Re: [PATCH v5 00/15] kunit: Introduce UAPI testing framework

[Christoph Hellwig <hch@lst.de>]

On Thu, Jul 17, 2025 at 10:48:02AM +0200, Thomas Weißschuh wrote:
> Currently testing of userspace and in-kernel API use two different
> frameworks.

Which is kinda expected as one has to run in the kernel to test
in-kernel kernel space APIs, and the other tests externally provided
kernel functionality.

> Therefore kunit is much easier to run against different kernel
> configurations and architectures.

Which is is normal.  unit tests are always easier to run than
integration tests.

> This series aims to combine kselftests and kunit, avoiding both their
> limitations. It works by compiling the userspace kselftests as part of
> the regular kernel build, embedding them into the kunit kernel or module
> and executing them from there.

This is really weird.  "Running userspace code is hard, so we package
it in the kernel".  I had my own fair share of problems with kselftests,
mostly because of the lack of structure and automated way to run them,
but adding them to the kernel (or a module) is overshooting the target
by far.

> If the kernel toolchain is not fit to
> produce userspace because of a missing libc, the kernel's own nolibc can
> be used instead.

Is nolibc enough to run all the selftests?  If so we should just do
it unconditionally, but linking to different libraries by availability
seems a bit problematic.

> The structured TAP output from the kselftest is integrated into the
> kunit KTAP output transparently, the kunit parser can parse the combined
> logs together.

Good idea!