linux-kernel - Re: [BUG] pci: nwl: Unhandled AER correctable error

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Message-ID: <23d9f128-af95-41b1-a5b9-3c69d2df8ab8@linux.dev>
Date: Mon, 4 Aug 2025 18:10:48 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Krzysztof Wilczyński <kw@...ux.com>,
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 linux-pci@...r.kernel.org, Rob Herring <robh@...nel.org>,
 Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
 Oliver O'Halloran <oohall@...il.com>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Michal Simek <michal.simek@....com>, Brian Norris
 <briannorris@...omium.org>, Minghuan Lian <minghuan.Lian@....com>,
 Mingkai Hu <mingkai.hu@....com>, Roy Zang <roy.zang@....com>,
 Frank Li <Frank.Li@....com>, Hou Zhiqiang <Zhiqiang.Hou@....com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG] pci: nwl: Unhandled AER correctable error

On 8/4/25 16:57, Bjorn Helgaas wrote:
> [+cc more folks who might be interested in AER with non-standard
> interrupts]
> 
> On Fri, Aug 01, 2025 at 01:43:19PM -0400, Sean Anderson wrote:
>> Hi,
>> 
>> AER correctable errors are pretty rare. I only saw one once before and
>> came up with commit 78457cae24cb ("PCI: xilinx-nwl: Rate-limit misc
>> interrupt messages") in response. I saw another today and,
>> unfortunately, clearing the correctable AER bit in MSGF_MISC_STATUS is
>> not sufficient to handle the IRQ. It gets immediately re-raised,
>> preventing the system from making any other progress. I suspect that it
>> needs to be cleared in PCI_ERR_ROOT_STATUS. But since the AER IRQ never
>> gets delivered to aer_irq, those registers never get tickled.
>> 
>> The underlying problem is that pcieport thinks that the IRQ is going to
>> be one of the MSIs or a legacy interrupt, but it's actually a native
>> interrupt:
>> 
>>            CPU0       CPU1       CPU2       CPU3       
>>  42:          0          0          0          0     GICv2 150 Level     nwl_pcie:misc
>>  45:          0          0          0          0  nwl_pcie:legacy   0 Level     PCIe PME, aerdrv
>>  46:         25          0          0          0  nwl_pcie:msi 524288 Edge      nvme0q0
>>  47:          0          0          0          0  nwl_pcie:msi 524289 Edge      nvme0q1
>>  48:          0          0          0          0  nwl_pcie:msi 524290 Edge      nvme0q2
>>  49:         46          0          0          0  nwl_pcie:msi 524291 Edge      nvme0q3
>>  50:          0          0          0          0  nwl_pcie:msi 524292 Edge      nvme0q4
>> 
>> In the above example, AER errors will trigger interrupt 42, not 45.
>> Actually, there are a bunch of different interrupts in MSGF_MISC_STATUS,
>> so maybe nwl_pcie_misc_handler should be an interrupt controller
>> instead? But even then pcie_port_enable_irq_vec() won't figure out the
>> correct IRQ. Any ideas on how to fix this?
>> 
>> Additionally, any tips on actually triggering AER/PME stuff in a
>> consistent way? Are there any off-the-shelf cards for sending weird PCIe
>> stuff over a link for testing? Right now all I have 
> 
> This is definitely a problem.  We have had some discussion about this
> in the past, but haven't quite achieved critical mass to solve this in
> a generic way.  Here are some links:
> 
>   https://lore.kernel.org/linux-pci/20250702223841.GA1905230@bhelgaas/t/#u
>   https://lore.kernel.org/linux-pci/1464242406-20203-1-git-send-email-po.liu@nxp.com/

Thanks for the links. Toggling PERST does seem to reliably cause
correctable errors (however "correctable" they may actually be in
practice). With the patch I posted on the other branch of this chain I
now get

[   43.041610] pcieport 0000:00:00.0: AER: Multiple Corrected error message received from 0000:00:00.0
[   43.050693] pcieport 0000:00:00.0: PCIe Bus Error: severity=Corrected, type=Physical Layer, (Receiver ID)
[   43.061477] pcieport 0000:00:00.0:   device [10ee:d011] error status/mask=00000001/0000e000
[   43.069842] pcieport 0000:00:00.0:    [ 0] RxErr                 

Whether or not that's the right fix, at least I can test things :)

--Sean