Re: [PATCH 1/4] [x86] Add command line option to enable/disable hyper-threading.

[Arjan van de Ven <arjan@infradead.org>]

> I'm just basing this on the history of the patch, which preceeds me, so
> if this is incorrect, please don't blame me for misinformation :)
> 
> The original patch claims that hyper-threading opens the user up to some
> sort of security risk involving hardware limitations in protecting
> memory across the threads. I can't recall all the details.
> 
> If this is wrong, I'm more than happy to just drop the whole damn patch.

that is not correct.
I suspect what is meant is the "attack" on older openssl versions where
you could in theory get SOME information about a key in use by snooping
cache patterns in a shared cache situation. By no means is it a "direct"
leak of any kind, and openssl has since then been fixed to not have as
many key-dependent execution streams anymore.

I would suggest you drop the patch; openssl has been long fixed, and it
was only a theoretical attack in the first place...
I'm not saying the attack isn't something that should be addressed.. but
it is, and disabling hyperthreading is not the right fix.


-- 
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