linux-kernel - Re: [PATCH v6 05/10] PCI/AER: Apply function level reset to RCiEP on fatal error

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Date:   Fri, 25 Sep 2020 15:54:19 -0700
From:   "Sean V Kelley" <sean.v.kelley@...el.com>
To:     "Bjorn Helgaas" <helgaas@...nel.org>
Cc:     "Sean V Kelley" <seanvk.dev@...gontracks.org>, bhelgaas@...gle.com,
        Jonathan.Cameron@...wei.com, rafael.j.wysocki@...el.com,
        ashok.raj@...el.com, tony.luck@...el.com,
        sathyanarayanan.kuppuswamy@...el.com, qiuxu.zhuo@...el.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 05/10] PCI/AER: Apply function level reset to RCiEP on
 fatal error

On 25 Sep 2020, at 14:58, Bjorn Helgaas wrote:

> On Tue, Sep 22, 2020 at 02:38:54PM -0700, Sean V Kelley wrote:
>> From: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>>
>> Attempt to do function level reset for an RCiEP associated with an
>> RCEC device on fatal error.
>>
>> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>> ---
>>  drivers/pci/pcie/err.c | 31 ++++++++++++++++++++++---------
>>  1 file changed, 22 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> index e575fa6cee63..5380ecc41506 100644
>> --- a/drivers/pci/pcie/err.c
>> +++ b/drivers/pci/pcie/err.c
>> @@ -169,6 +169,17 @@ static void pci_bridge_walk(struct pci_dev 
>> *bridge, int (*cb)(struct pci_dev *,
>>  		cb(bridge, userdata);
>>  }
>>
>> +static pci_ers_result_t flr_on_rciep(struct pci_dev *dev)
>> +{
>> +	if (!pcie_has_flr(dev))
>> +		return PCI_ERS_RESULT_NONE;
>> +
>> +	if (pcie_flr(dev))
>> +		return PCI_ERS_RESULT_DISCONNECT;
>> +
>> +	return PCI_ERS_RESULT_RECOVERED;
>> +}
>
> Either we reset the device or we didn't; there is no third option.
>
> If I read it correctly, nothing in pcie_do_recovery() cares about the
> difference between PCI_ERS_RESULT_NONE and PCI_ERS_RESULT_DISCONNECT.
> The status does get returned, but only edr_handle_event() looks at it,
> and it doesn't care about the difference either.
>
> So I think this should just return PCI_ERS_RESULT_RECOVERED or
> PCI_ERS_RESULT_DISCONNECT.

You raise a good point. As currently implemented, the usage requires 
either a reset or not result. Will change.

Thanks,

Sean

>
>>  pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>>  			pci_channel_state_t state,
>>  			pci_ers_result_t (*reset_subordinate_devices)(struct pci_dev 
>> *pdev))
>> @@ -195,15 +206,17 @@ pci_ers_result_t pcie_do_recovery(struct 
>> pci_dev *dev,
>>  	if (state == pci_channel_io_frozen) {
>>  		pci_bridge_walk(bridge, report_frozen_detected, &status);
>>  		if (type == PCI_EXP_TYPE_RC_END) {
>> -			pci_warn(dev, "link reset not possible for RCiEP\n");
>> -			status = PCI_ERS_RESULT_NONE;
>> -			goto failed;
>> -		}
>> -
>> -		status = reset_subordinate_devices(bridge);
>> -		if (status != PCI_ERS_RESULT_RECOVERED) {
>> -			pci_warn(dev, "subordinate device reset failed\n");
>> -			goto failed;
>> +			status = flr_on_rciep(dev);
>> +			if (status != PCI_ERS_RESULT_RECOVERED) {
>> +				pci_warn(dev, "function level reset failed\n");
>> +				goto failed;
>> +			}
>> +		} else {
>> +			status = reset_subordinate_devices(bridge);
>> +			if (status != PCI_ERS_RESULT_RECOVERED) {
>> +				pci_warn(dev, "subordinate device reset failed\n");
>> +				goto failed;
>> +			}
>>  		}
>>  	} else {
>>  		pci_bridge_walk(bridge, report_normal_detected, &status);
>> -- 
>> 2.28.0
>>