linux-kernel - [Patch] convert i386 Summint subarch to use SRAT info for apicid_to

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Date:	Wed, 19 Jul 2006 17:11:13 -0700
From:	keith mannthey <kmannth@...ibm.com>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	andrew <akpm@...l.org>
Subject: [Patch] convert i386 Summint subarch to use SRAT info for
	apicid_to_node calls

Hello Andrew,
  This patch converts the i386 summit subarch apicid_to_node to use node
information provided by the SRAT.  It was discussed a little on LKML a
few weeks ago and was seen as an acceptable fix.  The current way of
obtaining the nodeid 

 static inline int apicid_to_node(int logical_apicid)
 { 
   return logical_apicid >> 5;
 }

is just not correct for all summit systems/bios.  Assuming the apicid
matches the Linux node number require a leap of faith that the bios
mapped out the apicids a set way.  Modern summit HW (IBM x460) does not
layout its bios in the manner for various reasons and is unable to boot
i386 numa.

  The best way to get the correct apicid to node information is from the
SRAT table during boot.  It lays out what apicid belongs to what node.
I use this information to create a table for use at run time. 

  The attached patch was built against 2.6.18-rc1.  It only changes the
summit subarch.  

Signed-off-by:  Keith Mannthey <kmannth@...ibm.com>

View attachment "patch-2.6.18-rc1-apicid_to_node_srat-v2" of type "text/x-patch" (3321 bytes)