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TCR_EL2: Translation Control Register (EL2)

Purpose

The control register for stage 1 of the EL2, or EL2&0, translation regime:

Configuration

AArch64 System register TCR_EL2 bits [31:0] are architecturally mapped to AArch32 System register HTCR[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

TCR_EL2 is a 64-bit register.

Field descriptions

When the Effective value of HCR_EL2.E2H is not 1:

6362616059585756555453525150494847464544434241403938373635343332
313029282726252423222120191817161514131211109876543210
RES0MTXDS
RES1TCMATBIDHWU62HWU61HWU60HWU59HPDRES1HDHATBIRES0PSTG0SH0ORGN0IRGN0RES0T0SZ

Any of the bits in TCR_EL2 are permitted to be cached in a TLB.

Bits [63:34]

Reserved, RES0.

MTX, bit [33]

When FEAT_MTE_NO_ADDRESS_TAGS is implemented or FEAT_MTE_CANONICAL_TAGS is implemented:

Extended memory tag checking.

This field controls address generation and tag checking when EL2 is using AArch64 where the data address would be translated by tables pointed to by TTBR0_EL2.

This control has an effect regardless of whether stage 1 of the EL2 translation regime is enabled or not.

MTXMeaning
0b0

This control has no effect on the PE.

0b1

Bits[59:56] of a 64-bit VA hold a Logical Address Tag, and all of the following apply:

  • Bits[59:56] are treated as 0b0000 when checking if the address is out of range.
  • If FEAT_PAuth is implemented, bits[59:56] are not part of the PAC field.
  • A Canonical Tag Check operation is performed on Tag Checked memory accesses to a Canonically Tagged memory location.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

DS, bit [32]

When FEAT_LPA2 is implemented:

This field affects whether a 52-bit output address can be described by the translation tables of the 4KB or 16KB translation granules.

DSMeaning
0b0

Bits[49:48] of translation descriptors are RES0.

Bits[9:8] in Block and Page descriptors encode shareability information in the SH[1:0] field. Bits[9:8] in table descriptors are ignored by hardware.

The minimum value of TCR_EL2.T0SZ is 16. Any memory access using a smaller value generates a stage 1 level 0 translation table fault.

Output address[51:48] is 0b0000.

0b1

Bits[49:48] of translation descriptors hold output address[49:48].

Bits[9:8] of Translation table descriptors hold output address[51:50].

The shareability information of Block and Page descriptors for cacheable locations is determined by TCR_EL2.SH0.

The minimum value of TCR_EL2.T0SZ is 12. Any memory access using a smaller value generates a stage 1 level 0 translation table fault.

All calculations of the stage 1 base address are modified for tables of fewer than 8 entries so that the table is aligned to 64 bytes.

Bits[5:2] of TTBR0_EL2 are used to hold bits[51:48] of the output address in all cases.

Note

As FEAT_LVA must be implemented if TCR_EL2.DS == 1, the minimum value of the TCR_EL2.T0SZ field is 12, as determined by that extension.

For the TLBI Range instructions affecting VA, the format of the argument is changed so that bits[36:0] hold BaseADDR[52:16]. For the 4KB translation granule, bits[15:12] of BaseADDR are treated as 0b0000. For the 16KB translation granule, bits[15:14] of BaseADDR are treated as 0b00.

Note

This forces alignment of the ranges used by the TLBI range instructions.

This field is RES0 for a 64KB translation granule.

The reset behavior of this field is:



Otherwise:

Reserved, RES0, and the Effective value of this bit is 0b0.

Bit [31]

Reserved, RES1.

TCMA, bit [30]

When FEAT_MTE2 is implemented:

Controls the generation of Unchecked accesses at EL2 when address [59:56] = 0b0000.

TCMAMeaning
0b0

This control has no effect on the generation of Unchecked accesses.

0b1

All accesses are Unchecked.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

TBID, bit [29]

When FEAT_PAuth is implemented:

Controls the use of the top byte of instruction addresses for address matching.

For the purpose of this field, all cache maintenance and address translation instructions that perform address translation are treated as data accesses.

For more information, see 'Address tagging'.

TBIDMeaning
0b0

TCR_EL2.TBI applies to Instruction and Data accesses.

0b1

TCR_EL2.TBI applies to Data accesses only.

This affects addresses where the address would be translated by tables pointed to by TTBR0_EL2.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU62, bit [28]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[62] of the stage 1 translation table Block or Page entry.

