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# GICV_AIAR, Virtual Machine Aliased Interrupt Acknowledge Register

The GICV_AIAR characteristics are:

## Purpose

Provides the INTID of the signaled Group 1 virtual interrupt. A read of this register by the PE acts as an acknowledge for the interrupt.

This register corresponds to the physical CPU interface register GICC_AIAR.

## Configuration

This register is present only when FEAT_GICv3_LEGACY is implemented and EL2 is implemented. Otherwise, direct accesses to GICV_AIAR are RES0.

This register is available when the GIC implementation supports interrupt virtualization.

## Attributes

GICV_AIAR 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
RES0 | INTID

#### Bits [31:25]

Reserved, RES0.

#### INTID, bits [24:0]

The INTID of the signaled interrupt.

Note

INTIDs 1020-1023 are reserved and convey additional information such as spurious interrupts.

When affinity routing is not enabled:

- Bits [23:13] are RES0.
- For SGIs, bits [12:10] identify the CPU interface corresponding to the source PE. For all other interrupts these bits are RES0.

#### Additional information

The operation of this register is similar to the operation of GICV_IAR. When a vPE reads this register, the corresponding GICH_LR<n>.Group field is checked to determine whether the interrupt is in Group 0 or Group 1:

- If the interrupt is Group 0, the spurious INTID 1023 is returned and the interrupt is not acknowledged.
- If the interrupt is Group 1, the INTID is returned. The List register entry is updated to active state, and the appropriate bit in GICH_APR<n> is set to 1.

A read of this register returns the spurious INTID 1023 if any of the following are true:

- When the virtual CPU interface is enabled and GICH_HCR.En == 1:
  - There are no pending interrupts of sufficiently high priority value to be signaled to the PE.
  - The highest priority pending interrupt is in Group 0.
- Interrupt signaling by the virtual CPU interface is disabled.

## Accessing GICV_AIAR

This register is used only when System register access is not enabled. When System register access is enabled:

- For AArch32 implementations, ICC_IAR1 provides equivalent functionality.
- For AArch64 implementations, ICC_IAR1_EL1 provides equivalent functionality.

This register is used for Group 1 interrupts only. GICV_IAR provides equivalent functionality for Group 0 interrupts.

When affinity routing is enabled, it is a programming error to use memory-mapped registers to access the GIC.

#### GICV_AIAR can be accessed through the memory-mapped interfaces:

Component | Offset | Instance
--- | --- | ---
GIC Virtual CPU interface | 0x0020 | GICV_AIAR

This interface is accessible as follows:

- When GICD_CTLR.DS == 0, accesses to this register are RO.
- When an access is Secure, accesses to this register are RO.
- When an access is Non-secure, accesses to this register are RO.

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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