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

Pierre Morel
2020-06-16T13:41:37Z

On 2020-06-16 14:17, Cornelia Huck wrote:
> 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.
>

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

--
Pierre Morel
IBM Lab Boeblingen