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CONTEXTIDR: Context ID Register

Purpose

Identifies the current Process Identifier and, when using the Short-descriptor translation table format, the Address Space Identifier.

The value of the whole of this register is called the Context ID and is used by:

The significance of this register is for debug and trace use only.

Configuration

This register is banked between CONTEXTIDR and CONTEXTIDR_S and CONTEXTIDR_NS.

AArch32 System register CONTEXTIDR bits [31:0] are architecturally mapped to AArch64 System register CONTEXTIDR_EL1[31:0].

This register is present only when EL1 is capable of using AArch32. Otherwise, direct accesses to CONTEXTIDR are UNDEFINED.

The register format depends on whether address translation is using the Long-descriptor or the Short-descriptor translation table format.

Attributes

CONTEXTIDR is a 32-bit register.

This register has the following instances:

Field descriptions

When TTBCR.EAE == 0:

313029282726252423222120191817161514131211109876543210
PROCIDASID

PROCID, bits [31:8]

Process Identifier. This field must be programmed with a unique value that identifies the current process.

The reset behavior of this field is:

ASID, bits [7:0]

Address Space Identifier. This field is programmed with the value of the current ASID.

The reset behavior of this field is:

When TTBCR.EAE == 1:

313029282726252423222120191817161514131211109876543210
PROCID

PROCID, bits [31:0]

Process Identifier. This field must be programmed with a unique value that identifies the current process.

The reset behavior of this field is:

Accessing CONTEXTIDR

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

MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coprocopc1CRnCRmopc2
0b11110b0000b11010b00000b001

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T13 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T13 == '1' then AArch32.TakeHypTrapException(0x03); elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TRVM == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TRVM == '1' then AArch32.TakeHypTrapException(0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) then R[t] = CONTEXTIDR_NS; else R[t] = CONTEXTIDR; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && ELUsingAArch32(EL3) then R[t] = CONTEXTIDR_NS; else R[t] = CONTEXTIDR; elsif PSTATE.EL == EL3 then if SCR.NS == '0' then R[t] = CONTEXTIDR_S; else R[t] = CONTEXTIDR_NS;

MCR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coprocopc1CRnCRmopc2
0b11110b0000b11010b00000b001

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T13 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T13 == '1' then AArch32.TakeHypTrapException(0x03); elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TVM == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TVM == '1' then AArch32.TakeHypTrapException(0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) then CONTEXTIDR_NS = R[t]; else CONTEXTIDR = R[t]; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && ELUsingAArch32(EL3) then CONTEXTIDR_NS = R[t]; else CONTEXTIDR = R[t]; elsif PSTATE.EL == EL3 then if SCR.NS == '0' then CONTEXTIDR_S = R[t]; else CONTEXTIDR_NS = R[t];