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 Tested-by: Ananth N Mavinakayanahalli Cc: Chris McDermott Cc: Yinghai Lu 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/