// SPDX-License-Identifier: GPL-2.0-or-later /* * Copyright 2013 Red Hat Inc. * * Authors: Jérôme Glisse */ /* * Refer to include/linux/hmm.h for information about heterogeneous memory * management or HMM for short. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include 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, }; /* * hmm_device_entry_from_pfn() - create a valid device entry value from pfn * @range: range use to encode HMM pfn value * @pfn: pfn value for which to create the device entry * Return: valid device entry for the pfn */ static uint64_t hmm_device_entry_from_pfn(const struct hmm_range *range, unsigned long pfn) { return (pfn << range->pfn_shift) | range->flags[HMM_PFN_VALID]; } static int hmm_pfns_fill(unsigned long addr, unsigned long end, struct hmm_range *range, enum hmm_pfn_value_e value) { uint64_t *pfns = range->pfns; unsigned long i; i = (addr - range->start) >> PAGE_SHIFT; for (; addr < end; addr += PAGE_SIZE, i++) pfns[i] = range->values[value]; 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) & VM_FAULT_ERROR) return -EFAULT; return -EBUSY; } static unsigned int hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk, uint64_t pfns, uint64_t 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. */ pfns = (pfns & range->pfn_flags_mask) | range->default_flags; /* We aren't ask to do anything ... */ if (!(pfns & range->flags[HMM_PFN_VALID])) return 0; /* Need to write fault ? */ if ((pfns & range->flags[HMM_PFN_WRITE]) && !(cpu_flags & range->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 & range->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 uint64_t *pfns, unsigned long npages, uint64_t 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) & range->flags[HMM_PFN_VALID])) return 0; for (i = 0; i < npages; ++i) { required_fault |= hmm_pte_need_fault(hmm_vma_walk, 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; uint64_t *pfns; i = (addr - range->start) >> PAGE_SHIFT; npages = (end - addr) >> PAGE_SHIFT; pfns = &range->pfns[i]; required_fault = hmm_range_need_fault(hmm_vma_walk, 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); hmm_vma_walk->last = addr; return hmm_pfns_fill(addr, end, range, HMM_PFN_NONE); } static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd) { if (pmd_protnone(pmd)) return 0; return pmd_write(pmd) ? range->flags[HMM_PFN_VALID] | range->flags[HMM_PFN_WRITE] : range->flags[HMM_PFN_VALID]; } #ifdef CONFIG_TRANSPARENT_HUGEPAGE static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr, unsigned long end, uint64_t *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; uint64_t 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, 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++) pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags; hmm_vma_walk->last = end; 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, uint64_t *pfns, pmd_t pmd); #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ static inline bool hmm_is_device_private_entry(struct hmm_range *range, swp_entry_t entry) { return is_device_private_entry(entry) && device_private_entry_to_page(entry)->pgmap->owner == range->dev_private_owner; } static inline uint64_t 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) ? range->flags[HMM_PFN_VALID] | range->flags[HMM_PFN_WRITE] : range->flags[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, uint64_t *pfn) { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; unsigned int required_fault; uint64_t cpu_flags; pte_t pte = *ptep; uint64_t orig_pfn = *pfn; if (pte_none(pte)) { required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0); if (required_fault) goto fault; *pfn = range->values[HMM_PFN_NONE]; return 0; } if (!pte_present(pte)) { swp_entry_t entry = pte_to_swp_entry(pte); /* * Never fault in device private pages pages, but just report * the PFN even if not present. */ if (hmm_is_device_private_entry(range, entry)) { *pfn = hmm_device_entry_from_pfn(range, device_private_entry_to_pfn(entry)); *pfn |= range->flags[HMM_PFN_VALID]; if (is_write_device_private_entry(entry)) *pfn |= range->flags[HMM_PFN_WRITE]; return 0; } required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0); if (!required_fault) { *pfn = range->values[HMM_PFN_NONE]; return 0; } if (!non_swap_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, orig_pfn, cpu_flags); if (required_fault) goto fault; /* * Since each architecture defines a struct page for the zero page, just * fall through and treat it like a normal page. */ if (pte_special(pte) && !is_zero_pfn(pte_pfn(pte))) { if (hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0)) { pte_unmap(ptep); return -EFAULT; } *pfn = range->values[HMM_PFN_SPECIAL]; return 0; } *pfn = hmm_device_entry_from_pfn(range, 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; uint64_t *pfns = &range->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 = READ_ONCE(*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, pfns, npages, 0)) { hmm_vma_walk->last = addr; pmd_migration_entry_wait(walk->mm, pmdp); return -EBUSY; } return hmm_pfns_fill(start, end, range, HMM_PFN_NONE); } if (!pmd_present(pmd)) { if (hmm_range_need_fault(hmm_vma_walk, 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 = pmd_read_atomic(pmdp); barrier(); if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd)) goto again; return hmm_vma_handle_pmd(walk, addr, end, 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, pfns, npages, 0)) return -EFAULT; return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); } ptep = pte_offset_map(pmdp, addr); for (; addr < end; addr += PAGE_SIZE, ptep++, pfns++) { int r; r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, pfns); if (r) { /* hmm_vma_handle_pte() did pte_unmap() */ hmm_vma_walk->last = addr; return r; } } pte_unmap(ptep - 1); hmm_vma_walk->last = addr; return 0; } #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && \ defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) static inline uint64_t pud_to_hmm_pfn_flags(struct hmm_range *range, pud_t pud) { if (!pud_present(pud)) return 0; return pud_write(pud) ? range->flags[HMM_PFN_VALID] | range->flags[HMM_PFN_WRITE] : range->flags[HMM_PFN_VALID]; } 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; int ret = 0; 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; uint64_t *pfns, 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; pfns = &range->pfns[i]; cpu_flags = pud_to_hmm_pfn_flags(range, pud); required_fault = hmm_range_need_fault(hmm_vma_walk, 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) pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags; hmm_vma_walk->last = end; goto out_unlock; } /* Ask for the PUD to be split */ walk->action = ACTION_SUBTREE; out_unlock: spin_unlock(ptl); return ret; } #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; uint64_t orig_pfn, cpu_flags; unsigned int required_fault; 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; orig_pfn = range->pfns[i]; cpu_flags = pte_to_hmm_pfn_flags(range, entry); required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags); if (required_fault) { spin_unlock(ptl); return hmm_vma_fault(addr, end, required_fault, walk); } pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT); for (; addr < end; addr += PAGE_SIZE, i++, pfn++) range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags; hmm_vma_walk->last = end; 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 | VM_MIXEDMAP)) && 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->pfns + ((start - range->start) >> PAGE_SHIFT), (end - start) >> PAGE_SHIFT, 0)) return -EFAULT; hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); hmm_vma_walk->last = end; /* 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, }; /** * hmm_range_fault - try to fault some address in a virtual address range * @range: argument structure * * Return: the number of valid pages in range->pfns[] (from range start * address), which may be zero. On error one of the following status codes * can be returned: * * -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). */ long 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; lockdep_assert_held(&mm->mmap_sem); 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); } while (ret == -EBUSY); if (ret) return ret; return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT; } EXPORT_SYMBOL(hmm_range_fault);