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 87522C38145 for ; Wed, 7 Sep 2022 14:16:40 +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=UWsrXlvLQA40AR1XGofyCwFvaKscT1WgISWTtM/w/U4=; b=Gwj6HglbT0Zo7i FkHRANUU1uh87vKjMlTLhxmkkiko+sk/kGipXgDfiKoc5gDWk91JUsbjvTspYUFe6KzONR0rCU7Vc dI53T+FDpABrWc72yaWY/9/3QWj+Eb1j6NZjxQ8eftjvYXY96l3qjchBPRcu9GnEJQi//a3a4aH5c qUVZo6n0pnl/JBpd4UYwmh/7584Ff8hygoJ8LSMhWv2VRR9XEWXYUZkswMnfcNavJq3HbSZ0GcSSQ iZ/iDUlfR10EdRJI+sxbtEOycx/oN/Eoq+q4qpn0Az4Q+Up7YEylnVO4J1YDpGopKjEp1hV2MkfZX GbF+PxTJkWgHWj8yXCvA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oVvqH-006loU-Nx; Wed, 07 Sep 2022 14:15:49 +0000 Received: from pandora.armlinux.org.uk ([2001:4d48:ad52:32c8:5054:ff:fe00:142]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oVvqF-006lmY-12 for linux-arm-kernel@lists.infradead.org; Wed, 07 Sep 2022 14:15:48 +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=Hg6qzf3HJbNbp0dCwY4t8RE4nU3+CGfcWl0VQD+yUPM=; b=yrTy2XOP5xC/7f7PWvOCATWkoy c3HgQPpKFVHZg5T6BP3LfTnsuPgwyXOnVqVJ3/68VJ4t5Naclv6f8MqCGhyqRihx0CXqLSUsh0wOU PosTZvTS/xFn4lcfL7kuDM5YGIqIPZbebmyWEiIT/YQNWhLyTw4L+SRM6eg51dUh+T98M2jpbaClA NXJ1X/GH9QWJ+TokbKFxoX6DY/56bZfTQuUqzAvhcZpv1UU5oSAr7s7NKoYrwiC9F0gd4E8kdSvu6 8Buxz7eoyAKuLhxcNbtMdFOzhrV8rIO+7phF5anYNRXeE4W/wNHHCMzPbIpK4y5V9dX+vXHuiic5T zCVqJmcg==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:34184) 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 1oVvqB-0005UM-DC; Wed, 07 Sep 2022 15:15:43 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1oVvqA-0001AZ-J8; Wed, 07 Sep 2022 15:15:42 +0100 Date: Wed, 7 Sep 2022 15:15:42 +0100 From: "Russell King (Oracle)" To: Christoph Hellwig Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, Mark Rutland , Robin Murphy , Ard Biesheuvel Subject: Re: [PATCH] arm64: dma: Drop cache invalidation from arch_dma_prep_coherent() Message-ID: References: <20220823122111.17439-1-will@kernel.org> <20220907090434.GB30704@lst.de> <20220907141441.GA21984@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220907141441.GA21984@lst.de> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220907_071547_090849_BBCDEC7B X-CRM114-Status: GOOD ( 13.71 ) 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 Wed, Sep 07, 2022 at 04:14:41PM +0200, Christoph Hellwig wrote: > On Wed, Sep 07, 2022 at 03:10:35PM +0100, Russell King (Oracle) wrote: > > If we allocate memory, clean (and maybe invalidate) the cache, and then > > zero the memory _after_ the clean, then couldn't we be creating dirty > > cache lines. There are caches out there that are write-allocate, which > > means that by writing zeros to memory, you drag cache lines back into > > the cache. > > When writting through an uncached mapping? Eww. That's going to be slow. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps 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