HWU62Meaning
0b0

Bit[62] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

Bit[62] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU61, bit [27]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[61] of the stage 1 translation table Block or Page entry.

HWU61Meaning
0b0

Bit[61] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

Bit[61] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU60, bit [26]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[60] of the stage 1 translation table Block or Page entry.

HWU60Meaning
0b0

Bit[60] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

Bit[60] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU59, bit [25]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[59] of the stage 1 translation table Block or Page entry.

HWU59Meaning
0b0

Bit[59] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

Bit[59] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HPD, bit [24]

When FEAT_HPDS is implemented:

Hierarchical Permission Disables. This affects the hierarchical control bits, APTable, PXNTable, and UXNTable, except NSTable, in the translation tables pointed to by TTBR0_EL2.

HPDMeaning
0b0

Hierarchical permissions are enabled.

0b1

Hierarchical permissions are disabled.

Note

In this case, bit[61] (APTable[0]) and bit[59] (PXNTable) of the next level descriptor attributes are required to be ignored by the PE and are no longer reserved, allowing them to be used by software.

When disabled, the permissions are treated as if the bits are zero.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

Bit [23]

Reserved, RES1.

HD, bit [22]

When FEAT_HAFDBS is implemented:

Hardware management of dirty state in stage 1 translations from EL2.

HDMeaning
0b0

Stage 1 hardware management of dirty state disabled.

0b1

Stage 1 hardware management of dirty state enabled, only if the HA bit is also set to 1.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HA, bit [21]

When FEAT_HAFDBS is implemented:

Hardware Access flag update in stage 1 translations from EL2.

HAMeaning
0b0

Stage 1 Access flag update disabled.

0b1

Stage 1 Access flag update enabled.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

TBI, bit [20]

Top Byte Ignored. Indicates whether the top byte of an address is used for address match for the TTBR0_EL2 region, or ignored and used for tagged addresses.

For more information, see 'Address tagging'.

TBIMeaning
0b0

Top Byte used in the address calculation.

0b1

Top Byte ignored in the address calculation.

This affects addresses generated in EL2 using AArch64 where the address would be translated by tables pointed to by TTBR0_EL2. It has an effect whether the EL2, or EL2&0, translation regime is enabled or not.

If FEAT_PAuth is implemented and TCR_EL2.TBID is 1, then this field only applies to Data accesses.

If the value of TBI is 1, then bits[63:56] of that target address are also set to 0 before the address is stored in the PC, in the following cases:

The reset behavior of this field is:

Bit [19]

Reserved, RES0.

PS, bits [18:16]

Physical Address Size.

PSMeaningApplies when
0b000

32 bits, 4GB.

0b001

36 bits, 64GB.

0b010

40 bits, 1TB.

0b011

42 bits, 4TB.

0b100

44 bits, 16TB.

0b101

48 bits, 256TB.

0b110

52 bits, 4PB.

0b111

56 bits, 64PB.

When FEAT_D128 is implemented

If the translation granule is not 64KB and FEAT_LPA2 is not implemented, the value 0b110 is treated as reserved.

It is IMPLEMENTATION DEFINED whether an implementation that does not implement FEAT_LPA supports setting the value of 0b110 for the 64KB translation granule size or whether setting this value behaves as the 0b101 encoding.

If the value of ID_AA64MMFR0_EL1.PARange is 0b0110, and the value of this field is not 0b110 or a value treated as 0b110, then bits[51:48] of every translation table base address for the stage of translation controlled by TCR_EL2 are 0b0000.

The reset behavior of this field is:

TG0, bits [15:14]

Granule size for the TTBR0_EL2.

TG0Meaning
0b00

4KB.

0b01

64KB.

0b10

16KB.

Other values are reserved.

If the value is programmed to either a reserved value or a size that has not been implemented, then the hardware will treat the field as if it has been programmed to an IMPLEMENTATION DEFINED choice of the sizes that has been implemented for all purposes other than the value read back from this register.

It is IMPLEMENTATION DEFINED whether the value read back is the value programmed or the value that corresponds to the size chosen.

The reset behavior of this field is:

SH0, bits [13:12]

Shareability attribute for memory associated with translation table walks using TTBR0_EL2.

SH0Meaning
0b00

Non-shareable.

0b10

Outer Shareable.

0b11

Inner Shareable.

Other values are reserved. The effect of programming this field to a Reserved value is that behavior is CONSTRAINED UNPREDICTABLE.

