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 78B9DC169C4 for ; Thu, 31 Jan 2019 22:28:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5208B20881 for ; Thu, 31 Jan 2019 22:28:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729690AbfAaW2C (ORCPT ); Thu, 31 Jan 2019 17:28:02 -0500 Received: from mx0b-002e3701.pphosted.com ([148.163.143.35]:43092 "EHLO mx0b-002e3701.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725776AbfAaW2C (ORCPT ); Thu, 31 Jan 2019 17:28:02 -0500 Received: from pps.filterd (m0134424.ppops.net [127.0.0.1]) by mx0b-002e3701.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x0VMRZjL031650; Thu, 31 Jan 2019 22:27:35 GMT Received: from g9t5008.houston.hpe.com (g9t5008.houston.hpe.com [15.241.48.72]) by mx0b-002e3701.pphosted.com with ESMTP id 2qc71yhats-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 31 Jan 2019 22:27:35 +0000 Received: from g4t3433.houston.hpecorp.net (g4t3433.houston.hpecorp.net [16.208.49.245]) by g9t5008.houston.hpe.com (Postfix) with ESMTP id BDC7C4F; Thu, 31 Jan 2019 22:27:34 +0000 (UTC) Received: from anatevka (anatevka.americas.hpqcorp.net [10.34.81.61]) by g4t3433.houston.hpecorp.net (Postfix) with ESMTP id 06B6749; Thu, 31 Jan 2019 22:27:32 +0000 (UTC) Date: Thu, 31 Jan 2019 15:27:32 -0700 From: Jerry Hoemann To: Borislav Petkov Cc: Dave Young , x86@kernel.org, Baoquan He , Randy Dunlap , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Pingfan Liu , Mike Rapoport , Andrew Morton , yinghai@kernel.org, vgoyal@redhat.com Subject: Re: [PATCHv7] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr Message-ID: <20190131222732.GA946@anatevka> Reply-To: Jerry.Hoemann@hpe.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> <20190131075907.GB19091@dhcp-128-65.nay.redhat.com> <20190131105732.GC6749@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190131105732.GC6749@zn.tnic> User-Agent: Mutt/1.10.1 (2018-07-13) X-HPE-SCL: -1 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-01-31_12:,, 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=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=649 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901310163 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 31, 2019 at 11:57:32AM +0100, Borislav Petkov wrote: > On Thu, Jan 31, 2019 at 03:59:07PM +0800, Dave Young wrote: > > As Pingfan/me mentioned in another reply, there are two reasons: > > 1. old kexec-tools can not load kernel to high memory > > 2. ,high will not work on some systems without some amounts of low > > memory so it nees reserve extra low memory, it is bad for people who do > > not want it. > > Let's see: we don't enable high by default because of old kexec-tools > and some systems which do some funky reservations. > > But this patch kinda enables high by trying a couple more regions. > > So we don't really need this - we simply need to tell people to use high > if it fails with KASLR, AFAICT. Borris, The testing I've done shows that the allocation failure caused by KASLR is intermittent. On one SUT that I've seen this issue on, the crash kernel allocation fails less than 10% of the time. So even if a system administrator is diligent and tests that a chosen kdump configuration works, that configuration might not work on some random reboot 7 months in the future. Unfortunately, that will be the time that the system crashes and we won't be able to collect the crash dump due to the crashkernel allocation failure. Jerry -- ----------------------------------------------------------------------------- Jerry Hoemann Software Engineer Hewlett Packard Enterprise -----------------------------------------------------------------------------