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# ICV_BPR1_EL1, Interrupt Controller Virtual Binary Point Register 1

The ICV_BPR1_EL1 characteristics are:

## Purpose

Defines the point at which the priority value fields split into two parts, the group priority field and the subpriority field. The group priority field determines virtual Group 1 interrupt preemption.

## Configuration

AArch64 System register ICV_BPR1_EL1 bits [31:0] are architecturally mapped to AArch32 System register ICV_BPR1[31:0].

This register is present only when GICv3 is implemented and EL2 is implemented. Otherwise, direct accesses to ICV_BPR1_EL1 are UNDEFINED.

## Attributes

ICV_BPR1_EL1 is a 64-bit register.

## Field descriptions

63 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 40 | 39 | 38 | 37 | 36 | 35 | 34 | 33 | 32
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
RES0 | BinaryPoint

#### Bits [63:3]

Reserved, RES0.

#### BinaryPoint, bits [2:0]

If the GIC is configured to use separate binary point fields for Group 0 and Group 1 interrupts, the value of this field controls how the 8-bit interrupt priority field is split into a group priority field, that determines interrupt preemption, and a subpriority field.

For more information about priorities, see 'Priority grouping' in ARM® Generic Interrupt Controller Architecture Specification, GIC architecture version 3.0 and version 4.0 (ARM IHI 0069).

An attempt to program this field to a value less than the minimum value sets the field to the minimum value.

If ICV_CTLR_EL1.CBPR is set to 1, Non-secure EL1 reads return ICV_BPR0_EL1 + 1 saturated to 0b111. Non-secure EL1 writes are ignored.

If ICV_CTLR_EL1.CBPR is set to 1, Secure EL1 reads return ICV_BPR0_EL1. Secure EL1 writes modify ICV_BPR0_EL1.

The reset behavior of this field is:

- On a Warm reset, this field resets to an architecturally UNKNOWN value.

## Accessing ICV_BPR1_EL1

For Non-secure writes, the minimum value of this field is the minimum value of ICH_VMCR_EL2.VBPR0 plus one.

For Secure writes, the minimum value of this field is the minimum value of ICH_VMCR_EL2.VBPR0.

An attempt to program the binary point field to a value less than the minimum value sets the field to the minimum value. On a reset, the binary point field is UNKNOWN.

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

#### MRS <Xt>, ICC_BPR1_EL1

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b000 | 0b1100 | 0b1100 | 0b011

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.IRQ == '1' then UNDEFINED; elsif ICC_SRE_EL1.SRE == '0' then AArch64.SystemAccessTrap(EL1, 0x18); elsif EL2Enabled() && ICH_HCR_EL2.TALL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && HCR_EL2.IMO == '1' then X[t, 64] = ICV_BPR1_EL1; elsif HaveEL(EL3) && SCR_EL3.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif HaveEL(EL3) then if SCR_EL3.NS == '0' then X[t, 64] = ICC_BPR1_EL1_S; else X[t, 64] = ICC_BPR1_EL1_NS; else X[t, 64] = ICC_BPR1_EL1; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.IRQ == '1' then UNDEFINED; elsif ICC_SRE_EL2.SRE == '0' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && SCR_EL3.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif HaveEL(EL3) then if SCR_EL3.NS == '0' then X[t, 64] = ICC_BPR1_EL1_S; else X[t, 64] = ICC_BPR1_EL1_NS; else X[t, 64] = ICC_BPR1_EL1; elsif PSTATE.EL == EL3 then if ICC_SRE_EL3.SRE == '0' then AArch64.SystemAccessTrap(EL3, 0x18); else if SCR_EL3.NS == '0' then X[t, 64] = ICC_BPR1_EL1_S; else X[t, 64] = ICC_BPR1_EL1_NS;

#### MSR ICC_BPR1_EL1, <Xt>

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b000 | 0b1100 | 0b1100 | 0b011

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.IRQ == '1' then UNDEFINED; elsif ICC_SRE_EL1.SRE == '0' then AArch64.SystemAccessTrap(EL1, 0x18); elsif EL2Enabled() && ICH_HCR_EL2.TALL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && HCR_EL2.IMO == '1' then ICV_BPR1_EL1 = X[t, 64]; elsif HaveEL(EL3) && SCR_EL3.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif HaveEL(EL3) then if SCR_EL3.NS == '0' then ICC_BPR1_EL1_S = X[t, 64]; else ICC_BPR1_EL1_NS = X[t, 64]; else ICC_BPR1_EL1 = X[t, 64]; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.IRQ == '1' then UNDEFINED; elsif ICC_SRE_EL2.SRE == '0' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && SCR_EL3.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif HaveEL(EL3) then if SCR_EL3.NS == '0' then ICC_BPR1_EL1_S = X[t, 64]; else ICC_BPR1_EL1_NS = X[t, 64]; else ICC_BPR1_EL1 = X[t, 64]; elsif PSTATE.EL == EL3 then if ICC_SRE_EL3.SRE == '0' then AArch64.SystemAccessTrap(EL3, 0x18); else if SCR_EL3.NS == '0' then ICC_BPR1_EL1_S = X[t, 64]; else ICC_BPR1_EL1_NS = X[t, 64];

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26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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