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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 B3165C43381 for ; Tue, 19 Mar 2019 08:05:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8FF31213F2 for ; Tue, 19 Mar 2019 08:05:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727530AbfCSIFW (ORCPT ); Tue, 19 Mar 2019 04:05:22 -0400 Received: from mga07.intel.com ([134.134.136.100]:43610 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726910AbfCSIFV (ORCPT ); Tue, 19 Mar 2019 04:05:21 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Mar 2019 01:05:21 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,497,1544515200"; d="scan'208";a="128201049" Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by orsmga006.jf.intel.com with ESMTP; 19 Mar 2019 01:05:18 -0700 Cc: baolu.lu@linux.intel.com, David Woodhouse , Joerg Roedel , ashok.raj@intel.com, jacob.jun.pan@intel.com, alan.cox@intel.com, kevin.tian@intel.com, mika.westerberg@linux.intel.com, pengfei.xu@intel.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Jacob Pan Subject: Re: [PATCH v1 4/9] iommu/vt-d: Add bounce buffer API for domain map/unmap To: Christoph Hellwig References: <20190312060005.12189-1-baolu.lu@linux.intel.com> <20190312060005.12189-5-baolu.lu@linux.intel.com> <20190312163845.GA13141@infradead.org> <20190313161029.GA23513@infradead.org> From: Lu Baolu Message-ID: Date: Tue, 19 Mar 2019 15:59:48 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190313161029.GA23513@infradead.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 Christoph, On 3/14/19 12:10 AM, Christoph Hellwig wrote: > On Wed, Mar 13, 2019 at 10:31:52AM +0800, Lu Baolu wrote: >> Hi again, >> >> On 3/13/19 10:04 AM, Lu Baolu wrote: >>> Hi, >>> >>> On 3/13/19 12:38 AM, Christoph Hellwig wrote: >>>> On Tue, Mar 12, 2019 at 02:00:00PM +0800, Lu Baolu wrote: >>>>> This adds the APIs for bounce buffer specified domain >>>>> map() and unmap(). The start and end partial pages will >>>>> be mapped with bounce buffered pages instead. This will >>>>> enhance the security of DMA buffer by isolating the DMA >>>>> attacks from malicious devices. >>>> >>>> Please reuse the swiotlb code instead of reinventing it. >>>> >> >> Just looked into the code again. At least we could reuse below >> functions: >> >> swiotlb_tbl_map_single() >> swiotlb_tbl_unmap_single() >> swiotlb_tbl_sync_single() >> >> Anything else? > > Yes, that is probably about the level you want to reuse, given that the > next higher layer already has hooks into the direct mapping code. > I am trying to change my code to reuse swiotlb. But I found that swiotlb might not be suitable for my case. Below is what I got with swiotlb_map(): phy_addr size tlb_addr -------------------------------- 0x167eec330 0x8 0x85dc6000 0x167eef5c0 0x40 0x85dc6800 0x167eec330 0x8 0x85dc7000 0x167eef5c0 0x40 0x85dc7800 But what I expected to get is: phy_addr size tlb_addr -------------------------------- 0x167eec330 0x8 0xAAAAA330 0x167eef5c0 0x40 0xBBBBB5c0 0x167eec330 0x8 0xCCCCC330 0x167eef5c0 0x40 0xDDDDD5c0 , where 0xXXXXXX000 is the physical address of a bounced page. Basically, I want a bounce page to replace a leaf page in the vt-d page table, which maps a buffer with size less than a PAGE_SIZE. Best regards, Lu Baolu