On 08/21/2017 01:04 PM, Wuzongyong (Euler Dept) wrote: Usually libvirt features are request driven. In other words you seem to be the first to need this property exposed. And in generic case, it's questionable which properties should libvirt expose, and in what detail. Whether we want libvirt to be just XML -> cmd line compiler, or we want it to chose some sensible defaults and do something on the top of cmd line translation. Nope. It is not implemented yet. But if you want, you can post patches. BTW: it looks like the name changed from --max-ram-below-4g to --below-4g-mem-size. Michal