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

[Pierre Morel]

On 2020-06-29 15:44, Cornelia Huck wrote:
> On Mon, 29 Jun 2020 15:14:04 +0200
> Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
>
> > On 2020-06-19 11:20, Cornelia Huck wrote:
> > > On Thu, 18 Jun 2020 00:29:56 +0200
> > > Halil Pasic <pasic@xxxxxxxxxxxxx> wrote:
> > >    
> > > > On Wed, 17 Jun 2020 12:43:57 +0200
> > > > Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
>
> > > > > @@ -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");
>
> [Side note: wasn't there a patch renaming this bit on the list? I think
> this name is only kept for userspace compat.]

Sorry, I do not understand what you expect from me.
On which mailing list you think there is a patch on?

> > > > I'm not sure, divulging the current Linux name of this feature bit is a
> > > > good idea, but if everybody else is fine with this, I don't care that
> > >
> > > Not sure if that feature name will ever change, as it is exported in
> > > headers. At most, we might want to add the new ACCESS_PLATFORM define
> > > and keep the old one, but that would still mean some churn.
> > >    
> > > > much. An alternative would be:
> > > > "virtio: device falsely claims to have full access to the memory,
> > > > aborting the device"
> > >
> > > "virtio: device does not work with limited memory access" ?
> > >
> > > But no issue with keeping the current message.
> > >    
> >
> > If it is OK, I would like to specify that the arch is responsible to
> > accept or not the device.
> > The reason why the device is not accepted without IOMMU_PLATFORM is arch
> > specific.
>
> Hm, I'd think the reason is always the same (the device cannot access
> the memory directly), just the way to figure out whether that is the
> case or not is arch-specific, as with so many other things. No real
> need to go into detail here, I think.

As you like, so I rename the subject to:
"virtio: device does not work with limited memory access"

Regards,

Pierre


--
Pierre Morel
IBM Lab Boeblingen