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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 57CE7C169C4 for ; Tue, 29 Jan 2019 05:26:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 245E72175B for ; Tue, 29 Jan 2019 05:26:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="sdT4NTn3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725927AbfA2FZ6 (ORCPT ); Tue, 29 Jan 2019 00:25:58 -0500 Received: from mail-it1-f194.google.com ([209.85.166.194]:39261 "EHLO mail-it1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725536AbfA2FZ6 (ORCPT ); Tue, 29 Jan 2019 00:25:58 -0500 Received: by mail-it1-f194.google.com with SMTP id a6so2222283itl.4 for ; Mon, 28 Jan 2019 21:25:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=EoG5zwFwz/zugmlvlLSPlZlHaXhenbG7kxD8d9Gdc6I=; b=sdT4NTn3UEoDcjYdl88c/v54HrLEA/aFP28q2P7yNEKSpqwThNGVk7TB0Uxrr+4y2/ A3Ub4yetGLKWHyBtjYPI7xVl/Lkp+O7lHsnjHqKQ+YIZPUqpfL6Z1hQsQzuE0sJnlIGC KCmHsCSOQV4VfOabrFeq2rQHMkZQGExU1ZnqwjimLT+yKF3EiGHm7TlMl8FzidsdIXiy XTl7Z1f03clEVei+6oUGnIpDCJj7HOeT9PJvgY0zhIBhDNR0sFNhCqW0xmG6rVCS6M4B tRmCvrGmISKHHkMK31LlEyQicEuYRuVjDOP54v79cr54DRCdOG3k14KcWCikPkoFy07b UsOw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=EoG5zwFwz/zugmlvlLSPlZlHaXhenbG7kxD8d9Gdc6I=; b=Kn3Xpb9TCSvTs+jYB2JPGZkwZEme/pj/ycjIOWAG1Q0+qgb8hDZ/NdqMM1MM0I5iEi 7vGT95nCL0WKnkIUcCvtgVHlY5+FibHCIX2g9qJehZr8TIG560uwEPB9L8r7Z5h3lKcB BbDURvHV46JHcDA6mtA49ukEISCP6iKDXCjJpBYOokWjF11FG6rXxsVj2sEi29eSAYlw wCjkKKaAmk7uruaMZkegXr7a0+EERRMUdzorNHyr6ns+mZ4MKuF6b22GDM2pffETwlon cisPPDrO+H/R6t8qtC0kz6ymC0N7jyfQ/HtXqollz5f5fwIlPl6MJ8PHMmTVj3wH+sBc 83ug== X-Gm-Message-State: AJcUukfSasNlW9KxvbRmrOfMwejnUZZLSxtxtu2jI+Sd5vidn4GqLKTH RB8FpTkf2GZsgBEyCgF15+GFx0qcTzeViWaBqw== X-Google-Smtp-Source: ALg8bN6uTIzeMHCllwA/WgMqJO9wmgVvumRuxHlvOCZbLPvD0wfLXx1+kTh6xK0NmGHayz96N5OA2Iqx+f2N3m9mX88= X-Received: by 2002:a24:5608:: with SMTP id o8mr11575917itb.35.1548739556984; Mon, 28 Jan 2019 21:25:56 -0800 (PST) MIME-Version: 1.0 References: <1548047768-7656-1-git-send-email-kernelfans@gmail.com> <20190125103924.GB27998@zn.tnic> <20190125134518.GA23595@dhcp-128-65.nay.redhat.com> <20190125140823.GC27998@zn.tnic> In-Reply-To: <20190125140823.GC27998@zn.tnic> From: Pingfan Liu Date: Tue, 29 Jan 2019 13:25:45 +0800 Message-ID: Subject: Re: [PATCHv7] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr To: Borislav Petkov Cc: Dave Young , kexec@lists.infradead.org, Baoquan He , Andrew Morton , Mike Rapoport , Yinghai Lu , vgoyal@redhat.com, Randy Dunlap , x86@kernel.org, LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 25, 2019 at 10:08 PM Borislav Petkov wrote: > > On Fri, Jan 25, 2019 at 09:45:18PM +0800, Dave Young wrote: > > AFAIK, some people prefer to explictly reserve crash memory at high > > region even if it is possible to reserve at low area. May because > > <4G memory is limited on large server, they want to leave this for other > > use. > > > > Yinghai or Vivek should know more about the history, probably they can > > recall some initial reason. > Go through the git log, and I found the initial introduction of crashkernel_high option. Refer to commit 55a20ee7804ab64ac90bcdd4e2868a42829e2784 Author: Yinghai Lu Date: Mon Apr 15 22:23:47 2013 -0700 x86, kdump: Retore crashkernel= to allocate under 896M Vivek found old kexec-tools does not work new kernel anymore. So change back crashkernel= back to old behavoir, and add crashkernel_high= to let user decide if buffer could be above 4G, and also new kexec-tools will be needed. But kexec-tools-2.0.3, released at 2012, can run 4.20 kernel with crashkernel=256M@5G, so I think only very old kexec-tools requires memory under 896M. Due to -1.few people running latest kernel with very old kexec-tools to date, -2. crashkernel=X is more popular than crashkernel=X.high, it should be time to eliminate this limit of crashkernel=X parameter, otherwise we will run into this bug. As for crashkernel=,high, I think it is a more professional option for who cares about the DMA32. On high-end machine, big reserved region is used for crashkernel(e.g. in this case 384M), which make the crowed situation under under 4GB memory worse. > Yes, just "prefer" is not good enough. There should be a technical > reason why that's there. > > Also, if the user doesn't care, then the code should be free to force > "high" and thus probe a different range for allocation. > Do you suggest to remove crashkernel=X,high parameter? Thanks, Pingfan > > Good question, still it may be some historical reason, but it is good to > > make them clear and rethink about it after long time. > > > > I also want to understand, need dig the log more. > > Good idea. That would be a very nice cleanup. :-) > > Thx. > > -- > Regards/Gruss, > Boris. > > Good mailing practices for 400: avoid top-posting and trim the reply.