linux-kernel - Re: [PATCH v2 1/2] PCI/DPC: Run recovery on device that detected the error

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Message-ID: <3199a681-a31c-40c9-8a05-89cf38cd6eb8@linux.alibaba.com>
Date: Thu, 23 Jan 2025 15:03:03 +0800
From: Shuai Xue <xueshuai@...ux.alibaba.com>
To: Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>,
 linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, bhelgaas@...gle.com, kbusch@...nel.org
Cc: mahesh@...ux.ibm.com, oohall@...il.com
Subject: Re: [PATCH v2 1/2] PCI/DPC: Run recovery on device that detected the
 error



在 2025/1/23 12:53, Sathyanarayanan Kuppuswamy 写道:
> 
> On 11/12/24 5:54 AM, Shuai Xue wrote:
>> The current implementation of pcie_do_recovery() assumes that the
>> recovery process is executed on the device that detected the error.
>> However, the DPC driver currently passes the error port that experienced
>> the DPC event to pcie_do_recovery().
>>
>> Use the SOURCE ID register to correctly identify the device that detected the
>> error. By passing this error device to pcie_do_recovery(), subsequent
>> patches will be able to accurately access AER status of the error device.
> 
> When passing the error device, I assume pcie_do_recovery() will find the
> upstream bride and run the recovery logic .
> 

Yes, the pcie_do_recovery() will find the upstream bridge and walk bridges
potentially AER affected.

>>
>> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
>> ---
> 
> IMO, moving the "err_port" rename to a separate patch will make this change
> more clear.  But it is up to you.

I see, I will add a separate patch.

> 
>>   drivers/pci/pci.h      |  2 +-
>>   drivers/pci/pcie/dpc.c | 30 ++++++++++++++++++++++++------
>>   drivers/pci/pcie/edr.c | 35 ++++++++++++++++++-----------------
>>   3 files changed, 43 insertions(+), 24 deletions(-)
>>
>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>> index 14d00ce45bfa..0866f79aec54 100644
>> --- a/drivers/pci/pci.h
>> +++ b/drivers/pci/pci.h
>> @@ -521,7 +521,7 @@ struct rcec_ea {
>>   void pci_save_dpc_state(struct pci_dev *dev);
>>   void pci_restore_dpc_state(struct pci_dev *dev);
>>   void pci_dpc_init(struct pci_dev *pdev);
>> -void dpc_process_error(struct pci_dev *pdev);
>> +struct pci_dev *dpc_process_error(struct pci_dev *pdev);
>>   pci_ers_result_t dpc_reset_link(struct pci_dev *pdev);
>>   bool pci_dpc_recovered(struct pci_dev *pdev);
>>   #else
>> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
>> index 2b6ef7efa3c1..62a68cde4364 100644
>> --- a/drivers/pci/pcie/dpc.c
>> +++ b/drivers/pci/pcie/dpc.c
>> @@ -257,10 +257,17 @@ static int dpc_get_aer_uncorrect_severity(struct pci_dev *dev,
>>       return 1;
>>   }
>> -void dpc_process_error(struct pci_dev *pdev)
>> +/**
>> + * dpc_process_error - handle the DPC error status
> 
> Handling the DPC error status has nothing to do with finding
> the error source. Why not add a new helper function?

As PCIe Spec,

     DPC Error Source ID - When the DPC Trigger Reason field indicates that DPC
     was triggered due to the reception of an ERR_NONFATAL or ERR_FATAL, this
     register contains the Requester ID of the received Message. Otherwise, the
     value of this register is undefined.

To find the error source, we need to

   - check the error reason from PCI_EXP_DPC_STATUS,
   - Identify the error device by PCI_EXP_DPC_SOURCE_ID for ERR_NONFATAL and
     ERR_FATAL reason.

The code will duplicate with dpc_process_error. Therefore, I directly reused
dpc_process_error.

> 
>> + * @pdev: the port that experienced the containment event
>> + *
>> + * Return the device that experienced the error.
> detected the error?

Will change it.

>> + */
>> +struct pci_dev *dpc_process_error(struct pci_dev *pdev)
>>   {
>>       u16 cap = pdev->dpc_cap, status, source, reason, ext_reason;
>>       struct aer_err_info info;
>> +    struct pci_dev *err_dev = NULL;
> 
> I don't think you need NULL initialization here.

Will remove it.

> 
>>       pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
>>       pci_read_config_word(pdev, cap + PCI_EXP_DPC_SOURCE_ID, &source);
>> @@ -283,6 +290,13 @@ void dpc_process_error(struct pci_dev *pdev)
>>            "software trigger" :
>>            "reserved error");
>> +    if (reason == PCI_EXP_DPC_STATUS_TRIGGER_RSN_NFE ||
>> +        reason == PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE)
>> +        err_dev = pci_get_domain_bus_and_slot(pci_domain_nr(pdev->bus),
>> +                        PCI_BUS_NUM(source), source & 0xff);
>> +    else
>> +        err_dev = pci_dev_get(pdev);
>> +
>>       /* show RP PIO error detail information */
>>       if (pdev->dpc_rp_extensions &&
>>           reason == PCI_EXP_DPC_STATUS_TRIGGER_RSN_IN_EXT &&
>> @@ -295,6 +309,8 @@ void dpc_process_error(struct pci_dev *pdev)
>>           pci_aer_clear_nonfatal_status(pdev);
>>           pci_aer_clear_fatal_status(pdev);
>>       }
>> +
>> +    return err_dev;
>>   }
>>   static void pci_clear_surpdn_errors(struct pci_dev *pdev)
>> @@ -350,21 +366,23 @@ static bool dpc_is_surprise_removal(struct pci_dev *pdev)
>>   static irqreturn_t dpc_handler(int irq, void *context)
>>   {
>> -    struct pci_dev *pdev = context;
>> +    struct pci_dev *err_port = context, *err_dev = NULL;
> 
> NULL initialization is not needed.

Will remove it.

Thanks for valuable comments.

Best Regards,
Shuai