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
