Nfs mount 'gone' after vm's start

[Marc Roos]

I have had a nfs-ganesha mount provision install images for vm's, and 
recently I have the mount stall after starting a vm. (even when it does 
not access an iso image on the nfs mount)

I have the host ip on a macvtap of the connected interface. The vm is 
also having an macvtap on the same interface to allow host-guest 
communication. 

I am mounting the nfs with these options.
nfs4   
ro,vers=4,proto=tcp,soft,nodev,_netdev,noatime,timeo=30,x-systemd.device
-timeout=30,x-systemd.mount-timeout=30,x-systemd.automount,x-systemd.idl
e-timeout=30  0 0

The problem is fixed by doing a simple 'umount -l'

Anyone seen something similar? I suspect this could be related by the 
macvtap being created, but I cannot remember seeing this mount fail 
before.