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: <d62d775e-08e3-4a2d-88a8-437a4c04ebd3@linux.alibaba.com>
Date: Wed, 30 Oct 2024 09:54:00 +0800
From: Shuai Xue <xueshuai@...ux.alibaba.com>
To: Yazen Ghannam <yazen.ghannam@....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



在 2024/10/30 04:48, Yazen Ghannam 写道:
> 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.

Yes, GHES_PFX is a effective prefix and will be consistent to other 
message in GHES driver. Will add it in next version.

What do you mean about pr_fmt()?

> 
> 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.
> 

Do we really need a HW_ERR prefix? The other case which use HW_ERR 
prefix are for hardware registers. The messages which send SIGBUS does
not include HW_ERR, e.g. in kill_proc(), kill_procs().

     pr_err("%#lx: Sending SIGBUS to %s:%d due to hardware memory 
corruption\n",...
     pr_err("%#lx: forcibly killing %s:%d because of failure to unmap 
corrupted page\n",...


> Thanks,
> Yazen

Thanks for valuable comments.

Best Regards,
Shuai