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:     "Chatre, Reinette" <reinette.chatre@intel.com>,
        "jgg@nvidia.com" <jgg@nvidia.com>,
        "yishaih@nvidia.com" <yishaih@nvidia.com>,
        "shameerali.kolothum.thodi@huawei.com" 
        <shameerali.kolothum.thodi@huawei.com>,
        "alex.williamson@redhat.com" <alex.williamson@redhat.com>
CC:     "tglx@linutronix.de" <tglx@linutronix.de>,
        "darwi@linutronix.de" <darwi@linutronix.de>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "Jiang, Dave" <dave.jiang@intel.com>,
        "Liu, Jing2" <jing2.liu@intel.com>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        "Yu, Fenghua" <fenghua.yu@intel.com>,
        "tom.zanussi@linux.intel.com" <tom.zanussi@linux.intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH V4 07/11] vfio/pci: Update stale comment
Thread-Topic: [PATCH V4 07/11] vfio/pci: Update stale comment
Thread-Index: AQHZeS7OdjCZc/1V50izazr3xzJnga9ARQ7g
Date:   Fri, 28 Apr 2023 06:42:49 +0000
Message-ID: <BN9PR11MB5276651EF3C7A11C2D60BB8D8C6B9@BN9PR11MB5276.namprd11.prod.outlook.com>
References: <cover.1682615447.git.reinette.chatre@intel.com>
 <f16872889aed9a7b042a7e53722b9ae83430a126.1682615447.git.reinette.chatre@intel.com>
In-Reply-To: <f16872889aed9a7b042a7e53722b9ae83430a126.1682615447.git.reinette.chatre@intel.com>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?CItE0vGx1X/cRllYZMp5JbJhq739b3y3Z+6Zg+1JHdBynd3JcpB4oZrtoR9e?=
 =?us-ascii?Q?XvIp71m/3mmwkqva3Ekhp08JKPqTok+g45AWxpHAviRWScX3AHTdZISX4NMA?=
 =?us-ascii?Q?D5q+mBft6d2Fzdt+JFAiDHb1NU0dHJGtUh3mr6u5PF0dcAk0tgaFPZQTK+RC?=
 =?us-ascii?Q?Fn9jDeuf6LfZslWGoq5J/XNoiCzrr4txJtUeNIwwv5y06G1En7z+RWx1TgN0?=
 =?us-ascii?Q?GAaAKpU1rxog8pLhogKnO6po7KGxDBW9yg6QRSWuFqbBZd7JQxQtcdj4AbiK?=
 =?us-ascii?Q?ZwoQBLIE6E/tqndgJGq7WudV3hj72vsuyDOYa0DoLrG5VdlyV2tHUJtQiPxf?=
 =?us-ascii?Q?LSstPuhSJpSYB4NGU00Iuk+X5XW0Bsx4EtzqCvD0uLPD+EiJKHUzpMrG7cgC?=
 =?us-ascii?Q?PkCaTiGQvQ6IH9XvwF7XXlwPwiaA3tyDB67TiX1r1Ggq3d7JaJKe2ZXM1maf?=
 =?us-ascii?Q?yLrT7jiUEV8d78qR+Q+FwNq5VfRkrcJ71Jq4YbXIdNTiOOltA1tr1an3wnkF?=
 =?us-ascii?Q?v5t0DzopZdoyGASSKxa5ZrC4eMtroEBDUBlFoU/PI1PHkMc3sJVyQ9D5JH6B?=
 =?us-ascii?Q?soyFApPsD9SDGNcUwzc4y498fM91pVOg37KX4XUwPGmrw0y1h6iRehtkne+E?=
 =?us-ascii?Q?MIUzU6j5zwmfLTolXYaXlYBjGjFp1eZNQ6Eq5Y53PWvepXk5myRbQAihjaXZ?=
 =?us-ascii?Q?Cde8zfPLub2yhgFuv/sqBcx++Clgp1BsIEdTzzTCbR0DIpvRVBjIcBJ0A1gU?=
 =?us-ascii?Q?zEVKAkn8W6t8DU21P53OpzIsJLBoTeg7wD3kQ9DAy5Oz6mSNqALVbejR/M5j?=
 =?us-ascii?Q?g7ng8n2YjISJ+YAVBMlY/t8izdnR7s9ZpaAcoq/czGovnxCTO0WN2Jat9CS9?=
