HCR_EL2, Hypervisor Configuration Register

The HCR_EL2 characteristics are:

Purpose

Provides configuration controls for virtualization, including defining whether various operations are trapped to EL2.

Configuration

AArch64 System register HCR_EL2 bits [31:0] are architecturally mapped to AArch32 System register HCR[31:0] .

AArch64 System register HCR_EL2 bits [63:32] are architecturally mapped to AArch32 System register HCR2[31:0] .

If EL2 is not implemented, this register is RES0 from EL3.

The bits in this register behave as if they are 0 for all purposes other than direct reads of the register if EL2 is not enabled in the current Security state.

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

HCR_EL2 is a 64-bit register.

Field descriptions

The HCR_EL2 bit assignments are:

TWEDEL, bits [63:60]

When ARMv8.6-TWED is implemented:

TWE Delay. A 4-bit unsigned number that, when HCR_EL2.TWEDEn is 1, encodes the minimum delay in taking a trap of WFE caused by HCR_EL2.TWE as 2^(TWEDEL + 8) cycles.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

TWEDEn, bit [59]

When ARMv8.6-TWED is implemented:

TWE Delay Enable. Enables a configurable delayed trap of the WFE instruction caused by HCR_EL2.TWE.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

TID5, bit [58]

When ARMv8.5-MemTag is implemented:

Trap ID group 5. Traps the following register accesses to EL2, when EL2 is enabled in the current Security state:

AArch64:

• GMID_EL1.

When the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field has an Effective value of 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

DCT, bit [57]

When ARMv8.5-MemTag is implemented:

Default Cacheability Tagging. When HCR_EL2.DC is in effect, controls whether stage 1 translations are treated as Tagged or Untagged.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

ATA, bit [56]

When ARMv8.5-MemTag is implemented:

Allocation Tag Access. When SCR_EL3.ATA=1 and HCR_EL2.{E2H,TGE} != {1,1}, controls EL1 and EL0 access to Allocation Tags.

When access is prevented:

• Instructions which Load or Store data are Unchecked.

• Instructions which Load or Store Allocation Tags treat the Allocation Tag as RAZ/WI.

• Instructions which insert Logical Address Tags into addresses treat the Allocation Tag used to generate the Logical Address Tag as 0.

• Cache maintenance instructions which invalidate Allocation Tags from caches behave as the equivalent Clean and Invalidate operation on Allocation Tags.

• MRS and MSR instructions at EL1 using GCR_EL1, RGSR_EL1, TFSR_EL1, TFSR_EL2, or TFSRE0_EL1 that are not UNDEFINED are trapped to EL2.

This field is permitted to be cached in a TLB.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

TTLBOS, bit [55]

When ARMv8.2-EVT is implemented:

Trap TLB maintenance instructions that operate on the Outer Shareable domain. Traps execution of those TLB maintenance instructions at EL1 using AArch64 to EL2 when EL2 is enabled in the current Security state. This applies to the following instructions:

TLBI VMALLE1OS, TLBI VAE1OS, TLBI ASIDE1OS,TLBI VAAE1OS, TLBI VALE1OS, TLBI VAALE1OS,TLBI RVAE1OS, TLBI RVAAE1OS,TLBI RVALE1OS, and TLBI RVAALE1OS.

If ARMv8.2-EVT is not implemented, this field is RES0.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

TTLBIS, bit [54]

When ARMv8.2-EVT is implemented:

Trap TLB maintenance instructions that operate on the Inner Shareable domain. Traps execution of those TLB maintenance instructions at EL1 using AArch64, and at EL1 using AArch32, to EL2 when EL2 is enabled in the current Security state. This applies to the following instructions:

• When EL1 is using AArch64, TLBI VMALLE1IS, TLBI VAE1IS, TLBI ASIDE1IS,TLBI VAAE1IS, TLBI VALE1IS, TLBI VAALE1IS,TLBI RVAE1IS, TLBI RVAAE1IS,TLBI RVALE1IS, and TLBI RVAALE1IS.
• When EL1 is using AArch32, TLBIALLIS, TLBIMVAIS, TLBIASIDIS, TLBIMVAAIS, TLBIMVALIS, and TLBIMVAALIS.

If ARMv8.2-EVT is not implemented, this field is RES0.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

EnSCXT, bit [53]

When ARMv8.0-CSV2 is implemented:

Enable Access to the SCXTNUM_EL1 and SCXTNUM_EL0 registers. The defined values are:

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1,1}, this bit has no effect on execution at EL0.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

TOCU, bit [52]

When ARMv8.2-EVT is implemented:

Trap cache maintenance instructions that operate to the Point of Unification. Traps execution of those cache maintenance instructions at EL1 or EL0 using AArch64, and at EL1 using AArch32, to EL2 when EL2 is enabled in the current Security state. This applies to the following instructions:

• When SCTLR_EL1.UCI is 1, HCR_EL2.{TGE, E2H} is not {1, 1}, and EL0 is using AArch64, IC IVAU, DC CVAU.
• When EL1 is using AArch64, IC IVAU, IC IALLU, DC CVAU.
• When EL1 is using AArch32, ICIMVAU, ICIALLU, DCCMVAU.

If the Point of Unification is before any level of data cache, it is IMPLEMENTATION DEFINED whether the execution of any data or unified cache clean by VA to the Point of Unification instruction can be trapped when the value of this control is 1.

If the Point of Unification is before any level of instruction cache, it is IMPLEMENTATION DEFINED whether the execution of any instruction cache invalidate to the Point of Unification instruction can be trapped when the value of this control is 1.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

AMVOFFEN, bit [51]

When ARMv8.6-AMU is implemented:

Activity Monitors Virtual Offsets Enable.

Otherwise:

Reserved, RES0.

TICAB, bit [50]

When ARMv8.2-EVT is implemented:

Trap ICIALLUIS/IC IALLUIS cache maintenance instructions. Traps execution of those cache maintenance instructions at EL1 using AArch64, and at EL1 using AArch32, to EL2 when EL2 is enabled in the current Security state. This applies to the following instructions:

• When EL1 is using AArch64, IC IALLUIS.
• When EL1 is using AArch32, ICIALLUIS.

