powerpc/papr_scm: Implement support for PAPR_PDSM_HEALTH

This patch implements support for PDSM request 'PAPR_PDSM_HEALTH'
that returns a newly introduced 'struct nd_papr_pdsm_health' instance
containing dimm health information back to user space in response to
ND_CMD_CALL. This functionality is implemented in newly introduced
papr_pdsm_health() that queries the nvdimm health information and
then copies this information to the package payload whose layout is
defined by 'struct nd_papr_pdsm_health'.

Signed-off-by: Vaibhav Jain <[e-mail]>
Cc: "Aneesh Kumar K . V" <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Ira Weiny <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dan Williams <[e-mail]>

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

···
 #define ND_PDSM_HDR_SIZE \
 	(sizeof(struct nd_pkg_pdsm) - ND_PDSM_PAYLOAD_MAX_SIZE)
 
+/* Various nvdimm health indicators */
+#define PAPR_PDSM_DIMM_HEALTHY       0
+#define PAPR_PDSM_DIMM_UNHEALTHY     1
+#define PAPR_PDSM_DIMM_CRITICAL      2
+#define PAPR_PDSM_DIMM_FATAL         3
+
+/*
+ * Struct exchanged between kernel & ndctl in for PAPR_PDSM_HEALTH
+ * Various flags indicate the health status of the dimm.
+ *
+ * extension_flags	: Any extension fields present in the struct.
+ * dimm_unarmed		: Dimm not armed. So contents wont persist.
+ * dimm_bad_shutdown	: Previous shutdown did not persist contents.
+ * dimm_bad_restore	: Contents from previous shutdown werent restored.
+ * dimm_scrubbed	: Contents of the dimm have been scrubbed.
+ * 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
+ */
+struct nd_papr_pdsm_health {
+	union {
+		struct {
+			__u32 extension_flags;
+			__u8 dimm_unarmed;
+			__u8 dimm_bad_shutdown;
+			__u8 dimm_bad_restore;
+			__u8 dimm_scrubbed;
+			__u8 dimm_locked;
+			__u8 dimm_encrypted;
+			__u16 dimm_health;
+		};
+		__u8 buf[ND_PDSM_PAYLOAD_MAX_SIZE];
+	};
+};
+
 /*
  * Methods to be embedded in ND_CMD_CALL request. These are sent to the kernel
  * via 'nd_cmd_pkg.nd_command' member of the ioctl struct
  */
 enum papr_pdsm {
 	PAPR_PDSM_MIN = 0x0,
+	PAPR_PDSM_HEALTH,
 	PAPR_PDSM_MAX,
 };
 
 /* Maximal union that can hold all possible payload types */
 union nd_pdsm_payload {
+	struct nd_papr_pdsm_health health;
 	__u8 buf[ND_PDSM_PAYLOAD_MAX_SIZE];
 } __packed;
 

arch/powerpc/platforms/pseries/papr_scm.c

···
 	return 0;
 }
 
+/* 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)
+{
+	int rc;
+
+	/* Ensure dimm health mutex is taken preventing concurrent access */
+	rc = mutex_lock_interruptible(&p->health_mutex);
+	if (rc)
+		goto out;
+
+	/* Always fetch upto date dimm health data ignoring cached values */
+	rc = __drc_pmem_query_health(p);
+	if (rc) {
+		mutex_unlock(&p->health_mutex);
+		goto out;
+	}
+
+	/* update health struct with various flags derived from health bitmap */
+	payload->health = (struct nd_papr_pdsm_health) {
+		.extension_flags = 0,
+		.dimm_unarmed = !!(p->health_bitmap & PAPR_PMEM_UNARMED_MASK),
+		.dimm_bad_shutdown = !!(p->health_bitmap & PAPR_PMEM_BAD_SHUTDOWN_MASK),
+		.dimm_bad_restore = !!(p->health_bitmap & PAPR_PMEM_BAD_RESTORE_MASK),
+		.dimm_scrubbed = !!(p->health_bitmap & PAPR_PMEM_SCRUBBED_AND_LOCKED),
+		.dimm_locked = !!(p->health_bitmap & PAPR_PMEM_SCRUBBED_AND_LOCKED),
+		.dimm_encrypted = !!(p->health_bitmap & PAPR_PMEM_ENCRYPTED),
+		.dimm_health = PAPR_PDSM_DIMM_HEALTHY,
+	};
+
+	/* Update field dimm_health based on health_bitmap flags */
+	if (p->health_bitmap & PAPR_PMEM_HEALTH_FATAL)
+		payload->health.dimm_health = PAPR_PDSM_DIMM_FATAL;
+	else if (p->health_bitmap & PAPR_PMEM_HEALTH_CRITICAL)
+		payload->health.dimm_health = PAPR_PDSM_DIMM_CRITICAL;
+	else if (p->health_bitmap & PAPR_PMEM_HEALTH_UNHEALTHY)
+		payload->health.dimm_health = PAPR_PDSM_DIMM_UNHEALTHY;
+
+	/* struct populated hence can release the mutex now */
+	mutex_unlock(&p->health_mutex);
+	rc = sizeof(struct nd_papr_pdsm_health);
+
+out:
+	return rc;
+}
+
 /*
  * 'struct pdsm_cmd_desc'
  * Identifies supported PDSMs' expected length of in/out payloads
···
 	},
 	/* New PDSM command descriptors to be added below */
 
+	[PAPR_PDSM_HEALTH] = {
+		.size_in = 0,
+		.size_out = sizeof(struct nd_papr_pdsm_health),
+		.service = papr_pdsm_health,
+	},
 	/* Empty */
 	[PAPR_PDSM_MAX] = {
 		.size_in = 0,