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    SubjectRE: [RFC PATCH v2 1/3] perf/core: Expose perf_event_{en,dis}able_local()
    Date
    On Thursday, September 22, 2022 12:45 AM, Li, Xiaoyao wrote:
    > KVM needs them to disable/enable an Intel PT perf event before vm-entry/after
    > vm-exit.

    I would explain more in the commit here:

    Export perf_event_disable_local and perf_event_enable_local for perf users to disable
    and enable perf events on the current local CPU. One usage is in PT virtualization
    by KVM:
    - before VMEnter to guest, KVM calls perf_event_disable_local to disable the host PT event
    running on the current CPU, and this reuses the PT driver to save the related h/w states.
    - after VMExit to host, KVM calls perf_event_enable_local to resume the host PT event on
    the current CPU by having the PT driver load the previously saved states into h/w.

    >
    > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
    > ---
    > include/linux/perf_event.h | 1 +
    > kernel/events/core.c | 7 +++++++
    > 2 files changed, 8 insertions(+)
    >
    > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index
    > ee8b9ecdc03b..fc5f3952d6a2 100644
    > --- a/include/linux/perf_event.h
    > +++ b/include/linux/perf_event.h
    > @@ -1472,6 +1472,7 @@ extern int
    > perf_swevent_get_recursion_context(void);
    > extern void perf_swevent_put_recursion_context(int rctx); extern u64
    > perf_swevent_set_period(struct perf_event *event); extern void
    > perf_event_enable(struct perf_event *event);
    > +extern void perf_event_enable_local(struct perf_event *event);
    > extern void perf_event_disable(struct perf_event *event); extern void
    > perf_event_disable_local(struct perf_event *event); extern void
    > perf_event_disable_inatomic(struct perf_event *event); diff --git
    > a/kernel/events/core.c b/kernel/events/core.c index
    > 2621fd24ad26..8324bb99c6bf 100644
    > --- a/kernel/events/core.c
    > +++ b/kernel/events/core.c
    > @@ -2446,6 +2446,7 @@ void perf_event_disable_local(struct perf_event
    > *event) {
    > event_function_local(event, __perf_event_disable, NULL); }
    > +EXPORT_SYMBOL_GPL(perf_event_disable_local);
    >
    > /*
    > * Strictly speaking kernel users cannot create groups and therefore this @@
    > -2984,6 +2985,12 @@ static void _perf_event_enable(struct perf_event *event)
    > event_function_call(event, __perf_event_enable, NULL); }
    >
    > +void perf_event_enable_local(struct perf_event *event) {
    > + event_function_local(event, __perf_event_enable, NULL); }
    > +EXPORT_SYMBOL_GPL(perf_event_enable_local);
    > +
    > /*
    > * See perf_event_disable();
    > */
    > --
    > 2.27.0

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