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 A17A0CCA482 for ; Wed, 8 Jun 2022 07:59:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231245AbiFHH7Z (ORCPT ); Wed, 8 Jun 2022 03:59:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232952AbiFHH6E (ORCPT ); Wed, 8 Jun 2022 03:58:04 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E76B1E2269; Wed, 8 Jun 2022 00:27:14 -0700 (PDT) Received: from dggpemm500021.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4LHzKy3CJYzYsQl; Wed, 8 Jun 2022 15:26:14 +0800 (CST) Received: from dggpemm500014.china.huawei.com (7.185.36.153) by dggpemm500021.china.huawei.com (7.185.36.109) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 8 Jun 2022 15:27:12 +0800 Received: from [10.174.178.120] (10.174.178.120) by dggpemm500014.china.huawei.com (7.185.36.153) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 8 Jun 2022 15:27:10 +0800 Message-ID: <29900b05-ec44-76a2-645a-22a13399d7fd@huawei.com> Date: Wed, 8 Jun 2022 15:27:09 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH v3 5/6] mm: Add mirror flag back on initrd memory To: , CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , References: <20220607093805.1354256-1-mawupeng1@huawei.com> <20220607093805.1354256-6-mawupeng1@huawei.com> <99900b31-2605-2c85-a1b7-9ef2666b58da@redhat.com> From: mawupeng In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.120] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500014.china.huawei.com (7.185.36.153) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org 在 2022/6/7 22:49, Ard Biesheuvel 写道: > On Tue, 7 Jun 2022 at 14:22, David Hildenbrand wrote: >> >> On 07.06.22 11:38, Wupeng Ma wrote: >>> From: Ma Wupeng >>> >>> Initrd memory will be removed and then added in arm64_memblock_init() and this >>> will cause it to lose all of its memblock flags. The lost of MEMBLOCK_MIRROR >>> flag will lead to error log printed by find_zone_movable_pfns_for_nodes if >>> the lower 4G range has some non-mirrored memory. >>> >>> In order to solve this problem, the lost MEMBLOCK_MIRROR flag will be >>> reinstalled if the origin memblock has this flag. >>> >>> Signed-off-by: Ma Wupeng >>> --- >>> arch/arm64/mm/init.c | 9 +++++++++ >>> include/linux/memblock.h | 1 + >>> mm/memblock.c | 20 ++++++++++++++++++++ >>> 3 files changed, 30 insertions(+) >>> >>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c >>> index 339ee84e5a61..11641f924d08 100644 >>> --- a/arch/arm64/mm/init.c >>> +++ b/arch/arm64/mm/init.c >>> @@ -350,9 +350,18 @@ void __init arm64_memblock_init(void) >>> "initrd not fully accessible via the linear mapping -- please check your bootloader ...\n")) { >>> phys_initrd_size = 0; >>> } else { >>> + int flags, ret; >>> + >>> + ret = memblock_get_flags(base, &flags); >>> + if (ret) >>> + flags = 0; >>> + >>> memblock_remove(base, size); /* clear MEMBLOCK_ flags */ >>> memblock_add(base, size); >>> memblock_reserve(base, size); >> >> Can you explain why we're removing+re-adding here exactly? Is it just to >> clear flags as the comment indicates? >> > > This should only happen if the placement of the initrd conflicts with > a mem= command line parameter or it is not covered by memblock for > some other reason. > > IOW, this should never happen, and if re-memblock_add'ing this memory > unconditionally is causing problems, we should fix that instead of > working around it. This will happen if we use initrdmem=3G,100M to reserve initrd memory below the 4G limit to test this scenario(just for testing, I have trouble to boot qemu with initrd enabled and memory below 4G are all mirror memory). Re-memblock_add'ing this memory unconditionally seems fine but clear all flags(especially MEMBLOCK_MIRROR) may lead to some error log. > >> If it's really just about clearing flags, I wonder if we rather want to >> have an interface that does exactly that, and hides the way this is >> actually implemented (obtain flags, remove, re-add ...), internally. >> >> But most probably there is more magic in the code and clearing flags >> isn't all it ends up doing. >> > > I don't remember exactly why we needed to clear the flags, but I think > it had to do with some corner case we hit when the initrd was > partially covered. If "mem=" is set in command line, memblock_mem_limit_remove_map() will remove all memory block without MEMBLOCK_NOMAP. Maybe this will bring the memory back if this initrd mem has the MEMBLOCK_NOMAP flag? The rfc version [1] introduce and use memblock_clear_nomap() to clear the MEMBLOCK_NOMAP of this initrd memblock. So maybe the usage of memblock_remove() is just to avoid introducing new function(memblock_clear_nomap)? Since commit 4c546b8a3469 ("memblock: add memblock_clear_nomap()") already introduced memblock_clear_nomap(). Can we use this to remove flag MEMBLOCK_NOMAP to solve this problem rather than bring flag MEMBLOCK_MIRROR back? [1] https://lore.kernel.org/linux-arm-kernel/20160202180622.GP10166@arm.com/T/#t > .