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 22E0CC282C8 for ; Mon, 28 Jan 2019 09:58:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E6FD62087F for ; Mon, 28 Jan 2019 09:58:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726738AbfA1J6S (ORCPT ); Mon, 28 Jan 2019 04:58:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56960 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726648AbfA1J6S (ORCPT ); Mon, 28 Jan 2019 04:58:18 -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 CE90FC02C019; Mon, 28 Jan 2019 09:58:17 +0000 (UTC) Received: from dhcp-128-65.nay.redhat.com (ovpn-12-122.pek2.redhat.com [10.72.12.122]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 938305C234; Mon, 28 Jan 2019 09:58:13 +0000 (UTC) Date: Mon, 28 Jan 2019 17:58:09 +0800 From: Dave Young To: Borislav Petkov Cc: Pingfan Liu , kexec@lists.infradead.org, Baoquan He , Andrew Morton , Mike Rapoport , yinghai@kernel.org, vgoyal@redhat.com, Randy Dunlap , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv7] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr Message-ID: <20190128095809.GC3732@dhcp-128-65.nay.redhat.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190125140823.GC27998@zn.tnic> User-Agent: Mutt/1.9.5 (2018-04-13) 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 [10.5.110.31]); Mon, 28 Jan 2019 09:58:17 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/25/19 at 03:08pm, 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. > > 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. Another reason is in case ,high we will need automatically reserve a region in low area for swiotlb. So for example one use crashkernel=256M,high, actual reserved memory is 256M above 4G and another 256M under 4G for swiotlb. Normally it is not necessary for most people. Thus we can not make ,high as default. Thanks Dave