[patch 1/2] x86, apic: use physical mode for IBM summit platforms

From: Suresh Siddha
Date: Mon Jan 18 2010 - 15:26:36 EST

Chris McDermott from IBM confirmed that hurricane chipset in IBM summit
platforms doesn't support logical flat mode. Irrespective of the other things
like apic_id's, total number of logical cpu's, Linux kernel should default
to physical mode for this system. 32bit kernel does so using the OEM checks
for the IBM summit platform. Add a similar OEM platform check for the 64bit
kernel too. Otherwise the linux kernel boot can hang on this platform under
certain bios/platform settings.

Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
Tested-by: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Cc: Chris McDermott <lcm@xxxxxxxxxxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: stable@xxxxxxxxxx
arch/x86/kernel/apic/apic_flat_64.c | 5 +++++
1 file changed, 5 insertions(+)

Index: tip/arch/x86/kernel/apic/apic_flat_64.c
--- tip.orig/arch/x86/kernel/apic/apic_flat_64.c
+++ tip/arch/x86/kernel/apic/apic_flat_64.c
@@ -240,6 +240,11 @@ static int physflat_acpi_madt_oem_check(
printk(KERN_DEBUG "system APIC only can use physical flat");
return 1;
+ if (!strncmp(oem_id, "IBM", 3) && !strncmp(oem_table_id, "EXA", 3)) {
+ printk(KERN_DEBUG "IBM Summit detected, will use apic physical");
+ return 1;
+ }

return 0;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/