Commit de21e137 authored by Vaibhav Jain's avatar Vaibhav Jain Committed by Michael Ellerman
Browse files

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

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: default avatarVaibhav Jain <vaibhav@linux.ibm.com>
Reviewed-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210624080621.252038-1-vaibhav@linux.ibm.com
parent ed78f56e

arch/powerpc/include/uapi/asm/papr_pdsm.h

+6 −0
Original line number Diff line number Diff line
@@ -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];

	};

arch/powerpc/platforms/pseries/papr_scm.c

+30 −0
Original line number Diff line number Diff line
@@ -115,6 +115,9 @@ 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;

};
@@ -604,6 +607,16 @@ 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_pdsm_dsc(struct papr_scm_priv *p,

			 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)
@@ -647,6 +660,8 @@ 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_pdsm_dsc(p, payload);



	rc = sizeof(struct nd_papr_pdsm_health);
@@ -908,6 +923,16 @@ 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)

{
@@ -926,6 +951,7 @@ 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,

};
@@ -1151,6 +1177,10 @@ 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);