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 3B18DC43387 for ; Fri, 21 Dec 2018 07:27:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 16E9321903 for ; Fri, 21 Dec 2018 07:27:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732889AbeLUH1p (ORCPT ); Fri, 21 Dec 2018 02:27:45 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55780 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732589AbeLUH1n (ORCPT ); Fri, 21 Dec 2018 02:27:43 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DA4EAC049587; Fri, 21 Dec 2018 07:27:42 +0000 (UTC) Received: from localhost (ovpn-8-19.pek2.redhat.com [10.72.8.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 58BA51001914; Fri, 21 Dec 2018 07:27:38 +0000 (UTC) Date: Fri, 21 Dec 2018 15:27:36 +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: <20181221072736.GB2526@MiWiFi-R3L-srv> References: <1544760446-506-1-git-send-email-kernelfans@gmail.com> <20181221071823.GA2526@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181221071823.GA2526@MiWiFi-R3L-srv> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 21 Dec 2018 07:27:42 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/21/18 at 03:18pm, Baoquan He wrote: > 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 ~~ s/@/M > 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 > >