On Wed, Oct 20, 2021 at 08:34:33AM +0200, Thomas Hellström wrote: > Follow up question: If we resurrect this in the proper way (and in that case > only for x86_64) is there something we need to pay particular attention to > WRT the ZONE_DEVICE refcounting fixing you mention above? Similar to PTE it should be completely separated from ZONE_DEVICE. Seeing the special bit set at any level should trigger all page table walkers to never try to get a struct page. Today some of the page table walkers are trying to do this with vma_is_special(), all of those should end up being the Pxx_SPECIAL test instead. Jason
