On Wed, Aug 08, 2018 at 12:58:15PM -0400, Jerome Glisse wrote: > > If the former then I do not see any reason why we couldn't simply > > refactor the code to expect a failure and drop the warning in that path. > > Referring to newer case ie calling release_mem_region_adjustable() for > ZONE_DEVICE too. It seems i got my recollection wrong in the sense that > the resource is properly register as MEM but still we do not want to > release it because the device driver might still be using the resource > without struct page. The lifetime of the resource as memory with struct > page and the lifetime of the resource as something use by the device > driver are not tie together. The latter can outlive the former. > > So when we hotremove ZONE_DEVICE we do not want to release the resource > yet just to be on safe side and avoid some other driver/kernel component > to decide to use that resource. I checked the function that hot-removes the memory in HMM code. hmm_devmem_pages_remove(), which gets called via hmm_devmem_remove(), is in charge of hot-removing the memory. Then, hmm_devmem_remove() will release the resource only if the resource is not of type IORES_DESC_DEVICE_PUBLIC_MEMORY. So I guess that there are cases(at least in HMM) where we release the resource when hot-removing memory, but not always. Looking at devm code, I could not see any place where we release the resource when hot-removing memory. So, if we are really left with such scenario, maybe the easiest way is to pass a parameter from those paths to arch_remove_memory()->__remove_pages() to know if we get called from device_functions, and so skip the call to release_mem_region_adjustable. Thanks -- Oscar Salvador SUSE L3
