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

[Pierre Morel]

On 2020-07-02 15:03, Pierre Morel wrote:
> On 2020-06-29 18:05, Cornelia Huck wrote:
> > On Mon, 29 Jun 2020 11:57:14 -0400
> > "Michael S. Tsirkin" <mst@xxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > > > Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
> > > > Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> > > > ---
> > > > Â arch/s390/mm/init.cÂÂÂÂ |Â 6 ++++++
> > > > Â drivers/virtio/virtio.c | 22 ++++++++++++++++++++++
> > > >  include/linux/virtio.h | 2 ++
> > > > Â 3 files changed, 30 insertions(+)
> >
> > > > @@ -179,6 +194,13 @@ int virtio_finalize_features(struct 
> > > > virtio_device *dev)
> > > > ÂÂÂÂÂ if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
> > > > ÂÂÂÂÂÂÂÂÂ return 0;
> > > > +ÂÂÂ if (arch_needs_virtio_iommu_platform(dev) &&
> > > > +ÂÂÂÂÂÂÂ !virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
> > > > +ÂÂÂÂÂÂÂ dev_warn(&dev->dev,
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂ "virtio: device must provide VIRTIO_F_IOMMU_PLATFORM\n");
> > > > +ÂÂÂÂÂÂÂ return -ENODEV;
> > > > +ÂÂÂ }
> > > > +
> > > > ÂÂÂÂÂ virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
> > > > ÂÂÂÂÂ status = dev->config->get_status(dev);
> > > > ÂÂÂÂÂ 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.


would be something like:

-       if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
-               return 0;
+       if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
+               ret = arch_accept_virtio_features(dev);
+               if (ret)
+                       dev_warn(&dev->dev,
+                                "virtio: device must provide 
VIRTIO_F_VERSION_1\n");
+               return ret;
+       }


just a thought on the function name:
It becomes more general than just IOMMU_PLATFORM related.

What do you think of:

arch_accept_virtio_features()

?

Regards,
Pierre


--
Pierre Morel
IBM Lab Boeblingen