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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3483C433EF for ; Tue, 22 Mar 2022 04:51:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236519AbiCVEwa (ORCPT ); Tue, 22 Mar 2022 00:52:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236495AbiCVEwV (ORCPT ); Tue, 22 Mar 2022 00:52:21 -0400 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 393FB107839 for ; Mon, 21 Mar 2022 21:50:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1647924653; x=1679460653; h=message-id:date:mime-version:cc:subject:to:references: from:in-reply-to:content-transfer-encoding; bh=cTZrAGX+t69jJcCH7JXAi2XQzqRxygaDZLgYJyVhgpM=; b=jh96nUWM1ZuuX6hfl63PEnyVzTQ4JdBl58x4pz3UgiTc/6KOcZ0DlcWc iKMmDtXx2qvGnhdmwWg/XEUx3wOhr50vDza6YqvV+mc5JdL7BMjyKG6vB 5HDzNPTKarvwMQC98BAalOP6O2sjtn/yK+vd1XDaDBmug+31ziAXBbtv5 ImfYVtFFI1tKIpOcJ9F/2cruF8arGxlEb+lOj1Iuxi1li00/utWNLlNOt j42VDlTY3U4r7DUvFhYAuJfIi7AYw5S4bi6GqgEaInweA/zHBeGmgUaNE VtM5mTSFp+6ibyvkF/e1YtcjLGeQ4laK9EjVSOcZwxN5kKSczs24LyUQV Q==; X-IronPort-AV: E=McAfee;i="6200,9189,10293"; a="256542391" X-IronPort-AV: E=Sophos;i="5.90,200,1643702400"; d="scan'208";a="256542391" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Mar 2022 21:50:52 -0700 X-IronPort-AV: E=Sophos;i="5.90,200,1643702400"; d="scan'208";a="518724693" Received: from blu2-mobl3.ccr.corp.intel.com (HELO [10.254.209.186]) ([10.254.209.186]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Mar 2022 21:50:47 -0700 Message-ID: <966d28f6-3b87-45c5-e758-f38eb339e3c6@linux.intel.com> Date: Tue, 22 Mar 2022 12:50:45 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Cc: baolu.lu@linux.intel.com, Joerg Roedel , Christoph Hellwig , Kevin Tian , Ashok Raj , Will Deacon , Robin Murphy , Jean-Philippe Brucker , Eric Auger , Liu Yi L , Jacob jun Pan , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC 09/11] iommu: Add iommu_get_domain_for_dev_pasid() Content-Language: en-US To: Jason Gunthorpe References: <20220320064030.2936936-1-baolu.lu@linux.intel.com> <20220320064030.2936936-10-baolu.lu@linux.intel.com> <20220321124058.GO11336@nvidia.com> From: Lu Baolu In-Reply-To: <20220321124058.GO11336@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/3/21 20:40, Jason Gunthorpe wrote: > On Sun, Mar 20, 2022 at 02:40:28PM +0800, Lu Baolu wrote: >> @@ -3098,7 +3101,16 @@ int iommu_attach_device_pasid(struct iommu_domain *domain, >> if (iommu_group_device_count(group) != 1) >> goto out_unlock; >> >> + xa_lock(&group->pasid_array); >> + curr = __xa_cmpxchg(&group->pasid_array, pasid, NULL, >> + domain, GFP_KERNEL); >> + xa_unlock(&group->pasid_array); >> + if (curr) > > curr can be an xa_err that should be propogated. Yes, should check xa_err(). > >> + goto out_unlock; >> + >> ret = domain->ops->attach_dev_pasid(domain, dev, pasid); >> + if (ret) >> + xa_erase(&group->pasid_array, pasid); >> >> out_unlock: >> mutex_unlock(&group->mutex); >> @@ -3118,6 +3130,25 @@ void iommu_detach_device_pasid(struct iommu_domain *domain, >> >> mutex_lock(&group->mutex); >> domain->ops->detach_dev_pasid(domain, dev, pasid); >> + xa_erase(&group->pasid_array, pasid); >> + mutex_unlock(&group->mutex); >> + iommu_group_put(group); >> +} >> + >> +struct iommu_domain * >> +iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid) >> +{ >> + struct iommu_domain *domain; >> + struct iommu_group *group; >> + >> + group = iommu_group_get(dev); >> + if (!group) >> + return NULL; >> + >> + mutex_lock(&group->mutex); >> + domain = xa_load(&group->pasid_array, pasid); >> mutex_unlock(&group->mutex); >> iommu_group_put(group); > > This whole API seems sketchy - what is the lifecycle of the returned > iommu_domain and what prevents it from being concurrently freed after > unlocking? Agreed. The domain could be used in page fault handling thread, hence need a mechanism to guarantee the concurrence. Best regards, baolu