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

[Michael S. Tsirkin]

On Sat, Feb 05, 2022 at 01:02:05AM +0100, Halil Pasic wrote:
> 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.

yes but you wrote about return after error_setg above.

> > 
> > > 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  
> >