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Message-ID: <bdf15819-46e0-498f-97e1-a0183f257086@linux.alibaba.com>
Date: Thu, 22 Feb 2024 10:07:18 +0800
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Subject: Re: [PATCH v11 1/3] ACPI: APEI: send SIGBUS to current task if
 synchronous memory error not recovered
To: Borislav Petkov <bp@alien8.de>, Ira Weiny <ira.weiny@intel.com>,
 "Luck, Tony" <tony.luck@intel.com>, "james.morse@arm.com"
 <james.morse@arm.com>
Cc: rafael@kernel.org, wangkefeng.wang@huawei.com, tanxiaofei@huawei.com,
 mawupeng1@huawei.com, tony.luck@intel.com, linmiaohe@huawei.com,
 naoya.horiguchi@nec.com, gregkh@linuxfoundation.org, will@kernel.org,
 jarkko@kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
 linux-edac@vger.kernel.org, x86@kernel.org, justin.he@arm.com,
 ardb@kernel.org, ying.huang@intel.com, ashish.kalra@amd.com,
 baolin.wang@linux.alibaba.com, tglx@linutronix.de, mingo@redhat.com,
 dave.hansen@linux.intel.com, lenb@kernel.org, hpa@zytor.com,
 robert.moore@intel.com, lvying6@huawei.com, xiexiuqi@huawei.com,
 zhuo.song@linux.alibaba.com, Jonathan Cameron <Jonathan.Cameron@huawei.com>,
 Dan Williams <dan.j.williams@intel.com>
References: <20221027042445.60108-1-xueshuai@linux.alibaba.com>
 <20240204080144.7977-2-xueshuai@linux.alibaba.com>
 <20240219092528.GTZdMeiDWIDz613VeT@fat_crate.local>
Content-Language: en-US
From: Shuai Xue <xueshuai@linux.alibaba.com>
In-Reply-To: <20240219092528.GTZdMeiDWIDz613VeT@fat_crate.local>
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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@linux.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