If ARMv8.2-EVT is not implemented, this field is RES0.

If the Point of Unification is before any level of instruction cache, it is IMPLEMENTATION DEFINED whether the execution of any instruction cache invalidate to the Point of Unification instruction can be trapped when the value of this control is 1.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

TID4, bit [49]

When ARMv8.2-EVT is implemented:

Trap ID group 4. Traps the following register accesses to EL2, when EL2 is enabled in the current Security state:

AArch64:

• EL1 reads of CCSIDR_EL1, CCSIDR2_EL1, CLIDR_EL1, and CSSELR_EL1.
• EL1 writes to CSSELR_EL1.

AArch32:

• EL1 reads of CCSIDR, CCSIDR2, CLIDR, and CSSELR.
• EL1 writes to CSSELR.

If ARMv8.2-EVT is not implemented, this field is RES0.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

Bit [48]

Reserved, RES0.

FIEN, bit [47]

When ARMv8.4-RAS is implemented:

Fault Injection Enable. Unless this bit is set to 1, accesses to the ERXPFGCDN_EL1, ERXPFGCTL_EL1, and ERXPFGF_EL1 registers from EL1 generate a Trap exception to EL2, when EL2 is enabled in the current Security state, reported using EC syndrome value 0x18.

If EL2 is disabled in the current Security state, the Effective value of HCR_EL2.FIEN is 0b1.

If ERRIDR_EL1.NUM is zero, meaning no error records are implemented, or no error record accessible using System registers is owned by a node that implements the RAS Common Fault Injection Model Extension, then this bit might be RES0.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

FWB, bit [46]

When ARMv8.4-S2FWB is implemented:

Defines the combined cacheability attributes in a 2 stage translation regime.

In Secure state, this bit applies to both the Secure stage 2 translation and the Non-secure stage 2 translation.

This bit is permitted to be cached in a TLB.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

NV2, bit [45]

When ARMv8.4-NV is implemented:

Nested Virtualization. Changes the behaviors of HCR_EL2.{NV, NV1} to provide a mechanism for hardware to transform reads and writes from System registers into reads and writes from memory.

When this bit is 0, the behavior of HCR_EL2.{NV, NV1} is as defined for ARMv8.3-NV.

When this is bit is 1, then any exception taken from EL1 and taken to EL1 causes SPSR_EL1.M[3:2] to be set to 0b10 and not 0b01

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

AT, bit [44]

When ARMv8.3-NV is implemented:

Address Translation. EL1 execution of the following address translation instructions is trapped to EL2, when EL2 is enabled in the current Security state, reported using EC syndrome value 0x18:

• AT S1E0R, AT S1E0W, AT S1E1R, AT S1E1W, AT S1E1RP, AT S1E1WP

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

NV1, bit [43]

When ARMv8.4-NV is implemented:

Nested Virtualization.

If HCR_EL2.NV2 is 1, the value of HCR_EL2.NV1 defines which EL1 register accesses are transformed to loads and stores. These transformed accesses have priority over the trapping of registers.

The trapping of EL1 registers caused by other control bits has priority over the transformation of these accesses.

If a register is specified that is not implemented by an implementation, then access to that register are UNDEFINED.

For the list of registers affected, see Enhanced support for nested virtualization.

If HCR_EL2.{NV, NV1, NV2} are {1, 0, 0},any exception taken from EL1, and taken to EL1, causes the SPSR_EL1.M[3:2] to be set to 0b10, and not 0b01.

If HCR_EL2.{NV, NV1, NV2} are {1, 1, 0}, then:

• The EL1 translation table Block and Page descriptors:
  • Bit[54] holds the PXN instead of the UXN.
  • Bit[53] is RES0.
  • Bit[6] is treated as 0 regardless of the actual value.
• If Hierarchical Permissions are enabled, the EL1 translation table Table descriptors are as follows:
  • Bit[61] is treated as 0 regardless of the actual value.
  • Bit[60] holds the PXNTable instead of the UXNTable.
  • Bit[59] is RES0.
• When executing at EL1, the PSTATE.PAN bit is treated as zero for all purposes except reading the value of the bit.
• When executing at EL1, the LDTR* instructions are treated as the equivalent LDR* instructions, and the STTR* instructions are treated as the equivalent STR* instructions.

If HCR_EL2.{NV, NV1, NV2} are {0, 1, 0}, then the behavior is a CONSTRAINED UNPREDICTABLE choice of:

• Behaving as if HCR_EL2.NV is 1 and HCR_EL2.NV1 is 1 for all purposes other than reading than reading back the value of the HCR_EL2.NV bit.
• Behaving as if HCR_EL2.NV is 0 and HCR_EL2.NV1 is 0 for all purposes other than reading than reading back the value of the HCR_EL2.NV1 bit.
• Behaving with regard to the HCR_EL2.NV and HCR_EL2.NV1 bits behavior as defined in the rest of this description.

This bit is permitted to be cached in a TLB.

This field resets to an architecturally UNKNOWN value.

When ARMv8.3-NV is implemented:

Nested Virtualization. EL1 accesses to certain registers are trapped to EL2, when EL2 is enabled in the current Security state.

If HCR_EL2.NV is 1 and HCR_EL2.NV1 is 0 then the following effects also apply:

• Any exception taken from EL1, and taken to EL1, causes the SPSR_EL1.M[3:2] to be set to 0b10, and not 0b01.

If the bits HCR_EL2.NV and HCR_EL2.NV1 are both set to 1 then following effects also apply:

• The EL1 translation table Block and Page descriptors:
  • Bit[54] holds the PXN instead of the UXN.
  • Bit[53] is RES0.
  • Bit[6] is treated as 0 regardless of the actual value.
• If Hierarchical Permissions are enabled, the EL1 translation table Table descriptors are as follows:
  • Bit[61] is treated as 0 regardless of the actual value.
  • Bit[60] holds the PXNTable instead of the UXNTable.
  • Bit[59] is RES0.
• When executing at EL1, the PSTATE.PAN bit is treated as zero for all purposes except reading the value of the bit.
• When executing at EL1, the LDTR* instructions are treated as the equivalent LDR* instructions, and the STTR* instructions are treated as the equivalent STR* instructions.

