When people slam CPU manufacturers for Spectre, remember: Customers demanded speed doubling on legacy code, CPU vendors bent over backwards to accomodate programmers that did not want to learn parallelism.
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CPUs were plenty fast for desktop/office/web/etc. use 15-20 years ago. Comparable apps run SLOWER on affordable systems now than they did then due to much worse software architectures (giant js apps, etc.).
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Moreover OOOE can be made safe, at low or no perf cost, if you're careful about cache side effects. Vendors traded marginal perf/$ gain for sloppiness that compromised safety.
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Show me. And performance needed for better energy usage, doing more work.
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Naive approach which likely works (but needs verification): never fetch cache lines speculatively, only speculate with already-in-cache data.
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You said minimal performance impact. That won't be true. Hiding latency of cache miss by speculating on addresses crucial
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Tagging cache units with branch IDs and flush as branches become invalid?
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Flushing is pointless because the speculative load will invalidate the attackers cache line anyway, letting her know which line was loaded. We need a hidden cache that can somehow be made 'visible' when a speculated branch is taken. ARM spec allows hidden cache levels for e.g.
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I think it's also possible to speculatively fetch to visible cache as long as the address to fetch is a retired result, not speculative, but not 100% sure.
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Come on, nobody wants to be the last ceo to draw a diagonal line on Moore's law.
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absolutely agree
@RichFelker--consumers weren't the ones who invented Moore's law or geared corporate R&D to follow it. The GHz wars illustrate supply leading demand too; once they ended, the marketers continued business as usual by any means necessary (consider Appl*'s approach)Thanks. Twitter will use this to make your timeline better. UndoUndo
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