CSDB
Consumption of Speculative Data Barrier
Consumption of Speculative Data Barrier is a memory barrier that controls speculative execution and data value prediction.
No instruction other than branch instructions appearing in program order after the CSDB can be speculatively executed using the results of any:
Data value predictions of any instructions.
PSTATE.{N,Z,C,V} predictions of any instructions other than conditional branch instructions appearing in program order before the CSDB that have not been architecturally resolved.
Predictions of SVE predication state for any SVE instructions.
For purposes of the definition of CSDB, PSTATE.{N,Z,C,V} is not considered a data value. This definition permits:
Control flow speculation before and after the CSDB.
Speculative execution of conditional data processing instructions after the CSDB, unless they use the results of data value or PSTATE.{N,Z,C,V} predictions of instructions appearing in program order before the CSDB that have not been architecturally resolved.
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CSDB
SystemHintOp op;
case CRm:op2 of
when '0000 000' op = SystemHintOp_NOP;
when '0000 001' op = SystemHintOp_YIELD;
when '0000 010' op = SystemHintOp_WFE;
when '0000 011' op = SystemHintOp_WFI;
when '0000 100' op = SystemHintOp_SEV;
when '0000 101' op = SystemHintOp_SEVL;
when '0000 110'
if !HaveDGHExt() then EndOfInstruction(); // Instruction executes as NOP
op = SystemHintOp_DGH;
when '0000 111' SEE "XPACLRI";
when '0001 xxx'
case op2 of
when '000' SEE "PACIA1716";
when '010' SEE "PACIB1716";
when '100' SEE "AUTIA1716";
when '110' SEE "AUTIB1716";
otherwise EndOfInstruction(); // Instruction executes as NOP
when '0010 000'
if !HaveRASExt() then EndOfInstruction(); // Instruction executes as NOP
op = SystemHintOp_ESB;
when '0010 001'
if !HaveStatisticalProfiling() then EndOfInstruction(); // Instruction executes as NOP
op = SystemHintOp_PSB;
when '0010 010'
if !HaveSelfHostedTrace() then EndOfInstruction(); // Instruction executes as NOP
op = SystemHintOp_TSB;
when '0010 011'
if !IsFeatureImplemented(FEAT_GCS) then EndOfInstruction(); // Instruction executes as NOP
op = SystemHintOp_GCSB;
when '0010 100'
op = SystemHintOp_CSDB;
when '0010 110'
if !HaveFeatCLRBHB() then EndOfInstruction(); // Instruction executes as NOP
op = SystemHintOp_CLRBHB;
when '0011 xxx'
case op2 of
when '000' SEE "PACIAZ";
when '001' SEE "PACIASP";
when '010' SEE "PACIBZ";
when '011' SEE "PACIBSP";
when '100' SEE "AUTIAZ";
when '101' SEE "AUTIASP";
when '110' SEE "AUTIBZ";
when '111' SEE "AUTIBSP";
when '0100 xx0'
op = SystemHintOp_BTI;
// Check branch target compatibility between BTI instruction and PSTATE.BTYPE
SetBTypeCompatible(BTypeCompatible_BTI(op2<2:1>));
when '0101 000'
if !IsFeatureImplemented(FEAT_CHK) then EndOfInstruction(); // Instruction executes as NOP
op = SystemHintOp_CHKFEAT;
otherwise EndOfInstruction(); // Instruction executes as NOP
case op of
when SystemHintOp_YIELD
Hint_Yield();
when SystemHintOp_DGH
Hint_DGH();
when SystemHintOp_WFE
integer localtimeout = 1 << 64; // No local timeout event is generated
Hint_WFE(localtimeout, WFxType_WFE);
when SystemHintOp_WFI
integer localtimeout = 1 << 64; // No local timeout event is generated
Hint_WFI(localtimeout, WFxType_WFI);
when SystemHintOp_SEV
SendEvent();
when SystemHintOp_SEVL
SendEventLocal();
when SystemHintOp_ESB
if HaveTME() && TSTATE.depth > 0 then
FailTransaction(TMFailure_ERR, FALSE);
SynchronizeErrors();
AArch64.ESBOperation();
if PSTATE.EL IN {EL0, EL1} && EL2Enabled() then AArch64.vESBOperation();
TakeUnmaskedSErrorInterrupts();
when SystemHintOp_PSB
ProfilingSynchronizationBarrier();
when SystemHintOp_TSB
TraceSynchronizationBarrier();
when SystemHintOp_GCSB
GCSSynchronizationBarrier();
when SystemHintOp_CHKFEAT
X[16, 64] = AArch64.ChkFeat(X[16, 64]);
when SystemHintOp_CSDB
ConsumptionOfSpeculativeDataBarrier();
when SystemHintOp_CLRBHB
Hint_CLRBHB();
when SystemHintOp_BTI
SetBTypeNext('00');
otherwise // do nothing