Re: [PATCH v2 1/1] s390: vfio_ap: link the vfio_ap devices to the vfio_ap bus subsystem

[Pierre Morel]

On 21/02/2019 13:35, Christian Borntraeger wrote:
> On 21.02.2019 13:10, Pierre Morel wrote:
> > On 20/02/2019 13:51, Halil Pasic wrote:
> > > On Wed, 20 Feb 2019 10:27:31 +0100
> > > Cornelia Huck <cohuck@xxxxxxxxxx> wrote:
> > >
> > > > On Tue, 19 Feb 2019 22:31:17 +0100
> > > > Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
> > > >
> > > > > On 19/02/2019 19:52, Tony Krowiak wrote:
> > > > > > On 2/18/19 1:08 PM, Pierre Morel wrote:
> > > > > > > Libudev relies on having a subsystem link for non-root devices. To
> >
> > ...snip...
> >
> > > > > > > +
> > > > > > > +static struct device_driver matrix_driver = {
> > > > > > > +ÂÂÂ .name = "vfio_ap",
> > > > > >
> > > > > > This is the same name used for the original device driver. I think
> > > > > > this driver ought to have a different name to avoid confusion.
> > > > > > How about vfio_ap_matrix or some other name to differentiate the
> > > > > > two.
> > > > >
> > > > > I would like too, but changing this will change the path to the mediated
> > > > > device supported type.
> > > >
> > > > Yes, we don't want to change that.
> > >
> > > Nod.
> >
> > However if I cannot change the driver name, I can change the bus name to matrix.
> > At least one less "vfio_ap" name
> >
> > > > > >    
> > > > > > > +ÂÂÂ .bus = &matrix_bus,
> > > > > > > +ÂÂÂ .probe = matrix_probe,
> > > > > >
> > > > > > I would add:
> > > > > >  Â ÂÂÂÂ.suppress_bind_attrs = true;
> > > > > >
> > > > > > This will remove the sysfs bind/unbind interfaces. Since there is only
> > > > > > one matrix device and it's lifecycle is controlled herein, there is no
> > > > > > sense in allowing a root user to bind/unbind it.
> > > > > >     
> > > > >
> > > > > OTOH bind/unbind has no impact.
> > > > > If no one else ask for this I will not change what has already been
> > > > > reviewed by Conny and Christian.
> > > >
> > > > As we only have one driver, it does not really make sense anyway.
> > >
> > > I see this as a reason to suppress_bind_attrs. It is much easier than to
> > > think about what should happen when one unbinds the matrix device from
> > > the vfio_ap driver on the vfio_ap bus. With the code as is it seems to
> > > just keep working as if nothing happened.
> > > And /sys/devices/vfio_ap/matrix/mdev_supported_types/ referencing the
> > > name of the driver that is already gone sounds a bit weird.
> > >
> > > Regards,
> > > Halil
> >
> > If there is no objection I will do this,
> > It seems more logical to me too.
>
> Go ahead and send this as v3?

OK
CC stable ?


--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany