From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
To: Dave Young <dyoung@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Baoquan He <bhe@redhat.com>, Xunlei Pang <xlpang@redhat.com>,
Atsushi Kumagai <ats-kumagai@wm.jp.nec.com>,
Petr Tesarik <ptesarik@suse.cz>,
linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
kexec@lists.infradead.org, mahesh@linux.vnet.ibm.com,
hbathini@linux.vnet.ibm.com
Subject: Re: [PATCH v3 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section
Date: Wed, 22 Mar 2017 21:48:19 +0100 [thread overview]
Message-ID: <20170322214819.0b64d49c@TP-holzheu> (raw)
In-Reply-To: <20170322043004.GB4424@dhcp-128-65.nay.redhat.com>
Am Wed, 22 Mar 2017 12:30:04 +0800
schrieb Dave Young <dyoung@redhat.com>:
> On 03/21/17 at 10:18pm, Eric W. Biederman wrote:
> > Dave Young <dyoung@redhat.com> 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
next prev parent reply other threads:[~2017-03-22 20:48 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-20 5:50 [PATCH v3 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section Xunlei Pang
2017-03-20 5:50 ` [PATCH v3 2/3] powerpc/fadump: Use the correct VMCOREINFO_NOTE_SIZE for phdr Xunlei Pang
2017-03-20 5:50 ` [PATCH v3 3/3] kdump: Relocate vmcoreinfo to the crash memory range Xunlei Pang
2017-03-21 3:33 ` [PATCH v3 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section Eric W. Biederman
2017-03-22 2:55 ` Dave Young
2017-03-22 3:18 ` Eric W. Biederman
2017-03-22 4:30 ` Dave Young
2017-03-22 9:34 ` Xunlei Pang
2017-03-22 12:15 ` Hari Bathini
2017-03-22 11:46 ` Hari Bathini
2017-03-22 20:48 ` Michael Holzheu [this message]
2017-03-23 9:23 ` Xunlei Pang
2017-03-23 17:46 ` Michael Holzheu
2017-03-24 11:03 ` Xunlei Pang
2017-03-22 8:55 ` Xunlei Pang
2017-03-22 9:16 ` Xunlei Pang
2017-03-22 9:17 ` Xunlei Pang
2017-03-21 9:27 ` Petr Tesarik
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