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From: Badari Pulavarty <pbadari@us.ibm.com>
To: Dave Hansen <haveblue@us.ibm.com>
Cc: Christoph Raisch <RAISCH@de.ibm.com>,
	ossthema@linux.vnet.ibm.com, apw <apw@uk.ibm.com>,
	Greg KH <greg@kroah.com>, Jan-Bernd Themann <THEMANN@de.ibm.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linuxppc-dev@ozlabs.org, netdev <netdev@vger.kernel.org>,
	Thomas Q Klein <TKLEIN@de.ibm.com>,
	tklein@linux.ibm.com
Subject: Re: [PATCH] drivers/base: export gpl (un)register_memory_notifier
Date: Thu, 14 Feb 2008 09:36:15 -0800	[thread overview]
Message-ID: <1203010575.12312.6.camel@dyn9047017100.beaverton.ibm.com> (raw)
In-Reply-To: <1203009163.19205.42.camel@nimitz.home.sr71.net>

On Thu, 2008-02-14 at 09:12 -0800, Dave Hansen wrote:
..
> > > > - Use currently other not exported functions in kernel/resource.c, like
> > > >   walk_memory_resource (where we would still need the maximum
> > > possible number
> > > >   of pages NR_MEM_SECTIONS)
> > >
> > > It isn't the act of exporting that's the problem.  It's making sure that
> > > the exports won't be prone to abuse and that people are using them
> > > properly.  You should assume that you can export and use
> > > walk_memory_resource().
> > 
> > So this seems to come down to a basic question:
> > New hardware seems to have a tendency to get "private MMUs",
> > which need private mappings from the kernel address space into a
> > "HW defined address space with potentially unique characteristics"
> > RDMA in Openfabrics with global MR is the most prominent example heading
> > there
> 
> That's not a question. ;)
> 
> Please explain to me why walk_memory_resource() is insufficient for your
> needs.  I've now pointed it out to you at least 3 times.  

I am not sure what you are trying to do with walk_memory_resource(). The
behavior is different on ppc64. Hotplug memory usage assumes that all
the memory resources (all system memory, not just IOMEM) are represented
in /proc/iomem. Its the case with i386 and ia64. But on ppc64 is
contains ONLY iomem related. Paulus didn't want to export all the system
memory into /proc/iomem on ppc64. So I had to workaround by providing
arch-specific walk_memory_resource() function for ppc64.

Thanks,
Badari


  reply	other threads:[~2008-02-14 17:34 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-11 16:24 Jan-Bernd Themann
2008-02-11 16:47 ` Dave Hansen
2008-02-13 15:17   ` Jan-Bernd Themann
2008-02-13 17:05     ` Dave Hansen
2008-02-14  8:46     ` Christoph Raisch
2008-02-14 17:12       ` Dave Hansen
2008-02-14 17:36         ` Badari Pulavarty [this message]
2008-02-14 17:38           ` Dave Hansen
2008-02-15 13:22         ` Christoph Raisch
2008-02-15 16:55           ` Dave Hansen
2008-02-18 10:00             ` Jan-Bernd Themann
2008-02-20 18:14               ` Dave Hansen
2008-02-11 16:50 ` Dave Hansen
2008-02-12 18:04 ` Dave Hansen
  -- strict thread matches above, loose matches on Subject: below --
2008-02-11 15:57 Jan-Bernd Themann
2008-02-11 16:02 ` Sam Ravnborg
2008-02-11 16:04 ` Dave Hansen

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