BRBTGT<n>_EL1 | Jon's Arm Reference

This register is present only when FEAT_BRBE is implemented. Otherwise, direct accesses to BRBTGT<n>_EL1 are UNDEFINED.

Attributes

Field descriptions

ADDRESS, bits [63:0]:

Target virtual address of the Branch record.

When an indirect write occurs with a value with ADDRESS bits [63:P] indicating an invalid address, an UNKNOWN value which indicates an invalid address is written to bits [63:P].

An invalid address is:

For an address in a translation regime with 2 VA ranges, with bits [63:P] not all zeros or all ones.
For an address in a translation regime with a single VA range, with bits [63:P] not all zeros.

P is defined as:

56, when FEAT_LVA3 is implemented.
52, when FEAT_LVA is implemented.
48, otherwise.

The value in bits [P-1:0] is the value written.

When an indirect write occurs with a value with ADDRESS bits [63:P] indicating a valid address, the written value is written to bits [63:0], and a read of the register returns the written value.

The reset behavior of this field is:

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

Accessing this field has the following behavior:

Access to this field is RES0 if any the following are true:
- BRBINF<n>_EL1.VALID == '00'.
- BRBINF<n>_EL1.VALID == '10'.
Otherwise, access to this field is RO.

Access Instructions

BRBTGT<n>_EL1 is RES0 if n + (BRBFCR_EL1.BANK × 32) >= BRBIDR0_EL1.NUMREC.

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

MRS <Xt>, BRBTGT<m>_EL1 ; Where m = 0-31

(op0 = 0b10, op1 = 0b001, CRn = 0b1000, CRm = m[3:0], op2 = m[4]:0b10)

let m:integer = UInt(op2[2] :: CRm[3:0]); if !IsFeatureImplemented(FEAT_BRBE) then Undefined(); elsif HaveEL(EL3) && !(EffectivelyAtEL0InHost() || EffectivelyAtEL0NotInHost() || PSTATE.EL == EL3) && EL3SDDUndefPriority() && MDCR_EL3().SBRBE != '11' && SCR_EL3().NS == '0' then Undefined(); elsif HaveEL(EL3) && !(EffectivelyAtEL0InHost() || EffectivelyAtEL0NotInHost() || PSTATE.EL == EL3) && EL3SDDUndefPriority() && MDCR_EL3().SBRBE IN {'x0'} && SCR_EL3().NS == '1' then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3().FGTEn == '1') && HDFGRTR_EL2().nBRBDATA == '0' then AArch64_SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && MDCR_EL3().SBRBE != '11' && SCR_EL3().NS == '0' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; elsif HaveEL(EL3) && MDCR_EL3().SBRBE IN {'x0'} && SCR_EL3().NS == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; elsif m + (UInt(BRBFCR_EL1().BANK) * 32) >= NUM_BRBE_RECORDS then X{64}(t) = Zeros{64}; else X{64}(t) = BRBTGT_EL1(m); end; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && MDCR_EL3().SBRBE != '11' && SCR_EL3().NS == '0' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; elsif HaveEL(EL3) && MDCR_EL3().SBRBE IN {'x0'} && SCR_EL3().NS == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; elsif m + (UInt(BRBFCR_EL1().BANK) * 32) >= NUM_BRBE_RECORDS then X{64}(t) = Zeros{64}; else X{64}(t) = BRBTGT_EL1(m); end; elsif PSTATE.EL == EL3 then if m + (UInt(BRBFCR_EL1().BANK) * 32) >= NUM_BRBE_RECORDS then X{64}(t) = Zeros{64}; else X{64}(t) = BRBTGT_EL1(m); end; end;

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ADDRESS
ADDRESS

BRBTGT<n>_EL1, n = 0 - 31

Configuration

Attributes

Field descriptions

ADDRESS, bits [63:0]:

Access Instructions