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

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Date:   Mon, 8 May 2023 05:47:36 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
CC:     Tony Luck <tony.luck@...el.com>, Borislav Petkov <bp@...en8.de>,
        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>,
        "jane.chu@...cle.com" <jane.chu@...cle.com>
Subject: Re: [PATCH] x86/mce: set MCE_IN_KERNEL_COPYIN for all MC-Safe Copy

On Mon, May 08, 2023 at 10:22:33AM +0800, 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@...wei.com>

Looks good to me, thank you.

Reviewed-by: Naoya Horiguchi <naoya.horiguchi@....com>