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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] .

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.

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

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.

Field descriptions

The PAR bit assignments are:

When the instruction returned a 32-bit value to the PAR, PAR.F==0:
6362616059585756555453525150494847464544434241403938373635343332
00000000000000000000000000000000
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].

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.

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.

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.

This field resets to an architecturally UNKNOWN value.

IMPLEMENTATION DEFINED, bit [8]

IMPLEMENTATION DEFINED.

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.

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.

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.

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.

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.

This field resets to an architecturally UNKNOWN value.

When the instruction returned a 32-bit value to the PAR, PAR.F==1:
6362616059585756555453525150494847464544434241403938373635343332
00000000000000000000000000000000
IMPLEMENTATION DEFINED0000LPAE0000FSF

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.

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.

This field resets to an architecturally UNKNOWN value.

Bits [10:7]

Reserved, RES0.

FS, bits [6:1]

Fault status bits. Bits [12,10,3:0] from the DFSR, indicating the source of the abort.

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.

This field resets to an architecturally UNKNOWN value.

When the instruction returned a 64-bit value to the PAR, PAR.F==0:
6362616059585756555453525150494847464544434241403938373635343332
ATTR0000000000000000PA
PALPAEIMPLEMENTATION DEFINEDNSSH000000F

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.

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].

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.

This field resets to an architecturally UNKNOWN value.

IMPLEMENTATION DEFINED, bit [10]

IMPLEMENTATION DEFINED.

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.

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.

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.

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 DEFINED0000000000000000
00000000000000000000LPAE0FSTAGES2WLK0FSTF
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.

This field resets to an architecturally UNKNOWN value.

IMPLEMENTATION DEFINED, bits [55:52]

IMPLEMENTATION DEFINED.

This field resets to an architecturally UNKNOWN value.

IMPLEMENTATION DEFINED, bits [51:48]

IMPLEMENTATION DEFINED.

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.

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.

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.

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.

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.

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>}

opc1opc2CRncoprocCRm
0b0000b0000b01110b11110b0100
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
        if SCR.NS == '0' then
            return PAR_S<31:0>;
        else
            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>}

opc1opc2CRncoprocCRm
0b0000b0000b01110b11110b0100
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
        if SCR.NS == '0' then
            PAR_S = ZeroExtend(R[t]);
        else
            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>

opc1coprocCRm
0b00000b11110b0111
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
        if SCR.NS == '0' then
            return PAR_S;
        else
            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>

opc1coprocCRm
0b00000b11110b0111
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
        if SCR.NS == '0' then
            PAR_S = R[t2]:R[t];
        else
            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];
              


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