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=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 AE835C3F2CD for ; Mon, 23 Mar 2020 17:20:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F2952072D for ; Mon, 23 Mar 2020 17:20:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728078AbgCWRUV (ORCPT ); Mon, 23 Mar 2020 13:20:21 -0400 Received: from verein.lst.de ([213.95.11.211]:59637 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728088AbgCWRUR (ORCPT ); Mon, 23 Mar 2020 13:20:17 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id C11FA68BEB; Mon, 23 Mar 2020 18:20:14 +0100 (CET) Date: Mon, 23 Mar 2020 18:20:14 +0100 From: Christoph Hellwig To: Alexey Kardashevskiy Cc: Christoph Hellwig , iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, Lu Baolu , Greg Kroah-Hartman , Joerg Roedel , Robin Murphy , linux-kernel@vger.kernel.org, "Aneesh Kumar K.V" Subject: Re: [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device Message-ID: <20200323172014.GA31269@lst.de> References: <20200320141640.366360-1-hch@lst.de> <20200320141640.366360-2-hch@lst.de> <2f31d0dd-aa7e-8b76-c8a1-5759fda5afc9@ozlabs.ru> <20200323083705.GA31245@lst.de> <37ce1b7e-264d-292d-32b1-093b24b3525c@ozlabs.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <37ce1b7e-264d-292d-32b1-093b24b3525c@ozlabs.ru> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 23, 2020 at 07:58:01PM +1100, Alexey Kardashevskiy wrote: > >> 0x100.0000.0000 .. 0x101.0000.0000 > >> > >> 2x4G, each is 1TB aligned. And we can map directly only the first 4GB > >> (because of the maximum IOMMU table size) but not the other. And 1:1 on > >> that "pseries" is done with offset=0x0800.0000.0000.0000. > >> > >> So we want to check every bus address against dev->bus_dma_limit, not > >> dev->coherent_dma_mask. In the example above I'd set bus_dma_limit to > >> 0x0800.0001.0000.0000 and 1:1 mapping for the second 4GB would not be > >> tried. Does this sound reasonable? Thanks, > > > > bus_dma_limit is just another limiting factor applied on top of > > coherent_dma_mask or dma_mask respectively. > > This is not enough for the task: in my example, I'd set bus limit to > 0x0800.0001.0000.0000 but this would disable bypass for all RAM > addresses - the first and the second 4GB blocks. So what about something like the version here: http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dma-bypass.3