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    Subject[22/89] x86, apic: use physical mode for IBM summit platforms
    2.6.31-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Suresh Siddha <suresh.b.siddha@intel.com>

    commit dfea91d5a7c795fd6f4e1a97489a98e4e767463e upstream.

    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.

    The 32-bit 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>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    arch/x86/kernel/apic/apic_flat_64.c | 5 +++++
    1 file changed, 5 insertions(+)

    --- a/arch/x86/kernel/apic/apic_flat_64.c
    +++ b/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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