stable/11 r329462 - Meltdown/Spectre MFC questions
Jeremy Chadwick
jdc at koitsu.org
Sat Feb 17 19:47:29 UTC 2018
Reference: https://svnweb.freebsd.org/base?view=revision&revision=329462
Do the following new loader tunables and sysctls have documentation
anywhere? I ask because I wish to know how to turn all of this off (yes
you heard me correctly), as not all systems necessarily require
mitigation of these flaws.
Best I can tell from skimming source:
vm.pmap.pti
- Description: Page Table Isolation enabled
- Loader tunable, visible in sysctl (read-only)
- Integer
- Default value: depends on CPU model and capabilities, see
function pti_get_default(); looks like AMD = 0, any CPU with
RDCL_NO capability enabled = 0, else 1
hw.ibrs_active
- Description: Indirect Branch Restricted Speculation active
- sysctl (read-only)
- Integer
- Real-time indicator as to if IBRS is currently on or off
hw.ibrs_disable
- Description: Disable Indirect Branch Restricted Speculation
- Loader tunable and sysctl tunable (read-write)
- Integer
- Default value: unsure. Variable declaration has 1 but
SYSCTL_PROC() macro has 0.
Thank you.
--
| Jeremy Chadwick jdc at koitsu.org |
| UNIX Systems Administrator http://jdc.koitsu.org/ |
| Making life hard for others since 1977. PGP 4BD6C0CB |
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