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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.02.12 at 08:29, Philipp Hahn <hahn@xxxxxxxxxxxxx> wrote:
> 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.

You may want to get in touch with Daniel, who iirc started looking at
adding kexec support to the pv-ops kernel some time last year.

Jan


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