Tweet-sized explanation of Foreshadow: Intel chips with speculative execution erroneously use OS-private bits of not-present page table entries as physical addresses, allow reading L1-cached data from resulting location via timing side-channel.
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There's no way Spectre is going to be fixed without just nuking speculative execution from orbit. It was a bad idea. Go back to 90s-era microarchitectures and start over figuring out how to make it fast.
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Replying to @RichFelker
There is also no way society is going to give up speed gains for the sake of security. As
@securelyfitz put it to me some months back. Spec ex is inherently a side channel; it's bad we took so long to realize it, but we have to live with it if we want forward progress.3 replies 0 retweets 0 likes -
Replying to @cr1901 @securelyfitz
The speed gains are marginal, and negative if you're measuring performance per watt or per area. If the Centerton microarchitecture had not been abandoned and had been heavily invested in, we'd likely have in-order, non-speculative chips competitive with Spectre-hell.
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Replying to @RichFelker @securelyfitz
The only real saving grace of your proposal is that in practice, in order CPUs can be usable desktop systems (source: I have an in order Atom netbook that's still useable). But usable != pleasant.
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They'd be a lot better than just "usable" if all of Intel's, AMD's, and ARM's R&D budgets over the past 15 years had been poured into them rather than into speculative foolery.
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