vmgenc.4: add manual page for VM Generation Counter driver
ClosedPublic
Actions

Authored by longros on Mar 21 2026, 7:54 AM.

Details

Reviewers

cem
imp
ziaee

Group Reviewers

manpages

Commits

rG37bd9f15e37e: vmgenc.4: Add VM Generation ID Counter manual
rG252f0c28855b: vmgenc.4: Add VM Generation ID Counter manual
rG59cb18f35617: vmgenc.4: Add VM Generation ID Counter manual

Summary

Document the vmgenc(4) ACPI driver which detects virtual machine
cloning and snapshot restoration via the VM Generation ID
specification. The driver reseeds the kernel entropy pool when
a generation change is detected.

Signed-off-by: Christos Longros <chris.longros@gmail.com>

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Not Applicable

Unit

Tests Not Applicable

Event Timeline

longros created this revision.Mar 21 2026, 7:54 AM

Herald added subscribers: ziaee, imp. · View Herald TranscriptMar 21 2026, 7:54 AM

longros requested review of this revision.Mar 21 2026, 7:54 AM

Harbormaster completed remote builds in B71619: Diff 174076.Mar 21 2026, 7:54 AM

longros added reviewers: cem, imp.Mar 21 2026, 7:55 AM

Text looks reasonable to me. I did not verify formatting / doc best practices (section order, etc).

This revision is now accepted and ready to land.Mar 21 2026, 4:42 PM

I previewed it with

man -l ~/freebsd/freebsd-src/share/man/man4/vmgenc.4

mandoc

gives no errors.

ziaee added a reviewer: manpages.Mar 21 2026, 7:21 PM

Ok from manpages, let me know what you want to do w/rt synopsis formatting.

share/man/man4/vmgenc.4
14–26	Any chance I can get you to use a more mdoc(7) conformant format? We have almost two hundred manpages that follow this format, like vt(4) or uftdi(4), and I've proposed in talks and on arch@ trying to get everything to use this consistently. It is more consistent, concise, and has the added benefit of increased search indexing in the manpages database, and in my talk on youtube, mandoc upstream said they also support this change as a move towards greater correctness in consistency.

Updated SYNOPSIS to use modern .Cd format.

This revision now requires review to proceed.Mar 21 2026, 7:49 PM

Harbormaster completed remote builds in B71630: Diff 174088.Mar 21 2026, 7:49 PM

I was doing a final look-over before commit and had some ideas that may or may not be useful.

share/man/man4/vmgenc.4
12	Does this make sense (im unfamiliar with the underlying topic)? I'm thinking maybe someone could search "virtual machine generation id" or maybe even "machine generation id", but i don't know if that's realistic or disturbs the meaning.
23	Maybe? acpi4 refers to the driver and not the underlying concept, not sure if that's true here.