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VTCR_EL2: Virtualization Translation Control Register

Purpose

The control register for stage 2 of the EL1&0 translation regime.

Configuration

AArch64 System register VTCR_EL2 bits [31:0] are architecturally mapped to AArch32 System register VTCR[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

VTCR_EL2 is a 64-bit register.

Field descriptions

6362616059585756555453525150494847464544434241403938373635343332
313029282726252423222120191817161514131211109876543210
RES0HDBSSHAFTRES0TL0GCSHRES0D128S2POES2PIETL1AssuredOnlySL2DS
RES1NSANSWHWU62HWU61HWU60HWU59RES0HDHARES0VSPSTG0SH0ORGN0IRGN0SL0T0SZ

Unless stated otherwise, any of the bits in VTCR_EL2 are permitted to be cached in a TLB.

Bits [63:46]

Reserved, RES0.

HDBSS, bit [45]

When FEAT_HDBSS is implemented:

Enable use of HDBSS.

HDBSSMeaning
0b0

Hardware tracking of Dirty state Structure is disabled.

0b1

Hardware tracking of Dirty state Structure is enabled.

If VTCR_EL2.{HA, HD} is not {1, 1}, the Effective value of this field is 0.

If SCR_EL3.HDBSSEn is 0, then this field behaves as 0 for all purposes other than a direct read of the value of this bit.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

HAFT, bit [44]

When FEAT_HAFT is implemented:

Hardware managed Access Flag for Table descriptors.

Enables the Hardware managed Access Flag for Table descriptors.

HAFTMeaning
0b0

Hardware managed Access Flag for Table descriptors is disabled.

0b1

Hardware managed Access Flag for Table descriptors is enabled.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

Bits [43:42]

Reserved, RES0.

TL0, bit [41]

When FEAT_THE is implemented:

Control bit to check for presence of MMU TopLevel0 permission attribute.

TL0Meaning
0b0

This bit does not have any effect on stage 2 translations.

0b1

Enables MMU TopLevel0 permission attribute check for TTBR0_EL1 and TTBR1_EL1 translations.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

GCSH, bit [40]

When FEAT_THE is implemented and FEAT_GCS is implemented:

Assured stage 1 translations for Guarded Control Stacks. Enforces use of the AssuredOnly attribute in stage 2 for the memory accessed by privileged Guarded Control Stack data accesses.

GCSHMeaning
0b0

For the memory accessed by privileged Guarded Control Stack data accesses, the AssuredOnly attribute in stage 2 is not required to be set.

0b1

For the memory accessed by privileged Guarded Control Stack data accesses, the AssuredOnly attribute in stage 2 is required to be set.

This bit is permitted to be cached in a TLB.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

Bit [39]

Reserved, RES0.

D128, bit [38]

When FEAT_D128 is implemented:

Enables VMSAv9-128 translation system for stage 2 translation.

D128Meaning
0b0

Translation system follows VMSA-64 translation process.

0b1

Translation system follows VMSAv9-128 translation process.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

S2POE, bit [37]

When FEAT_S2POE is implemented:

Enable Permission Overlay. Enables permission overlay in stage 2 Permission model.

S2POEMeaning
0b0

Overlay disabled.

0b1

Overaly enabled.

This bit is not permitted to be cached in a TLB.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

S2PIE, bit [36]

When FEAT_S2PIE is implemented:

Select Permission Model. Enables usage of permission indirection in stage 2 Permission model.

S2PIEMeaning
0b0

Direct permission model.

0b1

Indirect permission model.

This field is RES1 when VTCR_EL2.D128 is set.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

TL1, bit [35]

When FEAT_THE is implemented:

Control bit to check for presence of MMU TopLevel1 permission attribute.

TL1Meaning
0b0

This bit does not have any effect on stage 2 translations.

0b1

Enables MMU TopLevel1 permission attribute check for TTBR0_EL1 and TTBR1_EL1 translations.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

AssuredOnly, bit [34]

When FEAT_THE is implemented:

AssuredOnly attribute enable for VMSAv8-64. Configures use of bit[58] of the stage 2 translation table Block or Page descriptor.

AssuredOnlyMeaning
0b0

Bit[58] of each stage 2 translation Block or Page descriptor does not indicate AssuredOnly attribute.

0b1

Bit[58] of each stage 2 translation Block or Page descriptor indicates AssuredOnly attribute.

This field is RES0 when VTCR_EL2.D128 is 1.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

SL2, bit [33]

When FEAT_LPA2 is implemented and (FEAT_D128 is not implemented or VTCR_EL2.D128 == 0):

Starting level of the stage 2 translation lookup controlled by VTCR_EL2.

If VTCR_EL2.DS == 1, then VTCR_EL2.SL2, in combination with VTCR_EL2.SL0, gives encodings for the stage 2 translation table walk initial lookup level.

