Re: [PATCH v3] vmcoreinfo: Track and log recoverable hardware errors

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

在 2025/7/24 21:34, Breno Leitao 写道:
> Hello Shuai,
> 
> On Thu, Jul 24, 2025 at 04:00:09PM +0800, Shuai Xue wrote:
>> 在 2025/7/23 00:56, Breno Leitao 写道:
>>> Introduce a generic infrastructure for tracking recoverable hardware
>>> errors (HW errors that did not cause a panic) and record them for vmcore
>>> consumption. This aids post-mortem crash analysis tools by preserving
>>> a count and timestamp for the last occurrence of such errors.
>>>
>>> Add centralized logging for three common sources of recoverable hardware
>>> errors:
>>
>> The term "recoverable" is highly ambiguous. Even within the x86
>> architecture, different vendors define errors differently. I'm not
>> trying to be pedantic about classification. As far as I know, for 2-bit
>> memory errors detected by scrub, AMD defines them as deferred errors
>> (DE) and handles them with log_error_deferred, while Intel uses
>> machine_check_poll. For 2-bit memory errors consumed by processes,
>> both Intel and AMD use MCE handling via do_machine_check(). Does your
>> HWERR_RECOV_MCE only focus on synchronous UE errors handled in
>> do_machine_check? What makes it special?
> 
> I understand that deferred errors (DE) detected by memory scrubbing are
> typically silent and may not significantly impact system stability. In
> other words, I’m not convinced that including DE metrics in crash dumps
> would be helpful for correlating crashes with hardware issues—it might
> just add noise.
> 
> Do you think it would be valuable to also log these events within
> log_error_deferred()?

Not really, as you meationed, the DE is typically silent in backgroud.
But I hope it is well documented.
> 
>>> -	if (ghes_severity(estatus->error_severity) >= GHES_SEV_PANIC)
>>> +	sev = ghes_severity(estatus->error_severity);
>>> +	if (sev == GHES_SEV_RECOVERABLE || sev ==  GHES_SEV_CORRECTED)
>>> +		hwerr_log_error_type(HWERR_RECOV_GHES);
>>
>> APEI does not define an error type named GHES. GHES is just a kernel
>> driver name. Many hardware error types can be handled in GHES (see
>> ghes_do_proc), for example, AER is routed by GHES when firmware-first
>> mode is used. As far as I know, firmware-first mode is commonly used in
>> production. Should GHES errors be categorized into AER, memory, and CXL
>> memory instead?
> 
> I also considered slicing the data differently initially, but then
> realized it would add more complexity than necessary for my needs.
> 
> If you believe we should further subdivide the data, I’m happy to do so.
> 
> You’re suggesting a structure like this, which would then map to the
> corresponding CPER_SEC_ sections:
> 
> 	enum hwerr_error_type {
> 	HWERR_RECOV_AER,     // maps to CPER_SEC_PCIE
> 	HWERR_RECOV_MCE,     // maps to default MCE + CPER_SEC_PCIE

CPER_SEC_PCIE is typo?

> 	HWERR_RECOV_CXL,     // maps to CPER_SEC_CXL_*
> 	HWERR_RECOV_MEMORY,  // maps to CPER_SEC_PLATFORM_MEM
> 	}
> 
> Additionally, what about events related to CPU, Firmware, or DMA
> errors—for example, CPER_SEC_PROC, CPER_SEC_FW, CPER_SEC_DMAR? Should we
> include those in the classification as well?

I would like to split a error from ghes to its own type,
it sounds more reasonable. I can not tell what happened from HWERR_RECOV_AERat all :(
> 
> 
> Thanks for your review and for the ongoing discussion!
> --breno

Thanks.
Shuai