linux-kernel - [PATCH] perf/x86/intel: Check perf metrics feature for each CPU

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Message-Id: <20201001211711.25708-1-kan.liang@linux.intel.com>
Date:   Thu,  1 Oct 2020 14:17:11 -0700
From:   kan.liang@...ux.intel.com
To:     peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     ak@...ux.intel.com, Kan Liang <kan.liang@...ux.intel.com>
Subject: [PATCH] perf/x86/intel: Check perf metrics feature for each CPU

From: Kan Liang <kan.liang@...ux.intel.com>

It might be possible that different CPUs have different CPU metrics on a
platform. In this case, writing the GLOBAL_CTRL_EN_PERF_METRICS bit to
the GLOBAL_CTRL register of a CPU, which doesn't support the TopDown
perf metrics feature, causes MSR access error.

Current TopDown perf metrics feature is enumerated using the boot CPU's
PERF_CAPABILITIES MSR. The MSR only indicates the boot CPU supports this
feature.

Check the PERF_CAPABILITIES MSR for each CPU. If any CPU doesn't support
the perf metrics feature, disable the feature globally.

Fixes: 59a854e2f3b9 ("perf/x86/intel: Support TopDown metrics on Ice Lake")
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
---
 arch/x86/events/intel/core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 4def6fa63875..4d70c7d6c750 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -4083,6 +4083,17 @@ static void intel_pmu_cpu_starting(int cpu)
 	if (x86_pmu.counter_freezing)
 		enable_counter_freeze();
 
+	/* Disable perf metrics if any added CPU doesn't support it. */
+	if (x86_pmu.intel_cap.perf_metrics) {
+		union perf_capabilities perf_cap;
+
+		rdmsrl(MSR_IA32_PERF_CAPABILITIES, perf_cap.capabilities);
+		if (!perf_cap.perf_metrics) {
+			x86_pmu.intel_cap.perf_metrics = 0;
+			x86_pmu.intel_ctrl &= ~(1ULL << GLOBAL_CTRL_EN_PERF_METRICS);
+		}
+	}
+
 	if (!cpuc->shared_regs)
 		return;
 
-- 
2.17.1