Re: [PATCH v12 1/3] ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

[Shuai Xue <xueshuai@linux.alibaba.com>]

在 2024/9/5 22:17, Jarkko Sakkinen 写道:
> On Thu Sep 5, 2024 at 5:14 PM EEST, Jarkko Sakkinen wrote:
>> On Thu Sep 5, 2024 at 6:04 AM EEST, Shuai Xue wrote:
>>>
>>>
>>> 在 2024/9/4 00:09, Jarkko Sakkinen 写道:
>>>> On Mon Sep 2, 2024 at 6:00 AM EEST, 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 unless all bellow
>>>>> preconditions check passed:
>>>>>
>>>>> - `if (!(mem_err->validation_bits & CPER_MEM_VALID_PA))` in ghes_handle_memory_failure()
>>>>> - `if (flags == -1)` in ghes_handle_memory_failure()
>>>>> - `if (!IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE))` in ghes_do_memory_failure()
>>>>> - `if (!pfn_valid(pfn) && !arch_is_platform_page(physical_addr)) ` in ghes_do_memory_failure()
>>>>>
>>>>> 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.
>>>>>
>>>>> Suggested-by: Xiaofei Tan <tanxiaofei@huawei.com>
>>>>> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.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 623cc0cb4a65..b0b20ee533d9 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("Sending SIGBUS to %s:%d due to hardware memory corruption\n",
>>>>> +			current->comm, task_pid_nr(current));
>>>>
>>>> Hmm... doest this need "hardware" or would "memory corruption" be
>>>> enough?
>>>>
>>>> Also, does this need to say that it is sending SIGBUS when the signal
>>>> itself tells that already?
>>>>
>>>> I.e. could "%s:%d has memory corruption" be enough information?
>>>
>>> Hi, Jarkko,
>>>
>>> Thank you for your suggestion. Maybe it could.
>>>
>>> There are some similar error info which use "hardware memory error", e.g.
>>
>> By tweaking my original suggestion just a bit:
>>
>> "%s:%d: hardware memory corruption"
>>
>> Can't get clearer than that, right?
> 
> And obvious reason that shorter and more consistent klog message is easy
> to spot and grep. It is simply less convoluted.
> 
> If you want also SIGBUS, I'd just put it as "%s:%d: hardware memory
> corruption (SIGBUS)"
> 
> BR, Jarkko

Hi, Jarkko,

I will change it to "%s:%d: hardware memory corruption (SIGBUS)".

Thank you for valuable suggestion.

Best Regards,
Shuai