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: <aItpKIhYr0T8jf7A@wunner.de>
Date: Thu, 31 Jul 2025 15:01:28 +0200
From: Lukas Wunner <lukas@...ner.de>
To: 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 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;
+}
+
 /**
  * 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");