port-xen/47899: xen block script does not create vnd devices when needed.

[7heo%7heo.tk@localhost]

>Number:         47899
>Category:       port-xen
>Synopsis:       xen block script does not create vnd devices when needed.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-xen-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jun 05 20:30:00 +0000 2013
>Originator:     7heo
>Release:        6.0.1
>Organization:
>Environment:
NetBSD host.domain.com 6.0.1 NetBSD 6.0.1 (XEN3PAE_DOM0) i386
>Description:
By default, NetBSD has 4 (four) vnd devices, /dev/vnd0, /dev/vnd1, /dev/vnd2 
and /dev/vnd3.

When one creates a virtual machine with a disk from a file, the block script 
uses vnconfig to "mount" the image on a vnd loopback device.

When the Xen toolstack (xm) needs to mount more than 4 images at the same time, 
it fails, instead of increasing the number of vnd devices to a suited quantity.

The error message looks like:

"Error: Device <nr> (vbd) could not be connected. Hotplug scripts not working."

and does not give any valuable input on the real reason behind the problem.
>How-To-Repeat:
Install NetBSD, install Xen, create a virtual machine with 5 drives.
>Fix:
$ cd /dev
$ ./MAKEDEV vnd4
$ ./MAKEDEV vnd...
$ xm start /path/to/domain.cfg