Re: [PATCH v14 1/3] ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

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

在 2024/10/17 17:39, Jonathan Cameron 写道:
> On Mon, 14 Oct 2024 16:42:38 +0800
> Shuai Xue <xueshuai@linux.alibaba.com> 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>
> 
> The subtle cases in here are the various other forms of delayed handling
> buried in some of the record handling that don't set queued.
> I've been through them all and have convinced myself that either
> hey should never be synchronous or that there is no attempt to
> recover in kernel today (non memory things such as CXL protocol
> collapse, which might I guess be detected synchronously on a read
> - though I'd expect poison and a memory error first) so the correct
> thing to do is what you have here.
> 
> Fiddly code though with a lot of paths, so more eyes welcome!
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> +CC linux-cxl for info.

Thanks :)

Best Regards,
Shuai