Anshuman Khandual <khand...@linux.vnet.ibm.com> wrote:
> Completely ignore BHRB privilege state filter request as we are
> already configuring that with privilege state filtering attribute
> for the accompanying PMU event. This would help achieve cleaner
> user space interaction for BHRB.
>
> This patch fixes a situation like this
>
> Before patch:-
> ------------
> ./perf record -j any -e branch-misses:k ls
> Error:
> The sys_perf_event_open() syscall returned with 95 (Operation not
> supported) for event (branch-misses:k).
> /bin/dmesg may provide additional information.
> No CONFIG_PERF_EVENTS=y kernel support configured?
>
> Here 'perf record' actually copies over ':k' filter request into BHRB
> privilege state filter config and our previous check in kernel would
> fail that.
>
> After patch:-
> -------------
> ./perf record -j any -e branch-misses:k ls
> perf perf.data perf.data.old test-mmap-ring
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.002 MB perf.data (~102 samples)]
>
> Signed-off-by: Anshuman Khandual <khand...@linux.vnet.ibm.com>
Acked-by: Michael Neuling <mi...@neuling.org>
> ---
> arch/powerpc/perf/power8-pmu.c | 13 ++++---------
> 1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c
> index f7d1c4f..371c6e7 100644
> --- a/arch/powerpc/perf/power8-pmu.c
> +++ b/arch/powerpc/perf/power8-pmu.c
> @@ -523,18 +523,13 @@ static int power8_generic_events[] = {
> static u64 power8_bhrb_filter_map(u64 branch_sample_type)
> {
> u64 pmu_bhrb_filter = 0;
> - u64 br_privilege = branch_sample_type & ONLY_PLM;
>
> - /* BHRB and regular PMU events share the same prvillege state
> + /* BHRB and regular PMU events share the same privilege state
> * filter configuration. BHRB is always recorded along with a
> - * regular PMU event. So privilege state filter criteria for BHRB
> - * and the companion PMU events has to be the same. As a default
> - * "perf record" tool sets all privillege bits ON when no filter
> - * criteria is provided in the command line. So as along as all
> - * privillege bits are ON or they are OFF, we are good to go.
> + * regular PMU event. As the privilege state filter is handled
> + * in the basic PMC configuration of the accompanying regular
> + * PMU event, we ignore any separate BHRB specific request.
> */
> - if ((br_privilege != 7) && (br_privilege != 0))
> - return -1;
>
> /* No branch filter requested */
> if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY)
> --
> 1.7.11.7
>
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