From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1cqnBY-0007hb-JB for kexec@lists.infradead.org; Wed, 22 Mar 2017 20:48:51 +0000 Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v2MKdA7B065772 for ; Wed, 22 Mar 2017 16:48:27 -0400 Received: from e06smtp11.uk.ibm.com (e06smtp11.uk.ibm.com [195.75.94.107]) by mx0a-001b2d01.pphosted.com with ESMTP id 29btm534s6-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 22 Mar 2017 16:48:27 -0400 Received: from localhost by e06smtp11.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 22 Mar 2017 20:48:25 -0000 Date: Wed, 22 Mar 2017 21:48:19 +0100 From: Michael Holzheu Subject: Re: [PATCH v3 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section In-Reply-To: <20170322043004.GB4424@dhcp-128-65.nay.redhat.com> 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> MIME-Version: 1.0 Message-Id: <20170322214819.0b64d49c@TP-holzheu> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: 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 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. 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