bhyve: Introduce monitor mode
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Authored by bnovkov on Thu, Nov 13, 11:13 AM.

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Reviewers

markj
andrew

Group Reviewers

bhyve

Summary

This change introduces "monitor mode", a mechanism for automatically
releasing virtual machine resources when bhyve dies, bringing us
closer towards making non-root bhyve viable.
Under this regime bhyve will create a transient virtual machine using
vmmctl's VMMCTL_CREATE_DESTROY_ON_CLOSE flag and automatically
reboot said virtual machine as long as it exits with "reboot" status.

This is done by splitting bhyve into two processes. The parent process
creates the virtual machine while the child process initializes and
runs the virtual machine. When the child exits the parent inspects
its exit status and either exits or forks again. vmmctl automatically
destroys the underlying virtual machine once the parent process dies.

Sponsored by: The FreeBSD Foundation
Sponsored by: Klara, Inc.

Diff Detail

Repository

rG FreeBSD src repository

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Build Status

Buildable 68597
Build 65480: arc lint + arc unit

Event Timeline

bnovkov created this revision.Thu, Nov 13, 11:13 AM

Herald added a reviewer: andrew. · View Herald TranscriptThu, Nov 13, 11:13 AM

Herald added subscribers: ziaee, bcran, rgrimes and 2 others. · View Herald Transcript

bnovkov requested review of this revision.Thu, Nov 13, 11:13 AM

Harbormaster completed remote builds in B68597: Diff 166353.Thu, Nov 13, 11:13 AM

bnovkov added a parent revision: D53730: bhyve: Eliminate exit status magic numbers.Thu, Nov 13, 11:13 AM

markj added inline comments.Tue, Nov 18, 3:31 PM

usr.sbin/bhyve/bhyve.8
278	I think "VM terminate with exit status 0" is a bit unclear. The main point is that the bhyve process doesn't exit when the guest reboot, so maybe, .It Fl M Run the VM in .Ql monitor mode. In this mode, a guest reboot does not cause the bhyve process to exit. Instead, bhyve will restart the VM. Once the bhyve process exits or is killed, the VM will be destroyed automatically.
279
usr.sbin/bhyve/bhyverun.c
896	I think you probably want a loop around the waitpid() call, in case EINTR is returned.
901	What if `status` indicates that the child was killed by a signal? You need to write: if (WIFSIGNALED(status)) { <print a message saying the child was killed by signal WTERMSIG(status)> exit(); } else { status = WEXITSTATUS(status); if (status != BHYVE_EXIT_RESET) exit(status); ... }