// SPDX-License-Identifier: GPL-2.0-or-later /* * Copyright 2013 Red Hat Inc. * * Authors: Jérôme Glisse <jglisse@redhat.com> */ /* * Refer to include/linux/hmm.h for information about heterogeneous memory * management or HMM for short. */ #include <linux/pagewalk.h> #include <linux/hmm.h> #include <linux/init.h> #include <linux/rmap.h> #include <linux/swap.h> #include <linux/slab.h> #include <linux/sched.h> #include <linux/mmzone.h> #include <linux/pagemap.h> #include <linux/swapops.h> #include <linux/hugetlb.h> #include <linux/memremap.h> #include <linux/sched/mm.h> #include <linux/jump_label.h> #include <linux/dma-mapping.h> #include <linux/mmu_notifier.h> #include <linux/memory_hotplug.h> #include "internal.h" struct hmm_vma_walk { struct hmm_range *range; unsigned long last; }; enum { HMM_NEED_FAULT = 1 << 0, HMM_NEED_WRITE_FAULT = 1 << 1, HMM_NEED_ALL_BITS = HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT, }; static int hmm_pfns_fill(unsigned long addr, unsigned long end, struct hmm_range *range, unsigned long cpu_flags) { unsigned long i = (addr - range->start) >> PAGE_SHIFT; for (; addr < end; addr += PAGE_SIZE, i++) range->hmm_pfns[i] = cpu_flags; return 0; } /* * hmm_vma_fault() - fault in a range lacking valid pmd or pte(s) * @addr: range virtual start address (inclusive) * @end: range virtual end address (exclusive) * @required_fault: HMM_NEED_* flags * @walk: mm_walk structure * Return: -EBUSY after page fault, or page fault error * * This function will be called whenever pmd_none() or pte_none() returns true, * or whenever there is no page directory covering the virtual address range. */ static int hmm_vma_fault(unsigned long addr, unsigned long end, unsigned int required_fault, struct mm_walk *walk) { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct vm_area_struct *vma = walk->vma; unsigned int fault_flags = FAULT_FLAG_REMOTE; WARN_ON_ONCE(!required_fault); hmm_vma_walk->last = addr; if (required_fault & HMM_NEED_WRITE_FAULT) { if (!(vma->vm_flags & VM_WRITE)) return -EPERM; fault_flags |= FAULT_FLAG_WRITE; } for (; addr < end; addr += PAGE_SIZE) if (handle_mm_fault(vma, addr, fault_flags, NULL) & VM_FAULT_ERROR) return -EFAULT; return -EBUSY; } static unsigned int hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk, unsigned long pfn_req_flags, unsigned long cpu_flags) { struct hmm_range *range = hmm_vma_walk->range; /* * So we not only consider the individual per page request we also * consider the default flags requested for the range. The API can * be used 2 ways. The first one where the HMM user coalesces * multiple page faults into one request and sets flags per pfn for * those faults. The second one where the HMM user wants to pre- * fault a range with specific flags. For the latter one it is a * waste to have the user pre-fill the pfn arrays with a default * flags value. */ pfn_req_flags &= range->pfn_flags_mask; pfn_req_flags |= range->default_flags; /* We aren't ask to do anything ... */ if (!(pfn_req_flags & HMM_PFN_REQ_FAULT)) return 0; /* Need to write fault ? */ if ((pfn_req_flags & HMM_PFN_REQ_WRITE) && !(cpu_flags & HMM_PFN_WRITE)) return HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT; /* If CPU page table is not valid then we need to fault */ if (!(cpu_flags & HMM_PFN_VALID)) return HMM_NEED_FAULT; return 0; } static unsigned int hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk, const unsigned long hmm_pfns[], unsigned long npages, unsigned long cpu_flags) { struct hmm_range *range = hmm_vma_walk->range; unsigned int required_fault = 0; unsigned long i; /* * If the default flags do not request to fault pages, and the mask does * not allow for individual pages to be faulted, then * hmm_pte_need_fault() will always return 0. */ if (!