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: <Z6u4O930eIbAVVMZ@google.com>
Date: Tue, 11 Feb 2025 20:51:07 +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>,
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	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>,
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	Jonathan Corbet <corbet@....net>,
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	Puranjay Mohan <puranjay@...nel.org>,
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	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 12:15:25PM -0800, Eduard Zingerman wrote:
> > > Nit: why is dummy_test() necessary?
> > 
> > It's just to make it clear when these tests are (effectively) skipped.
> > Otherwise, e.g. -cpuv4 runner with LLVM-18 on x86-64 would give:
> > 
> >   #518     verifier_load_acquire:OK
> > 
> > With dummy_test(), we would see:
> > 
> > (FWIW, for v3 I'm planning to change __description() to the following,
> > since new tests no longer depend on __BPF_FEATURE_LOAD_ACQ_STORE_REL.)
> > 
> >   #518/1   verifier_load_acquire/Clang version < 18, or JIT does not support load-acquire; use a dummy test:OK
> >   #518     verifier_load_acquire:OK
> > 
> > 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.

Sounds nice!

> Up to you if you'd like to change it like that or not.

I'll do that in v3, thanks for the suggestion.

Peilin Ye