Linux4.20針對Meltdown/Spectre/..修正 - 3C

其實Linus Torvalds有表態
https://lkml.org/lkml/2018/11/19/37

STIBP by default.. Revert?

This was marked for stable, and honestly, nowhere in the discussion did I see an
y mention of just *how* bad the performance impact of this was.

When performance goes down by 50% on some loads, people need to start asking the
mselves whether it was worth it.
It's apparently better to just disable SMT entirely, which is what security-cons
cious people do anyway.

So why do that STIBP slow-down by default when the people who *really* care alre
ady disabled SMT?

I think we should use the same logic as for L1TF: we default to something that d
oesn't kill performance.
Warn once about it, and let the crazy people say "I'd rather take a 50% performa
nce hit than worry about a theoretical issue".

Linus

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...關掉或本來就沒HT
就沒這次安全問題的煩惱了吧(眼神死

STIBP也不是核心4.20之後才會加入
目前維護中的核心
4.19.2
https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.2
4.18.19
https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.18.19
4.14.81
https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.14.81
4.9.137
https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.9.137
皆已獲得STIBP新功能...

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