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Subject: Re: [PATCH 0/4] Fix kselftest build with sub-directory
To:     Guillaume Tucker <guillaume.tucker@collabora.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Shuah Khan <shuah@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
        Anders Roxell <anders.roxell@linaro.org>
Cc:     kernel@collabora.com, linux-kbuild@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        Shuah Khan <skhan@linuxfoundation.org>
References: <cover.1657296695.git.guillaume.tucker@collabora.com>
From:   Shuah Khan <skhan@linuxfoundation.org>
Message-ID: <b39b9e0b-45f3-1818-39fe-58921182d957@linuxfoundation.org>
Date:   Fri, 8 Jul 2022 11:14:32 -0600
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On 7/8/22 10:23 AM, Guillaume Tucker wrote:
> Earlier attempts to get "make O=build kselftest-all" to work were
> not successful as they made undesirable changes to some functions
> in the top-level Makefile.  This series takes a different
> approach by removing the root cause of the problem within
> kselftest, which is when the sub-Makefile tries to install kernel
> headers "backwards" by calling make with the top-level Makefile.
> The actual issue comes from the fact that $(srctree) is ".." when
> building in a sub-directory with "O=build" which then obviously
> makes "-C $(top_srcdir)" point outside of the real source tree.
> 
> With this series, the generic kselftest targets work as expected
> from the top level with or without a build directory e.g.:
> 
>    $ make kselftest-all
> 
>    $ make O=build kselftest-all
> 
> Then in order to build using the sub-Makefile explicitly, the
> headers have to be installed first.  This is arguably a valid
> requirement to have when building a tool from a sub-Makefile.
> For example, "make -C tools/testing/nvdimm/" fails in a similar
> way until <asm/rwonce.h> has been generated by a kernel build.
> 
> Guillaume Tucker (4):
>    selftests: drop khdr make target
>    selftests: stop using KSFT_KHDR_INSTALL
>    selftests: drop KSFT_KHDR_INSTALL make target
>    Makefile: add headers_install to kselftest targets
> 

This takes us to back to the state before b2d35fa5fc80 added
khdr support. I reluctantly agreed to the change and it has
proven to be a problematic change. I would rather have had the
dependency stated that headers should be installed prior to
building tests - test build depends on kernel build anyway and
having dependency on headers having build isn't a huge deal.

So I am in favor of getting rid of khdr support. However, this
khdr support was a change originated from Linaro test ring. Undoing
this might have implication on their workflow.

I will pull them into the discussion so they are aware of it and
be prepared for this change.

thanks,
-- Shuah