Re: [PATCH v4 2/2] powerpc/papr_scm: Add support for fetching nvdimm 'fuel-gauge' metric

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

Vaibhav Jain <vaibhav@linux.ibm.com> writes:

> We add support for reporting 'fuel-gauge' NVDIMM metric via
> PAPR_PDSM_HEALTH pdsm payload. 'fuel-gauge' metric indicates the usage
> life remaining of a papr-scm compatible NVDIMM. PHYP exposes this
> metric via the H_SCM_PERFORMANCE_STATS.
>
> The metric value is returned from the pdsm by extending the return
> payload 'struct nd_papr_pdsm_health' without breaking the ABI. A new
> field 'dimm_fuel_gauge' to hold the metric value is introduced at the
> end of the payload struct and its presence is indicated by by
> extension flag PDSM_DIMM_HEALTH_RUN_GAUGE_VALID.
>
> The patch introduces a new function papr_pdsm_fuel_gauge() that is
> called from papr_pdsm_health(). If fetching NVDIMM performance stats
> is supported then 'papr_pdsm_fuel_gauge()' allocated an output buffer
> large enough to hold the performance stat and passes it to
> drc_pmem_query_stats() that issues the HCALL to PHYP. The return value
> of the stat is then populated in the 'struct
> nd_papr_pdsm_health.dimm_fuel_gauge' field with extension flag
> 'PDSM_DIMM_HEALTH_RUN_GAUGE_VALID' set in 'struct
> nd_papr_pdsm_health.extension_flags'
>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>

> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> ---
> Changelog:
>
> v4:
> * Moved a hunk from this patch to previous patch in the series.
>   [ Aneesh ]
>
> v3:
> * Updated papr_pdsm_fuel_guage() to use the updated
>   drc_pmem_query_stats() function.
>
> Resend:
> None
>
> v2:
> * Restructure code in papr_pdsm_fuel_gauge() to handle error case
> first [ Ira ]
> * Ignore the return value of papr_pdsm_fuel_gauge() in
> papr_psdm_health() [ Ira ]
> ---
>  arch/powerpc/include/uapi/asm/papr_pdsm.h |  9 +++++
>  arch/powerpc/platforms/pseries/papr_scm.c | 49 +++++++++++++++++++++++
>  2 files changed, 58 insertions(+)
>
> diff --git a/arch/powerpc/include/uapi/asm/papr_pdsm.h b/arch/powerpc/include/uapi/asm/papr_pdsm.h
> index 9ccecc1d6840..50ef95e2f5b1 100644
> --- a/arch/powerpc/include/uapi/asm/papr_pdsm.h
> +++ b/arch/powerpc/include/uapi/asm/papr_pdsm.h
> @@ -72,6 +72,11 @@
>  #define PAPR_PDSM_DIMM_CRITICAL      2
>  #define PAPR_PDSM_DIMM_FATAL         3
>  
> +/* struct nd_papr_pdsm_health.extension_flags field flags */
> +
> +/* Indicate that the 'dimm_fuel_gauge' field is valid */
> +#define PDSM_DIMM_HEALTH_RUN_GAUGE_VALID 1
> +
>  /*
>   * Struct exchanged between kernel & ndctl in for PAPR_PDSM_HEALTH
>   * Various flags indicate the health status of the dimm.
> @@ -84,6 +89,7 @@
>   * dimm_locked		: Contents of the dimm cant be modified until CEC reboot
>   * dimm_encrypted	: Contents of dimm are encrypted.
>   * dimm_health		: Dimm health indicator. One of PAPR_PDSM_DIMM_XXXX
> + * dimm_fuel_gauge	: Life remaining of DIMM as a percentage from 0-100
>   */
>  struct nd_papr_pdsm_health {
>  	union {
> @@ -96,6 +102,9 @@ struct nd_papr_pdsm_health {
>  			__u8 dimm_locked;
>  			__u8 dimm_encrypted;
>  			__u16 dimm_health;
> +
> +			/* Extension flag PDSM_DIMM_HEALTH_RUN_GAUGE_VALID */
> +			__u16 dimm_fuel_gauge;
>  		};
>  		__u8 buf[ND_PDSM_PAYLOAD_MAX_SIZE];
>  	};
> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
> index f37f3f70007d..f439f0dfea7d 100644
> --- a/arch/powerpc/platforms/pseries/papr_scm.c
> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
> @@ -518,6 +518,51 @@ static int is_cmd_valid(struct nvdimm *nvdimm, unsigned int cmd, void *buf,
>  	return 0;
>  }
>  
> +static int papr_pdsm_fuel_gauge(struct papr_scm_priv *p,
> +				union nd_pdsm_payload *payload)
> +{
> +	int rc, size;
> +	u64 statval;
> +	struct papr_scm_perf_stat *stat;
> +	struct papr_scm_perf_stats *stats;
> +
> +	/* Silently fail if fetching performance metrics isn't  supported */
> +	if (!p->stat_buffer_len)
> +		return 0;
> +
> +	/* Allocate request buffer enough to hold single performance stat */
> +	size = sizeof(struct papr_scm_perf_stats) +
> +		sizeof(struct papr_scm_perf_stat);
> +
> +	stats = kzalloc(size, GFP_KERNEL);
> +	if (!stats)
> +		return -ENOMEM;
> +
> +	stat = &stats->scm_statistic[0];
> +	memcpy(&stat->stat_id, "MemLife ", sizeof(stat->stat_id));
> +	stat->stat_val = 0;
> +
> +	/* Fetch the fuel gauge and populate it in payload */
> +	rc = drc_pmem_query_stats(p, stats, 1);
> +	if (rc < 0) {
> +		dev_dbg(&p->pdev->dev, "Err(%d) fetching fuel gauge\n", rc);
> +		goto free_stats;
> +	}
> +
> +	statval = be64_to_cpu(stat->stat_val);
> +	dev_dbg(&p->pdev->dev,
> +		"Fetched fuel-gauge %llu", statval);
> +	payload->health.extension_flags |=
> +		PDSM_DIMM_HEALTH_RUN_GAUGE_VALID;
> +	payload->health.dimm_fuel_gauge = statval;
> +
> +	rc = sizeof(struct nd_papr_pdsm_health);
> +
> +free_stats:
> +	kfree(stats);
> +	return rc;
> +}
> +
>  /* Fetch the DIMM health info and populate it in provided package. */
>  static int papr_pdsm_health(struct papr_scm_priv *p,
>  			    union nd_pdsm_payload *payload)
> @@ -558,6 +603,10 @@ static int papr_pdsm_health(struct papr_scm_priv *p,
>  
>  	/* struct populated hence can release the mutex now */
>  	mutex_unlock(&p->health_mutex);
> +
> +	/* Populate the fuel gauge meter in the payload */
> +	papr_pdsm_fuel_gauge(p, payload);
> +
>  	rc = sizeof(struct nd_papr_pdsm_health);
>  
>  out:
> -- 
> 2.26.2
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