linux-kernel - Re: [RFC PATCH 1/9] PCI/AER: Update AER driver to call root port and downstream port UCE handlers

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Date: Mon, 24 Jun 2024 09:58:02 -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 1/9] PCI/AER: Update AER driver to call root port and
 downstream port UCE handlers

Hi Jonathan,
I added a response below.

On 6/20/24 06:21, Jonathan Cameron wrote:
> On Mon, 17 Jun 2024 15:04:03 -0500
> Terry Bowman <terry.bowman@....com> wrote:
> 
>> The AER service driver does not currently call a handler for AER
>> uncorrectable errors (UCE) detected in root ports or downstream
>> ports. This is not needed in most cases because common PCIe port
>> functionality is handled by portdrv service drivers.
>>
>> CXL root ports include CXL specific RAS registers that need logging
>> before starting do_recovery() in the UCE case.
>>
>> Update the AER service driver to call the UCE handler for root ports
>> and downstream ports. These PCIe port devices are bound to the portdrv
>> driver that includes a CE and UCE handler to be called.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@....com>
>> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
>> Cc: linux-pci@...r.kernel.org
>> ---
>>  drivers/pci/pcie/err.c | 20 ++++++++++++++++++++
>>  1 file changed, 20 insertions(+)
>>
>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> index 705893b5f7b0..a4db474b2be5 100644
>> --- a/drivers/pci/pcie/err.c
>> +++ b/drivers/pci/pcie/err.c
>> @@ -203,6 +203,26 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>>  	pci_ers_result_t status = PCI_ERS_RESULT_CAN_RECOVER;
>>  	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
>>  
>> +	/*
>> +	 * PCIe ports may include functionality beyond the standard
>> +	 * extended port capabilities. This may present a need to log and
>> +	 * handle errors not addressed in this driver. Examples are CXL
>> +	 * root ports and CXL downstream switch ports using AER UIE to
>> +	 * indicate CXL UCE RAS protocol errors.
>> +	 */
>> +	if (type == PCI_EXP_TYPE_ROOT_PORT ||
>> +	    type == PCI_EXP_TYPE_DOWNSTREAM) {
>> +		struct pci_driver *pdrv = dev->driver;
>> +
>> +		if (pdrv && pdrv->err_handler &&
>> +		    pdrv->err_handler->error_detected) {
>> +			const struct pci_error_handlers *err_handler;
>> +
>> +			err_handler = pdrv->err_handler;
>> +			status = err_handler->error_detected(dev, state);
> 
> This status is going to get overridden by one of the pci_walk_bridge()
> calls.  Should it be kept around and acted on, or dropped silently?
> (I'd guess no for silent!).
> 

It should be used later.

According to PCI spec "The only method of recovering from an Uncorrectable
Internal Error is reset or hardware replacement."

I need to make certain that carries through below.

Regards,
Terry

>> +		}
>> +	}
>> +
>>  	/*
>>  	 * If the error was detected by a Root Port, Downstream Port, RCEC,
>>  	 * or RCiEP, recovery runs on the device itself.  For Ports, that
>