On Wed, Jan 25, 2023, Yu Zhang wrote: > Hi all, > > Currently, unlike the build system of Linux kernel, KVM selftests will > have to run "make clean && make" to rebuild the entire test suite, once > a header file is modified. > > Is it designed like this on purpose, My #1 rule: never assume anything weird in KVM was an explicit design choice :-) > or does anyone wanna change it? Yes! > I hacked the makefile by using "-MD" as EXTRA_CFLAGS, so that dependency > rules can be generated for each target object, whose prerequisites contains > the source file and the included header files as well. > > However, this change has its own costs. E.g., new ".o" and ".d" files will > occupy more storage. And performance-wise, the benifit could be limited, > because for now, most header files are needed by almost every ".c" files. > But with the evolution of KVM selftests, more ".h" files may be added. Some > of which may be of special usage. E.g., file "include/x86_64/mce.h" is only > used by "x86_64/ucna_injection_test". Having to rebuild the whole test suite > just because one specific header is touched would be annoying. > > I am not sure if this change is worthy, Absolutely worthy, I've run afoul of the lack of dependency tracking far too many times. > or if there's a better solution. This part I don't know. I would have cobbled together something long ago if I wasn't so clueless about Makefiles.
