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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 58E74C433B4 for ; Fri, 16 Apr 2021 15:05:30 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A2178611BF for ; Fri, 16 Apr 2021 15:05:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A2178611BF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4FMKJm0TTFz3c7D for ; Sat, 17 Apr 2021 01:05:28 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=csgroup.eu (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@csgroup.eu; receiver=) Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4FMKJL4H8Dz2yxT for ; Sat, 17 Apr 2021 01:05:03 +1000 (AEST) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4FMKJB6MPwz9v3LN; Fri, 16 Apr 2021 17:04:58 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id nfnIuGVT2LDV; Fri, 16 Apr 2021 17:04:58 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4FMKJB4wVtz9v3LK; Fri, 16 Apr 2021 17:04:58 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 0F4968B851; Fri, 16 Apr 2021 17:05:00 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id gM_a9XKodz3W; Fri, 16 Apr 2021 17:04:59 +0200 (CEST) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 7EF558B84C; Fri, 16 Apr 2021 17:04:58 +0200 (CEST) Subject: Re: [PATCH v1 3/5] mm: ptdump: Provide page size to notepage() From: Christophe Leroy To: Steven Price , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , akpm@linux-foundation.org References: <1ef6b954fb7b0f4dfc78820f1e612d2166c13227.1618506910.git.christophe.leroy@csgroup.eu> <41819925-3ee5-4771-e98b-0073e8f095cf@arm.com> <1102cda1-b00f-b6ef-6bf3-22068cc11510@arm.com> <6ff4816b-8ff6-19de-73a2-3fcadc003ccd@csgroup.eu>

Message-ID: Date: Fri, 16 Apr 2021 17:04:56 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 16/04/2021 à 16:40, Christophe Leroy a écrit : > > > Le 16/04/2021 à 15:00, Steven Price a écrit : >> On 16/04/2021 12:08, Christophe Leroy wrote: >>> >>> >>> Le 16/04/2021 à 12:51, Steven Price a écrit : >>>> On 16/04/2021 11:38, Christophe Leroy wrote: >>>>> >>>>> >>>>> Le 16/04/2021 à 11:28, Steven Price a écrit : >>>>>> To be honest I don't fully understand why powerpc requires the page_size - it appears to be >>>>>> using it purely to find "holes" in the calls to note_page(), but I haven't worked out why such >>>>>> holes would occur. >>>>> >>>>> I was indeed introduced for KASAN. We have a first commit >>>>> https://github.com/torvalds/linux/commit/cabe8138 which uses page size to detect whether it is >>>>> a KASAN like stuff. >>>>> >>>>> Then came https://github.com/torvalds/linux/commit/b00ff6d8c as a fix. I can't remember what >>>>> the problem was exactly, something around the use of hugepages for kernel memory, came as part >>>>> of the series >>>>> https://patchwork.ozlabs.org/project/linuxppc-dev/cover/cover.1589866984.git.christophe.leroy@csgroup.eu/ >>>> >>>> >>>> >>>> >>>> >>>> Ah, that's useful context. So it looks like powerpc took a different route to reducing the KASAN >>>> output to x86. >>>> >>>> Given the generic ptdump code has handling for KASAN already it should be possible to drop that >>>> from the powerpc arch code, which I think means we don't actually need to provide page size to >>>> notepage(). Hopefully that means more code to delete ;) >>>> >>> >>> Yes ... and no. >>> >>> It looks like the generic ptdump handles the case when several pgdir entries points to the same >>> kasan_early_shadow_pte. But it doesn't take into account the powerpc case where we have regular >>> page tables where several (if not all) PTEs are pointing to the kasan_early_shadow_page . >> >> I'm not sure I follow quite how powerpc is different here. But could you have a similar check for >> PTEs against kasan_early_shadow_pte as the other levels already have? >> >> I'm just worried that page_size isn't well defined in this interface and it's going to cause >> problems in the future. >> > > I'm trying. I reverted the two commits b00ff6d8c and cabe8138. > > At the moment, I don't get exactly what I expect: For linear memory I get one line for each 8M page > whereas before reverting the patches I got one 16M line and one 112M line. > > And for KASAN shadow area I get two lines for the 2x 8M pages shadowing linear mem then I get one 4M > line for each PGDIR entry pointing to kasan_early_shadow_pte. > > 0xf8000000-0xf87fffff 0x07000000 8M huge rw present > 0xf8800000-0xf8ffffff 0x07800000 8M huge rw present > 0xf9000000-0xf93fffff 0x01430000 4M r present ... > 0xfec00000-0xfeffffff 0x01430000 4M r present > > Any idea ? > I think the different with other architectures is here: } else if (flag != st->current_flags || level != st->level || addr >= st->marker[1].start_address || pa != st->last_pa + PAGE_SIZE) { In addition to the checks everyone do, powerpc also checks "pa != st->last_pa + PAGE_SIZE". And it is definitely for that test that page_size argument add been added. I see that other architectures except RISCV don't dump the physical address. But even RISCV doesn't include that check. That physical address dump was added by commit aaa229529244 ("powerpc/mm: Add physical address to Linux page table dump") [https://github.com/torvalds/linux/commit/aaa2295] How do other architectures deal with the problem described by the commit log of that patch ? Christophe