From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-173.mta0.migadu.com (out-173.mta0.migadu.com [91.218.175.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 337712E2DC3 for ; Mon, 11 Aug 2025 18:53:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754938410; cv=none; b=r0C7uxQkrEPi+Rd7aezXP/9nK6HT6vkSTHVtypjiGAQLx9tZBgtXpfBwZeePVNjoS6Cg4nkLkY/N9S6VaUHloyZrjXQq0e3sszaHgO3Z0QrUu9rFjPl909JkKy3bro2DMyuFDaaMMRNGZxZWbZts5qnCauupGLYfg2dZLrzF5Xg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754938410; c=relaxed/simple; bh=ACaCCx/zYEw6greU3vAV3sCC6jE2zat1KZSmI+K260U=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Ge8KUbcxHp/BZOV0ueQVqyPTmzqV/11TZnqCVNAjMMBMRubJ5rUeBv4KWTD+YFqHfauzm4oOcc8CmSXSfOYQkIYm6Mygk6QLFdlgIW0+mgYmlxOtB6N1vGQRqk3v5PV+QsByLmgUc9serEUbyMzlIclHGRHWQwNMJxvAS8ChRuY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=u136D40H; arc=none smtp.client-ip=91.218.175.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="u136D40H" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1754938405; 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=0R2bnIhPyR3QQbpGsQ2ZiExRLQ4FHglk5+SDpIvYRfw=; b=u136D40HAZRm2Ns4PIkj7lNjk9GpEzIDA0c6PL4vfZunBpXOL+T8bK9eSHezE+/ErbtzoA LFQBQRUjQbRcJ1FXpHpS4eMH3GHZTlm1PKk0cvRkbUEl1ubAtZ3EEn0ylwCcFNanSmEGhi 3Gh+X8fqy4yk5tSREu0rhyEpC/kmjMI= Date: Mon, 11 Aug 2025 14:53:19 -0400 Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH net-next v2 12/18] net: macb: match skb_reserve(skb, NET_IP_ALIGN) with HW alignment To: =?UTF-8?Q?Th=C3=A9o_Lebrun?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Nicolas Ferre , Claudiu Beznea , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Samuel Holland , Richard Cochran , Russell King , Thomas Bogendoerfer , Vladimir Kondratiev , Gregory CLEMENT , Cyrille Pitchen , Harini Katakam , Rafal Ozieblo , Haavard Skinnemoen Cc: netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-mips@vger.kernel.org, Thomas Petazzoni , Tawfik Bayouk References: <20250627-macb-v2-0-ff8207d0bb77@bootlin.com> <20250627-macb-v2-12-ff8207d0bb77@bootlin.com> <1a4fe95a-f029-43b2-aed1-594365254b6a@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Sean Anderson In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 8/7/25 11:24, Théo Lebrun wrote: > On Tue Jul 1, 2025 at 6:40 PM CEST, Sean Anderson wrote: >> On 6/27/25 05:08, Théo Lebrun wrote: >>> If HW is RSC capable, it cannot add dummy bytes at the start of IP >> >> Receive-side coalescing? Can you add a brief description of this >> feature to your commit message? > > Yes that is Receive Side Coalescing. Clearly it needs to be mentioned > out loud, and briefly described. > >>> packets. Alignment (ie number of dummy bytes) is configured using the >>> RBOF field inside the NCFGR register. >>> >>> On the software side, the skb_reserve(skb, NET_IP_ALIGN) call must only >>> be done if those dummy bytes are added by the hardware; notice the >>> skb_reserve() is done AFTER writing the address to the device. >>> >>> We cannot do the skb_reserve() call BEFORE writing the address because >>> the address field ignores the low 2/3 bits. Conclusion: in some cases, >>> we risk not being able to respect the NET_IP_ALIGN value (which is >>> picked based on unaligned CPU access performance). >>> >>> Fixes: 4df95131ea80 ("net/macb: change RX path for GEM") >> >> Do any existing MACBs support RSC? Is this a fix? > > I have no idea. If any MACB supports RSC, it must be those running with > NET_IP_ALIGN=0, so arm64/powerpc/x86. > > Is it a fix? We can guess that all boards fall in either category: > - Don't support RSC (=> RBOF works fine). > - Support RSC (=> RBOF not working) AND NET_IP_ALIGN=0. > > Both of those are not impacted, so we technically don't fix anything for > current users. OK, then please drop the fixes tag then. --Sean 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 55D3FCA0EDB for ; Mon, 11 Aug 2025 22:04:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=PGjL+NGOYi5aValkbzDhqBENzzwQmXniCm2HlFlC7h8=; b=RJKBwbZtiw3pUf Pv11j8s3y6LVvQApBYoqDL8qPEtDBSUB75ylvyCVie9tAKAuGkWSHuhYbyKToScDC5SMvEHLFes4z qknk6O6EwexbEkzDHMvEx9Cs5HHx+vQGE/eiAVKdSGq4Bs9RSEeckm8WcEkrnjR2lGzUXIR61B4h2 w5EDZEb5Wz9sG3kO5yeg2ZCjBsF6jdHqZblZgLfn0f2fJIPZeCAysaztuIfsLxpP9lkgm+qysfGt9 ZmcZ0RZOgPEy9WjgLImDzN5JbI+bkFT7YYjhp5eNEi8wkzmYeSInAF2WC7eXn6g2joU4+IjIzmzgK YlQKYRBfW1ZYLlMSEnCw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1ulacv-00000009D4U-2VOK; Mon, 11 Aug 2025 22:04:21 +0000 Received: from out-171.mta0.migadu.com ([91.218.175.171]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1ulXeD-00000008qS4-2mOV for linux-riscv@lists.infradead.org; Mon, 11 Aug 2025 18:53:31 +0000 Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1754938405; 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=0R2bnIhPyR3QQbpGsQ2ZiExRLQ4FHglk5+SDpIvYRfw=; b=u136D40HAZRm2Ns4PIkj7lNjk9GpEzIDA0c6PL4vfZunBpXOL+T8bK9eSHezE+/ErbtzoA LFQBQRUjQbRcJ1FXpHpS4eMH3GHZTlm1PKk0cvRkbUEl1ubAtZ3EEn0ylwCcFNanSmEGhi 3Gh+X8fqy4yk5tSREu0rhyEpC/kmjMI= Date: Mon, 11 Aug 2025 14:53:19 -0400 MIME-Version: 1.0 Subject: Re: [PATCH net-next v2 12/18] net: macb: match skb_reserve(skb, NET_IP_ALIGN) with HW alignment To: =?UTF-8?Q?Th=C3=A9o_Lebrun?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Nicolas Ferre , Claudiu Beznea , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Samuel Holland , Richard Cochran , Russell King , Thomas Bogendoerfer , Vladimir Kondratiev , Gregory CLEMENT , Cyrille Pitchen , Harini Katakam , Rafal Ozieblo , Haavard Skinnemoen Cc: netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-mips@vger.kernel.org, Thomas Petazzoni , Tawfik Bayouk References: <20250627-macb-v2-0-ff8207d0bb77@bootlin.com> <20250627-macb-v2-12-ff8207d0bb77@bootlin.com> <1a4fe95a-f029-43b2-aed1-594365254b6a@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Sean Anderson In-Reply-To: X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250811_115329_916740_E6B3DE6E X-CRM114-Status: GOOD ( 14.55 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org T24gOC83LzI1IDExOjI0LCBUaMOpbyBMZWJydW4gd3JvdGU6Cj4gT24gVHVlIEp1bCAxLCAyMDI1 IGF0IDY6NDAgUE0gQ0VTVCwgU2VhbiBBbmRlcnNvbiB3cm90ZToKPj4gT24gNi8yNy8yNSAwNTow OCwgVGjDqW8gTGVicnVuIHdyb3RlOgo+Pj4gSWYgSFcgaXMgUlNDIGNhcGFibGUsIGl0IGNhbm5v dCBhZGQgZHVtbXkgYnl0ZXMgYXQgdGhlIHN0YXJ0IG9mIElQCj4+Cj4+IFJlY2VpdmUtc2lkZSBj b2FsZXNjaW5nPyBDYW4geW91IGFkZCBhIGJyaWVmIGRlc2NyaXB0aW9uIG9mIHRoaXMKPj4gZmVh dHVyZSB0byB5b3VyIGNvbW1pdCBtZXNzYWdlPwo+IAo+IFllcyB0aGF0IGlzIFJlY2VpdmUgU2lk ZSBDb2FsZXNjaW5nLiBDbGVhcmx5IGl0IG5lZWRzIHRvIGJlIG1lbnRpb25lZAo+IG91dCBsb3Vk LCBhbmQgYnJpZWZseSBkZXNjcmliZWQuCj4gCj4+PiBwYWNrZXRzLiBBbGlnbm1lbnQgKGllIG51 bWJlciBvZiBkdW1teSBieXRlcykgaXMgY29uZmlndXJlZCB1c2luZyB0aGUKPj4+IFJCT0YgZmll bGQgaW5zaWRlIHRoZSBOQ0ZHUiByZWdpc3Rlci4KPj4+IAo+Pj4gT24gdGhlIHNvZnR3YXJlIHNp ZGUsIHRoZSBza2JfcmVzZXJ2ZShza2IsIE5FVF9JUF9BTElHTikgY2FsbCBtdXN0IG9ubHkKPj4+ IGJlIGRvbmUgaWYgdGhvc2UgZHVtbXkgYnl0ZXMgYXJlIGFkZGVkIGJ5IHRoZSBoYXJkd2FyZTsg bm90aWNlIHRoZQo+Pj4gc2tiX3Jlc2VydmUoKSBpcyBkb25lIEFGVEVSIHdyaXRpbmcgdGhlIGFk ZHJlc3MgdG8gdGhlIGRldmljZS4KPj4+IAo+Pj4gV2UgY2Fubm90IGRvIHRoZSBza2JfcmVzZXJ2 ZSgpIGNhbGwgQkVGT1JFIHdyaXRpbmcgdGhlIGFkZHJlc3MgYmVjYXVzZQo+Pj4gdGhlIGFkZHJl c3MgZmllbGQgaWdub3JlcyB0aGUgbG93IDIvMyBiaXRzLiBDb25jbHVzaW9uOiBpbiBzb21lIGNh c2VzLAo+Pj4gd2UgcmlzayBub3QgYmVpbmcgYWJsZSB0byByZXNwZWN0IHRoZSBORVRfSVBfQUxJ R04gdmFsdWUgKHdoaWNoIGlzCj4+PiBwaWNrZWQgYmFzZWQgb24gdW5hbGlnbmVkIENQVSBhY2Nl c3MgcGVyZm9ybWFuY2UpLgo+Pj4gCj4+PiBGaXhlczogNGRmOTUxMzFlYTgwICgibmV0L21hY2I6 IGNoYW5nZSBSWCBwYXRoIGZvciBHRU0iKQo+Pgo+PiBEbyBhbnkgZXhpc3RpbmcgTUFDQnMgc3Vw cG9ydCBSU0M/IElzIHRoaXMgYSBmaXg/IAo+IAo+IEkgaGF2ZSBubyBpZGVhLiBJZiBhbnkgTUFD QiBzdXBwb3J0cyBSU0MsIGl0IG11c3QgYmUgdGhvc2UgcnVubmluZyB3aXRoCj4gTkVUX0lQX0FM SUdOPTAsIHNvIGFybTY0L3Bvd2VycGMveDg2Lgo+IAo+IElzIGl0IGEgZml4PyBXZSBjYW4gZ3Vl c3MgdGhhdCBhbGwgYm9hcmRzIGZhbGwgaW4gZWl0aGVyIGNhdGVnb3J5Ogo+ICAtIERvbid0IHN1 cHBvcnQgUlNDICg9PiBSQk9GIHdvcmtzIGZpbmUpLgo+ICAtIFN1cHBvcnQgUlNDICg9PiBSQk9G IG5vdCB3b3JraW5nKSBBTkQgTkVUX0lQX0FMSUdOPTAuCj4gCj4gQm90aCBvZiB0aG9zZSBhcmUg bm90IGltcGFjdGVkLCBzbyB3ZSB0ZWNobmljYWxseSBkb24ndCBmaXggYW55dGhpbmcgZm9yCj4g Y3VycmVudCB1c2Vycy4KCk9LLCB0aGVuIHBsZWFzZSBkcm9wIHRoZSBmaXhlcyB0YWcgdGhlbi4K Ci0tU2VhbgoKCl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f CmxpbnV4LXJpc2N2IG1haWxpbmcgbGlzdApsaW51eC1yaXNjdkBsaXN0cy5pbmZyYWRlYWQub3Jn Cmh0dHA6Ly9saXN0cy5pbmZyYWRlYWQub3JnL21haWxtYW4vbGlzdGluZm8vbGludXgtcmlzY3YK