vmm: Fully adopt the getrlimit(2) machinery for limiting the number of VMM instances
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Authored by bnovkov on May 18 2026, 3:33 PM.

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Reviewers

markj
des
olce

Group Reviewers

bhyve

Summary

The vmm module currently combines parts of the kernelspace
getrlimit(2) machinery and a sysctl value to limit the number
of VMM instances per-UID. The original rationale for this
approach was to sidestep the convoluted way in which per-UID
getrlimit(2) limit values are currently propagated.

However, this approach deviates from the expected workflow when dealing
getrlimit(2) limits.

Fix this by teaching login(1) about RLIMIT_VMM and changing
vmmdev_create to use lim_cur. While we're here, document the limit
in the getrlimit(2) manpage.

Fixes: 1092ec8b3375 ("kern: Introduce RLIMIT_VMM")

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rG FreeBSD src repository

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Buildable 74774
Build 71657: arc lint + arc unit

Event Timeline

bnovkov created this revision.May 18 2026, 3:33 PM

Herald added subscribers: ziaee, imp. · View Herald TranscriptMay 18 2026, 3:33 PM

bnovkov requested review of this revision.May 18 2026, 3:33 PM

Harbormaster completed remote builds in B73194: Diff 178018.May 18 2026, 3:33 PM

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bnovkov mentioned this in D57259: libsys, libutil: Document RLIMIT_VMM.May 26 2026, 9:16 PM

des accepted this revision.Fri, Jul 10, 4:10 PM

This revision is now accepted and ready to land.Fri, Jul 10, 4:10 PM

des added inline comments.Fri, Jul 10, 4:11 PM

usr.bin/login/login.conf
47

markj added inline comments.Fri, Jul 10, 4:14 PM

usr.bin/login/login.conf
47	So we're changing the existing limit to unlimited, I guess because there's no way to express a constant like `4 * mp_ncpus` here?

des added inline comments.Fri, Jul 10, 4:15 PM

usr.bin/login/login.conf
47	It's still named `vms` elsewhere, I think we should standardize on `vmm` to reflect `RLIMIT_VMM`.

bnovkov added inline comments.Fri, Jul 10, 4:16 PM

usr.bin/login/login.conf
47	Yes, I'm not aware of way to dynamically populate `login.conf` with a machine-specific value.

markj accepted this revision as: markj.Fri, Jul 10, 4:23 PM

markj added inline comments.

sys/dev/vmm/vmm_dev.c
1021	Do you mind adding an EXTERROR() here? Could be done in a separate patch.

bnovkov added inline comments.Sun, Jul 12, 11:14 AM

sys/dev/vmm/vmm_dev.c
1021	Sure, I see quite a few other places where `dev/vmm` doesn't use EXTERROR so I'll plug those as well
usr.bin/login/login.conf
47	Agreed, I'll update the patch to include the rename.