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Date: Tue, 7 May 2013 14:23:15 +1000
From: Michael Ellerman <michael@ellerman.id.au>
To: Greg KH <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] powerpc: fix numa distance for form0 device tree
Message-ID: <20130507042315.GC12079@concordia>
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Cc: linuxppc-dev@ozlabs.org, Anton Blanchard <anton@samba.org>,
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On Mon, May 06, 2013 at 09:06:15PM -0700, Greg KH wrote:
> On Tue, May 07, 2013 at 01:49:34PM +1000, Michael Ellerman wrote:
> > From: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
> > 
> > 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 <svaidy@linux.vnet.ibm.com>
> > Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
> > ---
> >  arch/powerpc/mm/numa.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> What stable tree should this be applied to?

All of them please.

cheers