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

Cornelia Huck
2020-06-16T12:18:07Z

On Tue, 16 Jun 2020 13:57:26 +0200
Halil Pasic <pasic@linux.ibm.com> wrote:

> On Tue, 16 Jun 2020 12:52:50 +0200
> Pierre Morel <pmorel@linux.ibm.com> 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.