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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, 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 CD4C8C43387 for ; Mon, 31 Dec 2018 08:46:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9ED7021019 for ; Mon, 31 Dec 2018 08:46:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727175AbeLaIqY (ORCPT ); Mon, 31 Dec 2018 03:46:24 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:39292 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727132AbeLaIqY (ORCPT ); Mon, 31 Dec 2018 03:46:24 -0500 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wBV8iF50068679 for ; Mon, 31 Dec 2018 03:46:23 -0500 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0a-001b2d01.pphosted.com with ESMTP id 2pqdjxmj2h-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 31 Dec 2018 03:46:22 -0500 Received: from localhost by e06smtp07.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) Mon, 31 Dec 2018 08:46:14 -0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id wBV8kDLi8258044 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 31 Dec 2018 08:46:13 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2857F4C040; Mon, 31 Dec 2018 08:46:13 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2A5D54C044; Mon, 31 Dec 2018 08:46:11 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.205.47]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 31 Dec 2018 08:46:11 +0000 (GMT) Date: Mon, 31 Dec 2018 10:46:09 +0200 From: Mike Rapoport To: Pingfan Liu Cc: 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 , Baoquan He , yinghai@kernel.org, vgoyal@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCHv3 2/2] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr References: <1545966002-3075-1-git-send-email-kernelfans@gmail.com> <1545966002-3075-3-git-send-email-kernelfans@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1545966002-3075-3-git-send-email-kernelfans@gmail.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 18123108-0028-0000-0000-000003312268 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18123108-0029-0000-0000-000023EE668D Message-Id: <20181231084608.GB28478@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-12-31_06:,, 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-1812310082 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 28, 2018 at 11:00:02AM +0800, Pingfan Liu wrote: > Customer reported a bug on a high end server with many pcie devices, where > kernel bootup with crashkernel=384M, and kaslr is enabled. Even > though we still see much memory under 896 MB, the finding still failed > intermittently. Because currently we can only find region under 896 MB, > if w/0 ',high' specified. Then KASLR breaks 896 MB into several parts > randomly, and crashkernel reservation need be aligned to 128 MB, that's > why failure is found. It raises confusion to the end user that sometimes > crashkernel=X works while sometimes fails. > If want to make it succeed, customer can change kernel option to > "crashkernel=384M, high". Just this give "crashkernel=xx@yy" a very > limited space to behave even though its grammer looks more generic. > And we can't answer questions raised from customer that confidently: > 1) why it doesn't succeed to reserve 896 MB; > 2) what's wrong with memory region under 4G; > 3) why I have to add ',high', I only require 384 MB, not 3840 MB. > > This patch simplifies the method suggested in the mail [1]. It just goes > bottom-up to find a candidate region for crashkernel. The bottom-up may be > better compatible with the old reservation style, i.e. still want to get > memory region from 896 MB firstly, then [896 MB, 4G], finally above 4G. > > There is one trivial thing about the compatibility with old kexec-tools: > if the reserved region is above 896M, then old tool will fail to load > bzImage. But without this patch, the old tool also fail since there is no > memory below 896M can be reserved for crashkernel. > > [1]: http://lists.infradead.org/pipermail/kexec/2017-October/019571.html > Signed-off-by: Pingfan Liu > Cc: Tang Chen > Cc: "Rafael J. Wysocki" > Cc: Len Brown > Cc: Andrew Morton > Cc: Mike Rapoport > Cc: Michal Hocko > Cc: Jonathan Corbet > Cc: Yaowei Bai > Cc: Pavel Tatashin > Cc: Nicholas Piggin > Cc: Naoya Horiguchi > Cc: Daniel Vacek > Cc: Mathieu Malaterre > Cc: Stefan Agner > Cc: Dave Young > Cc: Baoquan He > Cc: yinghai@kernel.org, > Cc: vgoyal@redhat.com > Cc: linux-kernel@vger.kernel.org > --- > arch/x86/kernel/setup.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index d494b9b..165f9c3 100644 > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -541,15 +541,18 @@ static void __init reserve_crashkernel(void) > > /* 0 means: find the address automatically */ > if (crash_base <= 0) { > + bool bottom_up = memblock_bottom_up(); > + > + memblock_set_bottom_up(true); > > /* > * Set CRASH_ADDR_LOW_MAX upper bound for crash memory, > * as old kexec-tools loads bzImage below that, unless > * "crashkernel=size[KMG],high" is specified. > */ > crash_base = memblock_find_in_range(CRASH_ALIGN, > - high ? CRASH_ADDR_HIGH_MAX > - : CRASH_ADDR_LOW_MAX, > - crash_size, CRASH_ALIGN); > + (max_pfn * PAGE_SIZE), crash_size, CRASH_ALIGN); > + memblock_set_bottom_up(bottom_up); Using bottom-up does not guarantee that the allocation won't fall into a removable memory, it only makes it highly probable. I think that the 'max_pfn * PAGE_SIZE' limit should be replaced with the end of the non-removable memory node. > + > if (!crash_base) { > pr_info("crashkernel reservation failed - No suitable area found.\n"); > return; > -- > 2.7.4 > -- Sincerely yours, Mike.