Re: [Lhms-devel] Re: [PATCH] register hot-added memory to iomem resource

[Vivek Goyal <vgoyal@in.ibm.com>]

On Fri, Apr 28, 2006 at 09:27:54AM +0900, KAMEZAWA Hiroyuki wrote:
> On Thu, 27 Apr 2006 16:01:30 -0700
> Andrew Morton <akpm@osdl.org> wrote:
> 
> > KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > >
> > > This patch registers hot-added memory to iomem_resource.
> > > By this, /proc/iomem can show hot-added memory.
> > > This patch is against 2.6.17-rc2-mm1.
> > > 
> > > Note: kdump uses /proc/iomem to catch memory range when it is installed.
> > >       So, kdump should be re-installed after /proc/iomem change.
> > > 
> > 
> > What do you mean by "kdump should be reinstalled"?  The kdump userspace
> > tools need to re-run kexec_load()?
> > 
> yes. I heard an admin has to re-run kexec_load.
> - http://www.uwsg.indiana.edu/hypermail/linux/kernel/0604.0/0821.html
> - http://www.uwsg.indiana.edu/hypermail/linux/kernel/0604.0/0829.html
> Added CC to ebiederm@xmission.com, nanhai.zou@intel.com
> 
> > If so, why?
> > 
> It reads physical memory list from /proc/iomem now.
> The physical memory list is read and saved at kdump kernel loading time
> instead of crashing time. 
> 

True. If some meory is added, kdump kernel has to be re-loaded.

> > And how is kdump to know that memory was hot-added?  Do we generate a
> > hotplug event?
> > 
> A user program has to make memory section online from sysfs , anyway.
> 
> The hotplug script for memory hotplug will run at memory hotplug event 
> from ACPI. If a user uses /probe interface (powerpc, x86_64),
> he knows what he does. 
> 
> hot-add -> online memory -> kexec_load() is a scenario I think of.
> 

I will look into it.

Thanks
Vivek