OpenBSD Errata: July 31st, 2018 (amdlfence)

Errata patches for the kernel have been released for OpenBSD 6.3 and 6.2.

On AMD CPUs, set a chicken bit which turns LFENCE into a serialization        
instruction against speculation.

Binary updates for the amd64 and i386 platforms are available via the
syspatch utility. Source code patches can be found on the respective
errata pages:

  https://www.openbsd.org/errata62.html
  https://www.openbsd.org/errata63.html

As these affect the kernel, a reboot will be needed after patching.