If HCR_EL2.NV is 0 and HCR_EL2.NV1 is 1 then the behavior is a CONSTRAINED UNPREDICTABLE choice of:

• Behaving as if HCR_EL2.NV is 1 and HCR_EL2.NV1 is 1 for all purposes other than reading than reading back the value of the HCR_EL2.NV bit.
• Behaving as if HCR_EL2.NV is 0 and HCR_EL2.NV1 is 0 for all purposes other than reading than reading back the value of the HCR_EL2.NV1 bit.
• Behaving with regard to the HCR_EL2.NV and HCR_EL2.NV1 bits behavior as defined in the rest of this description.

This bit is permitted to be cached in a TLB.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

NV, bit [42]

When ARMv8.4-NV is implemented:

Nested Virtualization.

When HCR_EL2.NV2 is 1, redefines register accesses so that:

• Instructions accessing the Special purpose registers SPSR_EL2 and ELR_EL2 instead access SPSR_EL1 and ELR_EL1 respectively.
• Instructions accessing the System registers ESR_EL2 and FAR_EL2 instead access ESR_EL1 and FAR_EL1.

When HCR_EL2.NV2 is 0, or if ARMv8.4-NV is not implemented, traps functionality that is permitted at EL2 and would be UNDEFINED at EL1 if this field was 0, when EL2 is enabled in the current Security state. This applies to the following operations:

• EL1 accesses to Special-purpose registers that are not UNDEFINED at EL2.
• EL1 accesses to System registers that are not UNDEFINED at EL2.
• Execution of EL1 or EL2 translation regime address translation and TLB maintenance instructions for EL2 and above.

When HCR_EL2.NV2 is 0, or if ARMv8.4-NV is not implemented, then:

• The System or Special-purpose registers for which accesses are trapped and reported using EC syndrome value 0x18 are as follows:
  • Registers accessed using MRS or MSR with a name ending in _EL2, except SP_EL2.
  • Registers accessed using MRS or MSR with a name ending in _EL12.
  • Registers accessed using MRS or MSR with a name ending in _EL02.
  • Special-purpose registers SPSR_irq, SPSR_abt, SPSR_und and SPSR_fiq, accessed using MRS or MSR.
  • Special-purpose register SP_EL1 accessed using the dedicated MRS or MSR instruction.
• The instructions for which the execution is trapped and reported using EC syndrome value 0x18 are as follows:
  • EL2 translation regime Address Translation instructions and TLB maintenance instructions.
  • EL1 translation regime Address Translation instructions and TLB maintenance instructions that are only accessible from EL2 and EL3.
• The instructions for which the execution is trapped as follows:
  • SMC in an implementation that does not include EL3 and when HCR_EL2.TSC is 1. HCR_EL2.TSC bit is not RES0 in this case. This is reported using EC syndrome value 0x17.
  • The ERET, ERETAA, and ERETAB instructions, reported using EC syndrome value 0x1A.

This field resets to an architecturally UNKNOWN value.

When ARMv8.3-NV is implemented:

Nested Virtualization. Traps functionality that is permitted at EL2 and would be UNDEFINED at EL1 if this field was 0, when EL2 is enabled in the current Security state. This applies to the following operations:

• EL1 accesses to Special-purpose registers that are not UNDEFINED at EL2.
• EL1 accesses to System registers that are not UNDEFINED at EL2.
• Execution of EL1 or EL2 translation regime address translation and TLB maintenance instructions for EL2 and above.

The possible values are:

The System or Special-purpose registers for which accesses are trapped and reported using EC syndrome value 0x18 are as follows:

• Registers accessed using MRS or MSR with a name ending in _EL2, except SP_EL2.
• Registers accessed using MRS or MSR with a name ending in _EL12.
• Registers accessed using MRS or MSR with a name ending in _EL02.
• Special-purpose registers SPSR_irq, SPSR_abt, SPSR_und and SPSR_fiq, accessed using MRS or MSR.
• Special-purpose register SP_EL1 accessed using the dedicated MRS or MSR instruction.

The instructions for which the execution is trapped and reported using EC syndrome value 0x18 are as follows:

• EL2 translation regime Address Translation instructions and TLB maintenance instructions.
• EL1 translation regime Address Translation instructions and TLB maintenance instructions that are only accessible from EL2 and EL3.

The execution of the ERET, ERETAA, and ERETAB instructions are trapped and reported using EC syndrome value 0x1A

The execution of the SMC instructions in an implementation that does not include EL3 and when HCR_EL2.TSC is 1 are trapped and reported using EC syndrome value 0x17. HCR_EL2.TSC bit is not RES0 in this case.

This bit is permitted to be cached in a TLB.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

API, bit [41]

When ARMv8.3-PAuth is implemented:

Controls the use of instructions related to Pointer Authentication:

• In EL0, when HCR_EL2.TGE==0 or HCR_EL2.E2H==0, and the associated SCTLR_EL1.En<N><M>==1.
• In EL1, the associated SCTLR_EL1.En<N><M>==1.

Traps are reported using EC syndrome value 0x09. The Pointer Authentication instructions trapped are:

• AUTDA, AUTDB, AUTDZA, AUTDZB, AUTIA, AUTIA1716, AUTIASP, AUTIAZ, AUTIB, AUTIB1716, AUTIBSP, AUTIBZ, AUTIZA, AUTIZB.
• PACGA, PACDA, PACDB, PACDZA, PACDZB, PACIA, PACIA1716, PACIASP, PACIAZ, PACIB, PACIB1716, PACIBSP, PACIBZ, PACIZA, PACIZB.
• RETAA, RETAB, BRAA, BRAB, BLRAA, BLRAB, BRAAZ, BRABZ, BLRAAZ, BLRABZ.
• ERETAA, ERETAB, LDRAA and LDRAB.

