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Subject[PATCH v8 3/5] powerpc/papr_scm: Fetch nvdimm health information from PHYP
Date
Implement support for fetching nvdimm health information via
H_SCM_HEALTH hcall as documented in Ref[1]. The hcall returns a pair
of 64-bit bitmap, bitwise-and of which is then stored in
'struct papr_scm_priv' and subsequently partially exposed to
user-space via newly introduced dimm specific attribute
'papr/flags'. Since the hcall is costly, the health information is
cached and only re-queried, 60s after the previous successful hcall.

The patch also adds a documentation text describing flags reported by
the the new sysfs attribute 'papr/flags' is also introduced at
Documentation/ABI/testing/sysfs-bus-papr-scm.

[1] commit 58b278f568f0 ("powerpc: Provide initial documentation for
PAPR hcalls")

Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
---
Changelog:

v7..v8:
* Update type of variable 'rc' in __drc_pmem_query_health() and
drc_pmem_query_health() to long and int respectively. [ Ira ]
* Updated the patch description to s/64 bit Big Endian Number/64-bit
bitmap/ [ Ira, Aneesh ].

Resend:
* None

v6..v7 :
* Used the exported buf_seq_printf() function to generate content for
'papr/flags'
* Moved the PAPR_SCM_DIMM_* bit-flags macro definitions to papr_scm.c
and removed the papr_scm.h file [Mpe]
* Some minor consistency issued in sysfs-bus-papr-scm
documentation. [Mpe]
* s/dimm_mutex/health_mutex/g [Mpe]
* Split drc_pmem_query_health() into two function one of which takes
care of caching and locking. [Mpe]
* Fixed a local copy creation of dimm health information using
READ_ONCE(). [Mpe]

v5..v6 :
* Change the flags sysfs attribute from 'papr_flags' to 'papr/flags'
[Dan Williams]
* Include documentation for 'papr/flags' attr [Dan Williams]
* Change flag 'save_fail' to 'flush_fail' [Dan Williams]
* Caching of health bitmap to reduce expensive hcalls [Dan Williams]
* Removed usage of PPC_BIT from 'papr-scm.h' header [Mpe]
* Replaced two __be64 integers from papr_scm_priv to a single u64
integer [Mpe]
* Updated patch description to reflect the changes made in this
version.
* Removed avoidable usage of 'papr_scm_priv.dimm_mutex' from
flags_show() [Dan Williams]

v4..v5 :
* None

v3..v4 :
* None

v2..v3 :
* Removed PAPR_SCM_DIMM_HEALTH_NON_CRITICAL as a condition for
NVDIMM unarmed [Aneesh]

v1..v2 :
* New patch in the series.
---
Documentation/ABI/testing/sysfs-bus-papr-scm | 27 +++
arch/powerpc/platforms/pseries/papr_scm.c | 169 ++++++++++++++++++-
2 files changed, 194 insertions(+), 2 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-bus-papr-scm

diff --git a/Documentation/ABI/testing/sysfs-bus-papr-scm b/Documentation/ABI/testing/sysfs-bus-papr-scm
new file mode 100644
index 000000000000..6143d06072f1
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-papr-scm
@@ -0,0 +1,27 @@
+What: /sys/bus/nd/devices/nmemX/papr/flags
+Date: Apr, 2020
+KernelVersion: v5.8
+Contact: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, linux-nvdimm@lists.01.org,
+Description:
+ (RO) Report flags indicating various states of a
+ papr-scm NVDIMM device. Each flag maps to a one or
+ more bits set in the dimm-health-bitmap retrieved in
+ response to H_SCM_HEALTH hcall. The details of the bit
+ flags returned in response to this hcall is available
+ at 'Documentation/powerpc/papr_hcalls.rst' . Below are
+ the flags reported in this sysfs file:
+
+ * "not_armed" : Indicates that NVDIMM contents will not
+ survive a power cycle.
+ * "flush_fail" : Indicates that NVDIMM contents
+ couldn't be flushed during last
+ shut-down event.
+ * "restore_fail": Indicates that NVDIMM contents
+ couldn't be restored during NVDIMM
+ initialization.
+ * "encrypted" : NVDIMM contents are encrypted.
+ * "smart_notify": There is health event for the NVDIMM.
+ * "scrubbed" : Indicating that contents of the
+ NVDIMM have been scrubbed.
+ * "locked" : Indicating that NVDIMM contents cant
+ be modified until next power cycle.
diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index f35592423380..010cd9aae488 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -12,6 +12,7 @@
#include <linux/libnvdimm.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
+#include <linux/seq_buf.h>

