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DISR, Deferred Interrupt Status Register

The DISR characteristics are:

Purpose

Records that an SError interrupt has been consumed by an ESB instruction.

Configuration

AArch32 System register DISR bits [31:0] are architecturally mapped to AArch64 System register DISR_EL1[31:0] when the highest implemented Exception level is using AArch64.

This register is present only when RAS is implemented. Otherwise, direct accesses to DISR are UNDEFINED.

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

DISR is a 32-bit register.

Field descriptions

The DISR bit assignments are:

When the ESB instruction is executed at EL2:
313029282726252423222120191817161514131211109876543210
A0000000000000000000AETEA000DFSC

A, bit [31]

Set to 1 when an ESB instruction defers an asynchronous SError interrupt. If the implementation does not include any sources of SError interrupt that can be synchronized by an Error Synchronization Barrier, then this bit is RES0.

This field resets to an architecturally UNKNOWN value.

Bits [30:12]

Reserved, RES0.

AET, bits [11:10]

Asynchronous Error Type. See the description of HSR.AET for an SError interrupt.

This field resets to an architecturally UNKNOWN value.

EA, bit [9]

External abort Type. See the description of HSR.EA for an SError interrupt.

This field resets to an architecturally UNKNOWN value.

Bits [8:6]

Reserved, RES0.

DFSC, bits [5:0]

Fault Status Code. See the description of HSR.DFSC for an SError interrupt.

This field resets to an architecturally UNKNOWN value.

When the ESB instruction is executed at EL0 or EL1 and where TTBCR.EAE == 0:
313029282726252423222120191817161514131211109876543210
A000000000000000AET0ExT0FS[4]LPAE00000FS[3:0]

A, bit [31]

Set to 1 when an ESB instruction defers an asynchronous SError interrupt. If the implementation does not include any sources of SError interrupt that can be synchronized by an Error Synchronization Barrier, then this bit is RES0.

This field resets to an architecturally UNKNOWN value.

Bits [30:16]

Reserved, RES0.

AET, bits [15:14]

Asynchronous Error Type. See the description of DFSR.AET for an SError interrupt.

This field resets to an architecturally UNKNOWN value.

Bit [13]

Reserved, RES0.

ExT, bit [12]

External abort Type. See the description of DFSR.ExT for an SError interrupt.

This field resets to an architecturally UNKNOWN value.

Bit [11]

Reserved, RES0.

FS[4], bit [10]

This field is bit[4] of FS[4:0].

Fault Status Code. See the description of DFSR.FS for an SError interrupt.

The FS field is split as follows:

  • FS[4] is DISR[10].
  • FS[3:0] is DISR[3:0].

This field resets to an architecturally UNKNOWN value.

LPAE, bit [9]

Format.

LPAEMeaning
0b0

Using the Short-descriptor translation table format.

This field resets to an architecturally UNKNOWN value.

Bits [8:4]

Reserved, RES0.

FS[3:0], bits [3:0]

This field is bits[3:0] of FS[4:0].

See FS[4] for the field description.

When the ESB instruction is executed at EL0 or EL1 and where TTBCR.EAE == 1:
313029282726252423222120191817161514131211109876543210
A000000000000000AET0ExT00LPAE000STATUS

A, bit [31]

Set to 1 when an ESB instruction defers an asynchronous SError interrupt. If the implementation does not include any sources of SError interrupt that can be synchronized by an Error Synchronization Barrier, then this bit is RES0.

This field resets to an architecturally UNKNOWN value.

Bits [30:16]

Reserved, RES0.

AET, bits [15:14]

Asynchronous Error Type. See the description of DFSR.AET for an SError interrupt.

This field resets to an architecturally UNKNOWN value.

Bit [13]

Reserved, RES0.

ExT, bit [12]

External abort Type. See the description of DFSR.ExT for an SError interrupt.

This field resets to an architecturally UNKNOWN value.

Bits [11:10]

Reserved, RES0.

LPAE, bit [9]

Format.

LPAEMeaning
0b1

Using the Long-descriptor translation table format.

This field resets to an architecturally UNKNOWN value.

Bits [8:6]

Reserved, RES0.

STATUS, bits [5:0]

Fault Status Code. See the description of DFSR.DFSC for an SError interrupt.

This field resets to an architecturally UNKNOWN value.

Accessing the DISR

An indirect write to DISR made by an ESB instruction does not require an explicit synchronization operation for the value that is written to be observed by a direct read of DISR occurring in program order after the ESB instruction.

DISR is RAZ/WI if EL3 is implemented, the PE is in Non-debug state, and any of the following apply:

  • EL3 is using AArch64, SCR_EL3.EA == 1, and any of the following apply:
    • The PE is executing at EL2.
    • The PE is executing at EL1 and ((SCR_EL3.NS == 0 && SCR_EL3.EEL2 == 0) || HCR_EL2.AMO == 0).
  • EL3 is using AArch32, SCR.EA == 1, and any of the following apply:
    • The PE is executing at EL2.
    • The PE is executing at EL1 and (SCR.NS == 0 || HCR.AMO == 0).

Accesses to this register use the following encodings:

MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

opc1opc2CRncoprocCRm
0b0000b0010b11000b11110b0001
if 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);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.AMO == '1' then
        return VDISR_EL2;
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.AMO == '1' then
        return VDISR;
    else
        return DISR;
elsif PSTATE.EL == EL2 then
    return DISR;
elsif PSTATE.EL == EL3 then
    return DISR;
              

MCR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

opc1opc2CRncoprocCRm
0b0000b0010b11000b11110b0001
if 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);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.AMO == '1' then
        VDISR_EL2 = R[t];
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.AMO == '1' then
        VDISR = R[t];
    else
        DISR = R[t];
elsif PSTATE.EL == EL2 then
    DISR = R[t];
elsif PSTATE.EL == EL3 then
    DISR = R[t];
              


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