linux-kernel - Re: [PATCH] x86/mce: set MCE_IN_KERNEL

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Date:   Tue, 23 May 2023 09:34:49 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     "Luck, Tony" <tony.luck@...el.com>, Borislav Petkov <bp@...en8.de>,
        Naoya Horiguchi <naoya.horiguchi@....com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "chu, jane" <jane.chu@...cle.com>
Subject: Re: [PATCH] x86/mce: set MCE_IN_KERNEL_COPYIN for all MC-Safe Copy



On 2023/5/23 2:02, Luck, Tony wrote:
>>> Is this patch in addition to, or instead of, the earlier core dump patch?
>>
>> This is an addition, in previous coredump patch, manually call
>> memory_failure_queue()
>> to be asked to cope with corrupted page, and it is similar to your
>> "Copy-on-write poison recovery"[1], but after some discussion, I think
>> we could add MCE_IN_KERNEL_COPYIN to all MC-safe copy, which will
>> cope with corrupted page in the core do_machine_check() instead of
>> do it one-by-one.
> 
> Thanks for the context. I see how this all fits together now).
> 
> Your patch looks good.
> 
> Reviewed-by: Tony Luck <tony.luck@...el.com>

Thanks for your confirm.

> 
> -Tony
> 
> One small observation from testing. I injected to an application which consumed
> the poisoned data and was sent a SIGBUS.
> 
> Kernel did not crash (hurrah!)

Yes, no crash is always great.

> 
> Console log said:
> 
> [  417.610930] mce: [Hardware Error]: Machine check events logged
> [  417.618372] Memory failure: 0x89167f: recovery action for dirty LRU page: Recovered
> ... EDAC messages
> [  423.666918] MCE: Killing testprog:4770 due to hardware memory corruption fault at 7f8eccf35000
> 
> A core file was generated and saved in /var/lib/systemd/coredump
> 
> But my shell (/bin/bash) only said:
> 
> Bus error
> 
> not
> 
> Bus error (core dumped)

No sure about the effect, but since there is kernel message and mcelog,
it seems that there is no big deal for the different :)

> 
> -Tony
>