Kernel prepatch 4.0-rc4

"Reasons why this should be done in the kernel, instead of userspace as
it is currently done today include the following:

* Performance: Fewer process context switches, fewer copies, fewer
syscalls, larger memory chunks via memfd.

* Security: The peers which communicate do not have to trust each
other, as the only trustworthy component in the game is the kernel

* More types of metadata can be attached to messages than in userspace

* Semantics for apps with heavy data payloads (media apps, for
instance) with optinal priority message dequeuing, and global
message ordering.

* Being in the kernel closes a lot of races which can't be fixed with
the current userspace solutions

* Eavesdropping on the kernel level, so privileged users can hook into
the message stream without hacking support for that into their
userspace processes

* dbus-daemon is not available during early-boot or shutdown."