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Miller" , Jonathan Corbet , Shuah Khan , Simon Horman , Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Andrew Morton , "Borislav Petkov (AMD)" , Randy Dunlap , Dave Hansen , Christian Brauner , Petr Mladek , "Peter Zijlstra (Intel)" , Thomas Gleixner , Pawan Gupta , Dapeng Mi , Kees Cook , Marco Elver , Eric Biggers , "NBU-Contact-Li Rongqing (EXTERNAL)" , "Paul E. McKenney" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "linux-rdma@vger.kernel.org" References: <20260508175213.1952097f@kernel.org> <580a774b-ba9e-4523-b43a-476f75dd5b12@nvidia.com> <29868c1b-5751-421a-9f2b-2ac0f3324904@nvidia.com> Content-Language: en-US From: Mark Bloch In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: FR0P281CA0214.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:ac::8) To CH3PR12MB7548.namprd12.prod.outlook.com (2603:10b6:610:144::12) Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PR12MB7548:EE_|MN2PR12MB4175:EE_ X-MS-Office365-Filtering-Correlation-Id: 1a1ea837-93ed-4d89-d609-08deb1b5266c X-LD-Processed: 43083d15-7273-40c1-b7db-39efd9ccc17a,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014|4143699003|11063799003|22082099003|18002099003|56012099003; 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So that is a device-based decision. >>>>>>>>>> I believe as such it can optionally be permanenty configured (nv config) >>>>>>>>>> on older device. Why not? >>>>>>>>> >>>>>>>> Because sometimes switchdev_inactive is needed and sometimes not. >>>>>>>> Such knob is not device decision. >>>>>>> >>>>>>> That is what I would call corner case. In that, user can use userspace >>>>>>> configuration to change the mode in runtime. >>>>>>> >>>>>> Corner vs common depends on users one talks to. :) >>>>>> If fw has switchdev(active) as default, and then >>>>>> And user needs to run switchdev_inactive, it will actually break their switching applications. >>>>> >>>>> Can you describe the actutal breakage please? >>>>> >>>> Driver default was switchdev so all the traffic is forwarded to the switch, >>>> and user didn't have chance to setup the fdb rules. >>>> So packets are dropped but user didn't expect the traffic to be forwarded. >>> >>> User may switch mode to switchdev_inactive early on, before any of the >>> representors are created. What's the issue then? >> >> That is the ordering problem I am trying to solve. >> >> On a DPU, the host PF cannot finish loading until the ECPF moves the eswitch to >> switchdev/switchdev_inactive. So we need to do that transition during ECPF >> driver init, as early as possible. Waiting for userspace means the host PF stays >> blocked until userspace is up and has the right logic. >> >> That is not always true in practice, the driver may be built in, loaded from an >> initramfs, or the initramfs may simply not contain the devlink policy we need. >> >> Also, after talking with Parav, my understanding is that we need to support both >> switchdev and switchdev_inactive, since different customers want different boot >> behavior. Once we do the transition, the host PF can load and may start sending >> packets. At that point the initial mode already matters: in switchdev_inactive >> packets are dropped until userspace programs the pipeline; in switchdev they may >> reach the FDB before the pipeline is ready. >> >> So I do not think an early userspace transition is equivalent here. The initial >> mode needs to be known by the kernel before userspace runs, which is why I am >> proposing the devlink= command line default. > > Okay fair enough. Could you please at least make sure this is mode only > config and noone would ever think about abusing this for any other > configuration? Perhaps call it "devlink_eswitch_mode=" to remove > the "devlink=" namespace flexibility? Sure, something along these lines: devlink_eswitch_mode=[*]:switchdev devlink_eswitch_mode=[pci/0000:08:00.0,pci/0000:09:00.1]:switchdev_inactive The proper (not RFC) series will have 3 patches: - devlink: add the command-line default eswitch mode handling - mlx5: cleanup/prep patch - mlx5: use the devlink API to apply the early eswitch mode Since the mlx5 changes are part of the series, I suspect this will need to go through Tariq. The patches are ready, but are currently in our submission queue. Mark