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Tsirkin" Subject: RE: (proposal) RE: [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs Thread-Topic: (proposal) RE: [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs Thread-Index: AdagceQQLvqwjRCrQOaq1hZ7MgDUUAAt0sKAACmGxcAAPBsbAAAARpcAAAOFkAAAAwCSQADzeAMAAANpJxAAAu+FgAAAOEXwAAlgCoAAABHqwAAASzgAAAATKiA= Date: Tue, 20 Oct 2020 14:09:44 +0000 Message-ID: References: <9c10b681-dd7e-2e66-d501-7fcc3ff1207a@redhat.com> <21a66a96-4263-7df2-3bec-320e6f38a9de@redhat.com> <6e478a9e-2051-c0cd-b6fd-624ff5ef0f53@redhat.com> <20201020135439.GH6219@nvidia.com> <20201020140504.GJ6219@nvidia.com> In-Reply-To: <20201020140504.GJ6219@nvidia.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-reaction: no-action dlp-version: 11.5.1.3 dlp-product: dlpe-windows authentication-results: nvidia.com; dkim=none (message not signed) header.d=none;nvidia.com; dmarc=none action=none header.from=intel.com; x-originating-ip: [221.220.190.251] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: e1cd4281-6433-40ef-a2f6-08d87501cb99 x-ms-traffictypediagnostic: DM6PR11MB3865: x-ld-processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:6790; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: 5qbM8Rj5I/muQa3I6kUjt4nLxaxrWpZK/pSrEIxI83v2taX/mV/P+hwtMy4FWJaj1LQrFcfIOippBWl8jmD2to73shcSSnvGOPQAlYYLP4prg+ITv25yeICannsrIPhUC7WA+F9dbAxZkzn7Ew3DGaK2EwfnL+caanotFjbbuC/wJo4bO3vfT9zKTF9i8/JnHKKG47NLEbCOmKFJewHRonzD/AvkKN2hD+sURhtFf9OzoA4pn7QUvqoF7RIGsQy8g+vFTTu6YmZwRGeAY0xuQ6p20J0Ljn+RqAcH+0rntJoVxodFh8aSxcDzNGOBBMKG3sGuAhv0bDqGJs92KOrvFA== x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DM5PR11MB1435.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(396003)(346002)(136003)(366004)(376002)(39860400002)(186003)(478600001)(8676002)(7696005)(9686003)(4326008)(6916009)(8936002)(26005)(33656002)(6506007)(66946007)(7416002)(86362001)(66556008)(2906002)(5660300002)(66476007)(66446008)(71200400001)(52536014)(64756008)(55016002)(316002)(53546011)(54906003)(76116006);DIR:OUT;SFP:1102; x-ms-exchange-antispam-messagedata: 9Q7lWV47h8Xmt+0WUxP9diLxsPEuXBdq8ypivwCR27HuIOq8rqrrqP8hi5HwJq5wkgy7VOvfg3rSDCaghPzpUiNF9BXMyQr59gOCPyjxW/5MceW75vumdWxWXIxEjTLAyI6QVCoc0MA1vBmYhtTx2bCFxq95GEU1ypFFHPg59DMMZaOZ48WttNxaVV0OUR8H1qe/SUUe3+twuJlb/7Rq3z/kFW0wjRfkbEf+n/tnPnOlgImP86F6oSd+6p3tK7D4St8IqMJETKq5McxeOAykD0c1v3okVduSufRdF70DYj7Q0l9IJx+jscoagn9noyzGWKfi4p7xX0scrsCOsq/scNuujnruj1JdCrYzFxbVon5ZtxMhRd6JTIc8VeMyzPScf/5DW3eldrFdqRtldHoR0JJggo5rDGlFX0gIiQndH61RZ7FC5HmBhcrIyC9vc+XHvKtOD5kZQmkf1WEsOHG8b3ecqTzCJRAXo9NdS6908lZlR2+x/9THOLfuQoSst//yn2ED55eVV49eu/6Mu3IlQRPc6AYRp283ZViUl1IseltifMsBrSIjYNQ2ZyezaMkCZFaF4jpVwQc14/MlWxTaq6XOa3b3/p8ZKtYO9738MZTkadq3riezSdB+LXB2n+0mg+/j+hAyK6jiVLXvZhYBKQ== Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DM5PR11MB1435.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: e1cd4281-6433-40ef-a2f6-08d87501cb99 X-MS-Exchange-CrossTenant-originalarrivaltime: 20 Oct 2020 14:09:44.2886 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: DSuTEzRHh1gUorWvx0w4JxB5sy8jDolPEy2XIgswC9pzVOyFd4Y9Oiq/FDjdede2KOi88HQMRwZB5qmH2BSUNA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR11MB3865 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org > From: Jason Gunthorpe > Sent: Tuesday, October 20, 2020 10:05 PM > To: Liu, Yi L >=20 > On Tue, Oct 20, 2020 at 02:00:31PM +0000, Liu, Yi L wrote: > > > From: Jason Gunthorpe > > > Sent: Tuesday, October 20, 2020 9:55 PM > > > > > > On Tue, Oct 20, 2020 at 09:40:14AM +0000, Liu, Yi L wrote: > > > > > > > > See previous discussion with Kevin. If I understand correctly, > > > > > you expect a > > > shared > > > > > L2 table if vDPA and VFIO device are using the same PASID. > > > > > > > > L2 table sharing is not mandatory. The mapping is the same, but no > > > > need to assume L2 tables are shared. Especially for VFIO/vDPA > > > > devices. Even within a passthru framework, like VFIO, if the > > > > attributes of backend IOMMU are not the same, the L2 page table are= not > shared, but the mapping is the same. > > > > > > I think not being able to share the PASID shows exactly why this > > > VFIO centric approach is bad. > > > > no, I didn't say PASID is not sharable. My point is sharing L2 page > > table is not mandatory. >=20 > IMHO a PASID should be 1:1 with a page table, what does it even mean to s= hare > a PASID but have different page tables? PASID is actually 1:1 with an address space. Not really needs to be 1:1 wit= h page table. :-) Regards, Yi Liu > Jason