 =?us-ascii?Q?bXycOXsu9GV/J4iVbkHNLgXvepnXInFvjcVNgV4tivzMTofgTf6Md1ZW04Mc?=
 =?us-ascii?Q?ftwOj7+EfRZER40CquF6gokKDtERkbRQ6Pi94Xnhg1Js9ALJTwTySt1F3pzW?=
 =?us-ascii?Q?4M4gWBiZlXX9EtYOgn/7TzFn1jtGzg+XSOWp9+Yq8H7vtYJVgQnivpDJwdug?=
 =?us-ascii?Q?SvQYB6WvznxKPnv4Hrm5fP+DoO91xaGsBJ0xbp3+frv7saNqCBD8cfZaLCdX?=
 =?us-ascii?Q?VSvb76uXmSarGVb1/gIvgCCx2GjdD59PezgmBZhIc1JIEqYBX54M2XvDSHNH?=
 =?us-ascii?Q?FaOzcvNh5d7MgJlxeRqIuDrGSsKxtvBMjhy4YaXk/2YUclHaJI6pDPkFZlAB?=
 =?us-ascii?Q?d5fAXLgZgzDGNLD+pYrnCInOI4d+9qoelIyF4rYZju1A+gupXl1qrtOqS6F6?=
 =?us-ascii?Q?LcUZ3NVSzkWtwC6yXW7AyPwX5/aQ/9wXeHTXDTmBmZEPx0XMa++rPfjS0Itu?=
 =?us-ascii?Q?ucIwQohZz7B2AWV/SSHW9oMnBcl9M7yeV30gvE+Igevg7BI0j0TGgsOldOWS?=
 =?us-ascii?Q?dGoxMJKma7F3Byp6oYP5Wwz0MKaiLXFjQQt1FJXkPwpcyPqNaUnKpaXcn+wU?=
 =?us-ascii?Q?2Whm9eqlDSOkXOi3DDPJp9pw33OUpkOJzUjsbShm8RHyOOZd08gznPd0mm4E?=
 =?us-ascii?Q?bquHw7WLYW4VM79TGYloxnfOWm+qThMPxVzB6KAH?=
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: ba79e7d2-0112-4f9a-adac-08db47b3c889
X-MS-Exchange-CrossTenant-originalarrivaltime: 28 Apr 2023 06:42:49.1689
 (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: u1u8QAX9pkj6ffEFIunvHgi7pynif6Njyme7VVGKyv4QspikhNadMMFp84MOlysE4tsL35Wid7L3gZdlIiiZ/A==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY1PR11MB8126
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-4.6 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,URIBL_BLOCKED
        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: Chatre, Reinette <reinette.chatre@intel.com>
> Sent: Friday, April 28, 2023 1:36 AM
>=20
> @@ -419,11 +419,9 @@ static int vfio_msi_set_vector_signal(struct
> vfio_pci_core_device *vdev,
>  	}
>=20
>  	/*
> -	 * The MSIx vector table resides in device memory which may be
> cleared
> -	 * via backdoor resets. We don't allow direct access to the vector
> -	 * table so even if a userspace driver attempts to save/restore
> around
> -	 * such a reset it would be unsuccessful. To avoid this, restore the
> -	 * cached value of the message prior to enabling.
> +	 * If the vector was previously allocated, refresh the on-device
> +	 * message data before enabling in case it had been cleared or
> +	 * corrupted since writing.
>  	 */
>  	cmd =3D vfio_pci_memory_lock_and_enable(vdev);
>  	if (msix) {

What about keeping backdoor reset as an example, e.g.

"in case it had been cleared or corrupted (e.g. due to backdoor resets) ...=
"

otherwise one may doubt whether it is a more severe problem causing
the corruption inadvertently w/o userspace driver's awareness and then
whether just restoring the data is sufficient to move on.