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 CCCB7C636C8 for ; Thu, 22 Jul 2021 03:50:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5FE5D61241 for ; Thu, 22 Jul 2021 03:50:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5FE5D61241 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 D8C936B0036; Wed, 21 Jul 2021 23:50:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D3C9C6B005D; Wed, 21 Jul 2021 23:50:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C2B426B006C; Wed, 21 Jul 2021 23:50:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0226.hostedemail.com [216.40.44.226]) by kanga.kvack.org (Postfix) with ESMTP id A5AC26B0036 for ; Wed, 21 Jul 2021 23:50:27 -0400 (EDT) Received: from smtpin35.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 57B8B824805A for ; Thu, 22 Jul 2021 03:50:27 +0000 (UTC) X-FDA: 78388846494.35.AF69D9F Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf05.hostedemail.com (Postfix) with ESMTP id D060B5004713 for ; Thu, 22 Jul 2021 03:50:26 +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 D5339D6E; Wed, 21 Jul 2021 20:50:25 -0700 (PDT) Received: from [10.163.65.134] (unknown [10.163.65.134]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1C63A3F66F; Wed, 21 Jul 2021 20:50:22 -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> <57cb2f04-b3f2-2df4-3d9b-0b430b9c9f3e@arm.com> <8157142c-58e0-44c4-5cdb-76fff4a07210@redhat.com> From: Anshuman Khandual Message-ID: <5db75fd6-aeb9-c06f-30ab-839c09a0bc68@arm.com> Date: Thu, 22 Jul 2021 09:21:11 +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: <8157142c-58e0-44c4-5cdb-76fff4a07210@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: D060B5004713 X-Stat-Signature: m5of4bur7moowec83oh8sqnuuwbmajuc Authentication-Results: imf05.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf05.hostedemail.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com X-HE-Tag: 1626925826-520791 Content-Transfer-Encoding: quoted-printable 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: Small nit: s/Fix corrupted page flag/Fix page flag corruption on arm64/ On 7/21/21 5:33 PM, Gavin Shan wrote: > Hi Anshuman, >=20 > On 7/21/21 8:18 PM, Anshuman Khandual wrote: >> On 7/19/21 6:36 PM, Gavin Shan wrote: >>> In page table entry modifying tests, set_xxx_at() are used to populat= e >>> 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 pa= ge >>> checking failure when it's pulled from the buddy's free area list, as >>> the following warning messages indicate. >>> >>> =C2=A0=C2=A0=C2=A0 BUG: Bad page state in process memhog=C2=A0 pfn:08= 000 >>> =C2=A0=C2=A0=C2=A0 page:0000000015c0a628 refcount:0 mapcount:0 \ >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 mapping:000000000000= 0000 index:0x1 pfn:0x8000 >>> =C2=A0=C2=A0=C2=A0 flags: 0x7ffff8000000800(arch_1|node=3D0|zone=3D0|= lastcpupid=3D0xfffff) >>> =C2=A0=C2=A0=C2=A0 raw: 07ffff8000000800 dead000000000100 dead0000000= 00122 0000000000000000 >>> =C2=A0=C2=A0=C2=A0 raw: 0000000000000001 0000000000000000 00000000fff= fffff 0000000000000000 >>> =C2=A0=C2=A0=C2=A0 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_arc= h_1 >> context and how this does not have any adverse effect on other platfor= ms ? >> It should be easy for some one looking at this code after a while to f= igure >> out from where flush_dcache_page() came from. >> >=20 > Good point. I will improve chage log to include the commit ID in v4 whe= re the > page flag (PG_arch_1) is used and explain how. In that case, it's much = clearer > to understand the reason why we need flush_dcache_page() after set_xxx_= at() on > ARM64. But also some in code comments where flush_dcache_page() is being called.