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 74336C77B73 for ; Sat, 3 Jun 2023 12:39:07 +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:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=vwJLwo7MbNL7NPnDvKgsZk2g3lPxlme8UOqprL0YPUM=; b=yGYfYLPa3YpciY Ku8QqlF0ZncuK0LM9pX1edy2ypqca+lKfHiGU64NJjHHf38hdI8GiI1H+l9DBcClHAvbwKthV4iJ/ JpOJk1L3H/nAa6Uaot6WAN26AFtlozQXbaXoV2CIfLQ8ZOCndiqEmokmqQwILaQ+DNKp7SjbAUrrT ryZlixKVe/RPv/JqYmEoglY/Za/qP5o6JAdz6KivfhHRBn3Z6dsSDNXJoulHyHQLXsQYJ9DNxkKwF f7ePaNZz2EdeDaoTct7zXukr040yBcdj8bEccviXmULavpxTKKKEe9q13FcctA2SO6WxKGTwXJe2B 3NctfCFUbyO79gq5feRw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1q5QWq-009l3w-08; Sat, 03 Jun 2023 12:38:44 +0000 Received: from pandora.armlinux.org.uk ([2001:4d48:ad52:32c8:5054:ff:fe00:142]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1q5QWn-009l3K-1Q for linux-arm-kernel@lists.infradead.org; Sat, 03 Jun 2023 12:38:42 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=FYxP//pEp5JwsFfiiB2fPkPaZfUZ/lmbN9waaEjNaro=; b=osQmeyN9JIyUbxPZ7//1YH7W/2 jvdBDZlsjxoNIUh2AJiBJRFB77gIRR9qg0kDIE5O8Ro6v90po/Cats/r9xu2sEBI0q9ZET8ujSSS2 Od5GLusKegcCWF7jZzlUWTp2sBLIq5weRG5ZLXWgIo5ntSnNDBpk11/HbOKiwdVUtXAZ0QaxDguVj RlsrfN/hnqKo89kznsTxlGQsODeq+xRchqVVmdcr3vIAYK+/jeLnTbzWAeV22lpb5EOCpGXI4jtI+ KmnFnzvFfG5AJz6NT4uxWlSd2teSc1/DXu/17MOP+yO8Vt4tbIl1tPD3NMpNxOcme4DsPKd/yXjiM y1/XD0Ig==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:42276) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1q5QWi-0001H1-Ad; Sat, 03 Jun 2023 13:38:36 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1q5QWg-00041j-6u; Sat, 03 Jun 2023 13:38:34 +0100 Date: Sat, 3 Jun 2023 13:38:34 +0100 From: "Russell King (Oracle)" To: Arnd Bergmann Cc: Stefan Wahren , Florian Fainelli , Robin Murphy , Christoph Hellwig , Nicolas Saenz Julienne , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] ARM: mm: Fix ARCH_LOW_ADDRESS_LIMIT when CONFIG_ZONE_DMA Message-ID: References: <20230603090643.6799-1-stefan.wahren@i2se.com> <121092e9-a718-45f7-938d-a2cff7e92214@app.fastmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <121092e9-a718-45f7-938d-a2cff7e92214@app.fastmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230603_053841_504913_C1F3BC25 X-CRM114-Status: GOOD ( 10.30 ) X-BeenThere: linux-arm-kernel@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="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sat, Jun 03, 2023 at 02:33:49PM +0200, Arnd Bergmann wrote: > Changing the low address limit by itself makes the swiotlb work > correctly, but for performance we also want to avoid having to > use the swiotlb at all when dealing with the zero page. How often is the zero page used for DMA _to_ a device (it should never be used for DMA _from_ a device.) ? It doesn't sound that useful to me, since it can only be used for writing zeros. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last! _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel