[Intel-gfx] [PATCH v6 21/24] vfio: Add VFIO_DEVICE_BIND_IOMMUFD

[Liu, Yi L]

> From: Tian, Kevin <kevin.tian at intel.com>
> Sent: Friday, March 10, 2023 6:07 PM
> 
> > From: Liu, Yi L <yi.l.liu at intel.com>
> > Sent: Friday, March 10, 2023 5:58 PM
> >
> > > From: Tian, Kevin <kevin.tian at intel.com>
> > > Sent: Friday, March 10, 2023 5:02 PM
> > >
> > > > From: Liu, Yi L <yi.l.liu at intel.com>
> > > > 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.
> 
> correct.
> 
> >
> > 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
> 
> this makes sense.

Just have one more think. vfio_device_is_noiommu() is already able
to cover above vfio_device_group_allow_noiommu(), just needs
to make it work when !VFIO_GROUP. In the group code, group->type
== VFIO_NO_IOMMU means vfio_noiommu==true. So no need to
check it. While in the case !VFIO_GROUP, needs to check it. So the
code is as below. I can use vfio_device_is_noiommu() in cdev path.

# 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;
}
#endif