[PATCH 00/12] ACPI/NVDIMM: Runtime Firmware Activation

[Dan Williams]

Quoting the documentation:

    Some persistent memory devices run a firmware locally on the device /
    "DIMM" to perform tasks like media management, capacity provisioning,
    and health monitoring. The process of updating that firmware typically
    involves a reboot because it has implications for in-flight memory
    transactions. However, reboots are disruptive and at least the Intel
    persistent memory platform implementation, described by the Intel ACPI
    DSM specification [1], has added support for activating firmware at
    runtime.

    [1]: https://docs.pmem.io/persistent-memory/

The approach taken is to abstract the Intel platform specific mechanism
behind a libnvdimm-generic sysfs interface. The interface could support
runtime-firmware-activation on another architecture without need to
change userspace tooling.

The ACPI NFIT implementation involves a set of device-specific-methods
(DSMs) to 'arm' individual devices for activation and bus-level
'trigger' method to execute the activation. Informational / enumeration
methods are also provided at the bus and device level.

One complicating aspect of the memory device firmware activation is that
the memory controller may need to be quiesced, no memory cycles, during
the activation. While the platform has mechanisms to support holding off
in-flight DMA during the activation, the device response to that delay
is potentially undefined. The platform may reject a runtime firmware
update if, for example a PCI-E device does not support its completion
timeout value being increased to meet the activation time. Outside of
device timeouts the quiesce period may also violate application
timeouts.

Given the above device and application timeout considerations the
implementation defaults to hooking into the suspend path to trigger the
activation, i.e. that a suspend-resume cycle (at least up to the syscore
suspend point) is required. That default policy ensures that the system
is in a quiescent state before ceasing memory controller responses for
the activate. However, if desired, runtime activation without suspend
can be forced as an override.

The ndctl utility grows the following extensions / commands to drive
this mechanism:

1/ The existing update-firmware command will 'arm' devices where the
   firmware image is staged by default.

    ndctl update-firmware all -f firmware_image.bin

2/ The existing ability to enumerate firmware-update capabilities now
   includes firmware activate capabilities at the 'bus' and 'dimm/device'
   level:

    ndctl list -BDF -b nfit_test.0
    [
      {
        "provider":"nfit_test.0",
        "dev":"ndbus2",
        "scrub_state":"idle",
        "firmware":{
          "activate_method":"suspend",
          "activate_state":"idle"
        },
        "dimms":[
          {
            "dev":"nmem1",
            "id":"cdab-0a-07e0-ffffffff",
            "handle":0,
            "phys_id":0,
            "security":"disabled",
            "firmware":{
              "current_version":0,
              "can_update":true
            }
          },
    ...

3/ When the system can support activation without quiesce, or when the
   suspend-resume requirement is going to be suppressed, the new
   activate-firmware command wraps that functionality:

    ndctl activate-firmware nfit_test.0 --force

One major open question for review is how users can trigger
firmware-activation via suspend without doing a full trip through the
BIOS. The activation currently requires CONFIG_PM_DEBUG to enable that
flow. This seems an awkward dependency for something that is expected to
be a production capability.

---

Dan Williams (12):
      libnvdimm: Validate command family indices
      ACPI: NFIT: Move bus_dsm_mask out of generic nvdimm_bus_descriptor
      ACPI: NFIT: Define runtime firmware activation commands
      tools/testing/nvdimm: Cleanup dimm index passing
      tools/testing/nvdimm: Add command debug messages
      tools/testing/nvdimm: Prepare nfit_ctl_test() for ND_CMD_CALL emulation
      tools/testing/nvdimm: Emulate firmware activation commands
      driver-core: Introduce DEVICE_ATTR_ADMIN_{RO,RW}
      libnvdimm: Convert to DEVICE_ATTR_ADMIN_RO()
      libnvdimm: Add runtime firmware activation sysfs interface
      PM, libnvdimm: Add syscore_quiesced() callback for firmware activation
      ACPI: NFIT: Add runtime firmware activate support


 Documentation/ABI/testing/sysfs-bus-nfit           |   35 ++
 Documentation/ABI/testing/sysfs-bus-nvdimm         |    2 
 .../driver-api/nvdimm/firmware-activate.rst        |   74 +++
 drivers/acpi/nfit/core.c                           |  146 +++++--
 drivers/acpi/nfit/intel.c                          |  426 ++++++++++++++++++++
 drivers/acpi/nfit/intel.h                          |   61 +++
 drivers/acpi/nfit/nfit.h                           |   39 ++
 drivers/base/syscore.c                             |   18 +
 drivers/nvdimm/bus.c                               |   46 ++
 drivers/nvdimm/core.c                              |  103 +++++
 drivers/nvdimm/dimm_devs.c                         |   99 +++++
 drivers/nvdimm/namespace_devs.c                    |    2 
 drivers/nvdimm/nd-core.h                           |    1 
 drivers/nvdimm/pfn_devs.c                          |    2 
 drivers/nvdimm/region_devs.c                       |    2 
 include/linux/device.h                             |    4 
 include/linux/libnvdimm.h                          |   53 ++
 include/linux/syscore_ops.h                        |    2 
 include/linux/sysfs.h                              |    7 
 include/uapi/linux/ndctl.h                         |    5 
 kernel/power/suspend.c                             |    2 
 tools/testing/nvdimm/test/nfit.c                   |  367 ++++++++++++++---
 22 files changed, 1382 insertions(+), 114 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-nvdimm
 create mode 100644 Documentation/driver-api/nvdimm/firmware-activate.rst

base-commit: 48778464bb7d346b47157d21ffde2af6b2d39110