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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 6E9CEC43387 for ; Sun, 6 Jan 2019 06:28:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3B8682184C for ; Sun, 6 Jan 2019 06:28:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726425AbfAFG1u (ORCPT ); Sun, 6 Jan 2019 01:27:50 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:49534 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726258AbfAFG1t (ORCPT ); Sun, 6 Jan 2019 01:27:49 -0500 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id x066ODkw068426 for ; Sun, 6 Jan 2019 01:27:48 -0500 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0b-001b2d01.pphosted.com with ESMTP id 2pub4htc05-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Sun, 06 Jan 2019 01:27:47 -0500 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Sun, 6 Jan 2019 06:27:38 -0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x066Rber5505528 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Sun, 6 Jan 2019 06:27:37 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B15CB42045; Sun, 6 Jan 2019 06:27:37 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0EB344203F; Sun, 6 Jan 2019 06:27:36 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.8.246]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Sun, 6 Jan 2019 06:27:35 +0000 (GMT) Date: Sun, 6 Jan 2019 08:27:34 +0200 From: Mike Rapoport To: Baoquan He Cc: Tejun Heo , Pingfan Liu , linux-acpi@vger.kernel.org, linux-mm@kvack.org, kexec@lists.infradead.org, Tang Chen , "Rafael J. Wysocki" , Len Brown , Andrew Morton , Mike Rapoport , Michal Hocko , Jonathan Corbet , Yaowei Bai , Pavel Tatashin , Nicholas Piggin , Naoya Horiguchi , Daniel Vacek , Mathieu Malaterre , Stefan Agner , Dave Young , yinghai@kernel.org, vgoyal@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCHv3 1/2] mm/memblock: extend the limit inferior of bottom-up after parsing hotplug attr References: <1545966002-3075-1-git-send-email-kernelfans@gmail.com> <1545966002-3075-2-git-send-email-kernelfans@gmail.com> <20181231084018.GA28478@rapoport-lnx> <20190102092749.GA22664@rapoport-lnx> <20190102101804.GD1990@MiWiFi-R3L-srv> <20190102170537.GA3591@rapoport-lnx> <20190103184706.GU2509588@devbig004.ftw2.facebook.com> <20190104150929.GA32252@rapoport-lnx> <20190105034450.GE30750@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190105034450.GE30750@MiWiFi-R3L-srv> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19010606-0020-0000-0000-00000301DBCE X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19010606-0021-0000-0000-00002152E46D Message-Id: <20190106062733.GA3728@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-01-06_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901060056 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 05, 2019 at 11:44:50AM +0800, Baoquan He wrote: > On 01/04/19 at 05:09pm, Mike Rapoport wrote: > > On Thu, Jan 03, 2019 at 10:47:06AM -0800, Tejun Heo wrote: > > > Hello, > > > > > > On Wed, Jan 02, 2019 at 07:05:38PM +0200, Mike Rapoport wrote: > > > > I agree that currently the bottom-up allocation after the kernel text has > > > > issues with KASLR. But this issues are not necessarily related to the > > > > memory hotplug. Even with a single memory node, a bottom-up allocation will > > > > fail if KASLR would put the kernel near the end of node0. > > > > > > > > What I am trying to understand is whether there is a fundamental reason to > > > > prevent allocations from [0, kernel_start)? > > > > > > > > Maybe Tejun can recall why he suggested to start bottom-up allocations from > > > > kernel_end. > > > > > > That's from 79442ed189ac ("mm/memblock.c: introduce bottom-up > > > allocation mode"). I wasn't involved in that patch, so no idea why > > > the restrictions were added, but FWIW it doesn't seem necessary to me. > > > > I should have added the reference [1] at the first place :) > > Thanks! > > > > [1] https://lore.kernel.org/lkml/20130904192215.GG26609@mtj.dyndns.org/ > > With my understanding, we may not be able to discard the bottom-up > method for the current kernel. It's related to hotplug feature when > 'movable_node' kernel parameter is specified. With 'movable_node', > system relies on reading hotplug information from firmware, on x86 it's > acpi SRAT table. In the current system, we allocate memblock region > top-down by default. However, before that hotplug information retrieving, > there are several places of memblock allocating, top-down memblock > allocation must break hotplug feature since it will allocate kernel data > in movable zone which is usually at the end node on bare metal system. I do not suggest to discard the bottom-up method, I merely suggest to allow it to use [0, kernel_start). > This bottom-up way is taken on many ARCHes, it works well on system if > KASLR is not enabled. Below is the searching result in the current linux > kernel, we can see that all ARCHes have this mechanism, except of > arm/arm64. But now only arm64/mips/x86 have KASLR. > > W/o KASLR, allocating memblock region above kernle end when hotplug info > is not parsed, looks very reasonable. Since kernel is usually put at > lower address, e.g on x86, it's 16M. My thought is that we need do > memblock allocation around kernel before hotplug info parsed. That is > for system w/o KASLR, we will keep the current bottom-up way; for system > with KASLR, we should allocate memblock region top-down just below > kernel start. I completely agree. I was thinking about making memblock_find_in_range_node() to do something like if (memblock_bottom_up()) { bottom_up_start = max(start, kernel_end); ret = __memblock_find_range_bottom_up(bottom_up_start, end, size, align, nid, flags); if (ret) return ret; bottom_up_start = max(start, 0); end = kernel_start; ret = __memblock_find_range_top_down(bottom_up_start, end, size, align, nid, flags); if (ret) return ret; } > This issue must break hotplug, just because currently bare metal system > need add 'nokaslr' to disable KASLR since another bug fix is under > discussion as below, so this issue is covered up. > > [PATCH v14 0/5] x86/boot/KASLR: Parse ACPI table and limit KASLR to choosing immovable memory > lkml.kernel.org/r/20181214093013.13370-1-fanc.fnst@cn.fujitsu.com > > [~ ]$ git grep memblock_set_bottom_up > arch/alpha/kernel/setup.c: memblock_set_bottom_up(true); > arch/m68k/mm/motorola.c: memblock_set_bottom_up(true); > arch/mips/kernel/setup.c: memblock_set_bottom_up(true); > arch/mips/kernel/traps.c: memblock_set_bottom_up(false); > arch/nds32/kernel/setup.c: memblock_set_bottom_up(true); > arch/powerpc/kernel/paca.c: memblock_set_bottom_up(true); > arch/powerpc/kernel/paca.c: memblock_set_bottom_up(false); > arch/s390/kernel/setup.c: memblock_set_bottom_up(true); > arch/s390/kernel/setup.c: memblock_set_bottom_up(false); > arch/sparc/mm/init_32.c: memblock_set_bottom_up(true); > arch/x86/kernel/setup.c: memblock_set_bottom_up(true); > arch/x86/mm/numa.c: memblock_set_bottom_up(false); > include/linux/memblock.h:static inline void __init memblock_set_bottom_up(bool enable) > -- Sincerely yours, Mike.