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Date:   Sun, 24 Apr 2022 09:16:05 +0800
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Subject: Re: [PATCH -next v4 1/7] x86, powerpc: fix function define in
 copy_mc_to_user
To:     Michael Ellerman <mpe@ellerman.id.au>,
        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>
References: <20220420030418.3189040-1-tongtiangen@huawei.com>
 <20220420030418.3189040-2-tongtiangen@huawei.com>
 <87r15p8n9g.fsf@mpe.ellerman.id.au>
From:   Tong Tiangen <tongtiangen@huawei.com>
In-Reply-To: <87r15p8n9g.fsf@mpe.ellerman.id.au>
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在 2022/4/22 17:45, Michael Ellerman 写道:
> 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.
> 

Agreed, will do in next version.

Thanks,
Tong.

>> 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
> .