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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C3C0C3A5A6 for ; Fri, 30 Aug 2019 14:59:46 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 7083923427 for ; Fri, 30 Aug 2019 14:59:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="USrlillk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7083923427 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=hmFWKv+k7RIOeir2n+uefIDngQGM0cBN+KP7+OTK/xE=; b=USrlillkqFt/WJ LhmXBj6r3QsWkMPRbPO5W2wJvmWvVCx5JD/aBYgInI2wm17zOJCUDZGFfOLbyHm1cWwcJjzYUfiLd JyojDeZU3Lk/qukk+XwyrFD9Y1/0nOinMHMoZqrTee2axTzifTmSmEV1GuSQEgMExc+CgbyoGyx7h cOxvhvMc/Na6P8IUdcX89OzqZNHEwdZDlPbA9KQB/4foVRqwX7G6qNfu/Vd90CkZlMAflIuj4AuRc OOOvlLiN6xNyWc3FiydB0YkIGG9j8krwkDtdEr+iUAZ1Gf9umtAZW+J/f7FXmujj5G6/jtrMUz/6u 2cLH0+E4KRoJ0RDLL2Og==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i3iNO-0002mM-1C; Fri, 30 Aug 2019 14:59:46 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1i3iNK-0002kz-7W for linux-arm-kernel@lists.infradead.org; Fri, 30 Aug 2019 14:59:44 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 8244E68BFE; Fri, 30 Aug 2019 16:59:35 +0200 (CEST) Date: Fri, 30 Aug 2019 16:59:35 +0200 From: Christoph Hellwig To: Russell King - ARM Linux admin Subject: Re: [PATCH 1/4] vmalloc: lift the arm flag for coherent mappings to common code Message-ID: <20190830145935.GA19838@lst.de> References: <20190830062924.21714-1-hch@lst.de> <20190830062924.21714-2-hch@lst.de> <20190830092918.GV13294@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190830092918.GV13294@shell.armlinux.org.uk> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190830_075942_422072_552CD905 X-CRM114-Status: GOOD ( 12.58 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-xtensa@linux-xtensa.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Robin Murphy , Christoph Hellwig , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Aug 30, 2019 at 10:29:18AM +0100, Russell King - ARM Linux admin wrote: > On Fri, Aug 30, 2019 at 08:29:21AM +0200, Christoph Hellwig wrote: > > The arm architecture had a VM_ARM_DMA_CONSISTENT flag to mark DMA > > coherent remapping for a while. Lift this flag to common code so > > that we can use it generically. We also check it in the only place > > VM_USERMAP is directly check so that we can entirely replace that > > flag as well (although I'm not even sure why we'd want to allow > > remapping DMA appings, but I'd rather not change behavior). > > Good, because if you did change that behaviour, you'd break almost > every ARM framebuffer and cripple ARM audio drivers. How would that break them? All the usual video and audio drivers that use dma_alloc_* then use dma_mmap_* which never end up in the only place that actually checks VM_USERMAP (remap_vmalloc_range_partial) as they end up in the dma_map_ops mmap methods which contain what is effecitvely open coded versions of that routine. There are very few callers of remap_vmalloc_range_partial / remap_vmalloc_range, and while a few of those actually are in media drivers and the virtual frame buffer video driver, none of these seems to be called on dma memory (which would be a layering violation anyway). _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel