/kern/xen in domU?

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

I've been tracing through what needs to be done to make NetBSD as a PV 
guest to present its capabilities correctly to XenServer for the purposes 
of network throughput, migration, suspend, memory ballooning, etc.

The Linux VM tools manipulate xenstore to do this. So first they get the 
local domid:
linux:~# xenstore-read domid
31

and then store things back such as local IP address and version of the 
tools installed:

linux:~# xenstore-ls /local/domain/31/attr
eth0 = ""
 ip = "192.168.1.108"
PVAddons = ""
 MajorVersion = "5"
 MinorVersion = "6"
 MicroVersion = "100"
 BuildVersion = "39153"
 Installed = "1"

On Linux the xenstore-* tools use /proc/xen and the guest can only 
manipulate its own domain details:
linux:~# xenstore-ls /local
xenstore-ls: xs_directory (/local): Permission denied

On a NetBSD guest, I installed xentools33 to give me the relevant xenstore 
tools and libraries, but /kern/xen doesn't exist on NetBSD as a domU. 
Indeed, xenbus_probe_init() explicitly skips setting it up unless DOM0OPS 
is set.

Any reason for this restriction?

--
Stephen