On Sat, Oct 16, 2021 at 11:46:59AM +0200, Adam Turowski wrote: > Hello all, > I have a device and I need to mmap it into a user space using 1GB huge > pages. AFAIK I cannot use HugeTLB nor THP because they're backed by the > memory. The remap_pfn_range doesn't use huge pages neither. So I used a > huge_fault handler to set up the pud descriptor myself (arm64 here, so no > transparent puds) and that works. The problem is that the kernel warns > about a bad pud when the vma mapping is removed, the zap_pud_range function > doesn't accept block puds. The vunmap_pud_range function works with block > puds and checks for their presence and calls the pud_clear_huge function. > If I add this function call to the zap_pud_range function, the warnings are > gone. > > Am I missing something? What is the proper way to mmap (and munmap) any > address space using huge pages (esp. 1GB pages)? AFAIK it can't be done today. Certainly non-struct page memory cannot be installed in a PUD If you create a ZONE_DEVICE struct page using memremap_pages() then they can be inserted using vmf_insert_pfn_pud() - however that requires arch support for pud_devmap() which only x86 does right now. Jason
