[libvirt] configuration support to allow devices into cgroup devices devices.list inside libvirt_lxc container

Hi, I was having trouble with losetup inside libvirt_lxc container. Then I found that <mknod state="on"> will provide CAP_MKNOD capability. Even after enabling CAP_MKNOD in my container, I was not able to do 'losetup' because cgroup's device.list for my container dont have 'rwm' flags for loop devices ('b 7:* rwm' in /sys/fs/cgroup/devices/machine.slice/machine- lxc*.scope/user/*/c1.session/devices.list) Currently I have to manually do echo "b 7:* rwm" into /sys/fs/cgroup/devices/machine.slice/machine-lxc*.scope/devices.allow file before I login into the container in order to use loop devices. It will be useful if we have a way to do this through domain xml rather than manually doing it like what I'm doing now. I looked into rng files, but I'm not able to find a way to define 'b 7:* rwm' in xml. I just want to check with the devs if this is possible already. Otherwise I'll file one improvement bug. I think lxc already have a way to do this through lxc.cgroup.devices.allow Thanks, Mohan R