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=-8.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 CEF7BC636C9 for ; Wed, 21 Jul 2021 12:04:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF6D961261 for ; Wed, 21 Jul 2021 12:04:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238473AbhGULYO (ORCPT ); Wed, 21 Jul 2021 07:24:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:41552 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238672AbhGULWx (ORCPT ); Wed, 21 Jul 2021 07:22:53 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626869010; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lIoWBvZyQ1nQ5eQbYUUlt0BMPpJi6szuMaY9eqlGLvI=; b=KPAd5gKUOSj5/qqCLVI8byUYEbsrI50VKu9QRHtZmxHdCv/2BevVYD2hxNZ3OLQn0lRFjo mKfVW7BeaNCSMCPNDWeCuNyRQDpl0YAJKE7V5wiok6lOQjaf5jDxY3QQgUlsYx+Wbx2XRu pGaFHVfrQrQGTEIDRB+2HF2u9qpp9Ms= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-590-vSzVV2NFMBureCNAwWT2rg-1; Wed, 21 Jul 2021 08:03:27 -0400 X-MC-Unique: vSzVV2NFMBureCNAwWT2rg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B465E1084F55; Wed, 21 Jul 2021 12:03:25 +0000 (UTC) Received: from [10.64.54.195] (vpn2-54-195.bne.redhat.com [10.64.54.195]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 33E235C1BB; Wed, 21 Jul 2021 12:03:21 +0000 (UTC) Reply-To: Gavin Shan Subject: Re: [PATCH v3 12/12] mm/debug_vm_pgtable: Fix corrupted page flag To: Anshuman Khandual , 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> From: Gavin Shan Message-ID: <8157142c-58e0-44c4-5cdb-76fff4a07210@redhat.com> Date: Wed, 21 Jul 2021 22:03:39 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <57cb2f04-b3f2-2df4-3d9b-0b430b9c9f3e@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Anshuman, 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 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. > Good point. I will improve chage log to include the commit ID in v4 where 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. Thanks, Gavin