RE: [PATCH 04/12] iommufd: Pass parent hwpt and user_data to iommufd_hw_pagetable_alloc()

[Tian, Kevin]

> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Monday, March 20, 2023 8:47 PM
> 
> On Fri, Mar 17, 2023 at 10:23:54AM +0000, Tian, Kevin wrote:
> > > From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> > > Sent: Thursday, March 9, 2023 4:09 PM
> > >
> > > +	/* It must be either NESTED or UNMANAGED, depending on
> > > parent_domain */
> > > +	if ((parent_domain && hwpt->domain->type !=
> > > IOMMU_DOMAIN_NESTED) ||
> > > +	    (!parent_domain && hwpt->domain->type !=
> > > IOMMU_DOMAIN_UNMANAGED))
> > > +		goto out_abort;
> > > +
> >
> > WARN_ON()
> 
> Wouldn't that be userspace triggerable? It gets to pick the hwpt used.
> 

The domain type is set by iommu driver instead of userspace. A sane
driver should pass above check, if it claims to support nested.