Re: [libvirt] [PATCH 2/6] domain_conf: Add USB controler model "none"

On 07/10/2012 01:01 AM, Osier Yang wrote: It IS for back-compat reasons. We have been outputting '-usb' in the qemu command line for ages prior to 42043afcd, and need a way to explicitly omit the '-usb' in the command line. Older libvirt had no way to represent the implicit device, and the fix of 409b5f549 was more of a hack that said when migrating back to an older libvirt, the existing usb controller of the sending libvirt would be implicitly recreated by the receiving libvirt. If a user explicitly requests the 'none' controller, then we must ensure that migration to an older host fails up front; the 'none' element must be explicit because the absence of an element implies the default usb controller. Yes, just like it is a hard requirement that a user explicitly specifies the 'none' memoryballoon controller. That's the back-compat issue we have to face any time we make the XML explicit for something that older libvirt provided implicitly. This patch looks correct to me. -- Eric Blake eblake(a)redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org