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-rw-r--r--arch/arm64/mm/contpte.c408
1 files changed, 408 insertions, 0 deletions
diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
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+++ b/arch/arm64/mm/contpte.c
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+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 ARM Ltd.
+ */
+
+#include <linux/mm.h>
+#include <linux/efi.h>
+#include <linux/export.h>
+#include <asm/tlbflush.h>
+
+static inline bool mm_is_user(struct mm_struct *mm)
+{
+ /*
+ * Don't attempt to apply the contig bit to kernel mappings, because
+ * dynamically adding/removing the contig bit can cause page faults.
+ * These racing faults are ok for user space, since they get serialized
+ * on the PTL. But kernel mappings can't tolerate faults.
+ */
+ if (unlikely(mm_is_efi(mm)))
+ return false;
+ return mm != &init_mm;
+}
+
+static inline pte_t *contpte_align_down(pte_t *ptep)
+{
+ return PTR_ALIGN_DOWN(ptep, sizeof(*ptep) * CONT_PTES);
+}
+
+static void contpte_try_unfold_partial(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep, unsigned int nr)
+{
+ /*
+ * Unfold any partially covered contpte block at the beginning and end
+ * of the range.
+ */
+
+ if (ptep != contpte_align_down(ptep) || nr < CONT_PTES)
+ contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep));
+
+ if (ptep + nr != contpte_align_down(ptep + nr)) {
+ unsigned long last_addr = addr + PAGE_SIZE * (nr - 1);
+ pte_t *last_ptep = ptep + nr - 1;
+
+ contpte_try_unfold(mm, last_addr, last_ptep,
+ __ptep_get(last_ptep));
+ }
+}
+
+static void contpte_convert(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep, pte_t pte)
+{
+ struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
+ unsigned long start_addr;
+ pte_t *start_ptep;
+ int i;
+
+ start_ptep = ptep = contpte_align_down(ptep);
+ start_addr = addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);
+ pte = pfn_pte(ALIGN_DOWN(pte_pfn(pte), CONT_PTES), pte_pgprot(pte));
+
+ for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE) {
+ pte_t ptent = __ptep_get_and_clear(mm, addr, ptep);
+
+ if (pte_dirty(ptent))
+ pte = pte_mkdirty(pte);
+
+ if (pte_young(ptent))
+ pte = pte_mkyoung(pte);
+ }
+
+ __flush_tlb_range(&vma, start_addr, addr, PAGE_SIZE, true, 3);
+
+ __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_GPL(__contpte_try_fold);
+
+void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep, pte_t pte)
+{
+ /*
+ * We have already checked that the ptes are contiguous in
+ * contpte_try_unfold(), so just check that the mm is user space.
+ */
+ if (!mm_is_user(mm))
+ return;
+
+ pte = pte_mknoncont(pte);
+ contpte_convert(mm, addr, ptep, pte);
+}
+EXPORT_SYMBOL_GPL(__contpte_try_unfold);
+
+pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte)
+{
+ /*
+ * Gather access/dirty bits, which may be populated in any of the ptes
+ * of the contig range. We are guaranteed to be holding the PTL, so any
+ * contiguous range cannot be unfolded or otherwise modified under our
+ * feet.
+ */
+
+ pte_t pte;
+ int i;
+
+ ptep = contpte_align_down(ptep);
+
+ for (i = 0; i < CONT_PTES; i++, ptep++) {
+ pte = __ptep_get(ptep);
+
+ if (pte_dirty(pte))
+ orig_pte = pte_mkdirty(orig_pte);
+
+ if (pte_young(pte))
+ orig_pte = pte_mkyoung(orig_pte);
+ }
+
+ return orig_pte;
+}
+EXPORT_SYMBOL_GPL(contpte_ptep_get);
+
+pte_t contpte_ptep_get_lockless(pte_t *orig_ptep)
+{
+ /*
+ * The ptep_get_lockless() API requires us to read and return *orig_ptep
+ * so that it is self-consistent, without the PTL held, so we may be
+ * racing with other threads modifying the pte. Usually a READ_ONCE()
+ * would suffice, but for the contpte case, we also need to gather the
+ * access and dirty bits from across all ptes in the contiguous block,
+ * and we can't read all of those neighbouring ptes atomically, so any
+ * contiguous range may be unfolded/modified/refolded under our feet.
+ * Therefore we ensure we read a _consistent_ contpte range by checking
+ * that all ptes in the range are valid and have CONT_PTE set, that all
+ * pfns are contiguous and that all pgprots are the same (ignoring
+ * access/dirty). If we find a pte that is not consistent, then we must
+ * be racing with an update so start again. If the target pte does not
+ * have CONT_PTE set then that is considered consistent on its own
+ * because it is not part of a contpte range.
+ */
+
+ pgprot_t orig_prot;
+ unsigned long pfn;
+ pte_t orig_pte;
+ pgprot_t prot;
+ pte_t *ptep;
+ pte_t pte;
+ int i;
+
+retry:
+ orig_pte = __ptep_get(orig_ptep);
+
+ if (!pte_valid_cont(orig_pte))
+ return orig_pte;
+
+ orig_prot = pte_pgprot(pte_mkold(pte_mkclean(orig_pte)));
+ ptep = contpte_align_down(orig_ptep);
+ pfn = pte_pfn(orig_pte) - (orig_ptep - ptep);
+
+ for (i = 0; i < CONT_PTES; i++, ptep++, pfn++) {
+ pte = __ptep_get(ptep);
+ prot = pte_pgprot(pte_mkold(pte_mkclean(pte)));
+
+ if (!pte_valid_cont(pte) ||
+ pte_pfn(pte) != pfn ||
+ pgprot_val(prot) != pgprot_val(orig_prot))
+ goto retry;
+
+ if (pte_dirty(pte))
+ orig_pte = pte_mkdirty(orig_pte);
+
+ if (pte_young(pte))
+ orig_pte = pte_mkyoung(orig_pte);
+ }
+
+ return orig_pte;
+}
+EXPORT_SYMBOL_GPL(contpte_ptep_get_lockless);
+
+void contpte_set_ptes(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep, pte_t pte, unsigned int nr)
+{
+ unsigned long next;
+ unsigned long end;
+ unsigned long pfn;
+ pgprot_t prot;
+
+ /*
+ * The set_ptes() spec guarantees that when nr > 1, the initial state of
+ * all ptes is not-present. Therefore we never need to unfold or
+ * otherwise invalidate a range before we set the new ptes.
+ * contpte_set_ptes() should never be called for nr < 2.
+ */
+ VM_WARN_ON(nr == 1);
+
+ if (!mm_is_user(mm))
+ return __set_ptes(mm, addr, ptep, pte, nr);
+
+ end = addr + (nr << PAGE_SHIFT);
+ pfn = pte_pfn(pte);
+ prot = pte_pgprot(pte);
+
+ do {
+ next = pte_cont_addr_end(addr, end);
+ nr = (next - addr) >> PAGE_SHIFT;
+ pte = pfn_pte(pfn, prot);
+
+ if (((addr | next | (pfn << PAGE_SHIFT)) & ~CONT_PTE_MASK) == 0)
+ pte = pte_mkcont(pte);
+ else
+ pte = pte_mknoncont(pte);
+
+ __set_ptes(mm, addr, ptep, pte, nr);
+
+ addr = next;
+ ptep += nr;
+ pfn += nr;
+
+ } while (addr != end);
+}
+EXPORT_SYMBOL_GPL(contpte_set_ptes);
+
+void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep, unsigned int nr, int full)
+{
+ contpte_try_unfold_partial(mm, addr, ptep, nr);
+ __clear_full_ptes(mm, addr, ptep, nr, full);
+}
+EXPORT_SYMBOL_GPL(contpte_clear_full_ptes);
+
+pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm,
+ unsigned long addr, pte_t *ptep,
+ unsigned int nr, int full)
+{
+ contpte_try_unfold_partial(mm, addr, ptep, nr);
+ return __get_and_clear_full_ptes(mm, addr, ptep, nr, full);
+}
+EXPORT_SYMBOL_GPL(contpte_get_and_clear_full_ptes);
+
+int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep)
+{
+ /*
+ * ptep_clear_flush_young() technically requires us to clear the access
+ * flag for a _single_ pte. However, the core-mm code actually tracks
+ * access/dirty per folio, not per page. And since we only create a
+ * contig range when the range is covered by a single folio, we can get
+ * away with clearing young for the whole contig range here, so we avoid
+ * having to unfold.
