linux-kernel - Re: [RFC PATCH 2/9] PCI/AER: Call AER CE handler before clearing AER CE status register

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Date: Mon, 24 Jun 2024 10:08:44 -0500
From: Terry Bowman <Terry.Bowman@....com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: dan.j.williams@...el.com, ira.weiny@...el.com, dave@...olabs.net,
 dave.jiang@...el.com, alison.schofield@...el.com, ming4.li@...el.com,
 vishal.l.verma@...el.com, jim.harris@...sung.com,
 ilpo.jarvinen@...ux.intel.com, ardb@...nel.org,
 sathyanarayanan.kuppuswamy@...ux.intel.com, linux-cxl@...r.kernel.org,
 linux-kernel@...r.kernel.org, Yazen.Ghannam@....com, Robert.Richter@....com,
 Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org
Subject: Re: [RFC PATCH 2/9] PCI/AER: Call AER CE handler before clearing AER
 CE status register



On 6/20/24 06:31, Jonathan Cameron wrote:
> On Mon, 17 Jun 2024 15:04:04 -0500
> Terry Bowman <terry.bowman@....com> wrote:
> 
>> The AER service driver clears the AER correctable error (CE) status before
>> calling the correctable error handler. This results in the error's status
>> not correctly reflected if read from the CE handler.
>>
>> The AER CE status is needed by the portdrv's CE handler. The portdrv's
>> CE handler is intended to only call the registered notifier callbacks
>> if the CE error status has correctable internal error (CIE) set.
>>
>> This is not a problem for AER uncorrrectbale errors (UCE). The UCE status
> 
> uncorrectable
> 

Thank you.

>> is still present in the AER capability and available for reading, if
>> needed, when the UCE handler is called.
> 
> I'm seeing the clear in the DPC path for UCE. For other cases is
> it a side effect of the reset?
> 

Depends on when its being read. I'm assuming this is after recovery in your case. 
And after recovery it will be zeroed.

Regards,
Terry

>>
>> Change the order of clearing the CE status and calling the CE handler.
>> Make it to call the CE handler first and then clear the CE status
>> after returning.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@....com>
>> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
>> Cc: linux-pci@...r.kernel.org
> Seems reasonable, but many gremlins around the ordering in these
> flows, so I'm to particularly confident. With that in mind.
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...ei.com>
> 
>> ---
>>  drivers/pci/pcie/aer.c | 7 ++++---
>>  1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>> index ac6293c24976..4dc03cb9aff0 100644
>> --- a/drivers/pci/pcie/aer.c
>> +++ b/drivers/pci/pcie/aer.c
>> @@ -1094,9 +1094,6 @@ static void pci_aer_handle_error(struct pci_dev *dev, struct aer_err_info *info)
>>  		 * Correctable error does not need software intervention.
>>  		 * No need to go through error recovery process.
>>  		 */
>> -		if (aer)
>> -			pci_write_config_dword(dev, aer + PCI_ERR_COR_STATUS,
>> -					info->status);
>>  		if (pcie_aer_is_native(dev)) {
>>  			struct pci_driver *pdrv = dev->driver;
>>  
>> @@ -1105,6 +1102,10 @@ static void pci_aer_handle_error(struct pci_dev *dev, struct aer_err_info *info)
>>  				pdrv->err_handler->cor_error_detected(dev);
>>  			pcie_clear_device_status(dev);
>>  		}
>> +		if (aer)
>> +			pci_write_config_dword(dev, aer + PCI_ERR_COR_STATUS,
>> +					info->status);
>> +
>>  	} else if (info->severity == AER_NONFATAL)
>>  		pcie_do_recovery(dev, pci_channel_io_normal, aer_root_reset);
>>  	else if (info->severity == AER_FATAL)
>