CONTEXTIDR

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

Configuration

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

Attributes

Field descriptions

Bits [63:32]

PROCID, bits [31:0]

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

Note

In AArch32 state, when TTBCR.EAE is set to 0, CONTEXTIDR.ASID holds the ASID.

In AArch64 state, CONTEXTIDR_EL1 is independent of the ASID, and for the EL1&0 translation regime either TTBR0_EL1 or TTBR1_EL1 holds the ASID.

The reset behavior of this field is:

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

Accessing CONTEXTIDR_EL1

When the Effective value of HCR_EL2.E2H is 1, without explicit synchronization, accesses from EL3 using the accessor name CONTEXTIDR_EL1 or CONTEXTIDR_EL12 are not guaranteed to be ordered with respect to accesses using the other accessor name.

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

MRS <Xt>, CONTEXTIDR_EL1

op0	op1	CRn	CRm	op2
0b11	0b000	0b1101	0b0000	0b001

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.CONTEXTIDR_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() IN {'111'} then X[t, 64] = NVMem[0x108]; else X[t, 64] = CONTEXTIDR_EL1; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then X[t, 64] = CONTEXTIDR_EL2; else X[t, 64] = CONTEXTIDR_EL1; elsif PSTATE.EL == EL3 then X[t, 64] = CONTEXTIDR_EL1;

MSR CONTEXTIDR_EL1, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b000	0b1101	0b0000	0b001

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.CONTEXTIDR_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() IN {'111'} then NVMem[0x108] = X[t, 64]; else CONTEXTIDR_EL1 = X[t, 64]; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then CONTEXTIDR_EL2 = X[t, 64]; else CONTEXTIDR_EL1 = X[t, 64]; elsif PSTATE.EL == EL3 then CONTEXTIDR_EL1 = X[t, 64];

MRS <Xt>, CONTEXTIDR_EL12

op0	op1	CRn	CRm	op2
0b11	0b101	0b1101	0b0000	0b001

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then X[t, 64] = NVMem[0x108]; 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] = CONTEXTIDR_EL1; else UNDEFINED; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then X[t, 64] = CONTEXTIDR_EL1; else UNDEFINED;

MSR CONTEXTIDR_EL12, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b101	0b1101	0b0000	0b001

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then NVMem[0x108] = 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 CONTEXTIDR_EL1 = X[t, 64]; else UNDEFINED; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then CONTEXTIDR_EL1 = X[t, 64]; else UNDEFINED;

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
PROCID

CONTEXTIDR_EL1, Context ID Register (EL1)

Purpose