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Subject[tip: perf/core] perf/x86/rapl: Only check lower 32bits for RAPL energy counters
The following commit has been merged into the perf/core branch of tip:

Commit-ID: b6f78d3fba7f605f673185d7292d84af7576fdc1
Gitweb: https://git.kernel.org/tip/b6f78d3fba7f605f673185d7292d84af7576fdc1
Author: Zhang Rui <rui.zhang@intel.com>
AuthorDate: Fri, 05 Feb 2021 00:18:15 +08:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 10 Feb 2021 14:44:55 +01:00

perf/x86/rapl: Only check lower 32bits for RAPL energy counters

In the RAPL ENERGY_COUNTER MSR, only the lower 32bits represent the energy
counter.

On previous platforms, the higher 32bits are reverved and always return
Zero. But on Intel SapphireRapids platform, the higher 32bits are reused
for other purpose and return non-zero value.

Thus check the lower 32bits only for these ENERGY_COUTNER MSRs, to make
sure the RAPL PMU events are not added erroneously when higher 32bits
contain non-zero value.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Link: https://lkml.kernel.org/r/20210204161816.12649-2-rui.zhang@intel.com
---
arch/x86/events/rapl.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
index 7dbbeaa..7ed25b2 100644
--- a/arch/x86/events/rapl.c
+++ b/arch/x86/events/rapl.c
@@ -523,12 +523,15 @@ static bool test_msr(int idx, void *data)
return test_bit(idx, (unsigned long *) data);
}

+/* Only lower 32bits of the MSR represents the energy counter */
+#define RAPL_MSR_MASK 0xFFFFFFFF
+
static struct perf_msr intel_rapl_msrs[] = {
- [PERF_RAPL_PP0] = { MSR_PP0_ENERGY_STATUS, &rapl_events_cores_group, test_msr },
- [PERF_RAPL_PKG] = { MSR_PKG_ENERGY_STATUS, &rapl_events_pkg_group, test_msr },
- [PERF_RAPL_RAM] = { MSR_DRAM_ENERGY_STATUS, &rapl_events_ram_group, test_msr },
- [PERF_RAPL_PP1] = { MSR_PP1_ENERGY_STATUS, &rapl_events_gpu_group, test_msr },
- [PERF_RAPL_PSYS] = { MSR_PLATFORM_ENERGY_STATUS, &rapl_events_psys_group, test_msr },
+ [PERF_RAPL_PP0] = { MSR_PP0_ENERGY_STATUS, &rapl_events_cores_group, test_msr, false, RAPL_MSR_MASK },
+ [PERF_RAPL_PKG] = { MSR_PKG_ENERGY_STATUS, &rapl_events_pkg_group, test_msr, false, RAPL_MSR_MASK },
+ [PERF_RAPL_RAM] = { MSR_DRAM_ENERGY_STATUS, &rapl_events_ram_group, test_msr, false, RAPL_MSR_MASK },
+ [PERF_RAPL_PP1] = { MSR_PP1_ENERGY_STATUS, &rapl_events_gpu_group, test_msr, false, RAPL_MSR_MASK },
+ [PERF_RAPL_PSYS] = { MSR_PLATFORM_ENERGY_STATUS, &rapl_events_psys_group, test_msr, false, RAPL_MSR_MASK },
};

/*
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