From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3E77E3E16A9; Tue, 25 Aug 2026 14:18:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787667485; cv=none; b=syCnZfQ1+6nFKjCYq3DAtoH1iTuIlfVpQsALFvwUcQS0dW5sYDrkTRzTgBxuXw1kmMv95ccbg/p1jHXX+H4gfOx8rB/i3JvpAqh0Src9WqNOT82agxTzgKBADCUjDHo22G0s4FjlAgZk2hbpfGJ0HqInYEgxrH/0243erNMVjZA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787667485; c=relaxed/simple; bh=IVo46GOYksHu59bUk9yX/+ss/yJkSBpPFWwNe27FDUE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=nzzZdAWs2iAE5d6x+sqBDNoiam9ZnjAPyHmaSIj52fNnlTByBUyLA/sLmEX1Z5yPED8NBQNgzMGZ8oE5kGufblioV919jb5HwxB+vZqOYHJSZlm5qXpGmXmGAgEUG1rD+QXS887GEL+gbrpszbGuq2DOfxTXyWM1TsLadaDvYdk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lfQk7Wo+; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lfQk7Wo+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 435CE1F000E9; Tue, 25 Aug 2026 14:17:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787667483; bh=2m/dMXURvfpZ+cPx67e5HrKltzCqk468e+Tkq0xJoQg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=lfQk7Wo+tK5nk8tvFV0CZEzaOaUWM0Mh5YDkbrjWjVtjWhscI8MJLS69M66Tu25+a fbJEvOx8MgNAOlBOV+/XzLdLYLOm3bGxv+0UFbSn//FLHk6OZFFWwORKtxsSPjph3p 56VPgcJdJEi0UCoXC9842wvmIUVLsUc2/TlQJdpmNlKtpcDtY95C2CVN+SpwRASPfn ehFjBG71Vba1XgoS1PYhTKruDwglLDrDex7LLOjTgUcPx0m5DamkjvIUYluCGZSpSe bCwSD+1o9q2j0krEMh/rK7dQOAknp7cPXejiW0OnXXeUdbOGLRKU3hG3cnucfQJd19 7iFwxKMG5mQfA== Message-ID: Date: Tue, 25 Aug 2026 16:17:54 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/2] support kselftest on nommu platform To: "Lorenzo Stoakes (ARM)" Cc: Hajime Tazaki , linux-mm@kvack.org, liam@infradead.org, rbm@suse.com, akpm@linux-foundation.org, luto@amacapital.net, brendan.jackman@linux.dev, liuhangbin@gmail.com, corbet@lwn.net, kees@kernel.org, broonie@kernel.org, mhocko@suse.com, rppt@kernel.org, shuah@kernel.org, surenb@google.com, vbabka@kernel.org, wad@chromium.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-um@lists.infradead.org, geert@linux-m68k.org, daniel@thingy.jp References: <20260825015945.141739-1-thehajime@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/25/26 15:12, Lorenzo Stoakes (ARM) wrote: > On Tue, Aug 25, 2026 at 10:37:41AM +0200, David Hildenbrand (Arm) wrote: >> On 8/25/26 03:59, Hajime Tazaki wrote: >>> We add an ability to execute kselftest on nommu platforms. >>> >>> Currently there are several issues if we wish to run kselftests on nommu >>> targets: >>> >>> - it cannot compile/build test binaries because the current files mainly >>> assume to build with glibc, >>> - some of the tests are not able to run on nommu targets as there are no >>> fork(2) syscall. >>> >>> The first issue can be avoided if we can build static PIE binaries (if >>> targets support it), but in our case (build on ubuntu/glibc and run on >>> alpine/musl-libc), it fails to invoke due to lack of the GNU ifunc >>> mechanism. Thus, we need to cross-compile with musl toolchain, which >>> needs to be solved the first issue. >>> >>> The second issue is the lack of fork(2) syscall on those platforms. >>> Especially the test harness helper (kselftest_harness.h) uses the >>> syscall, which cannot be simply with vfork(2). `timeout` command used >>> in `runner.sh` never works for nommu platform as it uses fork(2). >>> >>> nommu component in the mm subsystem has several known issues and having >>> test cases should help this situation, thus this patchset is very first >>> step toward enriching test environment which has not been well tested >>> for a while. The test cases is implemented based on the document >>> (Documentation/admin-guide/mm/nommu-mmap.rst). >>> >>> So, for the first step, nommu targets only support low-level API of >>> kselftests (kselftest.h), and implement tests in a new target, >>> TARGETS=mm/nommu. Other targets are currently not even able to build >>> due to toolchain issues but will be addressed once the initial >>> introduction which mainly focuses on nommu test will be settled. >>> >>> The patch was initially combined with other patches but is decoupled to >>> only focus on test framework and testcases. >>> >>> - rfc: >>> https://lore.kernel.org/linux-mm/20260813063401.1786548-1-thehajime@gmail.com/ >>> >>> Hajime Tazaki (2): >>> selftests: run tests on nommu architecture >>> selftests/mm: add nommu mmap and mremap behavior tests >>> >>> Documentation/dev-tools/kselftest.rst | 14 + >>> tools/testing/selftests/Makefile | 1 + >>> tools/testing/selftests/kselftest/runner.sh | 9 +- >>> tools/testing/selftests/kselftest_harness.h | 4 + >>> tools/testing/selftests/lib.mk | 8 + >>> tools/testing/selftests/mm/nommu/Makefile | 7 + >>> .../selftests/mm/nommu/nommu_mmap_test.c | 265 +++++++++++++ >>> .../selftests/mm/nommu/nommu_mremap_test.c | 353 ++++++++++++++++++ >> >> That's odd. >> >> tools/testing/selftests/mm >> >> itself should know which tests can be built and ran on nommu. nommu-only tests >> can be placed in mm/nommu, but I would expect tools/testing/selftests/mm's >> Makefile and run script to compile and run only selftests that are supported on >> the given platform. > > I mean I think at this point with mm/nommu/nommu_xxx.c it'd make more sense to > simply have selftests/nommu/ + update the mm makefile to not build stuff that's > broken on nommu there. > > That way positively nommu-stuff is put in its own place and what's broken on mm > specific to nommu can be fixed there. > > I'd rather isolate them clearly rather than having them live in a subdirectory > of mm. My understanding is that some MM tests could be enabled/changed in the future that support both MMU and NOMMU. Not sure how to best handle that. So wiring up mm/nommu as a separate thing did sound wrong to me. So it should either be integrated or the tests in fact completely moved out of mm/ -- Cheers, David