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Date:   Thu, 5 May 2022 09:21:11 +0800
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Subject: Re: [PATCH -next v4 1/7] x86, powerpc: fix function define in
 copy_mc_to_user
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To:     Tong Tiangen <tongtiangen@huawei.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        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>,
        Michael Ellerman <mpe@ellerman.id.au>,
        "Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>
CC:     Xie XiuQi <xiexiuqi@huawei.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Guohanjun <guohanjun@huawei.com>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>
References: <20220420030418.3189040-1-tongtiangen@huawei.com>
 <20220420030418.3189040-2-tongtiangen@huawei.com>
 <91011a66-b125-b445-1486-bada8e06b994@csgroup.eu>
 <48f2779d-bc62-c7f5-c40e-7238a16b90fb@huawei.com>
From:   Kefeng Wang <wangkefeng.wang@huawei.com>
In-Reply-To: <48f2779d-bc62-c7f5-c40e-7238a16b90fb@huawei.com>
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On 2022/5/3 9:06, Tong Tiangen wrote:
>
>
> 在 2022/5/2 22:24, Christophe Leroy 写道:
>>
>>
>> Le 20/04/2022 à 05:04, Tong Tiangen a écrit :
>>> 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
>>>
>>> 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}()")
>>
>> I don't understand, what does it fix really ? What was the
>> (existing/real) bug introduced by that patch and that your are fixing ?
>>
>> If those defined had been expected and missing, we would have had a
>> build failure. If you have one, can you describe it ?
>
It could prevent future problems when patch3 is introduced， and yes，for 
now，

this patch won't fix any issue，we could drop the fix tag, and update the 
changelog.


> There will be build failure after patch 3 is added, there is a little
> confusing for a reader of this commit in isolation.
> In the next version, I will put this patch after patch 3.
This is an alternative.
>
> Thanks,
> Tong.
> .