If ARMv8.3-PAuth is implemented but EL2 is not implemented or disabled in the current Security state, the system behaves as if this bit is 1.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

APK, bit [40]

When ARMv8.3-PAuth is implemented:

Trap registers holding "key" values for Pointer Authentication. Traps accesses to the following registers from EL1 to EL2, when EL2 is enabled in the current Security state, reported using EC syndrome value 0x18:

• APIAKeyLo_EL1, APIAKeyHi_EL1, APIBKeyLo_EL1, APIBKeyHi_EL1, APDAKeyLo_EL1, APDAKeyHi_EL1, APDBKeyLo_EL1, APDBKeyHi_EL1, APGAKeyLo_EL1, and APGAKeyHi_EL1.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

Bit [39]

Reserved, RES0.

MIOCNCE, bit [38]

Mismatched Inner/Outer Cacheable Non-Coherency Enable, for the EL1&0 translation regimes.

For more information see 'Mismatched memory attributes' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile, section B2 (The AArch64 Application Level Memory Model).

This field can be implemented as RAZ/WI.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

TEA, bit [37]

Route synchronous External abort exceptions to EL2. If the RAS Extension is implemented, the possible values of this bit are:

When the RAS Extension is not implemented, this field is RES0.

This field resets to an architecturally UNKNOWN value.

TERR, bit [36]

When RAS is implemented:

Trap Error record accesses. Trap accesses to the RAS error registers from EL1 to EL2 as follows:

• If EL1 is using AArch64 state, accesses to the following registers are trapped to EL2, reported using EC syndrome value 0x18:
  • ERRIDR_EL1, ERRSELR_EL1, ERXADDR_EL1, ERXCTLR_EL1, ERXFR_EL1, ERXMISC0_EL1, ERXMISC1_EL1, and ERXSTATUS_EL1.
  • When ARMv8.4-RAS is implemented, ERXMISC2_EL1, and ERXMISC3_EL1.
• If EL1 is using AArch32 state, MCR or MRC accesses are trapped to EL2, reported using EC syndrome value 0x03, MCRR or MRRC accesses are trapped to EL2, reported using EC syndrome value 0x04:
  • ERRIDR, ERRSELR, ERXADDR, ERXADDR2, ERXCTLR, ERXCTLR2, ERXFR, ERXFR2, ERXMISC0, ERXMISC1, ERXMISC2, ERXMISC3, and ERXSTATUS.
  • When ARMv8.4-RAS is implemented, ERXMISC4, ERXMISC5, ERXMISC6, and ERXMISC7.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

TLOR, bit [35]

When ARMv8.1-LOR is implemented:

Trap LOR registers. Traps accesses to the LORSA_EL1, LOREA_EL1, LORN_EL1, LORC_EL1, and LORID_EL1 registers from EL1 to EL2, when EL2 is enabled in the current Security state.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

E2H, bit [34]

When ARMv8.1-VHE is implemented:

EL2 Host. Enables a configuration where a Host Operating System is running in EL2, and the Host Operating System's applications are running in EL0.

For information on the behavior of this bit see Behavior of HCR_EL2.E2H.

This bit is permitted to be cached in a TLB.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

ID, bit [33]

Stage 2 Instruction access cacheability disable. For the EL1&0 translation regime, when EL2 is enabled in the current Security state and HCR_EL2.VM==1, this control forces all stage 2 translations for instruction accesses to Normal memory to be Non-cacheable.

This bit has no effect on the EL2, EL2&0, or EL3 translation regimes.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

CD, bit [32]

Stage 2 Data access cacheability disable. For the EL1&0 translation regime, when EL2 is enabled in the current Security state and HCR_EL2.VM==1, this control forces all stage 2 translations for data accesses and translation table walks to Normal memory to be Non-cacheable.

This bit has no effect on the EL2, EL2&0, or EL3 translation regimes.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

RW, bit [31]

Execution state control for lower Exception levels:

If AArch32 state is not supported by the implementation at EL1, then this bit is RAO/WI.

In an implementation that includes EL3, when EL2 is not enabled in Secure state, the PE behaves as if this bit has the same value as the SCR_EL3.RW bit for all purposes other than a direct read or write access of HCR_EL2.

The RW bit is permitted to be cached in a TLB.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 1 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

TRVM, bit [30]

Trap Reads of Virtual Memory controls. Traps EL1 reads of the virtual memory control registers to EL2, when EL2 is enabled in the current Security state, from both Execution states as follows:

• If EL1 is using AArch64 state, the following registers are trapped to EL2 and reported using EC syndrome value 0x18.

  • SCTLR_EL1, TTBR0_EL1, TTBR1_EL1, TCR_EL1, ESR_EL1, FAR_EL1, AFSR0_EL1, AFSR1_EL1, MAIR_EL1, AMAIR_EL1, CONTEXTIDR_EL1.

• If EL1 is using AArch32 state, accesses using MRC to the following registers are trapped to EL2 and reported using EC syndrome value 0x03, accesses using MRRC are trapped to EL2 and reported using EC syndrome value 0x04:

  • SCTLR, TTBR0, TTBR1, TTBCR, TTBCR2, DACR, DFSR, IFSR, DFAR, IFAR, ADFSR, AIFSR, PRRR, NMRR, MAIR0, MAIR1, AMAIR0, AMAIR1, CONTEXTIDR.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

HCD, bit [29]

HVC instruction disable. Disables EL1 execution of HVC instructions, from both Execution states, when EL2 is enabled in the current Security state, reported using EC syndrome value 0x00.

This bit is only implemented if EL3 is not implemented. Otherwise, it is RES0.

This field resets to an architecturally UNKNOWN value.

TDZ, bit [28]

Trap DC ZVA instructions. Traps EL0 and EL1 execution of DC ZVA instructions to EL2, when EL2 is enabled in the current Security state, from AArch64 state only, reported using EC syndrome value 0x18.

If ARMv8.5-MemTag is implemented, this trap also applies to DC GVA and DC GZVA.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

TGE, bit [27]

Trap General Exceptions, from EL0.

HCR_EL2.TGE must not be cached in a TLB.

This field resets to an architecturally UNKNOWN value.

TVM, bit [26]

Trap Virtual Memory controls. Traps EL1 writes to the virtual memory control registers to EL2, when EL2 is enabled in the current Security state, from both Execution states as follows:

• If EL1 is using AArch64 state, the following registers are trapped to EL2 and reported using EC syndrome value 0x18:

  • SCTLR_EL1, TTBR0_EL1, TTBR1_EL1, TCR_EL1, ESR_EL1, FAR_EL1, AFSR0_EL1, AFSR1_EL1, MAIR_EL1, AMAIR_EL1, CONTEXTIDR_EL1.

