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: "Aneesh Kumar K . V" <aneesh.ku...@linux.ibm.com>
Cc: Dan Williams <dan.j.willi...@intel.com>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Ira Weiny <ira.we...@intel.com>
Signed-off-by: Vaibhav Jain <vaib...@linux.ibm.com>
---
Changelog:

v7..v8:
* None

Resend:
* None

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 c4bae3208e73..f81d714279f0 100644
--- a/arch/powerpc/include/uapi/asm/papr_scm_pdsm.h
+++ b/arch/powerpc/include/uapi/asm/papr_scm_pdsm.h
@@ -115,6 +115,7 @@ struct nd_pdsm_cmd_pkg {
  */
 enum papr_scm_pdsm {
        PAPR_SCM_PDSM_MIN = 0x0,
+       PAPR_SCM_PDSM_HEALTH,
        PAPR_SCM_PDSM_MAX,
 };
 
@@ -133,4 +134,42 @@ static inline void *pdsm_cmd_to_payload(struct 
nd_pdsm_cmd_pkg *pcmd)
                return (void *)(pcmd->payload);
 }
 
+/* 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 fcb8afee97dc..adf1fb819c56 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;
        long 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:%ld\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

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