Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:8 as permitted sender) client-ip=2620:137:e000::3:8;
From:   "Tian, Kevin" <kevin.tian@intel.com>
To:     Nicolin Chen <nicolinc@nvidia.com>
CC:     "Liu, Yi L" <yi.l.liu@intel.com>,
        "joro@8bytes.org" <joro@8bytes.org>,
        "alex.williamson@redhat.com" <alex.williamson@redhat.com>,
        "jgg@nvidia.com" <jgg@nvidia.com>,
        "robin.murphy@arm.com" <robin.murphy@arm.com>,
        "baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>,
        "cohuck@redhat.com" <cohuck@redhat.com>,
        "eric.auger@redhat.com" <eric.auger@redhat.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "mjrosato@linux.ibm.com" <mjrosato@linux.ibm.com>,
        "chao.p.peng@linux.intel.com" <chao.p.peng@linux.intel.com>,
        "yi.y.sun@linux.intel.com" <yi.y.sun@linux.intel.com>,
        "peterx@redhat.com" <peterx@redhat.com>,
        "jasowang@redhat.com" <jasowang@redhat.com>,
        "shameerali.kolothum.thodi@huawei.com" 
        <shameerali.kolothum.thodi@huawei.com>,
        "lulu@redhat.com" <lulu@redhat.com>,
        "suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>,
        "iommu@lists.linux.dev" <iommu@lists.linux.dev>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-kselftest@vger.kernel.org" <linux-kselftest@vger.kernel.org>,
        "Duan, Zhenzhong" <zhenzhong.duan@intel.com>,
        "joao.m.martins@oracle.com" <joao.m.martins@oracle.com>,
        "Zeng, Xin" <xin.zeng@intel.com>,
        "Zhao, Yan Y" <yan.y.zhao@intel.com>
Subject: RE: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE
Thread-Topic: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE
Thread-Index: AQHaGVcJ4nFLu64FV02Qq9BjVpwSvbCC3axQgAAHEwCAAAD1wIAAl++AgACaJQA=
Date:   Tue, 21 Nov 2023 02:50:05 +0000
Message-ID: <BN9PR11MB5276C8EACE2C300A646EA8A18CBBA@BN9PR11MB5276.namprd11.prod.outlook.com>
References: <20231117130717.19875-1-yi.l.liu@intel.com>
 <20231117130717.19875-3-yi.l.liu@intel.com>
 <BN9PR11MB5276D8406BF08B853329288C8CB4A@BN9PR11MB5276.namprd11.prod.outlook.com>
 <fa736836-e136-4ed4-a6af-8ea2f0e7c0dd@intel.com>
 <BN9PR11MB527659462CCB7280055858D98CB4A@BN9PR11MB5276.namprd11.prod.outlook.com>
 <ZVuZOYFzAaCuJjXZ@Asurada-Nvidia>
In-Reply-To: <ZVuZOYFzAaCuJjXZ@Asurada-Nvidia>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?uhWBwzbZN/685n1RnYSzS3gM3ZU8rA3SbTcPT2Xol0U+rrhaXzK45oPCWOP9?=
 =?us-ascii?Q?rmB8nvapzC0GSv0/7SlrpJ1xwiOI4v80vGsOrCMBhrEW/KFi7fxnOzaWdcIj?=
 =?us-ascii?Q?75i3jRurDEy+vH+xvQl7N3q8Fh3rzdoKnaBcEjjdMBYq3cfvMFEH+lRxV7Uo?=
 =?us-ascii?Q?GJ4BFwNYFK+wPsxln9BJOcfzESCyOUIB2fWcJvjXdwQKNAHqNoTh+KwDhJVQ?=
 =?us-ascii?Q?YWd2w4A3GGZ4yYWBcMIGSK9W+rcMHP2DyFQBV/TAOJWNgIltT+diyMJImPz4?=
 =?us-ascii?Q?lnAAlLHXP6bNeQ8luSv7bM37gZ3KU8RDVaUkts3CjV876lEZlpPsNkP4tDoR?=
 =?us-ascii?Q?v1YU3QfFZZRnS2cd7F/Kfs3pzB+mIknCQQ88WyQ7qsn3YXsNSPfe+TwIsEhl?=
 =?us-ascii?Q?wwevjuJPnDbCvQf6wnj5Om6DamVzDUy6b5RvA/ThXzuu4fnvPjK0HmRtAZ3T?=
 =?us-ascii?Q?IiqsPssyBDwyCP2k5ZvLIdsLh3Hx7Cr0DAAKi3Oo13X8PqygclrmpHrgV3Kh?=
 =?us-ascii?Q?TftnlbduAjW20/N2mRW7oleNjC9svlwqGO8gFGezA+C36H/BiJDMsxDQiv7k?=
 =?us-ascii?Q?KkQE0/xjFy7LBvfeQ7AQZuhNSoXkkk/hdpbbIydQ4ZDPvApRdw7hKXiQqAc6?=
 =?us-ascii?Q?ZURblvMqAM9/Dp2yCusl/YA99nH5oY9kvNGuNEYd7jdWF0AM4ZTzHlMq/lDT?=
 =?us-ascii?Q?UpwhW8edWMALEDJ3xK4GoBsSsGKgE7B96AJegqVwFED2LOM6tm/ooO2hVXzX?=
 =?us-ascii?Q?pIRRKGSL2NqZPHAw7UNVOf/dlbWKqnUnZYK3xHpyYdwbHl9BL/K9xrLrJCg3?=
 =?us-ascii?Q?cso3BpPyGeHpdHZfZGWlfm9jQ4m7zqIsnalWBvjhwVvJ2Ip+k5VxL5a++dFR?=
 =?us-ascii?Q?Jt0pxX3mWK0YgSdR++KZpTXNKDZiykIpgbfFTrdYZkWs0bBDX9d4RvIMltTR?=
 =?us-ascii?Q?cbLxPXDtDItpyjCMOrQIb0KMIBn0Xy228bgyXUvTtIQC8kjEzaUQtkV0YkOU?=
 =?us-ascii?Q?CIMElNA8Xy7CBVuS/STLWs3GrN6kLi2+DET0yB04X/Twik0FOOiDmmZ482vJ?=
 =?us-ascii?Q?wVWw0Tl+5LkiNxShMN3N4Mr8ny0NvZXKuz2KLAOjSSpWfRGXmF8pybYlN/J+?=
 =?us-ascii?Q?G6uEgl2gEaiL62i0F/CbPII9dcr3E4dVsqLmpHy/FFvxsP8m+IOsmp96lcLB?=
 =?us-ascii?Q?L372mt943DZBxxd7Kp9XeCz/6cCB/R99pgdaAYxEPnAdl/0aMGtgJNesilvp?=
 =?us-ascii?Q?btUo12ncbsVoLv5KwZaLK7jV+kNIJESBcSeOtwxLFToCfmezHDcyWvCxpGu+?=
 =?us-ascii?Q?7UwsMadBICuImphzSIIFSh+kRxBMWOnqdCl5BQ+R6kNksFSkjutfHh2+X9/A?=
 =?us-ascii?Q?g8XfEjkmPn5yPrRg35h3D5/BnU74PEW2lcxJG2+Ba1HOA1p54YPszbmhyUPZ?=
 =?us-ascii?Q?jkThiOEzX+bXQn1i4MOE9Vj89jTZrqrTdhj3xxtKHlsyGX8j9u8VWIq14n7j?=
 =?us-ascii?Q?3fk70nUrUQhPy2+6Qx14g/WkKZgRfuhmIEfKSFvEnriP1a6IstCeDvDd+86H?=
 =?us-ascii?Q?VwF6RYRlpN4LkM5wqvZZ+4NfCKrZvOE78rXsiQ0R?=
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: 63304275-2a02-4ff1-17b9-08dbea3c910d
X-MS-Exchange-CrossTenant-originalarrivaltime: 21 Nov 2023 02:50:05.4938
 (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: H9nn1y3ceY1z2Z9aSO7VQVfTK6bUjMGP/urJ3pam5SMNoqZXXtKhcVQ/VwS4wSILbj1KqDh9uPYDapp1bi0NIw==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR11MB4612
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE
	autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on fry.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (fry.vger.email [0.0.0.0]); Mon, 20 Nov 2023 18:50:26 -0800 (PST)

