linux-kernel - Re: [PATCH v2] mm: hwpoison: coredump: support recovery from dump_user

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Date:   Tue, 25 Apr 2023 09:47:22 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     "Luck, Tony" <tony.luck@...el.com>,
        HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>
CC:     "chu, jane" <jane.chu@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Tong Tiangen <tongtiangen@...wei.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH v2] mm: hwpoison: coredump: support recovery from
 dump_user_range()



On 2023/4/25 0:17, Luck, Tony wrote:
>>> This change seems to not related to what you try to fix.
>>> Could this break some other workloads like copying from user address?
>>>
>>
>> Yes, this move MCE_IN_KERNEL_COPYIN set into next case, both COPY and
>> MCE_SAFE type will set MCE_IN_KERNEL_COPYIN, for EX_TYPE_COPY, we don't
>> break it.
> 
> Should Linux even try to take a core dump for a SIGBUS generated because
> the application accessed a poisoned page?
> 
> It doesn't seem like it would be useful. Core dumps are for debugging s/w
> program errors in applications and libraries. That isn't the case when there
> is a poison consumption. The application did nothing wrong.
> 
> This patch is still useful though. There may be an undiscovered poison
> page in the application. Avoiding a kernel crash when dumping core
> is still a good thing.

Thanks for your confirm, and what your option about add
MCE_IN_KERNEL_COPYIN to EX_TYPE_DEFAULT_MCE_SAFE/FAULT_MCE_SAFE type
to let do_machine_check call queue_task_work(&m, msg, kill_me_never),
which kill every call memory_failure_queue() after mc safe copy return?

> 
> -Tony