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=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 3D280C43387 for ; Fri, 21 Dec 2018 07:18:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 01E94218FD for ; Fri, 21 Dec 2018 07:18:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732122AbeLUHSb (ORCPT ); Fri, 21 Dec 2018 02:18:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:22614 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728835AbeLUHSb (ORCPT ); Fri, 21 Dec 2018 02:18:31 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C7A00A7E1; Fri, 21 Dec 2018 07:18:30 +0000 (UTC) Received: from localhost (ovpn-8-19.pek2.redhat.com [10.72.8.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id ADBD64AC; Fri, 21 Dec 2018 07:18:26 +0000 (UTC) Date: Fri, 21 Dec 2018 15:18:23 +0800 From: Baoquan He To: Pingfan Liu , Andrew Morton Cc: linux-kernel@vger.kernel.org, Dave Young , yinghai@kernel.org, vgoyal@redhat.com, kexec@lists.infradead.org Subject: Re: [PATCHv2] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr Message-ID: <20181221071823.GA2526@MiWiFi-R3L-srv> References: <1544760446-506-1-git-send-email-kernelfans@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1544760446-506-1-git-send-email-kernelfans@gmail.com> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Fri, 21 Dec 2018 07:18:30 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/14/18 at 12:07pm, 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: Dave Young > Cc: Andrew Morton > Cc: Baoquan He > Cc: yinghai@kernel.org, > Cc: vgoyal@redhat.com > Cc: kexec@lists.infradead.org > > --- > v1->v2: > improve commit log > arch/x86/kernel/setup.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) This is a bug fix and urged by our customer. I personally think crashkernel=xx@ is a generic synctax, the current code making it search only under 896 MB seems not so reasonable. Ack this patch. Acked-by: Baoquan He Thanks Baoquan > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index d494b9b..60f12c4 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) { > + if (!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); > + if (!memblock_bottom_up()) > + memblock_set_bottom_up(false); > + > if (!crash_base) { > pr_info("crashkernel reservation failed - No suitable area found.\n"); > return; > -- > 2.7.4 >