Re: [PATCH v2] ACPI: APEI: Handle repeated SEA error storms

[hejunhao]

Hi All,


a gentle ping on this.
All comments are welcomed!


On 2026/7/23 16:32, hejunhao wrote:
>
> On 2026/7/9 1:14, Luck, Tony wrote:
>> On Wed, May 27, 2026 at 04:27:07PM +0800, Junhao He wrote:
>>> When hardware memory corruption occurs and a user process accesses the
>>> corrupted page, the CPU triggers a Synchronous External Abort (SEA).
>>> The kernel invokes do_sea() to handle the exception, which calls
>>> memory_failure() to handle the faulty page.
>>>
>>> Scenario 1: Memory Error Interrupt First, then SEA
>>> The page is already poisoned by the memory error interrupt path. The
>>> subsequent SEA handler sends a SIGBUS to the task, which accesses the
>>> poisoned page. This flow is correct.
>>>
>>> Scenario 2: SEA first, then memory error interrupt (problematic scenario)
>>> If a user task directly accesses corrupted memory through a PFNMAP-style
>>> mapping (e.g., devmem), the page may still be in the free-buddy state when
>>> SEA is handled. In this case, memory_failure() will poison the page without
>>> invoking kill_accessing_process(), and then takes the free-buddy recovery
>>> path.
>>>
>>> After the CPU returns to the task context, the task re-enters the SEA
>>> handler due to the same access. However, ghes_estatus_cached() suppresses
>>> all subsequent entries during the 10-second window, preventing
>>> ghes_do_proc() from being called. This suppression blocks the
>>> MF_ACTION_REQUIRED-based SIGBUS delivery, causing the kernel to fail to
>>> kill the task immediately. Consequently, the process keeps re-entering
>>> the SEA handler, leading to an SEA storm. Later, the memory error
>>> interrupt path also cannot kill the task, leaving the system stuck in
>>> this repeated loop.
>>>
>>> The following error logs are explained using the devmem process:
>>>   NOTICE:  SEA Handle
>>>   [Hardware Error]: Hardware error from APEI Generic Hardware Error Source: 9
>>>   [Hardware Error]: event severity: recoverable
>>>   [Hardware Error]:   section_type: ARM processor error
>>>   [Hardware Error]:    physical fault address: 0x0000001000093c00
>>>   [T54990] Memory failure: 0x1000093: recovery action for free buddy page: Recovered
>>>   [ T9955] EDAC MC0: 1 UE Multi-bit ECC on unknown memory
>>>            (page:0x1000093 offset:0xc00 grain:1 - APEI location: ...)
>>>   NOTICE:  SEA Handle
>>>   NOTICE:  SEA Handle
>>>   ...
>>>   ...        ---> SEA storm
>>>   ...
>>>   NOTICE:  SEA Handle
>>>   [ T9955] Memory failure: 0x1000093: already hardware poisoned
>>>   ghes_print_estatus: 1 callbacks suppressed
>>>   [Hardware Error]: Hardware error from APEI Generic Hardware Error Source: 9
>>>   [Hardware Error]: event severity: recoverable
>>>   [Hardware Error]:   section_type: ARM processor error
>>>   [Hardware Error]:    physical fault address: 0x0000001000093c00
>>>   [T54990] Memory failure: 0x1000093: already hardware poisoned
>>>   [T54990] 0x1000093: Sending SIGBUS to devmem:54990 due to hardware memory corruption
>>>
>>> To resolve this, return an error when encountering the same SEA again.
>>> The subsequent SEA handler invocation uses arm64_notify_die() to send a
>>> SIGBUS signal to the task, which terminates the process and prevents it
>>> from re-entering the handler loop.
>>>
>>> Signed-off-by: Junhao He <hejunhao3@xxxxxxxxxxxxxx>
>>> ---
>>>  drivers/acpi/apei/ghes.c | 10 +++++++++-
>>>  1 file changed, 9 insertions(+), 1 deletion(-)
>>>
>>> Changes in V2:
>>> 1. update the commit message per suggestion from Xueshuai
>>> 2. Add a check to only return failure on the ghes_notify_sea() path,
>>>    avoiding impact on other NMI-type GHES handlers.
>>> Link to V1 - https://lore.kernel.org/all/20251030071321.2763224-1-hejunhao3@xxxxxxxxxxxxxx/
>>>
>>> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
>>> index 3236a3ce79d6..787664740150 100644
>>> --- a/drivers/acpi/apei/ghes.c
>>> +++ b/drivers/acpi/apei/ghes.c
>>> @@ -1383,8 +1383,16 @@ static int ghes_in_nmi_queue_one_entry(struct ghes *ghes,
>> ghes_in_nmi_queue_one_entry() is called from two places:
>>
>> __ghes_sdei_callback()
>>
>> I think, but I'm not sure, that you are addressing call from here. By
>> returning -ECANCELLED this code skips the irq_work_queue() call and
>> returns -ENOENT (instead of zero).
>>
>> ghes_in_nmi_spool_from_list()
>>
>> Effect here is more complex. Depends on whether there are multiple
>> ghes entries on the rcu_list. If there was just one, and you return
>> -ECANCELLED, then irq_work_queue() is skipped. But if there are multiple
>> entries on the list and at least one of them gets a zero return from
>> ghes_in_nmi_queue_one_entry() then irq_work_queue() is called.
> Hi Luck Tony,
>
> Thanks for the comments.
>
> This fix is only for the call to ghes_in_nmi_spool_from_list() from ghes_notify_sea() on
> ARM platforms (ACPI_HEST_NOTIFY_SEA); other paths are unchanged.
>
> If multiple SEA errors occur simultaneously, multiple entries in ghes_sea are active
> and one of them returns 0, then -ECANCELED is discarded, but the unhandled
> SEA will simply trigger again and re-enter the SEA handler to be processed.
>
> The worst case is when multiple valid SEA entries persist within the 10-second
> ghes_estatus_cached() window — the fact is that a great many SEA errors are
> produced, which actually constitutes a real SEA storm, not one triggered by a single
> SEA, and in this situation not delivering SIGBUS in time to kill the process is acceptable.
>
> Best regards,
> Junhao.
>
>>
>> So which of these callers is the one that needs this fix? And is the
>> other called OK with getting -ECANCELLED error?
>>
>>>  	ghes_clear_estatus(ghes, &tmp_header, buf_paddr, fixmap_idx);
>>>  
>>>  	/* This error has been reported before, don't process it again. */
>>> -	if (ghes_estatus_cached(estatus))
>>> +	if (ghes_estatus_cached(estatus)) {
>>> +		/*
>>> +		 * Return failure on duplicate SEA entries so that the
>>> +		 * subsequent SEA handler invocation sends a SIGBUS signal to
>>> +		 * the task to prevent it from re-entering the handler loop.
>>> +		 */
>>> +		if (is_hest_sync_notify(ghes))
>>> +			rc = -ECANCELED;
>>>  		goto no_work;
>>> +	}
>>>  
>>>  	llist_add(&estatus_node->llnode, &ghes_estatus_llist);
>>>  
>>> -- 
>>> 2.33.0
>>>
>> -Tony
>>
>> .
>>
> .
>