Re: [PATCH v2 2/2] perf arm-spe: Add support for SPE Data Source packet on AmpereOne

[James Clark <james.clark@linaro.org>]

On 31/10/2024 9:35 pm, Ilkka Koskinen wrote:
> Decode SPE Data Source packets on AmpereOne. The field is IMPDEF.
> 
> Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
> ---
>   .../util/arm-spe-decoder/arm-spe-decoder.h    |  9 +++
>   tools/perf/util/arm-spe.c                     | 65 +++++++++++++++++++
>   2 files changed, 74 insertions(+)
> 
> diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.h b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.h
> index 358c611eeddb..4bcd627e859f 100644
> --- a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.h
> +++ b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.h
> @@ -67,6 +67,15 @@ enum arm_spe_common_data_source {
>   	ARM_SPE_COMMON_DS_DRAM		= 0xe,
>   };
>   
> +enum arm_spe_ampereone_data_source {
> +	ARM_SPE_AMPEREONE_LOCAL_CHIP_CACHE_OR_DEVICE    = 0x0,
> +	ARM_SPE_AMPEREONE_SLC                           = 0x3,
> +	ARM_SPE_AMPEREONE_REMOTE_CHIP_CACHE             = 0x5,
> +	ARM_SPE_AMPEREONE_DDR                           = 0x7,
> +	ARM_SPE_AMPEREONE_L1D                           = 0x8,
> +	ARM_SPE_AMPEREONE_L2D                           = 0x9,
> +};
> +
>   struct arm_spe_record {
>   	enum arm_spe_sample_type type;
>   	int err;
> diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
> index 9586416be30a..700d4bc8d8ec 100644
> --- a/tools/perf/util/arm-spe.c
> +++ b/tools/perf/util/arm-spe.c
> @@ -103,6 +103,30 @@ struct arm_spe_queue {
>   	u32				flags;
>   };
>   
> +struct arm_spe_source_mapping {
> +	u16 source;
> +	enum arm_spe_common_data_source common_src;
> +};
> +
> +#define MAP_SOURCE(src, common)				\
> +	{						\
> +		.source = ARM_SPE_##src,		\
> +		.common_src = ARM_SPE_COMMON_##common,  \
> +	}
> +
> +static int arm_spe__map_to_common_source(u16 source,
> +					 struct arm_spe_source_mapping *tbl,
> +					 int nr_sources)
> +{
> +	while (nr_sources--) {
> +		if (tbl->source == source)
> +			return tbl->common_src;
> +		tbl++;
> +	}
> +

Hi Ilkka,

I think a simple switch statement here would be easier to follow than 
the loop, custom macro and then having the mappings in some other place:

switch(source)
case 0x0: /* AMPEREONE_LOCAL_CHIP_CACHE_OR_DEVICE */
   return DS_PEER_CORE;

etc...

> +	return -1;

And the default case can return 0xfff directly, which avoids the if else 
later only to convert this -1 back into 0xfff.

> +}
> +
>   static void arm_spe_dump(struct arm_spe *spe __maybe_unused,
>   			 unsigned char *buf, size_t len)
>   {
> @@ -443,6 +467,11 @@ static const struct midr_range common_ds_encoding_cpus[] = {
>   	{},
>   };
>   
> +static const struct midr_range ampereone_ds_encoding_cpus[] = {
> +	MIDR_ALL_VERSIONS(MIDR_AMPERE1A),
> +	{},
> +};
> +
>   static void arm_spe__sample_flags(struct arm_spe_queue *speq)
>   {
>   	const struct arm_spe_record *record = &speq->decoder->record;
> @@ -532,6 +561,38 @@ static void arm_spe__synth_data_source_common(const struct arm_spe_record *recor
>   	}
>   }
>   
> +static struct arm_spe_source_mapping ampereone_sources[] = {
> +	MAP_SOURCE(AMPEREONE_LOCAL_CHIP_CACHE_OR_DEVICE, DS_PEER_CORE),
> +	MAP_SOURCE(AMPEREONE_SLC, DS_SYS_CACHE),
> +	MAP_SOURCE(AMPEREONE_REMOTE_CHIP_CACHE, DS_REMOTE),
> +	MAP_SOURCE(AMPEREONE_DDR, DS_DRAM),
> +	MAP_SOURCE(AMPEREONE_L1D, DS_L1D),
> +	MAP_SOURCE(AMPEREONE_L2D, DS_L2),
> +};
> +
> +/*
> + * Source is IMPDEF. Here we convert the source code used on AmpereOne cores
> + * to the common (Neoverse, Cortex) to avoid duplicating the decoding code.
> + */
> +static void arm_spe__synth_data_source_ampereone(const struct arm_spe_record *record,
> +						 union perf_mem_data_src *data_src)
> +{
> +	int common_src;
> +	struct arm_spe_record common_record;
> +
> +	common_src = arm_spe__map_to_common_source(record->source,
> +						   ampereone_sources,
> +						   ARRAY_SIZE(ampereone_sources));
> +	if (common_src < 0)
> +		 /* Assign a bogus value that's not used for common coding */
> +		common_record.source = 0xfff;
> +	else
> +		common_record.source = common_src;
> +
> +	common_record.op = record->op;
> +	arm_spe__synth_data_source_common(&common_record, data_src);
> +}
> +
>   static void arm_spe__synth_memory_level(const struct arm_spe_record *record,
>   					union perf_mem_data_src *data_src)
>   {
> @@ -606,6 +667,8 @@ static u64 arm_spe__synth_data_source(struct arm_spe_queue *speq,
>   	union perf_mem_data_src	data_src = { .mem_op = PERF_MEM_OP_NA };
>   	bool is_common = arm_spe__is_ds_encoding_supported(speq,
>   						common_ds_encoding_cpus);
> +	bool is_ampereone = arm_spe__is_ds_encoding_supported(speq,
> +						ampereone_ds_encoding_cpus);

I know this probably already works, but we don't really need is_common 
is_ampere etc, it will only grow anyway. All we need is a list of midrs 
and function pairs. That also avoids doing is_ampereone even after we 
already know is_common == true.

static const struct data_src[] = {
...
	DS(MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V2), common_ds),
	DS(MIDR_ALL_VERSIONS(MIDR_AMPERE1A), ampere_ds),
	{},
...
};

"arm_spe__is_ds_encoding_supported" then becomes a direct call to 
"arm_spe__synth_ds" and we can drop the is_ampereone and is_common vars. 
Then adding new ones doesn't require changing the function anymore.

>   
>   	if (record->op & ARM_SPE_OP_LD)
>   		data_src.mem_op = PERF_MEM_OP_LOAD;
> @@ -616,6 +679,8 @@ static u64 arm_spe__synth_data_source(struct arm_spe_queue *speq,
>   
>   	if (is_common)
>   		arm_spe__synth_data_source_common(record, &data_src);
> +	else if (is_ampereone)
> +		arm_spe__synth_data_source_ampereone(record, &data_src);
>   	else
>   		arm_spe__synth_memory_level(record, &data_src);
>