linux-kernel - Re: [PATCH 2/2] ehea: add memory remove hotplug support

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Message-Id: <200802041624.31228.ossthema@de.ibm.com>
Date:	Mon, 4 Feb 2008 16:24:30 +0100
From:	Jan-Bernd Themann <ossthema@...ibm.com>
To:	michael@...erman.id.au
Cc:	Jeff Garzik <jeff@...zik.org>, Thomas Klein <tklein@...ibm.com>,
	Jan-Bernd Themann <themann@...ibm.com>,
	netdev <netdev@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-ppc <linuxppc-dev@...abs.org>,
	Christoph Raisch <raisch@...ibm.com>,
	Marcus Eder <meder@...ibm.com>
Subject: Re: [PATCH 2/2] ehea: add memory remove hotplug support

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
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