ndctl

Utility library for managing the libnvdimm (non-volatile memory device) sub-system in the Linux kernel

Build

meson setup build;
meson compile -C build;

Optionally, to install:

meson install -C build

There are a number of packages required for the build steps that may not be installed by default. For information about the required packages, see the "BuildRequires:" lines in ndctl.spec.in.

https://github.com/pmem/ndctl/blob/master/ndctl.spec.in

Documentation

See the latest documentation for the NVDIMM kernel sub-system here:

https://www.kernel.org/doc/html/latest/driver-api/nvdimm/index.html

A getting started guide is also available on the kernel.org nvdimm wiki:

https://nvdimm.wiki.kernel.org/start

Unit Tests

The unit tests run by meson test require the nfit_test.ko module to be loaded. To build and install nfit_test.ko:

1. Obtain the kernel source. For example,
   git clone -b libnvdimm-for-next git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git

2. Skip to step 3 if the kernel version is >= v4.8. Otherwise, for kernel versions < v4.8, configure the kernel to make some memory available to CMA (contiguous memory allocator). This will be used to emulate DAX.

   CONFIG_DMA_CMA=y
   CONFIG_CMA_SIZE_MBYTES=200
   

   or
   cma=200M on the kernel command line.

3. Compile the libnvdimm sub-system as a module, make sure "zone device" memory is enabled, and enable the btt, pfn, and dax features of the sub-system:

   CONFIG_X86_PMEM_LEGACY=m
   CONFIG_ZONE_DEVICE=y
   CONFIG_LIBNVDIMM=m
   CONFIG_BLK_DEV_PMEM=m
   CONFIG_ND_BLK=m
   CONFIG_BTT=y
   CONFIG_NVDIMM_PFN=y
   CONFIG_NVDIMM_DAX=y
   CONFIG_DEV_DAX_PMEM=m
   CONFIG_ENCRYPTED_KEYS=y
   

4. Build and install the unit test enabled libnvdimm modules in the following order. The unit test modules need to be in place prior to the depmod that runs during the final modules_install

   make M=tools/testing/nvdimm
   sudo make M=tools/testing/nvdimm modules_install
   sudo make modules_install
   

5. Now run meson test -C build in the ndctl source directory, or ndctl test, if ndctl was built with -Dtest=enabled as a configuration option to meson.

6. To run the 'destructive' set of tests that may clobber existing pmem configurations and data, configure meson with the destructive option after the meson setup step:

   meson configure -Dtest=enabled -Ddestructive=enabled build;
   

Troubleshooting

The unit tests will validate that the environment is set up correctly before they try to run. If the platform is misconfigured, i.e. the unit test modules are not available, or the test versions of the modules are superseded by the "in-tree/production" version of the modules meson test will skip tests and report a message like the following in build/meson-logs/testlog.txt

SKIP: libndctl
==============
test/init: nfit_test_init: nfit.ko: appears to be production version: /lib/modules/4.8.8-200.fc24.x86_64/kernel/drivers/acpi/nfit/nfit.ko.xz
__ndctl_test_skip: explicit skip test_libndctl:2684
nfit_test unavailable skipping tests

If the unit test modules are indeed available in the modules 'extra' directory the default depmod policy can be overridden by adding a file to /etc/depmod.d with the following contents:

override nfit * extra
override device_dax * extra
override dax_pmem * extra
override dax_pmem_core * extra
override dax_pmem_compat * extra
override libnvdimm * extra
override nd_btt * extra
override nd_e820 * extra
override nd_pmem * extra

The nfit_test module emulates pmem with memory allocated via vmalloc(). One of the side effects is that this breaks 'physically contiguous' assumptions in the driver. Use the '--align=4K option to 'ndctl create-namespace' to avoid these corner case scenarios.