linux-kernel - Re: [PATCH v2 12/14] perf arm-spe: Add more sub classes for operation packet

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Date:   Tue, 20 Oct 2020 22:54:57 +0100
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>,
        Dave Martin <Dave.Martin@....com>,
        linux-kernel@...r.kernel.org, Al Grant <Al.Grant@....com>
Subject: Re: [PATCH v2 12/14] perf arm-spe: Add more sub classes for operation
 packet

On 29/09/2020 14:39, Leo Yan wrote:

Hi,

> For the operation type packet payload with load/store class, it misses
> to support these sub classes:
> 
>   - A load/store targeting the general-purpose registers;
>   - A load/store targeting unspecified registers;
>   - The ARMv8.4 nested virtualisation extension can redirect system
>     register accesses to a memory page controlled by the hypervisor.
>     The SPE profiling feature in newer implementations can tag those
>     memory accesses accordingly.
> 
> Add the bit pattern describing load/store sub classes, so that the perf
> tool can decode it properly.
> 
> Inspired by Andre Przywara, refined the commit log and code for more
> clear description.
> 
> Co-developed-by: Andre Przywara <andre.przywara@....com>
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  .../util/arm-spe-decoder/arm-spe-pkt-decoder.c    | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> 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 a848c784f4cf..57a2d5494838 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
> @@ -378,6 +378,21 @@ int arm_spe_pkt_desc(const struct arm_spe_pkt *packet, char *buf,
>  				ret = arm_spe_pkt_snprintf(&buf, &blen, " SIMD-FP");
>  				if (ret < 0)
>  					return ret;
> +			} else if ((payload & SPE_OP_PKT_LDST_SUBCLASS_MASK) ==

These three and the one above use the same mask, should this go into a
switch case? Move this block to the end, then do:
	switch (payload & SPE_OP_PKT_LDST_SUBCLASS_MASK) {
	case SPE_OP_PKT_LDST_SUBCLASS_GP_REG:
		...
	case SPE_OP_PKT_LDST_SUBCLASS_UNSPEC_REG:
		...
Maybe even assign just a string pointer inside, then have one snprintf.
Haven't checked it that *really* looks better, though.

Also those later checks are quite indented, shall those be moved to
helper functions? Again just an idea ....

Cheers,
Andre


> +					SPE_OP_PKT_LDST_SUBCLASS_GP_REG) {
> +				ret = arm_spe_pkt_snprintf(&buf, &blen, " GP-REG");
> +				if (ret < 0)
> +					return ret;
> +			} else if ((payload & SPE_OP_PKT_LDST_SUBCLASS_MASK) ==
> +					SPE_OP_PKT_LDST_SUBCLASS_UNSPEC_REG) {
> +				ret = arm_spe_pkt_snprintf(&buf, &blen, " UNSPEC-REG");
> +				if (ret < 0)
> +					return ret;
> +			} else if ((payload & SPE_OP_PKT_LDST_SUBCLASS_MASK) ==
> +					SPE_OP_PKT_LDST_SUBCLASS_NV_SYSREG) {
> +				ret = arm_spe_pkt_snprintf(&buf, &blen, " NV-SYSREG");
> +				if (ret < 0)
> +					return ret;
>  			}
>  
>  			return buf_len - blen;
>