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=-2.2 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 5C531C76191 for ; Thu, 25 Jul 2019 07:18:45 +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 3832E21734 for ; Thu, 25 Jul 2019 07:18:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3832E21734 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 E9D731640; Thu, 25 Jul 2019 07:18:44 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 2C9511615 for ; Thu, 25 Jul 2019 07:18:43 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id BD9F17C for ; Thu, 25 Jul 2019 07:18:42 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Jul 2019 00:18:42 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,305,1559545200"; d="scan'208";a="181373984" Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by orsmga002.jf.intel.com with ESMTP; 25 Jul 2019 00:18:37 -0700 Subject: Re: [PATCH v5 02/10] iommu/vt-d: Use per-device dma_ops To: Christoph Hellwig References: <20190725031717.32317-1-baolu.lu@linux.intel.com> <20190725031717.32317-3-baolu.lu@linux.intel.com> <20190725054413.GC24527@lst.de> From: Lu Baolu Message-ID: Date: Thu, 25 Jul 2019 15:18:03 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190725054413.GC24527@lst.de> Content-Language: en-US Cc: alan.cox@intel.com, Stefano Stabellini , ashok.raj@intel.com, Jonathan Corbet , pengfei.xu@intel.com, Ingo Molnar , David Woodhouse , kevin.tian@intel.com, Konrad Rzeszutek Wilk , Steven Rostedt , Bjorn Helgaas , Boris Ostrovsky , mika.westerberg@linux.intel.com, Juergen Gross , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, jacob.jun.pan@intel.com, Robin Murphy 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="us-ascii"; Format="flowed" Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org Hi Christoph, On 7/25/19 1:44 PM, Christoph Hellwig wrote: >> /* Check if the dev needs to go through non-identity map and unmap process.*/ >> static bool iommu_need_mapping(struct device *dev) >> { >> - int ret; >> - >> if (iommu_dummy(dev)) >> return false; >> >> - ret = identity_mapping(dev); >> - if (ret) { >> - u64 dma_mask = *dev->dma_mask; >> - >> - if (dev->coherent_dma_mask && dev->coherent_dma_mask < dma_mask) >> - dma_mask = dev->coherent_dma_mask; >> - >> - if (dma_mask >= dma_get_required_mask(dev)) >> - return false; > > Don't we need to keep this bit so that we still allow the IOMMU > to act if the device has a too small DMA mask to address all memory in > the system, even if if it should otherwise be identity mapped? > This checking happens only when device is using an identity mapped domain. If the device has a small DMA mask, swiotlb will be used for high memory access. This is supposed to be handled in dma_direct_map_page(): if (unlikely(!dma_direct_possible(dev, dma_addr, size)) && !swiotlb_map(dev, &phys, &dma_addr, size, dir, attrs)) { report_addr(dev, dma_addr, size); return DMA_MAPPING_ERROR; } Best regards, Baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu