linux-kernel - Re: [PATCH v9 10/15] PCI/ERR: Limit AER resets in pcie_do

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Date:   Fri, 16 Oct 2020 10:36:19 -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 v9 10/15] PCI/ERR: Limit AER resets in pcie_do_recovery()

On 16 Oct 2020, at 10:22, Bjorn Helgaas wrote:

> On Thu, Oct 15, 2020 at 05:11:08PM -0700, Sean V Kelley wrote:
>> From: Sean V Kelley <sean.v.kelley@...el.com>
>>
>> In some cases a bridge may not exist as the hardware controlling may 
>> be
>> handled only by firmware and so is not visible to the OS. This 
>> scenario is
>> also possible in future use cases involving non-native use of RCECs 
>> by
>> firmware.
>>
>> Explicitly apply conditional logic around these resets by limiting 
>> them to
>> Root Ports and Downstream Ports.
>>
>> Link: 
>> https://lore.kernel.org/r/20201002184735.1229220-8-seanvk.dev@oregontracks.org
>> Signed-off-by: Sean V Kelley <sean.v.kelley@...el.com>
>> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
>> Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>> ---
>>  drivers/pci/pcie/err.c | 31 +++++++++++++++++++++++++------
>>  1 file changed, 25 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> index 8b53aecdb43d..7883c9791562 100644
>> --- a/drivers/pci/pcie/err.c
>> +++ b/drivers/pci/pcie/err.c
>> @@ -148,13 +148,17 @@ static int report_resume(struct pci_dev *dev, 
>> void *data)
>>
>>  /**
>>   * pci_walk_bridge - walk bridges potentially AER affected
>> - * @bridge:	bridge which may be a Port
>> + * @bridge:	bridge which may be a Port, an RCEC with associated 
>> RCiEPs,
>> + *		or an RCiEP associated with an RCEC
>>   * @cb:		callback to be called for each device found
>>   * @userdata:	arbitrary pointer to be passed to callback
>>   *
>>   * If the device provided is a bridge, walk the subordinate bus, 
>> including
>>   * any bridged devices on buses under this bus.  Call the provided 
>> callback
>>   * on each device found.
>> + *
>> + * If the device provided has no subordinate bus, call the callback 
>> on the
>> + * device itself.
>>   */
>>  static void pci_walk_bridge(struct pci_dev *bridge,
>>  			    int (*cb)(struct pci_dev *, void *),
>> @@ -162,6 +166,8 @@ static void pci_walk_bridge(struct pci_dev 
>> *bridge,
>>  {
>>  	if (bridge->subordinate)
>>  		pci_walk_bus(bridge->subordinate, cb, userdata);
>> +	else
>> +		cb(bridge, userdata);
>
> Looks like *this* is the patch where the "no subordinate bus" case
> becomes possible?  If you agree, I can just move the test here, no
> need to repost.

Agree, this is the patch that the check is needed as we are opening 
things up for walking RC_ECs and RC_ENDs as below.

Sean


>
>>  }
>>
>>  pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>> @@ -174,10 +180,13 @@ pci_ers_result_t pcie_do_recovery(struct 
>> pci_dev *dev,
>>
>>  	/*
>>  	 * Error recovery runs on all subordinates of the bridge.  If the
>> -	 * bridge detected the error, it is cleared at the end.
>> +	 * bridge detected the error, it is cleared at the end.  For RCiEPs
>> +	 * we should reset just the RCiEP itself.
>>  	 */
>>  	if (type == PCI_EXP_TYPE_ROOT_PORT ||
>> -	    type == PCI_EXP_TYPE_DOWNSTREAM)
>> +	    type == PCI_EXP_TYPE_DOWNSTREAM ||
>> +	    type == PCI_EXP_TYPE_RC_EC ||
>> +	    type == PCI_EXP_TYPE_RC_END)
>>  		bridge = dev;
>>  	else
>>  		bridge = pci_upstream_bridge(dev);
>> @@ -185,6 +194,12 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev 
>> *dev,
>>  	pci_dbg(bridge, "broadcast error_detected message\n");
>>  	if (state == pci_channel_io_frozen) {
>>  		pci_walk_bridge(bridge, report_frozen_detected, &status);
>> +		if (type == PCI_EXP_TYPE_RC_END) {
>> +			pci_warn(dev, "subordinate device reset not possible for 
>> RCiEP\n");
>> +			status = PCI_ERS_RESULT_NONE;
>> +			goto failed;
>> +		}
>> +
>>  		status = reset_subordinates(bridge);
>>  		if (status != PCI_ERS_RESULT_RECOVERED) {
>>  			pci_warn(bridge, "subordinate device reset failed\n");
>> @@ -217,9 +232,13 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev 
>> *dev,
>>  	pci_dbg(bridge, "broadcast resume message\n");
>>  	pci_walk_bridge(bridge, report_resume, &status);
>>
>> -	if (pcie_aer_is_native(bridge))
>> -		pcie_clear_device_status(bridge);
>> -	pci_aer_clear_nonfatal_status(bridge);
>> +	if (type == PCI_EXP_TYPE_ROOT_PORT ||
>> +	    type == PCI_EXP_TYPE_DOWNSTREAM ||
>> +	    type == PCI_EXP_TYPE_RC_EC) {
>> +		if (pcie_aer_is_native(bridge))
>> +			pcie_clear_device_status(bridge);
>> +		pci_aer_clear_nonfatal_status(bridge);
>> +	}
>>  	pci_info(bridge, "device recovery successful\n");
>>  	return status;
>>
>> -- 
>> 2.28.0
>>