On Thu, Jul 8, 2021 at 4:28 PM Jonathon Jongsma <jjongsma@xxxxxxxxxx> wrote: > > On Thu, Jul 8, 2021 at 3:47 PM Boris Fiuczynski <fiuczy@xxxxxxxxxxxxx> wrote: > > > > On 7/6/21 9:05 PM, Jonathon Jongsma wrote: > > > Unfortunately, mdevctl supports defining more than one mdev with the > > > same UUID as long as they have different parent devices. So we can't use > > > the UUID alone as a way to uniquely identify these node devices. Append > > > the parent name to ensure uniqueness. For example: > > > > > > Before: mdev_88a6b868_46bd_4015_8e5b_26107f82da38 > > > After: mdev_88a6b868_46bd_4015_8e5b_26107f82da38_0000_00_02_0 > > > > > > Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1979440 > > > > > > Signed-off-by: Jonathon Jongsma <jjongsma@xxxxxxxxxx> > > > --- > > > QUESTION: Is there any expectation of stability in these device names? I'm not > > > sure to what extent these changes might affect users. Given that support for > > > persistent mdevs is fairly new, there are likely not many users yet. > > > > People using mdevs with libvirt will certainly be impacted by this but I > > am not sure how many there are. > > > > I am wondering if the scenario is even useful since I just tried it out > > and starting the second mdev with the uuid fails. > > > > # mdevctl list -d > > e60cef97-3f6b-485e-ac46-0520f9f66ac2 0.0.0033 vfio_ccw-io manual (active) > > e60cef97-3f6b-485e-ac46-0520f9f66ac2 0.0.0034 vfio_ccw-io manual > > # mdevctl start -u e60cef97-3f6b-485e-ac46-0520f9f66ac2 -p 0.0.0034 > > Device exists under different parent > > > > Yes, it is expected that you can only have a single device with the > same UUID active at one time. I asked Alex about why mdevctl supported > this feature, and he said he thought it was so that a single VM xml > could run with different mdevs depending on which one was > instantiated. I'm not sure that anybody is actually using this > "feature", but libvirt still has to deal with the possibility that we > could get such a config from mdevctl. > > Jonathon By the way, I'm self-NACKing this patch. I have a more comprehensive patch series coming soon. Jonathon
