linux-kernel - Re: [PATCH v11 1/3] ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

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Message-ID: <bdf15819-46e0-498f-97e1-a0183f257086@linux.alibaba.com>
Date: Thu, 22 Feb 2024 10:07:18 +0800
From: Shuai Xue <xueshuai@...ux.alibaba.com>
To: Borislav Petkov <bp@...en8.de>, Ira Weiny <ira.weiny@...el.com>,
 "Luck, Tony" <tony.luck@...el.com>, "james.morse@....com"
 <james.morse@....com>
Cc: rafael@...nel.org, wangkefeng.wang@...wei.com, tanxiaofei@...wei.com,
 mawupeng1@...wei.com, tony.luck@...el.com, linmiaohe@...wei.com,
 naoya.horiguchi@....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,
 ardb@...nel.org, ying.huang@...el.com, ashish.kalra@....com,
 baolin.wang@...ux.alibaba.com, tglx@...utronix.de, mingo@...hat.com,
 dave.hansen@...ux.intel.com, lenb@...nel.org, hpa@...or.com,
 robert.moore@...el.com, lvying6@...wei.com, xiexiuqi@...wei.com,
 zhuo.song@...ux.alibaba.com, Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v11 1/3] ACPI: APEI: send SIGBUS to current task if
 synchronous memory error not recovered



On 2024/2/19 17:25, Borislav Petkov wrote:
> On Sun, Feb 04, 2024 at 04:01:42PM +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>
>> ---
>>  drivers/acpi/apei/ghes.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
>> index 7b7c605166e0..0892550732d4 100644
>> --- a/drivers/acpi/apei/ghes.c
>> +++ b/drivers/acpi/apei/ghes.c
>> @@ -806,6 +806,15 @@ 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("Sending SIGBUS to current task due to memory error not recovered");
>> +		force_sig(SIGBUS);
>> +	}
> 
> Except that there are a bunch of CXL GUIDs being handled there too and
> this will sigbus those processes now automatically.

Before the CXL GUIDs added, @Tony confirmed that the HEST notifications are always
asynchronous on x86 platform, so only Synchronous External Abort (SEA) on ARM is
delivered as a synchronous notification.

Will the CXL component trigger synchronous events for which we need to terminate the
current process by sending sigbus to process?

> 
> Lemme add the whole bunch from
> 
>   671a794c33c6 ("acpi/ghes: Process CXL Component Events")
> 
> for comment to Cc.
> 

Thank you.

Best Regards,
Shuai