linux-kernel - Re: [PATCH] arm64: kcsan: Fix kcsan test

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Message-ID: <4c8acff0-38c5-4a4e-e216-c5252259b1f8@huawei.com>
Date:   Tue, 26 Apr 2022 23:13:27 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Marco Elver <elver@...gle.com>
CC:     <catalin.marinas@....com>, <will@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <mark.rutland@....com>
Subject: Re: [PATCH] arm64: kcsan: Fix kcsan test_barrier fail and panic


On 2022/4/26 20:10, Marco Elver wrote:
> On Tue, Apr 26, 2022 at 08:17AM +0000, Kefeng Wang wrote:
>> As "kcsan: Support detecting a subset of missing memory barriers"
>> introduced KCSAN_STRICT which make kcsan detects more missing memory
>> barrier, but arm64 don't have KCSAN instrumentation for barriers, so
>> the new selftest test_barrier() will fail, then panic.
> Thanks for fixing this - did kcsan_test module pass as well?

Yes， selftest and kcsan_test  passed with gcc11 & clang 14.

...

>> +#ifdef __dma_mb
>> +#define dma_mb()	do { kcsan_mb(); __dma_mb(); } while (0)
>> +#endif
>> +
> So it looks like arm64 is the only arch that defines dma_mb(). By adding
> it to asm-generic, we'd almost be encouraging other architectures to add
> it, which I don't know we want.
>
> Documentation/memory-barriers.txt doesn't mention dma_mb() either - so
> perhaps dma_mb() doesn't belong in asm-generic/barrier.h, and you could
> only change arm64's definition of dma_mb() to add the kcsan_mb().
>
> Preferences? Maybe arch64 maintainers have more background on why arm64
> is an anomaly here.
> .
Let's wait to see aarch64 maintainers's suggestion.