Errata patches for the kernel have been released for OpenBSD 6.3 and 6.2. Incorrect initialization of the FPU caused floating point exceptions when running on Xen.
Binary updates for the amd64 platform 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.