On 08/07/2012 06:19 AM, Christian Borntraeger wrote:
> 2nd attempt, with mailing lists on cc....
> This patch reminded us of another thing that we have been working on.
> Here is a patch that sits in my patch queue and  disables usb for s390
> We have not pushed that patch yet, since several libvirt versions will always 
> specify -usb, which will then break. 

You are correct that older libvirt always specified -usb; but with the
upcoming libvirt 0.10.0, we have fixed things to now allow the user to
request starting without -usb.

> 
> So are there any opinions about handling the usb option for platforms that
> actually dont support it?

Libvirt should probably learn which platforms don't support it and
automatically omit the -usb without user intervention on those
platforms, but at least we have the fallback to explicitly avoid the
-usb now.  Knowing which platforms support usb might be easier if there
were some QMP query-* command that could be used to learn whether a
particular machine type supports it.  That is, since this series is
adding the new syntax '-machine type=pseries,usb=off', libvirt should be
able to query '-machine type=pseries,?' to see what options the given
machine has, and preferably through a QMP interface rather than through
the command line.

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org