Re: [PATCH v4 1/1] virtio: fix the condition for iommu_platform not supported

[Halil Pasic]

On Fri, 4 Feb 2022 08:05:25 -0500
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Thu, Feb 03, 2022 at 05:06:35PM +0100, Halil Pasic wrote:
> > On Wed,  2 Feb 2022 20:54:38 +0100
> > Halil Pasic <pasic@linux.ibm.com> wrote:
> >   
> > >      }
> > > @@ -82,9 +78,14 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, 
> > > Error **errp)
> > >          return;
> > >      }
> > >  
> > > +    vdev_has_iommu = virtio_host_has_feature(vdev, 
> > > VIRTIO_F_IOMMU_PLATFORM);
> > >      if (klass->get_dma_as != NULL && has_iommu) {
> > >          virtio_add_feature(&vdev->host_features, 
> > > VIRTIO_F_IOMMU_PLATFORM);
> > >          vdev->dma_as = klass->get_dma_as(qbus->parent);
> > > +        if (!vdev_has_iommu && vdev->dma_as != &address_space_memory) {
> > > +            error_setg(errp,
> > > +                       "iommu_platform=true is not supported by the 
> > > device");
> > > +        }  
> > 
> > I'm wondering, would it be wise to change the message? Since this is now
> > dependent on the VM/bus the device is plugged into the message might be a
> > little misleading: i.e. the very same device could work perfectly fine
> > with iommu_platform=true if the "surroundings" are different.
> > 
> > Maybe "the device has no IOMMU support (iommu_platform=true)" would be a
> > better option. On the other hand changing the message has its downsides
> > as well.  
> 
> I personally don't care much frankly.
> 
> > Also I realized that keeping the return after error_setg() might have
> > been a good idea for the case more logic is added at the end of the
> > function.  
> 
> OK so you are sending v5 with this change then?

As stated below, I would prefer to get this merged. If I change the
message, I guess I have to drop the r-b's and the I'm sure the if
somebody decides to add logic to the end of the function that person
will be careful enough.

> 
> > In any case I would like to address these, if necessary with a separate
> > patch. I don't want the fix to experience any further delays.
> > 
> > Regards,
> > Halil  
>