Re: [Libguestfs] [PATCH 7/7] v2v: add support for SUSE VMDP drivers

On Tue, 2016-04-05 at 16:16 +0300, Roman Kagan wrote: > On Tue, Apr 05, 2016 at 03:08:48PM +0200, Cedric Bosdonnat wrote: > > On Tue, 2016-04-05 at 15:52 +0300, Roman Kagan wrote: > > > On Tue, Apr 05, 2016 at 01:47:33PM +0200, Cédric Bosdonnat wrote: > > > > Note that VMDP's block driver pvvxblk depends on the ballooning > > > > driver > > > > pvvxbn. > > > > > > Can you please elaborate on this? Is the balloon driver *used* > > > by > > > the > > > storage driver so that the latter won't work without the former? That's correct. The current design requires that the balloon driver be loaded. The pvvxblk driver is a single binary that runs on both KVM and Xen. It determines at runtime which environment it is running on and acts accordingly. The dependency is required for Xen. This also creates the dependency for KVM. > > > What > > > will happen if the virtio-balloon device isn't configured in the > > > VM? The balloon driver will not load and hence the block driver will not load. > > It's just that without the virtio balloon driver installed, the > > virtio > > block one won't start properly, resulting in the famous 0x7B error. > > Does it also require the presence of the balloon device? Yes. This the default installation. The only way to remove the balloon device is to launch the vm by constructing a manually configured command line.

Weather the balloon device is present or not, the user is able to set the current and maximum memory allocations differently. If different and the balloon device/driver is not present, the vm will undoubtedly crash at some point.