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

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Date:   Tue, 20 Jun 2023 14:46:03 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     <peterz@...radead.org>
CC:     <ravi.bangoria@....com>, <acme@...nel.org>, <irogers@...gle.com>,
        <jolsa@...nel.org>, <namhyung@...nel.org>, <bp@...en8.de>,
        <x86@...nel.org>, <linux-perf-users@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <sandipan.das@....com>,
        <ananth.narayan@....com>, <santosh.shukla@....com>
Subject: [PATCH] perf/amd: Prevent grouping of IBS events

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@....com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
---
 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