If VTCR_EL2.DS == 0, then VTCR_EL2.SL2 is RES0.

If the translation granule size is not 4KB, then this field is RES0.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

DS, bit [32]

When FEAT_LPA2 is implemented and (FEAT_D128 is not implemented or VTCR_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 VTCR_EL2.T0SZ is 16. Any memory access using a smaller value generates a stage 2 level 0 translation table fault.

The minimum value of VSTCR_EL2.T0SZ is 16. Any memory access using a smaller value generates a stage 2 level 0 translation table fault.

Output address[51:48] is 0000.

0b1

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

Bits[9:8] in translation descriptors hold output address[51:50].

The shareability information of Block and Page descriptors for cacheable locations is determined by VTCR_EL2.SH0.

The minimum value of VTCR_EL2.T0SZ is 12. Any memory access using a smaller value generates a stage 2 level 0 translation table fault.

The minimum value of VSTCR_EL2.T0SZ is 12. Any memory access using a smaller value generates a stage 2 level 0 translation table fault.

Note

As FEAT_LPA must be implemented if VTCR_EL2.DS == 1, the minimum values of VTCR_EL2.T0SZ and VSTCR_EL2.T0SZ are 12, as determined by that extension.

For the TLBI range instructions affecting IPA, 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 0000. For the 16KB translation granule, bits[15:14] of BaseADDR are treated as 00.

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.

Bit [31]

Reserved, RES1.

NSA, bit [30]

When FEAT_SEL2 is implemented:

Non-secure stage 2 translation output address space for the Secure EL1&0 translation regime.

NSAMeaning
0b0

All stage 2 translations for the Non-secure IPA space of the Secure EL1&0 translation regime access the Secure PA space.

0b1

All stage 2 translations for the Non-secure IPA space of the Secure EL1&0 translation regime access the Non-secure PA space.

This bit behaves as 1 for all purposes other than reading back the value of the bit when one of the following is true:

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

NSW, bit [29]

When FEAT_SEL2 is implemented:

Non-secure stage 2 translation table address space for the Secure EL1&0 translation regime.

NSWMeaning
0b0

All stage 2 translation table walks for the Non-secure IPA space of the Secure EL1&0 translation regime are to the Secure PA space.

0b1

All stage 2 translation table walks for the Non-secure IPA space of the Secure EL1&0 translation regime are to the Non-secure PA space.

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 2 translation table Block or Page entry.

HWU62Meaning
0b0

Bit[62] of each stage 2 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

Bit[62] of each stage 2 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose.

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 2 translation table Block or Page entry.

HWU61Meaning
0b0

Bit[61] of each stage 2 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

Bit[61] of each stage 2 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose.

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 2 translation table Block or Page entry.

HWU60Meaning
0b0

Bit[60] of each stage 2 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

Bit[60] of each stage 2 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose.

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 2 translation table Block or Page entry.

HWU59Meaning
0b0

Bit[59] of each stage 2 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.

0b1

Bit[59] of each stage 2 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

Bits [24:23]

Reserved, RES0.

HD, bit [22]

When FEAT_HAFDBS is implemented:

Hardware management of dirty state in stage 2 translations when EL2 is enabled in the current Security state.

HDMeaning
0b0

Stage 2 hardware management of dirty state disabled.

0b1

Stage 2 hardware management of dirty state enabled, only if the VTCR_EL2.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 2 translations when EL2 is enabled in the current Security state.

HAMeaning
0b0

Stage 2 Access flag update disabled.

0b1

Stage 2 Access flag update enabled.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

Bit [20]

Reserved, RES0.

VS, bit [19]

When FEAT_VMID16 is implemented:

VMID Size.

VSMeaning
0b0

8-bit VMID. The upper 8 bits of VTTBR_EL2 are ignored by the hardware, and treated as if they are all zeros, for every purpose except when reading back the register.

0b1

16-bit VMID. The upper 8 bits of VTTBR_EL2 are used for allocation and matching in the TLB.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

PS, bits [18:16]

Physical address Size for the second stage of translation.

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

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 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.

In an implementation that supports 52-bit PAs, if 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 VTCR_EL2 are 0b0000.

The reset behavior of this field is:

TG0, bits [15:14]

Granule size for the VTTBR_EL2.

TG0Meaning
0b00

4KB.

0b01

64KB.

0b10

16KB.

Other values are reserved.

If FEAT_GTG is implemented, ID_AA64MMFR0_EL1.{TGran4_2, TGran16_2, TGran64_2} indicate which granule sizes are supported for stage 2 translation.

If FEAT_GTG is not implemented, ID_AA64MMFR0_EL1.{TGran4, TGran16, TGran64} indicate which granule sizes are supported.

