STIBP, Collaborate, and Listen: Linus Floats Linux Kernel That ‘Fixes’ Intel CPUs’ Spectre Slowdown


Linus Torvalds has stuck to his “no swearing” resolution with his regular Sunday night Linux kernel release candidate announcement.

Probably the most important aspect of the weekend’s release candidate is that it, in a way, improves the performance of STIBP, which is a mitigation that stops malware exploiting a Spectre security vulnerability variant in Intel processors.

In November, it emerged that STIBP (Single Thread Indirect Branch Predictors), which counters Spectre Variant 2 attacks, caused nightmare slowdowns in some cases. The mitigation didn’t play well with simultaneous multi-threading (SMT) aka Intel’s Hyper Threading, and software would take up to a 50 per cent performance hit when the security measure was enabled. Linux 4.20-rc5, emitted on Sunday, addresses this performance issue by making the security defense optional… 

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