linux-kernel - Re: [PATCH v3 1/2] PCI/AER: Fix missing uevent on recovery when a reset is requested

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Message-ID: <4969c441-fe2a-470f-9efd-4661efca56ec@linux.intel.com>
Date: Thu, 31 Jul 2025 10:04:38 -0700
From: Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>
To: Lukas Wunner <lukas@...ner.de>, Niklas Schnelle <schnelle@...ux.ibm.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
 Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
 Linas Vepstas <linasvepstas@...il.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Manivannan Sadhasivam <mani@...nel.org>,
 Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
 Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
 Alexander Gordeev <agordeev@...ux.ibm.com>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>,
 Peter Oberparleiter <oberpar@...ux.ibm.com>,
 Matthew Rosato <mjrosato@...ux.ibm.com>, Oliver O'Halloran
 <oohall@...il.com>, Sinan Kaya <okaya@...nel.org>,
 linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
 Keith Busch <kbusch@...nel.org>
Subject: Re: [PATCH v3 1/2] PCI/AER: Fix missing uevent on recovery when a
 reset is requested


On 7/31/25 6:01 AM, Lukas Wunner wrote:
> On Wed, Jul 30, 2025 at 10:24:07PM +0200, Lukas Wunner wrote:
>> On Wed, Jul 30, 2025 at 10:01:50PM +0200, Lukas Wunner wrote:
>>> On Wed, Jul 30, 2025 at 01:20:57PM +0200, Niklas Schnelle wrote:
>>>> Since commit 7b42d97e99d3 ("PCI/ERR: Always report current recovery
>>>> status for udev") AER uses the result of error_detected() as parameter
>>>> to pci_uevent_ers(). As pci_uevent_ers() however does not handle
>>>> PCI_ERS_RESULT_NEED_RESET this results in a missing uevent for the
>>>> beginning of recovery if drivers request a reset. Fix this by treating
>>>> PCI_ERS_RESULT_NEED_RESET as beginning recovery.
>>> [...]
>>>> +++ b/drivers/pci/pci-driver.c
>>>> @@ -1592,6 +1592,7 @@ void pci_uevent_ers(struct pci_dev *pdev, enum pci_ers_result err_type)
>>>>   	switch (err_type) {
>>>>   	case PCI_ERS_RESULT_NONE:
>>>>   	case PCI_ERS_RESULT_CAN_RECOVER:
>>>> +	case PCI_ERS_RESULT_NEED_RESET:
>>>>   		envp[idx++] = "ERROR_EVENT=BEGIN_RECOVERY";
>>>>   		envp[idx++] = "DEVICE_ONLINE=0";
>>>>   		break;
>>> I note that PCI_ERS_RESULT_NO_AER_DRIVER is also missing in that
>>> switch/case statement.  I guess for the patch to be complete,
>>> it needs to be added to the PCI_ERS_RESULT_DISCONNECT case.
>>> Do you agree?
>> I realize now there's a bigger problem here:  In pcie_do_recovery(),
>> when control reaches the "failed:" label, a uevent is only signaled
>> for the *bridge*.  Shouldn't a uevent instead be signaled for every
>> device *below* the bridge?  (And possibly the bridge itself if it was
>> the device reporting the error.)
> The small patch below should resolve this issue.
> Please let me know what you think.
>
>> In that case you don't need to add PCI_ERS_RESULT_NO_AER_DRIVER to
>> the switch/case statement because we wouldn't want to have multiple
>> uevents reporting disconnect, so the one emitted below the "failed:"
>> label would be sufficient.
> I'll send a separate Reviewed-by for your original patch as the small
> patch below should resolve my concern about PCI_ERS_RESULT_NO_AER_DRIVER.
>
>> This all looks so broken that I'm starting to wonder if there's any
>> user space application at all that takes advantage of these uevents?
> I'd still be interested to know which user space application you're
> using to track these uevents?
>
> Thanks,
>
> Lukas
>
> -- >8 --
>
> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> index e795e5ae..3a95aa2 100644
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -165,6 +165,12 @@ static int report_resume(struct pci_dev *dev, void *data)
>   	return 0;
>   }
>   
> +static int report_disconnect(struct pci_dev *dev, void *data)
> +{
> +	pci_uevent_ers(dev, PCI_ERS_RESULT_DISCONNECT);
> +	return 0;
> +}

Since you are notifying the user space, I am wondering whether the drivers
should be notified about the recovery failure?

> +
>   /**
>    * pci_walk_bridge - walk bridges potentially AER affected
>    * @bridge:	bridge which may be a Port, an RCEC, or an RCiEP
> @@ -272,7 +278,7 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>   failed:
>   	pci_walk_bridge(bridge, pci_pm_runtime_put, NULL);
>   
> -	pci_uevent_ers(bridge, PCI_ERS_RESULT_DISCONNECT);
> +	pci_walk_bridge(bridge, report_disconnect, NULL);
>   
>   	pci_info(bridge, "device recovery failed\n");
>   
>
-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer