diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 8310875133ff..401087e8a43d 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1185,6 +1185,8 @@ extern void ptep_modify_prot_commit(struct vm_area_struct *vma, * where it is possible and makes sense to do so. The PTE_CONT bit is considered * a private implementation detail of the public ptep API (see below). */ +extern void __contpte_try_fold(struct mm_struct *mm, unsigned long addr, + pte_t *ptep, pte_t pte); extern void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte); extern pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte); @@ -1206,6 +1208,29 @@ extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep, pte_t entry, int dirty); +static __always_inline void contpte_try_fold(struct mm_struct *mm, + unsigned long addr, pte_t *ptep, pte_t pte) +{ + /* + * Only bother trying if both the virtual and physical addresses are + * aligned and correspond to the last entry in a contig range. The core + * code mostly modifies ranges from low to high, so this is the likely + * the last modification in the contig range, so a good time to fold. + * We can't fold special mappings, because there is no associated folio. + */ + + const unsigned long contmask = CONT_PTES - 1; + bool valign = ((addr >> PAGE_SHIFT) & contmask) == contmask; + + if (unlikely(valign)) { + bool palign = (pte_pfn(pte) & contmask) == contmask; + + if (unlikely(palign && + pte_valid(pte) && !pte_cont(pte) && !pte_special(pte))) + __contpte_try_fold(mm, addr, ptep, pte); + } +} + static __always_inline void contpte_try_unfold(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte) { @@ -1286,6 +1311,7 @@ static __always_inline void set_ptes(struct mm_struct *mm, unsigned long addr, if (likely(nr == 1)) { contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); __set_ptes(mm, addr, ptep, pte, 1); + contpte_try_fold(mm, addr, ptep, pte); } else { contpte_set_ptes(mm, addr, ptep, pte, nr); } diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c index 50e0173dc5ee..16788f07716d 100644 --- a/arch/arm64/mm/contpte.c +++ b/arch/arm64/mm/contpte.c @@ -73,6 +73,70 @@ static void contpte_convert(struct mm_struct *mm, unsigned long addr, __set_ptes(mm, start_addr, start_ptep, pte, CONT_PTES); } +void __contpte_try_fold(struct mm_struct *mm, unsigned long addr, + pte_t *ptep, pte_t pte) +{ + /* + * We have already checked that the virtual and pysical addresses are + * correctly aligned for a contpte mapping in contpte_try_fold() so the + * remaining checks are to ensure that the contpte range is fully + * covered by a single folio, and ensure that all the ptes are valid + * with contiguous PFNs and matching prots. We ignore the state of the + * access and dirty bits for the purpose of deciding if its a contiguous + * range; the folding process will generate a single contpte entry which + * has a single access and dirty bit. Those 2 bits are the logical OR of + * their respective bits in the constituent pte entries. In order to + * ensure the contpte range is covered by a single folio, we must + * recover the folio from the pfn, but special mappings don't have a + * folio backing them. Fortunately contpte_try_fold() already checked + * that the pte is not special - we never try to fold special mappings. + * Note we can't use vm_normal_page() for this since we don't have the + * vma. + */ + + unsigned long folio_start, folio_end; + unsigned long cont_start, cont_end; + pte_t expected_pte, subpte; + struct folio *folio; + struct page *page; + unsigned long pfn; + pte_t *orig_ptep; + pgprot_t prot; + + int i; + + if (!mm_is_user(mm)) + return; + + page = pte_page(pte); + folio = page_folio(page); + folio_start = addr - (page - &folio->page) * PAGE_SIZE; + folio_end = folio_start + folio_nr_pages(folio) * PAGE_SIZE; + cont_start = ALIGN_DOWN(addr, CONT_PTE_SIZE); + cont_end = cont_start + CONT_PTE_SIZE; + + if (folio_start > cont_start || folio_end < cont_end) + return; + + pfn = ALIGN_DOWN(pte_pfn(pte), CONT_PTES); + prot = pte_pgprot(pte_mkold(pte_mkclean(pte))); + expected_pte = pfn_pte(pfn, prot); + orig_ptep = ptep; + ptep = contpte_align_down(ptep); + + for (i = 0; i < CONT_PTES; i++) { + subpte = pte_mkold(pte_mkclean(__ptep_get(ptep))); + if (!pte_same(subpte, expected_pte)) + return; + expected_pte = pte_advance_pfn(expected_pte, 1); + ptep++; + } + + pte = pte_mkcont(pte); + contpte_convert(mm, addr, orig_ptep, pte); +} +EXPORT_SYMBOL(__contpte_try_fold); + void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte) {