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dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=nvidia.com; Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates 12.22.5.236 as permitted sender) receiver=protection.outlook.com; client-ip=12.22.5.236; helo=mail.nvidia.com; Received: from mail.nvidia.com (12.22.5.236) by CO1NAM11FT019.mail.protection.outlook.com (10.13.175.57) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.20.4951.12 via Frontend Transport; Fri, 4 Feb 2022 03:19:29 +0000 Received: from rnnvmail201.nvidia.com (10.129.68.8) by DRHQMAIL109.nvidia.com (10.27.9.19) with Microsoft SMTP Server (TLS) id 15.0.1497.18; Fri, 4 Feb 2022 03:19:29 +0000 Received: from nvidia.com (10.126.230.35) by rnnvmail201.nvidia.com (10.129.68.8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.9; Thu, 3 Feb 2022 19:19:27 -0800 From: Alexander Kozyrev To: CC: , , Subject: [PATCH] doc: add limitation on MPRQ usage in multi-process app Date: Fri, 4 Feb 2022 05:19:13 +0200 Message-ID: <20220204031913.595195-1-akozyrev@nvidia.com> X-Mailer: git-send-email 2.18.2 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.126.230.35] X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: e4758765-edce-4f57-e384-08d9e78d2820 X-MS-TrafficTypeDiagnostic: PH7PR12MB5655:EE_ X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; 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SFS:(13230001)(4636009)(46966006)(40470700004)(36840700001)(36756003)(36860700001)(82310400004)(356005)(81166007)(54906003)(40460700003)(6916009)(316002)(86362001)(47076005)(1076003)(2616005)(4326008)(426003)(186003)(70586007)(336012)(70206006)(6286002)(26005)(8676002)(5660300002)(83380400001)(508600001)(55016003)(16526019)(107886003)(2906002)(7696005)(6666004)(8936002)(36900700001); DIR:OUT; SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Feb 2022 03:19:29.8191 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: e4758765-edce-4f57-e384-08d9e78d2820 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a; Ip=[12.22.5.236]; Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT019.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB5655 X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org MPRQ cannot be used in multi-process applications because of externally attached MPRQ buffers. A callback is registered by a primary process to free MPRQ buffers once they are no longer needed. But this information is shared among all the processes. The virtual address of the mlx5_mprq_buf_free_cb function is different in a secondary process, which leads to a segmentation fault. Document that MPRQ is not supported in a multi-process app, since there is no way to find out if this is the one. Signed-off-by: Alexander Kozyrev Acked-by: Viacheslav Ovsiienko --- doc/guides/nics/mlx5.rst | 3 +++ 1 file changed, 3 insertions(+) diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst index daa7f2affb..7ac997ac27 100644 --- a/doc/guides/nics/mlx5.rst +++ b/doc/guides/nics/mlx5.rst @@ -138,6 +138,9 @@ Limitations - For secondary process: - Forked secondary process not supported. + - MPRQ is not supported. Callback to free externally attached MPRQ buffer is sets + in a primary process, but has a different virtual address in a secondary process. + Calling a function at the wrong address leads to a segmentation fault. - External memory unregistered in EAL memseg list cannot be used for DMA unless such memory has been registered by ``mlx5_mr_update_ext_mp()`` in primary process and remapped to the same virtual address in secondary -- 2.18.2