[PATCH v4 0/4] powerpc/papr_scm: Add support for reporting nvdimm health

[Vaibhav Jain]

The PAPR standard[1][3] provides mechanisms to query the health and
performance stats of an NVDIMM via various hcalls as described in Ref[2].
Until now these stats were never available nor exposed to the user-space
tools like 'ndctl'. This is partly due to PAPR platform not having support
for ACPI and NFIT. Hence 'ndctl' is unable to query and report the dimm
health status and a user had no way to determine the current health status
of a NDVIMM.

To overcome this limitation, this patch-set updates papr_scm kernel module
to query and fetch nvdimm health stats using hcalls described in Ref[2].
This health and performance stats are then exposed to userspace via syfs
and Dimm-Specific-Methods(DSM) issued by libndctl.

These changes coupled with proposed ndtcl changes located at Ref[4] should
provide a way for the user to retrieve NVDIMM health status using ndtcl.

Below is a sample output using proposed kernel + ndctl for PAPR NVDIMM in
a emulation environment:

 # ndctl list -DH
[
  {
    "dev":"nmem0",
    "health":{
      "health_state":"fatal",
      "shutdown_state":"dirty"
    }
  }
]

Dimm health report output on a pseries guest lpar with vPMEM or HMS
based nvdimms that are in perfectly healthy conditions:
	
 # ndctl list -d nmem0 -H
[
  {
    "dev":"nmem0",
    "health":{
      "health_state":"ok",
      "shutdown_state":"clean"
    }
  }
]

PAPR Dimm-Specific-Methods(DSM)
================================

As the name suggests DSMs are used by vendor specific code in libndctl to
execute certain operations or fetch certain information for NVDIMMS. DSMs
can be sent to papr_scm module via libndctl (userspace) and libnvdimm
(kernel) using the ND_CMD_CALL ioctl which can be handled in the dimm
control function papr_scm_ndctl(). For PAPR this patchset proposes a single
DSM to retrieve DIMM health, defined in the newly introduced uapi header
named 'papr_scm_dsm.h'. Support for more DSMs will be added in future.

Structure of the patch-set
==========================

The patchset starts with implementing support for fetching nvdimm health
information from PHYP and partially exposing it to user-space via nvdimm
flags.

Second & Third patches deal with implementing support for servicing DSM
commands papr_scm.

Finally the Fourth patch implements support for servicing DSM
'DSM_PAPR_SCM_HEALTH' that returns the nvdimm health information to
libndctl.

Changelog:
==========

v3..v4:

* Restructured papr_scm_ndctl() to dispatch ND_CMD_CALL commands to a new
  function named papr_scm_service_dsm() to serivice DSM requests. [Aneesh]

v2..v3:

* Updated the papr_scm_dsm.h header to be more confimant general kernel
  guidelines for UAPI headers. [Aneesh]

* Changed the definition of macro PAPR_SCM_DIMM_UNARMED_MASK to not
  include case when the nvdimm is unarmed because its a vPMEM
  nvdimm. [Aneesh]

v1..v2:

* Restructured the patch-set based on review comments on V1 patch-set to
simplify the patch review. Multiple small patches have been combined into
single patches to reduce cross referencing that was needed in earlier
patch-set. Hence most of the patches in this patch-set as now new. [Aneesh]

* Removed the initial work done for fetch nvdimm performance statistics.
These changes will be re-proposed in a separate patch-set. [Aneesh]

* Simplified handling of versioning of 'struct
nd_papr_scm_dimm_health_stat_v1' as only one version of the structure is
currently in existence.

References:
[1]: "Power Architecture Platform Reference"
      https://en.wikipedia.org/wiki/Power_Architecture_Platform_Reference
[2]: commit 58b278f568f0
     ("powerpc: Provide initial documentation for PAPR hcalls")
[3]: "Linux on Power Architecture Platform Reference"
     https://members.openpowerfoundation.org/document/dl/469
[4]: https://patchwork.kernel.org/project/linux-nvdimm/list/?series=244625

Vaibhav Jain (4):
  powerpc/papr_scm: Fetch nvdimm health information from PHYP
  ndctl/uapi: Introduce NVDIMM_FAMILY_PAPR_SCM as a new NVDIMM DSM
    family
  powerpc/papr_scm,uapi: Add support for handling PAPR DSM commands
  powerpc/papr_scm: Implement support for DSM_PAPR_SCM_HEALTH

 arch/powerpc/include/asm/papr_scm.h          |  48 ++++
 arch/powerpc/include/uapi/asm/papr_scm_dsm.h | 201 ++++++++++++++
 arch/powerpc/platforms/pseries/papr_scm.c    | 277 ++++++++++++++++++-
 include/uapi/linux/ndctl.h                   |   1 +
 4 files changed, 519 insertions(+), 8 deletions(-)
 create mode 100644 arch/powerpc/include/asm/papr_scm.h
 create mode 100644 arch/powerpc/include/uapi/asm/papr_scm_dsm.h

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