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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,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 D3F0DC4338F for ; Mon, 2 Aug 2021 15:46:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AFAEA610FB for ; Mon, 2 Aug 2021 15:46:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235250AbhHBPqz (ORCPT ); Mon, 2 Aug 2021 11:46:55 -0400 Received: from foss.arm.com ([217.140.110.172]:37832 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234974AbhHBPqy (ORCPT ); Mon, 2 Aug 2021 11:46:54 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0119311D4; Mon, 2 Aug 2021 08:46:45 -0700 (PDT) Received: from [10.57.36.146] (unknown [10.57.36.146]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 074273F66F; Mon, 2 Aug 2021 08:46:43 -0700 (PDT) Subject: Re: [Patch V2 0/2] iommu/arm-smmu: Fix races in iommu domain/group creation To: Will Deacon , Ashish Mhetre Cc: vdumpa@nvidia.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <1623961837-12540-1-git-send-email-amhetre@nvidia.com> <20210802151607.GF28735@willie-the-truck> From: Robin Murphy Message-ID: <9c38c53c-c145-097a-4c7e-40f1c06a1f01@arm.com> Date: Mon, 2 Aug 2021 16:46:37 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210802151607.GF28735@willie-the-truck> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-08-02 16:16, Will Deacon wrote: > On Fri, Jun 18, 2021 at 02:00:35AM +0530, Ashish Mhetre wrote: >> Multiple iommu domains and iommu groups are getting created for the devices >> sharing same SID. It is expected for devices sharing same SID to be in same >> iommu group and same iommu domain. >> This is leading to context faults when one device is accessing IOVA from >> other device which shouldn't be the case for devices sharing same SID. >> Fix this by protecting iommu domain and iommu group creation with mutexes. > > Robin -- any chance you could take a look at these, please? You had some > comments on the first version which convinced me that they are needed, > but I couldn't tell whether you wanted to solve this a different way or not. Sorry, I was lamenting that this came to light due to the of_iommu_configure() flow being yucky, but that wasn't meant to imply that there aren't - or couldn't be in future - better reasons for iommu_probe_device() to be robust against concurrency anyway. I do think these are legitimate fixes to make in their own right, even if the current need might get swept back under the rug in future. I would say, however, that the commit messages seem to focus too much on the wrong details and aren't overly useful, and patch #2 is missing Ashish's sign-off. Thanks, Robin.