The reset behavior of this field is:

ORGN0, bits [11:10]

Outer cacheability attribute for memory associated with translation table walks using TTBR0_EL2.

ORGN0Meaning
0b00

Normal memory, Outer Non-cacheable.

0b01

Normal memory, Outer Write-Back Read-Allocate Write-Allocate Cacheable.

0b10

Normal memory, Outer Write-Through Read-Allocate No Write-Allocate Cacheable.

0b11

Normal memory, Outer Write-Back Read-Allocate No Write-Allocate Cacheable.

The reset behavior of this field is:

IRGN0, bits [9:8]

Inner cacheability attribute for memory associated with translation table walks using TTBR0_EL2.

IRGN0Meaning
0b00

Normal memory, Inner Non-cacheable.

0b01

Normal memory, Inner Write-Back Read-Allocate Write-Allocate Cacheable.

0b10

Normal memory, Inner Write-Through Read-Allocate No Write-Allocate Cacheable.

0b11

Normal memory, Inner Write-Back Read-Allocate No Write-Allocate Cacheable.

The reset behavior of this field is:

Bits [7:6]

Reserved, RES0.

T0SZ, bits [5:0]

The size offset of the memory region addressed by TTBR0_EL2. The region size is 2(64-T0SZ) bytes.

The maximum and minimum possible values for T0SZ depend on the level of translation table and the memory translation granule size, as described in the AArch64 Virtual Memory System Architecture chapter.

Note

For the 4KB translation granule, if FEAT_LPA2 is implemented and this field is less than 16, the translation table walk begins with a level -1 initial lookup.

For the 16KB translation granule, if FEAT_LPA2 is implemented and this field is less than 17, the translation table walk begins with a level 0 initial lookup.

The reset behavior of this field is:

When the Effective value of HCR_EL2.E2H is 1:

6362616059585756555453525150494847464544434241403938373635343332
313029282726252423222120191817161514131211109876543210
RES0MTX1MTX0DSTCMA1TCMA0E0PD1E0PD0NFD1NFD0TBID1TBID0HWU162HWU161HWU160HWU159HWU062HWU061HWU060HWU059HPD1HPD0HDHATBI1TBI0ASRES0IPS
TG1SH1ORGN1IRGN1EPD1A1T1SZTG0SH0ORGN0IRGN0EPD0RES0T0SZ

Any of the bits in TCR_EL2, other than the A1 bit and the EPDx bits when they have the value 1, are permitted to be cached in a TLB.

Bits [63:62]

Reserved, RES0.

MTX1, bit [61]

When FEAT_MTE_NO_ADDRESS_TAGS is implemented or FEAT_MTE_CANONICAL_TAGS is implemented:

Extended memory tag checking.

This field controls address generation and tag checking when EL0 and EL2 are using AArch64 where the data address would be translated by tables pointed to by TTBR1_EL2.

This control has an effect regardless of whether stage 1 of the EL2&0 translation regime is enabled or not.

MTX1Meaning
0b0

This control has no effect on the PE.

0b1

Bits[59:56] of a 64-bit VA hold a Logical Address Tag, and all of the following apply:

  • Bits[59:56] are treated as 0b1111 when checking if the address is out of range.
  • If FEAT_PAuth is implemented, bits[59:56] are not part of the PAC field.
  • A Canonical Tag Check operation is performed on Tag Checked memory accesses to a Canonically Tagged memory location.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

MTX0, bit [60]

When FEAT_MTE_NO_ADDRESS_TAGS is implemented or FEAT_MTE_CANONICAL_TAGS is implemented:

Extended memory tag checking.

This field controls address generation and tag checking when EL0 and EL2 are using AArch64 where the data address would be translated by tables pointed to by TTBR0_EL2.

This control has an effect regardless of whether stage 1 of the EL2&0 translation regime is enabled or not.

MTX0Meaning
0b0

This control has no effect on the PE.

0b1

Bits[59:56] of a 64-bit VA hold a Logical Address Tag, and all of the following apply:

  • Bits[59:56] are treated as 0b0000 when checking if the address is out of range.
  • If FEAT_PAuth is implemented, bits[59:56] are not part of the PAC field.
  • A Canonical Tag Check operation is performed on Tag Checked memory accesses to a Canonically Tagged memory location.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

DS, bit [59]

When FEAT_LPA2 is implemented and (FEAT_D128 is not implemented or TCR2_EL2.D128 == 0):

This field affects whether a 52-bit output address can be described by the translation tables of the 4KB or 16KB translation granules.

