Description

This article describes why MPC7e card may see this syslog message: 

fpc4 kern.warning kernel:pci 0000:05:00.0: can't set Max Payload Size to 256; if necessary, use "pci=pcie_bus_safe" and report a bug

This is only a kernel warning message, not an actual FPC major error. It is for informational/debug use and should not have any traffic/service effect.

Symptoms

Syslog messages seen with MPC7e model:

fpc4 kern.warning kernel:pci 0000:05:00.0: can't set Max Payload Size to 256; if necessary, use "pci=pcie_bus_safe" and report a bug

 

Solution

This issue applies to JUNOS release from 19.1 and MPC7e card (MPC7E 3D MRATE-12xQSFPP-XGE-XLGE-CGE):

Feb 15 18:15:03  mx960 fpc4 kern.notice kernel:Kernel command line: BOOT_IMAGE=/vmlinuz root=LABEL=root rw quiet console=ttyS0, 115200n8 memmap=512M$1G intel_iommu=off rw nopat isolcpus=1 pcie_aspm=off pcie_ports=native crashkernel=256M
Feb 15 18:15:17 mx960 fpc4 kern.warning kernel:pci 0000:05:00.0: can't set Max Payload Size to 256; if necessary, use "pci=pcie_bus_safe" and report a bug
Feb 15 18:15:17 mx960 fpc9 kern.warning kernel:pci 0000:05:00.0: can't set Max Payload Size to 256; if necessary, use "pci=pcie_bus_safe" and report a bug

The messages is from newer Linux kernel, which became more verbose. Peripheral Component Interconnect (PCI) is an interface that provides connectivity between the control (FPGA) and the Routing Engine in MX. So during the boot up phase, one of these variables are getting negotiated. But some of hardware components do not support a 256 byte max payload size config. Hence an attempt to set the payload size to 256 on these fails.

This is only a kernel warning message, not an actual FPC major error. It is for informational/debug use and should not have any traffic/service effect.

 

Modification History

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