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=-2.2 required=3.0 tests=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 5B136C3A59B for ; Fri, 30 Aug 2019 15:01:04 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (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 1EF522341B for ; Fri, 30 Aug 2019 15:01:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1EF522341B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id C9BC560C8; Fri, 30 Aug 2019 15:01:03 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id E0A575C7E for ; Fri, 30 Aug 2019 14:59:40 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 4EF4F89B for ; Fri, 30 Aug 2019 14:59:40 +0000 (UTC) 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) 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 X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.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). _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu