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PAR, Physical Address Register

The PAR characteristics are:

Purpose

Returns the output address (OA) from an Address translation instruction that executed successfully, or fault information if the instruction did not execute successfully.

Configuration

AArch32 System register PAR bits [63:0] are architecturally mapped to AArch64 System register PAR_EL1[63:0] .

This register is present only when AArch32 is supported at any Exception level. Otherwise, direct accesses to PAR are UNDEFINED.

PAR is a 64-bit register that can also be accessed as a 32-bit value. If it is accessed as a 32-bit register, accesses read and write bits[31:0] and do not modify bits[63:32].

The Configurations section specifies the cases where each PAR format is used.

PAR is accessed as a 32-bit value:

  • When the PE is not in Hyp mode and is using the Short-descriptor translation table format.
  • When the PE is in Hyp mode and executes an ATS12NSOPR, ATS12NSOPW, ATS12NSOUR, or ATS12NSOUW instruction and the value of HCR.VM is 0 and the value of TTBCR.EAE is 0.

In these cases, PAR[63:32] is RES0.

Otherwise, the PAR is accessed as a 64-bit value, if any of the following is true:

  • When using the Long-descriptor translation table format.
  • If the stage 1 address translation is disabled and TTBCR.EAE is set to 1.
  • In an implementation that includes EL2, for the result of an ATS1Cxx instruction performed from Hyp mode.

For PL1&0 stage 1 translations, TTBCR.EAE selects the translation table format.

Attributes

PAR is a 64-bit register.

Field descriptions

The PAR bit assignments are:

When the instruction returned a 32-bit value to the PAR, PAR.F==0:
6362616059585756555453525150494847464544434241403938373635343332
RES0
PALPAENOSNSIMPLEMENTATION DEFINEDSHInner[2:0]Outer[1:0]SSF

This section describes the register value returned by the successful execution of an Address translation instruction. Software might subsequently write a different value to the register, and that write does not affect the operation of the PE.

On a successful conversion, the PAR can return a value that indicates the resulting attributes, rather than the values that appear in the translation table descriptors. More precisely:

  • Memory attribute fields are permitted to report the resulting attributes, as determined by any permitted implementation choices and any applicable configuration bits, instead of reporting the values that appear in the translation table descriptors. This applies to the NOS, SH, Inner, and Outer fields.
  • See the NS bit description for constraints on the value it returns.

Bits [63:32]

Reserved, RES0.

PA, bits [31:12]

Output address. The output address (OA) corresponding to the supplied input address. This field returns address bits[31:12].

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

LPAE, bit [11]

When updating the PAR with the result of the translation operation, this bit is set as follows:

LPAEMeaning
0b0

Short-descriptor translation table format used. This means the PAR returned a 32-bit value.

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

NOS, bit [10]

Not Outer Shareable. When the returned value of PAR.SH is 1, indicates the Shareability attribute for the physical memory region:

NOSMeaning
0b0

Memory region is Outer Shareable.

0b1

Memory region is Inner Shareable.

When the returned value of PAR.SH is 0 the value returned to this field is UNKNOWN.

The value returned in this field can be the resulting attribute, as determined by any permitted implementation choices and any applicable configuration bits, instead of the value that appears in the translation table descriptor.

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

NS, bit [9]

Non-secure. The NS attribute for a translation table entry from a Secure translation regime.

For a result from a Secure translation regime, this bit reflects the Security state of the physical address space of the translation. This means it reflects the effect of the NSTable bits of earlier levels of the translation table walk if those NSTable bits have an effect on the translation.

For a result from a Non-secure translation regime, this bit is UNKNOWN.

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

IMPLEMENTATION DEFINED, bit [8]

IMPLEMENTATION DEFINED.

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

SH, bit [7]

Shareability. Indicates whether the physical memory region is Non-shareable:

SHMeaning
0b0

Memory is Non-shareable.

0b1

Memory is shareable, and PAR.NOS indicates whether the region is Outer Shareable or Inner Shareable.

The value returned in this field can be the resulting attribute, as determined by any permitted implementation choices and any applicable configuration bits, instead of the value that appears in the translation table descriptor.

