linux-kernel - [PATCH] perf/core: Reset remaining bits in perf_clear_branch_entry

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Date:   Thu,  1 Dec 2022 11:21:03 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-kernel@...r.kernel.org
Cc:     james.clark@....com, Anshuman Khandual <anshuman.khandual@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org
Subject: [PATCH] perf/core: Reset remaining bits in perf_clear_branch_entry_bitfields()

perf_clear_branch_entry_bitfields() resets all struct perf_branch_entry bit
fields before capturing branch records. This resets remaining bit fields
except 'new_type', which is valid only when 'type' is PERF_BR_EXTEND_ABI.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: linux-perf-users@...r.kernel.org>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
This applies on v6.1-rc6

'perf_branch_entry.new_type' can remain uninitialized as explained earlier.
Also there is no PERF_BR_NEW_UNKNOWN to spare, because 'perf_branch_entry.
new_type' enumeration starts at PERF_BR_NEW_FAULT_ALGN, to save a position
for the extended branch types instead.

 include/linux/perf_event.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 0031f7b4d9ab..c97b5f6f77a4 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1110,8 +1110,9 @@ static inline void perf_clear_branch_entry_bitfields(struct perf_branch_entry *b
 	br->in_tx = 0;
 	br->abort = 0;
 	br->cycles = 0;
-	br->type = 0;
+	br->type = PERF_BR_UNKNOWN;
 	br->spec = PERF_BR_SPEC_NA;
+	br->priv = PERF_BR_PRIV_UNKNOWN;
 	br->reserved = 0;
 }
 
-- 
2.25.1