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=-10.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 13C50C4320A for ; Wed, 28 Jul 2021 10:04:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB76860F23 for ; Wed, 28 Jul 2021 10:04:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235788AbhG1KEz (ORCPT ); Wed, 28 Jul 2021 06:04:55 -0400 Received: from foss.arm.com ([217.140.110.172]:54448 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231635AbhG1KEy (ORCPT ); Wed, 28 Jul 2021 06:04:54 -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 AB5FC31B; Wed, 28 Jul 2021 03:04:52 -0700 (PDT) Received: from [10.163.65.183] (unknown [10.163.65.183]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 473503F73D; Wed, 28 Jul 2021 03:04:49 -0700 (PDT) Subject: Re: [PATCH v4 12/12] mm/debug_vm_pgtable: Fix corrupted page flag To: Christophe Leroy , Gavin Shan Cc: shan.gavin@gmail.com, chuhu@redhat.com, akpm@linux-foundation.org, will@kernel.org, catalin.marinas@arm.com, cai@lca.pw, aneesh.kumar@linux.ibm.com, gerald.schaefer@linux.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20210727061401.592616-1-gshan@redhat.com> <20210727061401.592616-13-gshan@redhat.com> <20210728095326.Horde.k1npSPaQKh2i7W3XoBsdiQ3@messagerie.c-s.fr> From: Anshuman Khandual Message-ID: <58a1eaa9-ba63-403b-1f4b-c22f23a3a0d3@arm.com> Date: Wed, 28 Jul 2021 15:35:37 +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: <20210728095326.Horde.k1npSPaQKh2i7W3XoBsdiQ3@messagerie.c-s.fr> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/28/21 1:23 PM, Christophe Leroy wrote: > Gavin Shan a écrit : > >> In page table entry modifying tests, set_xxx_at() are used to populate >> the page table entries. On ARM64, PG_arch_1 (PG_dcache_clean) flag is >> set to the target page flag if execution permission is given. The logic >> exits since commit 4f04d8f00545 ("arm64: MMU definitions"). 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. For architectures other than ARM64, the >> unexpected overhead of cache flushing is acceptable. >> >> Signed-off-by: Gavin Shan > > Maybe a Fixes: tag would be good to have Agreed. Fixes: a5c3b9ffb0f4 ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers") > > And would it be possible to have this fix as first patch of the series so that it can be applied to stable without applying the whole series ? Changing the allocation scheme does solve another problem (using non-owned pages) but is achieved via the entire series applied. But this particular patch could be moved to the beginning without much problem.