Re: [libvirt] mdevctl: A shoestring mediated device management and persistence utility
On Fri, 24 May 2019 12:11:06 +0200
Cornelia Huck <cohuck(a)redhat.com> wrote:
On Thu, 23 May 2019 17:20:01 -0600
Alex Williamson <alex.williamson(a)redhat.com> wrote:
> Hi,
>
[..]
>
> 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.
Sorry for being late...
I guess for vfio-ccw one needs to make sure that the ccw device is bound
to the vfio-ccw driver first, and only after that can one use
create-mdev to create the mdev on top of the subchannel.
So to make this work persistently (survive a reboot) one would need to
take care of the subchannel getting bound to the right vfio_ccw driver
before mdevctl is called. Right?
BTW how does this concurrence situation between the drivers io_subchannel
and vfio_ccw work? Especially if both are build in?
>
> 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.
>
+1
@Alex: I'm curious what is the big management picture for non-auto looks
like.
Regards,
Halil
[..]