linux-kernel - [tip: perf/urgent] perf/x86/rapl: fix AMD event handling

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Message-ID: <164250467243.16921.12614662338884193710.tip-bot2@tip-bot2>
Date:   Tue, 18 Jan 2022 11:17:52 -0000
From:   "tip-bot2 for Stephane Eranian" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Stephane Eranian <eranian@...gle.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/urgent] perf/x86/rapl: fix AMD event handling

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     0036fb00a756a2f6e360d44e2e3d2200a8afbc9b
Gitweb:        https://git.kernel.org/tip/0036fb00a756a2f6e360d44e2e3d2200a8afbc9b
Author:        Stephane Eranian <eranian@...gle.com>
AuthorDate:    Wed, 05 Jan 2022 10:56:59 -08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 18 Jan 2022 12:09:48 +01:00

perf/x86/rapl: fix AMD event handling

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
---
 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 85feafa..77e3a47 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);