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 21C52C10F25 for ; Sun, 8 Mar 2020 02:15:59 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (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 E7E5A20409 for ; Sun, 8 Mar 2020 02:15:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E7E5A20409 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 localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id CBA648863B; Sun, 8 Mar 2020 02:15:58 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 9rsnIfPMkoU6; Sun, 8 Mar 2020 02:15:56 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id 9103888630; Sun, 8 Mar 2020 02:15:56 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 8232AC18D3; Sun, 8 Mar 2020 02:15:56 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id E5110C013E for ; Sun, 8 Mar 2020 02:15:54 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id CCC4087D3B for ; Sun, 8 Mar 2020 02:15:54 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id mky3g-9cTDvL for ; Sun, 8 Mar 2020 02:15:54 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by whitealder.osuosl.org (Postfix) with ESMTPS id 1A59F87C16 for ; Sun, 8 Mar 2020 02:15:54 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Mar 2020 18:15:53 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,528,1574150400"; d="scan'208";a="414404843" Received: from blu2-mobl3.ccr.corp.intel.com (HELO [10.254.211.93]) ([10.254.211.93]) by orsmga005.jf.intel.com with ESMTP; 07 Mar 2020 18:15:49 -0800 Subject: Re: [PATCH 3/6] iommu/vt-d: Don't force 32bit devices to uses DMA domain To: Christoph Hellwig References: <20200307062014.3288-1-baolu.lu@linux.intel.com> <20200307062014.3288-4-baolu.lu@linux.intel.com> <20200307142144.GB26190@lst.de> From: Lu Baolu Message-ID: Date: Sun, 8 Mar 2020 10:15:48 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200307142144.GB26190@lst.de> Content-Language: en-US Cc: kevin.tian@intel.com, ashok.raj@intel.com, linux-kernel@vger.kernel.org, Daniel Drake , iommu@lists.linux-foundation.org, Robin Murphy , Derrick Jonathan X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 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" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" Hi Christoph, On 2020/3/7 22:21, Christoph Hellwig wrote: > On Sat, Mar 07, 2020 at 02:20:11PM +0800, Lu Baolu wrote: >> Currently, if a 32bit device initially uses an identity domain, >> Intel IOMMU driver will convert it forcibly to a DMA one if its >> address capability is not enough for the whole system memory. >> The motivation was to overcome the overhead caused by possible >> bounced buffer. >> >> Unfortunately, this improvement has led to many problems. For >> example, some 32bit devices are required to use an identity >> domain, forcing them to use DMA domain will cause the device >> not to work anymore. On the other hand, the VMD sub-devices >> share a domain but each sub-device might have different address >> capability. Forcing a VMD sub-device to use DMA domain blindly >> will impact the operation of other sub-devices without any >> notification. Further more, PCI aliased devices (PCI bridge >> and all devices beneath it, VMD devices and various devices >> quirked with pci_add_dma_alias()) must use the same domain. >> Forcing one device to switch to DMA domain during runtime >> will cause in-fligh DMAs for other devices to abort or target >> to other memory which might cause undefind system behavior. > > I still don't like the idea to enforce either a strict dynamic > IOMMU mapping or an identify mapping mode. > > Can we add a new AUTO domain which will allow using the identity > mapping when available? That somewhat matches the existing x86 > default, and also what powerpc does. Sai is proposing a series to change the default domain through sysfs during runtime. https://lore.kernel.org/linux-iommu/FFF73D592F13FD46B8700F0A279B802F4FBF7E4B@ORSMSX114.amr.corp.intel.com/T/#mb919da5567da7692ee7058a00a137145adf950a1 It has evolved into v2. Not sure whether it's what you want. > I have a series to lift > that bypass mode into the core dma-mapping code that I need > to repost, which I think would be suitable for intel-iommu as well. > Looking forward to your repost. Best regards, baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu