x86: oprofile: don't set counter width from cpuid on Core2

Impact: fix stuck NMIs and non-working oprofile on certain CPUs

Resetting the counter width of the performance counters on Intel's
Core2 CPUs, breaks the delivery of NMIs, when running in x86_64 mode.

This should fix bug #12395:

  http://bugzilla.kernel.org/show_bug.cgi?id=12395

Signed-off-by: Tim Blechmann <tim@klingt.org>
Signed-off-by: Robert Richter <robert.richter@amd.com>
LKML-Reference: <20090303100412.GC10085@erda.amd.com>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 12 insertions, 2 deletions

diff --git a/arch/x86/oprofile/op_model_ppro.c b/arch/x86/oprofile/op_model_ppro.c
index e9f80c744cf3..10131fbdaada 100644
--- a/arch/x86/oprofile/op_model_ppro.c
+++ b/arch/x86/oprofile/op_model_ppro.c
@@ -78,8 +78,18 @@ static void ppro_setup_ctrs(struct op_msrs const * const msrs)
         if (cpu_has_arch_perfmon) {
                 union cpuid10_eax eax;
                 eax.full = cpuid_eax(0xa);
-                if (counter_width < eax.split.bit_width)
-                        counter_width = eax.split.bit_width;
+
+                /*
+                 * For Core2 (family 6, model 15), don't reset the
+                 * counter width:
+                 */
+                if (!(eax.split.version_id == 0 &&
+                        current_cpu_data.x86 == 6 &&
+                                current_cpu_data.x86_model == 15)) {
+
+                        if (counter_width < eax.split.bit_width)
+                                counter_width = eax.split.bit_width;
+                }
         }
 
         /* clear all counters */