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 |
On Feb 17 11:47, Jeremy Chadwick wrote:>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. >+1. I have an Intel Atom D525 "Pineview" which I'm led to believe doesn't have these flaws and therefore unless it's detected and disabled automatically I too would like to have documentation on how to view the current status, and disable it as required. And thank you for pointing this out. I can now just wait a while to see what comes along rather than accidentally upgrading it and killing the already really slow performance. -- Matt
On 17.02.2018 20:47, Jeremy Chadwick wrote:> 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. >Strange thing is that tweaking `hw.ibrs_disable` has no effect on `hw.ibrs_active` on my side. -- David Marec https://lapinbilly.eu/