Re: [PATCH bpf,perf]] bpf,perf: return EOPNOTSUPP for attaching bpf handler on PERF_COUNT_SW_DUMMY

[Alexei Starovoitov]

On Sat, Nov 14, 2020 at 5:53 AM Florian Lehner <dev@xxxxxxxxxxx> wrote:
>
> At the moment it is not possible to attach a bpf handler to a perf event
> of type PERF_TYPE_SOFTWARE with a configuration of PERF_COUNT_SW_DUMMY.

It is possible or it is not possible?

Such "commit log as an abstract statement" patches are a mystery to a reader.
Please explain what problem you're trying to solve and how it's being addressed.

> Signed-off-by: Florian Lehner <dev@xxxxxxxxxxx>
> ---
>  kernel/events/core.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index da467e1dd49a..4e8846b7ceda 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -9668,6 +9668,10 @@ static int perf_event_set_bpf_handler(struct perf_event *event, u32 prog_fd)
>         if (event->prog)
>                 return -EEXIST;
>
> +       if (event->attr.type == PERF_TYPE_SOFTWARE &&
> +           event->attr.config == PERF_COUNT_SW_DUMMY)
> +               return -EOPNOTSUPP;

Is it a fix or a feature?
If it is a fix please add 'Fixes:' tag.