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From: Jan-Bernd Themann <ossthema@de.ibm.com>
To: michael@ellerman.id.au
Subject: Re: [PATCH 2/2] ehea: add memory remove hotplug support
Date: Mon, 4 Feb 2008 16:24:30 +0100
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Cc: Thomas Klein <tklein@de.ibm.com>, Jeff Garzik <jeff@garzik.org>,
	Jan-Bernd Themann <themann@de.ibm.com>, netdev <netdev@vger.kernel.org>,
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On Monday 04 February 2008 15:46, Michael Ellerman wrote:
> On Mon, 2008-02-04 at 14:04 +0100, Jan-Bernd Themann wrote:
> > Add memory remove hotplug support

> > @@ -3559,6 +3578,10 @@ int __init ehea_module_init(void)
> >  	if (ret)
> >  		ehea_info("failed registering reboot notifier");
> >  
> > +	ret = register_memory_notifier(&ehea_mem_nb);
> > +	if (ret)
> > +		ehea_info("failed registering memory remove notifier");
> > 
> >  	ret = crash_shutdown_register(&ehea_crash_handler);
> >  	if (ret)
> >  		ehea_info("failed registering crash handler");
> 
> You don't do anything except print a message if the registration fails.
> What happens when someone tries to remove memory but the memory notifier
> wasn't registered properly? Bang?

In case the registration fails and somebody tries to free memory:
- Driver will not remove the affected memory from the eHEA memory region
  --> Firmware (phyp) can not free that memory (as marked as used)
  --> Therefore the removed memory could not be used in an other partition

It makes sense to allow the driver to work anyway. Having no ethernet
would not really be a good alternative.

Regards,
Jan-Bernd