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 2B053C43381 for ; Wed, 20 Mar 2019 01:32:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ECFF720835 for ; Wed, 20 Mar 2019 01:32:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727411AbfCTBcc (ORCPT ); Tue, 19 Mar 2019 21:32:32 -0400 Received: from mga04.intel.com ([192.55.52.120]:47656 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726686AbfCTBcc (ORCPT ); Tue, 19 Mar 2019 21:32:32 -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 fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Mar 2019 18:32:31 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,246,1549958400"; d="scan'208";a="128456918" 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 18:32:29 -0700 Cc: baolu.lu@linux.intel.com, iommu@lists.linux-foundation.org, Tom Murphy , Dmitry Safonov , Jacob Pan , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/7] iommu/vt-d: Fix-up device-domain relationship by refactoring to use iommu group default domain. To: James Sewart References: <0F0C82BE-86E5-4BAC-938C-6F7629E18D27@arista.com> <83B82113-8AE5-4B0C-A079-F389520525BD@arista.com> <0e74cc54-bb90-a620-5763-466cb11aaef7@linux.intel.com> <94706334-3DE4-4964-8FDD-125C58D493A0@arista.com> From: Lu Baolu Message-ID: <418d1432-2036-3f6f-48de-77005807e350@linux.intel.com> Date: Wed, 20 Mar 2019 09:26:59 +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: <94706334-3DE4-4964-8FDD-125C58D493A0@arista.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi James, On 3/19/19 9:35 PM, James Sewart wrote: > Hey Lu, > >> On 15 Mar 2019, at 03:13, Lu Baolu wrote: >> >> Hi James, >> >> On 3/14/19 7:56 PM, James Sewart wrote: >>> Patches 1 and 2 are the same as v1. >>> v1-v2: >>> Refactored ISA direct mappings to be returned by iommu_get_resv_regions. >>> Integrated patch by Lu to defer turning on DMAR until iommu.c has mapped >>> reserved regions. >>> Integrated patches by Lu to remove more unused code in cleanup. >>> Lu: I didn't integrate your patch to set the default domain type as it >>> isn't directly related to the aim of this patchset. Instead patch 4 >> >> Without those patches, user experience will be affected and some devices >> will not work on Intel platforms anymore. >> >> For a long time, Intel IOMMU driver has its own logic to determine >> whether a device requires an identity domain. For example, when user >> specifies "iommu=pt" in kernel parameter, all device will be attached >> with the identity domain. Further more, some quirky devices require >> an identity domain to be used before enabling DMA remapping, otherwise, >> it will not work. This was done by adding quirk bits in Intel IOMMU >> driver. >> >> So from my point of view, one way is porting all those quirks and kernel >> parameters into IOMMU generic layer, or opening a door for vendor IOMMU >> driver to determine the default domain type by their own. I prefer the >> latter option since it will not impact any behaviors on other >> architectures. > > I see your point. I’m not confident that using the proposed door to set a > groups default domain has the desired behaviour. As discussed before the > default domain type will be set based on the desired type for only the > first device attached to a group. I think to change the default domain > type you would need a slightly different door that wasn’t conditioned on > device. I think this as another problem. Just a summarize for the ease of discussion. We saw two problems: 1. When allocating a new group for a device, how should we determine the type of the default domain? This is what my proposal patches trying to address. 2. If we need to put a device into an existing group which uses a different type of domain from what the device desires to use, we might break the functionality of the device. For this problem I'd second your proposal below if I get your point correctly. > > For situations where individual devices require an identity domain because > of quirks then maybe calling is_identity_map per device in > iommu_group_get_for_dev is a better solution than the one I proposed. > Do you mean if we see a quirky device requires a different domain type other than the default domain type of the group, we will assign a new group to it? That looks good to me as far as I can see. I suppose this should be done in vt-d's ops callback. Best regards, Lu Baolu