The pi4 kernel on 9p.io is now more complete, with support for SD card (which was pleasantly standards-conforming), and ethernet (thanks to cinap). USB3 still missing, so useful only as a cpu server.
On a pi4 with 4GB RAM, only 2GB will be accessible until we have a proper implementation of kmap(). For convenience there's a bootable 9pi4cpu binary in /contrib/miller. Needs firmware from 5 July 2019 or later. config.txt for pi4 should 'core_freq=250' and 'device_tree='
