Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   "Tian, Kevin" <kevin.tian@intel.com>
To:     Jean-Philippe Brucker <jean-philippe@linaro.org>
CC:     Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <joro@8bytes.org>,
        "Jason Gunthorpe" <jgg@nvidia.com>,
        Christoph Hellwig <hch@infradead.org>,
        "Raj, Ashok" <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        "Jiang, Dave" <dave.jiang@intel.com>,
        Vinod Koul <vkoul@kernel.org>,
        "Eric Auger" <eric.auger@redhat.com>,
        "Liu, Yi L" <yi.l.liu@intel.com>,
        "Pan, Jacob jun" <jacob.jun.pan@intel.com>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v7 06/10] iommu/sva: Refactoring
 iommu_sva_bind/unbind_device()
Thread-Topic: [PATCH v7 06/10] iommu/sva: Refactoring
 iommu_sva_bind/unbind_device()
Thread-Index: AQHYa1GHkRXh3WJ3kEuCY8op0Mm4AK0t2DnwgAALZoCAAPxJwA==
Date:   Wed, 25 May 2022 02:04:49 +0000
Message-ID: <BN9PR11MB5276FF0D52CF82942CB84D608CD69@BN9PR11MB5276.namprd11.prod.outlook.com>
References: <20220519072047.2996983-1-baolu.lu@linux.intel.com>
 <20220519072047.2996983-7-baolu.lu@linux.intel.com>
 <BN9PR11MB5276E462E3B32DDE54DD66418CD79@BN9PR11MB5276.namprd11.prod.outlook.com>
 <Yoy6NxroLLZup0sE@myrica>
In-Reply-To: <Yoy6NxroLLZup0sE@myrica>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?A9nozbHkvGmq5GhfVNNyp+PAxmk/SjS6HiiPrBRWe///yKLudQ9+P70MgA/u?=
 =?us-ascii?Q?Me7FTs5yOgjkcm63T9a2NqUzMsWX4nFaOWMscXJ+QgJzlB7QrX/WTQbXV+I+?=
 =?us-ascii?Q?hRuihs0E+3OsO/P/WwTDEeaifSzD6PdeYfHA5i0LDma4r53NYwH86zDp17AF?=
 =?us-ascii?Q?GAr0YP2hDpDNj07fcqzw807iF+YUfFiJVpznfLvsIWsgRdjGTi8mp6d8lBU5?=
 =?us-ascii?Q?QDVSGumIu6SgdRIhPXpQ5MjXto8rqVvqR3GXgtIvEO7nBBkjYiqWTd+oZegl?=
 =?us-ascii?Q?4y+f6oS+XLR53/MJHnA3Ax4Vxd763AXFCekOH9HmGOif8GSJXj05uzPUOR9c?=
 =?us-ascii?Q?AY6d9muLByGUpqkI4saZm8+54Ej4EKMRWxaTMIQF5uLZKVypP7R8BKZNlk10?=
 =?us-ascii?Q?TJhxdtmzJbNzyddymsHCN4G8Y4BrPPJ0O3sdJBq04O4XEOR/OoUs9IedqslZ?=
 =?us-ascii?Q?05xat0biVw5UlVO7bPYTOX7hsLAb130gT05K4ov8C48DX9PbO6mGj4o0wLOU?=
 =?us-ascii?Q?1G+jmfmMCbcgrq0rCI00K0Huo6YqZ91g6PpErDyJAwOdKhp9wsdP4NzqVxAc?=
 =?us-ascii?Q?a7H0GtwJn56GgVjJY73uaunQvhE0rvhQ3qknEuQ8m/yeEoE7qT5g/Dtxqyce?=
 =?us-ascii?Q?rfgpX1LQOBvirub4nTm8yl/yzjhAkhaQ0OfaIJ3d9KOp4zIjNK4CMk4rAz6U?=
 =?us-ascii?Q?iu/gqbOpramFcPKucGVFNLqy61XveGiY4ecLsMU8nhUwB1PCGS4KJjxuhYxR?=
 =?us-ascii?Q?I1CISRV1YYPq29T898+O4iPgywn3x+vU9XtO1XZYNguUhVSQfS0YaEsE+R9b?=
 =?us-ascii?Q?DLQTx4eiITg0ibivBim2b7Ywzj98z9gWlCP/OhXCJKAMZlmq10pUxvyf0l+d?=
 =?us-ascii?Q?d2BPSMVZ7YZ+OkZyYKnfuBjRgvTOKT6XrqAF6kyhcpm7DIRH5Ribounhogm+?=
 =?us-ascii?Q?FQB0qRhK4NI35ayAC2aobA96h4Pc0WwW/UiiSl7aYrxJJf6ukOjIpmf0hUEE?=
 =?us-ascii?Q?Jg1VSUAtMctBbEXsMOiIqo7EWrX4Xze1yQs2X/TwGF0i12D3DCLVfYoYOEKx?=
