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AMEVCNTR1<n>_EL0

AMEVCNTR1<n>_EL0, Activity Monitors Event Counter Registers 1, n = 0 - 15

The AMEVCNTR1<n>_EL0 characteristics are:

Purpose

Provides access to the auxiliary activity monitor event counters.

Configuration

AArch64 System register AMEVCNTR1<n>_EL0 bits [31:0] are architecturally mapped to AArch32 System register AMEVCNTR1<n>[31:0].

AArch64 System register AMEVCNTR1<n>_EL0 bits [63:0] are architecturally mapped to External register AMEVCNTR1<n>[63:0].

This register is present only when FEAT_AMUv1 is implemented. Otherwise, direct accesses to AMEVCNTR1<n>_EL0 are UNDEFINED.

Attributes

AMEVCNTR1<n>_EL0 is a 64-bit register.

Field descriptions

6362616059585756555453525150494847464544434241403938373635343332
313029282726252423222120191817161514131211109876543210
ACNT
ACNT

ACNT, bits [63:0]

Auxiliary activity monitor event counter n.

Value of auxiliary activity monitor event counter n, where n is the number of this register and is a number from 0 to 15.

If all of the following are true, reads of the AMEVCNTR1<n>_EL0 registers from EL0 or EL1 return (PCount<63:0> - AMEVCNTVOFF1<n>_EL2<63:0>), where PCount is the physical count returned when AMEVCNTR1<n>_EL0 is read from EL2 or EL3:

If the counter is enabled, writes to this register have UNPREDICTABLE results.

The reset behavior of this field is:

Accessing AMEVCNTR1<n>_EL0

If <n> is greater than or equal to AMCGCR_EL0 or FEAT_AMUv1p1 is implemented and auxiliary counter <n> is not implemented, then reads and writes of AMEVCNTR1<n>_EL0 are UNDEFINED.

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

MRS <Xt>, AMEVCNTR1<m>_EL0 ; Where m = 0-15

op0op1CRnCRmop2
0b110b0110b11010b110:m[3]m[2:0]

let m:integer = UInt(CRm[0] :: op2[2:0]); if !IsFeatureImplemented(FEAT_AMUv1) then Undefined(); elsif m >= NUM_AMU_CG1_MONITORS then Undefined(); elsif !IsG1ActivityMonitorImplemented(m) then Undefined(); elsif PSTATE.EL == EL0 then if HaveEL(EL3) && EL3SDDUndefPriority() && CPTR_EL3().TAM == '1' then Undefined(); elsif AMUSERENR_EL0().EN == '0' then if EL2Enabled() && HCR_EL2().TGE == '1' then AArch64_SystemAccessTrap(EL2, 0x18); else AArch64_SystemAccessTrap(EL1, 0x18); end; elsif EL2Enabled() && CPTR_EL2().TAM == '1' then AArch64_SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && !ELIsInHost(EL0) && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3().FGTEn == '1') && HAFGRTR_EL2()[(2 * m) + 18] == '1' then AArch64_SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && CPTR_EL3().TAM == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; elsif AMCR_EL0().CG1RZ == '1' then X{64}(t) = Zeros{64}; else X{64}(t) = AMEVCNTR1_EL0(m); end; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && CPTR_EL3().TAM == '1' then Undefined(); elsif EL2Enabled() && CPTR_EL2().TAM == '1' then AArch64_SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3().FGTEn == '1') && HAFGRTR_EL2()[(2 * m) + 18] == '1' then AArch64_SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && CPTR_EL3().TAM == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; elsif !IsHighestEL(PSTATE.EL) && AMCR_EL0().CG1RZ == '1' then X{64}(t) = Zeros{64}; else X{64}(t) = AMEVCNTR1_EL0(m); end; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && CPTR_EL3().TAM == '1' then Undefined(); elsif HaveEL(EL3) && CPTR_EL3().TAM == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; elsif !IsHighestEL(PSTATE.EL) && AMCR_EL0().CG1RZ == '1' then X{64}(t) = Zeros{64}; else X{64}(t) = AMEVCNTR1_EL0(m); end; elsif PSTATE.EL == EL3 then X{64}(t) = AMEVCNTR1_EL0(m); end;

MSR AMEVCNTR1<m>_EL0, <Xt> ; Where m = 0-15

op0op1CRnCRmop2
0b110b0110b11010b110:m[3]m[2:0]

let m:integer = UInt(CRm[0] :: op2[2:0]); if !IsFeatureImplemented(FEAT_AMUv1) then Undefined(); elsif m >= NUM_AMU_CG1_MONITORS then Undefined(); elsif !IsG1ActivityMonitorImplemented(m) then Undefined(); elsif IsHighestEL(PSTATE.EL) then AMEVCNTR1_EL0(m) = X{64}(t); else Undefined(); end;


2026-03-26 20:27:25, 2026-03_rel

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