On Wed, 2013-04-12 at 10:32:41 UTC, Anshuman Khandual wrote:
> Powerpc kernel now supports SW based branch filters for book3s systems with
> some
> specifc requirements while dealing with HW supported branch filters in order
> to
> achieve overall OR semantics prevailing in perf branch stack sampling
> framework.
> This patch adapts the BHRB branch filter configuration to meet those
> protocols.
> POWER8 PMU does support 3 branch filters (out of which two are getting used in
> perf branch stack) which are mutually exclussive and cannot be ORed with each
> other. This implies that PMU can only handle one HW based branch filter
> request
> at any point of time. For all other combinations PMU will pass it on to the
> SW.
>
> Also the combination of PERF_SAMPLE_BRANCH_ANY_CALL and
> PERF_SAMPLE_BRANCH_COND
> can now be handled in SW, hence we dont error them out anymore.
>
> diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c
> index 03c5b8d..6021349 100644
> --- a/arch/powerpc/perf/power8-pmu.c
> +++ b/arch/powerpc/perf/power8-pmu.c
> @@ -561,7 +561,56 @@ static int power8_generic_events[] = {
>
> static u64 power8_bhrb_filter_map(u64 branch_sample_type, u64 *filter_mask)
> {
> - u64 pmu_bhrb_filter = 0;
> + u64 x, tmp, pmu_bhrb_filter = 0;
> + *filter_mask = 0;
> +
> + /* No branch filter requested */
> + if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY) {
> + *filter_mask = PERF_SAMPLE_BRANCH_ANY;
> + return pmu_bhrb_filter;
> + }
> +
> + /*
> + * P8 does not support oring of PMU HW branch filters. Hence
> + * if multiple branch filters are requested which includes filters
> + * supported in PMU, still go ahead and clear the PMU based HW branch
> + * filter component as in this case all the filters will be processed
> + * in SW.
Leading space there.
> + */
> + tmp = branch_sample_type;
> +
> + /* Remove privilege filters before comparison */
> + tmp &= ~PERF_SAMPLE_BRANCH_USER;
> + tmp &= ~PERF_SAMPLE_BRANCH_KERNEL;
> + tmp &= ~PERF_SAMPLE_BRANCH_HV;
> +
> + for_each_branch_sample_type(x) {
> + /* Ignore privilege requests */
> + if ((x == PERF_SAMPLE_BRANCH_USER) || (x ==
> PERF_SAMPLE_BRANCH_KERNEL) || (x == PERF_SAMPLE_BRANCH_HV))
> + continue;
> +
> + if (!(tmp & x))
> + continue;
> +
> + /* Supported HW PMU filters */
> + if (tmp & PERF_SAMPLE_BRANCH_ANY_CALL) {
> + tmp &= ~PERF_SAMPLE_BRANCH_ANY_CALL;
> + if (tmp) {
> + pmu_bhrb_filter = 0;
> + *filter_mask = 0;
> + return pmu_bhrb_filter;
> + }
> + }
> +
> + if (tmp & PERF_SAMPLE_BRANCH_COND) {
> + tmp &= ~PERF_SAMPLE_BRANCH_COND;
> + if (tmp) {
> + pmu_bhrb_filter = 0;
> + *filter_mask = 0;
> + return pmu_bhrb_filter;
> + }
> + }
> + }
>
> /* BHRB and regular PMU events share the same privilege state
> * filter configuration. BHRB is always recorded along with a
> @@ -570,34 +619,20 @@ static u64 power8_bhrb_filter_map(u64
> branch_sample_type, u64 *filter_mask)
> * PMU event, we ignore any separate BHRB specific request.
> */
>
> - /* No branch filter requested */
> - if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY)
> - return pmu_bhrb_filter;
> -
> - /* Invalid branch filter options - HW does not support */
> - if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY_RETURN)
> - return -1;
> -
> - if (branch_sample_type & PERF_SAMPLE_BRANCH_IND_CALL)
> - return -1;
> -
> + /* Supported individual branch filters */
> if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY_CALL) {
> pmu_bhrb_filter |= POWER8_MMCRA_IFM1;
> + *filter_mask |= PERF_SAMPLE_BRANCH_ANY_CALL;
> return pmu_bhrb_filter;
> }
>
> if (branch_sample_type & PERF_SAMPLE_BRANCH_COND) {
> pmu_bhrb_filter |= POWER8_MMCRA_IFM3;
> + *filter_mask |= PERF_SAMPLE_BRANCH_COND;
> return pmu_bhrb_filter;
> }
>
> - /* PMU does not support ANY combination of HW BHRB filters */
> - if ((branch_sample_type & PERF_SAMPLE_BRANCH_ANY_CALL) &&
> - (branch_sample_type & PERF_SAMPLE_BRANCH_COND))
> - return -1;
> -
> - /* Every thing else is unsupported */
> - return -1;
> + return pmu_bhrb_filter;
> }
As I said in my comments on version 3 which you ignored:
I think it would be clearer if we actually checked for the possibilities we
allow and let everything else fall through, eg:
        /* Ignore user/kernel/hv bits */
        branch_sample_type &= ~PERF_SAMPLE_BRANCH_PLM_ALL;
        if (branch_sample_type == PERF_SAMPLE_BRANCH_ANY)
                return 0;
        if (branch_sample_type == PERF_SAMPLE_BRANCH_ANY_CALL)
                return POWER8_MMCRA_IFM1;
Â
        if (branch_sample_type == PERF_SAMPLE_BRANCH_COND)
                return POWER8_MMCRA_IFM3;
       Â
        return -1;
cheers
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