linux-kernel - Re: [RFC PATCH -next V3 4/6] arm64: add copy_{to, from}

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Date:   Wed, 13 Apr 2022 15:30:38 +0800
From:   Tong Tiangen <tongtiangen@...wei.com>
To:     Robin Murphy <robin.murphy@....com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>, <x86@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Xie XiuQi <xiexiuqi@...wei.com>
Subject: Re: [RFC PATCH -next V3 4/6] arm64: add copy_{to, from}_user to
 machine check safe



在 2022/4/13 1:08, Robin Murphy 写道:
> On 12/04/2022 8:25 am, Tong Tiangen wrote:
> [...]
>> diff --git a/arch/arm64/include/asm/asm-uaccess.h 
>> b/arch/arm64/include/asm/asm-uaccess.h
>> index 0557af834e03..bb17f0829042 100644
>> --- a/arch/arm64/include/asm/asm-uaccess.h
>> +++ b/arch/arm64/include/asm/asm-uaccess.h
>> @@ -92,4 +92,20 @@ alternative_else_nop_endif
>>           _asm_extable    8888b,\l;
>>       .endm
>> +
>> +    .macro user_ldp_mc l, reg1, reg2, addr, post_inc
>> +8888:        ldtr    \reg1, [\addr];
>> +8889:        ldtr    \reg2, [\addr, #8];
>> +        add    \addr, \addr, \post_inc;
>> +
>> +        _asm_extable_uaccess_mc    8888b, \l;
>> +        _asm_extable_uaccess_mc    8889b, \l;
>> +    .endm
> 
> You're replacing the only user of this, so please just 
> s/_asm_extable/_asm_extable_uaccess_mc/ in the existing macro and save 
> the rest of the churn.
> 
> Furthermore, how come you're not similarly updating user_stp, given that 
> you *are* updating the other stores in copy_to_user?

I think all load/store instructions should be handled.

Generally speaking, the load operation will receive a sea when consuming 
a hardware memory error, and the store operation will not receive a sea 
when consuming a hardware error. Depends on chip behavior.

So add store class instructions to processed is no harm.

If there is any problem with my understanding, correct me.

Thanks,
Tong.

> 
>> +
>> +    .macro user_ldst_mc l, inst, reg, addr, post_inc
>> +8888:        \inst        \reg, [\addr];
>> +        add        \addr, \addr, \post_inc;
>> +
>> +        _asm_extable_uaccess_mc    8888b, \l;
>> +    .endm
>
[...]