• If EL1 is using AArch32 state, accesses using MCR to the following registers are trapped to EL2 and reported using EC syndrome value 0x03, accesses using MCRR are trapped to EL2 and reported using EC syndrome value 0x04:

  • SCTLR, TTBR0, TTBR1, TTBCR, TTBCR2, DACR, DFSR, IFSR, DFAR, IFAR, ADFSR, AIFSR, PRRR, NMRR, MAIR0, MAIR1, AMAIR0, AMAIR1, CONTEXTIDR.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

TTLB, bit [25]

When ARMv8.4-TLBI is implemented:

Trap TLB maintenance instructions. Traps EL1 execution of TLB maintenance instructions to EL2, when EL2 is enabled in the current Security state, from both Execution states as follows:

• When EL1 is using AArch64 state, the following instructions are trapped to EL2 and reported using EC syndrome value 0x18:
  • TLBI VMALLE1, TLBI VAE1, TLBI ASIDE1, TLBI VAAE1, TLBI VALE1, TLBI VAALE1.
  • TLBI VMALLE1IS, TLBI VAE1IS, TLBI ASIDE1IS, TLBI VAAE1IS, TLBI VALE1IS, TLBI VAALE1IS.
  • TLBI VMALLE1OS, TLBI VAE1OS, TLBI ASIDE1OS, TLBI VAAE1OS, TLBI VALE1OS, TLBI VAALE1OS.
  • TLBI RVAE1, TLBI RVAAE1, TLBI RVALE1, TLBI RVAALE1.
  • TLBI RVAE1IS, TLBI RVAAE1IS, TLBI RVALE1IS, TLBI RVAALE1IS.
  • TLBI RVAE1OS, TLBI RVAAE1OS, TLBI RVALE1OS, TLBI RVAALE1OS.
• When EL1 is using AArch32 state, the following instructions are trapped to EL2 and reported using EC syndrome value 0x03:
  • TLBIALLIS, TLBIMVAIS, TLBIASIDIS, TLBIMVAAIS, TLBIMVALIS, TLBIMVAALIS.
  • TLBIALL, TLBIMVA, TLBIASID, TLBIMVAA, TLBIMVAL, TLBIMVAAL
  • ITLBIALL, ITLBIMVA, ITLBIASID.
  • DTLBIALL, DTLBIMVA, DTLBIASID.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Trap TLB maintenance instructions. Traps EL1 execution of TLB maintenance instructions to EL2, when EL2 is enabled in the current Security state, from both Execution states. This applies to the following instructions:

• When EL1 is using AArch64, TLBI VMALLE1IS, TLBI VAE1IS, TLBI ASIDE1IS, TLBI VAAE1IS, TLBI VALE1IS, TLBI VAALE1IS, TLBI VMALLE1, TLBI VAE1, TLBI ASIDE1, TLBI VAAE1, TLBI VALE1, TLBI VAALE1.
• When EL1 is using AArch32, TLBIALLIS, TLBIMVAIS, TLBIASIDIS, TLBIMVAAIS, TLBIMVALIS, TLBIMVAALIS, ITLBIALL, ITLBIMVA, ITLBIASID, DTLBIALL, DTLBIMVA, DTLBIASID, TLBIALL, TLBIMVA, TLBIASID, TLBIMVAA, TLBIMVAL, TLBIMVAAL

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

TPU, bit [24]

Trap cache maintenance instructions that operate to the Point of Unification. Traps execution of those cache maintenance instructions at EL1 or EL0 using AArch64, and at EL1 using AArch32, to EL2 when EL2 is enabled in the current Security state as follows:

• If EL0 is using AArch64 state and the value of SCTLR_EL1.UCI is not 0, the following instructions are trapped to EL2 and reported with EC syndrome value 0x18:
  • IC IVAU, DC CVAU. If the value of SCTLR_EL1.UCI is 0 these instructions are UNDEFINED at EL0 and any resulting exception is higher priority than this trap to EL2.
• If EL1 is using AArch64 state, the following instructions are trapped to EL2 and reported with EC syndrome value 0x18:
  • IC IVAU, IC IALLU, IC IALLUIS, DC CVAU.
• If EL1 is using AArch32 state, the following instructions are trapped to EL2 and reported with EC syndrome value 0x18:
  • ICIMVAU, ICIALLU, ICIALLUIS, DCCMVAU.

If the Point of Unification is before any level of data cache, it is IMPLEMENTATION DEFINED whether the execution of any data or unified cache clean by VA to the Point of Unification instruction can be trapped when the value of this control is 1.

If the Point of Unification is before any level of instruction cache, it is IMPLEMENTATION DEFINED whether the execution of any instruction cache invalidate to the Point of Unification instruction can be trapped when the value of this control is 1.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

TPCP, bit [23]

When ARMv8.2-DCPoP is implemented:

Trap data or unified cache maintenance instructions that operate to the Point of Coherency or Persistence. Traps execution of those cache maintenance instructions at EL1 or EL0 using AArch64, and at EL1 using AArch32, to EL2 when EL2 is enabled in the current Security state as follows:

• If EL0 is using AArch64 state and the value of SCTLR_EL1.UCI is not 0, the following instructions are trapped to EL2 and reported using EC syndrome value 0x18:
  • DC CIVAC, DC CVAC, DC CVAP. If the value of SCTLR_EL1.UCI is 0 these instructions are UNDEFINED at EL0 and any resulting exception is higher priority than this trap to EL2.
• If EL1 is using AArch64 state, the following instructions are trapped to EL2 and reported using EC syndrome value 0x18:
  • DC IVAC, DC CIVAC, DC CVAC, DC CVAP.
• If EL1 is using AArch32 state, the following instructions are trapped to EL2 and reported using EC syndrome value 0x03:
  • DCIMVAC, DCCIMVAC, DCCMVAC.

If ARMv8.2-DCCVADP is implemented, this trap also applies to DC CVADP.

