supports the Security Extensions or not. This bit is not the same as the CPU one.
Currently we are not checking for either before trying to write to the special
registers. This can lead to problems on hardware or simulators that do not
provide the security extensions. Add the missing checks. Their interactions with
the CPU flag is not entirely clear to me but using a macro will make it easier
to quickly adjust the condition once the CPU bits are sorted as well.
Reviewed by: br
Sponsored by: DARPA/AFRL
Differential Revision: https://reviews.freebsd.org/D6397
1f420ed469