On Fri, Dec 09, 2011 at 05:19:35PM +0530, Amit Shah wrote: > Hello, > > These patches make qemu generate an error on failure in setting a > balloon value: > > (qemu) balloon 400 > Device 'balloon' has not been activated > > This can happen when the guest hasn't yet loaded a balloon driver.
This is a pretty significant change in behaviour/semantics of the balloon driver interface. eg, when libvirt starts a guest, it launches QEMU paused, and immediately sets a balloon target, which may be lower than the memory limit, and then starts CPUS to let the guest boot. The guest will utilize this target when it loads the balloon driver during bootup. With this proposed change, libvirt will immediately get an error, and have to guess when the balloon driver might be loaded by the guest, in order to set the limit post-boot. > Previously, such a ballooning attempt didn't produce an error, but the > virtio-balloon driver remembered the value nevertheless, causing a > module load in the guest using the attempted balloon value > originally. This may not be the desired course of action. This is *exactly* desired behaviour. Please don't change this. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