DSMeaning
0b0

Bits[49:48] of translation descriptors are RES0.

Bits[9:8] in Block and Page descriptors encode shareability information in the SH[1:0] field. Bits[9:8] in table descriptors are ignored by hardware.

The minimum value of the TCR_EL2.{T0SZ, T1SZ} fields is 16. Any memory access using a smaller value generates a stage 1 level 0 translation table fault.

Output address[51:48] is 0b0000.

0b1

Bits[49:48] of translation descriptors hold output address[49:48].

Bits[9:8] of Translation table descriptors hold output address[51:50].

The shareability information of Block and Page descriptors for cacheable locations is determined by:

  • TCR_EL2.SH0 if the VA is an address that is translated using tables pointed to by TTBR0_EL2.

  • TCR_EL2.SH1 if the VA is an address that is translated using tables pointed to by TTBR1_EL2.

The minimum value of the TCR_EL2.{T0SZ, T1SZ} fields is 12. Any memory access using a smaller value generates a stage 1 level 0 translation table fault.

All calculations of the stage 1 base address are modified for tables of fewer than 16 entries so that the table is aligned to 64 bytes.

Bits[5:2] of TTBR0_EL2 or TTBR1_EL2 are used to hold bits[51:48] of the output address in all cases.

Note

As FEAT_LVA must be implemented if TCR_EL2.DS == 1, the minimum value of the TCR_EL2.{T0SZ, T1SZ} fields is 12, as determined by that extension.

For the TLBI Range instructions affecting VA, the format of the argument is changed so that bits[36:0] hold BaseADDR[52:16]. For the 4KB translation granule, bits[15:12] of BaseADDR are treated as 0b0000. For the 16KB translation granule, bits[15:14] of BaseADDR are treated as 0b00.

Note

This forces alignment of the ranges used by the TLBI range instructions.

This field is RES0 for a 64KB translation granule.

The reset behavior of this field is:



Otherwise:

Reserved, RES0, and the Effective value of this bit is 0b0.

TCMA1, bit [58]

When FEAT_MTE2 is implemented:

Controls the generation of Unchecked accesses at EL2, and at EL0 if HCR_EL2.TGE=1, when address[59:55] = 0b11111.

TCMA1Meaning
0b0

This control has no effect on the generation of Unchecked accesses at EL2 or EL0.

0b1

All accesses are Unchecked.

Note

Software may change this control bit on a context switch.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

TCMA0, bit [57]

When FEAT_MTE2 is implemented:

Controls the generation of Unchecked accesses at EL2, and at EL0 if HCR_EL2.TGE=1, when address[59:55] = 0b00000.

TCMA0Meaning
0b0

This control has no effect on the generation of Unchecked accesses at EL2 or EL0.

0b1

All accesses are Unchecked.

Note

Software may change this control bit on a context switch.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

E0PD1, bit [56]

When FEAT_E0PD is implemented:

Faulting control for Unprivileged access to any address translated by TTBR1_EL2.

E0PD1Meaning
0b0

Unprivileged access to any address translated by TTBR1_EL2 will not generate a fault by this mechanism.

0b1

Unprivileged access to any address translated by TTBR1_EL2 will generate a level 0 Translation fault.

Level 0 Translation faults generated as a result of this field are not counted as TLB misses for performance monitoring. The fault should take the same time to generate, whether the address is present in the TLB or not, to mitigate attacks that use fault timing.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

E0PD0, bit [55]

When FEAT_E0PD is implemented:

Faulting control for Unprivileged access to any address translated by TTBR0_EL2.

E0PD0Meaning
0b0

Unprivileged access to any address translated by TTBR0_EL2 will not generate a fault by this mechanism.

0b1

Unprivileged access to any address translated by TTBR0_EL2 will generate a level 0 Translation fault.

Level 0 Translation faults generated as a result of this field are not counted as TLB misses for performance monitoring. The fault should take the same time to generate, whether the address is present in the TLB or not, to mitigate attacks that use fault timing.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

NFD1, bit [54]

When FEAT_SVE is implemented or FEAT_TME is implemented:

Non-Fault translation timing Disable when using TTBR1_EL2.

Controls how a TLB miss is reported in response to a non-fault unprivileged access for a virtual address that is translated using TTBR1_EL2.

If SVE is implemented, the affected access types include:

If FEAT_TME is implemented, the affected access types include all accesses generated by a load or store instruction in Transactional state.

NFD1Meaning
0b0

Does not affect the handling of a TLB miss on accesses translated using TTBR1_EL2.

0b1

A TLB miss on a virtual address that is translated using TTBR1_EL2 due to the specified access types causes the access to fail without taking an exception. The amount of time that the failure takes to be handled should not predictively leak whether it was caused by a TLB miss or a Permission fault, to mitigate attacks that use fault timing.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

NFD0, bit [53]

When FEAT_SVE is implemented or FEAT_TME is implemented:

Non-Fault translation timing Disable when using TTBR0_EL2.

Controls how a TLB miss is reported in response to a non-fault unprivileged access for a virtual address that is translated using TTBR0_EL2.

If SVE is implemented, the affected access types include:

If FEAT_TME is implemented, the affected access types include all accesses generated by a load or store instruction in Transactional state.

NFD0Meaning
0b0

Does not affect the handling of a TLB miss on accesses translated using TTBR0_EL2.

0b1

A TLB miss on a virtual address that is translated using TTBR0_EL2 due to the specified access types causes the access to fail without taking an exception. The amount of time that the failure takes to be handled should not predictively leak whether it was caused by a TLB miss or a Permission fault, to mitigate attacks that use fault timing.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

TBID1, bit [52]

When FEAT_PAuth is implemented:

Controls the use of the top byte of instruction addresses for address matching.

For the purpose of this field, all cache maintenance and address translation instructions that perform address translation are treated as data accesses.

For more information, see 'Address tagging'.

TBID1Meaning
0b0

TCR_EL2.TBI1 applies to Instruction and Data accesses.

0b1

TCR_EL2.TBI1 applies to Data accesses only.

This affects addresses where the address would be translated by tables pointed to by TTBR1_EL2.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

TBID0, bit [51]

When FEAT_PAuth is implemented:

Controls the use of the top byte of instruction addresses for address matching.

For more information, see 'Address tagging'.

TBID0Meaning
0b0

TCR_EL2.TBI0 applies to Instruction and Data accesses.

0b1

TCR_EL2.TBI0 applies to Data accesses only.

This affects addresses where the address would be translated by tables pointed to by TTBR0_EL2.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU162, bit [50]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[62] of the stage 1 translation table Block or Page entry for translations using TTBR1_EL2.

HWU162Meaning
0b0

For translations using TTBR1_EL2, bit[62] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

For translations using TTBR1_EL2, bit[62] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD1 is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD1 is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU161, bit [49]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[61] of the stage 1 translation table Block or Page entry for translations using TTBR1_EL2.

HWU161Meaning
0b0

For translations using TTBR1_EL2, bit[61] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

For translations using TTBR1_EL2, bit[61] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD1 is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD1 is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU160, bit [48]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[60] of the stage 1 translation table Block or Page entry for translations using TTBR1_EL2.

HWU160Meaning
0b0

For translations using TTBR1_EL2, bit[60] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

For translations using TTBR1_EL2, bit[60] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD1 is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD1 is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU159, bit [47]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[59] of the stage 1 translation table Block or Page entry for translations using TTBR1_EL2.

HWU159Meaning
0b0

For translations using TTBR1_EL2, bit[59] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

For translations using TTBR1_EL2, bit[59] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD1 is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD1 is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU062, bit [46]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[62] of the stage 1 translation table Block or Page entry for translations using TTBR0_EL1.

HWU062Meaning
0b0

For translations using TTBR0_EL1, bit[62] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

For translations using TTBR0_EL1, bit[62] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD0 is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD0 is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU061, bit [45]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[61] of the stage 1 translation table Block or Page entry for translations using TTBR0_EL1.

HWU061Meaning
0b0

For translations using TTBR0_EL1, bit[61] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

For translations using TTBR0_EL1, bit[61] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD0 is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD0 is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU060, bit [44]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[60] of the stage 1 translation table Block or Page entry for translations using TTBR0_EL1.

HWU060Meaning
0b0

For translations using TTBR0_EL1, bit[60] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

For translations using TTBR0_EL1, bit[60] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD0 is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD0 is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HWU059, bit [43]

When FEAT_HPDS2 is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[59] of the stage 1 translation table Block or Page entry for translations using TTBR0_EL1.

HWU059Meaning
0b0

For translations using TTBR0_EL1, bit[59] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

For translations using TTBR0_EL1, bit[59] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TCR_EL2.HPD0 is 1.

The Effective value of this field is 0 if the value of TCR_EL2.HPD0 is 0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HPD1, bit [42]

When FEAT_HPDS is implemented:

Hierarchical Permission Disables. This affects the hierarchical control bits, APTable, PXNTable, and UXNTable, except NSTable, in the translation tables pointed to by TTBR1_EL2.

HPD1Meaning
0b0

Hierarchical permissions are enabled.

0b1

Hierarchical permissions are disabled.

When disabled, the permissions are treated as if the bits are zero.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HPD0, bit [41]

When FEAT_HPDS is implemented:

Hierarchical Permission Disables. This affects the hierarchical control bits, APTable, PXNTable, and UXNTable, except NSTable, in the translation tables pointed to by TTBR0_EL2.

HPD0Meaning
0b0

Hierarchical permissions are enabled.

0b1

Hierarchical permissions are disabled.

When disabled, the permissions are treated as if the bits are zero.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HD, bit [40]

When FEAT_HAFDBS is implemented:

Hardware management of dirty state in stage 1 translations from EL2.

HDMeaning
0b0

Stage 1 hardware management of dirty state disabled.

0b1

Stage 1 hardware management of dirty state enabled, only if the HA bit is also set to 1.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HA, bit [39]

When FEAT_HAFDBS is implemented:

Hardware Access flag update in stage 1 translations from EL2.

HAMeaning
0b0

Stage 1 Access flag update disabled.

0b1

Stage 1 Access flag update enabled.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

TBI1, bit [38]

Top Byte Ignored. Indicates whether the top byte of an address is used for address match for the TTBR1_EL2 region, or ignored and used for tagged addresses.

For more information, see 'Address tagging'.

TBI1Meaning
0b0

Top Byte used in the address calculation.

0b1

Top Byte ignored in the address calculation.

This affects addresses generated in EL0 and EL2 using AArch64 where the address would be translated by tables pointed to by TTBR1_EL2. It has an effect whether the EL2, or EL2&0, translation regime is enabled or not.

If FEAT_PAuth is implemented and TCR_EL2.TBID1 is 1, then this field only applies to Data accesses.

If the value of TBI1 is 1 and bit [55] of the target address to be stored to the PC is 1, then bits[63:56] of that target address are also set to 1 before the address is stored in the PC, in the following cases:

The reset behavior of this field is:

TBI0, bit [37]

Top Byte Ignored. Indicates whether the top byte of an address is used for address match for the TTBR0_EL2 region, or ignored and used for tagged addresses.

For more information, see 'Address tagging'.

TBI0Meaning
0b0

Top Byte used in the address calculation.

0b1

Top Byte ignored in the address calculation.

This affects addresses generated in EL0 and EL2 using AArch64 where the address would be translated by tables pointed to by TTBR0_EL2. It has an effect whether the EL2, or EL2&0, translation regime is enabled or not.

If FEAT_PAuth is implemented and TCR_EL2.TBID0 is 1, then this field only applies to Data accesses.

If the value of TBI0 is 1 and bit [55] of the target address to be stored to the PC is 0, then bits[63:56] of that target address are also set to 0 before the address is stored in the PC, in the following cases:

The reset behavior of this field is:

AS, bit [36]

ASID Size.

ASMeaning
0b0

8 bit - the upper 8 bits of TTBR0_EL2 and TTBR1_EL2 are ignored by hardware for every purpose except reading back the register, and are treated as if they are all zeros for when used for allocation and matching entries in the TLB.

0b1

16 bit - the upper 16 bits of TTBR0_EL2 and TTBR1_EL2 are used for allocation and matching in the TLB.

If the implementation has only 8 bits of ASID, this field is RES0.

The reset behavior of this field is:

Bit [35]

Reserved, RES0.

IPS, bits [34:32]

Intermediate Physical Address Size.

IPSMeaningApplies when
0b000

32 bits, 4GB.

0b001

36 bits, 64GB.

0b010

40 bits, 1TB.

0b011

42 bits, 4TB.

0b100

44 bits, 16TB.

0b101

48 bits, 256TB.

0b110

52 bits, 4PB.

When FEAT_LPA is implemented

All other values are reserved.

The reserved values behave in the same way as the 0b101 or 0b110 encoding, but software must not rely on this property as the behavior of the reserved values might change in a future revision of the architecture.

If the translation granule is not 64KB, the value 0b110 is treated as reserved.

It is IMPLEMENTATION DEFINED whether an implementation that does not implement FEAT_LPA supports setting the value of 0b110 for the 64KB translation granule size or whether setting this value behaves as the 0b101 encoding.

If the value of ID_AA64MMFR0_EL1.PARange is 0b0110, and the value of this field is not 0b110 or a value treated as 0b110, then bits[51:48] of every translation table base address for the stage of translation controlled by TCR_EL2 are 0b0000.

The reset behavior of this field is:

TG1, bits [31:30]

Granule size for the TTBR1_EL2.

TG1Meaning
0b01

16KB.

0b10

4KB.

0b11

64KB.

Other values are reserved.

If the value is programmed to either a reserved value, or a size that has not been implemented, then the hardware will treat the field as if it has been programmed to an IMPLEMENTATION DEFINED choice of the sizes that has been implemented for all purposes other than the value read back from this register.

It is IMPLEMENTATION DEFINED whether the value read back is the value programmed or the value that corresponds to the size chosen.

The reset behavior of this field is:

SH1, bits [29:28]

Shareability attribute for memory associated with translation table walks using TTBR1_EL2.

SH1Meaning
0b00

Non-shareable.

0b10

Outer Shareable.

0b11

Inner Shareable.

Other values are reserved. The effect of programming this field to a Reserved value is that behavior is CONSTRAINED UNPREDICTABLE.

The reset behavior of this field is:

ORGN1, bits [27:26]

Outer cacheability attribute for memory associated with translation table walks using TTBR1_EL2.

ORGN1Meaning
0b00

Normal memory, Outer Non-cacheable.

0b01

Normal memory, Outer Write-Back Read-Allocate Write-Allocate Cacheable.

0b10

Normal memory, Outer Write-Through Read-Allocate No Write-Allocate Cacheable.

0b11

Normal memory, Outer Write-Back Read-Allocate No Write-Allocate Cacheable.

The reset behavior of this field is:

IRGN1, bits [25:24]

Inner cacheability attribute for memory associated with translation table walks using TTBR1_EL2.

IRGN1Meaning
0b00

Normal memory, Inner Non-cacheable.

0b01

Normal memory, Inner Write-Back Read-Allocate Write-Allocate Cacheable.

0b10

Normal memory, Inner Write-Through Read-Allocate No Write-Allocate Cacheable.

0b11

Normal memory, Inner Write-Back Read-Allocate No Write-Allocate Cacheable.

The reset behavior of this field is:

EPD1, bit [23]

Translation table walk disable for translations using TTBR1_EL2. This bit controls whether a translation table walk is performed on a TLB miss, for an address that is translated using TTBR1_EL2. The encoding of this bit is:

EPD1Meaning
0b0

Perform translation table walks using TTBR1_EL2.

0b1

A TLB miss on an address that is translated using TTBR1_EL2 generates a Translation fault. No translation table walk is performed.

The reset behavior of this field is:

A1, bit [22]

Selects whether TTBR0_EL2 or TTBR1_EL2 defines the ASID. The encoding of this bit is:

A1Meaning
0b0

TTBR0_EL2.ASID defines the ASID.

0b1

TTBR1_EL2.ASID defines the ASID.

The reset behavior of this field is:

T1SZ, bits [21:16]

The size offset of the memory region addressed by TTBR1_EL2. The region size is 2(64-T1SZ) bytes.

The maximum and minimum possible values for T1SZ depend on the level of translation table and the memory translation granule size, as described in the AArch64 Virtual Memory System Architecture chapter.

Note

For the 4KB translation granule, if FEAT_LPA2 is implemented and this field is less than 16, the translation table walk begins with a level -1 initial lookup.

For the 16KB translation granule, if FEAT_LPA2 is implemented and this field is less than 17, the translation table walk begins with a level 0 initial lookup.

The reset behavior of this field is:

TG0, bits [15:14]

Granule size for the TTBR0_EL2.

TG0Meaning
0b00

4KB.

0b01

64KB.

0b10

16KB.

Other values are reserved.

If the value is programmed to either a reserved value, or a size that has not been implemented, then the hardware will treat the field as if it has been programmed to an IMPLEMENTATION DEFINED choice of the sizes that has been implemented for all purposes other than the value read back from this register.

