I finally got around to slapping more hacky #ifdef's onto my vmm_clock [1] and virtio_vmmci [2] Linux kernel modules because I found older Linux kernel versions (~3.10 era) didn't support compiling them.
If you host things like CentOS 7 guests under vmm(4)/vmd(8), I recommend trying them out and opening a GitHub issue in the respective project if there's something wrong. (PR's welcome.) No idea what I'm talking about? * virtio_vmmci - Linux port of vmmci(4) that helps signal reboots/rtc sync with Linux guests via vmctl(8) and vmd(8). * vmm_clock - duct-taped version of kvmclock to work with vmm(4)'s pvclock(4) paravirtualized clock. -dv [1] https://github.com/voutilad/virtio_vmmci [2] https://github.com/voutilad/vmm_clock