Re: [PATCH v3 bpf-next 1/2] bpf: separate bpf_get_[stack|stackid] for perf events BPF

[Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>]

On Tue, Jul 21, 2020 at 3:40 PM Song Liu <songliubraving@xxxxxx> wrote:
>
> We only need to block precise_ip >= 2. precise_ip == 1 is OK.

Are you sure?
intel_pmu_hw_config() has:
if (event->attr.precise_ip) {
    if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
            event->attr.sample_type |= __PERF_SAMPLE_CALLCHAIN_EARLY;
}