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[23.128.96.18]) by mx.google.com with ESMTP id k17si18245474pgl.58.2021.04.19.07.36.21; Mon, 19 Apr 2021 07:36:34 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240679AbhDSNSV (ORCPT + 99 others); Mon, 19 Apr 2021 09:18:21 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:1813 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240144AbhDSNOy (ORCPT ); Mon, 19 Apr 2021 09:14:54 -0400 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4FP6j54THDz9txv8; Mon, 19 Apr 2021 15:14:17 +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 yKDNb47P5hGT; Mon, 19 Apr 2021 15:14:17 +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 4FP6j53cN4z9txv7; Mon, 19 Apr 2021 15:14:17 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 866238B7B4; Mon, 19 Apr 2021 15:14:22 +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 CgC9R0HVBL9q; Mon, 19 Apr 2021 15:14:22 +0200 (CEST) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id AB4DA8B7BD; Mon, 19 Apr 2021 15:14:21 +0200 (CEST) Subject: Re: [PATCH v1 3/5] mm: ptdump: Provide page size to notepage() To: Steven Price , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , akpm@linux-foundation.org Cc: linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, x86@kernel.org, linux-mm@kvack.org References: <1ef6b954fb7b0f4dfc78820f1e612d2166c13227.1618506910.git.christophe.leroy@csgroup.eu> <41819925-3ee5-4771-e98b-0073e8f095cf@arm.com> <1102cda1-b00f-b6ef-6bf3-22068cc11510@arm.com> From: Christophe Leroy Message-ID: <627ee414-2f78-94e3-b77b-1013f52e77e3@csgroup.eu> Date: Mon, 19 Apr 2021 15:14:21 +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: <1102cda1-b00f-b6ef-6bf3-22068cc11510@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 : >>> On 15/04/2021 18:18, Christophe Leroy wrote: >>> >>> 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 ;) > Looking at how the generic ptdump code handles KASAN, I'm a bit sceptic. IIUC, it is checking that kasan_early_shadow_pte is in the same page as the pgtable referred by the PMD entry. But what happens if that PMD entry is referring another pgtable which is inside the same page as kasan_early_shadow_pte ? Shouldn't the test be if (pmd_page_vaddr(val) == lm_alias(kasan_early_shadow_pte)) return note_kasan_page_table(walk, addr); Christophe