[PATCH] perf/amd: Prevent grouping of IBS events

From: Ravi Bangoria
Date: Tue Jun 20 2023 - 05:17:49 EST


IBS PMUs can have only one event active at any point in time. Restrict
grouping of multiple IBS events.

Reported-by: Sandipan Das <sandipan.das@xxxxxxx>
Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxx>
---
arch/x86/events/amd/ibs.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index 371014802191..74e664266753 100644
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -247,11 +247,33 @@ int forward_event_to_ibs(struct perf_event *event)
return -ENOENT;
}

+/*
+ * Grouping of IBS events is not possible since IBS can have only
+ * one event active at any point in time.
+ */
+static int validate_group(struct perf_event *event)
+{
+ struct perf_event *sibling;
+
+ if (event->group_leader == event)
+ return 0;
+
+ if (event->group_leader->pmu == event->pmu)
+ return -EINVAL;
+
+ for_each_sibling_event(sibling, event->group_leader) {
+ if (sibling->pmu == event->pmu)
+ return -EINVAL;
+ }
+ return 0;
+}
+
static int perf_ibs_init(struct perf_event *event)
{
struct hw_perf_event *hwc = &event->hw;
struct perf_ibs *perf_ibs;
u64 max_cnt, config;
+ int ret;

perf_ibs = get_ibs_pmu(event->attr.type);
if (!perf_ibs)
@@ -265,6 +287,10 @@ static int perf_ibs_init(struct perf_event *event)
if (config & ~perf_ibs->config_mask)
return -EINVAL;

+ ret = validate_group(event);
+ if (ret)
+ return ret;
+
if (hwc->sample_period) {
if (config & perf_ibs->cnt_mask)
/* raw max_cnt may not be set */
--
2.41.0