TTBR0_EL1 | Jon's Arm Reference

Holds the base address of the translation table for the initial lookup for stage 1 of the translation of an address from the lower VA range in the EL1&0 translation regime, and other information for this translation regime.

Configuration

AArch64 System register TTBR0_EL1 bits [63:0] are architecturally mapped to AArch32 System register TTBR0[63:0].

TTBR0_EL1 is a 128-bit register that can also be accessed as a 64-bit value. If it is accessed as a 64-bit register, accesses read and write bits [63:0] and do not modify bits [127:64].

Attributes

Field descriptions

When FEAT_D128 is implemented and TCR2_EL1.D128 == 1:

Bits [127:88]

BADDR, bits [87:80, 47:5]

Bits [79:64]

ASID, bits [63:48]

Bits [4:3]

SKL, bits [2:1]

SKL	Meaning
0b00	Skip 0 level from the regular start level.
0b01	Skip 1 level from the regular start level.
0b10	Skip 2 levels from the regular start level.
0b11	Skip 3 levels from the regular start level.

CnP, bit [0]

When FEAT_TTCNP is implemented:

Common not Private. This bit indicates whether each entry that is pointed to by TTBR0_EL1 is a member of a common set that can be used by every PE in the Inner Shareable domain for which the value of TTBR0_EL1.CnP is 1.

CnP	Meaning
0b0	The translation table entries pointed to by TTBR0_EL1, for the current translation regime and ASID, are permitted to differ from corresponding entries for TTBR0_EL1 for other PEs in the Inner Shareable domain. This is not affected by: The value of TTBR0_EL1.CnP on those other PEs. The value of the current ASID. If EL2 is implemented and enabled in the current Security state, the value of the current VMID.
0b1	The translation table entries pointed to by TTBR0_EL1 are the same as the translation table entries for every other PE in the Inner Shareable domain for which the value of TTBR0_EL1.CnP is 1 and all of the following apply: The translation table entries are pointed to by TTBR0_EL1. The translation tables relate to the same translation regime. The ASID is the same as the current ASID. If EL2 is implemented and enabled in the current Security state, the value of the current VMID.

CnP

Meaning

0b0

The translation table entries pointed to by TTBR0_EL1, for the current translation regime and ASID, are permitted to differ from corresponding entries for TTBR0_EL1 for other PEs in the Inner Shareable domain. This is not affected by:

The value of TTBR0_EL1.CnP on those other PEs.
The value of the current ASID.
If EL2 is implemented and enabled in the current Security state, the value of the current VMID.

0b1

The translation table entries pointed to by TTBR0_EL1 are the same as the translation table entries for every other PE in the Inner Shareable domain for which the value of TTBR0_EL1.CnP is 1 and all of the following apply:

The translation table entries are pointed to by TTBR0_EL1.
The translation tables relate to the same translation regime.
The ASID is the same as the current ASID.
If EL2 is implemented and enabled in the current Security state, the value of the current VMID.

This bit is permitted to be cached in a TLB.

When a TLB combines entries from stage 1 translation and stage 2 translation into a single entry, that entry can only be shared between different PEs if the value of the CnP bit is 1 for both stage 1 and stage 2.

Note

If the value of the TTBR0_EL1.CnP bit is 1 on multiple PEs in the same Inner Shareable domain and those TTBR0_EL1s do not point to the same translation table entries when the other conditions specified for the case when the value of CnP is 1 apply, then the results of translations are CONSTRAINED UNPREDICTABLE, see 'CONSTRAINED UNPREDICTABLE behaviors due to caching of control or data values'.

The reset behavior of this field is:

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

Otherwise:

When FEAT_D128 is not implemented or TCR2_EL1.D128 == 0:

ASID, bits [63:48]

BADDR[47:1], bits [47:1]

Translation table base address:

Bits A[47:x] of the stage 1 translation table base address bits are in register bits[47:x].
Bits A[(x-1):0] of the stage 1 translation table base address are zero.

