svn commit: r328625 - in head/sys: amd64/amd64 amd64/ia32 amd64/include dev/cpuctl i386/i386 x86/include x86/x86

[Bjoern A. Zeeb]

On 31 Jan 2018, at 14:36, Konstantin Belousov wrote:

> Author: kib
> Date: Wed Jan 31 14:36:27 2018
> New Revision: 328625
> URL: https://svnweb.freebsd.org/changeset/base/328625
>
> Log:
>   IBRS support, AKA Spectre hardware mitigation.

>   For existing processors, you need a microcode update which adds IBRS
>   CPU features, and to manually enable it by setting the 
> tunable/sysctl
>   hw.ibrs_disable to 0.  Current status can be checked in sysctl
>   hw.ibrs_active.  The mitigation might be inactive if the CPU feature

Can you change the tunable/sysctl to hw.ibrs_enable[d] (and toggle the 
default setting along).
I find it highly confusing to have two different sysctls “disable” 
and “active” and a lot
of people (and cultures) have trouble with the double negative.
Also the “enable[d]” variant seems to be pre-dominant in the kernel.

Also can we spell IBRS in the sysctl description as “Indirect Branch 
Restricted Speculation (IBRS)”?

Thanks
/bz