K 10
svn:author
V 3
kib
K 8
svn:date
V 27
2020-05-20T22:00:31.466791Z
K 7
svn:log
V 429
amd64: Add a knob to flush RSB on context switches if machine has SMEP.

The flush is needed to prevent cross-process ret2spec, which is not handled
on kernel entry if IBPB is enabled but SMEP is present.
While there, add i386 RSB flush.

Reported by:	Anthony Steinhauser <asteinhauser@google.com>
Reviewed by:	markj, Anthony Steinhauser
Discussed with:	philip
admbugs:	961
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

END