#include <asm/plpar_wrappers.h>

@@ -22,6 +23,44 @@
(1ul << ND_CMD_GET_CONFIG_DATA) | \
(1ul << ND_CMD_SET_CONFIG_DATA))

+/* DIMM health bitmap bitmap indicators */
+/* SCM device is unable to persist memory contents */
+#define PAPR_SCM_DIMM_UNARMED (1ULL << (63 - 0))
+/* SCM device failed to persist memory contents */
+#define PAPR_SCM_DIMM_SHUTDOWN_DIRTY (1ULL << (63 - 1))
+/* SCM device contents are persisted from previous IPL */
+#define PAPR_SCM_DIMM_SHUTDOWN_CLEAN (1ULL << (63 - 2))
+/* SCM device contents are not persisted from previous IPL */
+#define PAPR_SCM_DIMM_EMPTY (1ULL << (63 - 3))
+/* SCM device memory life remaining is critically low */
+#define PAPR_SCM_DIMM_HEALTH_CRITICAL (1ULL << (63 - 4))
+/* SCM device will be garded off next IPL due to failure */
+#define PAPR_SCM_DIMM_HEALTH_FATAL (1ULL << (63 - 5))
+/* SCM contents cannot persist due to current platform health status */
+#define PAPR_SCM_DIMM_HEALTH_UNHEALTHY (1ULL << (63 - 6))
+/* SCM device is unable to persist memory contents in certain conditions */
+#define PAPR_SCM_DIMM_HEALTH_NON_CRITICAL (1ULL << (63 - 7))
+/* SCM device is encrypted */
+#define PAPR_SCM_DIMM_ENCRYPTED (1ULL << (63 - 8))
+/* SCM device has been scrubbed and locked */
+#define PAPR_SCM_DIMM_SCRUBBED_AND_LOCKED (1ULL << (63 - 9))
+
+/* Bits status indicators for health bitmap indicating unarmed dimm */
+#define PAPR_SCM_DIMM_UNARMED_MASK (PAPR_SCM_DIMM_UNARMED | \
+ PAPR_SCM_DIMM_HEALTH_UNHEALTHY)
+
+/* Bits status indicators for health bitmap indicating unflushed dimm */
+#define PAPR_SCM_DIMM_BAD_SHUTDOWN_MASK (PAPR_SCM_DIMM_SHUTDOWN_DIRTY)
+
+/* Bits status indicators for health bitmap indicating unrestored dimm */
+#define PAPR_SCM_DIMM_BAD_RESTORE_MASK (PAPR_SCM_DIMM_EMPTY)
+
+/* Bit status indicators for smart event notification */
+#define PAPR_SCM_DIMM_SMART_EVENT_MASK (PAPR_SCM_DIMM_HEALTH_CRITICAL | \
+ PAPR_SCM_DIMM_HEALTH_FATAL | \
+ PAPR_SCM_DIMM_HEALTH_UNHEALTHY)
+
+/* private struct associated with each region */
struct papr_scm_priv {
struct platform_device *pdev;
struct device_node *dn;
@@ -39,6 +78,15 @@ struct papr_scm_priv {
struct resource res;
struct nd_region *region;
struct nd_interleave_set nd_set;
+
+ /* Protect dimm health data from concurrent read/writes */
+ struct mutex health_mutex;
+
+ /* Last time the health information of the dimm was updated */
+ unsigned long lasthealth_jiffies;
+
+ /* Health information for the dimm */
+ u64 health_bitmap;
};

static int drc_pmem_bind(struct papr_scm_priv *p)
@@ -144,6 +192,62 @@ static int drc_pmem_query_n_bind(struct papr_scm_priv *p)
return drc_pmem_bind(p);
}

+/*
+ * Issue hcall to retrieve dimm health info and populate papr_scm_priv with the
+ * health information.
+ */
+static int __drc_pmem_query_health(struct papr_scm_priv *p)
+{
+ unsigned long ret[PLPAR_HCALL_BUFSIZE];
+ long rc;
+
+ /* issue the hcall */
+ rc = plpar_hcall(H_SCM_HEALTH, ret, p->drc_index);
+ if (rc != H_SUCCESS) {
+ dev_err(&p->pdev->dev,
+ "Failed to query health information, Err:%ld\n", rc);
+ rc = -ENXIO;
+ goto out;
+ }
+
+ p->lasthealth_jiffies = jiffies;
+ p->health_bitmap = 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;
+}
+
+/* Min interval in seconds for assuming stable dimm health */
+#define MIN_HEALTH_QUERY_INTERVAL 60
+
+/* Query cached health info and if needed call drc_pmem_query_health */
+static int drc_pmem_query_health(struct papr_scm_priv *p)
+{
+ unsigned long cache_timeout;
+ int rc;
+
+ /* Protect concurrent modifications to papr_scm_priv */
+ rc = mutex_lock_interruptible(&p->health_mutex);
+ if (rc)
+ return rc;
+
+ /* Jiffies offset for which the health data is assumed to be same */
+ cache_timeout = p->lasthealth_jiffies +
+ msecs_to_jiffies(MIN_HEALTH_QUERY_INTERVAL * 1000);
+
+ /* Fetch new health info is its older than MIN_HEALTH_QUERY_INTERVAL */
+ if (time_after(jiffies, cache_timeout))
+ rc = __drc_pmem_query_health(p);
+ else
+ /* Assume cached health data is valid */
+ rc = 0;
+
+ mutex_unlock(&p->health_mutex);
+ return rc;
+}

static int papr_scm_meta_get(struct papr_scm_priv *p,
struct nd_cmd_get_config_data_hdr *hdr)
@@ -286,6 +390,64 @@ static int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc,
return 0;
}

+static ssize_t flags_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);
+ 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)
+ seq_buf_printf(&s, "not_armed ");
+
+ if (health & PAPR_SCM_DIMM_BAD_SHUTDOWN_MASK)
+ seq_buf_printf(&s, "flush_fail ");
+
+ if (health & PAPR_SCM_DIMM_BAD_RESTORE_MASK)
+ seq_buf_printf(&s, "restore_fail ");
+
+ if (health & PAPR_SCM_DIMM_ENCRYPTED)
+ seq_buf_printf(&s, "encrypted ");
+
+ if (health & PAPR_SCM_DIMM_SMART_EVENT_MASK)
+ seq_buf_printf(&s, "smart_notify ");
+
+ if (health & PAPR_SCM_DIMM_SCRUBBED_AND_LOCKED)
+ seq_buf_printf(&s, "scrubbed locked ");
+
+ if (seq_buf_used(&s))
+ seq_buf_printf(&s, "\n");
+
+ return seq_buf_used(&s);
+}
+DEVICE_ATTR_RO(flags);
+
+/* papr_scm specific dimm attributes */
+static struct attribute *papr_scm_nd_attributes[] = {
+ &dev_attr_flags.attr,
+ NULL,
+};
+
+static struct attribute_group papr_scm_nd_attribute_group = {
+ .name = "papr",
+ .attrs = papr_scm_nd_attributes,
+};
+
+static const struct attribute_group *papr_scm_dimm_attr_groups[] = {
+ &papr_scm_nd_attribute_group,
+ NULL,
+};
+
static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
{
struct device *dev = &p->pdev->dev;
@@ -312,8 +474,8 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
dimm_flags = 0;
set_bit(NDD_LABELING, &dimm_flags);

- p->nvdimm = nvdimm_create(p->bus, p, NULL, dimm_flags,
- PAPR_SCM_DIMM_CMD_MASK, 0, NULL);
+ p->nvdimm = nvdimm_create(p->bus, p, papr_scm_dimm_attr_groups,
+ dimm_flags, PAPR_SCM_DIMM_CMD_MASK, 0, NULL);
if (!p->nvdimm) {
dev_err(dev, "Error creating DIMM object for %pOF\n", p->dn);
goto err;
@@ -399,6 +561,9 @@ static int papr_scm_probe(struct platform_device *pdev)
if (!p)
return -ENOMEM;

+ /* Initialize the dimm mutex */
+ mutex_init(&p->health_mutex);
+
/* optional DT properties */
of_property_read_u32(dn, "ibm,metadata-size", &metadata_size);

--
2.26.2
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