> From: Nicolin Chen <nicolinc@nvidia.com>
> Sent: Tuesday, November 21, 2023 1:37 AM
>=20
> On Mon, Nov 20, 2023 at 08:34:58AM +0000, Tian, Kevin wrote:
> > > From: Liu, Yi L <yi.l.liu@intel.com>
> > > Sent: Monday, November 20, 2023 4:30 PM
> > >
> > > On 2023/11/20 16:09, Tian, Kevin wrote:
> > > >> From: Liu, Yi L <yi.l.liu@intel.com>
> > > >> Sent: Friday, November 17, 2023 9:07 PM
> > > >> + * @req_len: Length (in bytes) of a request entry in the request =
array
> > > >> + * @req_num: Input the number of cache invalidation requests in t=
he
> > > array.
> > > >> + *           Output the number of requests successfully handled b=
y
> kernel.
> > > >> + * @out_driver_error_code: Report a driver speicifc error code up=
on
> > > failure.
> > > >> + *                         It's optional, driver has a choice to =
fill it or
> > > >> + *                         not.
> > > >
> > > > Being optional how does the user tell whether the code is filled or=
 not?
>=20
> Well, naming it "error_code" indicates zero means no error while
> non-zero means something? An error return from this ioctl could
> also tell the user space to look up for this driver error code,
> if it ever cares.

probably over-thinking but I'm not sure whether zero is guaranteed to
mean no error in all implementations...

>=20
> > > seems like we need a flag for it. otherwise, a reserved special value=
 is
> > > required. or is it enough to just document it that this field is avai=
lable
> > > or not per the iommu_hw_info_type?
> > >
> >
> > No guarantee that a reserved special value applies to all vendors.
> >
> > I'll just remove the optional part. the viommu driver knows what a vali=
d
> > code is, if the driver fills it.
>=20
> Hmm, remove out_driver_error_code? Do you mean by reusing ioctl
> error code to tell the user space what driver error code it gets?
>=20

No. I just meant to remove the last sentence "It's optional ..."