K 10
svn:author
V 3
kib
K 8
svn:date
V 27
2020-06-12T22:14:45.309141Z
K 7
svn:log
V 635
Control for Special Register Buffer Data Sampling mitigation.

New microcode update for Intel enables mitigation for SRBDS, which
slows down RDSEED and related instructions.  The update also provides
a control to limit the mitigation to SGX enclaves, which should
restore the speed of random generator by the cost of potential
cross-core bufer sampling.

See https://software.intel.com/security-software-guidance/insights/deep-dive-special-register-buffer-data-sampling

GIve the user control over it.

Reviewed by:	markj
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D25221

END