> 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. > OK, I can live with "bad pud" warnings for now. Would it be a bad idea to make the zap_pud_range function to look like vunmap_pud_range function by adding a pud_clear_huge(pud) call? -- Regards, Adam Turowski
