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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23CE5C4332F for ; Mon, 7 Nov 2022 08:40:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231299AbiKGIj7 (ORCPT ); Mon, 7 Nov 2022 03:39:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231226AbiKGIj6 (ORCPT ); Mon, 7 Nov 2022 03:39:58 -0500 Received: from relay10.mail.gandi.net (relay10.mail.gandi.net [217.70.178.230]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3D5F515709; Mon, 7 Nov 2022 00:39:57 -0800 (PST) Received: (Authenticated sender: maxime.chevallier@bootlin.com) by mail.gandi.net (Postfix) with ESMTPSA id AE13B240012; Mon, 7 Nov 2022 08:39:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1667810395; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Kt3YaVgos6aTLVWYjMs61pa3ceG8lp2j8XYt+Ucplyw=; b=AscLybvqBkKKgJLxu4it0nKtw+XOslDBXsHBsvlHVxB0Quj8CJoOpqRBmXiqfOd1/kasH9 I+cRuyTQ77O+3UrGUe3ZGeH7rU1c/DtCrPXXS+URrPf5lzaNMrG7+Bc9qi70AWFk/HuaSt jolcAbhp1rSvg2qX53A0bk241bSR4UCNLi0r3AMKmZCI5JP75FU80j+GTBU53Iy1XyffQi Uv2CTDUq7j4BuVRIrD5Rb5nvrcN87Urg4Q7WbnybzhsxcFFSPae5Z7j42qmFbMKsj+HI3J vXojYdsYBdNtD5o2z/B8c6rgd+JXFd3YWUtUB46TeWGWJbN4757yjat0WVARgg== Date: Mon, 7 Nov 2022 09:39:50 +0100 From: Maxime Chevallier To: Jakub Kicinski Cc: davem@davemloft.net, Rob Herring , Krzysztof Kozlowski , Eric Dumazet , Paolo Abeni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, thomas.petazzoni@bootlin.com, Andrew Lunn , Florian Fainelli , Heiner Kallweit , Russell King , linux-arm-kernel@lists.infradead.org, Vladimir Oltean , Luka Perkov , Robert Marko , Andy Gross , Bjorn Andersson , Konrad Dybcio Subject: Re: [PATCH net-next v8 3/5] net: dsa: add out-of-band tagging protocol Message-ID: <20221107093950.74de3fa1@pc-8.home> In-Reply-To: <20221104200530.3bbe18c6@kernel.org> References: <20221104174151.439008-1-maxime.chevallier@bootlin.com> <20221104174151.439008-4-maxime.chevallier@bootlin.com> <20221104200530.3bbe18c6@kernel.org> Organization: Bootlin X-Mailer: Claws Mail 4.1.0 (GTK 3.24.34; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hello Jakub, On Fri, 4 Nov 2022 20:05:30 -0700 Jakub Kicinski wrote: > On Fri, 4 Nov 2022 18:41:49 +0100 Maxime Chevallier wrote: > > This tagging protocol is designed for the situation where the link > > between the MAC and the Switch is designed such that the Destination > > Port, which is usually embedded in some part of the Ethernet > > Header, is sent out-of-band, and isn't present at all in the > > Ethernet frame. > > > > This can happen when the MAC and Switch are tightly integrated on an > > SoC, as is the case with the Qualcomm IPQ4019 for example, where > > the DSA tag is inserted directly into the DMA descriptors. In that > > case, the MAC driver is responsible for sending the tag to the > > switch using the out-of-band medium. To do so, the MAC driver needs > > to have the information of the destination port for that skb. > > > > Add a new tagging protocol based on SKB extensions to convey the > > information about the destination port to the MAC driver > > This is what METADATA_HW_PORT_MUX is for, you shouldn't have > to allocate a piece of memory for every single packet. Does this work with DSA ? The information conveyed in the extension is the DSA port identifier. I'm not familiar at all with METADATA_HW_PORT_MUX, should we extend that mechanism to convey the DSA port id ? I also agree that allocating data isn't the best way to go, but from the history of this series, we've tried 3 approaches so far : - Adding a new field to struct sk_buff, which isn't a good idea - Using the skb headroom, but then we can't know for sure is the skb contains a DSA tag or not - Using skb extensions, that comes with the cost of this memory allocation. Is this approach also incorrect then ? > Also the series doesn't build. Can you elaborate more ? I can't reproduce the build failure on my side, and I didn't get any reports from the kbuild bot, are you using a specific config file ? Thanks, Maxime