From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-02.galae.net (smtpout-02.galae.net [185.246.84.56]) (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 F373B329C44; Thu, 23 Oct 2025 14:19:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.84.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761229171; cv=none; b=fP0uxA0sw1/757oQnarCpNphJwaSxJAMEVwO0J11Es+LSo72EaYQDdSXtkfetf+P6zYGuAGjWTrZzO0xWBkm/W1nu90t/psUPHLqBR44boH8E3lR//0Dki1DeEB4uH0WfOxH1wPP53dt0TkGQeTgEOI1uyLFgEmsXErkTBKYDok= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761229171; c=relaxed/simple; bh=HzqfBrlXW6O7F5EtXwkrAduCbaf4snx4zKoGIjdlgf4=; h=Mime-Version:Content-Type:Date:Message-Id:From:Subject:Cc:To: References:In-Reply-To; b=nUUsveo9Aa+HTiW+SH5E1Lis0nBqNiE0dqCRYJfux2jTBBT+5gxVKixjPeQtwbngnJhXg/gUvYyRQ/c1HJIz9pVQt8HTky7P+l7gfpJY5bSLHoLBI0EitoHq/ntPdQxBnklvr4j14bIgNVriSThTcaj3wd6PE3//tUs3vwKidi4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=qNgKvpU2; arc=none smtp.client-ip=185.246.84.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="qNgKvpU2" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-02.galae.net (Postfix) with ESMTPS id E44C01A1617; Thu, 23 Oct 2025 14:19:25 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id B63326068C; Thu, 23 Oct 2025 14:19:25 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 89A30102F2469; Thu, 23 Oct 2025 16:19:07 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1761229164; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=HzqfBrlXW6O7F5EtXwkrAduCbaf4snx4zKoGIjdlgf4=; b=qNgKvpU2CjPJtQSwjcNfl3i9yQmN0DMrwzKhlKuzSSJkzQ4EV5jDSqQCVZqMA1W3sp6PiO ETXodZ91r7/aOSn28IpGGNP1/uqsIyUgvOFzIz3E08R3hOdcKbTEZ8NKgUWWHHwgo+JeyZ f7utcJj1XoBoSG+IMd8/dQH2XNG69Vj931NiL57TbTOGxCFWSYa+F9jZtP8NVW2LVY3S+1 5wHnY8YpGOE2EblVzOPJ2wTazIbPuc9EZfD1ctm/7P10QyekbUd3QcCLDW0i9syTz4GWz0 /nK/zbExk4Dek+76fBVpfVtiJGnvu6s4sOpYokxnhhkv3xnKEP4c7R5+SszR0g== Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Thu, 23 Oct 2025 16:19:07 +0200 Message-Id: From: =?utf-8?q?Th=C3=A9o_Lebrun?= Subject: Re: [PATCH net-next v2 2/5] net: macb: match skb_reserve(skb, NET_IP_ALIGN) with HW alignment Cc: "Andrew Lunn" , "David S. Miller" , "Eric Dumazet" , "Jakub Kicinski" , "Paolo Abeni" , "Rob Herring" , "Krzysztof Kozlowski" , "Conor Dooley" , "Nicolas Ferre" , "Claudiu Beznea" , "Russell King" , , , , =?utf-8?q?Beno=C3=AEt_Monin?= , =?utf-8?q?Gr=C3=A9gory_Clement?= , "Maxime Chevallier" , "Tawfik Bayouk" , "Thomas Petazzoni" , "Vladimir Kondratiev" To: "Andrew Lunn" , =?utf-8?q?Th=C3=A9o_Lebrun?= X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20251022-macb-eyeq5-v2-0-7c140abb0581@bootlin.com> <20251022-macb-eyeq5-v2-2-7c140abb0581@bootlin.com> <7950f287-f025-40d9-b182-c1002d955a5b@lunn.ch> In-Reply-To: <7950f287-f025-40d9-b182-c1002d955a5b@lunn.ch> X-Last-TLS-Session-Version: TLSv1.3 On Wed Oct 22, 2025 at 9:27 PM CEST, Andrew Lunn wrote: > On Wed, Oct 22, 2025 at 09:38:11AM +0200, Th=C3=A9o Lebrun wrote: >> If HW is RSC capable, it cannot add dummy bytes at the start of IP >> packets. Alignment (ie number of dummy bytes) is configured using the >> RBOF field inside the NCFGR register. >>=20 >> 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. >>=20 >> 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). >>=20 >> Fixes: 4df95131ea80 ("net/macb: change RX path for GEM") > > Is this a real fix? You should not mix new development with > fixes. Either post this patch to net, or drop the Fixes: tag for > net-next. No, it isn't fixing any platform that currently uses the driver. Dropped the "Fixes:" trailer for next revision. Thanks Andrew, -- Th=C3=A9o Lebrun, Bootlin Embedded Linux and Kernel engineering https://bootlin.com