Re: [PATCH v2 1/1] s390: virtio: let arch accept devices without IOMMU feature

[Pierre Morel]

On 2020-06-16 14:17, Cornelia Huck wrote:
> On Tue, 16 Jun 2020 13:57:26 +0200
> Halil Pasic <pasic@xxxxxxxxxxxxx> wrote:
>
> > On Tue, 16 Jun 2020 12:52:50 +0200
> > Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
> >
> > > > >    int virtio_finalize_features(struct virtio_device *dev)
> > > > >    {
> > > > >    	int ret = dev->config->finalize_features(dev);
> > > > > @@ -179,6 +184,10 @@ int virtio_finalize_features(struct virtio_device *dev)
> > > > >    	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
> > > > >    		return 0;
> > > > >    
> > > > > +	if (arch_needs_iommu_platform(dev) &&
> > > > > +		!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM))
> > > > > +		return -EIO;
> > > > > +
> > > >
> > > > Why EIO?
> > >
> > > Because I/O can not occur correctly?
> > > I am open to suggestions.
> >
> > We use -ENODEV if feature when the device rejects the features we
> > tried to negotiate (see virtio_finalize_features()) and -EINVAL when
> > the F_VERSION_1 and the virtio-ccw revision ain't coherent (in
> > virtio_ccw_finalize_features()). Any of those seems more fitting
> > that EIO to me. BTW does the error code itself matter in any way,
> > or is it just OK vs some error?
>
> If I haven't lost my way, we end up in the driver core probe failure
> handling; we probably should do -ENODEV if we just want probing to fail
> and -EINVAL or -EIO if we want the code to moan.

what about returning -ENODEV and add a dedicated warning here?

--
Pierre Morel
IBM Lab Boeblingen