 =?us-ascii?Q?L/AnJja5VzDDsO3G2oGUAR9USwltOCX7jLaQQVq8IWKM882VmhFyYyBDoP8R?=
 =?us-ascii?Q?bwBlfR889VUTPYW7iWagbI6Y1oAtJrR76Y9ecKNIMxKoO/Tq8VuGO8R1Bdjd?=
 =?us-ascii?Q?TsfULsKfj6p74J8+3n6f7tFBD1rb1etN6OpJ0K+zfFvO6n3GB06oNjK+8z0A?=
 =?us-ascii?Q?aLV4neDryPPQ1GCkpzIruZSMvlXvk+Mca6azJltItLHpAVItlpy11Wl7bvD2?=
 =?us-ascii?Q?uPJoru9W8muVIm5vFNa3T28IeDjs7Chx0KG7PY+b5xmLq4WgygxS4nT6+QX2?=
 =?us-ascii?Q?uTe7J3F+Xg29wsyzxVXmFIjH/vr0UMa3TfgWJDcRwrp4Qqlen4KcKLnygWx4?=
 =?us-ascii?Q?NxsOSR3/pc5q8XDWHqjYTXZxdRwlEHjtINft69ZbjBnwkk4ZMsIKYnJcFlNN?=
 =?us-ascii?Q?t6/HBox8p+xkypx/0hOEuT/89YWTDqqy/WAxT4/wVyLlgaVr7eqmfG2A9Jll?=
 =?us-ascii?Q?AaI+R6mqC+0TsmydhoKrpg1PnQYbMc0v+a3sf7OT0kvaUPxKxJG66xXUZ7Bj?=
 =?us-ascii?Q?hjydHPn8yQ1TPO0zWNYwdY8YyJ+TdvwuO7Eh2hVaCeyLIftYA0VK/dj7rcfM?=
 =?us-ascii?Q?WOu0iGt76EYfdAdrUKwLwqGE6Tx8f9kZTFa50YOXRmssV0dG2XaF49j1YJ/l?=
 =?us-ascii?Q?tNkb2SovOQ=3D=3D?=
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: BN9PR11MB5276.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: cd6a4ad0-9051-452e-7f19-08da3df2f2f3
X-MS-Exchange-CrossTenant-originalarrivaltime: 25 May 2022 02:04:49.3301
 (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: DLeJlTAaaElKRJED7oH5aUZr1sZNnnYza+9XYs16zY8VRYlVcg9fjlNoSmIQHEIkO+URPymol6anKlRnHzDUTA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR11MB4408
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-5.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,
        SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham
        autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Sent: Tuesday, May 24, 2022 6:58 PM
>=20
> On Tue, May 24, 2022 at 10:22:28AM +0000, Tian, Kevin wrote:
> > > From: Lu Baolu <baolu.lu@linux.intel.com>
> > > Sent: Thursday, May 19, 2022 3:21 PM
> > >
> > > The existing iommu SVA interfaces are implemented by calling the SVA
> > > specific iommu ops provided by the IOMMU drivers. There's no need for
> > > any SVA specific ops in iommu_ops vector anymore as we can achieve
> > > this through the generic attach/detach_dev_pasid domain ops.
> >
> > set/block_pasid_dev, to be consistent.
> >
> > > +
> > > +	mutex_lock(&iommu_sva_lock);
> > > +	/* Search for an existing domain. */
> > > +	domain =3D iommu_get_domain_for_dev_pasid(dev, mm->pasid);
> > > +	if (domain) {
> > > +		sva_domain =3D to_sva_domain(domain);
> > > +		refcount_inc(&sva_domain->bond.users);
> > > +		goto out_success;
> > > +	}
> > > +
> >
> > why would one device/pasid be bound to a mm more than once?
>=20
> Device drivers can call bind() multiple times for the same device and mm,
> for example if one process wants to open multiple accelerator queues.
>=20

Is it clearer to have a sva_bond_get/put() pair instead of calling
bind() multiple times here?=20