x86, amd: Fix panic on AMD CPU family 0x15

[The mainline kernel doesn't have this problem. Commit "(23588c3) x86,
amd: Add support for CPUID topology extension of AMD CPUs" removed the
family check. But 2.6.32.y needs to be fixed.]

This CPU family check is not required -- existence of the NodeId MSR
is indicated by a CPUID feature flag which is already checked in
amd_fixup_dcm() -- and it needlessly prevents amd_fixup_dcm() to be
called for newer AMD CPUs.

In worst case this can lead to a panic in the scheduler code for AMD
family 0x15 multi-node AMD CPUs. I just have a picture of VGA console
output so I can't copy-and-paste it herein, but the call stack of such
a panic looked like:

  do_divide_error
  ...
  find_busiest_group
  run_rebalance_domains
  ...
  apic_timer_interrupt
  ...
  cpu_idle

The mainline kernel doesn't have this problem. Commit "(23588c3) x86,
amd: Add support for CPUID topology extension of AMD CPUs" removed the
family check. But 2.6.32.y needs to be fixed.

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index e485825130d2c8ee9b5d278717deca21ae2116f4..d11629a89b0396fdb4de877ab1255d3f6394e2dc 100644 (file)
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -305,8 +305,7 @@ static void __cpuinit amd_detect_cmp(struct cpuinfo_x86 *c)
        /* use socket ID also for last level cache */
        per_cpu(cpu_llc_id, cpu) = c->phys_proc_id;
        /* fixup topology information on multi-node processors */
-       if ((c->x86 == 0x10) && (c->x86_model == 9))
-               amd_fixup_dcm(c);
+       amd_fixup_dcm(c);
 #endif
 }