TTBR0_EL3, Translation Table Base Register 0 (EL3)

The TTBR0_EL3 characteristics are:

Purpose

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.

Configuration

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

TTBR0_EL3 is a 64-bit register.

Field descriptions

The TTBR0_EL3 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RES0BADDR
BADDRCnP
313029282726252423222120191817161514131211109876543210

Bits [63:48]

Reserved, RES0.

BADDR, bits [47:1]

Translation table base address, A[47:x] or A[51:x].

Note

In an implementation that includes ARMv8.2-LPA, if the value of TCR_EL3.PS is 0b110 then:

Note

If the Effective value of TCR_EL3.PS is not 0b110 then:

Note

This definition applies:

If any TTBR0_EL3[47:0] bit that is defined as RES0 has the value 1 when a translation table walk is performed 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 AArch64 Virtual Memory System Architecture chapter describes how x is calculated based on the value of TCR_EL3.T0SZ, the stage of translation, and the translation granule size.

This field resets to an architecturally UNKNOWN value.

CnP, bit [0]

When ARMv8.2-TTCNP is implemented:

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.

CnPMeaning
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 field is permitted to be cached in a TLB.

Note

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' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile.

This field resets to an architecturally UNKNOWN value.


Otherwise:

Reserved, RES0.

Accessing the TTBR0_EL3

Accesses to this register use the following encodings:

MRS <Xt>, TTBR0_EL3

op0op1CRnCRmop2
0b110b1100b00100b00000b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then return TTBR0_EL3;

MSR TTBR0_EL3, <Xt>

op0op1CRnCRmop2
0b110b1100b00100b00000b000

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];




27/03/2019 21:59; e5e4db499bf9867a4b93324c4dbac985d3da9376

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