linux-kernel - Re: [PATCH v4 03/21] perf arm-spe: Refactor payload size calculation

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Message-ID: <bcca927c-bf32-e58c-a67c-e4e452daa641@arm.com>
Date:   Tue, 27 Oct 2020 14:53:49 +0000
From:   André Przywara <andre.przywara@....com>
To:     Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Wei Li <liwei391@...wei.com>,
        James Clark <james.clark@....com>, Al Grant <Al.Grant@....com>,
        Dave Martin <Dave.Martin@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 03/21] perf arm-spe: Refactor payload size calculation

On 27/10/2020 03:08, Leo Yan wrote:
> This patch defines macro to extract "sz" field from header, and renames
> the function payloadlen() to arm_spe_payload_len().
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>

Reviewed-by: Andre Przywara <andre.przywara@....com>

Cheers,
Andre

> ---
>  .../util/arm-spe-decoder/arm-spe-pkt-decoder.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> index 7c7b5eb09fba..06b3eec4494e 100644
> --- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> +++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> @@ -69,22 +69,22 @@ const char *arm_spe_pkt_name(enum arm_spe_pkt_type type)
>  	return arm_spe_packet_name[type];
>  }
>  
> -/* return ARM SPE payload size from its encoding,
> - * which is in bits 5:4 of the byte.
> - * 00 : byte
> - * 01 : halfword (2)
> - * 10 : word (4)
> - * 11 : doubleword (8)
> +/*
> + * Extracts the field "sz" from header bits and converts to bytes:
> + *   00 : byte (1)
> + *   01 : halfword (2)
> + *   10 : word (4)
> + *   11 : doubleword (8)
>   */
> -static int payloadlen(unsigned char byte)
> +static unsigned int arm_spe_payload_len(unsigned char hdr)
>  {
> -	return 1 << ((byte & 0x30) >> 4);
> +	return 1U << ((hdr & GENMASK_ULL(5, 4)) >> 4);
>  }
>  
>  static int arm_spe_get_payload(const unsigned char *buf, size_t len,
>  			       struct arm_spe_pkt *packet)
>  {
> -	size_t payload_len = payloadlen(buf[0]);
> +	size_t payload_len = arm_spe_payload_len(buf[0]);
>  
>  	if (len < 1 + payload_len)
>  		return ARM_SPE_NEED_MORE_BYTES;
>