Address bit x is the minimum address bit required to align the translation table to the size of the table. The AArch64 Virtual Memory System Architecture chapter describes how x is calculated based on the value of TCR_EL1.T0SZ, the translation stage, and the translation granule size.

Note

If an OA size of more than 48 bits is in use, and the translation table has fewer than eight entries, the table must be aligned to 64 bytes. Otherwise the translation table must be aligned to the size of the table.

If the value of TCR_EL1.IPS is not 0b110, then:

Register bits[(x-1):1] are RES0.
If the implementation supports 52-bit PAs and IPAs, then bits A[51:48] of the stage 1 translation table base address are 0b0000.

If FEAT_LPA is implemented and the value of TCR_EL1.IPS is 0b110, then:

Bits A[51:48] of the stage 1 translation table base address bits are in register bits[5:2].
Register bit[1] is RES0.
The smallest permitted value of x is 6.
When x>6, register bits[(x-1):6] are RES0.

Note

TCR_EL1.IPS==0b110 is permitted when:

FEAT_LPA is implemented and the 64KB translation granule is used.
FEAT_LPA2 is implemented and the 4KB or 16KB translation granule is used.

When the value of ID_AA64MMFR0_EL1.PARange indicates that the implementation does not support a 52 bit PA size, if a translation table lookup uses this register when the Effective value of TCR_EL1.IPS is 0b110 and the value of register bits[5:2] is nonzero, an Address size fault is generated.

When the value of ID_AA64MMFR0_EL1.PARange indicates that the implementation supports a 56 bit PA size, bits A[55:52] of the stage 1 translation table base address are zero.

If any register bit[47:1] that is defined as RES0 has the value 1 when a translation table walk is done using TTBR0_EL1, then the translation table base address might be misaligned, with effects that are CONSTRAINED UNPREDICTABLE, and must be one of the following:

Bits A[(x-1):0] of the stage 1 translation table base address are treated as if all the bits are zero. The value read back from the corresponding register bits is either the value written to the register or zero.
The result of the calculation of an address for a translation table walk using this register can be corrupted in those bits that are nonzero.

The reset behavior of this field is:

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

CnP, bit [0]

When FEAT_TTCNP is implemented:

CnP	Meaning
0b0	The translation table entries pointed to by TTBR0_EL1, for the current translation regime and ASID, are permitted to differ from corresponding entries for TTBR0_EL1 for other PEs in the Inner Shareable domain. This is not affected by: The value of TTBR0_EL1.CnP on those other PEs. The value of the current ASID. If EL2 is implemented and enabled in the current Security state, the value of the current VMID.
0b1	The translation table entries pointed to by TTBR0_EL1 are the same as the translation table entries for every other PE in the Inner Shareable domain for which the value of TTBR0_EL1.CnP is 1 and all of the following apply: The translation table entries are pointed to by TTBR0_EL1. The translation tables relate to the same translation regime. The ASID is the same as the current ASID. If EL2 is implemented and enabled in the current Security state, the value of the current VMID.

CnP

Meaning

0b0

The value of TTBR0_EL1.CnP on those other PEs.
The value of the current ASID.
If EL2 is implemented and enabled in the current Security state, the value of the current VMID.

0b1

The translation table entries are pointed to by TTBR0_EL1.
The translation tables relate to the same translation regime.
The ASID is the same as the current ASID.
If EL2 is implemented and enabled in the current Security state, the value of the current VMID.

This bit is permitted to be cached in a TLB.

