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Message-ID: <40cb885e-278a-43ee-a2ac-18c529256c45@linux.alibaba.com>
Date: Thu, 29 Jan 2026 13:49:58 +0800
From: Shuai Xue <xueshuai@...ux.alibaba.com>
To: Jonathan Cameron <jonathan.cameron@...wei.com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, bhelgaas@...gle.com, kbusch@...nel.org,
sathyanarayanan.kuppuswamy@...ux.intel.com, mahesh@...ux.ibm.com,
oohall@...il.com, terry.bowman@....com, tianruidong@...ux.alibaba.com,
lukas@...ner.de
Subject: Re: [PATCH v7 2/5] PCI/DPC: Run recovery on device that detected the
error
On 1/28/26 11:02 PM, Jonathan Cameron wrote:
> On Wed, 28 Jan 2026 20:27:31 +0800
> Shuai Xue <xueshuai@...ux.alibaba.com> wrote:
>
>> On 1/27/26 6:24 PM, Jonathan Cameron wrote:
>>> On Sat, 24 Jan 2026 15:45:54 +0800
>>> Shuai Xue <xueshuai@...ux.alibaba.com> wrote:
>>>
>>>> The current implementation of pcie_do_recovery() assumes that the
>>>> recovery process is executed for 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. When passing the error device, the
>>>> pcie_do_recovery() will find the upstream bridge and walk bridges
>>>> potentially AER affected. And subsequent commits will be able to
>>>> accurately access AER status of the error device.
>>>>
>>>> Should not observe any functional changes.
>>>>
>>>> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>>>> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
> Hi Shuai,
>
>>>> ---
>>>> drivers/pci/pci.h | 2 +-
>>>> drivers/pci/pcie/dpc.c | 25 +++++++++++++++++++++----
>>>> drivers/pci/pcie/edr.c | 7 ++++---
>>>> 3 files changed, 26 insertions(+), 8 deletions(-)
>>>>
> ...
>
>>>> -void dpc_process_error(struct pci_dev *pdev)
>>>> +/**
>>>> + * dpc_process_error - handle the DPC error status
>>>> + * @pdev: the port that experienced the containment event
>>>> + *
>>>> + * Return: the device that detected the error.
>>>> + *
>>>> + * NOTE: The device reference count is increased, the caller must decrement
>>>> + * the reference count by calling pci_dev_put().
>>>> + */
>>>> +struct pci_dev *dpc_process_error(struct pci_dev *pdev)
>>>
>>> Maybe it makes sense to carry the err_port naming for the pci_dev
>>> in here as well? Seems stronger than just relying on people
>>> reading the documentation you've added.
>>
>> Good point. I think renaming the parameter would improve clarity. However,
>> I'd prefer to handle it in a separate patch to keep this change focused on
>> the functional modification. Would that work for you?
>>
> Sure. Ideal would be a precursor patch, but if it's much easier to
> do on top of this I'm fine with that.
>
> You are absolutely correct that it should be a separate patch!
Got it.
>>>
>>>> {
>>>> u16 cap = pdev->dpc_cap, status, source, reason, ext_reason;
>>>> struct aer_err_info info = {};
>>>> + struct pci_dev *err_dev;
>>>>
>>>> pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
>>>>
>>>> @@ -279,6 +289,7 @@ void dpc_process_error(struct pci_dev *pdev)
>>>> pci_aer_clear_nonfatal_status(pdev);
>>>> pci_aer_clear_fatal_status(pdev);
>>>> }
>>>> + err_dev = pci_dev_get(pdev);
>>>> break;
>>>> case PCI_EXP_DPC_STATUS_TRIGGER_RSN_NFE:
>>>> case PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE:
>>>> @@ -290,6 +301,8 @@ void dpc_process_error(struct pci_dev *pdev)
>>>> "ERR_FATAL" : "ERR_NONFATAL",
>>>> pci_domain_nr(pdev->bus), PCI_BUS_NUM(source),
>>>> PCI_SLOT(source), PCI_FUNC(source));
>>>> + err_dev = pci_get_domain_bus_and_slot(pci_domain_nr(pdev->bus),
>>>> + PCI_BUS_NUM(source), source & 0xff);
>>>
>>> Bunch of replication in her with the pci_warn(). Maybe some local variables?
>>> Maybe even rebuild the final parameter from PCI_DEVFN(slot, func) just to make the
>>> association with the print really obvious?
>>
>> Agreed. Here's the improved version:
>>
>> --- a/drivers/pci/pcie/dpc.c
>> +++ b/drivers/pci/pcie/dpc.c
>> @@ -293,17 +293,28 @@ struct pci_dev *dpc_process_error(struct pci_dev *pdev)
>> break;
>> case PCI_EXP_DPC_STATUS_TRIGGER_RSN_NFE:
>> case PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE:
>> - pci_read_config_word(pdev, cap + PCI_EXP_DPC_SOURCE_ID,
>> - &source);
>> + {
>> + int domain, bus;
>> + u8 slot, func, devfn;
>> + const char *err_type;
>> +
>> + pci_read_config_word(pdev, cap + PCI_EXP_DPC_SOURCE_ID, &source);
>> +
>> + /* Extract source device location */
>> + domain = pci_domain_nr(pdev->bus);
>> + bus = PCI_BUS_NUM(source);
>> + slot = PCI_SLOT(source);
>> + func = PCI_FUNC(source);
>> + devfn = PCI_DEVFN(slot, func);
>> +
>> + err_type = (reason == PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE) ?
>> + "ERR_FATAL" : "ERR_NONFATAL";
>> +
>> pci_warn(pdev, "containment event, status:%#06x, %s received from %04x:%02x:%02x.%d\n",
>> - status,
>> - (reason == PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE) ?
>> - "ERR_FATAL" : "ERR_NONFATAL",
>> - pci_domain_nr(pdev->bus), PCI_BUS_NUM(source),
>> - PCI_SLOT(source), PCI_FUNC(source));
>> - err_dev = pci_get_domain_bus_and_slot(pci_domain_nr(pdev->bus),
>> - PCI_BUS_NUM(source), source & 0xff);
>> + status, err_type, domain, bus, slot, func);
>> + err_dev = pci_get_domain_bus_and_slot(domain, bus, devfn);
> Maybe don't bother with local variables for the things only used once.
> e.g.
>
> err_dev = pci_get_domain_bus_and_slot(domain, bus, PCI_DEVFN(slot, func));
>
> and possibly the same for err_type.
>
> I don't mind though if you prefer to use locals for everything.
Sure, will remove local devfn and err_type.
>
>
>
>> break;
>> + }
>> case PCI_EXP_DPC_STATUS_TRIGGER_RSN_IN_EXT:
>> ext_reason = status & PCI_EXP_DPC_STATUS_TRIGGER_RSN_EXT;
>> pci_warn(pdev, "containment event, status:%#06x: %s detected\n",
>>
>>>
>>> Is there any chance that this might return NULL? Feels like maybe that's
>>> only a possibility on a broken setup, but I'm not sure of all the wonderful
>>> races around hotplug and DPC occurring before the OS has caught up.
>>
>> Surprise Down events are handled separately in
>> dpc_handle_surprise_removal() and won't reach dpc_process_error().
>> Please correct me if I missed anything.
>
> Probably fine. I just didn't check particularly closely.
>
> Jonathan
Thanks for valuable comments.
Best Regards,
Shuai
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