Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: B+NgqlJFdtmxKXxb0eZn5Bhs8ml2hG7G6nll+QnkbD6vjhtkckEKiV2QpZJq9xCmX9EVRDokza
 qgyP1Lb7AaiA==
IronPort-SDR: 2crRJvln5awoHIY3DB7DM7g/N/1WYmWlPhp2To+YzTItAVjoWav5hKhiMSZ5pck6qqZSuLMD06
 zWLfP/doGKQg==
From:   "Tian, Kevin" <kevin.tian@intel.com>
To:     Jason Gunthorpe <jgg@nvidia.com>
CC:     Jacob Pan <jacob.jun.pan@linux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        David Woodhouse <dwmw2@infradead.org>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        "cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
        Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        "Jean-Philippe Brucker" <jean-philippe@linaro.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Eric Auger <eric.auger@redhat.com>,
        "Jonathan Corbet" <corbet@lwn.net>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        "Liu, Yi L" <yi.l.liu@intel.com>, "Wu, Hao" <hao.wu@intel.com>,
        "Jiang, Dave" <dave.jiang@intel.com>,
        Jason Wang <jasowang@redhat.com>
Subject: RE: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation
 APIs
Thread-Topic: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and
 allocation APIs
Thread-Index: AQHXDZub0CDG82VGXUmLEYgvMuPs4KqKkLIAgACg94CAAC72gIAAD04AgAADogCAAErUgIAETQEAgAOaswCAB7C3gIAAhxQwgADYDACABFtkwA==
Date:   Fri, 2 Apr 2021 08:22:28 +0000
Message-ID: <MWHPR11MB1886CAD48AFC156BFC7C1D398C7A9@MWHPR11MB1886.namprd11.prod.outlook.com>
References: <20210318172234.3e8c34f7@jacob-builder> <YFR10eeDVf5ZHV5l@myrica>
 <20210319124645.GP2356281@nvidia.com> <YFSqDNJ5yagk4eO+@myrica>
 <20210319135432.GT2356281@nvidia.com> <20210319112221.5123b984@jacob-builder>
 <20210322120300.GU2356281@nvidia.com> <20210324120528.24d82dbd@jacob-builder>
 <20210329163147.GG2356281@nvidia.com>
 <MWHPR11MB188639EE54B48B0E1321C8198C7D9@MWHPR11MB1886.namprd11.prod.outlook.com>
 <20210330132830.GO2356281@nvidia.com>
In-Reply-To: <20210330132830.GO2356281@nvidia.com>
Accept-Language: en-US
Content-Language: en-US
dlp-version: 11.5.1.3
dlp-product: dlpe-windows
dlp-reaction: no-action
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: b5b7ba21-3f3e-487b-595f-08d8f5b07401
X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Apr 2021 08:22:28.1590
 (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: oLpuzb4KUwAeZqoKsatcHHvz8dewF6sMjtqP6y2UGhqKzbKou9uXhDoQd4NoQFd0CuHe6ey3DtANPAkNzkzNtg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR11MB1327
X-OriginatorOrg: intel.com
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Tuesday, March 30, 2021 9:29 PM
>=20
> >
> > First, userspace may use ioasid in a non-SVA scenario where ioasid is
> > bound to specific security context (e.g. a control vq in vDPA) instead =
of
> > tying to mm. In this case there is no pgtable binding initiated from us=
er
> > space. Instead, ioasid is allocated from /dev/ioasid and then programme=
d
> > to the intended security context through specific passthrough framework
> > which manages that context.
>=20
> This sounds like the exact opposite of what I'd like to see.
>=20
> I do not want to see every subsystem gaining APIs to program a
> PASID. All of that should be consolidated in *one place*.
>=20
> I do not want to see VDPA and VFIO have two nearly identical sets of
> APIs to control the PASID.
>=20
> Drivers consuming a PASID, like VDPA, should consume the PASID and do
> nothing more than authorize the HW to use it.
>=20
> quemu should have general code under the viommu driver that drives
> /dev/ioasid to create PASID's and manage the IO mapping according to
> the guest's needs.
>=20
> Drivers like VDPA and VFIO should simply accept that PASID and
> configure/authorize their HW to do DMA's with its tag.
>=20

I agree with you on consolidating things in one place (especially for the
general SVA support). But here I was referring to an usage without=20
pgtable binding (Possibly Jason. W can say more here), where the=20
userspace just wants to allocate PASIDs, program/accept PASIDs to=20
various workqueues (device specific), and then use MAP/UNMAP=20
interface to manage address spaces associated with each PASID.=20
I just wanted to point out that the latter two steps are through=20
VFIO/VDPA specific interfaces.=20

Thanks
Kevin