If ARMv8.5-MemTag is implemented, this trap also applies to DC CIGVAC, DC CIGDVAC, DC IGVAC, DC IGDVAC, DC CGVAC, DC CGDVAC, DC CGVAP and DC CGDVAP.

If ARMv8.2-DCCVADP and ARMv8.5-MemTag are implemented, this trap also applies to DC CGVADP and DC CGDVADP.

If the Point of Coherency is before any level of data cache, it is IMPLEMENTATION DEFINED whether the execution of any data or unified cache clean, invalidate, or clean and invalidate instruction that operates by VA to the point of coherency can be trapped when the value of this control is 1.

If HCR_EL2.{E2H, TGE} is set to {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Trap data or unified cache maintenance instructions that operate to the Point of Coherency. Traps execution of those cache maintenance instructions at EL1 or EL0 using AArch64, and at EL1 using AArch32, to EL2 when EL2 is enabled in the current Security state as follows:

• If EL0 is using AArch64 state and the value of SCTLR_EL1.UCI is not 0, accesses to the following registers are trapped and reported using EC syndrome value 0x18:
  • DC CIVAC, DC CVAC. However, if the value of SCTLR_EL1.UCI is 0 these instructions are UNDEFINED at EL0 and any resulting exception is higher priority than this trap to EL2.
• If EL1 is using AArch64 state, accesses to DC IVAC, DC CIVAC, DC CVAC are trapped and reported using EC syndrome value 0x18.
• When EL1 is using AArch32, accesses to DCIMVAC, DCCIMVAC, and DCCMVAC are trapped and reported using EC syndrome value 0x03.

If the Point of Coherency is before any level of data cache, it is IMPLEMENTATION DEFINED whether the execution of any data or unified cache clean, invalidate, or clean and invalidate instruction that operates by VA to the point of coherency can be trapped when the value of this control is 1.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

TSW, bit [22]

Trap data or unified cache maintenance instructions that operate by Set/Way. Traps execution of those cache maintenance instructions at EL1 using AArch64, and at EL1 using AArch32, to EL2 when EL2 is enabled in the current Security state as follows:

• If EL1 is using AArch64 state, accesses to DC ISW, DC CSW, DC CISW are trapped to EL2, reported using EC syndrome value 0x18.
• If EL1 is using AArch32 state, accesses to DCISW, DCCSW, DCCISW are trapped to EL2, reported using EC syndrome value 0x03.

If ARMv8.5-MemTag is implemented, this trap also applies to DC IGSW, DC IGDSW, DC CGSW, DC CGDW, DC CIGSW, and DC CIGDSW.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

TACR, bit [21]

Trap Auxiliary Control Registers. Traps EL1 accesses to the Auxiliary Control Registers to EL2, when EL2 is enabled in the current Security state, from both Execution states as follows:

• If EL1 is using AArch64 state, accesses to ACTLR_EL1 to EL2, are trapped to EL2 and reported using EC syndrome value 0x18.
• If EL1 is using AArch32 state, accesses to ACTLR and, if implemented, ACTLR2 are trapped to EL2 and reported using EC syndrome value 0x03.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

TIDCP, bit [20]

Trap IMPLEMENTATION DEFINED functionality. Traps EL1 accesses to the encodings reserved for IMPLEMENTATION DEFINED functionality to EL2, when EL2 is enabled in the current Security state as follows:

• In AArch64 state, access to any of the encodings in the following reserved encoding spaces are trapped and reported using EC syndrome 0x18:
  • IMPLEMENTATION DEFINED System instructions, which are accessed using SYS and SYSL, with CRn == {11, 15}.
  • IMPLEMENTATION DEFINED System registers, which are accessed using MRS and MSR with the S3_<op1>_<Cn>_<Cm>_<op2> register name.
• In AArch32 state, MCR and MRC access to instructions with the following encodings are trapped and reported using EC syndrome 0x03:
  • All coproc==p15, CRn==c9, opc1 == {0-7}, CRm == {c0-c2, c5-c8}, opc2 == {0-7}.
  • All coproc==p15, CRn==c10, opc1 =={0-7}, CRm == {c0, c1, c4, c8}, opc2 == {0-7}.
  • All coproc==p15, CRn==c11, opc1=={0-7}, CRm == {c0-c8, c15}, opc2 == {0-7}.

When the value of HCR_EL2.TIDCP is 1, it is IMPLEMENTATION DEFINED whether any of this functionality accessed from EL0 is trapped to EL2. If it is not, then it is UNDEFINED, and any attempt to access it from EL0 generates an exception that is taken to EL1.

An implementation can also include IMPLEMENTATION DEFINED registers that provide additional controls, to give finer-grained control of the trapping of IMPLEMENTATION DEFINED features.

This field resets to an architecturally UNKNOWN value.

TSC, bit [19]

Trap SMC instructions. Traps EL1 execution of SMC instructions to EL2, when EL2 is enabled in the current Security state, from both Execution states.

If execution is in AArch64 state the trap is reported using EC syndrome value 0x17 and if execution is in AArch32 state, the trap is reported using EC syndrome value 0x13.

In AArch32 state, the Armv8-A architecture permits, but does not require, this trap to apply to conditional SMC instructions that fail their condition code check, in the same way as with traps on other conditional instructions.

SMC instructions are UNDEFINED at EL0.

If EL3 is not implemented and HCR_EL2.NV is 0, it is IMPLEMENTATION DEFINED whether this bit is:

• RES0.
• Implemented with the functionality as described in HCR_EL2.TSC.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

TID3, bit [18]

Trap ID group 3. Traps EL1 reads of group 3 ID registers to EL2, when EL2 is enabled in the current Security state, as follows:

• In AArch64 state, reads of the following registers are trapped to EL2, reported using EC syndrome value 0x18:

  • ID_PFR0_EL1, ID_PFR1_EL1, ID_DFR0_EL1, ID_AFR0_EL1, ID_MMFR0_EL1, ID_MMFR1_EL1, ID_MMFR2_EL1, ID_MMFR3_EL1, ID_ISAR0_EL1, ID_ISAR1_EL1, ID_ISAR2_EL1, ID_ISAR3_EL1, ID_ISAR4_EL1, ID_ISAR5_EL1, ID_ISAR6_EL1, MVFR0_EL1, MVFR1_EL1, MVFR2_EL1.

