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Thu, 5 Aug 2021 22:44:19 +0000 From: "Tian, Kevin" To: Jason Gunthorpe CC: David Gibson , "Alex Williamson (alex.williamson@redhat.com)" , "Jean-Philippe Brucker" , Jason Wang , "parav@mellanox.com" , "Enrico Weigelt, metux IT consult" , Paolo Bonzini , Shenming Lu , Joerg Roedel , Eric Auger , Jonathan Corbet , "Raj, Ashok" , "Liu, Yi L" , "Wu, Hao" , "Jiang, Dave" , Jacob Pan , Kirti Wankhede , "Robin Murphy" , "kvm@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "David Woodhouse" , LKML , "Lu Baolu" Subject: RE: [RFC v2] /dev/iommu uAPI proposal Thread-Topic: [RFC v2] /dev/iommu uAPI proposal Thread-Index: Add0lrMH87IsTsl5Rp6WN1oQU6kGMQNQxoYAAN4kDIAAfDtbgAB9mQaAABKIGhAAGkG/gAAXZR2A Date: Thu, 5 Aug 2021 22:44:19 +0000 Message-ID: References: <20210730145123.GW1721383@nvidia.com> <20210804140447.GH1721383@nvidia.com> <20210805112713.GN1721383@nvidia.com> In-Reply-To: <20210805112713.GN1721383@nvidia.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-version: 11.5.1.3 dlp-product: dlpe-windows dlp-reaction: no-action authentication-results: nvidia.com; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BN9PR11MB5433.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: b40bef67-1a30-45de-8194-08d958629000 X-MS-Exchange-CrossTenant-originalarrivaltime: 05 Aug 2021 22:44:19.3676 (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: rIGThFV5UB0+wHLuWLGXOTOoP0VnnkY1ObizsHWnuMwp6dE66h0suEIC4El3WP2iYVGCm0jydVxYDGgB9mYPBw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN6PR11MB1762 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Jason Gunthorpe > Sent: Thursday, August 5, 2021 7:27 PM >=20 > On Wed, Aug 04, 2021 at 10:59:21PM +0000, Tian, Kevin wrote: > > > From: Jason Gunthorpe > > > Sent: Wednesday, August 4, 2021 10:05 PM > > > > > > On Mon, Aug 02, 2021 at 02:49:44AM +0000, Tian, Kevin wrote: > > > > > > > Can you elaborate? IMO the user only cares about the label (device > cookie > > > > plus optional vPASID) which is generated by itself when doing the > attaching > > > > call, and expects this virtual label being used in various spots > (invalidation, > > > > page fault, etc.). How the system labels the traffic (the physical = RID or > RID+ > > > > PASID) should be completely invisible to userspace. > > > > > > I don't think that is true if the vIOMMU driver is also emulating > > > PASID. Presumably the same is true for other PASID-like schemes. > > > > > > > I'm getting even more confused with this comment. Isn't it the > > consensus from day one that physical PASID should not be exposed > > to userspace as doing so breaks live migration? >=20 > Uh, no? >=20 > > with PASID emulation vIOMMU only cares about vPASID instead of > > pPASID, and the uAPI only requires user to register vPASID instead > > of reporting pPASID back to userspace... >=20 > vPASID is only a feature of one device in existance, so we can't make > vPASID mandatory. >=20 sure. my point is just that if vPASID is being emulated there is no need of exposing pPASID to user space. Can you give a concrete example where pPASID must be exposed and how the user wants to use this information?=20 Thanks Kevin