Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933730AbdCWJVT (ORCPT ); Thu, 23 Mar 2017 05:21:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56540 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932070AbdCWJVQ (ORCPT ); Thu, 23 Mar 2017 05:21:16 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 640C6437F7C Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=xpang@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 640C6437F7C Reply-To: xlpang@redhat.com Subject: Re: [PATCH v3 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section 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> <20170322214819.0b64d49c@TP-holzheu> To: Michael Holzheu , Dave Young Cc: Baoquan He , Xunlei Pang , Atsushi Kumagai , Petr Tesarik , linux-kernel@vger.kernel.org, "Eric W. Biederman" , hbathini@linux.vnet.ibm.com, akpm@linux-foundation.org, kexec@lists.infradead.org From: Xunlei Pang Message-ID: <58D39429.9020200@redhat.com> Date: Thu, 23 Mar 2017 17:23:53 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20170322214819.0b64d49c@TP-holzheu> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 23 Mar 2017 09:21:11 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2544 Lines: 71 On 03/23/2017 at 04:48 AM, Michael Holzheu wrote: > Am Wed, 22 Mar 2017 12:30:04 +0800 > schrieb Dave Young : > >> On 03/21/17 at 10:18pm, Eric W. Biederman wrote: >>> Dave Young writes: >>> > [snip] > >>>> 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. > On s390 we have at least an issue with patch 1/3. For stand-alone dump > and also because we create the ELF header for kdump in the new > kernel we save the pointer to the vmcoreinfo note in the old kernel on a > defined memory address in our absolute zero lowcore. > > This is done in arch/s390/kernel/setup.c: > > static void __init setup_vmcoreinfo(void) > { > mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note()); > } > > Since with patch 1/3 paddr_vmcoreinfo_note() returns NULL at this point in > time we have a problem here. > > To solve this - I think - we could move the initialization to > arch/s390/kernel/machine_kexec.c: > > void arch_crash_save_vmcoreinfo(void) > { > VMCOREINFO_SYMBOL(lowcore_ptr); > VMCOREINFO_SYMBOL(high_memory); > VMCOREINFO_LENGTH(lowcore_ptr, NR_CPUS); > mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note()); > } > > Probably related to this is my observation that patch 3/3 leads to > an empty VMCOREINFO note for kdump on s390. The note is there ... > > # readelf -n /var/crash/127.0.0.1-2017-03-22-21:14:39/vmcore | grep VMCORE > VMCOREINFO 0x0000068e Unknown note type: (0x00000000) > > But it contains only zeros. Yes, this is a good catch, I will do more tests. Thanks, Xunlei > > Unfortunately I have not yet understood the reason for this. > > Michael > > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec