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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Tong Tiangen <tongtiangen@huawei.com>,
        Mark Rutland <mark.rutland@arm.com>,
        James Morse <james.morse@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Robin Murphy <robin.murphy@arm.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>
Cc:     linuxppc-dev@lists.ozlabs.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Kefeng Wang <wangkefeng.wang@huawei.com>,
        Xie XiuQi <xiexiuqi@huawei.com>,
        Guohanjun <guohanjun@huawei.com>,
        Tong Tiangen <tongtiangen@huawei.com>
Subject: Re: [PATCH -next v4 1/7] x86, powerpc: fix function define in
 copy_mc_to_user
In-Reply-To: <20220420030418.3189040-2-tongtiangen@huawei.com>
References: <20220420030418.3189040-1-tongtiangen@huawei.com>
 <20220420030418.3189040-2-tongtiangen@huawei.com>
Date:   Fri, 22 Apr 2022 19:45:31 +1000
Message-ID: <87r15p8n9g.fsf@mpe.ellerman.id.au>
MIME-Version: 1.0
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Tong Tiangen <tongtiangen@huawei.com> writes:
> x86/powerpc has it's implementation of copy_mc_to_user but not use #define
> to declare.
>
> This may cause problems, for example, if other architectures open
> CONFIG_ARCH_HAS_COPY_MC, but want to use copy_mc_to_user() outside the
> architecture, the code add to include/linux/uaddess.h is as follows:
>
>     #ifndef copy_mc_to_user
>     static inline unsigned long __must_check
>     copy_mc_to_user(void *dst, const void *src, size_t cnt)
>     {
> 	    ...
>     }
>     #endif
     
The above doesn't exist yet, you add it in patch 3, which is a little
confusing for a reader of this commit in isolation.

I think you could safely move that into this patch, and then this patch
would be ~= "Add generic fallback version of copy_mc_to_user()".

It's probably not worth doing a whole new version of the series just for
that, but if you need to do a new version for some other reason I think
it would be cleaner to introduce the fallback in this commit.

> Then this definition will conflict with the implementation of x86/powerpc
> and cause compilation errors as follow:
>
> Fixes: ec6347bb4339 ("x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}()")
> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
> ---
>  arch/powerpc/include/asm/uaccess.h | 1 +

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers