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6bc756193f
'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> |
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.. | ||
acpica | ||
apei | ||
pmic | ||
ac.c | ||
acpi_apd.c | ||
acpi_cmos_rtc.c | ||
acpi_extlog.c | ||
acpi_ipmi.c | ||
acpi_lpat.c | ||
acpi_lpss.c | ||
acpi_memhotplug.c | ||
acpi_pad.c | ||
acpi_platform.c | ||
acpi_pnp.c | ||
acpi_processor.c | ||
battery.c | ||
battery.h | ||
bgrt.c | ||
blacklist.c | ||
bus.c | ||
button.c | ||
cm_sbs.c | ||
container.c | ||
custom_method.c | ||
debugfs.c | ||
device_pm.c | ||
dock.c | ||
ec.c | ||
ec_sys.c | ||
event.c | ||
fan.c | ||
glue.c | ||
gsi.c | ||
hed.c | ||
int340x_thermal.c | ||
internal.h | ||
ioapic.c | ||
Kconfig | ||
Makefile | ||
nfit.c | ||
nfit.h | ||
numa.c | ||
nvs.c | ||
osl.c | ||
pci_irq.c | ||
pci_link.c | ||
pci_root.c | ||
pci_slot.c | ||
power.c | ||
proc.c | ||
processor_core.c | ||
processor_driver.c | ||
processor_idle.c | ||
processor_pdc.c | ||
processor_perflib.c | ||
processor_thermal.c | ||
processor_throttling.c | ||
property.c | ||
reboot.c | ||
resource.c | ||
sbs.c | ||
sbshc.c | ||
sbshc.h | ||
scan.c | ||
sleep.c | ||
sleep.h | ||
sysfs.c | ||
tables.c | ||
thermal.c | ||
utils.c | ||
video.c | ||
video_detect.c | ||
wakeup.c |