On Wed 19-07-17 20:01:18, Wei Wang wrote: > On 07/19/2017 04:13 PM, Michal Hocko wrote: [... > >All you should need is the check for the page reference count, no? I > >assume you do some sort of pfn walk and so you should be able to get an > >access to the struct page. > > Not necessarily - the guest struct page is not seen by the hypervisor. The > hypervisor only gets those guest pfns which are hinted as unused. From the > hypervisor (host) point of view, a guest physical address corresponds to a > virtual address of a host process. So, once the hypervisor knows a guest > physical page is unsued, it knows that the corresponding virtual memory of > the process doesn't need to be transferred in the 1st round. I am sorry, but I do not understand. Why cannot _guest_ simply check the struct page ref count and send them to the hypervisor? Is there any documentation which describes the workflow or code which would use your new API? -- Michal Hocko SUSE Labs
