amd64: Add sysctl knobs for loader tunables
AbandonedPublic
Actions

Authored by zlei on Oct 16 2023, 5:22 PM.

Details

Reviewers

kib
alc
grehan

Group Reviewers

bhyve

Summary

The following loader tunable do not have corresponding sysctl MIB
entries. Add them so that they can be retrieved, and sysctl -T will
also report them correctly.

hw.clflush_disable
hw.memtest.tests
hw.skz63_enable
hw.use_xsave
hw.vmm.ept.use_exec_only
hw.vmm.ept.use_hw_ad_bits
hw.vmm.ept.use_superpages
hw.vmm.npt.enable_superpage
hw.xsave_mask

MFC after: 1 week

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Skipped

Unit

Tests Skipped

Event Timeline

zlei created this revision.Oct 16 2023, 5:22 PM

Herald added a reviewer: bhyve. · View Herald TranscriptOct 16 2023, 5:22 PM

Herald added subscribers: bcran, rgrimes, imp. · View Herald Transcript

zlei requested review of this revision.Oct 16 2023, 5:22 PM

zlei added a parent revision: D42251: vmx: Prefer consistent naming for loader tunables.Oct 17 2023, 9:50 AM

alc added inline comments.Oct 17 2023, 5:09 PM

sys/amd64/vmm/amd/npt.c
51
62	I would suggest initializing the variables at their definitions, rather than at run-time.

kib added inline comments.Oct 17 2023, 5:44 PM

sys/amd64/amd64/fpu.c
173	The description is wrong. That said, I do not see much use for these and other x86-related tunables to be exposed as sysctl. They are debugging tools, useful only for people who understand the code.

zlei added inline comments.Oct 18 2023, 3:24 AM

sys/amd64/amd64/fpu.c
173	Thanks for the explanation. That make sense. Those tunables are not documented and confused me until `git blame` shows theirs history.

zlei mentioned this in D42218: x86: Add sysctl knobs for loader tunables.Oct 18 2023, 3:28 AM

zlei added a child revision: D42274: pmap: Prefer consistent naming for loader tunable.Oct 18 2023, 10:32 AM

kib added inline comments.Oct 18 2023, 4:40 PM

sys/amd64/amd64/fpu.c
173	If you want to add some information about these tunables, a source comment would be appropriate.

patmaddox added a subscriber: patmaddox.Oct 19 2023, 9:43 PM

Abandoned as no need to add sysctl knobs for debugging purpose only tunables.

They are debugging tools, useful only for people who understand the code.

sys/amd64/vmm/amd/npt.c
66	Actually the flag `enable_superpage` can be retrieved from `npt_flags` which is exposed via sysctl MIB `hw.vmm.npt.pmap_flags`. So `hw.vmm.npt.enable_superpage` should be for debugging purpose only. A new sysctl knob for it is redundant.
sys/amd64/vmm/intel/ept.c
76	Redundant. They can be retrieved from sysctl MIB `hw.vmm.ept.pmap_flags`.