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 VTTBR_EL2 or VSTTBR_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 VTTBR_EL2 or VSTTBR_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 VTTBR_EL2 or VSTTBR_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:

SL0, bits [7:6]

When FEAT_TTST is implemented and (FEAT_D128 is not implemented or VTCR_EL2.D128 == 0):

Starting level of the stage 2 translation lookup, controlled by VTCR_EL2. The meaning of this field depends on the value of VTCR_EL2.TG0.

SL0Meaning
0b00

If VTCR_EL2.TG0 is 0b00 (4KB granule):

  • If FEAT_LPA2 is not implemented, start at level 2.

  • If FEAT_LPA2 is implemented and VTCR_EL2.SL2 is 0b0, start at level 2.

  • If FEAT_LPA2 is implemented and VTCR_EL2.SL2 is 0b1, start at level -1.

If VTCR_EL2.TG0 is 0b10 (16KB granule) or 0b01 (64KB granule), start at level 3.

0b01

If VTCR_EL2.TG0 is 0b00 (4KB granule):

  • If FEAT_LPA2 is not implemented, start at level 1.

  • If FEAT_LPA2 is implemented and VTCR_EL2.SL2 is 0b0, start at level 1.

  • If FEAT_LPA2 is implemented, the combination of VTCR_EL2.SL0 == 01 and VTCR_EL2.SL2 == 1 is reserved.

If VTCR_EL2.TG0 is 0b10 (16KB granule) or 0b01 (64KB granule), start at level 2.

0b10

If VTCR_EL2.TG0 is 0b00 (4KB granule):

  • If FEAT_LPA2 is not implemented, start at level 0.

  • If FEAT_LPA2 is implemented and VTCR_EL2.SL2 is 0b0, start at level 0.

  • If FEAT_LPA2 is implemented, the combination of VTCR_EL2.SL0 == 10 and VTCR_EL2.SL2 == 1 is reserved.

If VTCR_EL2.TG0 is 0b10 (16KB granule) or 0b01 (64KB granule), start at level 1.

0b11

If VTCR_EL2.TG0 is 0b00 (4KB granule):

  • If FEAT_LPA2 is not implemented, start at level 3.

  • If FEAT_LPA2 is implemented and VTCR_EL2.SL2 is 0b0, start at level 3.

  • If FEAT_LPA2 is implemented, the combination of VTCR_EL2.SL0 == 11 and VTCR_EL2.SL2 == 1 is reserved.

If VTCR_EL2.TG0 is 0b10 (16KB granule) and FEAT_LPA2 is implemented, start at level 0.

If this field is programmed to a value that is not consistent with the programming of VTCR_EL2.T0SZ, then a stage 2 level 0 Translation fault is generated.

The reset behavior of this field is:



When FEAT_TTST is not implemented and (FEAT_D128 is not implemented or VTCR_EL2.D128 == 0):

Starting level of the stage 2 translation lookup, controlled by VTCR_EL2. The meaning of this field depends on the value of VTCR_EL2.TG0.

SL0Meaning
0b00

If VTCR_EL2.TG0 is 0b00 (4KB granule), start at level 2. If VTCR_EL2.TG0 is 0b10 (16KB granule) or 0b01 (64KB granule), start at level 3.

0b01

If VTCR_EL2.TG0 is 0b00 (4KB granule), start at level 1. If VTCR_EL2.TG0 is 0b10 (16KB granule) or 0b01 (64KB granule), start at level 2.

0b10

If VTCR_EL2.TG0 is 0b00 (4KB granule), start at level 0. If VTCR_EL2.TG0 is 0b10 (16KB granule) or 0b01 (64KB granule), start at level 1.

All other values are reserved. If this field is programmed to a reserved value, or to a value that is not consistent with the programming of VTCR_EL2.T0SZ, then a stage 2 level 0 Translation fault is generated.

The reset behavior of this field is:



Otherwise:

Reserved, RES0.

T0SZ, bits [5:0]

The size offset of the memory region addressed by VTTBR_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'.

If this field is programmed to a value that is not consistent with the programming of SL0, then a stage 2 level 0 Translation fault is generated.

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 VTCR_EL2

Unless stated otherwise, any of the bits in VTCR_EL2 are permitted to be cached in a TLB.

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

MRS <Xt>, VTCR_EL2

op0op1CRnCRmop2
0b110b1000b00100b00010b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() IN {'1x1'} then X[t, 64] = NVMem[0x040]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then X[t, 64] = VTCR_EL2; elsif PSTATE.EL == EL3 then X[t, 64] = VTCR_EL2;

MSR VTCR_EL2, <Xt>

op0op1CRnCRmop2
0b110b1000b00100b00010b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() IN {'1x1'} then NVMem[0x040] = X[t, 64]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then VTCR_EL2 = X[t, 64]; elsif PSTATE.EL == EL3 then VTCR_EL2 = X[t, 64];