Note

The reset behavior of this field is:

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

Otherwise:

Accessing TTBR0_EL1

When the Effective value of HCR_EL2.E2H is 1, without explicit synchronization, access from EL3 using the mnemonic TTBR0_EL1 or TTBR0_EL12 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>, TTBR0_EL1

op0	op1	CRn	CRm	op2
0b11	0b000	0b0010	0b0000	0b000

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.TTBR0_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() == '111' then X[t, 64] = NVMem[0x200]; else X[t, 64] = TTBR0_EL1<63:0>; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then X[t, 64] = TTBR0_EL2<63:0>; else X[t, 64] = TTBR0_EL1<63:0>; elsif PSTATE.EL == EL3 then X[t, 64] = TTBR0_EL1<63:0>;

MSR TTBR0_EL1, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b000	0b0010	0b0000	0b000

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.TTBR0_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() == '111' then NVMem[0x200] = X[t, 64]; else TTBR0_EL1<63:0> = X[t, 64]; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then TTBR0_EL2<63:0> = X[t, 64]; else TTBR0_EL1<63:0> = X[t, 64]; elsif PSTATE.EL == EL3 then TTBR0_EL1<63:0> = X[t, 64];

MRS <Xt>, TTBR0_EL12

op0	op1	CRn	CRm	op2
0b11	0b101	0b0010	0b0000	0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then X[t, 64] = NVMem[0x200]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then X[t, 64] = TTBR0_EL1<63:0>; else UNDEFINED; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then X[t, 64] = TTBR0_EL1<63:0>; else UNDEFINED;

MSR TTBR0_EL12, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b101	0b0010	0b0000	0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then NVMem[0x200] = X[t, 64]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then TTBR0_EL1<63:0> = X[t, 64]; else UNDEFINED; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then TTBR0_EL1<63:0> = X[t, 64]; else UNDEFINED;

When FEAT_D128 is implemented

MRRS <Xt+1>, <Xt>, TTBR0_EL1

op0	op1	CRn	CRm	op2
0b11	0b000	0b0010	0b0000	0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.D128En == '0' then UNDEFINED; elsif EL2Enabled() && HCR_EL2.TRVM == '1' then AArch64.SystemAccessTrap(EL2, 0x14); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGRTR_EL2.TTBR0_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x14); elsif EL2Enabled() && (!IsHCRXEL2Enabled() || HCRX_EL2.D128En == '0') then AArch64.SystemAccessTrap(EL2, 0x14); elsif HaveEL(EL3) && SCR_EL3.D128En == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x14); elsif EffectiveHCR_EL2_NVx() == '111' then (X[t + 1, 64], X[t, 64]) = Split(NVMem[0x200, 128], 64); else (X[t + 1, 64], X[t, 64]) = Split(TTBR0_EL1, 64); elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.D128En == '0' then UNDEFINED; elsif HaveEL(EL3) && SCR_EL3.D128En == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x14); elsif ELIsInHost(EL2) then (X[t + 1, 64], X[t, 64]) = Split(TTBR0_EL2, 64); else (X[t + 1, 64], X[t, 64]) = Split(TTBR0_EL1, 64); elsif PSTATE.EL == EL3 then (X[t + 1, 64], X[t, 64]) = Split(TTBR0_EL1, 64);

When FEAT_D128 is implemented

MSRR TTBR0_EL1, <Xt+1>, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b000	0b0010	0b0000	0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.D128En == '0' then UNDEFINED; elsif EL2Enabled() && HCR_EL2.TVM == '1' then AArch64.SystemAccessTrap(EL2, 0x14); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGWTR_EL2.TTBR0_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x14); elsif EL2Enabled() && (!IsHCRXEL2Enabled() || HCRX_EL2.D128En == '0') then AArch64.SystemAccessTrap(EL2, 0x14); elsif HaveEL(EL3) && SCR_EL3.D128En == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x14); elsif EffectiveHCR_EL2_NVx() == '111' then NVMem[0x200, 128] = X[t + 1, 64]:X[t, 64]; else TTBR0_EL1<127:0> = X[t + 1, 64]:X[t, 64]; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.D128En == '0' then UNDEFINED; elsif HaveEL(EL3) && SCR_EL3.D128En == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x14); elsif ELIsInHost(EL2) then TTBR0_EL2<127:0> = X[t + 1, 64]:X[t, 64]; else TTBR0_EL1<127:0> = X[t + 1, 64]:X[t, 64]; elsif PSTATE.EL == EL3 then TTBR0_EL1<127:0> = X[t + 1, 64]:X[t, 64];

When FEAT_D128 is implemented

MRRS <Xt+1>, <Xt>, TTBR0_EL12

op0	op1	CRn	CRm	op2
0b11	0b101	0b0010	0b0000	0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then (X[t + 1, 64], X[t, 64]) = Split(NVMem[0x200, 128], 64); elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x14); else UNDEFINED; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.D128En == '0' then UNDEFINED; elsif HaveEL(EL3) && SCR_EL3.D128En == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x14); else (X[t + 1, 64], X[t, 64]) = Split(TTBR0_EL1, 64); else UNDEFINED; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then (X[t + 1, 64], X[t, 64]) = Split(TTBR0_EL1, 64); else UNDEFINED;

When FEAT_D128 is implemented

MSRR TTBR0_EL12, <Xt+1>, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b101	0b0010	0b0000	0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then NVMem[0x200, 128] = X[t + 1, 64]:X[t, 64]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x14); else UNDEFINED; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.D128En == '0' then UNDEFINED; elsif HaveEL(EL3) && SCR_EL3.D128En == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x14); else TTBR0_EL1<127:0> = X[t + 1, 64]:X[t, 64]; else UNDEFINED; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then TTBR0_EL1<127:0> = X[t + 1, 64]:X[t, 64]; else UNDEFINED;

127	126	125	124	123	122	121	120	119	118	117	116	115	114	113	112	111	110	109	108	107	106	105	104	103	102	101	100	99	98	97	96
RES0
95	94	93	92	91	90	89	88	87	86	85	84	83	82	81	80	79	78	77	76	75	74	73	72	71	70	69	68	67	66	65	64
RES0								BADDR[50:43]								RES0
63	62	61	60	59	58	57	56	55	54	53	52	51	50	49	48	47	46	45	44	43	42	41	40	39	38	37	36	35	34	33	32
ASID																BADDR[42:0]
31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
BADDR[42:0]																											RES0		SKL		CnP

63	62	61	60	59	58	57	56	55	54	53	52	51	50	49	48	47	46	45	44	43	42	41	40	39	38	37	36	35	34	33	32
31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ASID																BADDR[47:1]
BADDR[47:1]																															CnP

TTBR0_EL1: Translation Table Base Register 0 (EL1)

Purpose

Configuration

Attributes

Field descriptions

When FEAT_D128 is implemented and TCR2_EL1.D128 == 1:

Bits [127:88]

BADDR, bits [87:80, 47:5]

Bits [79:64]

ASID, bits [63:48]

Bits [4:3]

SKL, bits [2:1]

CnP, bit [0]

When FEAT_TTCNP is implemented:

Otherwise:

When FEAT_D128 is not implemented or TCR2_EL1.D128 == 0:

ASID, bits [63:48]

BADDR[47:1], bits [47:1]

CnP, bit [0]

When FEAT_TTCNP is implemented:

Otherwise:

Accessing TTBR0_EL1

TTBR0_EL1: Translation Table Base Register 0 (EL1)

Purpose

Configuration

Attributes

Field descriptions

When FEAT_D128 is implemented and TCR2_EL1.D128 == 1:

Bits [127:88]

BADDR, bits [87:80, 47:5]

Bits [79:64]

ASID, bits [63:48]

Bits [4:3]

SKL, bits [2:1]

CnP, bit [0]When FEAT_TTCNP is implemented:

Otherwise:

When FEAT_D128 is not implemented or TCR2_EL1.D128 == 0:

ASID, bits [63:48]

BADDR[47:1], bits [47:1]

CnP, bit [0]When FEAT_TTCNP is implemented:

Otherwise:

Accessing TTBR0_EL1

CnP, bit [0]

When FEAT_TTCNP is implemented:

CnP, bit [0]

When FEAT_TTCNP is implemented: