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>

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 */