MECIDR_EL2, MEC Identification Register

The MECIDR_EL2 characteristics are:

Purpose

MEC identification register.

Configuration

This register is present only when FEAT_MEC is implemented and FEAT_AA64 is implemented. Otherwise, direct accesses to MECIDR_EL2 are UNDEFINED.

If EL2 is not implemented, this register is RES0 from EL3.

Attributes

MECIDR_EL2 is a 64-bit register.

Field descriptions

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
RES0																												MECIDWidthm1

Bits [63:4]

Reserved, RES0.

MECIDWidthm1, bits [3:0]

MECID width minus 1.

The value of this field plus 1 is the MECID width in bits, that this PE supports.

For example, the value 0b1111 indicates that this PE supports a MECID width of 16 bits, and provides 2¹⁶ possible MECID values.

MECIDWidth is defined as MECIDR_EL2.MECIDWidthm1 + 1.

This field has an IMPLEMENTATION DEFINED value.

Access to this field is RO.

Accessing MECIDR_EL2

For accesses from EL2 and EL3, this register is RO.

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

MRS <Xt>, MECIDR_EL2

op0	op1	CRn	CRm	op2
0b11	0b100	0b1010	0b1000	0b111

if !(IsFeatureImplemented(FEAT_MEC) && IsFeatureImplemented(FEAT_AA64)) then UNDEFINED; elsif PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then X[t, 64] = MECIDR_EL2; elsif PSTATE.EL == EL3 then X[t, 64] = MECIDR_EL2;

21/03/2025 17:52; 154105dd5041532b480d9ef0c018b8420cbe5c19