mount_nfs accepts vers=4,soft options
nfs - NFS server and client
# man mount_nfs ... hard|soft Continue to retry requests until the server responds (hard) or give up and return an error (soft). The default value is hard. Note that NFSv4 clients do not support soft mounts. ...
# mount -F nfs -o vers=4,soft 192.168.129.1:/zones/uuid/data /mnt # mount -v | grep mnt 192.168.129.1:/zones/uuid/data on /mnt type nfs remote/read/write/setuid/nodevices/vers=4/soft/xattr/zone=uuid/dev=9300016 on Wed Jun 10 15:13:54 2020 #
Either mount should fail, or the man page is incorrect, or `soft` is being ignored (which the man page should say). I have not tried with LX or kvm/bhyve instances.