GICH_LR<n>, List Registers, n = 0 - 15

The GICH_LR<n> characteristics are:

Purpose

These registers provide context information for the virtual CPU interface.

This register is part of the GIC virtualised guest interface control registers functional group.

Usage constraints

This register is accessible as follows:

Security disabledSecureNon-secure
RWRWRW

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

Configuration

RW fields in this register reset to architecturally UNKNOWN values.

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

A maximum of 16 List registers can be provided. GICH_VTR.ListRegs defines the number implemented. Unimplemented List registers are RAZ/WI.

Attributes

GICH_LR<n> is a 32-bit register.

Field descriptions

The GICH_LR<n> bit assignments are:

313029282726252423222120191817161514131211109876543210
HWGroupStatePriority000pINTIDvINTID

HW, bit [31]

Indicates whether this virtual interrupt is a hardware interrupt, meaning that it corresponds to a physical interrupt. Deactivation of the virtual interrupt also causes the deactivation of the physical interrupt corresponding to the INTID:

HWMeaning
0

This interrupt is triggered entirely in software. No notification is sent to the Distributor when the virtual interrupt is deactivated.

1

A hardware interrupt. A deactivate interrupt request is sent to the Distributor when the virtual interrupt is deactivated, using GICH_LR<n>.pINTID to indicate the physical interrupt identifier.

If GICV_CTLR.EOImode == 0, this request corresponds to a write to GICV_EOIR or GICV_AEOIR, otherwise it corresponds to a write to GICV_DIR.

When this register has an architecturally-defined reset value, this field resets to a value that is architecturally UNKNOWN.

Group, bit [30]

Indicates whether the interrupt is Group 0 or Group 1:

GroupMeaning
0

Group 0 virtual interrupt. GICV_CTLR.FIQEn determines whether it is signaled as a virtual IRQ or as a virtual FIQ, and GICV_CTLR.EnableGrp0 enables signaling of this interrupt to the virtual machine.

1

Group 1 virtual interrupt, signaled as a virtual IRQ. GICV_CTLR.EnableGrp1 enables signaling of this interrupt to the virtual machine.

Note

GICV_CTLR.CBPR controls whether GICV_BPR or GICV_ABPR determines if a pending Group 1 interrupt has sufficient priority to preempt current execution.

When this register has an architecturally-defined reset value, this field resets to a value that is architecturally UNKNOWN.

State, bits [29:28]

The state of the interrupt. This field has one of the following values:

StateMeaning
00

Inactive

01

Pending

10

Active

11

Active and pending

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

Note

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

When this register has an architecturally-defined reset value, this field resets to a value that is architecturally UNKNOWN.

Priority, bits [27:23]

The priority of this interrupt.

When this register has an architecturally-defined reset value, this field resets to a value that is architecturally UNKNOWN.

Bits [22:20]

Reserved, RES0.

pINTID, bits [19:10]

The function of this field depends on the value of GICH_LR<n>.HW.

When GICH_LR<n>.HW == 0:

When GICH_LR<n>.HW == 1:

When this register has an architecturally-defined reset value, this field resets to a value that is architecturally UNKNOWN.

vINTID, bits [9:0]

This INTID is returned to the VM when the interrupt is acknowledged through GICV_IAR. Each valid interrupt stored in the List registers must have a unique vINTID for that virtual CPU interface. If the value of vINTID is 1020-1023, behavior is UNPREDICTABLE.

When this register has an architecturally-defined reset value, this field resets to a value that is architecturally UNKNOWN.

Accessing the GICH_LR<n>

GICH_LR<n> can be accessed through its memory-mapped interface:

ComponentOffset
GIC Virtual interface control0x0100 + 4n



28/09/2017 08:24

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