linux-kernel - Re: [PATCH RFC 1/1] mm/ksm: Add recovery mechanism for memory failures

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Message-ID: <077882e3-f69f-44f3-aa74-b325721beb42@linux.dev>
Date: Sat, 11 Oct 2025 17:38:29 +0800
From: Lance Yang <lance.yang@...ux.dev>
To: Miaohe Lin <linmiaohe@...wei.com>
Cc: Longlong Xia <xialonglong2025@....com>, nao.horiguchi@...il.com,
 akpm@...ux-foundation.org, wangkefeng.wang@...wei.com, xu.xin16@....com.cn,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Longlong Xia <xialonglong@...inos.cn>, david@...hat.com
Subject: Re: [PATCH RFC 1/1] mm/ksm: Add recovery mechanism for memory
 failures



On 2025/10/11 17:23, Miaohe Lin wrote:
> On 2025/10/11 15:52, Lance Yang wrote:
>> @Miaohe
>>
>> I'd like to raise a concern about a potential hardware failure :)
> 
> Thanks for your thought.
> 
>>
>> My tests show that if the shared zeropage (or huge zeropage) gets marked
>> with HWpoison, the kernel continues to install it for new mappings.
>> Surprisingly, it does not kill the accessing process ...
> 
> Have you investigated the cause? If user space writes to shared zeropage,
> it will trigger COW and a new page will be installed. After that, reading
> the newly allocated page won't trigger memory error. In this scene, it does
> not kill the accessing process.

Not write just read :)

> 
>>
>> The concern is, once the page is no longer zero-filled due to the hardware
>> failure, what will happen? Would this lead to silent data corruption for
>> applications that expect to read zeros?
> 
> IMHO, once the page is no longer zero-filled due to the hardware failure, later
> any read will trigger memory error and memory_failure should handle that.

I've only tested injecting an error on the shared zeropage using 
corrupt-pfn:

echo $PFN > /sys/kernel/debug/hwpoison/corrupt-pfn

But no memory error was triggered on a subsequent read ...

Anyway, I'm trying to explore other ways to simulate hardware failure :)

Thanks,
Lance