To mitigate the Meltdown and Spectre vulnerabilities, OpenBSD holds separate page tables for the kernel and userland.
The next generation of Meltdown was mitigated in this way. OpenBSD was no longer affected as memory could not be inappropriately accessed.
OpenBSD has also disabled Intel’s hyper-threading technology, citing security concerns – seemingly, Spectre-style concerns, with “a new hw.smt sysctl”.
Details: