From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, PDS_BAD_THREAD_QP_64,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D634C433ED for ; Fri, 7 May 2021 11:48:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BFF860FF3 for ; Fri, 7 May 2021 11:48:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234729AbhEGLtn (ORCPT ); Fri, 7 May 2021 07:49:43 -0400 Received: from mail-db8eur05on2078.outbound.protection.outlook.com ([40.107.20.78]:17888 "EHLO EUR05-DB8-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S235328AbhEGLtm (ORCPT ); Fri, 7 May 2021 07:49:42 -0400 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=iMMKUa5r5fZrKOkr8p0LjaO6qBjAN7Pz3sg1xxxz/m6TqYj+aw7s2pKpzpQFeItwHVSN0T6AkUgeOH6kIlTXOAiqbQ4OkI+EVX44rqIm2A61fW0wU6PpRRk/bdJbO9a/ZTmysaKf+v5t6Z/2WP0Rv86l1uGpt99FF5PmFxL4/+MePflMcz3B27PGrPbRiDvWHJk3LkMC+tL1L7FIzBkoL3gggOjzVTrJAAcBFLh6OGU1ST3EVNEjO9zkWZxZT8XD3YZ0Zsg2UKrfPCQibxDGFHXwTSbbJ/pyHCoY6vEau1fd94iZ2vQQvgA3bDai803yo4P2gOznTGuGrCSY1qxFMg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=01f437XOs2KyHgQWDEagqS5C/UDWO8zr6WF743JjPbQ=; b=bJ5yq/s93fHK9ox/ld05H8/cPTeryRs+Ex2vop3j1K4o94Q7pjlduTB/VDMSNe97DxB+GiKqJwjTJUxbIYSewHtBWvxs1XFnqKTL5Kri6FjNKFTmROTyvZGCMESlIj+esJW5ihc+JiqeZ7ewyBp5h6gMg6KeXM48OYvovZLI4IY3/siEkCWXqQAh7fZdYV8Wr3rz4g/wH1Ekvx93TzOs60m83bM1RbCWY+zovmnfwNVIi/wwJkplqCSU+BYmS1efLjdoyAJ83M4leDMr1nmhse/2wgCba6FlrYBZYVuceNHQFBqvqd4wliz9uBMQwqnxD8zeWVvYZBjANZxrtqPfbA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nxp.com; dmarc=pass action=none header.from=nxp.com; dkim=pass header.d=nxp.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nxp.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=01f437XOs2KyHgQWDEagqS5C/UDWO8zr6WF743JjPbQ=; b=TKcenVuJ2urCyfRyqWTaV7vL2XBV42fFUNUvjWpo7TX4cLcKTjdsxeWrR+NvMZEJ7+P9kP5OTJh3fbnEMhQDCGVVbWzfSkhJ8ZhfUSI4xImq0ML8y+k5tABCzClSWxrjYtttyffSWs6a/hWy6xeuMHFjI8yLkEYqgsz/fRKEAYY= Received: from VI1PR04MB5136.eurprd04.prod.outlook.com (2603:10a6:803:55::19) by VE1PR04MB6640.eurprd04.prod.outlook.com (2603:10a6:803:122::32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4108.26; Fri, 7 May 2021 11:48:38 +0000 Received: from VI1PR04MB5136.eurprd04.prod.outlook.com ([fe80::f0c0:cb99:d153:e39b]) by VI1PR04MB5136.eurprd04.prod.outlook.com ([fe80::f0c0:cb99:d153:e39b%7]) with mapi id 15.20.4108.028; Fri, 7 May 2021 11:48:38 +0000 From: Vladimir Oltean To: "Y.b. Lu" CC: Tobias Waldekranz , "netdev@vger.kernel.org" , Richard Cochran , "David S . Miller" , Jakub Kicinski , Jonathan Corbet , Kurt Kanzenbach , Andrew Lunn , Vivien Didelot , Florian Fainelli , Claudiu Manoil , Alexandre Belloni , "UNGLinuxDriver@microchip.com" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [net-next, v2, 3/7] net: dsa: free skb->cb usage in core driver Thread-Topic: [net-next, v2, 3/7] net: dsa: free skb->cb usage in core driver Thread-Index: AQHXOn8JAwAhGEvKKUeIpvbpNi0+oarKZYAAgA2NKwCAAAYrgA== Date: Fri, 7 May 2021 11:48:37 +0000 Message-ID: <20210507114837.aybpln6twhstelqd@skbuf> References: <20210426093802.38652-1-yangbo.lu@nxp.com> <20210426093802.38652-4-yangbo.lu@nxp.com> <87y2d2noe5.fsf@waldekranz.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: nxp.com; dkim=none (message not signed) header.d=none;nxp.com; dmarc=none action=none header.from=nxp.com; x-originating-ip: [86.127.41.210] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 08e510c4-a534-466f-bfc6-08d9114e0d81 x-ms-traffictypediagnostic: VE1PR04MB6640: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:9508; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: 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 x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:VI1PR04MB5136.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(7916004)(4636009)(396003)(346002)(136003)(366004)(376002)(39850400004)(64756008)(66556008)(66446008)(6512007)(66476007)(66946007)(76116006)(86362001)(9686003)(71200400001)(4326008)(54906003)(33716001)(186003)(53546011)(6506007)(316002)(44832011)(8936002)(478600001)(966005)(6636002)(8676002)(122000001)(38100700002)(1076003)(7416002)(5660300002)(26005)(2906002)(6862004)(6486002);DIR:OUT;SFP:1101; x-ms-exchange-antispam-messagedata: =?us-ascii?Q?Ry2F+RTqwKoGUs4iLwkvEz1YwGM82SD/lkarUrtBgGHSucYmfcfcP5yP42JF?= =?us-ascii?Q?rV0AFha2I6+495nAkx6VWRm9SO3qvlUbwpWTihO7yS6O2XaqVkdSXyHFkse4?= =?us-ascii?Q?jh2XRJz6APhnk23oQnffM6Va8jmsTN1TRn62Oajbp4MsAWLFSOFvDvJOdIe2?= =?us-ascii?Q?Sm8RBthih0U+GTDnQBLWezZolqqs7UOrXHkJx+0yFr2tk/eWBMCY7znSFtMo?= =?us-ascii?Q?X762G0MKGbsf/xTgwWPEvI2KXmDSZJ1zJNoSzeVdpDVRSlHmMlooTiFQkTDx?= =?us-ascii?Q?jqOBSVtcOQLYzLJPGtrAoMeB2HlmDYDVMFBm9ATujf+UmYpMXgtRuJ3x/0M/?= =?us-ascii?Q?C/0Vt44CKnunM6Ve4YZIVAUhbmziQD+1x1rsOP1Zq8oMS2vZDT4dwwvn1PZb?= =?us-ascii?Q?84nOlX4pY/qnXVvJEjtRbzUOcXwIUMaWzMEgNX1sJx48r5NADW9AJzcrfK96?= =?us-ascii?Q?5QT+vz/iHF6B/qj/8lB/sUVtvoM31shFtRgbquwgcNMtgR8+P1/xABib6vqG?= =?us-ascii?Q?IYDyS44cywQIyhLw18ROxwqJD35guZahxaWPgycXiCCKwlzhI31ADx8w5vJp?= =?us-ascii?Q?3FFDfdRvycTQUHZ5GiDAope8ISwc3+F7N+et2/W3pw8lxas5L/4abSlMXgss?= =?us-ascii?Q?a8jh3Df6sxCmjkXjtU9ZIfGrxnAl7aNGcGEGijeAOc1f8Q+Zu+fOcv4ME0GS?= =?us-ascii?Q?HS65LWJC79vkj3iJpSSZNGjTlKPqRyrUGO8oPWWuWH86gE3+/wcKqiBYQ4pb?= =?us-ascii?Q?BIm47nZ53u5fBPO3jxt875L1qtive49YNmlxBYdX/bOCdYZqGOD1uCI5XVWs?= =?us-ascii?Q?TtodQDvlZ9Ca1fAz23WNLowmn86E4lwDWhLo9SRLoZ+mcJsbaIcJ0ZQVICnO?= =?us-ascii?Q?uk+z7hM4nRvkH/spCPI0KQtte+YemfctH4icGEoForwFaY24gij/Dgoaglz+?= =?us-ascii?Q?vLulbPWWS2j5bWClxR5Lt2e8Ua+p/prwiFK6Mc3MTKPOaEyntdWuPTKRMypL?= =?us-ascii?Q?IhabDnJ8UxiKvtrApkOnFmXnJgUTRbjL/D72456CSPc0DaQp+yTTgqhJGb8s?= =?us-ascii?Q?C1AGF0j1H+FB38RbxFx8GhJKEf6iWpt6Wx2GMo+C3Bk0+Z8wROibrVA9rFaT?= =?us-ascii?Q?rBRpM+Q/X+Ur3EbfhmjEcpZvxfxOzM85Mel7vfmSOqUJxcEWon45VJdsJiiH?= =?us-ascii?Q?jRWD0PcqiobpSdAg9Ns+tXKbb7p2rRnE8sixT8PtGckLK0VHd9R1cTKLYLYY?= =?us-ascii?Q?qCZRyUnaRSDJ0+kMD4zlzWjbhPBjaW48rr8He/3gAeSW1df1Av8z3zC40jhE?= =?us-ascii?Q?7QcXrvQ3tOxmxn0E42AvAtN0?= Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB5136.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 08e510c4-a534-466f-bfc6-08d9114e0d81 X-MS-Exchange-CrossTenant-originalarrivaltime: 07 May 2021 11:48:37.9645 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 0iNzVljQ3Qm1vxoMENrOTVNv9lBi+eYUJjm6N9x9SS5swcRw3OsV6RPUBf10WPck0NVw1nOefU9vTqgwX33Qbg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: VE1PR04MB6640 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, May 07, 2021 at 11:26:32AM +0000, Y.b. Lu wrote: > > From: Tobias Waldekranz > > On Mon, Apr 26, 2021 at 17:37, Yangbo Lu wrote: > > > Free skb->cb usage in core driver and let device drivers decide to us= e > > > or not. The reason having a DSA_SKB_CB(skb)->clone was because > > > dsa_skb_tx_timestamp() which may set the clone pointer was called > > > before p->xmit() which would use the clone if any, and the device > > > driver has no way to initialize the clone pointer. > > > > > > Although for now putting memset(skb->cb, 0, 48) at beginning of > > > dsa_slave_xmit() by this patch is not very good, there is still way t= o > > > improve this. Otherwise, some other new features, like one-step > > > > Could you please expand on this improvement? > > > > This memset makes it impossible to carry control buffer information fro= m > > driver callbacks that run before .ndo_start_xmit, for > > example .ndo_select_queue, to a tagger's .xmit. > > > > It seems to me that if the drivers are to handle the CB internally from= now on, > > that should go for both setting and clearing of the required fields. > > For the timestamping case, dsa_skb_tx_timestamp may not touch > .port_txtstamp callback, so we had to put skb->cb initialization at > beginning of dsa_slave_xmit. > To avoid breaking future skb->cb usage you mentioned, do you think we > can back to Vladimir's idea initializing only field required, or even > just add a callback for cb initialization for timestamping? I would like to avoid overengineering, which a callback for skb->cb initialization would introduce, given the needs we have now. FWIW, we may not even be able to touch skb->cb in .ndo_select_queue for Tobias's use case, that discussion is here: https://patchwork.kernel.org/project/netdevbpf/patch/20210426170411.1789186= -7-tobias@waldekranz.com/=