Re: [PATCH] x86/mce: set MCE_IN_KERNEL_COPYIN for all MC-Safe Copy

[Kefeng Wang]

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@xxxxxxxxx>

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
>