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=-13.0 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 CCB76C433E1 for ; Mon, 3 Aug 2020 02:20:35 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (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 A5A3E20722 for ; Mon, 3 Aug 2020 02:20:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A5A3E20722 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 silver.osuosl.org (Postfix) with ESMTP id D23CC20485; Mon, 3 Aug 2020 02:20:35 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ZZEyOX4qlLBR; Mon, 3 Aug 2020 02:20:34 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by silver.osuosl.org (Postfix) with ESMTP id 5C9BE203FA; Mon, 3 Aug 2020 02:20:34 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 413FBC0051; Mon, 3 Aug 2020 02:20:34 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 60BE7C004C for ; Mon, 3 Aug 2020 02:20:32 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 4E85C87B60 for ; Mon, 3 Aug 2020 02:20:32 +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 kbkM+NoVRlmb for ; Mon, 3 Aug 2020 02:20:31 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by hemlock.osuosl.org (Postfix) with ESMTPS id 026AC87B59 for ; Mon, 3 Aug 2020 02:20:30 +0000 (UTC) IronPort-SDR: OPM4goDuSmqAn2loN+yCx+hVn60OTYEW2ISMyCGmRYiYFEWBP6R6TUGqqiGfMmDiljzEBzyIpL /ovjFq+TbrMA== X-IronPort-AV: E=McAfee;i="6000,8403,9701"; a="153240894" X-IronPort-AV: E=Sophos;i="5.75,428,1589266800"; d="scan'208";a="153240894" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Aug 2020 19:20:29 -0700 IronPort-SDR: qBWMv2KDbNwROoK6QxaoQTKg3p7yCiwqOsxCFMDmeLzSALxSB3YfchntlexrlpC10igfhQ/2Jw Jb+scsqpJqsQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,428,1589266800"; d="scan'208";a="395909209" Received: from allen-box.sh.intel.com (HELO [10.239.159.139]) ([10.239.159.139]) by fmsmga001.fm.intel.com with ESMTP; 02 Aug 2020 19:20:26 -0700 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> <06fd91c1-a978-d526-7e2b-fec619a458e4@linux.intel.com> <20200731121418.0274afb8@x1.home> From: Lu Baolu Message-ID: <3fd171a2-a5cc-89d7-f539-04eb2faf130f@linux.intel.com> Date: Mon, 3 Aug 2020 10:15:27 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200731121418.0274afb8@x1.home> Content-Language: en-US Cc: Jean-Philippe Brucker , Kevin Tian , Dave Jiang , Ashok Raj , kvm@vger.kernel.org, Cornelia Huck , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Robin Murphy 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 Alex, On 8/1/20 2:14 AM, Alex Williamson wrote: > On Fri, 31 Jul 2020 14:30:03 +0800 > Lu Baolu wrote: > >> 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/ > > Yep, I thought that was a bit of a leap in logic. > >> 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. > > I think it could work either way, we could have an > iommu_get_aux_domain_for_dev() which returns NULL if the domain is not > an aux domain, or we could use iommu_get_domain_for_dev() and the > caller could test the domain with iommu_is_aux_domain() if they need to > confirm if it's an aux domain. The former could even be written using > the latter, a wrapper of iommu_get_domain_for_dev() that checks aux > property before returning. Okay. So iommu_get_domain_for_dev() and iommu_is_aux_domain() are what we wanted. The iommu_get_domain_for_dev() could be a simple wrapper of them. Thanks a lot for the guide. I will implement a new version according to the feedbacks. Best regards, baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu