The TTBR0_EL3 characteristics are:
Holds the base address of the translation table for the initial lookup for stage 1 of an address translation in the EL3 translation regime, and other information for this translation regime.
This register is present only when EL3 is implemented. Otherwise, direct accesses to TTBR0_EL3 are UNDEFINED.
TTBR0_EL3 is a 64-bit register.
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 |
RES0 | BADDR | ||||||||||||||||||||||||||||||
BADDR | RES0 | SKL | CnP |
Reserved, RES0.
Address bit x is the minimum address bit required to align the translation table to the size of the table. x is calculated based on LOG2(StartTableSize), as described in VMSAv9-128. The smallest permitted value of x is 5.
The reset behavior of this field is:
Reserved, RES0.
Skip Level associated with translation table walks using TTBR0_EL3.
This determines the number of levels to be skipped from the regular start level of the Stage 1 EL3 translation table walks using TTBR0_EL3.
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. |
The reset behavior of this field is:
Common not Private, for stage 2 of the Secure EL1&0 translation regime. In an implementation that includes FEAT_TTCNP, indicates whether each entry that is pointed to by VSTTBR_EL2 is a member of a common set that can be used by every PE in the Inner Shareable domain for which the value of VSTTBR_EL2.CnP is 1.
CnP | Meaning |
---|---|
0b0 |
The translation table entries pointed to by VSTTBR_EL2 are permitted to differ from the entries for VSTTBR_EL2 for other PEs in the Inner Shareable domain. This is not affected by the value of the current VMID. |
0b1 |
The translation table entries pointed to by VSTTBR_EL2 are the same as the translation table entries for every other PE in the Inner Shareable domain for which the value of VSTTBR_EL2.CnP is 1 and the VMID is the same as the current VMID. |
This bit is permitted to be cached in a TLB.
If the value of VSTTBR_EL2.CnP bit is 1 on multiple PEs in the same Inner Shareable domain and those VSTTBR_EL2s do not point to the same translation table entries when using the current VMID, then the results of translations using VSTTBR_EL2 are CONSTRAINED UNPREDICTABLE, see 'CONSTRAINED UNPREDICTABLE behaviors due to caching of control or data values'.
When this register has an architecturally-defined reset value, this field resets to a value that is architecturally UNKNOWN.
The reset behavior of this field is:
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 |
RES0 | BADDR | ||||||||||||||||||||||||||||||
BADDR | CnP |
Reserved, RES0.
Address bit x is the minimum address bit required to align the translation table to the size of the table. The smallest permitted value of x is 6. The AArch64 Virtual Memory System Architecture chapter describes how x is calculated based on the value of TCR_EL3.T0SZ, the translation stage, and the translation granule size.
A translation table is required to be aligned to the size of the table. If a table contains fewer than eight entries, it must be aligned on a 64 byte address boundary.
If the value of TCR_EL3.PS is not 0b110, then:
If FEAT_LPA is implemented and the value of TCR_EL3.PS is 0b110, then:
TCR_EL3.PS==0b110 is permitted when:
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_EL3.PS 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_EL3, then the translation table base address might be misaligned, with effects that are CONSTRAINED UNPREDICTABLE, and must be one of the following:
The reset behavior of this field is:
Common not Private. This bit indicates whether each entry that is pointed to by TTBR0_EL3 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_EL3.CnP is 1.
CnP | Meaning |
---|---|
0b0 |
The translation table entries pointed to by TTBR0_EL3, for the current translation regime, are permitted to differ from corresponding entries for TTBR0_EL3 for other PEs in the Inner Shareable domain. This is not affected by the value of TTBR0_EL3.CnP on those other PEs. |
0b1 |
The translation table entries pointed to by TTBR0_EL3 are the same as the translation table entries for every other PE in the Inner Shareable domain for which the value of TTBR0_EL3.CnP is 1 and the translation table entries are pointed to by TTBR0_EL3. |
This bit is permitted to be cached in a TLB.
If the value of the TTBR0_EL3.CnP bit is 1 on multiple PEs in the same Inner Shareable domain and those TTBR0_EL3s do not point to the same translation table entries the results of translations using TTBR0_EL3 are CONSTRAINED UNPREDICTABLE, see 'CONSTRAINED UNPREDICTABLE behaviors due to caching of control or data values'.
The reset behavior of this field is:
Reserved, RES0.
Accesses to this register use the following encodings in the System register encoding space:
op0 | op1 | CRn | CRm | op2 |
---|---|---|---|---|
0b11 | 0b110 | 0b0010 | 0b0000 | 0b000 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then X[t, 64] = TTBR0_EL3;
op0 | op1 | CRn | CRm | op2 |
---|---|---|---|---|
0b11 | 0b110 | 0b0010 | 0b0000 | 0b000 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then TTBR0_EL3 = X[t, 64];
30/09/2022 15:57; 21c5a6dd0fdaf10a712e2f2d6fffbdbd66d4d96f
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