bhyve: allow overriding snapshot socket directory

[novel]

Summary

By default bhyve(8) creates a snapshot socket in
"/var/run/bhyve/" (BHYVE_RUN_DIR).
As this is a system directory not writable by users,
this does not work when bhyve(8) is being started
as a non-root user.

Address that by allowing to override this directory.
In bhyve(8) it is done by setting 'rundir' option
with '-o rundir=<path>'.

In bhyvectl(8) it is done with '--rundir=<path>'.

Test Plan

sudo -u bhyve -g vmm bhyve -M -c 2 -m 4096 -o pci.enable_bars=1 -u -H -P \

-s 0:0,hostbridge -l bootrom,/usr/local/share/uefi-firmware/BHYVE_UEFI.fd \
-s 2:0,xhci,tablet -s 1:0,lpc \
-s 3:0,ahci,cd:/data/isos/alpine-standard-3.23.4-x86_64.iso \
-s 6:0,fbuf,tcp=127.0.0.1:5901 \
-l com1,stdio \
-o rundir=/tmp/bhyve_run \
alpine

sudo -u bhyve -g vmm bhyvectl --checkpoint=/tmp/vm --vm=alpine --rundir=/tmp/bhyve_run

[bnovkov]

usr.sbin/bhyve/amd64/bhyverun_machdep.c

71

This will fail to compile on a non-BHYVE_SNAPSHOT build otherwise.

usr.sbin/bhyvectl/bhyvectl.c

160

Isn't this array supposed to hold information about the type of the argument? Would it make more sense to put "path" here?

393–394

547–550

[bnovkov]

One more thing, could you please document this feature in bhyve's manpage?

[novel]

Address review comments.

[ziaee]

This is cool! Please add the docs to bhyvectl as well!

usr.sbin/bhyve/bhyve_config.5

229

Use the Pa macro to add filesystem paths to the whatis database. This facilitates searching the manual by filename.

[novel]

Address review comments about manpages.

[bcr]

The manpage looks good now, thanks!

[ziaee]

usr.sbin/bhyvectl/bhyvectl.8

43–44

We need it here too.

[novel]

bhyvectl.8: add '--rundir' to synopsis

[bnovkov]

Two more nits, looks good otherwise.

usr.sbin/bhyve/snapshot.c

1424–1432

usr.sbin/bhyvectl/bhyvectl.c

274–275

[novel]

Address comments (formatting).