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

["Liu, Yi L" <yi.l.liu@xxxxxxxxx>]

> From: Tian, Kevin <kevin.tian@xxxxxxxxx>
> Sent: Friday, March 10, 2023 5:02 PM
> 
> > From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> > Sent: Wednesday, March 8, 2023 9:29 PM
> > +
> > +static int vfio_device_cdev_probe_noiommu(struct vfio_device *device)
> > +{
> > +	struct iommu_group *iommu_group;
> > +	int ret = 0;
> > +
> > +	if (!IS_ENABLED(CONFIG_VFIO_NOIOMMU) || !vfio_noiommu)
> > +		return -EINVAL;
> > +
> > +	if (!capable(CAP_SYS_RAWIO))
> > +		return -EPERM;
> > +
> > +	iommu_group = iommu_group_get(device->dev);
> > +	if (!iommu_group)
> > +		return 0;
> > +
> > +	/*
> > +	 * We cannot support noiommu mode for devices that are
> protected
> > +	 * by IOMMU.  So check the iommu_group, if it is a no-iommu group
> > +	 * created by VFIO, we support. If not, we refuse.
> > +	 */
> > +	if
> (!vfio_group_find_noiommu_group_from_iommu(iommu_group))
> > +		ret = -EINVAL;
> > +	iommu_group_put(iommu_group);
> > +	return ret;
> 
> can check whether group->name == "vfio-noiommu"?

But VFIO names it to be "vfio-noiommu" for both VFIO_EMULATED_IOMMU
and VFIO_NO_IOMMU. And we don't support no-iommu mode for emulated
devices since VFIO_MAP/UNMAP, pin_page(), dam_rw() won't work in the
no-iommu mode.

So maybe something like below in drivers/vfio/vfio.h. It can be used
to replace the code from iommu_group_get() to
vfio_group_find_noiommu_group_from_iommu() In my patch.

#if IS_ENABLED(CONFIG_VFIO_GROUP)
static inline bool vfio_device_group_allow_noiommu(struct vfio_device *device)
{
	lockdep_assert_held(&device->dev_set->lock);

	return device->group->type == VFIO_NO_IOMMU;
}
#else
static inline bool vfio_device_group_allow_noiommu(struct vfio_device *device)
{
	struct iommu_group *iommu_group;

	lockdep_assert_held(&device->dev_set->lock);

	iommu_group = iommu_group_get(device->dev);
	if (iommu_group)
		iommu_group_put(iommu_group);

	return !iommu_group;
}
#endif