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ICH_ELRSR_EL2, Interrupt Controller Empty List Register Status Register

The ICH_ELRSR_EL2 characteristics are:

Purpose

These registers can be used to locate a usable List register when the hypervisor is delivering an interrupt to a VM.

Configuration

AArch64 System register ICH_ELRSR_EL2 bits [31:0] are architecturally mapped to AArch32 System register ICH_ELRSR[31:0] .

If EL2 is not implemented, this register is RES0 from EL3.

This register has no effect if EL2 is not enabled in the current Security state.

Attributes

ICH_ELRSR_EL2 is a 64-bit register.

Field descriptions

The ICH_ELRSR_EL2 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
00000000000000000000000000000000
0000000000000000Status<n>, bit [n], for n = 0 to 15
313029282726252423222120191817161514131211109876543210

Bits [63:16]

Reserved, RES0.

Status<n>, bit [n], for n = 0 to 15

Status bit for List register <n>, ICH_LR<n>_EL2:

Status<n>Meaning
0b0

List register ICH_LR<n>_EL2, if implemented, contains a valid interrupt. Using this List register can result in overwriting a valid interrupt.

0b1

List register ICH_LR<n>_EL2 does not contain a valid interrupt. The List register is empty and can be used without overwriting a valid interrupt or losing an EOI maintenance interrupt.

For any List register <n>, the corresponding status bit is set to 1 if ICH_LR<n>_EL2.State is 0b00 and either ICH_LR<n>_EL2.HW is 1 or ICH_LR<n>_EL2.EOI (bit [41]) is 0.

Otherwise the status bit takes the value 0.

Accessing the ICH_ELRSR_EL2

Accesses to this register use the following encodings:

MRS <Xt>, ICH_ELRSR_EL2

op0CRnop1op2CRm
0b110b11000b1000b1010b1011
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    if ICC_SRE_EL2.SRE == '0' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        return ICH_ELRSR_EL2;
elsif PSTATE.EL == EL3 then
    if ICC_SRE_EL3.SRE == '0' then
        AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return ICH_ELRSR_EL2;
              


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