linux-kernel - [PATCH] perf/x86/rapl: Fix the error checking order

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Message-ID: <20250129080513.30353-1-dhananjay.ugwekar@amd.com>
Date: Wed, 29 Jan 2025 08:05:14 +0000
From: Dhananjay Ugwekar <dhananjay.ugwekar@....com>
To: <peterz@...radead.org>, <mingo@...hat.com>, <rui.zhang@...el.com>,
	<irogers@...gle.com>, <bp@...en8.de>
CC: <gautham.shenoy@....com>, <ravi.bangoria@....com>, <x86@...nel.org>,
	<linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	"Dhananjay Ugwekar" <dhananjay.ugwekar@....com>, Koichiro Den
	<koichiro.den@...onical.com>
Subject: [PATCH] perf/x86/rapl: Fix the error checking order

After the commit b4943b8bfc41 ("perf/x86/rapl: Add core energy counter
support for AMD CPUs"), the default "perf record"/"perf top" command is
broken in systems where there isn't a PMU registered for type
PERF_TYPE_RAW.

This is due to the change in order of error checks in rapl_pmu_event_init()
Due to which we return -EINVAL instead of -ENOENT, when we reach here from
the fallback loop in perf_init_event().

Move the "PMU and event type match" back to the beginning of the function
so that we return -ENOENT early on.

Reported-by: Koichiro Den <koichiro.den@...onical.com>
Closes: https://lore.kernel.org/all/uv7mz6vew2bzgre5jdpmwldxljp5djzmuiksqdcdwipfm4zm7w@ribobcretidk/
Fixes: b4943b8bfc41 ("perf/x86/rapl: Add core energy counter support for AMD CPUs")
Signed-off-by: Dhananjay Ugwekar <dhananjay.ugwekar@....com>
---
 arch/x86/events/rapl.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
index d3bb3865c1b1..4952faf03e82 100644
--- a/arch/x86/events/rapl.c
+++ b/arch/x86/events/rapl.c
@@ -370,6 +370,10 @@ static int rapl_pmu_event_init(struct perf_event *event)
 	unsigned int rapl_pmu_idx;
 	struct rapl_pmus *rapl_pmus;
 
+	/* only look at RAPL events */
+	if (event->attr.type != event->pmu->type)
+		return -ENOENT;
+
 	/* unsupported modes and filters */
 	if (event->attr.sample_period) /* no sampling */
 		return -EINVAL;
@@ -387,10 +391,6 @@ static int rapl_pmu_event_init(struct perf_event *event)
 	rapl_pmus_scope = rapl_pmus->pmu.scope;
 
 	if (rapl_pmus_scope == PERF_PMU_SCOPE_PKG || rapl_pmus_scope == PERF_PMU_SCOPE_DIE) {
-		/* only look at RAPL package events */
-		if (event->attr.type != rapl_pmus_pkg->pmu.type)
-			return -ENOENT;
-
 		cfg = array_index_nospec((long)cfg, NR_RAPL_PKG_DOMAINS + 1);
 		if (!cfg || cfg >= NR_RAPL_PKG_DOMAINS + 1)
 			return -EINVAL;
@@ -398,10 +398,6 @@ static int rapl_pmu_event_init(struct perf_event *event)
 		bit = cfg - 1;
 		event->hw.event_base = rapl_model->rapl_pkg_msrs[bit].msr;
 	} else if (rapl_pmus_scope == PERF_PMU_SCOPE_CORE) {
-		/* only look at RAPL core events */
-		if (event->attr.type != rapl_pmus_core->pmu.type)
-			return -ENOENT;
-
 		cfg = array_index_nospec((long)cfg, NR_RAPL_CORE_DOMAINS + 1);
 		if (!cfg || cfg >= NR_RAPL_PKG_DOMAINS + 1)
 			return -EINVAL;
-- 
2.34.1