linux-kernel - Re: [PATCH bpf-next v2 8/9] selftests/bpf: Add selftests for load-acquire and store-release instructions

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Message-ID: <Z7aAmYi5zaVIgRKR@google.com>
Date: Thu, 20 Feb 2025 01:08:41 +0000
From: Peilin Ye <yepeilin@...gle.com>
To: Eduard Zingerman <eddyz87@...il.com>
Cc: bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, bpf@...f.org,
	Xu Kuohai <xukuohai@...weicloud.com>,
	David Vernet <void@...ifault.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	Jonathan Corbet <corbet@....net>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Puranjay Mohan <puranjay@...nel.org>,
	Ilya Leoshkevich <iii@...ux.ibm.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Quentin Monnet <qmo@...nel.org>,
	Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
	Ihor Solodrai <ihor.solodrai@...ux.dev>,
	Yingchi Long <longyingchi24s@....ac.cn>,
	Josh Don <joshdon@...gle.com>, Barret Rhoden <brho@...gle.com>,
	Neel Natu <neelnatu@...gle.com>,
	Benjamin Segall <bsegall@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 8/9] selftests/bpf: Add selftests for
 load-acquire and store-release instructions

On Tue, Feb 11, 2025 at 08:51:07PM +0000, Peilin Ye wrote:
> > > > Nit: why is dummy_test() necessary?
> > > 
> > > It's just to make it clear when these tests are (effectively) skipped.

<...>

> > > Commit 147c8f4470ee ("selftests/bpf: Add unit tests for new
> > > sign-extension load insns") did similar thing in verifier_ldsx.c.
> > 
> > I see, thank you for explaining.
> > We do have a concept of skipped tests in the test-suite,
> > but it is implemented by calling test__skip() from the prog_tests/<smth>.c.
> > This would translate as something like below in prog_tests/verifier.c:
> > 
> > 	void test_verifier_store_release(void) {
> > 	#if defined(ENABLE_ATOMICS_TESTS) && defined(__TARGET_ARCH_arm64)
> > 		RUN(verifier_store_release);
> > 	#else
> > 		test__skip()
> > 	#endif
> > 	}
> 
> > The number of tests skipped is printed after tests execution.

I tried:

  void test_verifier_load_acquire(void)
  {
  #if __clang_major__ >= 18 && defined(ENABLE_ATOMICS_TESTS) && defined(__aarch64__)
          RUN(verifier_load_acquire);
  #else
          printf("%s:SKIP: Clang version < 18, ENABLE_ATOMICS_TESTS not defined, and/or JIT doesn't support load-acquire\n",
                 __func__);
          test__skip();
  #endif
  }

Then realized that I can't check __clang_major__ in .../prog_tests/*
files (e.g. I was building prog_tests/verifier.c using GCC).  I think
ideally we should do something similar to prog{,_test}s/arena_atomics.c,
i.e. use a global bool in BPF source to indicate if we should skip this
test, but that seems to require non-trivial changes to
prog_tests/verifier.c?

For the purpose of this patchset, let me keep dummy_test(), like what we
have now in verifier_ldsx.c.

Thanks,
Peilin Ye