How to set OpenSBI kernel command line argument with Buildroot

How can kernel command line arguments be set when using the OpenSBI bootloader in Buildroot? I want to set the isolcpus argument.

I don't think OpenSBI is even able to boot Linux. Typically, there will be a full-fledged boot loader, e.g. U-Boot, that loads Linux and sets the command line.

If OpenSBI is able to load Linux after all, here are a few ways that the command line can be set.

• In the device tree, set the bootargs property (at the top level) to the kernel command line you want.
• In the Linux kernel configuration, set CONFIG_CMDLINE (and probably enable CONFIG_CMDLINE_EXTEND).