Re: [RESEND PATCH v9 3/5] powerpc/papr_scm: Fetch nvdimm health information from PHYP

From: Ira Weiny
Date: Tue Jun 02 2020 - 14:47:03 EST

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In reply to: Vaibhav Jain: "[RESEND PATCH v9 3/5] powerpc/papr_scm: Fetch nvdimm health information from PHYP"
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On Tue, Jun 02, 2020 at 03:44:36PM +0530, Vaibhav Jain wrote:
> 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-pmem.
>
> [1] commit 58b278f568f0 ("powerpc: Provide initial documentation for
> PAPR hcalls")
>
> Cc: "Aneesh Kumar K . V" <aneesh.kumar@xxxxxxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
> ---
> Changelog:
>
> Resend:
> * Added ack from Aneesh.
>
> v8..v9:
> * Rename some variables and defines to reduce usage of term SCM
> replacing it with PMEM [Dan Williams, Aneesh]
> * s/PAPR_SCM_DIMM/PAPR_PMEM/g
> * s/papr_scm_nd_attributes/papr_nd_attributes/g
> * s/papr_scm_nd_attribute_group/papr_nd_attribute_group/g
> * s/papr_scm_dimm_attr_groups/papr_nd_attribute_groups/g
> * Renamed file sysfs-bus-papr-scm to sysfs-bus-papr-pmem
>
> 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-pmem | 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-pmem
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-papr-pmem b/Documentation/ABI/testing/sysfs-bus-papr-pmem
> new file mode 100644
> index 000000000000..5b10d036a8d4
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-papr-pmem
> @@ -0,0 +1,27 @@
> +What: /sys/bus/nd/devices/nmemX/papr/flags
> +Date: Apr, 2020
> +KernelVersion: v5.8
> +Contact: linuxppc-dev <linuxppc-dev@xxxxxxxxxxxxxxxx>, linux-nvdimm@xxxxxxxxxxxx,
> +Description:
> + (RO) Report flags indicating various states of a
> + papr-pmem 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..149431594839 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_PMEM_UNARMED (1ULL << (63 - 0))
> +/* SCM device failed to persist memory contents */
> +#define PAPR_PMEM_SHUTDOWN_DIRTY (1ULL << (63 - 1))
> +/* SCM device contents are persisted from previous IPL */
> +#define PAPR_PMEM_SHUTDOWN_CLEAN (1ULL << (63 - 2))
> +/* SCM device contents are not persisted from previous IPL */
> +#define PAPR_PMEM_EMPTY (1ULL << (63 - 3))
> +/* SCM device memory life remaining is critically low */
> +#define PAPR_PMEM_HEALTH_CRITICAL (1ULL << (63 - 4))
> +/* SCM device will be garded off next IPL due to failure */
> +#define PAPR_PMEM_HEALTH_FATAL (1ULL << (63 - 5))
> +/* SCM contents cannot persist due to current platform health status */
> +#define PAPR_PMEM_HEALTH_UNHEALTHY (1ULL << (63 - 6))
> +/* SCM device is unable to persist memory contents in certain conditions */
> +#define PAPR_PMEM_HEALTH_NON_CRITICAL (1ULL << (63 - 7))
> +/* SCM device is encrypted */
> +#define PAPR_PMEM_ENCRYPTED (1ULL << (63 - 8))
> +/* SCM device has been scrubbed and locked */
> +#define PAPR_PMEM_SCRUBBED_AND_LOCKED (1ULL << (63 - 9))
> +
> +/* Bits status indicators for health bitmap indicating unarmed dimm */
> +#define PAPR_PMEM_UNARMED_MASK (PAPR_PMEM_UNARMED | \
> + PAPR_PMEM_HEALTH_UNHEALTHY)
> +
> +/* Bits status indicators for health bitmap indicating unflushed dimm */
> +#define PAPR_PMEM_BAD_SHUTDOWN_MASK (PAPR_PMEM_SHUTDOWN_DIRTY)
> +
> +/* Bits status indicators for health bitmap indicating unrestored dimm */
> +#define PAPR_PMEM_BAD_RESTORE_MASK (PAPR_PMEM_EMPTY)
> +
> +/* Bit status indicators for smart event notification */
> +#define PAPR_PMEM_SMART_EVENT_MASK (PAPR_PMEM_HEALTH_CRITICAL | \
> + PAPR_PMEM_HEALTH_FATAL | \
> + PAPR_PMEM_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;

I question if this really needs protection. But I don't think it hurts.

Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>

> +
> + /* 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_PMEM_UNARMED_MASK)
> + seq_buf_printf(&s, "not_armed ");
> +
> + if (health & PAPR_PMEM_BAD_SHUTDOWN_MASK)
> + seq_buf_printf(&s, "flush_fail ");
> +
> + if (health & PAPR_PMEM_BAD_RESTORE_MASK)
> + seq_buf_printf(&s, "restore_fail ");
> +
> + if (health & PAPR_PMEM_ENCRYPTED)
> + seq_buf_printf(&s, "encrypted ");
> +
> + if (health & PAPR_PMEM_SMART_EVENT_MASK)
> + seq_buf_printf(&s, "smart_notify ");
> +
> + if (health & PAPR_PMEM_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_nd_attributes[] = {
> + &dev_attr_flags.attr,
> + NULL,
> +};
> +
> +static struct attribute_group papr_nd_attribute_group = {
> + .name = "papr",
> + .attrs = papr_nd_attributes,
> +};
> +
> +static const struct attribute_group *papr_nd_attr_groups[] = {
> + &papr_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_nd_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
>

Next message: Qian Cai: "Re: [PATCH 11/14] x86/entry: Clarify irq_{enter,exit}_rcu()"
Previous message: Nick Desaulniers: "Re: [PATCH] ACPICA: fix UBSAN warning using __builtin_offsetof"
In reply to: Vaibhav Jain: "[RESEND PATCH v9 3/5] powerpc/papr_scm: Fetch nvdimm health information from PHYP"
Next in thread: Vaibhav Jain: "[RESEND PATCH v9 4/5] ndctl/papr_scm,uapi: Add support for PAPR nvdimm specific methods"
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