[PATCH 4.18 045/350] Revert "perf tools: Fix PMU term format max value calculation"

Greg Kroah-Hartman
2018-11-11T23:41:42Z

From: Jiri Olsa <jolsa@kernel.org>

[ Upstream commit 1b9caa10b31dda0866f4028e4bfb923fb6e4072f ]

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
...

Reported-by: Michael Petlan <mpetlan@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: ac0e2cd55537 ("perf tools: Fix PMU term format max value calculation")
Link: http://lkml.kernel.org/r/20181003072046.29276-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/perf/util/pmu.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -936,13 +936,14 @@ static void pmu_format_value(unsigned lo

static __u64 pmu_format_max_value(const unsigned long *format)
{
- __u64 w = 0;
- int fbit;
+ int w;

- for_each_set_bit(fbit, format, PERF_PMU_FORMAT_BITS)
- w |= (1ULL << fbit);
-
- return w;
+ w = bitmap_weight(format, PERF_PMU_FORMAT_BITS);
+ if (!w)
+ return 0;
+ if (w < 64)
+ return (1ULL << w) - 1;
+ return -1;
}

/*