Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <c5107413-3714-8aef-fa24-c0f46d705d68@huawei.com>
Date:   Wed, 24 May 2023 19:23:33 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.10.1
Subject: Re: [PATCH] x86/mce: set MCE_IN_KERNEL_COPYIN for all MC-Safe Copy
Content-Language: en-US
To:     Tony Luck <tony.luck@intel.com>, Borislav Petkov <bp@alien8.de>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>
CC:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>, <x86@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        <linux-edac@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-mm@kvack.org>, <jane.chu@oracle.com>
References: <20230508022233.13890-1-wangkefeng.wang@huawei.com>
From:   Kefeng Wang <wangkefeng.wang@huawei.com>
In-Reply-To: <20230508022233.13890-1-wangkefeng.wang@huawei.com>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

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>