linux-kernel - Re: [PATCH v15 1/3] ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

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Message-ID: <20241029204848.GA1229628@yaz-khff2.amd.com>
Date: Tue, 29 Oct 2024 16:48:48 -0400
From: Yazen Ghannam <yazen.ghannam@....com>
To: Shuai Xue <xueshuai@...ux.alibaba.com>
Cc: mark.rutland@....com, catalin.marinas@....com, mingo@...hat.com,
	robin.murphy@....com, Jonathan.Cameron@...wei.com, bp@...en8.de,
	rafael@...nel.org, wangkefeng.wang@...wei.com,
	tanxiaofei@...wei.com, mawupeng1@...wei.com, tony.luck@...el.com,
	linmiaohe@...wei.com, naoya.horiguchi@....com, james.morse@....com,
	tongtiangen@...wei.com, gregkh@...uxfoundation.org, will@...nel.org,
	jarkko@...nel.org, linux-acpi@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	linux-edac@...r.kernel.org, x86@...nel.org, justin.he@....com,
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	baolin.wang@...ux.alibaba.com, tglx@...utronix.de,
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	robert.moore@...el.com, lvying6@...wei.com, xiexiuqi@...wei.com,
	zhuo.song@...ux.alibaba.com
Subject: Re: [PATCH v15 1/3] ACPI: APEI: send SIGBUS to current task if
 synchronous memory error not recovered

On Mon, Oct 28, 2024 at 04:11:40PM +0800, Shuai Xue wrote:
> Synchronous error was detected as a result of user-space process accessing
> a 2-bit uncorrected error. The CPU will take a synchronous error exception
> such as Synchronous External Abort (SEA) on Arm64. The kernel will queue a
> memory_failure() work which poisons the related page, unmaps the page, and
> then sends a SIGBUS to the process, so that a system wide panic can be
> avoided.
> 
> However, no memory_failure() work will be queued when abnormal synchronous
> errors occur. These errors can include situations such as invalid PA,
> unexpected severity, no memory failure config support, invalid GUID
> section, etc. In such case, the user-space process will trigger SEA again.
> This loop can potentially exceed the platform firmware threshold or even
> trigger a kernel hard lockup, leading to a system reboot.
> 
> Fix it by performing a force kill if no memory_failure() work is queued
> for synchronous errors.
> 
> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
> Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
>  drivers/acpi/apei/ghes.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index ada93cfde9ba..f2ee28c44d7a 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -801,6 +801,16 @@ static bool ghes_do_proc(struct ghes *ghes,
>  		}
>  	}
>  
> +	/*
> +	 * If no memory failure work is queued for abnormal synchronous
> +	 * errors, do a force kill.
> +	 */
> +	if (sync && !queued) {
> +		pr_err("%s:%d: hardware memory corruption (SIGBUS)\n",
> +			current->comm, task_pid_nr(current));

I think it would help to include the GHES_PFX to indicate where this
message is coming from. The pr_fmt() macro could also be introduced
instead.

Also, you may want to include the HW_ERR prefix. Not all kernel messages
related to hardware errors have this prefix today. But maybe that should
be changed so there is more consistent messaging.

Thanks,
Yazen