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Date:   Sat, 27 Aug 2022 18:43:06 +0800
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Subject: Re: [PATCH -next v2 1/2] riscv: uaccess: rename
 __get/put_user_nocheck to __get/put_mem_nocheck
To:     Arnd Bergmann <arnd@arndb.de>
CC:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Palmer Dabbelt <palmer@rivosinc.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        <Conor.Dooley@microchip.com>, <linux-riscv@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <wangkefeng.wang@huawei.com>,
        Guohanjun <guohanjun@huawei.com>
References: <20220815032025.2685516-1-tongtiangen@huawei.com>
 <20220815032025.2685516-2-tongtiangen@huawei.com>
 <CAK8P3a0ixaYimjCh77QBJpbHbVsw+9C7RiW2LEnwQ8HnwG_jHg@mail.gmail.com>
From:   Tong Tiangen <tongtiangen@huawei.com>
In-Reply-To: <CAK8P3a0ixaYimjCh77QBJpbHbVsw+9C7RiW2LEnwQ8HnwG_jHg@mail.gmail.com>
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在 2022/8/26 17:30, Arnd Bergmann 写道:
> On Mon, Aug 15, 2022 at 5:20 AM Tong Tiangen <tongtiangen@huawei.com> wrote:
>>
>> Current, The helpers __get/put_user_nocheck() is used by get/put_user() and
>> __get/put_kernel_nofault(), which is not always uaccess, so the name with
>> *user* is not appropriate.
>>
>> Also rename xxx_user_xxx to xxx_mem_xx  on the call path of
>> __get/put_user_nocheck()
>>
>> Only refactor code without any functional changes.
>>
>> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
> 
> I would prefer this not being done, it just makes riscv diverge from the
> code on other architectures. While the new name does make more sense,
> it ends up making it harder to refactor this across architectures in the end.
> 
> There are two important cleanups that I would like to see done in
> asm/uaccess.h across architectures:
> 
>   - generalize the __get_user()/__put_user()/__get_kernel_nofault()/
>    __put_kernel_nofault() wrappers to the point that architectures do not
>    need to worry about the variable type stuff but instead just provide
>    trivial fixed-length helpers of some sort
> 
> - change the calling conventions in a way that allows the use of the
>    asm-goto-with-output method for better object code on modern
>    compilers.
> 
> The x86 version already has most of this, with their
> __get_user_size() macro supporting both the asm-goto label
> and the error code assignment, so the generalized code should
> probably be based on that approach.

I am very interested in the implementation of X86. I need to investigate 
and consider a cross architecture implementation.
However, I understand that the modification of the current patch has 
little to do with the two points mentioned above. We can optimize the 
code step by step.

Thanks,
Tong.

> 
>         Arnd
> 
> .