Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934329AbdCVLrU (ORCPT ); Wed, 22 Mar 2017 07:47:20 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:33773 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933495AbdCVLrN (ORCPT ); Wed, 22 Mar 2017 07:47:13 -0400 Subject: Re: [PATCH v3 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section To: Dave Young , "Eric W. Biederman" References: <1489989033-1179-1-git-send-email-xlpang@redhat.com> <87pohbz4lo.fsf@xmission.com> <20170322025536.GA4424@dhcp-128-65.nay.redhat.com> <87pohaxam1.fsf@xmission.com> <20170322043004.GB4424@dhcp-128-65.nay.redhat.com> Cc: Baoquan He , Xunlei Pang , Atsushi Kumagai , Petr Tesarik , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, holzheu@linux.vnet.ibm.com, kexec@lists.infradead.org From: Hari Bathini Date: Wed, 22 Mar 2017 17:16:56 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <20170322043004.GB4424@dhcp-128-65.nay.redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable x-cbid: 17032211-0020-0000-0000-000000D7565E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17032211-0021-0000-0000-000002965742 Message-Id: <0e9381e2-a44e-aa48-6463-45b571222203@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-03-22_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1702020001 definitions=main-1703220102 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1988 Lines: 44 Hi Dave, On Wednesday 22 March 2017 10:00 AM, Dave Young wrote: > On 03/21/17 at 10:18pm, Eric W. Biederman wrote: >> Dave Young writes: >> >>> On 03/20/17 at 10:33pm, Eric W. Biederman wrote: >>>> Xunlei Pang writes: >>>> >>>>> As Eric said, >>>>> "what we need to do is move the variable vmcoreinfo_note out >>>>> of the kernel's .bss section. And modify the code to regenerate >>>>> and keep this information in something like the control page. >>>>> >>>>> Definitely something like this needs a page all to itself, and ideally >>>>> far away from any other kernel data structures. I clearly was not >>>>> watching closely the data someone decided to keep this silly thing >>>>> in the kernel's .bss section." >>>>> >>>>> This patch allocates extra pages for these vmcoreinfo_XXX variables, >>>>> one advantage is that it enhances some safety of vmcoreinfo, because >>>>> vmcoreinfo now is kept far away from other kernel data structures. >>>> Can you preceed this patch with a patch that removes CRASHTIME from >>>> vmcoreinfo? If someone actually cares we can add a separate note that holds >>>> a 64bit crashtime in the per cpu notes. >>> I think makedumpfile is using it, but I also vote to remove the >>> CRASHTIME. It is better not to do this while crashing and a makedumpfile >>> userspace patch is needed to drop the use of it. >>> >>>> As we are looking at reliability concerns removing CRASHTIME should make >>>> everything in vmcoreinfo a boot time constant. Which should simplify >>>> everything considerably. >>> It is a nice improvement.. >> We also need to take a close look at what s390 is doing with vmcoreinfo. >> As apparently it is reading it in a different kind of crashdump process. > Yes, need careful review from s390 and maybe ppc64 especially about > patch 2/3, better to have comments from IBM about s390 dump tool and ppc > fadump. Added more cc. w.r.t powerpc/fadump, this patch-set works fine.. Thanks Hari