On 03.04.19 10:12, Michal Hocko wrote: > On Wed 03-04-19 10:01:16, Oscar Salvador wrote: >> On Tue, Apr 02, 2019 at 02:48:45PM +0200, Michal Hocko wrote: >>> So what is going to happen when you hotadd two memblocks. The first one >>> holds memmaps and then you want to hotremove (not just offline) it? >> >> If you hot-add two memblocks, this means that either: >> >> a) you hot-add a 256MB-memory-device (128MB per memblock) >> b) you hot-add two 128MB-memory-device >> >> Either way, hot-removing only works for memory-device as a whole, so >> there is no problem. >> >> Vmemmaps are created per hot-added operations, this means that >> vmemmaps will be created for the hot-added range. >> And since hot-add/hot-remove operations works with the same granularity, >> there is no problem. > > What does prevent calling somebody arch_add_memory for a range spanning > multiple memblocks from a driver directly. In other words aren't you To drivers, we only expose add_memory() and friends. And I think this is a good idea. > making assumptions about a future usage based on the qemu usecase? > As I noted, we only have an issue if add add_memory() and remove_memory() is called with different granularity. I gave two examples where this might not be the case, but we will have to look int the details. -- Thanks, David / dhildenb
