[PATCH v7 5/5] powerpc/papr_scm: Implement support for PAPR_SCM_PDSM_HEALTH

[Vaibhav Jain]

This patch implements support for PDSM request 'PAPR_SCM_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_scm_get_health() that queries the scm-dimm health information and
then copies this information to the package payload whose layout is
defined by 'struct nd_papr_pdsm_health'.

The patch also introduces a new member 'struct papr_scm_priv.health'
thats an instance of 'struct nd_papr_pdsm_health' to cache the health
information of a nvdimm. As a result functions drc_pmem_query_health()
and flags_show() are updated to populate and use this new struct
instead of a u64 integer that was earlier used.

Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@xxxxxxxxxxxxx>
Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
---
Changelog:
v6..v7:
* Updated flags_show() to use seq_buf_printf(). [Mpe]
* Updated papr_scm_get_health() to use newly introduced
  __drc_pmem_query_health() bypassing the cache [Mpe].

v5..v6:
* Added attribute '__packed' to 'struct nd_papr_pdsm_health_v1' to
  gaurd against possibility of different compilers adding different
  paddings to the struct [ Dan Williams ]

* Updated 'struct nd_papr_pdsm_health_v1' to use __u8 instead of
  'bool' and also updated drc_pmem_query_health() to take this into
  account. [ Dan Williams ]

v4..v5:
* None

v3..v4:
* Call the DSM_PAPR_SCM_HEALTH service function from
  papr_scm_service_dsm() instead of papr_scm_ndctl(). [Aneesh]

v2..v3:
* Updated struct nd_papr_scm_dimm_health_stat_v1 to use '__xx' types
  as its exported to the userspace [Aneesh]
* Changed the constants DSM_PAPR_SCM_DIMM_XX indicating dimm health
  from enum to #defines [Aneesh]

v1..v2:
* New patch in the series
---
 arch/powerpc/include/uapi/asm/papr_scm_pdsm.h |  39 ++++++
 arch/powerpc/platforms/pseries/papr_scm.c     | 125 +++++++++++++++---
 2 files changed, 147 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/include/uapi/asm/papr_scm_pdsm.h b/arch/powerpc/include/uapi/asm/papr_scm_pdsm.h
index 671693439c1c..db0cf550dabe 100644
--- a/arch/powerpc/include/uapi/asm/papr_scm_pdsm.h
+++ b/arch/powerpc/include/uapi/asm/papr_scm_pdsm.h
@@ -113,6 +113,7 @@ struct nd_pdsm_cmd_pkg {
  */
 enum papr_scm_pdsm {
 	PAPR_SCM_PDSM_MIN = 0x0,
+	PAPR_SCM_PDSM_HEALTH,
 	PAPR_SCM_PDSM_MAX,
 };
 
@@ -131,4 +132,42 @@ static inline void *pdsm_cmd_to_payload(struct nd_pdsm_cmd_pkg *pcmd)
 		return (void *)((__u8 *) pcmd + pcmd->payload_offset);
 }
 
+/* Various scm-dimm 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_SCM_PDSM_HEALTH
+ * Various flags indicate the health status of the dimm.
+ *
+ * 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_v1 {
+	__u8 dimm_unarmed;
+	__u8 dimm_bad_shutdown;
+	__u8 dimm_bad_restore;
+	__u8 dimm_scrubbed;
+	__u8 dimm_locked;
+	__u8 dimm_encrypted;
+	__u16 dimm_health;
+} __packed;
+
+/*
+ * Typedef the current struct for dimm_health so that any application
+ * or kernel recompiled after introducing a new version automatically
+ * supports the new version.
+ */
+#define nd_papr_pdsm_health nd_papr_pdsm_health_v1
+
+/* Current version number for the dimm health struct */
+#define ND_PAPR_PDSM_HEALTH_VERSION 1
+
 #endif /* _UAPI_ASM_POWERPC_PAPR_SCM_PDSM_H_ */
diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index ed4b49a6f1e1..c59bf17ad054 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -88,7 +88,7 @@ struct papr_scm_priv {
 	unsigned long lasthealth_jiffies;
 
 	/* Health information for the dimm */
-	u64 health_bitmap;
+	struct nd_papr_pdsm_health health;
 };
 
 static int drc_pmem_bind(struct papr_scm_priv *p)
@@ -201,6 +201,7 @@ static int drc_pmem_query_n_bind(struct papr_scm_priv *p)
 static int __drc_pmem_query_health(struct papr_scm_priv *p)
 {
 	unsigned long ret[PLPAR_HCALL_BUFSIZE];
+	u64 health;
 	s64 rc;
 
 	/* issue the hcall */
@@ -208,18 +209,46 @@ static int __drc_pmem_query_health(struct papr_scm_priv *p)
 	if (rc != H_SUCCESS) {
 		dev_err(&p->pdev->dev,
 			 "Failed to query health information, Err:%lld\n", rc);
-		rc = -ENXIO;
-		goto out;
+		return -ENXIO;
 	}
 
 	p->lasthealth_jiffies = jiffies;
-	p->health_bitmap = ret[0] & ret[1];
+	health = ret[0] & ret[1];
 
 	dev_dbg(&p->pdev->dev,
 		"Queried dimm health info. Bitmap:0x%016lx Mask:0x%016lx\n",
 		ret[0], ret[1]);
-out:
-	return rc;
+
+	memset(&p->health, 0, sizeof(p->health));
+
+	/* Check for various masks in bitmap and set the buffer */
+	if (health & PAPR_SCM_DIMM_UNARMED_MASK)
+		p->health.dimm_unarmed = 1;
+
+	if (health & PAPR_SCM_DIMM_BAD_SHUTDOWN_MASK)
+		p->health.dimm_bad_shutdown = 1;
+
+	if (health & PAPR_SCM_DIMM_BAD_RESTORE_MASK)
+		p->health.dimm_bad_restore = 1;
+
+	if (health & PAPR_SCM_DIMM_ENCRYPTED)
+		p->health.dimm_encrypted = 1;
+
+	if (health & PAPR_SCM_DIMM_SCRUBBED_AND_LOCKED) {
+		p->health.dimm_locked = 1;
+		p->health.dimm_scrubbed = 1;
+	}
+
+	if (health & PAPR_SCM_DIMM_HEALTH_UNHEALTHY)
+		p->health.dimm_health = PAPR_PDSM_DIMM_UNHEALTHY;
+
+	if (health & PAPR_SCM_DIMM_HEALTH_CRITICAL)
+		p->health.dimm_health = PAPR_PDSM_DIMM_CRITICAL;
+
+	if (health & PAPR_SCM_DIMM_HEALTH_FATAL)
+		p->health.dimm_health = PAPR_PDSM_DIMM_FATAL;
+
+	return 0;
 }
 
 /* Min interval in seconds for assuming stable dimm health */
@@ -403,6 +432,58 @@ static int is_cmd_valid(struct nvdimm *nvdimm, unsigned int cmd, void *buf,
 	return 0;
 }
 
