> Following patch breaks real NUMA on multi-node CPUs like AMD
> Magny-Cours and should be reverted (or changed to just take effect in
> case of numa=fake):
> 
>   commit 7d6b46707f2491a94f4bd3b4329d2d7f809e9368
>   Author: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>   Date:   Fri Apr 15 20:39:01 2011 +0900
> 
>     x86, NUMA: Fix fakenuma boot failure
> 
>     ...
> 
>     Thus, this patch implements a reassignment of node-ids if buggy firmware
>     or numa emulation makes wrong cpu node map. Tt enforce all logical cpus
>     in the same physical cpu share the same node.
> 
>     ...
> 
>   +static void __cpuinit check_cpu_siblings_on_same_node(int cpu1, int cpu2)
>   +{
>   +       int node1 = early_cpu_to_node(cpu1);
>   +       int node2 = early_cpu_to_node(cpu2);
>   +
>   +       /*
>   +        * Our CPU scheduler assumes all logical cpus in the same physical cpu
>   +        * share the same node. But, buggy ACPI or NUMA emulation might assign
>   +        * them to different node. Fix it.
>   +        */
> 
>    ...
> 
> This is a false assumption. Magny-Cours has two nodes in the same
> physical package. The scheduler was (kind of) fixed to work around
> this boot problem for multi-node CPUs (with 2.6.32). 

I agree we have to fix this ASAP. I also think we have to avoid reintroduce 
the same again. Can you please tell me the commit-id of this one? 

> If this is also
> an issue with wrong cpu node maps in case of NUMA emulation this might
> be fixed similar or this quirk should only be applied in case of NUMA
> emulation.

Indeed.

Tejun, Do you remember I sent numa emulation specific patch at first. now
I'm beside with Andreas. Because I bet current numa fallback code (you 
pointed out one) has no user. 

Or, please let us know if you have an alternative patch.



Attached revert and fakenuma spefic fix patches.
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