cpu: Fix O3 uncacheable load that is replayed but misses the TLB
This change fixes an issue in the O3 CPU where an uncachable instruction is attempted to be executed before it reaches the head of the ROB. It is determined to be uncacheable, and is replayed, but a PanicFault is attached to the instruction to make sure that it is properly executed before committing. If the TLB entry it was using is replaced in the interveaning time, the TLB returns a delayed translation when the load is replayed at the head of the ROB, however the LSQ code can't differntiate between the old fault and the new one. If the translation isn't complete it can't be faulting, so clear the fault.
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1 changed files with 15 additions and 0 deletions
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@ -1009,8 +1009,16 @@ BaseDynInst<Impl>::initiateTranslation(RequestPtr req, RequestPtr sreqLow,
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// One translation if the request isn't split.
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// One translation if the request isn't split.
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DataTranslation<BaseDynInstPtr> *trans =
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DataTranslation<BaseDynInstPtr> *trans =
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new DataTranslation<BaseDynInstPtr>(this, state);
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new DataTranslation<BaseDynInstPtr>(this, state);
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cpu->dtb->translateTiming(req, thread->getTC(), trans, mode);
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cpu->dtb->translateTiming(req, thread->getTC(), trans, mode);
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if (!translationCompleted()) {
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if (!translationCompleted()) {
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// The translation isn't yet complete, so we can't possibly have a
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// fault. Overwrite any existing fault we might have from a previous
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// execution of this instruction (e.g. an uncachable load that
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// couldn't execute because it wasn't at the head of the ROB).
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fault = NoFault;
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// Save memory requests.
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// Save memory requests.
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savedReq = state->mainReq;
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savedReq = state->mainReq;
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savedSreqLow = state->sreqLow;
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savedSreqLow = state->sreqLow;
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@ -1028,7 +1036,14 @@ BaseDynInst<Impl>::initiateTranslation(RequestPtr req, RequestPtr sreqLow,
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cpu->dtb->translateTiming(sreqLow, thread->getTC(), stransLow, mode);
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cpu->dtb->translateTiming(sreqLow, thread->getTC(), stransLow, mode);
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cpu->dtb->translateTiming(sreqHigh, thread->getTC(), stransHigh, mode);
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cpu->dtb->translateTiming(sreqHigh, thread->getTC(), stransHigh, mode);
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if (!translationCompleted()) {
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if (!translationCompleted()) {
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// The translation isn't yet complete, so we can't possibly have a
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// fault. Overwrite any existing fault we might have from a previous
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// execution of this instruction (e.g. an uncachable load that
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// couldn't execute because it wasn't at the head of the ROB).
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fault = NoFault;
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// Save memory requests.
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// Save memory requests.
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savedReq = state->mainReq;
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savedReq = state->mainReq;
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savedSreqLow = state->sreqLow;
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savedSreqLow = state->sreqLow;
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