Re: [PATCH v2] PCI/AER: Add error message when AER_MAX_MULTI_ERR_DEVICES limit is hit during AER handling

[Bjorn Helgaas <helgaas@kernel.org>]

On Fri, Jun 20, 2025 at 12:20:30AM +0530, Akshay Jindal wrote:
> When a PCIe error is detected, the root port receives the error message
> and the threaded IRQ handler, aer_isr, traverses the hierarchy downward
> from the root port. It populates the e_info->dev[] array with the PCIe
> devices that have recorded error status, so that appropriate error
> handling and recovery can be performed.
> 
> The e_info->dev[] array is limited in size by AER_MAX_MULTI_ERR_DEVICES,
> which is currently defined as 5. If more than five devices report errors
> in the same event, the array silently truncates the list, and those
> extra devices are not included in the recovery flow.
> 
> Emit an error message when this limit is reached, fulfilling a TODO
> comment in drivers/pci/pcie/aer.c.
> /* TODO: Should print error message here? */
> 
> Signed-off-by: Akshay Jindal <akshayaj.lkd@gmail.com>

Applied to pci/aer for v6.17, thanks!

> ---
> 
> Changes since v1:
> - Reworded commit message in imperative mood (per Shuah’s feedback)
> - Mentioned and quoted related TODO in the message
> - Updated recipient list
> 
> Testing:
> ========
> Verified log in dmesg on QEMU.
> 
> 1. Following command created the required environment. As mentioned below a
> pcie-root-port and a virtio-net-pci device are used on a Q35 machine model.
> ./qemu-system-x86_64 \
> 	-M q35,accel=kvm \
> 	-m 2G -cpu host -nographic \
> 	-serial mon:stdio \
> 	-kernel /home/akshayaj/pci/arch/x86/boot/bzImage \
> 	-initrd /home/akshayaj/Embedded_System_Using_QEMU/rootfs/rootfs.cpio.gz \
> 	-append "console=ttyS0 root=/ pci=pcie_scan_all" \
> 	-device pcie-root-port,id=rp0,chassis=1,slot=1 \
> 	-device virtio-net-pci,bus=rp0
> 
> ~ # mylspci -t
> -[0000:00]-+-00.0
>            +-01.0
>            +-02.0
>            +-03.0-[01]----00.0
>            +-1f.0
>            +-1f.2
>            \-1f.3
> 00:03.0--> pcie-root-port
> 
> 2. Kernel bzImage compiled with following changes:
> 	2.1 CONFIG_PCIEAER=y in config
> 	2.2 AER_MAX_MULTI_ERR_DEVICES set to 0
> 	Since there is no pcie-testdev in QEMU, it is impossible to create
> 	a 5-level hierarchy of PCIe devices in QEMU. So we simulate the
> 	error scenario by changing the limit to 0.
> 	2.3 Log added at the required place in aer.c.
> 
> 3. Both correctable and uncorrectable errors were injected on
> pcie-root-port via HMP command (pcie_aer_inject_error) in QEMU.
> HMP Command used are as follows:
> 	3.1 pcie_aer_inject_error -c rp0 0x1
> 	3.2 pcie_aer_inject_error -c rp0 0x40
> 	3.3 pcie_aer_inject_error rp0 0x10
> 
> Resulting dmesg:
> ================
> [    0.380534] pcieport 0000:00:03.0: AER: enabled with IRQ 24
> [   55.729530] pcieport 0000:00:03.0: AER: Exceeded max allowed (0) addition of PCIe devices for AER handling
> [  225.484456] pcieport 0000:00:03.0: AER: Exceeded max allowed (0) addition of PCIe devices for AER handling
> [  356.976253] pcieport 0000:00:03.0: AER: Exceeded max allowed (0) addition of PCIe devices for AER handling
> 
>  drivers/pci/pcie/aer.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 70ac66188367..3995a1db5699 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -1039,7 +1039,8 @@ static int find_device_iter(struct pci_dev *dev, void *data)
>  		/* List this device */
>  		if (add_error_device(e_info, dev)) {
>  			/* We cannot handle more... Stop iteration */
> -			/* TODO: Should print error message here? */
> +			pci_err(dev, "Exceeded max allowed (%d) addition of PCIe "
> +				"devices for AER handling\n", AER_MAX_MULTI_ERR_DEVICES);
>  			return 1;
>  		}
>  
> -- 
> 2.43.0
>