linux-kernel - Re: [PATCH v11 1/8] PCI/ERR: Update error status after reset

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Date:   Fri, 3 Jan 2020 17:03:03 -0800
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        ashok.raj@...el.com, keith.busch@...el.com
Subject: Re: [PATCH v11 1/8] PCI/ERR: Update error status after reset_link()


On 1/3/20 4:34 PM, Bjorn Helgaas wrote:
> On Thu, Dec 26, 2019 at 04:39:07PM -0800, sathyanarayanan.kuppuswamy@...ux.intel.com wrote:
>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>>
>> Commit bdb5ac85777d ("PCI/ERR: Handle fatal error recovery") uses
>> reset_link() to recover from fatal errors. But, if the reset is
>> successful there is no need to continue the rest of the error recovery
>> checks. Also, during fatal error recovery, if the initial value of error
>> status is PCI_ERS_RESULT_DISCONNECT or PCI_ERS_RESULT_NO_AER_DRIVER then
>> even after successful recovery (using reset_link()) pcie_do_recovery()
>> will report the recovery result as failure. So update the status of
>> error after reset_link().
> I like the part about updating "status" with the result of
> reset_link(), and I split that into its own patch because it
> seems like a fix that *can* be separated.
>
> But I'm not convinced that we should skip the ->slot_reset()
> callbacks if the reset_link() was successful.
If reset_link() call is successful then the result value will be
"PCI_ERS_RESULT_RECOVERED". So even if you proceed with
rest of the code, slot_reset() will never get called right ?
>    According to
> Documentation/PCI/pci-error-recovery.rst, we should call
> ->slot_reset() after completion of the reset.
>
> For example, rsxx_err_handler implements ->slot_reset(), but
> not ->resume().  If we reset the device, we'll claim success and
> return, but we won't call rsxx_slot_reset(), which does a bunch
> of important-looking recovery stuff.
>
> If pci-error-recovery.rst is wrong, we should fix that (after
> auditing all the drivers to make sure they match).
>
>> Fixes: bdb5ac85777d ("PCI/ERR: Handle fatal error recovery")
>> Cc: Ashok Raj <ashok.raj@...el.com>
>> Cc: Keith Busch <keith.busch@...el.com>
>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>> Acked-by: Keith Busch <keith.busch@...el.com>
>> ---
>>   drivers/pci/pcie/err.c | 10 +++++++---
>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> index b0e6048a9208..53cd9200ec2c 100644
>> --- a/drivers/pci/pcie/err.c
>> +++ b/drivers/pci/pcie/err.c
>> @@ -204,9 +204,12 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>>   	else
>>   		pci_walk_bus(bus, report_normal_detected, &status);
>>   
>> -	if (state == pci_channel_io_frozen &&
>> -	    reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
>> -		goto failed;
>> +	if (state == pci_channel_io_frozen) {
>> +		status = reset_link(dev, service);
>> +		if (status != PCI_ERS_RESULT_RECOVERED)
>> +			goto failed;
>> +		goto done;
>> +	}
>>   
>>   	if (status == PCI_ERS_RESULT_CAN_RECOVER) {
>>   		status = PCI_ERS_RESULT_RECOVERED;
>> @@ -228,6 +231,7 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>>   	if (status != PCI_ERS_RESULT_RECOVERED)
>>   		goto failed;
>>   
>> +done:
>>   	pci_dbg(dev, "broadcast resume message\n");
>>   	pci_walk_bus(bus, report_resume, &status);
>>   
>> -- 
>> 2.21.0
>>
-- 
Sathyanarayanan Kuppuswamy
Linux kernel developer