
Torvalds Blasts “Beyond Stupid” Flushing L1d on Context Switches - signa11
https://www.phoronix.com/scan.php?page=news_item&px=Linux-Blasts-L1d-Flushing
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RNCTX
A bit sensational on the headline (as they do), the criticism in this case is
pretty tame, imo.

I think it's a testament to the success and longevity of the Linux kernel that
people truly striving for objectivity and separation from monetary interest
can look at the Intels and Amazons of the world and say "no, you fix your
thing, do not try to force a work-around on everyone else."

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inshadows
Quote from Igno Molnar:

Typically cloud computing systems such as AWS will have SMT enabled, because
cloud computing pricing is essentially per vCPU, and they want to sell the
hyperthreads as vCPUs. So the safest solution, disabling SMT on affected
systems, is not actually done, because it's an economic non-starter. (I'd like
to note the security double standard there: the most secure option, to disable
SMT, is not actually used ...)

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mrweasel
> Typically cloud computing systems such as AWS will have SMT enabled

Isn't that counter intuitive? Cloud computing seems like the only place where
you should ALWAYS disable SMT. For workstations, home computers, non-shared
servers and so on, it's doesn't really matter that much and you can safely
leave SMT on.

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WJW
If user security is more important than revenue, turn SMT on. If revenue is
more important than user security, turn it off. It's easy to predict which
option will be chosen by the big cloud providers, all of which are are very
large public companies with a history of optimizing for cost savings over
customer service.

On the plus side, there might be a gap in the market if you can brand yourself
as the secure alternative to the subset of customers who really cares about it
even if they have to pay double.

