ID_AA64DFR2

For general information about the interpretation of the ID registers, see 'Principles of the ID scheme for fields in ID registers'.

Configuration

Attributes

Field descriptions

Bits [63:8]

BWE, bits [7:4]

Breakpoints and watchpoint enhancements.

The value of this field is an IMPLEMENTATION DEFINED choice of:

BWE	Meaning
0b0000	This field does not indicate whether DBGBCR<n>_EL1.MASK and address mismatch breakpoints are implemented.
0b0001	DBGBCR<n>_EL1.MASK and address mismatch breakpoints are implemented.
0b0010	As 0b0001, and address mismatch watchpoints are implemented.

All other values are reserved.

FEAT_BWE implements the functionality identified by the value 0b0001.

FEAT_BWE2 implements the functionality identified by the value 0b0010.

From Armv9.5, the permitted values are 0b0000 and 0b0010.

When this field is 0b0000, ID_AA64DFR1_EL1.ABLE might indicate the presence of support for DBGBCR<n>_EL1.MASK and address mismatch breakpoints.

Access to this field is RO.

STEP, bits [3:0]

Enhanced Software Step Extension.

The value of this field is an IMPLEMENTATION DEFINED choice of:

STEP	Meaning
0b0000	Execution from MDSTEPOP_EL1 is not supported for Software Step.
0b0001	Execution from MDSTEPOP_EL1 is supported for Software Step.

All other values are reserved.

FEAT_STEP2 implements the functionality identified by the value 0b0001.

Access to this field is RO.

Accessing ID_AA64DFR2_EL1

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

MRS <Xt>, ID_AA64DFR2_EL1

op0	op1	CRn	CRm	op2
0b11	0b000	0b0000	0b0101	0b010

if PSTATE.EL == EL0 then if IsFeatureImplemented(FEAT_IDST) then if EL2Enabled() && HCR_EL2.TGE == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else AArch64.SystemAccessTrap(EL1, 0x18); else UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && (IsFeatureImplemented(FEAT_FGT) || !IsZero(ID_AA64DFR2_EL1) || boolean IMPLEMENTATION_DEFINED "ID_AA64DFR2_EL1 trapped by HCR_EL2.TID3") && HCR_EL2.TID3 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else X[t, 64] = ID_AA64DFR2_EL1; elsif PSTATE.EL == EL2 then X[t, 64] = ID_AA64DFR2_EL1; elsif PSTATE.EL == EL3 then X[t, 64] = ID_AA64DFR2_EL1;

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																								BWE				STEP

ID_AA64DFR2_EL1, Debug Feature Register 2

Purpose