> From: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Sent: Friday, August 27, 2021 6:47 AM
>
> On Thu, 26 Aug 2021 15:34:15 +0200
> Christoph Hellwig <hch@xxxxxx> wrote:
> > +#ifdef CONFIG_VFIO_NOIOMMU
> > +static struct vfio_group *vfio_noiommu_group_alloc(struct device *dev)
> > {
> > struct iommu_group *iommu_group;
> > struct vfio_group *group;
> > + int ret;
> > +
> > + iommu_group = iommu_group_alloc();
> > + if (IS_ERR(iommu_group))
> > + return ERR_CAST(iommu_group);
> >
> > - iommu_group = vfio_iommu_group_get(dev);
> > + iommu_group_set_name(iommu_group, "vfio-noiommu");
> > + iommu_group_set_iommudata(iommu_group, &noiommu, NULL);
> > + ret = iommu_group_add_device(iommu_group, dev);
> > + if (ret)
> > + goto out_put_group;
> > +
> > + group = vfio_create_group(iommu_group);
> > + if (IS_ERR(group)) {
> > + ret = PTR_ERR(group);
> > + goto out_remove_device;
> > + }
> > +
> > + return group;
> > +
> > +out_remove_device:
> > + iommu_group_remove_device(dev);
> > +out_put_group:
> > + iommu_group_put(iommu_group);
> > + return ERR_PTR(ret);
> > +}
> > +#endif
> > +
> > +static struct vfio_group *vfio_group_find_or_alloc(struct device *dev)
> > +{
> > + struct iommu_group *iommu_group;
> > + struct vfio_group *group;
> > +
> > + iommu_group = iommu_group_get(dev);
> > +#ifdef CONFIG_VFIO_NOIOMMU
> > + if (!iommu_group && noiommu && !iommu_present(dev->bus)) {
> > + /*
> > + * With noiommu enabled, create an IOMMU group for
> devices that
> > + * don't already have one and don't have an iommu_ops on
> their
> > + * bus. Taint the kernel because we're about to give a DMA
> > + * capable device to a user without IOMMU protection.
> > + */
> > + group = vfio_noiommu_group_alloc(dev);
> > + if (group) {
> > + add_taint(TAINT_USER, LOCKDEP_STILL_OK);
> > + dev_warn(dev, "Adding kernel taint for vfio-
> noiommu group on device\n");
> > + }
>
> Perhaps what Kevin was pointing out here in the previous version,
> vfio_noiommu_group_alloc() returns a pointer, so this should test
> !IS_ERR(group). Thanks,
>
yes, that is what I meant.
