Subject: Re: [PATCH] powerpc: fix numa distance for form0 device tree

From: Greg KH <[email-masked]>
Date: Mon, 6 May 2013 21:06:15 -0700

On Tue, May 07, 2013 at 01:49:34PM +1000, Michael Ellerman wrote:
> From: Vaidyanathan Srinivasan <[email-masked]>
> 
> Commit 7122beeee7bc1757682049780179d7c216dd1c83 upstream.
> 
> The following commit breaks numa distance setup for old powerpc
> systems that use form0 encoding in device tree.
> 
> commit 41eab6f88f24124df89e38067b3766b7bef06ddb
> powerpc/numa: Use form 1 affinity to setup node distance
> 
> Device tree node /rtas/ibm,associativity-reference-points would
> index into /cpus/PowerPCxxxx/ibm,associativity based on form0 or
> form1 encoding detected by ibm,architecture-vec-5 property.
> 
> All modern systems use form1 and current kernel code is correct.
> However, on older systems with form0 encoding, the numa distance
> will get hard coded as LOCAL_DISTANCE for all nodes.  This causes
> task scheduling anomaly since scheduler will skip building numa
> level domain (topmost domain with all cpus) if all numa distances
> are same.  (value of 'level' in sched_init_numa() will remain 0)
> 
> Prior to the above commit:
> ((from) == (to) ? LOCAL_DISTANCE : REMOTE_DISTANCE)
> 
> Restoring compatible behavior with this patch for old powerpc systems
> with device tree where numa distance are encoded as form0.
> 
> Signed-off-by: Vaidyanathan Srinivasan <[email-masked]>
> Signed-off-by: Michael Ellerman <[email-masked]>
> ---
>  arch/powerpc/mm/numa.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

What stable tree should this be applied to?

thanks,

greg k-h