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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 A2C27C07E95 for ; Tue, 13 Jul 2021 13:27:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A5D36115B for ; Tue, 13 Jul 2021 13:27:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231654AbhGMNaH (ORCPT ); Tue, 13 Jul 2021 09:30:07 -0400 Received: from foss.arm.com ([217.140.110.172]:43432 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236222AbhGMNaG (ORCPT ); Tue, 13 Jul 2021 09:30:06 -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 3A9B31FB; Tue, 13 Jul 2021 06:27:16 -0700 (PDT) Received: from bogus (unknown [10.57.79.213]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CC7F03F694; Tue, 13 Jul 2021 06:27:14 -0700 (PDT) Date: Tue, 13 Jul 2021 14:26:12 +0100 From: Sudeep Holla To: Xiongfeng Wang Cc: gregkh@linuxfoundation.org, rafael@kernel.org, Sudeep Holla , linux-kernel@vger.kernel.org, james.morse@arm.com Subject: Re: [PATCH] cacheinfo: clear cache_leaves(cpu) in free_cache_attributes() Message-ID: <20210713132612.gvx7xpdp3tjcmxxu@bogus> References: <1626148058-55230-1-git-send-email-wangxiongfeng2@huawei.com> <20210713113315.thsvrvqvqptc7hje@bogus> <303cd2bf-7142-6ec9-548a-afe7f6e5ca8f@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <303cd2bf-7142-6ec9-548a-afe7f6e5ca8f@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 13, 2021 at 08:46:19PM +0800, Xiongfeng Wang wrote: > Hi Sudeep, > > On 2021/7/13 19:33, Sudeep Holla wrote: > > On Tue, Jul 13, 2021 at 11:47:38AM +0800, Xiongfeng Wang wrote: > >> On ARM64, when PPTT(Processor Properties Topology Table) is not > >> implemented in ACPI boot, we will goto 'free_ci' with the following > >> print: > >> Unable to detect cache hierarchy for CPU 0 > >> > > > > The change itself looks good and I am fine with that. However,... > > > >> But some other codes may still use 'num_leaves' to iterate through the > > > > Can you point me exactly where it is used to make sure there are no > > other issues associated with that. > > > >> 'info_list', such as get_cpu_cacheinfo_id(). If 'info_list' is NULL , it > >> would crash. So clear 'num_leaves' in free_cache_attributes(). > >> > > > > And can you provide the crash dump please ? If we are not hitting any > > issue and you just figured this with code inspection, that is fine. It > > helps to determine if this needs to be backport or just good to have > > clean up. > > There is no issue in the mainline kernel. get_cpu_cacheinfo_id() is only called > on x86. I didn't hit any issue using the mainline kernel. > Thanks for confirming. > Actually, it's our own code that crashed. My colleague Shaobo(CCed) tried to add > MPAM support on ARM64. His code called get_cpu_cacheinfo_id() and crashed when > PPTT is not implemented. Maybe he should check whether PPTT is implemented > before calling get_cpu_cacheinfo_id(), but we think it is also better to clear > cache_leaves(cpu) in free_cache_attributes(). > Sorry for not clearly expressed. > Thanks for detailed explanation. In this case I would drop the Fixes: tag as it is not fixing anything in the commit mentioned in the tag. Also not sure if we can tag this as fixes 709c4362725a ("cacheinfo: Move resctrl's get_cache_id() to the cacheinfo header file") as that is introducing the possible access that could crash. @James ? Anyways, irrespective of whether you add above tag, feel free to add once to drop the original fixes tag in the patch. Reviewed-by: Sudeep Holla -- Regards, Sudeep