Re: [PATCH 1/2] KVM: selftests: Make rseq compatible with glibc-2.35

[Paolo Bonzini]

On 8/10/22 14:29, Mathieu Desnoyers wrote:
> > - By design, selftests/rseq and selftests/kvm are parallel. It's going to
> > introduce
> >    unnecessary dependency for selftests/kvm to use selftests/rseq/librseq.so. To
> >    me,
> >    it makes the maintainability even harder.
> In terms of build system, yes, selftests/rseq and selftests/kvm are side-by-side,
> and I agree it is odd to have a cross-dependency.
>
> That's where moving rseq.c to tools/lib/ makes sense.
>
> > - What selftests/kvm needs is rseq-thread-pointer.h, which accounts for ~5% of
> >    functionalities, provided by selftests/rseq/librseq.so.
> I've never seen this type of argument used to prevent using a library before, except
> on extremely memory-constrained devices, which is not our target here.

I agree.

To me, the main argument against moving librseq to tools/lib is a 
variant of the build-system argument, namely that recursive Make 
sucks[1] and selftests/kvm right now does not use tools/lib.  So, for a 
single-file library, it may be simply not worth the hassle.

On the other hand, if "somebody else" does the work, I would have no 
problem with having selftests/kvm depend on tools/lib, not at all.

Thanks,

Paolo

[1] Kbuild is a marvel that makes it work, but it works because there 
are no such cross-subdirectory dependencies and anyway 
tools/testing/selftests does not use Kbuild.