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SubjectRe: [PATCH] Revert "perf tools: Fix PMU term format max value calculation"
ping

thanks,
jirka

On Wed, Oct 03, 2018 at 09:20:46AM +0200, Jiri Olsa wrote:
> This reverts commit ac0e2cd555373ae6f8f3a3ad3fbbf5b6d1e7aaaa.
>
> Michael reported an issue with oversized terms values assignment
> and I noticed there was actually a misunderstanding of the max
> value check in the past.
>
> The above commit's changelog says:
>
> If bit 21 is set, there is parsing issues as below.
>
> $ perf stat -a -e uncore_qpi_0/event=0x200002,umask=0x8/
> event syntax error: '..pi_0/event=0x200002,umask=0x8/'
> \___ value too big for format, maximum is 511
>
> But there's no issue there, because the event value is distributed
> along the value defined by the format. Even if the format defines
> separated bit, the value is treated as a continual number, which
> should follow the format definition.
>
> In above case it's 9-bit value with last bit separated:
> $ cat uncore_qpi_0/format/event
> config:0-7,21
>
> Hence the value 0x200002 is correctly reported as format violation,
> because it exceeds 9 bits. It should have been 0x102 instead, which
> sets the 9th bit - the bit 21 of the format.
>
> $ perf stat -vv -a -e uncore_qpi_0/event=0x102,umask=0x8/
> Using CPUID GenuineIntel-6-2D
> ...
> ------------------------------------------------------------
> perf_event_attr:
> type 10
> size 112
> config 0x200802
> sample_type IDENTIFIER
> ...
>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Kan Liang <kan.liang@intel.com>
> Reported-by: Michael Petlan <mpetlan@redhat.com>
> Link: http://lkml.kernel.org/n/tip-icxq7a1r66lusm3ahaimekis@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> tools/perf/util/pmu.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index afd68524ffa9..7799788f662f 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -930,13 +930,14 @@ static void pmu_format_value(unsigned long *format, __u64 value, __u64 *v,
>
> static __u64 pmu_format_max_value(const unsigned long *format)
> {
> - __u64 w = 0;
> - int fbit;
> -
> - for_each_set_bit(fbit, format, PERF_PMU_FORMAT_BITS)
> - w |= (1ULL << fbit);
> + int w;
>
> - return w;
> + w = bitmap_weight(format, PERF_PMU_FORMAT_BITS);
> + if (!w)
> + return 0;
> + if (w < 64)
> + return (1ULL << w) - 1;
> + return -1;
> }
>
> /*
> --
> 2.17.1
>

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