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Subject[PATCH 04/12] perf/x86-ibs: Fix frequency profiling
Date
Fixing profiling at a fix frequency, in this case the freq value and
sample period was setup incorrectly. Since sampling periods are
adjusted we also allow periods that have lower 4 bits set.

Another fix is the setup of the hw counter: If we modify
hwc->sample_period, we also need to update hwc->last_period and
hwc->period_left.

Signed-off-by: Robert Richter <robert.richter@amd.com>
---
arch/x86/kernel/cpu/perf_event_amd_ibs.c | 18 ++++++++++++++++--
1 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
index 6f00ee3..eec3ea2 100644
--- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c
+++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
@@ -162,9 +162,16 @@ static int perf_ibs_init(struct perf_event *event)
if (config & perf_ibs->cnt_mask)
/* raw max_cnt may not be set */
return -EINVAL;
- if (hwc->sample_period & 0x0f)
- /* lower 4 bits can not be set in ibs max cnt */
+ if (!event->attr.sample_freq && hwc->sample_period & 0x0f)
+ /*
+ * lower 4 bits can not be set in ibs max cnt,
+ * but allowing it in case we adjust the
+ * sample period to set a frequency.
+ */
return -EINVAL;
+ hwc->sample_period &= ~0x0FULL;
+ if (!hwc->sample_period)
+ hwc->sample_period = 0x10;
} else {
max_cnt = config & perf_ibs->cnt_mask;
config &= ~perf_ibs->cnt_mask;
@@ -175,6 +182,13 @@ static int perf_ibs_init(struct perf_event *event)
if (!hwc->sample_period)
return -EINVAL;

+ /*
+ * If we modify hwc->sample_period, we also need to update
+ * hwc->last_period and hwc->period_left.
+ */
+ hwc->last_period = hwc->sample_period;
+ local64_set(&hwc->period_left, hwc->sample_period);
+
hwc->config_base = perf_ibs->msr;
hwc->config = config;

--
1.7.8.4



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