[PATCH] convert i386 Summit subarch to use SRAT info for apicid_to_node calls

Convert 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.

Signed-off-by: Keith Mannthey <kmannth@us.ibm.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 3 insertions, 1 deletions

diff --git a/include/asm-i386/mach-summit/mach_apic.h b/include/asm-i386/mach-summit/mach_apic.h
index a81b05961595..254a0fe01c6a 100644
--- a/include/asm-i386/mach-summit/mach_apic.h
+++ b/include/asm-i386/mach-summit/mach_apic.h
@@ -88,7 +88,7 @@ static inline void clustered_apic_check(void)
 
 static inline int apicid_to_node(int logical_apicid)
 {
-        return logical_apicid >> 5;          /* 2 clusterids per CEC */
+        return apicid_2_node[logical_apicid];
 }
 
 /* Mapping from cpu number to logical apicid */
diff --git a/include/asm-i386/smp.h b/include/asm-i386/smp.h
index 32ac8c91d5c5..915c26a31b79 100644
--- a/include/asm-i386/smp.h
+++ b/include/asm-i386/smp.h
@@ -46,6 +46,8 @@ extern u8 x86_cpu_to_apicid[];
 
 #define cpu_physical_id(cpu)    x86_cpu_to_apicid[cpu]
 
+extern u8 apicid_2_node[];
+
 #ifdef CONFIG_HOTPLUG_CPU
 extern void cpu_exit_clear(void);
 extern void cpu_uninit(void);