AMEVCNTR0<n>

AArch64 System register AMEVCNTR0<n>_EL0 bits [31:0] are architecturally mapped to AArch32 System register AMEVCNTR0<n>[31:0].

AArch64 System register AMEVCNTR0<n>_EL0 bits [63:0] are architecturally mapped to External register AMU.AMEVCNTR0<n>[63:0].

This register is present only when FEAT_AMUv1 is implemented. Otherwise, direct accesses to AMEVCNTR0<n>_EL0 are UNDEFINED.

Attributes

Field descriptions

ACNT, bits [63:0]

Architected activity monitor event counter n.

Value of architected activity monitor event counter n, where n is the number of this register and is a number from 0 to 3.

If all of the following are true, reads of the AMEVCNTR0<n>_EL0 registers from EL0 or EL1 return (PCount<63:0> - AMEVCNTVOFF0<n>_EL2<63:0>), where PCount is the physical count returned when AMEVCNTR0<n>_EL0 is read from EL2 or EL3:

FEAT_AMUv1p1 is implemented.
HCR_EL2.AMVOFFEN and SCR_EL3.AMVOFFEN are 1.
EL2 is implemented and enabled in the current Security state, and the Effective value of HCR_EL2.{E2H, TGE} is not {1, 1}.

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

The reset behavior of this field is:

On an AMU reset, this field resets to 0.

Accessing AMEVCNTR0<n>_EL0

If <n> is greater than or equal to the number of architected activity monitor event counters, reads and writes of AMEVCNTR0<n>_EL0 are UNDEFINED.

Note

AMCGCR_EL0.CG0NC identifies the number of architected activity monitor event counters.

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

MRS <Xt>, AMEVCNTR0<m>_EL0 ; Where m = 0-3

op0	op1	CRn	CRm	op2
0b11	0b011	0b1101	0b010:m[3]	m[2:0]

integer m = UInt(CRm<0>:op2<2:0>); if m >= 4 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); 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.AMEVCNTR0<m>_EL0 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && CPTR_EL3.TAM == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else X[t, 64] = AMEVCNTR0_EL0[m]; 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.AMEVCNTR0<m>_EL0 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && CPTR_EL3.TAM == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else X[t, 64] = AMEVCNTR0_EL0[m]; 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); else X[t, 64] = AMEVCNTR0_EL0[m]; elsif PSTATE.EL == EL3 then X[t, 64] = AMEVCNTR0_EL0[m];

MSR AMEVCNTR0<m>_EL0, <Xt> ; Where m = 0-3

op0	op1	CRn	CRm	op2
0b11	0b011	0b1101	0b010:m[3]	m[2:0]

integer m = UInt(CRm<0>:op2<2:0>); if m >= 4 then UNDEFINED; elsif IsHighestEL(PSTATE.EL) then AMEVCNTR0_EL0[m] = 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
ACNT
ACNT

AMEVCNTR0<n>_EL0, Activity Monitors Event Counter Registers 0, n = 0 - 3