linux-kernel - Re: [PATCH v3 08/17] iommufd: IOMMU_HWPT

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Date:   Fri, 28 Jul 2023 12:10:14 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Yi Liu <yi.l.liu@...el.com>, Jason Gunthorpe <jgg@...dia.com>
CC:     <joro@...tes.org>, <alex.williamson@...hat.com>,
        <kevin.tian@...el.com>, <robin.murphy@....com>,
        <baolu.lu@...ux.intel.com>, <cohuck@...hat.com>,
        <eric.auger@...hat.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>, <zhenzhong.duan@...el.com>
Subject: Re: [PATCH v3 08/17] iommufd: IOMMU_HWPT_ALLOC allocation with user
 data

On Fri, Jul 28, 2023 at 02:55:57PM -0300, Jason Gunthorpe wrote:
> On Mon, Jul 24, 2023 at 04:03:57AM -0700, Yi Liu wrote:
> 
> > +	switch (pt_obj->type) {
> > +	case IOMMUFD_OBJ_IOAS:
> > +		ioas = container_of(pt_obj, struct iommufd_ioas, obj);
> > +		break;
> > +	case IOMMUFD_OBJ_HW_PAGETABLE:
> > +		/* pt_id points HWPT only when hwpt_type is !IOMMU_HWPT_TYPE_DEFAULT */
> > +		if (cmd->hwpt_type == IOMMU_HWPT_TYPE_DEFAULT) {
> > +			rc = -EINVAL;
> > +			goto out_put_pt;
> > +		}
> > +
> > +		parent = container_of(pt_obj, struct iommufd_hw_pagetable, obj);
> > +		/*
> > +		 * Cannot allocate user-managed hwpt linking to auto_created
> > +		 * hwpt. If the parent hwpt is already a user-managed hwpt,
> > +		 * don't allocate another user-managed hwpt linking to it.
> > +		 */
> > +		if (parent->auto_domain || parent->parent) {
> > +			rc = -EINVAL;
> > +			goto out_put_pt;
> > +		}
> > +		ioas = parent->ioas;
> 
> Why do we set ioas here? I would think it should be NULL.
> 
> I think it is looking like a mistake to try and re-use
> iommufd_hw_pagetable_alloc() directly for the nested case. It should
> not have a IOAS argument, it should not do enforce_cc, or iopt_*
> functions
> 
> So must of the function is removed. Probably better to make a new
> ioas-less function for the nesting case.

OK.

@Yi, along with the PATCH-6 (IOMMU_RESV_SW_MSI), I will rework
on this -- mainly breaking up NESTED hwpt with IOAS.

Thanks
Nic