FYI. Long ago we discussed key value approach on top of virtio-serial.

-------- Original Message --------
Subject: [PATCH]: An implementation of HyperV  KVP  functionality
Date: Thu, 11 Nov 2010 13:03:10 -0700
From: Ky Srinivasan <ksrinivasan@novell.com>
To: <devel@driverdev.osuosl.org>, <Virtualization@lists.osdl.org>
CC: Haiyang Zhang <haiyangz@microsoft.com>, Greg KH <gregkh@suse.de>

I am enclosing a patch that implements the KVP (Key Value Pair) 
functionality for Linux guests on HyperV. This functionality allows 
Microsoft Management stack to query information from the guest. This 
functionality is implemented in two parts: (a) A kernel component that 
communicates with the host and (b) A user level daemon that implements 
data gathering. The attached patch (kvp.patch) implements the kernel 
component. I am also attaching the code for the user-level daemon 
(kvp_daemon.c)  for reference.

Regards,

K. Y