Re: [libvirt] mdevctl: A shoestring mediated device management and persistence utility

That is true irrespective of the usage, isn’t it? In other words, when you invoke `mdevctl create-mdev`, you assert “I own that specific parent/type”. At least, that’s how I read the way the script behaves today. Whether you invoke uuidgen inside or outside the script does not change that assertion (at least with today’s code). I agree there is a race, but if anything, having a usage where you don’t pass the UUID on the command line is a step in the right direction. It leaves the door open for the create-mdev script to do smarter things, like deferring the allocation of the mdevs to an entity that has slightly more knowledge of the global system state than uuidgen. In other words, in my mind, `mdevctl create-mdev parent type` does not imply “this will use uuidgen” but rather, if anything, implies “this will do the right thing to prevent the race in the future, even if that’s more complex than just calling uuidgen”. However, I believe that this means we should reorder the args further. I would suggest something like: mdevctl create-mdev <mdev-type> [<parent-device> [<mdev-uuid>]] where 1 arg means you let mdevctl choose the parent device for you (future) (e.g. I want a VGPU of this type, I don’t really care where it comes from) 2 args mean you want that specific type/parent combination 3 args mean you assert you own that device That also implies that mdevctl create-mdev should output what it allocated so that some higher-level software can tell “OK, that’s the instance I got”. Done.