linux-kernel - Re: [PATCH] acpi: apei: call into AER handling regardless of severity

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Date:   Wed, 30 Aug 2017 11:31:06 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     Borislav Petkov <bp@...e.de>
Cc:     "Baicar, Tyler" <tbaicar@...eaurora.org>,
        Tony Luck <tony.luck@...el.com>, rjw@...ysocki.net,
        lenb@...nel.org, will.deacon@....com, james.morse@....com,
        prarit@...hat.com, punit.agrawal@....com, shiju.jose@...wei.com,
        andriy.shevchenko@...ux.intel.com, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Linux PCI <linux-pci@...r.kernel.org>,
        Huang Ying <ying.huang@...el.com>
Subject: Re: [PATCH] acpi: apei: call into AER handling regardless of severity

On 8/30/2017 11:16 AM, Borislav Petkov wrote:
> On Wed, Aug 30, 2017 at 10:05:44AM -0400, Sinan Kaya wrote:
>> Link reset is not the only recovery mechanism. In the case of nonfatal
>> errors, it is assumed that the endpoint CSR is still reachable.
>> Error is propagated the PCIe endpoint driver. Endpoint driver does a
>> re-initialization, we are back in business.
> 
> I'm assuming that's broadcast_error_message()'s job.
> 

That's right. Each driver provides an err_handler hook. broadcast function
calls these. 

static struct pci_driver e1000_driver = {
	..
	.err_handler = &e1000_err_handler
};

struct pci_error_handlers {
	...
	pci_ers_result_t (*error_detected)(struct pci_dev *dev,
					   enum pci_channel_state error);
}


>> That's not true. The GHES code is changing the severity here before posting
>> to the AER driver in ghes_do_proc().
>>
>> 	if (gdata->flags & CPER_SEC_RESET)
>> 		aer_severity = AER_FATAL;
> 
> You're missing the point that we would walk into that if branch *only* for
> 
>                         if (sev == GHES_SEV_RECOVERABLE &&
>                             sec_sev == GHES_SEV_RECOVERABLE
> 
> severities. So if you have an AER_FATAL error but ghes severities are
> not GHES_SEV_RECOVERABLE, nothing happens.

I see. We should probably try to do something only if GHES_SEV_CORRECTED or
GHES_SEV_RECOVERABLE.

If somebody wants to crash the system with GHES_SEV_PANIC, there is no point
in doing additional work.

> 
>> No, AER ISR is not set up if firmware first is enabled.
> 
> So then this is a major suckage. We do AER recovery on FF systems only
> for GHES_SEV_RECOVERABLE severity.
> 
>> The behavior should match non firmware-first case ideally.
>>
>> 1. Print all correctable errors.
>> 2. Go to do_recovery for all uncorrectable errors including fatal and
>> non-fatal. 
>>
>> This is also what AER driver does in the absence of firmware first via
>> handle_error_source().
> 
> Yes, that makes sense.
> 
> Which would mean that we'd call aer_recover_queue() regardless of GHES
> severity but we'd do recovery only if GHES_SEV_RECOVERABLE is set
> or CPER_SEC_RESET. I.e., we can communicate all that by setting the
> correct AER severity before calling aer_recover_queue(). And then call
> do_recovery() based on AER severity.
> 
> Hmmm?
> 

Sounds good. Do you still want to do PCIe recovery in the case of
GHES_SEV_PANIC or if some FW returns GHES_SEV_NO?

-- 
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.