linux-kernel - Re: [PATCH 04/12] iommufd: Pass parent hwpt and user_data to iommufd_hw_pagetable

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Date:   Fri, 10 Mar 2023 13:49:07 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     Yi Liu <yi.l.liu@...el.com>, joro@...tes.org,
        alex.williamson@...hat.com, kevin.tian@...el.com,
        robin.murphy@....com, cohuck@...hat.com, eric.auger@...hat.com,
        nicolinc@...dia.com, kvm@...r.kernel.org, mjrosato@...ux.ibm.com,
        chao.p.peng@...ux.intel.com, yi.y.sun@...ux.intel.com,
        peterx@...hat.com, jasowang@...hat.com,
        shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
        suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 04/12] iommufd: Pass parent hwpt and user_data to
 iommufd_hw_pagetable_alloc()

On Fri, Mar 10, 2023 at 10:10:56AM +0800, Baolu Lu wrote:
> > @@ -54,14 +58,20 @@ int iommufd_hw_pagetable_enforce_cc(struct iommufd_hw_pagetable *hwpt)
> >    */
> >   struct iommufd_hw_pagetable *
> >   iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
> > -			   struct iommufd_device *idev, bool immediate_attach)
> > +			   struct iommufd_device *idev,
> > +			   struct iommufd_hw_pagetable *parent,
> > +			   void *user_data, bool immediate_attach)
> >   {
> >   	const struct iommu_ops *ops = dev_iommu_ops(idev->dev);
> > +	struct iommu_domain *parent_domain = NULL;
> >   	struct iommufd_hw_pagetable *hwpt;
> >   	int rc;
> >   	lockdep_assert_held(&ioas->mutex);
> > +	if (parent && !ops->domain_alloc_user)
> > +		return ERR_PTR(-EOPNOTSUPP);
> 
> My understanding here is that we are checking whether domain_alloc_user
> is required. It seems that as long as the caller inputs a valid
> user_data or parent, domain_alloc_user is required. If so,
> 
> 	if ((user_data || parent) && !ops->domain_alloc_user)
> 		return ERR_PTR(-EOPNOTSUPP);

Yes

Jason