linux-kernel - Re: [RFC PATCH 4/9] PCI/AER: Extend AER error handling to RCECs

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Message-ID: <BBEF2C05-521A-42D9-9AA4-F0B537E063F5@intel.com>
Date:   Mon, 27 Jul 2020 08:00:11 -0700
From:   "Sean V Kelley" <sean.v.kelley@...el.com>
To:     "Jonathan Cameron" <Jonathan.Cameron@...wei.com>
Cc:     bhelgaas@...gle.com, rjw@...ysocki.net, tony.luck@...el.com,
        "Raj, Ashok" <ashok.raj@...el.com>,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 4/9] PCI/AER: Extend AER error handling to RCECs

On 27 Jul 2020, at 7:04, Jonathan Cameron wrote:

> On Fri, 24 Jul 2020 10:22:18 -0700
> Sean V Kelley <sean.v.kelley@...el.com> wrote:
>
>> From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>>
>> Currently the kernel does not handle AER errors for Root Complex 
>> integrated
>> End Points (RCiEPs)[0]. These devices sit on a root bus within the 
>> Root Complex
>> (RC). AER handling is performed by a Root Complex Event Collector 
>> (RCEC) [1]
>> which is a effectively a type of RCiEP on the same root bus.
>>
>> For an RCEC (technically not a Bridge), error messages "received" 
>> from
>> associated RCiEPs must be enabled for "transmission" in order to 
>> cause a
>> System Error via the Root Control register or (when the Advanced 
>> Error
>> Reporting Capability is present) reporting via the Root Error Command
>> register and logging in the Root Error Status register and Error 
>> Source
>> Identification register.
>>
>> In addition to the defined OS level handling of the reset flow for 
>> the
>> associated RCiEPs of an RCEC, it is possible to also have a firmware 
>> first
>> model. In that case there is no need to take any actions on the RCEC 
>> because
>> the firmware is responsible for them. This is true where APEI [2] is 
>> used
>> to report the AER errors via a GHES[v2] HEST entry [3] and relevant
>> AER CPER record [4] and Firmware First handling is in use.
>>
>> We effectively end up with two different types of discovery for
>> purposes of handling AER errors:
>>
>> 1) Normal bus walk - we pass the downstream port above a bus to which
>> the device is attached and it walks everything below that point.
>>
>> 2) An RCiEP with no visible association with an RCEC as there is no 
>> need to
>> walk devices. In that case, the flow is to just call the callbacks 
>> for the actual
>> device.
>>
>> A new walk function, similar to pci_bus_walk is provided that takes a 
>> pci_dev
>> instead of a bus. If that dev corresponds to a downstream port it 
>> will walk
>> the subordinate bus of that downstream port. If the dev does not then 
>> it
>> will call the function on that device alone.
>>
>> [0] ACPI PCI Express Base Specification 5.0-1 1.3.2.3 Root Complex 
>> Integrated
>>     Endpoint Rules.
>> [1] ACPI PCI Express Base Specification 5.0-1 6.2 Error Signalling 
>> and Logging
>> [2] ACPI Specification 6.3 Chapter 18 ACPI Platform Error Interface 
>> (APEI)
>> [3] ACPI Specification 6.3 18.2.3.7 Generic Hardware Error Source
>> [4] UEFI Specification 2.8, N.2.7 PCI Express Error Section
>>
>> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>> Signed-off-by: Sean V Kelley <sean.v.kelley@...el.com>
>> ---
> ...
>
>
>>  	pci_dbg(dev, "broadcast resume message\n");
>> -	pci_walk_bus(bus, report_resume, &status);
>> +	pci_walk_dev_affected(dev, report_resume, &status);
>>
>> -	pci_aer_clear_device_status(dev);
>> -	pci_aer_clear_nonfatal_status(dev);
>
> This code had changed a little in Bjorn's pci/next branch so do a 
> rebase on that
> before v2.

Will ensure rebase includes pci/next.

Thanks,

Sean

>
>> +	if ((pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
>> +	     pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM ||
>> +	     pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)) {
>> +		pci_aer_clear_device_status(dev);
>> +		pci_aer_clear_nonfatal_status(dev);
>> +	}
>>  	pci_info(dev, "device recovery successful\n");
>>  	return status;
>>