+/* Fetch the DIMM health info and populate it in provided package. */
+static int papr_scm_get_health(struct papr_scm_priv *p,
+			       struct nd_pdsm_cmd_pkg *pkg)
+{
+	int rc;
+	size_t copysize = sizeof(p->health);
+
+	/* 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)
+		goto out_unlock;
+	/*
+	 * If the requested payload version is greater than one we know
+	 * about, return the payload version we know about and let
+	 * caller/userspace handle.
+	 */
+	if (pkg->payload_version > ND_PAPR_PDSM_HEALTH_VERSION)
+		pkg->payload_version = ND_PAPR_PDSM_HEALTH_VERSION;
+
+	if (pkg->hdr.nd_size_out < copysize) {
+		dev_dbg(&p->pdev->dev, "Truncated payload (%u). Expected (%lu)",
+			pkg->hdr.nd_size_out, copysize);
+		rc = -ENOSPC;
+		goto out_unlock;
+	}
+
+	dev_dbg(&p->pdev->dev, "Copying payload size=%lu version=0x%x\n",
+		copysize, pkg->payload_version);
+
+	/* Copy the health struct to the payload */
+	memcpy(pdsm_cmd_to_payload(pkg), &p->health, copysize);
+	pkg->hdr.nd_fw_size = copysize;
+
+out_unlock:
+	mutex_unlock(&p->health_mutex);
+
+out:
+	/*
+	 * Put the error in out package and return success from function
+	 * so that errors if any are propogated back to userspace.
+	 */
+	pkg->cmd_status = rc;
+	dev_dbg(&p->pdev->dev, "completion code = %d\n", rc);
+
+	return 0;
+}
+
 static int papr_scm_service_pdsm(struct papr_scm_priv *p,
 				struct nd_pdsm_cmd_pkg *call_pkg)
 {
@@ -417,6 +498,9 @@ static int papr_scm_service_pdsm(struct papr_scm_priv *p,
 
 	/* Depending on the DSM command call appropriate service routine */
 	switch (call_pkg->hdr.nd_command) {
+	case PAPR_SCM_PDSM_HEALTH:
+		return papr_scm_get_health(p, call_pkg);
+
 	default:
 		dev_dbg(&p->pdev->dev, "Unsupported PDSM request 0x%llx\n",
 			call_pkg->hdr.nd_command);
@@ -485,34 +569,41 @@ static ssize_t flags_show(struct device *dev,
 	struct nvdimm *dimm = to_nvdimm(dev);
 	struct papr_scm_priv *p = nvdimm_provider_data(dimm);
 	struct seq_buf s;
-	u64 health;
 	int rc;
 
 	rc = drc_pmem_query_health(p);
 	if (rc)
 		return rc;
 
-	/* Copy health_bitmap locally, check masks & update out buffer */
-	health = READ_ONCE(p->health_bitmap);
-
 	seq_buf_init(&s, buf, PAGE_SIZE);
-	if (health & PAPR_SCM_DIMM_UNARMED_MASK)
+
+	/* Protect concurrent modifications to papr_scm_priv */
+	rc = mutex_lock_interruptible(&p->health_mutex);
+	if (rc)
+		return rc;
+
+	if (p->health.dimm_unarmed)
 		seq_buf_printf(&s, "not_armed ");
 
-	if (health & PAPR_SCM_DIMM_BAD_SHUTDOWN_MASK)
+	if (p->health.dimm_bad_shutdown)
 		seq_buf_printf(&s, "flush_fail ");
 
-	if (health & PAPR_SCM_DIMM_BAD_RESTORE_MASK)
+	if (p->health.dimm_bad_restore)
 		seq_buf_printf(&s, "restore_fail ");
 
-	if (health & PAPR_SCM_DIMM_ENCRYPTED)
+	if (p->health.dimm_encrypted)
 		seq_buf_printf(&s, "encrypted ");
 
-	if (health & PAPR_SCM_DIMM_SMART_EVENT_MASK)
+	if (p->health.dimm_health)
 		seq_buf_printf(&s, "smart_notify ");
 
-	if (health & PAPR_SCM_DIMM_SCRUBBED_AND_LOCKED)
-		seq_buf_printf(&s, "scrubbed locked ");
+	if (p->health.dimm_scrubbed)
+		seq_buf_printf(&s, "scrubbed ");
+
+	if (p->health.dimm_locked)
+		seq_buf_printf(&s, "locked ");
+
+	mutex_unlock(&p->health_mutex);
 
 	if (seq_buf_used(&s))
 		seq_buf_printf(&s, "\n");
-- 
2.26.2