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Comment by keldaris | Hacker News Reader

I'm frankly shocked Linus was anywhere near as restrained as he was upon seeing this monstrosity. Nothing of this sort should ever make it into the kernel without explicit and loudly announced opt-out switches. If anything close to this does make it in, even as an opt-in, this will easily be the biggest performance regression in recent (perhaps all-time?) kernel history.

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His restraint and the fact that this stuff is even being considered tells me this is a really really bad bug. I doubt he would be so cordial in any other situation.

Nothing like this should have ever made it into hardware. It's lazy implementation (or performance at the expense of security).

Performance at the expense of security is a compromise made daily in every aspect of IT. The only way to make systems perfectly secure is to make them unusable.

Now, you can certainly argue that this particular tradeoff wasn't worth it, and in hindsight it's certainly a questionable one. However, do note that side channel attacks have been known for decades (since out-of-order CPUs became widespread in the 90s) and until this point have rarely presented a significant threat to most systems.

I'd be more inclined to think this was someone who didn't understand the implications implementing a performance improvement. This bug is clearly deep into unk-unk (i.e. well past the known areas of concern) territory and took a great deal of insight to the fundamentals of speculative execution to discover.

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