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=-5.4 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 96F06C12002 for ; Wed, 21 Jul 2021 13:55:31 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 344916121E for ; Wed, 21 Jul 2021 13:55:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 344916121E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BDDBF6B0070; Wed, 21 Jul 2021 09:55:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B99436B0078; Wed, 21 Jul 2021 09:55:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A7CB26B0072; Wed, 21 Jul 2021 09:55:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 8C03C6B0033 for ; Wed, 21 Jul 2021 09:55:30 -0400 (EDT) Received: from forelay.prod.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by fograve02.hostedemail.com (Postfix) with ESMTP id 4835A231B7 for ; Wed, 21 Jul 2021 10:17:49 +0000 (UTC) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id E26CB8248047 for ; Wed, 21 Jul 2021 10:17:48 +0000 (UTC) X-FDA: 78386193816.22.0F77149 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf27.hostedemail.com (Postfix) with ESMTP id 3EDE770000AE for ; Wed, 21 Jul 2021 10:17:48 +0000 (UTC) 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 2444731B; Wed, 21 Jul 2021 03:17:47 -0700 (PDT) Received: from [10.163.64.235] (unknown [10.163.64.235]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BB6EA3F694; Wed, 21 Jul 2021 03:17:44 -0700 (PDT) Subject: Re: [PATCH v3 12/12] mm/debug_vm_pgtable: Fix corrupted page flag To: Gavin Shan , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, chuhu@redhat.com, shan.gavin@gmail.com References: <20210719130613.334901-1-gshan@redhat.com> <20210719130613.334901-13-gshan@redhat.com> From: Anshuman Khandual Message-ID: <57cb2f04-b3f2-2df4-3d9b-0b430b9c9f3e@arm.com> Date: Wed, 21 Jul 2021 15:48:34 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210719130613.334901-13-gshan@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Authentication-Results: imf27.hostedemail.com; dkim=none; spf=pass (imf27.hostedemail.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com; dmarc=pass (policy=none) header.from=arm.com X-Rspamd-Server: rspam05 X-Stat-Signature: mi61hr5kyjtngwgwtpcwrd81i9zhab17 X-Rspamd-Queue-Id: 3EDE770000AE X-HE-Tag: 1626862668-636603 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 7/19/21 6:36 PM, Gavin Shan wrote: > In page table entry modifying tests, set_xxx_at() are used to populate > the page table entries. On ARM64, PG_arch_1 is set to the target page > flag if execution permission is given. The page flag is kept when the > page is free'd to buddy's free area list. However, it will trigger page > checking failure when it's pulled from the buddy's free area list, as > the following warning messages indicate. > > BUG: Bad page state in process memhog pfn:08000 > page:0000000015c0a628 refcount:0 mapcount:0 \ > mapping:0000000000000000 index:0x1 pfn:0x8000 > flags: 0x7ffff8000000800(arch_1|node=0|zone=0|lastcpupid=0xfffff) > raw: 07ffff8000000800 dead000000000100 dead000000000122 0000000000000000 > raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000 > page dumped because: PAGE_FLAGS_CHECK_AT_PREP flag(s) set > > This fixes the issue by clearing PG_arch_1 through flush_dcache_page() > after set_xxx_at() is called. Could you please add comments before each flush_dcache_page() instance explaining why this is needed for arm64 platforms with relevant PG_arch_1 context and how this does not have any adverse effect on other platforms ? It should be easy for some one looking at this code after a while to figure out from where flush_dcache_page() came from.