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

[Kefeng Wang]

On 2023/5/20 0:17, Luck, Tony wrote:
> > For now, the MCE_IN_KERNEL_COPYIN flag is only set for EX_TYPE_COPY
> > and EX_TYPE_UACCESS when copy from user, and corrupted page is
> > isolated in this case, for MC-safe copy, memory_failure() is not
> > always called, some places, like __wp_page_copy_user, copy_subpage,
> > copy_user_gigantic_page and ksm_might_need_to_copy manually call
> > memory_failure_queue() to cope with such unhandled error pages,
> > recently coredump hwposion recovery support[1] is asked to do the
> > same thing, and there are some other already existed MC-safe copy
> > scenarios, eg, nvdimm, dm-writecache, dax, which has similar issue.
> >
> > The best way to fix them is set MCE_IN_KERNEL_COPYIN to MCE_SAFE
> > exception, then kill_me_never() will be queued to call memory_failure()
> > in do_machine_check() to isolate corrupted page, which avoid calling
> > memory_failure_queue() after every MC-safe copy return.
> >
> > [1] https://lkml.kernel.org/r/20230417045323.11054-1-wangkefeng.wang@xxxxxxxxxx
>
> 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.

The related patch is
normal page CoW [1]
huge page CoW [2]
coredump [3]
ksm might copy [4]

[1] d302c2398ba2 ("mm, hwpoison: when copy-on-write hits poison, take 
page offline")
a873dfe1032a ("mm, hwpoison: try to recover from copy-on write faults")

[2] 1cb9dc4b475c ("mm: hwpoison: support recovery from HugePage 
copy-on-write faults")

[3] 245f09226893 ("mm: hwpoison: coredump: support recovery from 
dump_user_range()")

[4] 6b970599e807 ("mm: hwpoison: support recovery from 
ksm_might_need_to_copy()")

All of them are in v6.4-rc1.

Thanks.
Kefeng

> I'd like to run some tests. Can you point me a the precise set of patches
> that I should apply please?
>
> -Tony
>