linux-kernel - Re: [PATCH] mm/memory-failure: teach kill_accessing

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Message-ID: <d441011b-fe8e-46d3-a67b-6971a380b3cd@oracle.com>
Date: Mon, 22 Dec 2025 10:42:02 -0800
From: jane.chu@...cle.com
To: "David Hildenbrand (Red Hat)" <david@...nel.org>, muchun.song@...ux.dev,
        osalvador@...e.de, linmiaohe@...wei.com, jiaqiyan@...gle.com,
        william.roche@...cle.com, rientjes@...gle.com,
        akpm@...ux-foundation.org, lorenzo.stoakes@...cle.com,
        Liam.Howlett@...cle.com, rppt@...nel.org, surenb@...gle.com,
        mhocko@...e.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/memory-failure: teach kill_accessing_process to accept
 hugetlb tail page pfn


On 12/21/2025 12:49 AM, David Hildenbrand (Red Hat) wrote:
> On 12/19/25 07:28, Jane Chu wrote:
>> When a hugetlb folio is being poisoned again, 
>> try_memory_failure_hugetlb()
>> passed head pfn to kill_accessing_process(), that is not right.
>> The precise pfn of the poisoned page should be used in order to
>> determine the precise vaddr as the SIGBUS payload.
> 
> I don't think so? IIRC, for hugetlb folios we always reported the head 
> PFN. And user space must assume that the whole thing is poisoned and 
> will go away.
> 
> I recall that older QEMU even depended on that behavior, for example.
> 

What happens if non-head PFN of hugetlb is indicated in a SIGBUG to 
QEMU?  Because, the regular path, the path via hwpoison_user_mappings() 
already behave this way.

I'm not familiar with QEMU. AFAIK, the need for this patch came from our 
VM/QEMU team.

thanks,
-jane