linux-kernel - Re: [PATCH v3] LoongArch: Fixup do_ri csr

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Message-ID: <5bf565a4-5bc4-42f8-59c0-8b908a9c2ab6@loongson.cn>
Date:   Tue, 27 Sep 2022 11:10:30 +0800
From:   Jun Yi <yijun@...ngson.cn>
To:     Guo Ren <guoren@...nel.org>
Cc:     Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Qing Zhang <zhangqing@...ngson.cn>,
        Mao Bibo <maobibo@...ngson.cn>,
        Jianmin Lv <lvjianmin@...ngson.cn>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] LoongArch: Fixup do_ri csr_era

do_ri is porting from mips, mipsr6 use do_ri to emulate some fp 
instructions, but Loongarch do not need to emulate these instructions.

And the regs->csr_era be always recovered to ths old_era = 
regs->csr_era, so the compute_return_era is useless.

On 9/27/22 07:41, Guo Ren wrote:
> On Mon, Sep 26, 2022 at 8:27 PM Jun Yi <yijun@...ngson.cn> wrote:
>>
>> csr_era of pt_regs in do_ri should not add 4 to point to the
>> next instruction.
> The comment does not make sense. I think it wants to skip some
> instructions, but your patch broke that.
> 
>>
>> Signed-off-by: Jun Yi <yijun@...ngson.cn>
>> ---
>>   arch/loongarch/kernel/traps.c | 2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
>> index aa1c95aaf595..ec888eda3d45 100644
>> --- a/arch/loongarch/kernel/traps.c
>> +++ b/arch/loongarch/kernel/traps.c
>> @@ -477,8 +477,6 @@ asmlinkage void noinstr do_ri(struct pt_regs *regs)
>>
>>          die_if_kernel("Reserved instruction in kernel code", regs);
>>
>> -       compute_return_era(regs);
>> -
>>          if (unlikely(get_user(opcode, era) < 0)) {
>>                  status = SIGSEGV;
>>                  current->thread.error_code = 1;
>> --
>> 2.31.1
>>
> 
>