Re: [RESEND PATCH v18 1/2] ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

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

在 2025/4/18 15:48, Hanjun Guo 写道:
> On 2025/4/14 23:02, Shuai Xue wrote:
>>
>>
>> 在 2025/4/14 22:37, Hanjun Guo 写道:
>>> On 2025/4/4 19:20, 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>
>>>> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
>>>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>>>> Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
>>>> Reviewed-by: Jane Chu <jane.chu@oracle.com>
>>>> ---
>>>>   drivers/acpi/apei/ghes.c | 11 +++++++++++
>>>>   1 file changed, 11 insertions(+)
>>>>
>>>> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
>>>> index b72772494655..50e4d924aa8b 100644
>>>> --- a/drivers/acpi/apei/ghes.c
>>>> +++ b/drivers/acpi/apei/ghes.c
>>>> @@ -799,6 +799,17 @@ 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) {
>>>> +        dev_err(ghes->dev,
>>>> +            HW_ERR GHES_PFX "%s:%d: synchronous unrecoverable error (SIGBUS)\n",
>>>> +            current->comm, task_pid_nr(current));
>>>> +        force_sig(SIGBUS);
>>>> +    }
>>>
>>> I think it's reasonable to send a force kill to the task when the
>>> synchronous memory error is not recovered.
>>>
>>> But I hope this code will not trigger some legacy firmware issues,
>>> let's be careful for this, so can we just introduce arch specific
>>> callbacks for this?
>>
>> Sorry, can you give more details? I am not sure I got your point.
>>
>> For x86, Tony confirmed that ghes will not dispatch x86 synchronous errors
>> (a.k.a machine check exception), in previous vesion.
>> Sync is only used in arm64 platform, see is_hest_sync_notify().
> 
> Sorry for the late reply, from the code I can see that x86 will reuse
> ghes_do_proc(), if Tony confirmed that x86 is OK, it's OK to me as well.

Hi, Hanjun,

Glad to hear that.

I copy and paste in the original disscusion with @Tony from mailist.[1]

> On x86 the "action required" cases are signaled by a synchronous machine check
> that is delivered before the instruction that is attempting to consume the uncorrected
> data retires. I.e., it is guaranteed that the uncorrected error has not been propagated
> because it is not visible in any architectural state.

> APEI signaled errors don't fall into that category on x86 ... the uncorrected data
> could have been consumed and propagated long before the signaling used for
> APEI can alert the OS.

I also add comments in the code.

/*
  * A platform may describe one error source for the handling of synchronous
  * errors (e.g. MCE or SEA), or for handling asynchronous errors (e.g. SCI
  * or External Interrupt). On x86, the HEST notifications are always
  * asynchronous, so only SEA on ARM is delivered as a synchronous
  * notification.
  */
static inline bool is_hest_sync_notify(struct ghes *ghes)
{
	u8 notify_type = ghes->generic->notify.type;

	return notify_type == ACPI_HEST_NOTIFY_SEA;
}


If you are happy with code, please explictly give me your reviewed-by tags :)


> 
> Thanks
> Hanjun

Thanks.

Best Regards,
Shuai

[1] https://lore.kernel.org/lkml/CAJZ5v0hdgxsDiXqOmeqBQoZUQJ1RssM=3jpYpWt3qzy0n2eyaA@mail.gmail.com/t/#u