linux-kernel - [PATCH AUTOSEL 5.15 15/41] perf/x86/rapl: fix AMD event handling

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Message-Id: <20220203203245.3007-15-sashal@kernel.org>
Date:   Thu,  3 Feb 2022 15:32:19 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Stephane Eranian <eranian@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sasha Levin <sashal@...nel.org>, mingo@...hat.com,
        acme@...nel.org, tglx@...utronix.de, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org,
        linux-perf-users@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 15/41] perf/x86/rapl: fix AMD event handling

From: Stephane Eranian <eranian@...gle.com>

[ Upstream commit 0036fb00a756a2f6e360d44e2e3d2200a8afbc9b ]

The RAPL events exposed under /sys/devices/power/events should only reflect
what the underlying hardware actually support. This is how it works on Intel
RAPL and Intel core/uncore PMUs in general.
But on AMD, this was not the case. All possible RAPL events were advertised.

This is what it showed on an AMD Fam17h:
$ ls /sys/devices/power/events/
energy-cores        energy-gpu          energy-pkg          energy-psys
energy-ram          energy-cores.scale  energy-gpu.scale    energy-pkg.scale
energy-psys.scale   energy-ram.scale    energy-cores.unit   energy-gpu.unit
energy-pkg.unit     energy-psys.unit    energy-ram.unit

Yet, on AMD Fam17h, only energy-pkg is supported.

This patch fixes the problem. Given the way perf_msr_probe() works, the
amd_rapl_msrs[] table has to have all entries filled out and in particular
the group field, otherwise perf_msr_probe() defaults to making the event
visible.

With the patch applied, the kernel now only shows was is actually supported:

$ ls /sys/devices/power/events/
energy-pkg  energy-pkg.scale  energy-pkg.unit

The patch also uses the RAPL_MSR_MASK because only the 32-bits LSB of the
RAPL counters are relevant when reading power consumption.

Signed-off-by: Stephane Eranian <eranian@...gle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20220105185659.643355-1-eranian@google.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/events/rapl.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
index 85feafacc445d..77e3a47af5ad5 100644
--- a/arch/x86/events/rapl.c
+++ b/arch/x86/events/rapl.c
@@ -536,11 +536,14 @@ static struct perf_msr intel_rapl_spr_msrs[] = {
  * - perf_msr_probe(PERF_RAPL_MAX)
  * - want to use same event codes across both architectures
  */
-static struct perf_msr amd_rapl_msrs[PERF_RAPL_MAX] = {
-	[PERF_RAPL_PKG]  = { MSR_AMD_PKG_ENERGY_STATUS,  &rapl_events_pkg_group,   test_msr },
+static struct perf_msr amd_rapl_msrs[] = {
+	[PERF_RAPL_PP0]  = { 0, &rapl_events_cores_group, 0, false, 0 },
+	[PERF_RAPL_PKG]  = { MSR_AMD_PKG_ENERGY_STATUS,  &rapl_events_pkg_group,   test_msr, false, RAPL_MSR_MASK },
+	[PERF_RAPL_RAM]  = { 0, &rapl_events_ram_group,   0, false, 0 },
+	[PERF_RAPL_PP1]  = { 0, &rapl_events_gpu_group,   0, false, 0 },
+	[PERF_RAPL_PSYS] = { 0, &rapl_events_psys_group,  0, false, 0 },
 };
 
-
 static int rapl_cpu_offline(unsigned int cpu)
 {
 	struct rapl_pmu *pmu = cpu_to_rapl_pmu(cpu);
-- 
2.34.1