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,URIBL_BLOCKED,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 CDD55C32771 for ; Tue, 21 Jan 2020 00:45:26 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 9BFDF24125 for ; Tue, 21 Jan 2020 00:45:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9BFDF24125 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 whitealder.osuosl.org (Postfix) with ESMTP id 67D1886072; Tue, 21 Jan 2020 00:45:26 +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 QmUQ2fOxDpZs; Tue, 21 Jan 2020 00:45:25 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by whitealder.osuosl.org (Postfix) with ESMTP id BCDDE855E1; Tue, 21 Jan 2020 00:45:25 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id AE11FC0178; Tue, 21 Jan 2020 00:45:25 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id C784FC0174 for ; Tue, 21 Jan 2020 00:45:24 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id C0D1986072 for ; Tue, 21 Jan 2020 00:45:24 +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 znu-ou9NTCtF for ; Tue, 21 Jan 2020 00:45:23 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by whitealder.osuosl.org (Postfix) with ESMTPS id 3086C855E1 for ; Tue, 21 Jan 2020 00:45:23 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Jan 2020 16:45:22 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,343,1574150400"; d="scan'208";a="215371656" Received: from allen-box.sh.intel.com (HELO [10.239.159.138]) ([10.239.159.138]) by orsmga007.jf.intel.com with ESMTP; 20 Jan 2020 16:45:20 -0800 Subject: Re: [RFC PATCH 0/4] iommu: Per-group default domain type To: John Garry , Joerg Roedel , Greg Kroah-Hartman , Bjorn Helgaas References: <20200101052648.14295-1-baolu.lu@linux.intel.com> From: Lu Baolu Message-ID: Date: Tue, 21 Jan 2020 08:43:52 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US Cc: kevin.tian@intel.com, ashok.raj@intel.com, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, jacob.jun.pan@intel.com, Robin Murphy , Christoph Hellwig 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 John, On 1/20/20 5:44 PM, John Garry wrote: > On 01/01/2020 05:26, Lu Baolu wrote: >> An IOMMU group represents the smallest set of devices that are considered >> to be isolated. All devices belonging to an IOMMU group share a default >> domain for DMA APIs. There are two types of default domain: >> IOMMU_DOMAIN_DMA >> and IOMMU_DOMAIN_IDENTITY. The former means IOMMU translation, while the >> latter means IOMMU by-pass. >> >> Currently, the default domain type for the IOMMU groups is determined >> globally. All IOMMU groups use a single default domain type. The global >> default domain type can be adjusted by kernel build configuration or >> kernel parameters. >> >> More and more users are looking forward to a fine grained default domain >> type. For example, with the global default domain type set to >> translation, >> the OEM verndors or end users might want some trusted and fast-speed >> devices >> to bypass IOMMU for performance gains. On the other hand, with global >> default domain type set to by-pass, some devices with limited system >> memory addressing capability might want IOMMU translation to remove the >> bounce buffer overhead. > > Hi Lu Baolu, > > Do you think that it would be a more common usecase to want > kernel-managed devices to be passthrough for performance reasons and > some select devices to be in DMA domain, like those with limited address > cap or whose drivers request huge amounts of memory? > > I just think it would be more manageable to set kernel commandline > parameters for this, i.e. those select few which want DMA domain. > It's just two sides of a coin. Currently, iommu subsystem make DMA domain by default, that's the reason why I selected to let user set which devices are willing to use identity domains. > Thanks, > John Best regards, baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu