MDSELR

Selects the current breakpoints or watchpoints accessed by System register instructions.

Configuration

This register is present only when FEAT_Debugv8p9 is implemented. Otherwise, direct accesses to MDSELR_EL1 are UNDEFINED.

Attributes

Field descriptions

Bits [63:6]

BANK, bits [5:4]

Breakpoint and watchpoint bank select.

BANK	Meaning	Applies when
0b00	Select 0 to 15.
0b01	Select 16 to 31.	When NUM_BREAKPOINTS > 16 or NUM_WATCHPOINTS > 16
0b10	Select 32 to 47.	When NUM_BREAKPOINTS > 32 or NUM_WATCHPOINTS > 32
0b11	Select 48 to 63.	When NUM_BREAKPOINTS > 48 or NUM_WATCHPOINTS > 48

Each of the following register names accesses a register for breakpoint or watchpoint <n>, where n = UInt(MDSELR_EL1.BANK:m[3:0]):

This field is ignored by the PE and treated as zeros when any of the following are true:

Executing at EL3 and MDCR_EL3.EBWE is 0.
Executing at EL2 and the Effective value of MDCR_EL2.EBWE is 0.
Executing at EL1 and the Effective value of MDSCR_EL1.EMBWE is 0.

The reset behavior of this field is:

On a Warm reset, this field resets to an architecturally UNKNOWN value.

Accessing this field has the following behavior:

Access is RES0 if NUM_BREAKPOINTS <= 16 and NUM_WATCHPOINTS <= 16.
Otherwise, access to this field is RW.

Bits [3:0]

Accessing MDSELR_EL1

When 16 or fewer breakpoints are implemented, 16 or fewer watchpoints are implemented, and MDSELR_EL1 is implemented as RAZ/WI, it is IMPLEMENTATION DEFINED whether these trap controls have any effect on accesses to MDSELR_EL1.

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

MRS <Xt>, MDSELR_EL1

op0	op1	CRn	CRm	op2
0b10	0b000	0b0000	0b0100	0b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3.EBWE == '0' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3.TDA == '1' then UNDEFINED; elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT2) && ((HaveEL(EL3) && SCR_EL3.FGTEn2 == '0') || HDFGRTR2_EL2.nMDSELR_EL1 == '0') then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && MDCR_EL2.<TDE,TDA> != '00' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && MDCR_EL3.EBWE == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif HaveEL(EL3) && MDCR_EL3.TDA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else X[t, 64] = MDSELR_EL1; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3.EBWE == '0' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3.TDA == '1' then UNDEFINED; elsif HaveEL(EL3) && MDCR_EL3.EBWE == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif HaveEL(EL3) && MDCR_EL3.TDA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else X[t, 64] = MDSELR_EL1; elsif PSTATE.EL == EL3 then X[t, 64] = MDSELR_EL1;

MSR MDSELR_EL1, <Xt>

op0	op1	CRn	CRm	op2
0b10	0b000	0b0000	0b0100	0b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3.EBWE == '0' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3.TDA == '1' then UNDEFINED; elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT2) && ((HaveEL(EL3) && SCR_EL3.FGTEn2 == '0') || HDFGWTR2_EL2.nMDSELR_EL1 == '0') then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && MDCR_EL2.<TDE,TDA> != '00' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && MDCR_EL3.EBWE == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif HaveEL(EL3) && MDCR_EL3.TDA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else MDSELR_EL1 = X[t, 64]; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3.EBWE == '0' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3.TDA == '1' then UNDEFINED; elsif HaveEL(EL3) && MDCR_EL3.EBWE == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif HaveEL(EL3) && MDCR_EL3.TDA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else MDSELR_EL1 = X[t, 64]; elsif PSTATE.EL == EL3 then MDSELR_EL1 = X[t, 64];

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																										BANK		RES0

MDSELR_EL1, Breakpoint and Watchpoint Selection Register

Purpose