On 06/12/2017 09:28 AM, Michael S. Tsirkin wrote: > >> The hypervisor is going to throw away the contents of these pages, >> right? > It should be careful and only throw away contents that was there before > report_unused_page_block was invoked. Hypervisor is responsible for not > corrupting guest memory. But that's not something an mm patch should > worry about. That makes sense. I'm struggling to imagine how the hypervisor makes use of this information, though. Does it make the pages read-only before this, and then it knows if there has not been a write *and* it gets notified via this new mechanism that it can throw the page away?