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Wed, 12 Aug 2020 03:35:39 +0000 Received: from MWHPR11MB1645.namprd11.prod.outlook.com ([fe80::6dfe:feb8:25f1:ac9c]) by MWHPR11MB1645.namprd11.prod.outlook.com ([fe80::6dfe:feb8:25f1:ac9c%7]) with mapi id 15.20.3261.025; Wed, 12 Aug 2020 03:35:39 +0000 From: "Tian, Kevin" To: Alex Williamson CC: Jason Gunthorpe , "Jiang, Dave" , "vkoul@kernel.org" , "Dey, Megha" , "maz@kernel.org" , "bhelgaas@google.com" , "rafael@kernel.org" , "gregkh@linuxfoundation.org" , "tglx@linutronix.de" , "hpa@zytor.com" , "Pan, Jacob jun" , "Raj, Ashok" , "Liu, Yi L" , "Lu, Baolu" , "Kumar, Sanjay K" , "Luck, Tony" , "Lin, Jing" , "Williams, Dan J" , "kwankhede@nvidia.com" , "eric.auger@redhat.com" , "parav@mellanox.com" , "Hansen, Dave" , "netanelg@mellanox.com" , "shahafs@mellanox.com" , "yan.y.zhao@linux.intel.com" , "pbonzini@redhat.com" , "Ortiz, Samuel" , "Hossain, Mona" , "dmaengine@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "x86@kernel.org" , "linux-pci@vger.kernel.org" , "kvm@vger.kernel.org" Subject: RE: [PATCH RFC v2 00/18] Add VFIO mediated device support and DEV-MSI support for the idxd driver Thread-Topic: [PATCH RFC v2 00/18] Add VFIO mediated device support and DEV-MSI support for the idxd driver Thread-Index: AQHWX3hut2htBlMVB0qfW0Pa+gZbC6kSPbuAgABwW8CAAzMrAIAUgAoAgAJJ4oCABDO9YIACZAIAgACUIGCAAAy5AIAAD1+w Date: Wed, 12 Aug 2020 03:35:39 +0000 Message-ID: References: <159534667974.28840.2045034360240786644.stgit@djiang5-desk3.ch.intel.com> <20200721164527.GD2021248@mellanox.com> <20200724001930.GS2021248@mellanox.com> <20200805192258.5ee7a05b@x1.home> <20200807121955.GS16789@nvidia.com> <20200811110036.7d337837@x1.home> <20200811203618.41aa6031@x1.home> In-Reply-To: <20200811203618.41aa6031@x1.home> 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: redhat.com; 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x-ms-exchange-antispam-messagedata: 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 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: MWHPR11MB1645.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3f2dc017-2e19-4e60-b1bf-08d83e70c870 X-MS-Exchange-CrossTenant-originalarrivaltime: 12 Aug 2020 03:35:39.2113 (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: Z4YDs/1+15MIllGJcXucg9I+e6sLBICd1kR6SQG3Y9yQvMi4ZbyNdbnDeXdHwahj6TvZ2CTe5wSI5a92ci0Y+g== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR11MB1647 X-OriginatorOrg: intel.com Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org > From: Alex Williamson > Sent: Wednesday, August 12, 2020 10:36 AM > On Wed, 12 Aug 2020 01:58:00 +0000 > "Tian, Kevin" wrote: >=20 > > > > > > I'll also remind folks that LPC is coming up in just a couple short > > > weeks and this might be something we should discuss (virtually) > > > in-person. uconf CfPs are currently open. Thanks, > > > > > > > Yes, LPC is a good place to reach consensus. btw I saw there is > > already one VFIO topic called "device assignment/sub-assignment". > > Do you think whether this can be covered under that topic, or > > makes more sense to be a new one? >=20 > All the things listed in the CFP are only potential topics to get ideas > flowing, there is currently no proposal to talk about sub-assignment. > I'd suggest submitting separate topics for each and if we run into time > constraints we can ask that they might be combined together. Thanks, >=20 Done. -- title: Criteria of using VFIO mdev (vs. userspace DMA) Content: VFIO mdev provides a framework for subdevice assignment and reuses=20 existing VFIO uAPI to handle common passthrough-related requirements.=20 However, subdevice (e.g. ADI defined in Intel Scalable IOV) might not be=20 a PCI endpoint (e.g. just a work queue), thus requires some degree of=20 emulation/mediation in kernel to fit into VFIO device API. Then there is=20 a concern on putting emulation in kernel and how to judge abuse of=20 mdev framework by simply using it as an easy path to hook into=20 virtualization stack. An associated open is about differentiating mdev=20 from userspace DMA framework (such as uacce), and whether building=20 passthrough features on top of userspace DMA framework is a better=20 choice than using mdev.=20 Thanks Kevin