Re: [PATCH v15 1/3] ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

Shuai Xue
2024-10-30T01:54:08Z

在 2024/10/30 04:48, Yazen Ghannam 写道:
> On Mon, Oct 28, 2024 at 04:11:40PM +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>
>> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.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 ada93cfde9ba..f2ee28c44d7a 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("%s:%d: hardware memory corruption (SIGBUS)\n",
>> + current->comm, task_pid_nr(current));
>
> I think it would help to include the GHES_PFX to indicate where this
> message is coming from. The pr_fmt() macro could also be introduced
> instead.

Yes, GHES_PFX is a effective prefix and will be consistent to other
message in GHES driver. Will add it in next version.

What do you mean about pr_fmt()?

>
> Also, you may want to include the HW_ERR prefix. Not all kernel messages
> related to hardware errors have this prefix today. But maybe that should
> be changed so there is more consistent messaging.
>

Do we really need a HW_ERR prefix? The other case which use HW_ERR
prefix are for hardware registers. The messages which send SIGBUS does
not include HW_ERR, e.g. in kill_proc(), kill_procs().

pr_err("%#lx: Sending SIGBUS to %s:%d due to hardware memory
corruption\n",...
pr_err("%#lx: forcibly killing %s:%d because of failure to unmap
corrupted page\n",...

> Thanks,
> Yazen

Thanks for valuable comments.

Best Regards,
Shuai