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.
Configuration
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:
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:
| HW | Meaning |
|---|---|
| 0b0 |
This interrupt is triggered entirely in software. No notification is sent to the Distributor when the virtual interrupt is deactivated. |
| 0b1 |
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. |
This field resets to an architecturally UNKNOWN value.
Group, bit [30]
Indicates whether the interrupt is Group 0 or Group 1:
| Group | Meaning |
|---|---|
| 0b0 |
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. |
| 0b1 |
Group 1 virtual interrupt, signaled as a virtual IRQ. GICV_CTLR.EnableGrp1 enables signaling of this interrupt to the virtual machine. |
GICV_CTLR.CBPR controls whether GICV_BPR or GICV_ABPR determines if a pending Group 1 interrupt has sufficient priority to preempt current execution.
This field resets to an architecturally UNKNOWN value.
State, bits [29:28]
The state of the interrupt. This field has one of the following values:
| State | Meaning |
|---|---|
| 0b00 |
Inactive |
| 0b01 |
Pending |
| 0b10 |
Active |
| 0b11 |
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.
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.
This field resets to an architecturally UNKNOWN value.
Priority, bits [27:23]
The priority of this interrupt.
This field resets to an architecturally UNKNOWN value.
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:
- Bit [19] indicates whether the interrupt triggers an EOI maintenance interrupt. If this bit is 1, then when the interrupt identified by vINTID is deactivated, an EOI maintenance interrupt is asserted.
- Bits [18:13] are reserved, SBZ.
- If the vINTID field value corresponds to an SGI (that is, 0-15), bits [12:10] contain the number of the requesting PE. This appears in the corresponding field of GICV_IAR or GICV_AIAR. If the vINTID field value is not 0-15, this field must be cleared to 0.
When GICH_LR<n>.HW == 1:
- This field indicates the pINTID that the hypervisor forwards to the Distributor. This field is only required to implement enough bits to hold a valid value for the ID configuration. Any unused higher order bits are RAZ/WI.
- If the value of pINTID is 0-15 or 1020-1023, behavior is UNPREDICTABLE. If the value of pINTID is 16-31, this field applies to the PPI associated with this same PE as the virtual CPU interface requesting the deactivation.
This field resets to an architecturally UNKNOWN value.
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.
This field resets to an architecturally UNKNOWN value.
Accessing the GICH_LR<n>
This register is used only when System register access is not enabled. When System register access is enabled:
- For AArch32 implementations, ICH_LR<n> provides equivalent functionality.
- For AArch64 implementations, ICH_LR<n>_EL2 provides equivalent functionality.
GICH_LR<n> can be accessed through the memory-mapped interfaces:
| Component | Offset | Instance |
|---|---|---|
| GIC Virtual interface control | 0x0100 + (4 * n) | GICH_LR<n> |
This interface is accessible as follows:
- When GICD_CTLR.DS == 0 accesses to this register are RW.
- When an access is Secure accesses to this register are RW.
- When an access is Non-secure accesses to this register are RW.