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authorDan Williams <dan.j.williams@intel.com>2015-06-17 17:23:32 -0400
committerDan Williams <dan.j.williams@intel.com>2015-06-26 11:23:38 -0400
commit6bc756193ff61bf5e7b3cfedfbb0873bf40f8055 (patch)
tree5b17fac71bf9989eb2f5ab4ff10e3c6fc01a3cbf /tools/testing/nvdimm/Makefile
parentlibnvdimm, nfit, nd_blk: driver for BLK-mode access persistent memory (diff)
downloadlinux-dev-6bc756193ff61bf5e7b3cfedfbb0873bf40f8055.tar.xz
linux-dev-6bc756193ff61bf5e7b3cfedfbb0873bf40f8055.zip
tools/testing/nvdimm: libnvdimm unit test infrastructure
'libnvdimm' is the first driver sub-system in the kernel to implement mocking for unit test coverage. The nfit_test module gets built as an external module and arranges for external module replacements of nfit, libnvdimm, nd_pmem, and nd_blk. These replacements use the linker --wrap option to redirect calls to ioremap() + request_mem_region() to custom defined unit test resources. The end result is a fully functional nvdimm_bus, as far as userspace is concerned, but with the capability to perform otherwise destructive tests on emulated resources. Q: Why not use QEMU for this emulation? QEMU is not suitable for unit testing. QEMU's role is to faithfully emulate the platform. A unit test's role is to unfaithfully implement the platform with the goal of triggering bugs in the corners of the sub-system implementation. As bugs are discovered in platforms, or the sub-system itself, the unit tests are extended to backstop a fix with a reproducer unit test. Another problem with QEMU is that it would require coordination of 3 software projects instead of 2 (kernel + libndctl [1]) to maintain and execute the tests. The chances for bit rot and the difficulty of getting the tests running goes up non-linearly the more components involved. Q: Why submit this to the kernel tree instead of external modules in libndctl? Simple, to alleviate the same risk that out-of-tree external modules face. Updates to drivers/nvdimm/ can be immediately evaluated to see if they have any impact on tools/testing/nvdimm/. Q: What are the negative implications of merging this? It is a unique maintenance burden because the purpose of mocking an interface to enable a unit test is to purposefully short circuit the semantics of a routine to enable testing. For example __wrap_ioremap_cache() fakes the pmem driver into "ioremap()'ing" a test resource buffer allocated by dma_alloc_coherent(). The future maintenance burden hits when someone changes the semantics of ioremap_cache() and wonders what the implications are for the unit test. [1]: https://github.com/pmem/ndctl Cc: <linux-acpi@vger.kernel.org> Cc: Lv Zheng <lv.zheng@intel.com> Cc: Robert Moore <robert.moore@intel.com> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'tools/testing/nvdimm/Makefile')
-rw-r--r--tools/testing/nvdimm/Makefile7
1 files changed, 7 insertions, 0 deletions
diff --git a/tools/testing/nvdimm/Makefile b/tools/testing/nvdimm/Makefile
new file mode 100644
index 000000000000..3dfe024b4e7e
--- /dev/null
+++ b/tools/testing/nvdimm/Makefile
@@ -0,0 +1,7 @@
+KDIR ?= ../../../
+
+default:
+ $(MAKE) -C $(KDIR) M=$$PWD
+
+install: default
+ $(MAKE) -C $(KDIR) M=$$PWD modules_install