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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 2483AC04EBF for ; Wed, 5 Dec 2018 14:45:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E628B20892 for ; Wed, 5 Dec 2018 14:45:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E628B20892 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727751AbeLEOpq (ORCPT ); Wed, 5 Dec 2018 09:45:46 -0500 Received: from foss.arm.com ([217.140.101.70]:55974 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727025AbeLEOpq (ORCPT ); Wed, 5 Dec 2018 09:45:46 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A06B180D; Wed, 5 Dec 2018 06:45:45 -0800 (PST) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 6F1C13F59C; Wed, 5 Dec 2018 06:45:45 -0800 (PST) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 2F5D71AE0BC3; Wed, 5 Dec 2018 14:46:06 +0000 (GMT) Date: Wed, 5 Dec 2018 14:46:06 +0000 From: Will Deacon To: Christoph Hellwig Cc: Robin Murphy , Nicolas Boichat , Joerg Roedel , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Michal Hocko , Mel Gorman , Levin Alexander , Huaisheng Ye , Mike Rapoport , linux-arm-kernel@lists.infradead.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Yong Wu , Matthias Brugger , Tomasz Figa , yingjoe.chen@mediatek.com, Matthew Wilcox Subject: Re: [PATCH v4 3/3] iommu/io-pgtable-arm-v7s: Request DMA32 memory, and improve debugging Message-ID: <20181205144605.GA16171@arm.com> References: <20181205054828.183476-1-drinkcat@chromium.org> <20181205054828.183476-4-drinkcat@chromium.org> <20181205135406.GA29031@infradead.org> <1d211576-9153-cca1-5cd0-8c9881bd3fa4@arm.com> <20181205144308.GA28409@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181205144308.GA28409@infradead.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 05, 2018 at 06:43:08AM -0800, Christoph Hellwig wrote: > On Wed, Dec 05, 2018 at 02:40:06PM +0000, Robin Murphy wrote: > > 32-bit Arm doesn't have ZONE_DMA32, but has (or at least had at the time) a > > 2GB ZONE_DMA. Whether we actually need that or not depends on how this all > > interacts with LPAE and highmem, but I'm not sure of those details off-hand. > > Well, arm32 can't address more than 32-bits in the linear kernel > mapping, so GFP_KERNEL should be perfectly fine there if the limit > really is 32-bits and not 31 or smaller because someone stole a bit > or two somewhere. I'm not sure that's necessarily true on the physical side. Wasn't there a keystone SoC with /all/ the coherent memory above 4GB? Will