[PATCH] powerpc/papr_scm: Add support for reporting dirty-shutdown-count

[Vaibhav Jain]

Thanks for catching this Santosh. Have fixed this in v2 version of this
patch

-- 
Cheers
~ Vaibhav


Santosh Sivaraj <santosh at fossix.org> writes:

> Hi Vaibhav,
>
> Vaibhav Jain <vaibhav at linux.ibm.com> writes:
>
>> Persistent memory devices like NVDIMMs can loose cached writes in case
>> something prevents flush on power-fail. Such situations are termed as
>> dirty shutdown and are exposed to applications as
>> last-shutdown-state (LSS) flag and a dirty-shutdown-counter(DSC) as
>> described at [1]. The latter being useful in conditions where multiple
>> applications want to detect a dirty shutdown event without racing with
>> one another.
>>
>> PAPR-NVDIMMs have so far only exposed LSS style flags to indicate a
>> dirty-shutdown-state. This patch further adds support for DSC via the
>> "ibm,persistence-failed-count" device tree property of an NVDIMM. This
>> property is a monotonic increasing 64-bit counter thats an indication
>> of number of times an NVDIMM has encountered a dirty-shutdown event
>> causing persistence loss.
>>
>> Since this value is not expected to change after system-boot hence
>> papr_scm reads & caches its value during NVDIMM probe and exposes it
>> as a PAPR sysfs attributed named 'dirty_shutdown' to match the name of
>> similarly named NFIT sysfs attribute. Also this value is available to
>> libnvdimm via PAPR_PDSM_HEALTH payload. 'struct nd_papr_pdsm_health'
>> has been extended to add a new member called 'dimm_dsc' presence of
>> which is indicated by the newly introduced PDSM_DIMM_DSC_VALID flag.
>>
>> References:
>> [1] https://pmem.io/documents/Dirty_Shutdown_Handling-V1.0.pdf
>>
>> Signed-off-by: Vaibhav Jain <vaibhav at linux.ibm.com>
>> ---
>>  arch/powerpc/include/uapi/asm/papr_pdsm.h |  6 +++++
>>  arch/powerpc/platforms/pseries/papr_scm.c | 30 +++++++++++++++++++++++
>>  2 files changed, 36 insertions(+)
>>
>> diff --git a/arch/powerpc/include/uapi/asm/papr_pdsm.h b/arch/powerpc/include/uapi/asm/papr_pdsm.h
>> index 50ef95e2f5b1..82488b1e7276 100644
>> --- a/arch/powerpc/include/uapi/asm/papr_pdsm.h
>> +++ b/arch/powerpc/include/uapi/asm/papr_pdsm.h
>> @@ -77,6 +77,9 @@
>>  /* Indicate that the 'dimm_fuel_gauge' field is valid */
>>  #define PDSM_DIMM_HEALTH_RUN_GAUGE_VALID 1
>>  
>> +/* Indicate that the 'dimm_dsc' field is valid */
>> +#define PDSM_DIMM_DSC_VALID 2
>> +
>>  /*
>>   * Struct exchanged between kernel & ndctl in for PAPR_PDSM_HEALTH
>>   * Various flags indicate the health status of the dimm.
>> @@ -105,6 +108,9 @@ struct nd_papr_pdsm_health {
>>  
>>  			/* Extension flag PDSM_DIMM_HEALTH_RUN_GAUGE_VALID */
>>  			__u16 dimm_fuel_gauge;
>> +
>> +			/* Extension flag PDSM_DIMM_DSC_VALID */
>> +			__u64 dimm_dsc;
>>  		};
>>  		__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 11e7b90a3360..68f0d3d5e899 100644
>> --- a/arch/powerpc/platforms/pseries/papr_scm.c
>> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
>> @@ -114,6 +114,9 @@ struct papr_scm_priv {
>>  	/* Health information for the dimm */
>>  	u64 health_bitmap;
>>  
>> +	/* Holds the last known dirty shutdown counter value */
>> +	u64 dirty_shutdown_counter;
>> +
>>  	/* length of the stat buffer as expected by phyp */
>>  	size_t stat_buffer_len;
>>  };
>> @@ -603,6 +606,16 @@ static int papr_pdsm_fuel_gauge(struct papr_scm_priv *p,
>>  	return rc;
>>  }
>>  
>> +/* Add the dirty-shutdown-counter value to the pdsm */
>> +static int papr_psdm_dsc(struct papr_scm_priv *p,
>                    ^^^^ should be pdsm
>> +			 union nd_pdsm_payload *payload)
>> +{
>> +	payload->health.extension_flags |= PDSM_DIMM_DSC_VALID;
>> +	payload->health.dimm_dsc = p->dirty_shutdown_counter;
>> +
>> +	return sizeof(struct nd_papr_pdsm_health);
>> +}
>> +
>>  /* 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)
>> @@ -646,6 +659,8 @@ static int papr_pdsm_health(struct papr_scm_priv *p,
>>  
>>  	/* Populate the fuel gauge meter in the payload */
>>  	papr_pdsm_fuel_gauge(p, payload);
>> +	/* Populate the dirty-shutdown-counter field */
>> +	papr_psdm_dsc(p, payload);
>              ^^^^ same typo
>
> Thanks,
> Santosh
>
>>  
>>  	rc = sizeof(struct nd_papr_pdsm_health);
>>  
>> @@ -907,6 +922,16 @@ static ssize_t flags_show(struct device *dev,
>>  }
>>  DEVICE_ATTR_RO(flags);
>>  
>> +static ssize_t dirty_shutdown_show(struct device *dev,
>> +			  struct device_attribute *attr, char *buf)
>> +{
>> +	struct nvdimm *dimm = to_nvdimm(dev);
>> +	struct papr_scm_priv *p = nvdimm_provider_data(dimm);
>> +
>> +	return sysfs_emit(buf, "%llu\n", p->dirty_shutdown_counter);
>> +}
>> +DEVICE_ATTR_RO(dirty_shutdown);
>> +
>>  static umode_t papr_nd_attribute_visible(struct kobject *kobj,
>>  					 struct attribute *attr, int n)
>>  {
>> @@ -925,6 +950,7 @@ static umode_t papr_nd_attribute_visible(struct kobject *kobj,
>>  static struct attribute *papr_nd_attributes[] = {
>>  	&dev_attr_flags.attr,
>>  	&dev_attr_perf_stats.attr,
>> +	&dev_attr_dirty_shutdown.attr,
>>  	NULL,
>>  };
>>  
>> @@ -1149,6 +1175,10 @@ static int papr_scm_probe(struct platform_device *pdev)
>>  	p->is_volatile = !of_property_read_bool(dn, "ibm,cache-flush-required");
>>  	p->hcall_flush_required = of_property_read_bool(dn, "ibm,hcall-flush-required");
>>  
>> +	if (of_property_read_u64(dn, "ibm,persistence-failed-count",
>> +				 &p->dirty_shutdown_counter))
>> +		p->dirty_shutdown_counter = 0;
>> +
>>  	/* We just need to ensure that set cookies are unique across */
>>  	uuid_parse(uuid_str, (uuid_t *) uuid);
>>  	/*
>> -- 
>> 2.31.1
>