On 06/02/19 17:34, Peter Zijlstra wrote:
>
> How about we extend perf_guest_info_callback with an arch section and
> add:
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 5aeb4c74fb99..76ce804e72c1 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -5835,6 +5835,9 @@ struct perf_guest_info_callbacks *perf_guest_cbs;
>
> int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
> {
> + if (WARN_ON_ONCE(perf_guest_cbs))
> + return -EBUSY;
> +
> perf_guest_cbs = cbs;
> return 0;
> }
> @@ -5842,6 +5845,9 @@ EXPORT_SYMBOL_GPL(perf_register_guest_info_callbacks);
>
> int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks
> *cbs)
> {
> + if (WARN_ON_ONCE(perf_guest_cbs != cbs))
> + return -EINVAL;
> +
> perf_guest_cbs = NULL;
> return 0;
> }
Makes total sense.
Paolo
