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This breaks >> virtio-pmem which has file backed (MAP_SHARED) host mapping where GUP rejects >> FOLL_WRITE | FOLL_LONGTERM since: >> >> commit 8ac268436e6d ("mm/gup: disallow FOLL_LONGTERM GUP-nonfast writing to file-backed mappings") >> commit a6e79df92e4a ("mm/gup: disallow FOLL_LONGTERM GUP-fast writing to file-backed mappings"). >> >> Drop FOLL_LONGTERM when registering encrypted memory regions and restore >> the previous behavior. > But that breaks the original issue of breaking ZONE_MOVABLE/CMA? > > If it is a longterm pin, it must use FOLL_LONGTERM. :/ > > I assume we fail in check_vma_flags() > > if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma)) > return -EOPNOTSUPP; Yes, it fails in this path but for file backed mapping, vma_is_fsdax() returns false because vma_is_dax() returns false: > > IIRC, fsdax cannot tolerate unbounded pins. Is that the case we are running into? Host side backend is regular file backed memory (no fsdax). Thanks, Pankaj > > How does vfio deal with that? (does it?) >