On Wed, Jun 19, 2019 at 12:46:33PM -0600, Alex Williamson wrote: > On Wed, 19 Jun 2019 11:46:59 +0200 > Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > > > On Wed, 19 Jun 2019 08:28:02 +0100 > > Daniel P. Berrangé <berrange@xxxxxxxxxx> wrote: > > > > > On Tue, Jun 18, 2019 at 04:12:10PM -0600, Alex Williamson wrote: > > > > On Tue, 18 Jun 2019 14:48:11 +0200 > > > > Sylvain Bauza <sbauza@xxxxxxxxxx> wrote: > > > > > > > > > On Tue, Jun 18, 2019 at 1:01 PM Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > > > > > > > > I think we need to reach consensus about the actual scope of the > > > > > > mdevctl tool. > > > > > > > > > > > > > > > > > Thanks Cornelia, my thoughts: > > > > > > > > > > - Is it supposed to be responsible for managing *all* mdev devices in > > > > > > the system, or is it more supposed to be a convenience helper for > > > > > > users/software wanting to manage mdevs? > > > > > > > > > > > > > > > > The latter. If an operator (or some software) wants to create mdevs by not > > > > > using mdevctl (and rather directly calling the sysfs), I think it's OK. > > > > > That said, mdevs created by mdevctl would be supported by systemctl, while > > > > > the others not but I think it's okay. > > > > > > > > I agree (sort of), and I'm hearing that we should drop any sort of > > > > automatic persistence of mdevs created outside of mdevctl. The problem > > > > comes when we try to draw the line between unmanaged and manged > > > > devices. For instance, if we have a command to list mdevs it would > > > > feel incomplete if it didn't list all mdevs both those managed by > > > > mdevctl and those created elsewhere. For managed devices, I expect > > > > we'll also have commands that allow the mode of the device to be > > > > switched between transient, saved, and persistent. Should a user then > > > > Hm, what's the difference between 'saved' and 'persistent'? That > > 'saved' devices are not necessarily present? > > It seems like we're coming up with the following classes: > > 1) transient > a) mdevctl created > b) foreign > 2) defined > a) automatic start-up > b) manual start-up > > I was using persistent for 2b), but that's probably not a good name > because devices can still be stopped, so they're not really > persistently available even in this class. NB, for terminology when libvirt calls something "persistent" it just means that there's a configuration file recorded on disk, thus when you stop the thing, you can still query its config & restart it from that same config later. The best solution for libvirt would be to cope with all 4 of those classes. 1b is the least important for us, so not the end of the world if it was missing. > > > To my mind there shouldn't really need to be a difference between > > > transient mdevs created by mdevctrl and mdevs created by an user > > > directly using sysfs. Both are mdevs on the running system with > > > no config file that you have to enumerate by looking at sysfs. > > > This ties back to my belief that we shouldn't need to have any > > > config on disk for a transient mdev, just discover them all > > > dynamically when required. > > > > So mdevctl can potentially interact with any mdev device on the system, > > it just has to be instructed by a user or software to do so? I think we > > can work with that. > > Some TBDs around systemd/init support for transient devices and how > transient devices can be promoted to defined. For instance if a > vfio-ap device requires matrix programming after instantiation, can we > glean that programming from sysfs or is there metadata irrecoverably > lost if no config file is created for a transient device? This would > also imply that a 1b) foreign device could not be promoted to 2x) > defined device. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
