Re: [PATCH v3 1/1] s390: virtio: let arch accept devices without IOMMU feature

Pierre Morel
2020-07-02T13:05:35Z

On 2020-06-29 18:05, Cornelia Huck wrote:
> On Mon, 29 Jun 2020 11:57:14 -0400
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
>> On Wed, Jun 17, 2020 at 12:43:57PM +0200, Pierre Morel wrote:
>>> An architecture protecting the guest memory against unauthorized host
>>> access may want to enforce VIRTIO I/O device protection through the
>>> use of VIRTIO_F_IOMMU_PLATFORM.
>>>
>>> Let's give a chance to the architecture to accept or not devices
>>> without VIRTIO_F_IOMMU_PLATFORM.
>>>
>>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>>> Acked-by: Jason Wang <jasowang@redhat.com>
>>> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>> ---
>>> arch/s390/mm/init.c | 6 ++++++
>>> drivers/virtio/virtio.c | 22 ++++++++++++++++++++++
>>> include/linux/virtio.h | 2 ++
>>> 3 files changed, 30 insertions(+)
>
>>> @@ -179,6 +194,13 @@ int virtio_finalize_features(struct virtio_device *dev)
>>> if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
>>> return 0;
>>>
>>> + if (arch_needs_virtio_iommu_platform(dev) &&
>>> + !virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
>>> + dev_warn(&dev->dev,
>>> + "virtio: device must provide VIRTIO_F_IOMMU_PLATFORM\n");
>>> + return -ENODEV;
>>> + }
>>> +
>>> virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
>>> status = dev->config->get_status(dev);
>>> if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
>>
>> Well don't you need to check it *before* VIRTIO_F_VERSION_1, not after?
>
> But it's only available with VERSION_1 anyway, isn't it? So it probably
> also needs to fail when this feature is needed if VERSION_1 has not been
> negotiated, I think.
>

Yes, clearly, I will add this.

Thanks,
Pierre

--
Pierre Morel
IBM Lab Boeblingen