Neat! This was the original linuxbios model from 1999: kernel + minimal initramfs in flash, so it's nice to see it coming back.
I've got something similar too, save the userland is not petitboot (I no longer want to use C for user mode code) but Go. It's also bigger than I'd like (about the size of the petitboot) but the security folks I talk to like the fact that I use Go, not C. It's at github.com/u-root/u-root. In one mode u-root is a combined binary, using a tool that rewrites all the individual Go tools into one tool; in another mode, the only user mode binary in flash is the go toolchain, and programs are compiled on demand into a tmpfs. Go is fast enough to make that first compile painless. In this second mode, the scripting language is also Go.
It's really nice to see projects using coreboot going back to putting a real kernel in the flash. Back at Los Alamos we put linux, Plan 9, and even some hypervisors in flash and enjoyed the flexibility it got us. We had many thousand HPC nodes running with this model. It's not just consumer, although there are linuxbios-based consumer systems too.
With a big enough flash the recovery and reflash is easy; you have a fallback kernel/initramfs just as you have a fallback coreboot. I learned the value of this the day I flash 1023 nodes with a bad image.
Thanks Arthur, that's neat stuff!
ron