From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lu Baolu Subject: Re: [PATCH v3 02/10] swiotlb: Factor out slot allocation and free Date: Mon, 29 Apr 2019 13:10:17 +0800 Message-ID: <93b3d627-782d-cae0-2175-77a5a8b3fe6e@linux.intel.com> References: <20190421011719.14909-1-baolu.lu@linux.intel.com> <20190421011719.14909-3-baolu.lu@linux.intel.com> <20190422164555.GA31181@lst.de> <0c6e5983-312b-0d6b-92f5-64861cd6804d@linux.intel.com> <20190423061232.GB12762@lst.de> <20190424144532.GA21480@lst.de> <20190426150433.GA19930@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190426150433.GA19930@lst.de> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Christoph Hellwig 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, Konrad Rzeszutek Wilk , Marek Szyprowski , Robin Murphy , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org List-Id: iommu@lists.linux-foundation.org Hi Christoph, On 4/26/19 11:04 PM, Christoph Hellwig wrote: > On Thu, Apr 25, 2019 at 10:07:19AM +0800, Lu Baolu wrote: >> This is not VT-d specific. It's just how generic IOMMU works. >> >> Normally, IOMMU works in paging mode. So if a driver issues DMA with >> IOVA 0xAAAA0123, IOMMU can remap it with a physical address 0xBBBB0123. >> But we should never expect IOMMU to remap 0xAAAA0123 with physical >> address of 0xBBBB0000. That's the reason why I said that IOMMU will not >> work there. > > Well, with the iommu it doesn't happen. With swiotlb it obviosuly > can happen, so drivers are fine with it. Why would that suddenly > become an issue when swiotlb is called from the iommu code? > I would say IOMMU is DMA remapping, not DMA engine. :-) Best regards, Lu Baolu 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,URIBL_BLOCKED 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 9A615C43219 for ; Mon, 29 Apr 2019 05:18:39 +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 5FCD42075E for ; Mon, 29 Apr 2019 05:18:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5FCD42075E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com 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 1171B1DED; Mon, 29 Apr 2019 05:18:39 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 9E2CB1DE7 for ; Mon, 29 Apr 2019 05:16:38 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 24E05608 for ; Mon, 29 Apr 2019 05:16:38 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Apr 2019 22:16:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,408,1549958400"; d="scan'208";a="295363562" Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by orsmga004.jf.intel.com with ESMTP; 28 Apr 2019 22:16:34 -0700 Subject: Re: [PATCH v3 02/10] swiotlb: Factor out slot allocation and free To: Christoph Hellwig References: <20190421011719.14909-1-baolu.lu@linux.intel.com> <20190421011719.14909-3-baolu.lu@linux.intel.com> <20190422164555.GA31181@lst.de> <0c6e5983-312b-0d6b-92f5-64861cd6804d@linux.intel.com> <20190423061232.GB12762@lst.de> <20190424144532.GA21480@lst.de> <20190426150433.GA19930@lst.de> From: Lu Baolu Message-ID: <93b3d627-782d-cae0-2175-77a5a8b3fe6e@linux.intel.com> Date: Mon, 29 Apr 2019 13:10:17 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190426150433.GA19930@lst.de> Content-Language: en-US Cc: kevin.tian@intel.com, mika.westerberg@linux.intel.com, ashok.raj@intel.com, Konrad Rzeszutek Wilk , alan.cox@intel.com, Robin Murphy , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, pengfei.xu@intel.com, jacob.jun.pan@intel.com, David Woodhouse 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="UTF-8"; format="flowed" Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org Message-ID: <20190429051017._D5YTuRjhzfKEKNHcUVys6qIec9p8q3kTxDEEntel2w@z> Hi Christoph, On 4/26/19 11:04 PM, Christoph Hellwig wrote: > On Thu, Apr 25, 2019 at 10:07:19AM +0800, Lu Baolu wrote: >> This is not VT-d specific. It's just how generic IOMMU works. >> >> Normally, IOMMU works in paging mode. So if a driver issues DMA with >> IOVA 0xAAAA0123, IOMMU can remap it with a physical address 0xBBBB0123. >> But we should never expect IOMMU to remap 0xAAAA0123 with physical >> address of 0xBBBB0000. That's the reason why I said that IOMMU will not >> work there. > > Well, with the iommu it doesn't happen. With swiotlb it obviosuly > can happen, so drivers are fine with it. Why would that suddenly > become an issue when swiotlb is called from the iommu code? > I would say IOMMU is DMA remapping, not DMA engine. :-) Best regards, Lu Baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu