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    Subject[PATCH v2 03/20] perf/core: add PERF_PMU_CAP_EXCLUDE for exclusion capable PMUs
    Date
    Many PMU drivers do not have the capability to exclude counting events
    that occur in specific contexts such as idle, kernel, guest, etc. These
    drivers indicate this by returning an error in their event_init upon
    testing the events attribute flags. This approach is error prone and
    often inconsistent.

    Let's instead allow PMU drivers to advertise their ability to exclude
    based on context via a new capability: PERF_PMU_CAP_EXCLUDE. This
    allows the perf core to reject requests for exclusion events where
    there is no support in the PMU.

    Signed-off-by: Andrew Murray <andrew.murray@arm.com>
    ---
    include/linux/perf_event.h | 1 +
    kernel/events/core.c | 9 +++++++++
    2 files changed, 10 insertions(+)

    diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
    index b2e806f..69b3d65 100644
    --- a/include/linux/perf_event.h
    +++ b/include/linux/perf_event.h
    @@ -244,6 +244,7 @@ struct perf_event;
    #define PERF_PMU_CAP_EXCLUSIVE 0x10
    #define PERF_PMU_CAP_ITRACE 0x20
    #define PERF_PMU_CAP_HETEROGENEOUS_CPUS 0x40
    +#define PERF_PMU_CAP_EXCLUDE 0x80

    /**
    * struct pmu - generic performance monitoring unit
    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index 5a97f34..9afb33c 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -9743,6 +9743,15 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
    if (ctx)
    perf_event_ctx_unlock(event->group_leader, ctx);

    + if (!ret) {
    + if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUDE) &&
    + event_has_any_exclude_flag(event)) {
    + if (event->destroy)
    + event->destroy(event);
    + ret = -EINVAL;
    + }
    + }
    +
    if (ret)
    module_put(pmu->module);

    --
    2.7.4
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