arm64: Implement page table free interfaces
arm64 requires break-before-make. Originally, before setting up new pmd/pud entry for huge mapping, in few cases, the modifying pmd/pud entry was still valid and pointing to next level page table as we only clear off leaf PTE in unmap leg. a) This was resulting into stale entry in TLBs (as few TLBs also cache intermediate mapping for performance reasons) b) Also, modifying pmd/pud was the only reference to next level page table and it was getting lost without freeing it. So, page leaks were happening. Implement pud_free_pmd_page() and pmd_free_pte_page() to enforce BBM and also free the leaking page tables. Implementation requires, 1) Clearing off the current pud/pmd entry 2) Invalidation of TLB 3) Freeing of the un-used next level page tables Reviewed-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Chintan Pandya <cpandya@codeaurora.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
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