Re: [PATCH v6 21/24] vfio: Add VFIO_DEVICE_BIND_IOMMUFD

Jason Gunthorpe
2023-03-20T17:22:09Z

On Mon, Mar 20, 2023 at 10:31:53PM +0800, Yi Liu wrote:
> On 2023/3/20 22:09, Jason Gunthorpe wrote:
> > On Wed, Mar 15, 2023 at 04:40:19AM +0000, Liu, Yi L wrote:
> >
> > > # if IS_ENABLED(CONFIG_VFIO_GROUP)
> > > static inline bool vfio_device_is_noiommu(struct vfio_device *vdev)
> > > {
> > > return IS_ENABLED(CONFIG_VFIO_NOIOMMU) &&
> > > vdev->group->type == VFIO_NO_IOMMU;
> > > }
> > > #else
> > > static inline bool vfio_device_is_noiommu(struct vfio_device *vdev)
> > > {
> > > struct iommu_group *iommu_group;
> > >
> > > if (!IS_ENABLED(CONFIG_VFIO_NOIOMMU) || !vfio_noiommu)
> > > return -EINVAL;
> > >
> > > iommu_group = iommu_group_get(vdev->dev);
> > > if (iommu_group)
> > > iommu_group_put(iommu_group);
> > >
> > > return !iommu_group;
> >
> > If we don't have VFIO_GROUP then no-iommu is signaled by a NULL
> > iommu_ctx pointer in the vdev, don't mess with groups
>
> yes, NULL iommufd_ctx pointer would be set in vdev and passed to the
> vfio_device_open(). But here, we want to use this helper to check if
> user can use noiommu mode. This is before calling vfio_device_open().
> e.g. if the device is protected by iommu, then user cannot use noiommu
> mode on it.

Why not allow it?

If the admin has enabled this mode we may as well let it be used.

You explicitly ask for no-iommu mode by passing -1 for the iommufd
parameter. If the module parameter says it is allowed then that is all
you need.

Jason