CONTEXTIDR_EL1 Context ID Register (EL1) when FEAT_AA64 is implemented CONTEXTIDR Architectural AArch32 31 0 31 0 31 0 31 0 Identifies the current Process Identifier. The value of the whole of this register is called the Context ID and is used by: The debug logic, for Linked and Unlinked Context ID matching. The trace logic, to identify the current process. The significance of this register is for debug and trace use only. Memory CONTEXTIDR_EL1 is a 64-bit register. 63 32 63:32 Reserved, RES0. PROCID 31 0 31:0 Process Identifier. This field must be programmed with a unique value that identifies the current process. 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. AU 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. MRS <Xt>, CONTEXTIDR_EL1 if !IsFeatureImplemented(FEAT_AA64) then Undefined(); elsif 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{64}(t) = NVMem(0x108); else X{64}(t) = CONTEXTIDR_EL1(); end; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then X{64}(t) = CONTEXTIDR_EL2(); else X{64}(t) = CONTEXTIDR_EL1(); end; elsif PSTATE.EL == EL3 then X{64}(t) = CONTEXTIDR_EL1(); end; MSR CONTEXTIDR_EL1, <Xt> if !IsFeatureImplemented(FEAT_AA64) then Undefined(); elsif 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{64}(t); else CONTEXTIDR_EL1() = X{64}(t); end; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then CONTEXTIDR_EL2() = X{64}(t); else CONTEXTIDR_EL1() = X{64}(t); end; elsif PSTATE.EL == EL3 then CONTEXTIDR_EL1() = X{64}(t); end; MRS <Xt>, CONTEXTIDR_EL12 When FEAT_VHE is implemented if !IsFeatureImplemented(FEAT_AA64) then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then X{64}(t) = NVMem(0x108); elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64_SystemAccessTrap(EL2, 0x18); else Undefined(); end; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then X{64}(t) = CONTEXTIDR_EL1(); else Undefined(); end; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then X{64}(t) = CONTEXTIDR_EL1(); else Undefined(); end; end; MSR CONTEXTIDR_EL12, <Xt> When FEAT_VHE is implemented if !IsFeatureImplemented(FEAT_AA64) then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then NVMem(0x108) = X{64}(t); elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64_SystemAccessTrap(EL2, 0x18); else Undefined(); end; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then CONTEXTIDR_EL1() = X{64}(t); else Undefined(); end; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then CONTEXTIDR_EL1() = X{64}(t); else Undefined(); end; end; 2026-03-26 20:27:25 2026-03_rel