+ */
+
+ int young = 0;
+ int i;
+
+ ptep = contpte_align_down(ptep);
+ addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);
+
+ for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE)
+ young |= __ptep_test_and_clear_young(vma, addr, ptep);
+
+ return young;
+}
+EXPORT_SYMBOL_GPL(contpte_ptep_test_and_clear_young);
+
+int contpte_ptep_clear_flush_young(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep)
+{
+ int young;
+
+ young = contpte_ptep_test_and_clear_young(vma, addr, ptep);
+
+ if (young) {
+ /*
+ * See comment in __ptep_clear_flush_young(); same rationale for
+ * eliding the trailing DSB applies here.
+ */
+ addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);
+ __flush_tlb_range_nosync(vma, addr, addr + CONT_PTE_SIZE,
+ PAGE_SIZE, true, 3);
+ }
+
+ return young;
+}
+EXPORT_SYMBOL_GPL(contpte_ptep_clear_flush_young);
+
+void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep, unsigned int nr)
+{
+ /*
+ * If wrprotecting an entire contig range, we can avoid unfolding. Just
+ * set wrprotect and wait for the later mmu_gather flush to invalidate
+ * the tlb. Until the flush, the page may or may not be wrprotected.
+ * After the flush, it is guaranteed wrprotected. If it's a partial
+ * range though, we must unfold, because we can't have a case where
+ * CONT_PTE is set but wrprotect applies to a subset of the PTEs; this
+ * would cause it to continue to be unpredictable after the flush.
+ */
+
+ contpte_try_unfold_partial(mm, addr, ptep, nr);
+ __wrprotect_ptes(mm, addr, ptep, nr);
+}
+EXPORT_SYMBOL_GPL(contpte_wrprotect_ptes);
+
+int contpte_ptep_set_access_flags(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep,
+ pte_t entry, int dirty)
+{
+ unsigned long start_addr;
+ pte_t orig_pte;
+ int i;
+
+ /*
+ * Gather the access/dirty bits for the contiguous range. If nothing has
+ * changed, its a noop.
+ */
+ orig_pte = pte_mknoncont(ptep_get(ptep));
+ if (pte_val(orig_pte) == pte_val(entry))
+ return 0;
+
+ /*
+ * We can fix up access/dirty bits without having to unfold the contig
+ * range. But if the write bit is changing, we must unfold.
+ */
+ if (pte_write(orig_pte) == pte_write(entry)) {
+ /*
+ * For HW access management, we technically only need to update
+ * the flag on a single pte in the range. But for SW access
+ * management, we need to update all the ptes to prevent extra
+ * faults. Avoid per-page tlb flush in __ptep_set_access_flags()
+ * and instead flush the whole range at the end.
+ */
+ ptep = contpte_align_down(ptep);
+ start_addr = addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);
+
+ for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE)
+ __ptep_set_access_flags(vma, addr, ptep, entry, 0);
+
+ if (dirty)
+ __flush_tlb_range(vma, start_addr, addr,
+ PAGE_SIZE, true, 3);
+ } else {
+ __contpte_try_unfold(vma->vm_mm, addr, ptep, orig_pte);
+ __ptep_set_access_flags(vma, addr, ptep, entry, dirty);
+ }
+
+ return 1;
+}
+EXPORT_SYMBOL_GPL(contpte_ptep_set_access_flags);