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

[Kefeng Wang <wangkefeng.wang@huawei.com>]

Hi x86/mm maintainers, could you pick this up as it has be reviewed
by Naoya and Tony, many thanks.

On 2023/5/8 10:22, Kefeng Wang wrote:
> Both EX_TYPE_FAULT_MCE_SAFE and EX_TYPE_DEFAULT_MCE_SAFE exception
> fixup types are used to identify fixups which allow in kernel #MC
> recovery, that is the Machine Check Safe Copy.
> 
> 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@huawei.com
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>