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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,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 ED5BCC43461 for ; Wed, 16 Sep 2020 22:08:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B04C7206CA for ; Wed, 16 Sep 2020 22:08:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726435AbgIPWIF (ORCPT ); Wed, 16 Sep 2020 18:08:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47958 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726321AbgIPWH7 (ORCPT ); Wed, 16 Sep 2020 18:07:59 -0400 Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3E1D3C0698D0; Wed, 16 Sep 2020 14:59:55 -0700 (PDT) Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: gtucker) with ESMTPSA id 5C3D229BBA2 Subject: Re: [PATCH] cma: make number of CMA areas dynamic, remove CONFIG_CMA_AREAS To: Mike Kravetz , "Song Bao Hua (Barry Song)" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-mips@vger.kernel.org" Cc: Aslan Bakirov , Joonsoo Kim , Rik van Riel , Michal Hocko , Andrew Morton , Will Deacon , Roman Gushchin , Mike Rapoport , kernelci-results@groups.io References: <20200915205703.34572-1-mike.kravetz@oracle.com> <4b7b14c9eb6a42509f8324f7ed84b46f@hisilicon.com> <2bf99eee-29b1-4965-da7d-d4e341803440@oracle.com> From: Guillaume Tucker Message-ID: <70ad632d-88f3-db6d-3493-b09451150298@collabora.com> Date: Wed, 16 Sep 2020 22:59:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <2bf99eee-29b1-4965-da7d-d4e341803440@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/09/2020 17:30, Mike Kravetz wrote: > On 9/16/20 2:14 AM, Song Bao Hua (Barry Song) wrote: >>>> -----Original Message----- >>>> From: Mike Kravetz [mailto:mike.kravetz@oracle.com] >>>> Sent: Wednesday, September 16, 2020 8:57 AM >>>> To: linux-mm@kvack.org; linux-kernel@vger.kernel.org; >>>> linux-arm-kernel@lists.infradead.org; linux-mips@vger.kernel.org >>>> Cc: Roman Gushchin ; Song Bao Hua (Barry Song) >>>> ; Mike Rapoport ; Joonsoo >>>> Kim ; Rik van Riel ; Aslan Bakirov >>>> ; Michal Hocko ; Andrew Morton >>>> ; Mike Kravetz >>>> Subject: [PATCH] cma: make number of CMA areas dynamic, remove >>>> CONFIG_CMA_AREAS >>>> >>>> The number of distinct CMA areas is limited by the constant >>>> CONFIG_CMA_AREAS. In most environments, this was set to a default >>>> value of 7. Not too long ago, support was added to allocate hugetlb >>>> gigantic pages from CMA. More recent changes to make >>> dma_alloc_coherent >>>> NUMA-aware on arm64 added more potential users of CMA areas. Along >>>> with the dma_alloc_coherent changes, the default value of CMA_AREAS >>>> was bumped up to 19 if NUMA is enabled. >>>> >>>> It seems that the number of CMA users is likely to grow. Instead of >>>> using a static array for cma areas, use a simple linked list. These >>>> areas are used before normal memory allocators, so use the memblock >>>> allocator. >>>> >>>> Acked-by: Roman Gushchin >>>> Signed-off-by: Mike Kravetz >>>> --- >>>> rfc->v1 >>>> - Made minor changes suggested by Song Bao Hua (Barry Song) >>>> - Removed check for late calls to cma_init_reserved_mem that was part >>>> of RFC. >>>> - Added ACK from Roman Gushchin >>>> - Still in need of arm testing >>> >>> Unfortunately, the test result on my arm64 board is negative, Linux can't boot >>> after applying >>> this patch. >>> >>> I guess we have to hold on this patch for a while till this is fixed. BTW, Mike, do >>> you have >>> a qemu-based arm64 numa system to debug? It is very easy to reproduce, we >>> don't need to >>> use hugetlb_cma and pernuma_cma. Just the default cma will make the boot >>> hang. >> >> Hi Mike, >> I spent some time on debugging the boot issue and sent a patch here: >> https://lore.kernel.org/linux-mm/20200916085933.25220-1-song.bao.hua@hisilicon.com/ >> All details and knic oops can be found there. >> pls feel free to merge my patch into your v2 if you want. And we probably need ack from >> arm maintainers. >> >> Also, +Will, >> >> Hi Will, the whole story is that Mike tried to remove the cma array with CONFIG_CMA_AREAS >> and moved to use memblock_alloc() to allocate cma area, so that the number of cma areas >> could be dynamic. It turns out it causes a kernel panic on arm64 during system boot as the >> returned address from memblock_alloc is invalid before paging_init() is done on arm64. >> > > Thank you! > > Based on your analysis, I am concerned that other architectures may also > have issues. > > Andrew, > I suggest we remove this patch from your tree. I will audit all architectures > which enable CMA and look for similar issues there. Will then merge Barry's > patch into a V2 with any other arch specific changes. FYI This was also bisected on kernelci.org[1] and it landed on this commit: c999bd436fe9 ("mm/cma: make number of CMA areas dynamic, remove CONFIG_CMA_AREAS"). Only arm and arm64 seem to be affected, and not with all the builds: https://kernelci.org/test/job/next/branch/master/kernel/next-20200916/plan/baseline/ The list of failures above might help someone debug the issue with a platform they have at hand. Guillaume [1] https://groups.io/g/kernelci-results-staging/message/2027