I followed +LWN.net’s link to lore.kernel.org this morning, and clicked on the first link I saw, with a fairly innocuous title. It seemed a slightly odd post for LKML, because disabling hyperthreading isn’t a new question; there have long been recognized workloads for which that’s a good idea. But that’s not really what it’s about.

It’s really about this quote from an upcoming blackhat presentation: “Our TLBleed exploit successfully leaks a 256-bit EdDSA key from libgcrypt (used in e.g. GPG) with a 98% success rate after just a single observation of signing operation on a co-resident hyperthread and just 17 seconds of analysis time.”

I wonder if there are cloud vendors whose cheapest instances share hyperthreads with other domains?


Linux on Intel x86: How to disable Hyperthreading

Alan Cox June 24, 2018 08:53

Probably.. but you shouldn’t be running software that doesn’t do constant time constant data crypto on random cloud nodes IMHO.

For better providers I doubt it’s a concern for ht pairs - they go to a lot of trouble to give people predictable meaningful amounts of CPU when that is what they bill by

Imported from Google+ — content and formatting may not be reliable