linux-kernel - Re: [PATCH] PCI/AER: Add option to panic on unrecoverable errors

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Message-ID: <20260206185232.GA70936@bhelgaas>
Date: Fri, 6 Feb 2026 12:52:32 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Breno Leitao <leitao@...ian.org>
Cc: Jonathan Corbet <corbet@....net>,
	Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
	Oliver O'Halloran <oohall@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, kbusch@...nel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
	dcostantino@...a.com, rneu@...a.com, kernel-team@...a.com
Subject: Re: [PATCH] PCI/AER: Add option to panic on unrecoverable errors

On Fri, Feb 06, 2026 at 10:23:11AM -0800, Breno Leitao wrote:
> When a device lacks an error_detected callback, AER recovery fails and
> the device is left in a disconnected state. This can mask serious
> hardware issues during development and testing.
> 
> Add a module parameter 'aer_unrecoverable_fatal' that panics the kernel
> instead, making such failures immediately visible. The parameter
> defaults to false to preserve existing behavior.
> 
> Signed-off-by: Breno Leitao <leitao@...ian.org>
> ---
> In environments where all hardware must be fully operational, silently
> leaving a device in a disconnected state after an AER recovery failure
> is unacceptable. This is common in high-reliability systems, production
> servers, and testing infrastructure where a degraded system should not
> continue running.
> 
> This patch adds a module parameter that allows administrators to enforce
> a strict policy: if a device cannot recover from an AER error, the
> kernel panics instead of continuing with degraded hardware. This ensures
> that hardware failures are immediately visible and can trigger
> appropriate remediation (restart, failover, alerting).
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++
>  drivers/pci/pcie/err.c                          | 3 +++
>  drivers/pci/pcie/portdrv.c                      | 7 +++++++
>  drivers/pci/pcie/portdrv.h                      | 1 +
>  4 files changed, 20 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 1058f2a6d6a8c..ff95c24280e3c 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -5240,6 +5240,15 @@ Kernel parameters
>  		nomsi	Do not use MSI for native PCIe PME signaling (this makes
>  			all PCIe root ports use INTx for all services).
>  
> +	pcieportdrv.aer_unrecoverable_fatal=
> +			[PCIE] Panic on unrecoverable AER errors:
> +		0	Log the error and leave the device in a disconnected
> +			state (default).
> +		1	Panic the kernel when a device cannot recover from an
> +			AER error (no error_detected callback). Useful for
> +			high-reliability systems where degraded hardware is
> +			unacceptable.

Just from an overall complexity point of view, I'm a little hesitant
to add new kernel parameters because this seems like a very specific
case.

Is there anything we could do to improve the logging to make the issue
more recognizable?  I assume you already look for KERN_CRIT, KERN_ERR,
etc., but it looks like the current message is just KERN_INFO.  I
think we could make a good case for at least KERN_WARNING.

But I guess you probably want something that's just impossible to
ignore.

Are there any other similar flags you already use that we could
piggy-back on?  E.g., if we raised the level to KERN_WARNING, maybe
the existing "panic_on_warn" would be enough?

> +++ b/drivers/pci/pcie/err.c
> @@ -73,6 +73,9 @@ static int report_error_detected(struct pci_dev *dev,
>  		if (dev->hdr_type != PCI_HEADER_TYPE_BRIDGE) {
>  			vote = PCI_ERS_RESULT_NO_AER_DRIVER;
>  			pci_info(dev, "can't recover (no error_detected callback)\n");
> +			if (aer_unrecoverable_fatal)
> +				panic("AER: %s: no error_detected callback\n",
> +				      pci_name(dev));
>  		} else {
>  			vote = PCI_ERS_RESULT_NONE;
>  		}