bhyve configuration changes up for review

[John Baldwin]

I have been toying with a new approach to managing bhyve's
internal configuration for a while.  Internally it stores a
little configuration "database" of key-value pairs that is
stored in a hierarchical tree (using nvlist).  One of the
ideas is that the configuration for a given device model
would consist of keys hung off of a node and the device init
routines would be passed a reference to that node and lookup
the desired keys as relative values.

There is more detail in the review, but I wanted to give a
heads up on the list as well in case folks would like to test
it.  I think comments on the design and other review notes
probably belong on the review rather than this thread.

Note that right now it only supports a simple flat config
file, but it should be quite possible to support a nicer
UCL config file syntax where the parser of that configuration
file sets a bunch of configuration variables just as the
parser of the flat config file does.  There might need to be
some additional logic for a nice UCL syntax for things like
choosing PCI slots if an explicit one isn't given, etc. but
that should be doable.

https://reviews.freebsd.org/D26035

-- 
John Baldwin