RE: [PATCH 2/5] perf/x86: add PERF_SAMPLE_SKID_IP support for X86 PEBS

Liang, Kan
2017-06-15T15:40:13Z

> This patch adds support for SKID_IP to Intel x86 processors in PEBS mode. In
> that case, the off-by-1 IP from PEBS is returned in the SKID_IP field.

It looks we can only get different skid_ip and ip with :pp event (attr.precise = 2).
With the :p event (attr.precise = 1), the skid_ip and ip are the same. Right?

Thanks,
Kan

>
> Signed-off-by: Stephane Eranian <eranian@google.com>
> ---
> arch/x86/events/intel/ds.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c index
> c6d23ffe422d..ee17de5d6b8d 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -1169,6 +1169,13 @@ static void setup_pebs_sample_data(struct
> perf_event *event,
> x86_pmu.intel_cap.pebs_format >= 1)
> data->addr = pebs->dla;
>
> + /*
> + * unmodified, skid IP which is guaranteed to be the next
> + * dyanmic instruction
> + */
> + if (sample_type & PERF_SAMPLE_SKID_IP)
> + data->skid_ip = pebs->ip;
> +
> if (x86_pmu.intel_cap.pebs_format >= 2) {
> /* Only set the TSX weight when no memory weight. */
> if ((sample_type & PERF_SAMPLE_WEIGHT) && !fll)
> --
> 2.13.1.518.g3df882009-goog