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=-12.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 5A6DEC433E1 for ; Fri, 31 Jul 2020 06:30:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 445C5208E4 for ; Fri, 31 Jul 2020 06:30:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731398AbgGaGaN (ORCPT ); Fri, 31 Jul 2020 02:30:13 -0400 Received: from mga04.intel.com ([192.55.52.120]:4982 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731351AbgGaGaM (ORCPT ); Fri, 31 Jul 2020 02:30:12 -0400 IronPort-SDR: 8HyRPrYh1AVKywSXyjvIpkuHMZ3NFqTzfjFtBI+PG/9qPh11XTP0NAasCj7/4tn57O838F0UvK +kom63vbr/7g== X-IronPort-AV: E=McAfee;i="6000,8403,9698"; a="149203168" X-IronPort-AV: E=Sophos;i="5.75,417,1589266800"; d="scan'208";a="149203168" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Jul 2020 23:30:08 -0700 IronPort-SDR: zX0i7UjX9khEP8dd1fClb0ZgGv4jktjUAWeeAPNWqdnllhKOSoYF4zKfKXMGsBk6HaRnhUzDgA XHE5s3SdIx7g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,417,1589266800"; d="scan'208";a="321320272" Received: from daisygao-mobl.ccr.corp.intel.com (HELO [10.254.211.68]) ([10.254.211.68]) by orsmga008.jf.intel.com with ESMTP; 30 Jul 2020 23:30:04 -0700 Cc: baolu.lu@linux.intel.com, Joerg Roedel , Robin Murphy , Jean-Philippe Brucker , Cornelia Huck , Kevin Tian , Ashok Raj , Dave Jiang , Liu Yi L , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH v3 3/4] iommu: Add iommu_aux_get_domain_for_dev() To: Alex Williamson References: <20200714055703.5510-1-baolu.lu@linux.intel.com> <20200714055703.5510-4-baolu.lu@linux.intel.com> <20200729142507.182cd18a@x1.home> From: Lu Baolu Message-ID: <06fd91c1-a978-d526-7e2b-fec619a458e4@linux.intel.com> Date: Fri, 31 Jul 2020 14:30:03 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200729142507.182cd18a@x1.home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Alex, On 2020/7/30 4:25, Alex Williamson wrote: > On Tue, 14 Jul 2020 13:57:02 +0800 > Lu Baolu wrote: > >> The device driver needs an API to get its aux-domain. A typical usage >> scenario is: >> >> unsigned long pasid; >> struct iommu_domain *domain; >> struct device *dev = mdev_dev(mdev); >> struct device *iommu_device = vfio_mdev_get_iommu_device(dev); >> >> domain = iommu_aux_get_domain_for_dev(dev); >> if (!domain) >> return -ENODEV; >> >> pasid = iommu_aux_get_pasid(domain, iommu_device); >> if (pasid <= 0) >> return -EINVAL; >> >> /* Program the device context */ >> .... >> >> This adds an API for such use case. >> >> Suggested-by: Alex Williamson >> Signed-off-by: Lu Baolu >> --- >> drivers/iommu/iommu.c | 18 ++++++++++++++++++ >> include/linux/iommu.h | 7 +++++++ >> 2 files changed, 25 insertions(+) >> >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c >> index cad5a19ebf22..434bf42b6b9b 100644 >> --- a/drivers/iommu/iommu.c >> +++ b/drivers/iommu/iommu.c >> @@ -2817,6 +2817,24 @@ void iommu_aux_detach_group(struct iommu_domain *domain, >> } >> EXPORT_SYMBOL_GPL(iommu_aux_detach_group); >> >> +struct iommu_domain *iommu_aux_get_domain_for_dev(struct device *dev) >> +{ >> + struct iommu_domain *domain = NULL; >> + struct iommu_group *group; >> + >> + group = iommu_group_get(dev); >> + if (!group) >> + return NULL; >> + >> + if (group->aux_domain_attached) >> + domain = group->domain; > Why wouldn't the aux domain flag be on the domain itself rather than > the group? Then if we wanted sanity checking in patch 1/ we'd only > need to test the flag on the object we're provided. Agreed. Given that a group may contain both non-aux and aux devices, adding such flag in iommu_group doesn't make sense. > > If we had such a flag, we could create an iommu_domain_is_aux() > function and then simply use iommu_get_domain_for_dev() and test that > it's an aux domain in the example use case. It seems like that would > resolve the jump from a domain to an aux-domain just as well as adding > this separate iommu_aux_get_domain_for_dev() interface. The is_aux > test might also be useful in other cases too. Let's rehearsal our use case. unsigned long pasid; struct iommu_domain *domain; struct device *dev = mdev_dev(mdev); struct device *iommu_device = vfio_mdev_get_iommu_device(dev); [1] domain = iommu_get_domain_for_dev(dev); if (!domain) return -ENODEV; [2] pasid = iommu_aux_get_pasid(domain, iommu_device); if (pasid <= 0) return -EINVAL; /* Program the device context */ .... The reason why I add this iommu_aux_get_domain_for_dev() is that we need to make sure the domain got at [1] is valid to be used at [2]. https://lore.kernel.org/linux-iommu/20200707150408.474d81f1@x1.home/ When calling into iommu_aux_get_pasid(), the iommu driver should make sure that @domain is a valid aux-domain for @iommu_device. Hence, for our use case, it seems that there's no need for a is_aux_domain() api. Anyway, I'm not against adding a new is_aux_domain() api if there's a need elsewhere. Best regards, baolu