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

Inner[2:0], bits [6:4]

Inner cacheability attribute for the region. Permitted values are:

Inner[2:0]Meaning
0b000

Non-cacheable.

0b001

Device-nGnRnE.

0b011

Device-nGnRE.

0b101

Write-Back, Write-Allocate.

0b110

Write-Through.

0b111

Write-Back, no Write-Allocate.

The values 0b010 and 0b100 are reserved.

The value returned in this field can be the resulting attribute, as determined by any permitted implementation choices and any applicable configuration bits, instead of the value that appears in the translation table descriptor.

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

Outer[1:0], bits [3:2]

Outer cacheability attribute for the region. Permitted values are:

Outer[1:0]Meaning
0b00

Non-cacheable.

0b01

Write-Back, Write-Allocate.

0b10

Write-Through, no Write-Allocate.

0b11

Write-Back, no Write-Allocate.

The value returned in this field can be the resulting attribute, as determined by any permitted implementation choices and any applicable configuration bits, instead of the value that appears in the translation table descriptor.

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

SS, bit [1]

Supersection. Used to indicate if the result is a Supersection:

SSMeaning
0b0

Result is not a Supersection. PAR[31:12] contains OA[31:12].

0b1

Result is a Supersection, and:

  • PAR[31:24] contains OA[31:24].
  • PAR[23:16] contains OA[39:32].
  • PAR[15:12] contains 0b0000.

If an implementation supports less than 40 bits of physical address, the bits in the PAR field that correspond to physical address bits that are not implemented are UNKNOWN.

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

F, bit [0]

Indicates whether the instruction performed a successful address translation.

FMeaning
0b0

Address translation completed successfully.

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

When the instruction returned a 32-bit value to the PAR, PAR.F==1:
6362616059585756555453525150494847464544434241403938373635343332
RES0
IMPLEMENTATION DEFINEDRES0LPAERES0FS[5]FS[4:0]F

This section describes the register value returned by a fault on the execution of an Address translation instruction. Software might subsequently write a different value to the register, and that write does not affect the operation of the PE.

Bits [63:32]

Reserved, RES0.

IMPLEMENTATION DEFINED, bits [31:16]

IMPLEMENTATION DEFINED.

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

Bits [15:12]

Reserved, RES0.

LPAE, bit [11]

When updating the PAR with the result of the translation operation, this bit is set as follows:

LPAEMeaning
0b0

Short-descriptor translation table format used. This means the PAR returned a 32-bit value.

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

Bits [10:7]

Reserved, RES0.

FS[5], bit [6]

Fault status bits, external abort type. Provides an IMPLEMENTATION DEFINED classification of an External abort. Values are as in in the DFSR.ExT field when using the Short-descriptor translation table format.

In an implementation that does not provide any classification of External aborts, this bit is RES0.

For aborts other than External aborts this bit always returns 0.

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

FS[4:0], bits [5:1]

Fault status bits. Values are as in the DFSR.FS field when using the Short-descriptor translation table format.

FS[4:0]MeaningApplies when
0b00001

Alignment fault.

0b00011

Access flag fault, level 1.

0b00100

Fault on instruction cache maintenance.

0b00101

Translation fault, level 1.

0b00110

Access flag fault, level 2.

0b00111

Translation fault, level 2.

0b01001

Domain fault, level 1.

0b01011

Domain fault, level 2.

0b01100

Synchronous External abort, on translation table walk, level 1.

0b01101

Permission fault, level 1.

0b01110

Synchronous External abort, on translation table walk, level 2.

0b01111

Permission fault, level 2.

0b10000

TLB conflict abort.

0b11001

Synchronous parity or ECC error on memory access, not on translation table walk.

When FEAT_RAS is not implemented
0b11100

Synchronous parity or ECC error on translation table walk, level 1.

When FEAT_RAS is not implemented
0b11110

Synchronous parity or ECC error on translation table walk, level 2.

When FEAT_RAS is not implemented

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

F, bit [0]

Indicates whether the instruction performed a successful address translation.

FMeaning
0b1

Address translation aborted.

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

When the instruction returned a 64-bit value to the PAR, PAR.F==0:
6362616059585756555453525150494847464544434241403938373635343332
ATTRRES0PA
PALPAEIMPLEMENTATION DEFINEDNSSHRES0F

This section describes the register value returned by the successful execution of an Address translation instruction. Software might subsequently write a different value to the register, and that write does not affect the operation of the PE.

On a successful conversion, the PAR can return a value that indicates the resulting attributes, rather than the values that appear in the translation table descriptors. More precisely:

  • Memory attribute fields are permitted to report the resulting attributes, as determined by any permitted implementation choices and any applicable configuration bits, instead of reporting the values that appear in the translation table descriptors. This applies to the ATTR and SH fields.
  • See the NS bit description for constraints on the value it returns.

ATTR, bits [63:56]

Memory attributes for the returned output address. This field uses the same encoding as the Attr<n> fields in MAIR0 and MAIR1.

The value returned in this field can be the resulting attribute, as determined by any permitted implementation choices and any applicable configuration bits, instead of the value that appears in the translation table descriptor.

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

Bits [55:40]

Reserved, RES0.

PA, bits [39:12]

Output address. The output address (OA) corresponding to the supplied input address. This field returns address bits[39:12].

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

LPAE, bit [11]

When updating the PAR with the result of the translation operation, this bit is set as follows:

LPAEMeaning
0b1

Long-descriptor translation table format used. This means the PAR returned a 64-bit value.

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

IMPLEMENTATION DEFINED, bit [10]

IMPLEMENTATION DEFINED.

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

NS, bit [9]

Non-secure. The NS attribute for a translation table entry from a Secure translation regime.

For a result from a Secure translation regime, this bit reflects the Security state of the physical address space of the translation. This means it reflects the effect of the NSTable bits of earlier levels of the translation table walk if those NSTable bits have an effect on the translation.

For a result from a Non-secure translation regime, this bit is UNKNOWN.

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

SH, bits [8:7]

Shareability attribute, for the returned output address. Permitted values are:

SHMeaning
0b00

Non-shareable.

0b10

Outer Shareable.

0b11

Inner Shareable.

The value 0b01 is reserved.

Note

This field returns the value 0b10 for:

  • Any type of Device memory.
  • Normal memory with both Inner Non-cacheable and Outer Non-cacheable attributes.

The value returned in this field can be the resulting attribute, as determined by any permitted implementation choices and any applicable configuration bits, instead of the value that appears in the translation table descriptor.

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

Bits [6:1]

Reserved, RES0.

F, bit [0]

Indicates whether the instruction performed a successful address translation.

FMeaning
0b0

Address translation completed successfully.

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

When the instruction returned a 64-bit value to the PAR, PAR.F==1:
6362616059585756555453525150494847464544434241403938373635343332
IMPLEMENTATION DEFINEDIMPLEMENTATION DEFINEDIMPLEMENTATION DEFINEDRES0
RES0LPAERES0FSTAGES2WLKRES0FSTF
313029282726252423222120191817161514131211109876543210
313029282726252423222120191817161514131211109876543210
313029282726252423222120191817161514131211109876543210
313029282726252423222120191817161514131211109876543210

This section describes the register value returned by a fault on the execution of an Address translation instruction. Software might subsequently write a different value to the register, and that write does not affect the operation of the PE.

IMPLEMENTATION DEFINED, bits [63:56]

IMPLEMENTATION DEFINED.

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

IMPLEMENTATION DEFINED, bits [55:52]

IMPLEMENTATION DEFINED.

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

IMPLEMENTATION DEFINED, bits [51:48]

IMPLEMENTATION DEFINED.

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

Bits [47:12]

Reserved, RES0.

LPAE, bit [11]

When updating the PAR with the result of the translation operation, this bit is set as follows:

LPAEMeaning
0b1

Long-descriptor translation table format used. This means the PAR returned a 64-bit value.

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

Bit [10]

Reserved, RES0.

FSTAGE, bit [9]

Indicates the translation stage at which the translation aborted:

FSTAGEMeaning
0b0

Translation aborted because of a fault in the stage 1 translation.

0b1

Translation aborted because of a fault in the stage 2 translation.

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

S2WLK, bit [8]

If this bit is set to 1, it indicates the translation aborted because of a stage 2 fault during a stage 1 translation table walk.

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

Bit [7]

Reserved, RES0.

FST, bits [6:1]

Fault status field. Values are as in the DFSR.STATUS and IFSR.STATUS fields when using the Long-descriptor translation table format.

FSTMeaningApplies when
0b000000

Address size fault in translation table base register.

0b000001

Address size fault, level 1.

0b000010

Address size fault, level 2.

0b000011

Address size fault, level 3.

0b000101

Translation fault, level 1.

0b000110

Translation fault, level 2.

0b000111

Translation fault, level 3.

0b001001

Access flag fault, level 1.

0b001010

Access flag fault, level 2.

0b001011

Access flag fault, level 3.

0b001101

Permission fault, level 1.

0b001110

Permission fault, level 2.

0b001111

Permission fault, level 3.

0b010101

Synchronous External abort on translation table walk, level 1.

0b010110

Synchronous External abort on translation table walk, level 2.

0b010111

Synchronous External abort on translation table walk, level 3.

0b011101

Synchronous parity or ECC error on memory access on translation table walk, level 1.

When FEAT_RAS is not implemented
0b011110

Synchronous parity or ECC error on memory access on translation table walk, level 2.

When FEAT_RAS is not implemented
0b011111

Synchronous parity or ECC error on memory access on translation table walk, level 3.

When FEAT_RAS is not implemented
0b110000

TLB conflict abort.

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

F, bit [0]

Indicates whether the instruction performed a successful address translation.

FMeaning
0b1

Address translation aborted.

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

Accessing the PAR

Accesses to this register use the following encodings:

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

coprocopc1CRnCRmopc2
0b11110b0000b01110b01000b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T7 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T7 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif HaveEL(EL3) && ELUsingAArch32(EL3) then
        return PAR_NS<31:0>;
    else
        return PAR<31:0>;
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && ELUsingAArch32(EL3) then
        return PAR_NS<31:0>;
    else
        return PAR<31:0>;
elsif PSTATE.EL == EL3 then
    if SCR.NS == '0' then
        return PAR_S<31:0>;
    else
        return PAR_NS<31:0>;
              

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

coprocopc1CRnCRmopc2
0b11110b0000b01110b01000b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T7 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T7 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif HaveEL(EL3) && ELUsingAArch32(EL3) then
        PAR_NS = ZeroExtend(R[t]);
    else
        PAR = ZeroExtend(R[t]);
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && ELUsingAArch32(EL3) then
        PAR_NS = ZeroExtend(R[t]);
    else
        PAR = ZeroExtend(R[t]);
elsif PSTATE.EL == EL3 then
    if SCR.NS == '0' then
        PAR_S = ZeroExtend(R[t]);
    else
        PAR_NS = ZeroExtend(R[t]);
              

MRRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <Rt2>, <CRm>

coprocCRmopc1
0b11110b01110b0000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T7 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x04);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T7 == '1' then
        AArch32.TakeHypTrapException(0x04);
    elsif HaveEL(EL3) && ELUsingAArch32(EL3) then
        return PAR_NS;
    else
        return PAR;
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && ELUsingAArch32(EL3) then
        return PAR_NS;
    else
        return PAR;
elsif PSTATE.EL == EL3 then
    if SCR.NS == '0' then
        return PAR_S;
    else
        return PAR_NS;
              

MCRR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <Rt2>, <CRm>

coprocCRmopc1
0b11110b01110b0000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T7 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x04);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T7 == '1' then
        AArch32.TakeHypTrapException(0x04);
    elsif HaveEL(EL3) && ELUsingAArch32(EL3) then
        PAR_NS = R[t2]:R[t];
    else
        PAR = R[t2]:R[t];
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && ELUsingAArch32(EL3) then
        PAR_NS = R[t2]:R[t];
    else
        PAR = R[t2]:R[t];
elsif PSTATE.EL == EL3 then
    if SCR.NS == '0' then
        PAR_S = R[t2]:R[t];
    else
        PAR_NS = R[t2]:R[t];