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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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