((range->default_flags | range->pfn_flags_mask) & HMM_PFN_REQ_FAULT)) return 0; for (i = 0; i < npages; ++i) { required_fault |= hmm_pte_need_fault(hmm_vma_walk, hmm_pfns[i], cpu_flags); if (required_fault == HMM_NEED_ALL_BITS) return required_fault; } return required_fault; } static int hmm_vma_walk_hole(unsigned long addr, unsigned long end, __always_unused int depth, struct mm_walk *walk) { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; unsigned int required_fault; unsigned long i, npages; unsigned long *hmm_pfns; i = (addr - range->start) >> PAGE_SHIFT; npages = (end - addr) >> PAGE_SHIFT; hmm_pfns = &range->hmm_pfns[i]; required_fault = hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0); if (!walk->vma) { if (required_fault) return -EFAULT; return hmm_pfns_fill(addr, end, range, HMM_PFN_ERROR); } if (required_fault) return hmm_vma_fault(addr, end, required_fault, walk); return hmm_pfns_fill(addr, end, range, 0); } static inline unsigned long hmm_pfn_flags_order(unsigned long order) { return order << HMM_PFN_ORDER_SHIFT; } static inline unsigned long pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd) { if (pmd_protnone(pmd)) return 0; return (pmd_write(pmd) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID) | hmm_pfn_flags_order(PMD_SHIFT - PAGE_SHIFT); } #ifdef CONFIG_TRANSPARENT_HUGEPAGE static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr, unsigned long end, unsigned long hmm_pfns[], pmd_t pmd) { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; unsigned long pfn, npages, i; unsigned int required_fault; unsigned long cpu_flags; npages = (end - addr) >> PAGE_SHIFT; cpu_flags = pmd_to_hmm_pfn_flags(range, pmd); required_fault = hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, cpu_flags); if (required_fault) return hmm_vma_fault(addr, end, required_fault, walk); pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) hmm_pfns[i] = pfn | cpu_flags; return 0; } #else /* CONFIG_TRANSPARENT_HUGEPAGE */ /* stub to allow the code below to compile */ int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr, unsigned long end, unsigned long hmm_pfns[], pmd_t pmd); #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ static inline unsigned long pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte) { if (pte_none(pte) || !pte_present(pte) || pte_protnone(pte)) return 0; return pte_write(pte) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID; } static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, unsigned long end, pmd_t *pmdp, pte_t *ptep, unsigned long *hmm_pfn) { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; unsigned int required_fault; unsigned long cpu_flags; pte_t pte = ptep_get(ptep); uint64_t pfn_req_flags = *hmm_pfn; if (pte_none_mostly(pte)) { required_fault = hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0); if (required_fault) goto fault; *hmm_pfn = 0; return 0; } if (!pte_present(pte)) { swp_entry_t entry = pte_to_swp_entry(pte); /* * Don't fault in device private pages owned by the caller, * just report the PFN. */ if (is_device_private_entry(entry) && pfn_swap_entry_to_page(entry)->pgmap->owner == range->dev_private_owner) { cpu_flags = HMM_PFN_VALID; if (is_writable_device_private_entry(entry)) cpu_flags |= HMM_PFN_WRITE; *hmm_pfn = swp_offset_pfn(entry) | cpu_flags; return 0; } required_fault = hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0); if (!required_fault) { *hmm_pfn = 0; return 0; } if (!non_swap_entry(entry)) goto fault; if (is_device_private_entry(entry)) goto fault; if (is_device_exclusive_entry(entry)) goto fault; if (is_migration_entry(entry)) { pte_unmap(ptep); hmm_vma_walk->last = addr; migration_entry_wait(walk->mm, pmdp, addr); return -EBUSY; } /* Report error for everything else */ pte_unmap(ptep); return -EFAULT; } cpu_flags = pte_to_hmm_pfn_flags(range, pte); required_fault = hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags); if (required_fault) goto fault; /* * Bypass devmap pte such as DAX page when all pfn requested * flags(pfn_req_flags) are fulfilled. * Since each architecture defines a struct page for the zero page, just * fall through and treat it like a normal page. */ if (!vm_normal_page(walk->vma, addr, pte) && !pte_devmap(pte) && !is_zero_pfn(pte_pfn(pte))) { if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) { pte_unmap(ptep); return -EFAULT; } *hmm_pfn = HMM_PFN_ERROR; return 0; } *hmm_pfn = pte_pfn(pte) | cpu_flags; return 0; fault: pte_unmap(ptep); /* Fault any virtual address we were asked to fault */ return hmm_vma_fault(addr, end, required_fault, walk); } static int hmm_vma_walk_pmd(pmd_t *pmdp, unsigned long start, unsigned long end, struct mm_walk *walk) { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; unsigned long *hmm_pfns = &range->hmm_pfns[(start - range->start) >> PAGE_SHIFT]; unsigned long npages = (end - start) >> PAGE_SHIFT; unsigned long addr = start; pte_t *ptep; pmd_t pmd; again: pmd = pmdp_get_lockless(pmdp); if (pmd_none(pmd)) return hmm_vma_walk_hole(start, end, -1, walk); if (thp_migration_supported() && is_pmd_migration_entry(pmd)) { if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) { hmm_vma_walk->last = addr; pmd_migration_entry_wait(walk->mm, pmdp); return -EBUSY; } return hmm_pfns_fill(start, end, range, 0); } if (!pmd_present(pmd)) { if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) return -EFAULT; return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); } if (pmd_devmap(pmd) || pmd_trans_huge(pmd)) { /* * No need to take pmd_lock here, even if some other thread * is splitting the huge pmd we will get that event through * mmu_notifier callback. * * So just read pmd value and check again it's a transparent * huge or device mapping one and compute corresponding pfn * values. */ pmd = pmdp_get_lockless(pmdp); if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd)) goto again; return hmm_vma_handle_pmd(walk, addr, end, hmm_pfns, pmd); } /* * We have handled all the valid cases above ie either none, migration, * huge or transparent huge. At this point either it is a valid pmd * entry pointing to pte directory or it is a bad pmd that will not * recover. */ if (pmd_bad(pmd)) { if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) return -EFAULT; return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); } ptep = pte_offset_map(pmdp, addr); if (!ptep) goto again; for (; addr < end; addr += PAGE_SIZE, ptep++, hmm_pfns++) { int r; r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, hmm_pfns); if (r) { /* hmm_vma_handle_pte() did pte_unmap() */ return r; } } pte_unmap(ptep - 1); return 0; } #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && \ defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) static inline unsigned long pud_to_hmm_pfn_flags(struct hmm_range *range, pud_t pud) { if (!pud_present(pud)) return 0; return (pud_write(pud) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID) | hmm_pfn_flags_order(PUD_SHIFT - PAGE_SHIFT); } static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end, struct mm_walk *walk) { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; unsigned long addr = start; pud_t pud; spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma); if (!ptl) return 0; /* Normally we don't want to split the huge page */ walk->action = ACTION_CONTINUE; pud = READ_ONCE(*pudp); if (pud_none(pud)) { spin_unlock(ptl); return hmm_vma_walk_hole(start, end, -1, walk); } if (pud_huge(pud) && pud_devmap(pud)) { unsigned long i, npages, pfn; unsigned int required_fault; unsigned long *hmm_pfns; unsigned long cpu_flags; if (!pud_present(pud)) { spin_unlock(ptl); return hmm_vma_walk_hole(start, end, -1, walk); } i = (addr - range->start) >> PAGE_SHIFT; npages = (end - addr) >> PAGE_SHIFT; hmm_pfns = &range->hmm_pfns[i]; cpu_flags = pud_to_hmm_pfn_flags(range, pud); required_fault = hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, cpu_flags); if (required_fault) { spin_unlock(ptl); return hmm_vma_fault(addr, end, required_fault, walk); } pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); for (i = 0; i < npages; ++i, ++pfn) hmm_pfns[i] = pfn | cpu_flags; goto out_unlock; } /* Ask for the PUD to be split */ walk->action = ACTION_SUBTREE; out_unlock: spin_unlock(ptl); return 0; } #else #define hmm_vma_walk_pud NULL #endif #ifdef CONFIG_HUGETLB_PAGE static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask, unsigned