[tip:perf/pebs] perf, x86: Disable PEBS on clovertown chips

tip-bot for Peter Zijlstra
2010-03-10T13:21:58Z

Commit-ID: 3c44780b220e876b01e39d4028cd6f4205fbf5d6
Gitweb: http://git.kernel.org/tip/3c44780b220e876b01e39d4028cd6f4205fbf5d6
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Thu, 4 Mar 2010 21:49:01 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 10 Mar 2010 13:23:35 +0100

perf, x86: Disable PEBS on clovertown chips

This CPU has just too many handycaps to be really useful.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: paulus@samba.org
Cc: eranian@google.com
Cc: robert.richter@amd.com
Cc: fweisbec@gmail.com
LKML-Reference: <20100305154128.890278662@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/kernel/cpu/perf_event.c | 4 ++++
arch/x86/kernel/cpu/perf_event_intel.c | 27 +++++++++++++++++++++++++++
2 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 7b5430b..335ee1d 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -197,6 +197,7 @@ struct x86_pmu {
void (*put_event_constraints)(struct cpu_hw_events *cpuc,
struct perf_event *event);
struct event_constraint *event_constraints;
+ void (*quirks)(void);

void (*cpu_prepare)(int cpu);
void (*cpu_starting)(int cpu);
@@ -1373,6 +1374,9 @@ void __init init_hw_perf_events(void)

pr_cont("%s PMU driver.\n", x86_pmu.name);

+ if (x86_pmu.quirks)
+ x86_pmu.quirks();
+
if (x86_pmu.num_events > X86_PMC_MAX_GENERIC) {
WARN(1, KERN_ERR "hw perf events %d > max(%d), clipping!",
x86_pmu.num_events, X86_PMC_MAX_GENERIC);
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 246c072..224c952 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -792,6 +792,32 @@ static __initconst struct x86_pmu intel_pmu = {
.cpu_dying = fini_debug_store_on_cpu,
};

+static void intel_clovertown_quirks(void)
+{
+ /*
+ * PEBS is unreliable due to:
+ *
+ * AJ67 - PEBS may experience CPL leaks
+ * AJ68 - PEBS PMI may be delayed by one event
+ * AJ69 - GLOBAL_STATUS[62] will only be set when DEBUGCTL[12]
+ * AJ106 - FREEZE_LBRS_ON_PMI doesn't work in combination with PEBS
+ *
+ * AJ67 could be worked around by restricting the OS/USR flags.
+ * AJ69 could be worked around by setting PMU_FREEZE_ON_PMI.
+ *
+ * AJ106 could possibly be worked around by not allowing LBR
+ * usage from PEBS, including the fixup.
+ * AJ68 could possibly be worked around by always programming
+ * a pebs_event_reset[0] value and coping with the lost events.
+ *
+ * But taken together it might just make sense to not enable PEBS on
+ * these chips.
+ */
+ printk(KERN_WARNING "PEBS disabled due to CPU errata.\n");
+ x86_pmu.pebs = 0;
+ x86_pmu.pebs_constraints = NULL;
+}
+
static __init int intel_pmu_init(void)
{
union cpuid10_edx edx;
@@ -856,6 +882,7 @@ static __init int intel_pmu_init(void)
break;

case 15: /* original 65 nm celeron/pentium/core2/xeon, "Merom"/"Conroe" */
+ x86_pmu.quirks = intel_clovertown_quirks;
case 22: /* single-core 65 nm celeron/core2solo "Merom-L"/"Conroe-L" */
case 23: /* current 45 nm celeron/core2/xeon "Penryn"/"Wolfdale" */
case 29: /* six-core 45 nm xeon "Dunnington" */