Re: [Xen-devel] [Xen-users] crashkernel doesn't work with linux-2.6.32-dom0

[Philipp Hahn <hahn@xxxxxxxxxxxxx>]

Hello,

Am Donnerstag 16 Februar 2012 02:22:30 schrieben Sie:
> On Tue, Feb 14, 2012 at 10:07 AM, Eric Camachat <eric.camachat@xxxxxxxxx> 
wrote:
> > On Tue, Feb 14, 2012 at 12:07 AM, Philipp Hahn <hahn@xxxxxxxxxxxxx> wrote:
> Try to use HYPERVISOR_kexec_op() to find out where crash buffer is.
> But it returned address that outside of total memory!

Yes, because the Hyervisor (which is running below your dom0 Linux kernel) 
reserves the memory, so not even the dom0 kernel should be able to scribble 
it. That's why you have to use the HYPERVIROS_OPs.

I've spend some time investigating this a month ago but finally did gave up. 
Here're some of my notes:
- it should be possible to write a user-space tool (like kexec), which uses 
HYPERVISOR_kexec_op() to load a crash-dump kernel.
- you would need to copy some code from the linux-kernel to fill in some data 
structures.
- the Linux kernel prepends the crash kernel with some assembly code, which 
moves it to the final location on execution. This trampolin code would 
possibly be  needed in your tool as well.

The other option I see would be to modify the current Linux kernel to use 
HYPERVISOR_kexec_op() when used as a dom0 kernel.

Sincerely
Philipp
-- 
Philipp Hahn           Open Source Software Engineer      hahn@xxxxxxxxxxxxx
Univention GmbH        Linux for Your Business        fon: +49 421 22 232- 0
Mary-Somerville-Str.1  D-28359 Bremen                 fax: +49 421 22 232-99
                                                   http://www.univention.de/

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