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

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Date:   Mon, 22 May 2023 18:02:29 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.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

>> 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>

-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!)

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)

-Tony