Skiboot/NVRAM

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Known NVRAM settings in Skiboot

A loose collection of known NVRAM settings in Skiboot. These should eventually be exposed via the Petiboot TUI.

To query the state of these settings, execute the following from the petitboot shell, or from a host OS with the nvram utility installed:

nvram -p ibm,skiboot --print-config

pcie-max-link-speed

Description

PCIe Link Speed Cap

Details

To cap the link speed, change the "pcie-max-link-speed" variable to the maximum generation you want to support and re-IPL the machine. For instance, to cap at PCIe Generation 3, in the petitboot command line type:

nvram -p ibm,skiboot --update-config pcie-max-link-speed=3

bootargs

Description

Skiroot kernel command line parameters

Details

Controls the arguments passed to the skiroot kernel. For example, to prevent petitboot from appearing on the AST video output and prefer another GPU if available:

nvram -p ibm,skiboot --update-config bootargs='modprobe.blacklist=ast'