Re: [PATCH] kexec-tools: Read always one vmcoreinfo file

[Simon Horman <horms-/R6kz+dDXgpPR4JQBCEnsQ@public.gmane.org>]

On Tue, Jul 24, 2012 at 03:54:10PM +0200, Daniel Kiper wrote:
> On Tue, Jul 24, 2012 at 10:18:34AM +0200, Petr Tesarik wrote:
> > Dne Po 23. ??ervence 2012 22:10:59 Daniel Kiper napsal(a):
> > > Hi Petr,
> > >
> > > On Mon, Jul 23, 2012 at 03:30:55PM +0200, Petr Tesarik wrote:
> > > > Dne Po 23. ??ervence 2012 14:56:07 Petr Tesarik napsal(a):
> > > > > Dne ??t 5. ??ervence 2012 14:16:35 Daniel Kiper napsal(a):
> > > > > > vmcoreinfo file could exists under /sys/kernel (valid on baremetal
> > > > > > only) and/or under /sys/hypervisor (valid when Xen dom0 is running).
> > > > > > Read only one of them. It means that only one PT_NOTE will be always
> > > > > > created. Remove extra code for second PT_NOTE creation.
> > > > >
> > > > > Hi Daniel,
> > > > >
> > > > > are you absolutely sure this is the right thing to do? IIUC these two
> > > > > VMCORINFO notes are very different. The one from /sys/kernel/vmcoreinfo
> > > > > describes the Dom0 kernel (type 'VMCOREINFO'), while the one from
> > > > > /sys/hypervisor describes the Xen hypervisor (type 'XEN_VMCOREINFO').
> > > > > If you keep only the hypervisor note, then e.g. makedumpfile won't be
> > > > > able to use dumplevel greater than 1, nor will it be able to extract
> > > > > the log buffer.
> > > >
> > > > I've just verified this, and I'm confident we have to keep both notes in
> > > > the dump file. Simon, please revert Daniel's patch to avoid regressions.
> > > >
> > > > I'm attaching a sample VMCOREINFO_XEN and VMCOREINFO to demonstrate the
> > > > difference. Note that the VMCOREINFO_XEN note is actually too big,
> > > > because Xen doesn't bother to maintain the correct note size in the note
> > > > header, so it always spans a complete page minus sizeof(Elf64_Nhdr)...
> > >
> > > [...]
> > >
> > > The problem with /sys/kernel/vmcoreinfo under Xen is that it expose invalid
> > > physical address. It breaks /proc/vmcore in crash kernel. That is why I
> > > proposed that fix. Additionally, /sys/kernel/vmcoreinfo is not available
> > > under Xen Linux Ver. 2.6.18. However, I did not do any makedumpfile tests.
> > > If you discovered any issues with my patch please drop me more details
> > > about your tests (Xen version, Linux Kernel version, makedumpfile version,
> > > command lines, config files, logs, etc.). I will be more then happy to
> > > fix/improve kexec-tools and makedumpfile.
> >
> > Hi Daniel,
> >
> > well, Linux v2.6.18 does not have /sys/kernel/vmcoreinfo, simply because the
> > VMCOREINFO infrastructure was not present in 2.6.18. It was added later with
> 
> Yep.
> 
> > commit fd59d231f81cb02870b9cf15f456a897f3669b4e, which went into 2.6.24.
> 
> Hmmm... As I know 2.6.24 does not support kexec/kdump under Xen dom0. Correct?
> 
> > I tested with the following combinations:
> >
> > * xen-3.3.1 + kernel-xen-2.6.27.54 + kexec-tools-2.0.0 + makedumpfile-1.3.1
> > * xen-4.0.3 + kernel-xen-2.6.32.59 + kexec-tools-2.0.0 + makedumpfile-1.3.1
> > * xen-4.1.2 + kernel-xen-3.0.34 + kexec-tools-2.0.0 + makedumpfile-1.4.0
> >
> > These versions correspond to SLES11-GA, SLES11-SP1 and SLES11-SP2,
> > respectively. All of them work just fine and save both ELF notes into the
> > dump.
> 
> Could you test current kexec-tools development version and
> latest makedumpfile version on latest SLES version?
> 
> > What do you mean by "invalid physical address"? I'm getting the correct
> > physical address under Xen. Obviously, it must be translated to machine
> > addresses if you need them from the secondary kernel.
> 
> Correct vmcoreinfo address should be established by calling
> HYPERVISOR_kexec_op(KEXEC_CMD_kexec_get_range, KEXEC_RANGE_MA_VMCOREINFO).
> Address exposed by /sys/kernel/vmcoreinfo is calculated in other way.
> /sys/hypervisor/vmcoreinfo does it correctly (in older implementations
> and in my new upstream implementation which I am going to post shortly).
> 
> > Anyway, let me re-install my test system and send all the necessary
> > information. What kind of log files are you interested in?
> 
> If you spot any error in any logfile which in your opinion
> is relevent to our testes please send me it.

Hi,

is there any consensus on what to do here?