ICH_AP0R<n>

AArch32 System register ICH_AP0R<n> bits [31:0] are architecturally mapped to AArch64 System register ICH_AP0R<n>_EL2[31:0].

This register is present only when EL2 is capable of using AArch32, GICv3 is implemented and (EL2 is implemented or EL3 is implemented). Otherwise, direct accesses to ICH_AP0R<n> are UNDEFINED.

Attributes

Field descriptions

P<x>, bit [x], for x = 31 to 0

Provides the access to the virtual active priorities for Group 0 interrupts. Possible values of each bit are:

P<x>	Meaning
0b0	There is no Group 0 interrupt active at the priority corresponding to that bit.
0b1	There is a Group 0 interrupt active at the priority corresponding to that bit.

The correspondence between priority levels and bits depends on the number of bits of priority that are implemented.

If 5 bits of preemption are implemented (bits [7:3] of priority), then there are 32 preemption levels, and the active state of these preemption levels are held in ICH_AP0R0 in the bits corresponding to Priority[7:3].

If 6 bits of preemption are implemented (bits [7:2] of priority), then there are 64 preemption levels, and:

The active state of preemption levels 0 - 124 are held in ICH_AP0R0 in the bits corresponding to 0:Priority[6:2].
The active state of preemption levels 128 - 252 are held in ICH_AP0R1 in the bits corresponding to 1:Priority[6:2].

If 7 bits of preemption are implemented (bits [7:1] of priority), then there are 128 preemption levels, and:

The active state of preemption levels 0 - 62 are held in ICH_AP0R0 in the bits corresponding to 00:Priority[5:1].
The active state of preemption levels 64 - 126 are held in ICH_AP0R1 in the bits corresponding to 01:Priority[5:1].
The active state of preemption levels 128 - 190 are held in ICH_AP0R2 in the bits corresponding to 10:Priority[5:1].
The active state of preemption levels 192 - 254 are held in ICH_AP0R3 in the bits corresponding to 11:Priority[5:1].

Note

Having the bit corresponding to a priority set to 1 in both ICH_AP0R<n> and ICH_AP1R<n> might result in UNPREDICTABLE behavior of the interrupt prioritization system for virtual interrupts.

The reset behavior of this field is:

On a Warm reset, this field resets to 0.

Accessing ICH_AP0R<n>

ICH_AP0R1 is implemented only in implementations that support 6 or more bits of preemption. ICH_AP0R2 and ICH_AP0R3 are implemented only in implementations that support 7 bits of preemption. Unimplemented registers are UNDEFINED.

Note

The number of bits of preemption is indicated by ICH_VTR.PREbits

Writing to the active priority registers in any order other than the following order will result in UNPREDICTABLE behavior:

ICH_AP0R<n>
ICH_AP1R<n>

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

MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>} ; Where m = 0-3

coproc	opc1	CRn	CRm	opc2
0b1111	0b100	0b1100	0b1000	0b0:m[1:0]

integer m = UInt(opc2<1:0>); if m == 1 && NUM_GIC_PREEMPTION_BITS < 6 then UNDEFINED; elsif (m == 2 || m == 3) && NUM_GIC_PREEMPTION_BITS < 7 then UNDEFINED; elsif PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then AArch32.TakeHypTrapException(0x03); else UNDEFINED; elsif PSTATE.EL == EL2 then if ICC_HSRE.SRE == '0' then UNDEFINED; else R[t] = ICH_AP0R[m]; elsif PSTATE.EL == EL3 then if ICC_MSRE.SRE == '0' then UNDEFINED; else R[t] = ICH_AP0R[m];

MCR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>} ; Where m = 0-3

coproc	opc1	CRn	CRm	opc2
0b1111	0b100	0b1100	0b1000	0b0:m[1:0]

integer m = UInt(opc2<1:0>); if m == 1 && NUM_GIC_PREEMPTION_BITS < 6 then UNDEFINED; elsif (m == 2 || m == 3) && NUM_GIC_PREEMPTION_BITS < 7 then UNDEFINED; elsif PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then AArch32.TakeHypTrapException(0x03); else UNDEFINED; elsif PSTATE.EL == EL2 then if ICC_HSRE.SRE == '0' then UNDEFINED; else ICH_AP0R[m] = R[t]; elsif PSTATE.EL == EL3 then if ICC_MSRE.SRE == '0' then UNDEFINED; else ICH_AP0R[m] = R[t];

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
P31	P30	P29	P28	P27	P26	P25	P24	P23	P22	P21	P20	P19	P18	P17	P16	P15	P14	P13	P12	P11	P10	P9	P8	P7	P6	P5	P4	P3	P2	P1	P0

ICH_AP0R<n>, Interrupt Controller Hyp Active Priorities Group 0 Registers, n = 0 - 3

Purpose

Configuration