GICV_AIAR

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GICV_AIAR, Virtual Machine Aliased Interrupt Acknowledge Register

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.

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

Field descriptions

Bits [31:25]

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:

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:

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