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Subject: Re: [PATCH -next] mm: hwpoison: support recovery from HugePage
 copy-on-write faults
To:     Andrew Morton <akpm@linux-foundation.org>,
        Mike Kravetz <mike.kravetz@oracle.com>
References: <20230411092741.780679-1-liushixin2@huawei.com>
 <20230412181350.GA22818@monkey>
 <20230412145718.0bcb7dd98112a3010711ad0b@linux-foundation.org>
 <20230412222138.GB4759@monkey>
 <20230412155618.720e6b3aa5be6444f7889ea6@linux-foundation.org>
CC:     Naoya Horiguchi <naoya.horiguchi@nec.com>,
        Tony Luck <tony.luck@intel.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Muchun Song <muchun.song@linux.dev>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>
From:   Liu Shixin <liushixin2@huawei.com>
Message-ID: <5202b6fe-7008-6e1b-eaae-03edbe7c055c@huawei.com>
Date:   Thu, 13 Apr 2023 09:55:32 +0800
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On 2023/4/13 6:56, Andrew Morton wrote:
> On Wed, 12 Apr 2023 15:21:38 -0700 Mike Kravetz <mike.kravetz@oracle.com> wrote:
>
>>>> Commit a873dfe1032a ("mm, hwpoison: try to recover from copy-on write
>>>> faults") introduced the routine copy_user_highpage_mc() to gracefully
>>>> handle copying of user pages with uncorrectable errors.  Previously,
>>>> such copies would result in a kernel crash.  hugetlb has separate code
>>>> paths for copy-on-write and does not benefit from the changes made in
>>>> commit a873dfe1032a.
>> I was just going to suggest adding the line,
>>
>> Hence, copy-on-write of hugetlb user pages with uncorrectable errors            
>> will result in a kernel crash as was the case with 'normal' pages before        
>> commit a873dfe1032a.
>>
>> However, I'm guessing it might be more clear if we start with the
>> runtime effects.  Something like:
>>
>> copy-on-write of hugetlb user pages with uncorrectable errors will result
>> in a kernel crash.  This is because the copy is performed in kernel mode
>> and in general we can not handle accessing memory with such errors while
>> in kernel mode.  Commit a873dfe1032a ("mm, hwpoison: try to recover from
>> copy-on write faults") introduced the routine copy_user_highpage_mc() to
>> gracefully handle copying of user pages with uncorrectable errors.  However,
>> the separate hugetlb copy-on-write code paths were not modified as part
>> of commit a873dfe1032a.
> Sounds good.  So I assume cc:stable is desirable.
>
> I can't actually get the patch to apply to anything.  Can we please
> have a redo against current -linus?
OK, I will apply this patch to mainline again.
>
> .
>