linux-kernel - [PATCH 3/3] perf/x86: Add CAP_NO

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Message-ID: <20231120221932.213710-3-namhyung@kernel.org>
Date:   Mon, 20 Nov 2023 14:19:32 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Mingwei Zhang <mizhang@...gle.com>
Subject: [PATCH 3/3] perf/x86: Add CAP_NO_INTERRUPT for uncore PMUs

It doesn't support sampling in uncore PMU events.  While it's
technically possible to generate interrupts, let's treat it as if it
has no interrupt in order to skip the freq adjust/unthrottling logic
in the timer handler which is only meaningful to sampling events.

Also remove the sampling event check because it'd be done in the general
code in the perf_event_open syscall.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 arch/x86/events/intel/uncore.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index 69043e02e8a7..f7e6228bd1b1 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -744,10 +744,6 @@ static int uncore_pmu_event_init(struct perf_event *event)
 	if (pmu->func_id < 0)
 		return -ENOENT;
 
-	/* Sampling not supported yet */
-	if (hwc->sample_period)
-		return -EINVAL;
-
 	/*
 	 * Place all uncore events for a particular physical package
 	 * onto a single cpu
@@ -919,7 +915,12 @@ static int uncore_pmu_register(struct intel_uncore_pmu *pmu)
 			.stop		= uncore_pmu_event_stop,
 			.read		= uncore_pmu_event_read,
 			.module		= THIS_MODULE,
-			.capabilities	= PERF_PMU_CAP_NO_EXCLUDE,
+			/*
+			 * It doesn't allow sampling for uncore events, let's
+			 * treat the PMU has no interrupts to skip them in the
+			 * perf_adjust_freq_unthr_context().
+			 */
+			.capabilities	= PERF_PMU_CAP_NO_EXCLUDE | PERF_PMU_CAP_NO_INTERRUPT,
 			.attr_update	= pmu->type->attr_update,
 		};
 	} else {
-- 
2.43.0.rc1.413.gea7ed67945-goog