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From: "Tian, Kevin" <kevin.tian@intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>, Suravee Suthikulpanit
	<suravee.suthikulpanit@amd.com>
CC: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"iommu@lists.linux.dev" <iommu@lists.linux.dev>, "joro@8bytes.org"
	<joro@8bytes.org>, "Liu, Yi L" <yi.l.liu@intel.com>, "nicolinc@nvidia.com"
	<nicolinc@nvidia.com>, "eric.auger@redhat.com" <eric.auger@redhat.com>,
	"vasant.hegde@amd.com" <vasant.hegde@amd.com>, "jon.grimm@amd.com"
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	"Dhaval.Giani@amd.com" <Dhaval.Giani@amd.com>, "pandoh@google.com"
	<pandoh@google.com>, "loganodell@google.com" <loganodell@google.com>
Subject: RE: [RFC PATCH 5/6] iommu/amd: Introduce helper functions to setup
 GCR3TRPMode
Thread-Topic: [RFC PATCH 5/6] iommu/amd: Introduce helper functions to setup
 GCR3TRPMode
Thread-Index: AQHaLRSghPqwSI/GWkO0t5FR0qd6ALCnPUSAgAK797A=
Date: Fri, 15 Dec 2023 07:39:43 +0000
Message-ID: <BN9PR11MB52765E5B6A22918FC9B438818C93A@BN9PR11MB5276.namprd11.prod.outlook.com>
References: <20231212160139.174229-1-suravee.suthikulpanit@amd.com>
 <20231212160139.174229-6-suravee.suthikulpanit@amd.com>
 <20231213135313.GE3259566@nvidia.com>
In-Reply-To: <20231213135313.GE3259566@nvidia.com>
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> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Wednesday, December 13, 2023 9:53 PM
>=20
> On Tue, Dec 12, 2023 at 10:01:38AM -0600, Suravee Suthikulpanit wrote:
> > +/*
> > + * For GCR3TRPMode, user-space provides GPA for the GCR3 Root Pointer
> Table.
> > + */
> > +int amd_iommu_set_gcr3tbl_trp(struct amd_iommu *iommu, struct
> pci_dev *pdev,
> > +			      u64 gcr3_tbl, u16 glx, u16 guest_paging_mode)
> > +{
> > +	struct iommu_dev_data *dev_data =3D dev_iommu_priv_get(&pdev-
> >dev);
> > +	struct dev_table_entry *dev_table =3D get_dev_table(iommu);
> > +	struct gcr3_tbl_info *gcr3_info =3D &dev_data->gcr3_info;
> > +	int devid =3D pci_dev_id(pdev);
> > +	u64 data0 =3D dev_table[devid].data[0];
> > +	u64 data1 =3D dev_table[devid].data[1];
> > +	u64 data2 =3D dev_table[devid].data[2];
> > +	u64 tmp;
>=20
> Like I said in my other email, this whole function is conceptually
> wrong - you can't read the DTE to learn the parent domain's
> contribution to the nesting DTE and you can't write to the DTE during
> allocation of a domain!
>=20

Agree. DTE is updated only at attach/detach. domain allocation should
involve things only about the domain itself.