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Subject[patch 1/2] x86, apic: use physical mode for IBM summit platforms
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@intel.com>
Tested-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Chris McDermott <lcm@linux.vnet.ibm.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: stable@kernel.org
---
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;
+ }
#endif

return 0;



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