long start, unsigned long end, struct mm_walk *walk) { unsigned long addr = start, i, pfn; struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; struct vm_area_struct *vma = walk->vma; unsigned int required_fault; unsigned long pfn_req_flags; unsigned long cpu_flags; spinlock_t *ptl; pte_t entry; ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte); entry = huge_ptep_get(pte); i = (start - range->start) >> PAGE_SHIFT; pfn_req_flags = range->hmm_pfns[i]; cpu_flags = pte_to_hmm_pfn_flags(range, entry) | hmm_pfn_flags_order(huge_page_order(hstate_vma(vma))); required_fault = hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags); if (required_fault) { int ret; spin_unlock(ptl); hugetlb_vma_unlock_read(vma); /* * Avoid deadlock: drop the vma lock before calling * hmm_vma_fault(), which will itself potentially take and * drop the vma lock. This is also correct from a * protection point of view, because there is no further * use here of either pte or ptl after dropping the vma * lock. */ ret = hmm_vma_fault(addr, end, required_fault, walk); hugetlb_vma_lock_read(vma); return ret; } pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT); for (; addr < end; addr += PAGE_SIZE, i++, pfn++) range->hmm_pfns[i] = pfn | cpu_flags; spin_unlock(ptl); return 0; } #else #define hmm_vma_walk_hugetlb_entry NULL #endif /* CONFIG_HUGETLB_PAGE */ static int hmm_vma_walk_test(unsigned long start, unsigned long end, struct mm_walk *walk) { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; struct vm_area_struct *vma = walk->vma; if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)) && vma->vm_flags & VM_READ) return 0; /* * vma ranges that don't have struct page backing them or map I/O * devices directly cannot be handled by hmm_range_fault(). * * If the vma does not allow read access, then assume that it does not * allow write access either. HMM does not support architectures that * allow write without read. * * If a fault is requested for an unsupported range then it is a hard * failure. */ if (hmm_range_need_fault(hmm_vma_walk, range->hmm_pfns + ((start - range->start) >> PAGE_SHIFT), (end - start) >> PAGE_SHIFT, 0)) return -EFAULT; hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); /* Skip this vma and continue processing the next vma. */ return 1; } static const struct mm_walk_ops hmm_walk_ops = { .pud_entry = hmm_vma_walk_pud, .pmd_entry = hmm_vma_walk_pmd, .pte_hole = hmm_vma_walk_hole, .hugetlb_entry = hmm_vma_walk_hugetlb_entry, .test_walk = hmm_vma_walk_test, .walk_lock = PGWALK_RDLOCK, }; /** * hmm_range_fault - try to fault some address in a virtual address range * @range: argument structure * * Returns 0 on success or one of the following error codes: * * -EINVAL: Invalid arguments or mm or virtual address is in an invalid vma * (e.g., device file vma). * -ENOMEM: Out of memory. * -EPERM: Invalid permission (e.g., asking for write and range is read * only). * -EBUSY: The range has been invalidated and the caller needs to wait for * the invalidation to finish. * -EFAULT: A page was requested to be valid and could not be made valid * ie it has no backing VMA or it is illegal to access * * This is similar to get_user_pages(), except that it can read the page tables * without mutating them (ie causing faults). */ int hmm_range_fault(struct hmm_range *range) { struct hmm_vma_walk hmm_vma_walk = { .range = range, .last = range->start, }; struct mm_struct *mm = range->notifier->mm; int ret; mmap_assert_locked(mm); do { /* If range is no longer valid force retry. */ if (mmu_interval_check_retry(range->notifier, range->notifier_seq)) return -EBUSY; ret = walk_page_range(mm, hmm_vma_walk.last, range->end, &hmm_walk_ops, &hmm_vma_walk); /* * When -EBUSY is returned the loop restarts with * hmm_vma_walk.last set to an address that has not been stored * in pfns. All entries < last in the pfn array are set to their * output, and all >= are still at their input values. */ } while (ret == -EBUSY); return ret; } EXPORT_SYMBOL(hmm_range_fault);