It is IMPLEMENTATION DEFINED whether the value read back is the value programmed or the value that corresponds to the size chosen.

The reset behavior of this field is:

SH0, bits [13:12]

Shareability attribute for memory associated with translation table walks using TTBR0_EL2.

SH0Meaning
0b00

Non-shareable.

0b10

Outer Shareable.

0b11

Inner Shareable.

Other values are reserved. The effect of programming this field to a Reserved value is that behavior is CONSTRAINED UNPREDICTABLE.

The reset behavior of this field is:

ORGN0, bits [11:10]

Outer cacheability attribute for memory associated with translation table walks using TTBR0_EL2.

ORGN0Meaning
0b00

Normal memory, Outer Non-cacheable.

0b01

Normal memory, Outer Write-Back Read-Allocate Write-Allocate Cacheable.

0b10

Normal memory, Outer Write-Through Read-Allocate No Write-Allocate Cacheable.

0b11

Normal memory, Outer Write-Back Read-Allocate No Write-Allocate Cacheable.

The reset behavior of this field is:

IRGN0, bits [9:8]

Inner cacheability attribute for memory associated with translation table walks using TTBR0_EL2.

IRGN0Meaning
0b00

Normal memory, Inner Non-cacheable.

0b01

Normal memory, Inner Write-Back Read-Allocate Write-Allocate Cacheable.

0b10

Normal memory, Inner Write-Through Read-Allocate No Write-Allocate Cacheable.

0b11

Normal memory, Inner Write-Back Read-Allocate No Write-Allocate Cacheable.

The reset behavior of this field is:

EPD0, bit [7]

Translation table walk disable for translations using TTBR0_EL2. This bit controls whether a translation table walk is performed on a TLB miss, for an address that is translated using TTBR0_EL2. The encoding of this bit is:

EPD0Meaning
0b0

Perform translation table walks using TTBR0_EL2.

0b1

A TLB miss on an address that is translated using TTBR0_EL2 generates a Translation fault. No translation table walk is performed.

The reset behavior of this field is:

Bit [6]

Reserved, RES0.

T0SZ, bits [5:0]

The size offset of the memory region addressed by TTBR0_EL2. The region size is 2(64-T0SZ) bytes.

The maximum and minimum possible values for T0SZ depend on the level of translation table and the memory translation granule size, as described in the AArch64 Virtual Memory System Architecture chapter.

Note

For the 4KB translation granule, if FEAT_LPA2 is implemented and this field is less than 16, the translation table walk begins with a level -1 initial lookup.

For the 16KB translation granule, if FEAT_LPA2 is implemented and this field is less than 17, the translation table walk begins with a level 0 initial lookup.

The reset behavior of this field is:

Accessing TCR_EL2

When the Effective value of HCR_EL2.E2H is 1, without explicit synchronization, access from EL2 using the mnemonic TCR_EL2 or TCR_EL1 are not guaranteed to be ordered with respect to accesses using the other mnemonic.

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

MRS <Xt>, TCR_EL2

op0op1CRnCRmop2
0b110b1000b00100b00000b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then X[t, 64] = TCR_EL2; elsif PSTATE.EL == EL3 then X[t, 64] = TCR_EL2;

MSR TCR_EL2, <Xt>

op0op1CRnCRmop2
0b110b1000b00100b00000b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then TCR_EL2 = X[t, 64]; elsif PSTATE.EL == EL3 then TCR_EL2 = X[t, 64];

When FEAT_VHE is implemented

MRS <Xt>, TCR_EL1

op0op1CRnCRmop2
0b110b0000b00100b00000b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.TRVM == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGRTR_EL2.TCR_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() == '111' then X[t, 64] = NVMem[0x120]; else X[t, 64] = TCR_EL1; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then X[t, 64] = TCR_EL2; else X[t, 64] = TCR_EL1; elsif PSTATE.EL == EL3 then X[t, 64] = TCR_EL1;

When FEAT_VHE is implemented

MSR TCR_EL1, <Xt>

op0op1CRnCRmop2
0b110b0000b00100b00000b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.TVM == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGWTR_EL2.TCR_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() == '111' then NVMem[0x120] = X[t, 64]; else TCR_EL1 = X[t, 64]; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then TCR_EL2 = X[t, 64]; else TCR_EL1 = X[t, 64]; elsif PSTATE.EL == EL3 then TCR_EL1 = X[t, 64];