Re: [PATCH v3 4/5] perf arm-spe: Support metadata version 2

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

On 28/09/2024 8:55 pm, Leo Yan wrote:
> This commit is to support metadata version 2 and at the meantime it is
> backward compatible for version 1's format.
> 
> The metadata version 1 doesn't include the ARM_SPE_HEADER_VERSION field.
> As version 1 is fixed with two u64 fields, by checking the metadata
> size, it distinguishes the metadata is version 1 or version 2 (and any
> new versions if later will have). For version 2, it reads out CPU number
> and retrieves the metadata info for every CPU.
> 
> Signed-off-by: Leo Yan <leo.yan@arm.com>
> ---
>   tools/perf/util/arm-spe.c | 95 +++++++++++++++++++++++++++++++++++++--
>   1 file changed, 92 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
> index 70989b1bae47..52cee7401ff4 100644
> --- a/tools/perf/util/arm-spe.c
> +++ b/tools/perf/util/arm-spe.c
> @@ -78,6 +78,10 @@ struct arm_spe {
>   
>   	unsigned long			num_events;
>   	u8				use_ctx_pkt_for_pid;
> +
> +	u64				**metadata;
> +	u64				metadata_ver;
> +	u64				metadata_nr_cpu;
>   };
>   
>   struct arm_spe_queue {
> @@ -1016,6 +1020,73 @@ static int arm_spe_flush(struct perf_session *session __maybe_unused,
>   	return 0;
>   }
>   
> +static u64 *arm_spe__alloc_per_cpu_metadata(u64 *buf, int per_cpu_size)
> +{
> +	u64 *metadata;
> +
> +	metadata = zalloc(per_cpu_size);
> +	if (!metadata)
> +		return NULL;
> +
> +	memcpy(metadata, buf, per_cpu_size);
> +	return metadata;
> +}
> +
> +static void arm_spe__free_metadata(u64 **metadata, int nr_cpu)
> +{
> +	int i;
> +
> +	for (i = 0; i < nr_cpu; i++)
> +		zfree(&metadata[i]);
> +	free(metadata);
> +}
> +
> +static u64 **arm_spe__alloc_metadata(struct perf_record_auxtrace_info *info,
> +				     u64 *ver, int *nr_cpu)
> +{
> +	u64 *ptr = (u64 *)info->priv;
> +	u64 metadata_size;
> +	u64 **metadata = NULL;
> +	int hdr_sz, per_cpu_sz, i;
> +
> +	metadata_size = info->header.size -
> +		sizeof(struct perf_record_auxtrace_info);
> +
> +	/* Metadata version 1 */
> +	if (metadata_size == ARM_SPE_AUXTRACE_V1_PRIV_SIZE) {
> +		*ver = 1;
> +		*nr_cpu = 0;
> +		/* No per CPU metadata */
> +		return NULL;
> +	}
> +
> +	*ver = ptr[ARM_SPE_HEADER_VERSION];
> +	hdr_sz = ptr[ARM_SPE_HEADER_SIZE];
> +	*nr_cpu = ptr[ARM_SPE_CPUS_NUM];
> +
> +	metadata = calloc(*nr_cpu, sizeof(*metadata));
> +	if (!metadata)
> +		return NULL;
> +
> +	/* Locate the start address of per CPU metadata */
> +	ptr += hdr_sz;
> +	per_cpu_sz = (metadata_size - (hdr_sz * sizeof(u64))) / (*nr_cpu);
> +
> +	for (i = 0; i < *nr_cpu; i++) {
> +		metadata[i] = arm_spe__alloc_per_cpu_metadata(ptr, per_cpu_sz);
> +		if (!metadata[i])
> +			goto err_per_cpu_metadata;
> +
> +		ptr += per_cpu_sz / sizeof(u64);
> +	}
> +
> +	return metadata;
> +
> +err_per_cpu_metadata:
> +	arm_spe__free_metadata(metadata, *nr_cpu);
> +	return NULL;
> +}
> +
>   static void arm_spe_free_queue(void *priv)
>   {
>   	struct arm_spe_queue *speq = priv;
> @@ -1050,6 +1121,7 @@ static void arm_spe_free(struct perf_session *session)
>   	auxtrace_heap__free(&spe->heap);
>   	arm_spe_free_events(session);
>   	session->auxtrace = NULL;
> +	arm_spe__free_metadata(spe->metadata, spe->metadata_nr_cpu);
>   	free(spe);
>   }
>   
> @@ -1267,15 +1339,24 @@ int arm_spe_process_auxtrace_info(union perf_event *event,
>   	const char *cpuid = perf_env__cpuid(session->evlist->env);
>   	u64 midr = strtol(cpuid, NULL, 16);
>   	struct arm_spe *spe;
> -	int err;
> +	u64 **metadata = NULL;
> +	u64 metadata_ver;
> +	int nr_cpu, err;
>   
>   	if (auxtrace_info->header.size < sizeof(struct perf_record_auxtrace_info) +
>   					min_sz)
>   		return -EINVAL;
>   
> +	metadata = arm_spe__alloc_metadata(auxtrace_info, &metadata_ver,
> +					   &nr_cpu);
> +	if (!metadata && metadata_ver != 1) {
> +		pr_err("Failed to parse Arm SPE metadata.\n");
> +		return -EINVAL;
> +	}
> +
>   	spe = zalloc(sizeof(struct arm_spe));
>   	if (!spe)
> -		return -ENOMEM;
> +		goto err_free_metadata;
>   

Hi Leo,

There's a build error here:

util/arm-spe.c:1402:6: error: variable 'err' is used uninitialized 
whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
         if (!spe)
             ^~~~


>   	err = auxtrace_queues__init(&spe->queues);
>   	if (err)
> @@ -1284,8 +1365,14 @@ int arm_spe_process_auxtrace_info(union perf_event *event,
>   	spe->session = session;
>   	spe->machine = &session->machines.host; /* No kvm support */
>   	spe->auxtrace_type = auxtrace_info->type;
> -	spe->pmu_type = auxtrace_info->priv[ARM_SPE_PMU_TYPE];
> +	if (metadata_ver == 1)
> +		spe->pmu_type = auxtrace_info->priv[ARM_SPE_PMU_TYPE];
> +	else
> +		spe->pmu_type = auxtrace_info->priv[ARM_SPE_SHARED_PMU_TYPE];

I thought V2 saved the type per-CPU, so I wasn't that clear on the 
SHARED_PMU_TYPE vs ARM_SPE_PMU_TYPE use here. Maybe it's just a naming 
issue? If it's a placeholder value to generate events can it be the same 
name as the V1 enum, that way it's clearer that it's the same thing.

Like: ARM_SPE_PMU_TYPE_V2


Other than that, for the whole set:

Reviewed-by: James Clark <james.clark@linaro.org>