  • ID_AA64PFR0_EL1, ID_AA64PFR1_EL1, ID_AA64DFR0_EL1, ID_AA64DFR1_EL1, ID_AA64ISAR0_EL1, ID_AA64ISAR1_EL1, ID_AA64MMFR0_EL1, ID_AA64MMFR1_EL1, ID_AA64MMFR2_EL1, ID_AA64AFR0_EL1, ID_AA64AFR1_EL1, ID_AA64ZFR0_EL1 (where SVE is implemented), and ID_MMFR4_EL1

• In AArch64 state, ID_MMFR4_EL1 and ID_MMFR5_EL1 are trapped to EL2, unless implemented as RAZ, when it is IMPLEMENTATION DEFINED whether accesses to ID_MMFR4_EL1 or ID_MMFR5_EL1 are trapped to EL2, reported using EC syndrome value 0x18.

• In AArch64 state, ID_AA64MMFR2_EL1 and ID_ISAR6_EL1 are trapped to EL2, unless implemented as RAZ, when it is IMPLEMENTATION DEFINED whether accesses to ID_AA64MMFR2_EL1 or ID_ISAR6_EL1 are trapped to EL2, reported using EC syndrome value 0x18.

• In AArch64 state, ID_DFR1_EL1 is trapped to EL2, unless implemented as RAZ, when it is IMPLEMENTATION DEFINED whether accesses to ID_DFR1_EL1 are trapped to EL2, reported using EC syndrome value 0x18.

• In AArch64 state, ID_AA64ZFR0_EL1 is trapped to EL2, unless implemented as RAZ then it is IMPLEMENTATION DEFINED whether accesses to ID_AA64ZFR0_EL1 are trapped to EL2, reported using EC syndrome value 0x18.

• In AArch64 state, it is IMPLEMENTATION DEFINED whether this field traps MRS accesses to encodings in the following range that are not already mentioned in this field description, reported using EC syndrome value 0x18:

  • Op0 == 3, op1 == 0, CRn == c0, CRm == {c2-c7}, op2 == {0-7}.

• In AArch32 state, MRC access to the following registers are trapped to EL2, reported using EC syndrome value 0x03:

  • ID_PFR0, ID_PFR1, ID_DFR0, ID_AFR0, ID_MMFR0, ID_MMFR1, ID_MMFR2, ID_MMFR3, ID_ISAR0, ID_ISAR1, ID_ISAR2, ID_ISAR3, ID_ISAR4, ID_ISAR5, MVFR0, MVFR1, MVFR2, and ID_MMFR4.

• In AArch32 state, VMRS access to MVFR0, MVFR1, and MVFR2, reported using EC syndrome value 0x08.

• In AArch32 state, ID_MMFR4 and ID_MMFR5 are trapped to EL2, unless implemented as RAZ, when it is IMPLEMENTATION DEFINED whether accesses to ID_MMFR4 or ID_MMFR5 are trapped to EL2, reported using EC syndrome value 0x03.

• In AArch32 state, ID_ISAR6 is trapped to EL2, unless implemented as RAZ, when it is IMPLEMENTATION DEFINED whether accesses to ID_ISAR6 are trapped to EL2, reported using EC syndrome value 0x03.

• In AArch32 state, ID_DFR1 is trapped to EL2, unless implemented as RAZ, when it is IMPLEMENTATION DEFINED whether accesses to ID_DFR1 are trapped to EL2, reported using EC syndrome value 0x03.

• In AArch32 state, it is IMPLEMENTATION DEFINED whether this bit traps MRC accesses to encodings that are not already mentioned, with coproc==p15, opc1 == 0, CRn == c0, CRm == {c2-c7}, opc2 == {0-7}.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

TID2, bit [17]

Trap ID group 2. Traps the following register accesses to EL2, when EL2 is enabled in the current Security state, as follows:

• If EL1 is using AArch64, reads of CTR_EL0, CCSIDR_EL1, CCSIDR2_EL1, CLIDR_EL1, and CSSELR_EL1 are trapped to EL2, reported using EC syndrome value 0x18.
• If EL0 is using AArch64 and the value of SCTLR_EL1.UCT is not 0, reads of CTR_EL0 are trapped to EL2, reported using EC syndrome value 0x18. If the value of SCTLR_EL1.UCT is 0 then EL0 reads of CTR_EL0 are UNDEFINED and any resulting exception takes precedence over this trap.
• If EL1 is using AArch64, writes to CSSELR_EL1 are trapped to EL2, reported using EC syndrome value 0x18.
• If EL1 is using AArch32, reads of CTR, CCSIDR, CCSIDR2, CLIDR, and CSSELR are trapped to EL2, reported using EC syndrome value 0x03.
• If EL1 is using AArch32, writes to CSSELR are trapped to EL2, reported using EC syndrome value 0x03.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

TID1, bit [16]

Trap ID group 1. Traps EL1 reads of the following registers to EL2, when EL2 is enabled in the current Security state as follows:

• In AArch64 state, accesses of REVIDR_EL1, AIDR_EL1, reported using EC syndrome value 0x18.

• In AArch32 state, accesses of TCMTR, TLBTR, REVIDR, AIDR, reported using EC syndrome value 0x03.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

TID0, bit [15]

Trap ID group 0. Traps the following register accesses to EL2:

• EL1 reads of the JIDR, reported using EC syndrome value 0x05.
• If the JIDR is RAZ from EL0, EL0 reads of the JIDR, reported using EC syndrome value 0x05.
• EL1 accesses using VMRS of the FPSID, reported using EC syndrome value 0x08.

In an AArch64 only implementation, this bit is RES0.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

TWE, bit [14]

Traps EL0 and EL1 execution of WFE instructions to EL2, when EL2 is enabled in the current Security state, from both Execution states, reported using EC syndrome value 0x01.

In AArch32 state, the attempted execution of a conditional WFE instruction is only trapped if the instruction passes its condition code check.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

For more information about when WFE instructions can cause the PE to enter a low-power state, see 'Wait for Event mechanism and Send event' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile.

