From: Kan Liang <kan.li...@linux.intel.com>
Current perf doesn't check the index of a Topdown metrics event before
updating the event. A perf tool user may get a value from an unsupported
Topdown metrics event.
For example, the L2 topdown event, cpu/event=0x00,umask=0x84/, is not
supported on Ice Lake. A perf tool user may mistakenly use the
unsupported events via RAW format. In this case, the scheduler follows
the unknown event handling and assigns a GP counter to the event. The
icl_get_topdown_value() returns the value of the slots to the event.
The perf tool user will get the value for the unsupported
Topdown metrics event.
Add a check in the __icl_update_topdown_event() and avoid updating
unsupported events.
Signed-off-by: Kan Liang <kan.li...@linux.intel.com>
---
arch/x86/events/intel/core.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 8eba41b..b02d482 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2319,6 +2319,17 @@ static void __icl_update_topdown_event(struct perf_event
*event,
{
u64 delta, last = 0;
+ /*
+ * Although the unsupported topdown events are not exposed to users,
+ * users may mistakenly use the unsupported events via RAW format.
+ * For example, using L2 topdown event, cpu/event=0x00,umask=0x84/,
+ * on Ice Lake. In this case, the scheduler follows the unknown
+ * event handling and assigns a GP counter to the event.
+ * Check the case, and avoid updating unsupported events.
+ */
+ if (event->hw.idx < INTEL_PMC_IDX_FIXED)
+ return;
+
delta = icl_get_topdown_value(event, slots, metrics);
if (last_slots)
last = icl_get_topdown_value(event, last_slots, last_metrics);
--
2.7.4
