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Date: Fri, 4 Mar 2011 13:33:29 -0800 (PST)
From: David Rientjes <rientjes@google.com>
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To: Tejun Heo <tj@kernel.org>
cc: Yinghai Lu <yinghai@kernel.org>, Ingo Molnar <mingo@elte.hu>,
        tglx@linutronix.de, "H. Peter Anvin" <hpa@zytor.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH x86/mm] x86-64, NUMA: Don't assume phys node 0 is always
 online in numa_emulation() handling
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On Fri, 4 Mar 2011, Tejun Heo wrote:

> Undetermined entries in emu_nid_to_phys[] are filled with zero
> assuming that physical node 0 is always online; however, this might
> not be true depending on hardware configuration.  Find a physical node
> which is actually online and use it instead.
> 

I still don't understand why emu_nid_to_phys[] can't return NUMA_NO_NODE 
and this needs to be done at all.  An emulated node should be mapped to a 
physical node based on the address ranges of that emulated node, so it's 
impossible for that to not map directly to a physical online node.  We 
don't support memoryless emulated nodes for hotpluggable SRAT entries.