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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41F00C0015E for ; Fri, 28 Jul 2023 01:06:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231174AbjG1BGX (ORCPT ); Thu, 27 Jul 2023 21:06:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38876 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229817AbjG1BGU (ORCPT ); Thu, 27 Jul 2023 21:06:20 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2B397113 for ; Thu, 27 Jul 2023 18:06:19 -0700 (PDT) Received: from dggpemm500014.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4RBqC01h5nzLnvh; Fri, 28 Jul 2023 09:03:40 +0800 (CST) Received: from [10.174.178.120] (10.174.178.120) by dggpemm500014.china.huawei.com (7.185.36.153) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Fri, 28 Jul 2023 09:06:16 +0800 Message-ID: Date: Fri, 28 Jul 2023 09:06:16 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird CC: , , , , , , , , Subject: Re: [RFC PATCH] arm64: mm: Fix kernel page tables incorrectly deleted during memory removal To: , , References: <20230717115150.1806954-1-mawupeng1@huawei.com> <20230721103628.GA12601@willie-the-truck> <35a0dad6-4f3b-f2c3-f835-b13c1e899f8d@huawei.com> <732e0db0-eb41-6c58-85b7-46257b4ba0b7@redhat.com> <3149f5f8-7878-dfe1-5745-870fddcc1108@huawei.com> Content-Language: en-US From: mawupeng In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.120] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500014.china.huawei.com (7.185.36.153) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/7/26 15:50, David Hildenbrand wrote: > On 26.07.23 08:20, mawupeng wrote: >> >> >> On 2023/7/24 14:11, David Hildenbrand wrote: >>> On 24.07.23 07:54, Anshuman Khandual wrote: >>>> >>>> >>>> On 7/24/23 06:55, mawupeng wrote: >>>>> >>>>> On 2023/7/21 18:36, Will Deacon wrote: >>>>>> On Mon, Jul 17, 2023 at 07:51:50PM +0800, Wupeng Ma wrote: >>>>>>> From: Ma Wupeng >>>>>>> >>>>>>> During our test, we found that kernel page table may be unexpectedly >>>>>>> cleared with rodata off. The root cause is that the kernel page is >>>>>>> initialized with pud size(1G block mapping) while offline is memory >>>>>>> block size(MIN_MEMORY_BLOCK_SIZE 128M), eg, if 2G memory is hot-added, >>>>>>> when offline a memory block, the call trace is shown below, >>> >>> Is someone adding memory in 2 GiB granularity and then removing parts of it in 128 MiB granularity? That would be against what we support using the add_memory() / offline_and_remove_memory() API and that driver should be fixed instead. >> >> Yes, this kind of situation. >> >> The problem occurs in the following scenarios: >> 1. use mem=xxG to reserve memory. >> 2. add_momory to online memory. >> 3. offline part of the memroy via offline_and_remove_memory. >> >> During my research, ACPI memory removal use memory_subsys_offline to offline memory section and >> this will not delete page table entry which do not trigger this kind of problem. >> >> So I understand what you are talking about. >> 1. 3rd-party driver shouldn't use add_memory/offline_and_remove_memory to online/offline memory. >>     If it have to use, this can be achieved by driver. >> 2. memory_subsys_offline is perfered to do such thing. > > No, my point is that > > 1) If you use add_memory() and offline_and_remove_memory() in the *same >    granularity* it has to be working, otherwise it has to be fixed. > > 2) If you use add_memory() and offline_and_remove_memory() in different >    granularity (especially, add_memory() in bigger granularity) , then >    change your code to do add_memory() in the same granularity. > > > If you run into 1), then we populated a PUD for boot memory that also covers yet unpopulated physical memory ranges that are later populated by add_memory(). If that's the case, then we can either fix it by > > a) Not doing that. Use PMD tables instead for that piece of memory. > > b) Detecting that that PUD still covers memory and refusing to remove >    that PUD. > > c) Rejecting to hotadd memory in this situation at that location. We >    have mhp_get_pluggable_range() -> arch_get_mappable_range() to kind- >    of handle something like that. Thank you for your patient answer. This I do understand and answer my question. >