linux-kernel - [PATCH 1/2] perf/x86/cstate: Allow reading the package statistics from local CPU

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Date:   Wed, 23 Aug 2023 08:56:52 +0300
From:   Tero Kristo <tero.kristo@...ux.intel.com>
To:     dave.hansen@...ux.intel.com, tglx@...utronix.de, x86@...nel.org,
        bp@...en8.de
Cc:     artem.bityutskiy@...ux.intel.com, acme@...nel.org,
        bpf@...r.kernel.org, namhyung@...nel.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        irogers@...gle.com, hpa@...or.com, mark.rutland@....com,
        jolsa@...nel.org, adrian.hunter@...el.com,
        alexander.shishkin@...ux.intel.com, peterz@...radead.org,
        Kan Liang <kan.liang@...el.com>
Subject: [PATCH 1/2] perf/x86/cstate: Allow reading the package statistics from local CPU

The MSR registers for reading the package residency counters are
available on every CPU of the package. To avoid doing unnecessary SMP
calls to read the values for these from the various CPUs inside a
package, allow reading them from any CPU of the package.

Signed-off-by: Tero Kristo <tero.kristo@...ux.intel.com>
Suggested-by: Kan Liang <kan.liang@...el.com>
---
 arch/x86/events/intel/cstate.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/events/intel/cstate.c b/arch/x86/events/intel/cstate.c
index 835862c548cc..5cfe021edc65 100644
--- a/arch/x86/events/intel/cstate.c
+++ b/arch/x86/events/intel/cstate.c
@@ -336,6 +336,9 @@ static int cstate_pmu_event_init(struct perf_event *event)
 		cfg = array_index_nospec((unsigned long)cfg, PERF_CSTATE_PKG_EVENT_MAX);
 		if (!(pkg_msr_mask & (1 << cfg)))
 			return -EINVAL;
+
+		event->event_caps |= PERF_EV_CAP_READ_ACTIVE_PKG;
+
 		event->hw.event_base = pkg_msr[cfg].msr;
 		cpu = cpumask_any_and(&cstate_pkg_cpu_mask,
 				      topology_die_cpumask(event->cpu));
-- 
2.25.1