As part of the work for 2.5 we made some changes in order to move the bootloader configuration out to separate recipes (grub-bootconf and systemd-bootconf); at least systemd-bootconf is reading the APPEND variable which is used to set the kernel command line. Unfortunately this is problematic in that the previous assumption was that APPEND was only read in the image context (and therefore could be effectively set from there). The following change is an example:

  http://cgit.openembedded.org/openembedded-core/commit/?id=cfc09de06ecc12bb42181004689e881c75072665

Cal suggested that the separate configuration wasn't used by default and thus this shouldn't be a major problem yet - I wasn't clear on the details though.

Somehow this needs to be reconciled.