How to mmap any address space using huge pages?

[Adam Turowski]

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)?

Thanks

--
Regards,
Adam Turowski
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