MSR (immediate) Move immediate value to special register This instruction moves an immediate value to selected bits of the PSTATE. For more information, see Process state, PSTATE. The bits that can be written by this instruction are: PSTATE.D, PSTATE.A, PSTATE.I, PSTATE.F, and PSTATE.SP. If FEAT_SSBS is implemented, PSTATE.SSBS. If FEAT_PAN is implemented, PSTATE.PAN. If FEAT_UAO is implemented, PSTATE.UAO. If FEAT_DIT is implemented, PSTATE.DIT. If FEAT_MTE is implemented, PSTATE.TCO. If FEAT_NMI is implemented, PSTATE.ALLINT. If FEAT_SME is implemented, PSTATE.SM and PSTATE.ZA. If FEAT_EBEP is implemented, PSTATE.PM. If FEAT_MTE is implemented and FEAT_MTE2 is not implemented, it is IMPLEMENTATION DEFINED whether writes to PSTATE.TCO by this instruction are ignored. This instruction is used by the aliases SMSTART op1 == '011' && CRm IN {'0xx1'} && op2 == '011' SMSTOP op1 == '011' && CRm IN {'0xx0'} && op2 == '011' See below for details of when each alias is preferred. 1 1 0 1 0 1 0 1 0 0 0 0 0 0 1 0 0 1 1 1 1 1 MSR <pstatefield>, #<imm> if op1 == '000' && op2 == '000' then See("CFINV"); end; if op1 == '000' && op2 == '001' then See("XAFLAG"); end; if op1 == '000' && op2 == '010' then See("AXFLAG"); end; var min_EL : bits(2); var need_secure : boolean = FALSE; case op1 of when '00x' => min_EL = EL1; when '010' => min_EL = EL1; when '011' => min_EL = EL0; when '100' => min_EL = EL2; when '101' => if !IsFeatureImplemented(FEAT_VHE) then EndOfDecode(Decode_UNDEF); end; min_EL = EL2; when '110' => min_EL = EL3; when '111' => min_EL = EL1; need_secure = TRUE; end; let operand : bits(4) = CRm; var field : PSTATEField; case op1::op2 of when '000 011' => if !IsFeatureImplemented(FEAT_UAO) then EndOfDecode(Decode_UNDEF); end; field = PSTATEField_UAO; when '000 100' => if !IsFeatureImplemented(FEAT_PAN) then EndOfDecode(Decode_UNDEF); end; field = PSTATEField_PAN; when '000 101' => field = PSTATEField_SP; when '001 000' => case CRm of when '000x' => if !IsFeatureImplemented(FEAT_NMI) then EndOfDecode(Decode_UNDEF); end; field = PSTATEField_ALLINT; when '001x' => if !IsFeatureImplemented(FEAT_EBEP) then EndOfDecode(Decode_UNDEF); end; field = PSTATEField_PM; otherwise => EndOfDecode(Decode_UNDEF); end; when '011 010' => if !IsFeatureImplemented(FEAT_DIT) then EndOfDecode(Decode_UNDEF); end; field = PSTATEField_DIT; when '011 011' => case CRm of when '001x' => if !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); end; field = PSTATEField_SVCRSM; when '010x' => if !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); end; field = PSTATEField_SVCRZA; when '011x' => if !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); end; field = PSTATEField_SVCRSMZA; otherwise => EndOfDecode(Decode_UNDEF); end; when '011 100' => if !IsFeatureImplemented(FEAT_MTE) then EndOfDecode(Decode_UNDEF); end; field = PSTATEField_TCO; when '011 110' => field = PSTATEField_DAIFSet; when '011 111' => field = PSTATEField_DAIFClr; when '011 001' => if !IsFeatureImplemented(FEAT_SSBS) then EndOfDecode(Decode_UNDEF); end; field = PSTATEField_SSBS; otherwise => EndOfDecode(Decode_UNDEF); end; <pstatefield> Is a PSTATE field name. For the MSR instruction, this is CRm op1 op2 <pstatefield> Architectural Feature xxxx 000 011 UAO xxxx 000 100 PAN xxxx 000 101 SPSel xxxx 000 11x RESERVED 000x 001 000 ALLINT xxxx 001 001 RESERVED xxxx 001 01x RESERVED xxxx 001 1xx RESERVED xxxx 010 xxx RESERVED xxxx 011 000 RESERVED xxxx 011 001 SSBS xxxx 011 010 DIT 000x 011 011 RESERVED xxxx 011 100 TCO xxxx 011 101 RESERVED xxxx 011 110 DAIFSet xxxx 011 111 DAIFClr xxxx 1xx xxx RESERVED 001x 001 000 PM 001x 011 011 SVCRSM 01xx 001 000 RESERVED 010x 011 011 SVCRZA 011x 011 011 SVCRSMZA 1xxx 001 000 RESERVED 1xxx 011 011 RESERVED For the SMSTART and SMSTOP aliases, this is encoded in "CRm<2:1>", where 0b01 specifies SVCRSM, 0b10 specifies SVCRZA, and 0b11 specifies SVCRSMZA. <imm> Is a 4-bit unsigned immediate, in the range 0 to 15, encoded in the "CRm" field. Restricted to the range 0 to 1, encoded in "CRm<0>", when <pstatefield> is ALLINT, PM, SVCRSM, SVCRSMZA, or SVCRZA. Alias Conditions if UInt(PSTATE.EL) < UInt(min_EL) then Undefined(); end; if need_secure && CurrentSecurityState() != SS_Secure then Undefined(); end; case field of when PSTATEField_SSBS => PSTATE.SSBS = operand[0]; when PSTATEField_SP => PSTATE.SP = operand[0]; when PSTATEField_DAIFSet => AArch64_CheckDAIFAccess(PSTATEField_DAIFSet); PSTATE.D = PSTATE.D OR operand[3]; PSTATE.A = PSTATE.A OR operand[2]; PSTATE.I = PSTATE.I OR operand[1]; PSTATE.F = PSTATE.F OR operand[0]; when PSTATEField_DAIFClr => AArch64_CheckDAIFAccess(PSTATEField_DAIFClr); PSTATE.D = PSTATE.D AND NOT(operand[3]); PSTATE.A = PSTATE.A AND NOT(operand[2]); PSTATE.I = PSTATE.I AND NOT(operand[1]); PSTATE.F = PSTATE.F AND NOT(operand[0]); when PSTATEField_PAN => PSTATE.PAN = operand[0]; when PSTATEField_UAO => PSTATE.UAO = operand[0]; when PSTATEField_DIT => PSTATE.DIT = operand[0]; when PSTATEField_TCO => PSTATE.TCO = operand[0]; when PSTATEField_ALLINT => if (PSTATE.EL == EL1 && IsHCRXEL2Enabled() && HCRX_EL2().TALLINT == '1' && operand[0] == '1') then AArch64_SystemAccessTrap(EL2, 0x18); end; PSTATE.ALLINT = operand[0]; when PSTATEField_SVCRSM => CheckSMEAccess(); SetPSTATE_SM(operand[0]); when PSTATEField_SVCRZA => CheckSMEAccess(); SetPSTATE_ZA(operand[0]); when PSTATEField_SVCRSMZA => CheckSMEAccess(); SetPSTATE_SM(operand[0]); SetPSTATE_ZA(operand[0]); when PSTATEField_PM => PSTATE.PM = operand[0]; end; 2026-03-26 20:27:25 2026-03_rel