[PATCH 4/5] perf, x86: Add INST_RETIRED.ALL workarounds

From: Andi Kleen
Date: Wed Aug 13 2014 - 21:18:40 EST


From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

On Broadwell INST_RETIRED.ALL cannot be used with any period
that doesn't have the lowest 6 bits cleared. And the period
should not be smaller than 128.

Add a new callback to enforce this, and set it for Broadwell.

This is erratum BDM57 and BDM11.

v2: Use correct event name in description. Use EVENT() macro.
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/perf_event.c | 3 +++
arch/x86/kernel/cpu/perf_event.h | 1 +
arch/x86/kernel/cpu/perf_event_intel.c | 19 +++++++++++++++++++
3 files changed, 23 insertions(+)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 0adc5e3..a0adf58 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -980,6 +980,9 @@ int x86_perf_event_set_period(struct perf_event *event)
if (left > x86_pmu.max_period)
left = x86_pmu.max_period;

+ if (x86_pmu.limit_period)
+ left = x86_pmu.limit_period(event, left);
+
per_cpu(pmc_prev_left[idx], smp_processor_id()) = left;

/*
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index de81627..a46e391 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -456,6 +456,7 @@ struct x86_pmu {
struct x86_pmu_quirk *quirks;
int perfctr_second_write;
bool late_ack;
+ unsigned (*limit_period)(struct perf_event *event, unsigned l);

/*
* sysfs attrs
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 4bfb0ec..66260e1 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -2034,6 +2034,24 @@ hsw_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
return c;
}

+/*
+ * Broadwell:
+ * The INST_RETIRED.ALL period always needs to have lowest
+ * 6bits cleared (BDM57). It shall not use a period smaller
+ * than 100 (BDM11). We combine the two to enforce
+ * a min-period of 128.
+ */
+static unsigned bdw_limit_period(struct perf_event *event, unsigned left)
+{
+ if ((event->hw.config & 0xffff) ==
+ X86_CONFIG(.event=0xc0, .umask=0x01)) {
+ if (left < 128)
+ left = 128;
+ left &= ~0x3fu;
+ }
+ return left;
+}
+
PMU_FORMAT_ATTR(event, "config:0-7" );
PMU_FORMAT_ATTR(umask, "config:8-15" );
PMU_FORMAT_ATTR(edge, "config:18" );
@@ -2711,6 +2729,7 @@ __init int intel_pmu_init(void)
x86_pmu.hw_config = hsw_hw_config;
x86_pmu.get_event_constraints = hsw_get_event_constraints;
x86_pmu.cpu_events = hsw_events_attrs;
+ x86_pmu.limit_period = bdw_limit_period;
pr_cont("Broadwell events, ");
break;

--
1.9.3

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