kdump: A memory hotplug issue on s390

[Simon Horman]

On Tue, Oct 25, 2011 at 07:17:17PM +0200, Michael Holzheu wrote:
> Hello Simon and Vivek,
> 
> For s390 we currently use /proc/iomem for defining the memory layout in
> the kexec elfcore header. Unfortunately this is not correct, when using
> memory hotplug. When a memory chunk is set offline (e.g. with "echo
> offline > /sys/devices/system/memory/memoryX/state") this is not
> reflected in /proc/iomem.
> 
> To fix this I could parse /sys/devices/system/memory and exclude each
> memory chunk that in not online from the /proc/iomem info. Do you think
> that this approach is fine or is there a better solution?

Hi Michael,

that sounds like a reasonable approach to me.
IIRC, kexec xen on ia64 makes use of an alternate iomem file,
and this seems to be another example of /proc/iomem not being
the right source of information.