Disabling speculative execution mitigations

[Ed Maste]

On Fri, 6 Dec 2019 at 22:54, O'Connor, Daniel <darius at dons.net.au> wrote:
>
> With respect to the man page, I find it difficult to know what a given value for each sysctl will do, as evidenced by my confusion above about IBRS.

scottl recently moved these sysctls to machdep.mitigations in r355436,
but they've kept the existing names and sense. So, some still have an
enable control while some are disable, some report "state: inactive"
while others report "active: 0".

Work is ongoing now to rationalize these so that the sense is true for
mitigation enabled. Backwards compatibility will be maintained for the
sysctl paths in stable (e.g. hw.ibrs*) but not the interim names
(machdep.mitigations.*)