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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 A803CC3A589 for ; Fri, 16 Aug 2019 02:46:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 840BD206C2 for ; Fri, 16 Aug 2019 02:46:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726636AbfHPCqV (ORCPT ); Thu, 15 Aug 2019 22:46:21 -0400 Received: from mga05.intel.com ([192.55.52.43]:31494 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726434AbfHPCqV (ORCPT ); Thu, 15 Aug 2019 22:46:21 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 15 Aug 2019 19:46:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,391,1559545200"; d="scan'208";a="171292545" Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by orsmga008.jf.intel.com with ESMTP; 15 Aug 2019 19:46:15 -0700 Cc: baolu.lu@linux.intel.com, David Woodhouse , Bjorn Helgaas , Christoph Hellwig , ashok.raj@intel.com, jacob.jun.pan@intel.com, alan.cox@intel.com, kevin.tian@intel.com, mika.westerberg@linux.intel.com, Ingo Molnar , Greg Kroah-Hartman , pengfei.xu@intel.com, Konrad Rzeszutek Wilk , Marek Szyprowski , Robin Murphy , Jonathan Corbet , Boris Ostrovsky , Juergen Gross , Stefano Stabellini , Steven Rostedt , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Jacob Pan , Alan Cox , Mika Westerberg Subject: Re: [PATCH v6 5/8] iommu: Add bounce page APIs To: Joerg Roedel References: <20190730045229.3826-1-baolu.lu@linux.intel.com> <20190730045229.3826-6-baolu.lu@linux.intel.com> <20190814083842.GB22669@8bytes.org> <445624e7-eb57-8089-8eb3-8687a65b1258@linux.intel.com> <20190815154845.GA18327@8bytes.org> From: Lu Baolu Message-ID: Date: Fri, 16 Aug 2019 10:45:13 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190815154845.GA18327@8bytes.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Joerg, On 8/15/19 11:48 PM, Joerg Roedel wrote: > On Thu, Aug 15, 2019 at 02:15:32PM +0800, Lu Baolu wrote: >> iommu_map/unmap() APIs haven't parameters for dma direction and >> attributions. These parameters are elementary for DMA APIs. Say, >> after map, if the dma direction is TO_DEVICE and a bounce buffer is >> used, we must sync the data from the original dma buffer to the bounce >> buffer; In the opposite direction, if dma is FROM_DEVICE, before unmap, >> we need to sync the data from the bounce buffer onto the original >> buffer. > > The DMA direction from DMA-API maps to the protections in iommu_map(): > > DMA_FROM_DEVICE: IOMMU_WRITE > DMA_TO_DEVICE: IOMMU_READ > DMA_BIDIRECTIONAL IOMMU_READ | IOMMU_WRITE > > And for the sync DMA-API also has separate functions for either > direction. So I don't see why these extra functions are needed in the > IOMMU-API. > Okay. I understand that adding these APIs in iommu.c is not a good idea. And, I also don't think merging the bounce buffer implementation into iommu_map() is feasible since iommu_map() is not DMA API centric. The bounce buffer implementation will eventually be part of DMA APIs defined in dma-iommu.c, but currently those APIs are not ready for x86 use yet. So I will put them in iommu/vt-d driver for this time being and will move them to dma-iommu.c later. Does this work for you? Best regards, Lu Baolu