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Message-ID: <64f7f939-0c71-e5de-9812-fd46bfdd89a8@arm.com>
Date:   Mon, 5 Dec 2022 09:11:18 +0530
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Subject: Re: [PATCH] perf/core: Reset remaining bits in
 perf_clear_branch_entry_bitfields()
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To:     linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>
Cc:     james.clark@arm.com, Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        linux-perf-users@vger.kernel.org
References: <20221201055103.302019-1-anshuman.khandual@arm.com>
From:   Anshuman Khandual <anshuman.khandual@arm.com>
In-Reply-To: <20221201055103.302019-1-anshuman.khandual@arm.com>
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On 12/1/22 11:21, Anshuman Khandual wrote:
> 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@infradead.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: linux-perf-users@vger.kernel.org>
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.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;
>  }
>  

Hello Peter,

Just wondering is there a chance that this patch could make it to v6.2-rc1 ?

- Anshuman