | 0b1100 | 0b111:m[3] | m[2:0]

integer m = UInt(CRm<0>:opc2<2:0>); if m >= NUM_GIC_LIST_REGS then UNDEFINED; elsif PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then AArch32.TakeHypTrapException(0x03); else UNDEFINED; elsif PSTATE.EL == EL2 then if ICC_HSRE.SRE == '0' then UNDEFINED; else R[t] = ICH_LRC[m]; elsif PSTATE.EL == EL3 then if ICC_MSRE.SRE == '0' then UNDEFINED; else R[t] = ICH_LRC[m];

#### MCR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>} ; Where m = 0-15

coproc | opc1 | CRn | CRm | opc2
--- | --- | --- | --- | ---
0b1111 | 0b100 | 0b1100 | 0b111:m[3] | m[2:0]

integer m = UInt(CRm<0>:opc2<2:0>); if m >= NUM_GIC_LIST_REGS then UNDEFINED; elsif PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then AArch32.TakeHypTrapException(0x03); else UNDEFINED; elsif PSTATE.EL == EL2 then if ICC_HSRE.SRE == '0' then UNDEFINED; else ICH_LRC[m] = R[t]; elsif PSTATE.EL == EL3 then if ICC_MSRE.SRE == '0' then UNDEFINED; else ICH_LRC[m] = R[t];

AArch32 Registers | AArch64 Registers | AArch32 Instructions | AArch64 Instructions | Index by Encoding | External Registers | External Registers by Offset | Registers by Functional Group | Proprietary Notice

26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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