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

On Thu, 23 May 2019 17:20:01 -0600 Alex Williamson <alex.williamson(a)redhat.com&gt; wrote: > Hi, > > Currently mediated device management, much like SR-IOV VF management, > is largely left as an exercise for the user. This is an attempt to > provide something and see where it goes. I doubt we'll solve > everyone's needs on the first pass, but maybe we'll solve enough and > provide helpers for the rest. Without further ado, I'll point to what > I have so far: > > https://github.com/awilliam/mdevctl > > This is inspired by driverctl, which is also a bash utility. mdevctl > uses udev and systemd to record and recreate mdev devices for > persistence and provides a command line utility for querying, listing, > starting, stopping, adding, and removing mdev devices. Currently, for > better or worse, it considers anything created to be persistent. I can > imagine a global configuration option that might disable this and > perhaps an autostart flag per mdev device, such that mdevctl might > simply "know" about some mdevs but not attempt to create them > automatically. Clearly command line usage help, man pages, and > packaging are lacking as well, release early, release often, plus this > is a discussion starter to see if perhaps this is sufficient to meet > some needs. > > Originally I thought about making a utility to manage both mdev and > SR-IOV VFs all in one, but it seemed more natural to start here > (besides, I couldn't think of a good name for the combined utility). > If this seems useful, maybe I'll start on a vfctl for SR-IOV and we'll > see whether they have enough synergy to become one. > > It would be really useful if s390 folks could help me understand > whether it's possible to glean all the information necessary to > recreate a ccw or ap mdev device from sysfs. I expect the file where > we currently only store the mdev_type to evolve into something that > includes more information to facilitate more complicated devices. For > now I make no claims to maintaining compatibility of recorded mdev > devices, it will absolutely change, but I didn't want to get bogged > down in making sure I don't accidentally source a root kit hidden in an > mdev config file. I played a bit with it on my LPAR, and it is at least not obviously broken with vfio-ccw :) I don't have any ap devices to play with, though.

> I'm also curious how or if libvirt or openstack might use this. If > nothing else, it makes libvirt hook scripts easier to write, especially > if we add an option not to autostart mdevs, or if users don't mind > persistent mdevs, maybe there's nothing more to do. > > BTW, feel free to clean up by bash, I'm a brute force and ignorance > shell coder ;) Not that I'm a good shell coder, but I sent you a pull req at least adding a basic help text ;) I have not yet looked at most of the code, though.