This field resets to an architecturally UNKNOWN value.

TWI, bit [13]

Traps EL0 and EL1 execution of WFI instructions to EL2, when EL2 is enabled in the current Security state, from both Execution states, reported using EC syndrome value 0x01.

In AArch32 state, the attempted execution of a conditional WFI instruction is only trapped if the instruction passes its condition code check.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

For more information about when WFI instructions can cause the PE to enter a low-power state, see 'Wait for Interrupt' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile.

This field resets to an architecturally UNKNOWN value.

DC, bit [12]

Default Cacheability.

This field has no effect on the EL2, EL2&0, and EL3 translation regimes.

This field is permitted to be cached in a TLB.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this field.

This field resets to an architecturally UNKNOWN value.

BSU, bits [11:10]

Barrier Shareability upgrade. This field determines the minimum shareability domain that is applied to any barrier instruction executed from EL1 or EL0:

This value is combined with the specified level of the barrier held in its instruction, using the same principles as combining the shareability attributes from two stages of address translation.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0b00 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

FB, bit [9]

Force broadcast. Causes the following instructions to be broadcast within the Inner Shareable domain when executed from EL1:

AArch32: BPIALL, TLBIALL, TLBIMVA, TLBIASID, DTLBIALL, DTLBIMVA, DTLBIASID, ITLBIALL, ITLBIMVA, ITLBIASID, TLBIMVAA, ICIALLU, TLBIMVAL, TLBIMVAAL.

AArch64: TLBI VMALLE1, TLBI VAE1, TLBI ASIDE1, TLBI VAAE1, TLBI VALE1, TLBI VAALE1, IC IALLU, TLBI RVAE1, TLBI RVAAE1, TLBI RVALE1, TLBI RVAALE1.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

VSE, bit [8]

Virtual SError interrupt.

The virtual SError interrupt is only enabled when the value of HCR_EL2.{TGE, AMO} is {0, 1}.

This field resets to an architecturally UNKNOWN value.

VI, bit [7]

Virtual IRQ Interrupt.

The virtual IRQ is enabled only when the value of HCR_EL2.{TGE, IMO} is {0, 1}.

This field resets to an architecturally UNKNOWN value.

VF, bit [6]

Virtual FIQ Interrupt.

The virtual FIQ is enabled only when the value of HCR_EL2.{TGE, FMO} is {0, 1}.

This field resets to an architecturally UNKNOWN value.

AMO, bit [5]

Physical SError interrupt routing.

If EL2 is enabled in the current Security state and the value of HCR_EL2.TGE is 1:

• Regardless of the value of the AMO bit physical asynchronous External aborts and SError interrupts target EL2 unless they are routed to EL3.
• When ARMv8.1-VHE is not implemented, or if HCR_EL2.E2H is 0, this field behaves as 1 for all purposes other than a direct read of the value of this bit.
• When ARMv8.1-VHE is implemented and HCR_EL2.E2H is 1, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

For more information, see 'Asynchronous exception routing' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile, section D1 (The AArch64 System Level Programmers' Model).

This field resets to an architecturally UNKNOWN value.

IMO, bit [4]

Physical IRQ Routing.

If EL2 is enabled in the current Security state, and the value of HCR_EL2.TGE is 1:

• Regardless of the value of the IMO bit, physical IRQ Interrupts target EL2 unless they are routed to EL3.
• When ARMv8.1-VHE is not implemented, or if HCR_EL2.E2H is 0, this field behaves as 1 for all purposes other than a direct read of the value of this bit.
• When ARMv8.1-VHE is implemented and HCR_EL2.E2H is 1, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

For more information, see 'Asynchronous exception routing' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile, section D1.

This field resets to an architecturally UNKNOWN value.

FMO, bit [3]

Physical FIQ Routing.

If EL2 is enabled in the current Security state and the value of HCR_EL2.TGE is 1:

• Regardless of the value of the FMO bit, physical FIQ Interrupts target EL2 unless they are routed to EL3.
• When ARMv8.1-VHE is not implemented, or if HCR_EL2.E2H is 0, this field behaves as 1 for all purposes other than a direct read of the value of this bit.
• When ARMv8.1-VHE is implemented and HCR_EL2.E2H is 1, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

For more information, see 'Asynchronous exception routing' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile, section D1.

This field resets to an architecturally UNKNOWN value.

PTW, bit [2]

Protected Table Walk. In the EL1&0 translation regime, a translation table access made as part of a stage 1 translation table walk is subject to a stage 2 translation. The combining of the memory type attributes from the two stages of translation means the access might be made to a type of Device memory. If this occurs, then the value of this bit determines the behavior:

This field is permitted to be cached in a TLB.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

SWIO, bit [1]

Set/Way Invalidation Override. Causes EL1 execution of the data cache invalidate by set/way instructions to perform a data cache clean and invalidate by set/way:

When the value of this bit is 1:

AArch32: DCISW performs the same invalidation as a DCCISW instruction.

AArch64: DC ISW performs the same invalidation as a DC CISW instruction.

This bit can be implemented as RES1.

When HCR_EL2.TGE is 1, the PE ignores the value of this field for all purposes other than a direct read of this field.

This field resets to an architecturally UNKNOWN value.

VM, bit [0]

Virtualization enable. Enables stage 2 address translation for the EL1&0 translation regime, when EL2 is enabled in the current Security state.

When the value of this bit is 1, data cache invalidate instructions executed at EL1 perform a data cache clean and invalidate. For the invalidate by set/way instruction this behavior applies regardless of the value of the HCR_EL2.SWIO bit.

This bit is permitted to be cached in a TLB.

When ARMv8.1-VHE is implemented, and the value of HCR_EL2.{E2H, TGE} is {1, 1}, this field behaves as 0 for all purposes other than a direct read of the value of this bit.

This field resets to an architecturally UNKNOWN value.

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then
        return NVMem[0x078];
    elsif EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    return HCR_EL2;
elsif PSTATE.EL == EL3 then
    return HCR_EL2;
              

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then
        NVMem[0x078] = X[t];
    elsif EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    HCR_EL2 = X[t];
elsif PSTATE.EL == EL3 then
    HCR_EL2 = X[t];