Lead developer for OpenBSD Mark Kettenis has announced that OpenBSD will no longer enable Hyper-Threading on Intel processors by default. This move is intended to mitigate security exploits from the Spectre ecosystem as well as TLB and cache timing attacks, because important processor resources are no longer shared between threads. Their suspicion is that some of the unreleased (or yet unknown) attacks can be stopped using this approach.
This move is supported by the fact that most newer motherboards no longer provide an option to disable Hyper-Threading via BIOS. OpenBSD users who still want to use Hyper-Threading can manually enable support for it using the sysctl hw.smt. The developers are also looking into expanding this feature to other CPUs from other vendors, should they be affected, too.
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