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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 15 Nov 2023 11:04:36 -0500
Message-ID: <CAHk-=whTqzkep-RFMcr=S8A2bVx5u_Dgk+f2GXFK-e470jkKjA@mail.gmail.com>
Subject: Re: [PATCH v3 00/10] iov_iter: kunit: Cleanup, abstraction and more tests
To:     David Howells <dhowells@redhat.com>
Cc:     Christian Brauner <christian@brauner.io>,
        Jens Axboe <axboe@kernel.dk>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@lst.de>,
        David Laight <David.Laight@aculab.com>,
        Matthew Wilcox <willy@infradead.org>,
        Brendan Higgins <brendanhiggins@google.com>,
        David Gow <davidgow@google.com>, linux-fsdevel@vger.kernel.org,
        linux-block@vger.kernel.org, linux-mm@kvack.org,
        netdev@vger.kernel.org, linux-kselftest@vger.kernel.org,
        kunit-dev@googlegroups.com, linux-kernel@vger.kernel.org
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On Wed, 15 Nov 2023 at 10:50, David Howells <dhowells@redhat.com> wrote:
>
>  (3) Add a function to set up a userspace VM, attach the VM to the kunit
>      testing thread, create an anonymous file, stuff some pages into the
>      file and map the file into the VM to act as a buffer that can be used
>      with UBUF/IOVEC iterators.
>
>      I map an anonymous file with pages attached rather than using MAP_ANON
>      so that I can check the pages obtained from iov_iter_extract_pages()
>      without worrying about them changing due to swap, migrate, etc..
>
>      [?] Is this the best way to do things?  Mirroring execve, it requires
>      a number of extra core symbols to be exported.  Should this be done in
>      the core code?

Do you really need to do this as a kunit test in the kernel itself?

Why not just make it a user-space test as part of tools/testing/selftests?

That's what it smells like to me. You're doing user-level tests, but
you're doing them in the wrong place, so you need to jump through all
these hoops that you really shouldn't.

                Linus