diff options
Diffstat (limited to 'mm/hmm.c')
| -rw-r--r-- | mm/hmm.c | 1348 |
1 files changed, 1348 insertions, 0 deletions
diff --git a/mm/hmm.c b/mm/hmm.c new file mode 100644 index 000000000..c482c07bb --- /dev/null +++ b/mm/hmm.c @@ -0,0 +1,1348 @@ +/* + * Copyright 2013 Red Hat Inc. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * Authors: Jérôme Glisse <jglisse@redhat.com> + */ +/* + * Refer to include/linux/hmm.h for information about heterogeneous memory + * management or HMM for short. + */ +#include <linux/mm.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/jump_label.h> +#include <linux/mmu_notifier.h> +#include <linux/memory_hotplug.h> + +#define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT) + +#if IS_ENABLED(CONFIG_HMM_MIRROR) +static const struct mmu_notifier_ops hmm_mmu_notifier_ops; + +/* + * struct hmm - HMM per mm struct + * + * @mm: mm struct this HMM struct is bound to + * @lock: lock protecting ranges list + * @sequence: we track updates to the CPU page table with a sequence number + * @ranges: list of range being snapshotted + * @mirrors: list of mirrors for this mm + * @mmu_notifier: mmu notifier to track updates to CPU page table + * @mirrors_sem: read/write semaphore protecting the mirrors list + */ +struct hmm { + struct mm_struct *mm; + spinlock_t lock; + atomic_t sequence; + struct list_head ranges; + struct list_head mirrors; + struct mmu_notifier mmu_notifier; + struct rw_semaphore mirrors_sem; +}; + +/* + * hmm_register - register HMM against an mm (HMM internal) + * + * @mm: mm struct to attach to + * + * This is not intended to be used directly by device drivers. It allocates an + * HMM struct if mm does not have one, and initializes it. + */ +static struct hmm *hmm_register(struct mm_struct *mm) +{ + struct hmm *hmm = READ_ONCE(mm->hmm); + bool cleanup = false; + + /* + * The hmm struct can only be freed once the mm_struct goes away, + * hence we should always have pre-allocated an new hmm struct + * above. + */ + if (hmm) + return hmm; + + hmm = kmalloc(sizeof(*hmm), GFP_KERNEL); + if (!hmm) + return NULL; + INIT_LIST_HEAD(&hmm->mirrors); + init_rwsem(&hmm->mirrors_sem); + atomic_set(&hmm->sequence, 0); + hmm->mmu_notifier.ops = NULL; + INIT_LIST_HEAD(&hmm->ranges); + spin_lock_init(&hmm->lock); + hmm->mm = mm; + + spin_lock(&mm->page_table_lock); + if (!mm->hmm) + mm->hmm = hmm; + else + cleanup = true; + spin_unlock(&mm->page_table_lock); + + if (cleanup) + goto error; + + /* + * We should only get here if hold the mmap_sem in write mode ie on + * registration of first mirror through hmm_mirror_register() + */ + hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops; + if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) + goto error_mm; + + return mm->hmm; + +error_mm: + spin_lock(&mm->page_table_lock); + if (mm->hmm == hmm) + mm->hmm = NULL; + spin_unlock(&mm->page_table_lock); +error: + kfree(hmm); + return NULL; +} + +void hmm_mm_destroy(struct mm_struct *mm) +{ + kfree(mm->hmm); +} + +static void hmm_invalidate_range(struct hmm *hmm, + enum hmm_update_type action, + unsigned long start, + unsigned long end) +{ + struct hmm_mirror *mirror; + struct hmm_range *range; + + spin_lock(&hmm->lock); + list_for_each_entry(range, &hmm->ranges, list) { + unsigned long addr, idx, npages; + + if (end < range->start || start >= range->end) + continue; + + range->valid = false; + addr = max(start, range->start); + idx = (addr - range->start) >> PAGE_SHIFT; + npages = (min(range->end, end) - addr) >> PAGE_SHIFT; + memset(&range->pfns[idx], 0, sizeof(*range->pfns) * npages); + } + spin_unlock(&hmm->lock); + + down_read(&hmm->mirrors_sem); + list_for_each_entry(mirror, &hmm->mirrors, list) + mirror->ops->sync_cpu_device_pagetables(mirror, action, + start, end); + up_read(&hmm->mirrors_sem); +} + +static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm) +{ + struct hmm_mirror *mirror; + struct hmm *hmm = mm->hmm; + + down_write(&hmm->mirrors_sem); + mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror, + list); + while (mirror) { + list_del_init(&mirror->list); + if (mirror->ops->release) { + /* + * Drop mirrors_sem so callback can wait on any pending + * work that might itself trigger mmu_notifier callback + * and thus would deadlock with us. + */ + up_write(&hmm->mirrors_sem); + mirror->ops->release(mirror); + down_write(&hmm->mirrors_sem); + } + mirror = list_first_entry_or_null(&hmm->mirrors, + struct hmm_mirror, list); + } + up_write(&hmm->mirrors_sem); +} + +static int hmm_invalidate_range_start(struct mmu_notifier *mn, + struct mm_struct *mm, + unsigned long start, + unsigned long end, + bool blockable) +{ + struct hmm *hmm = mm->hmm; + + VM_BUG_ON(!hmm); + + atomic_inc(&hmm->sequence); + + return 0; +} + +static void hmm_invalidate_range_end(struct mmu_notifier *mn, + struct mm_struct *mm, + unsigned long start, + unsigned long end) +{ + struct hmm *hmm = mm->hmm; + + VM_BUG_ON(!hmm); + + hmm_invalidate_range(mm->hmm, HMM_UPDATE_INVALIDATE, start, end); +} + +static const struct mmu_notifier_ops hmm_mmu_notifier_ops = { + .release = hmm_release, + .invalidate_range_start = hmm_invalidate_range_start, + .invalidate_range_end = hmm_invalidate_range_end, +}; + +/* + * hmm_mirror_register() - register a mirror against an mm + * + * @mirror: new mirror struct to register + * @mm: mm to register against + * + * To start mirroring a process address space, the device driver must register + * an HMM mirror struct. + * + * THE mm->mmap_sem MUST BE HELD IN WRITE MODE ! + */ +int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm) +{ + /* Sanity check */ + if (!mm || !mirror || !mirror->ops) + return -EINVAL; + +again: + mirror->hmm = hmm_register(mm); + if (!mirror->hmm) + return -ENOMEM; + + down_write(&mirror->hmm->mirrors_sem); + if (mirror->hmm->mm == NULL) { + /* + * A racing hmm_mirror_unregister() is about to destroy the hmm + * struct. Try again to allocate a new one. + */ + up_write(&mirror->hmm->mirrors_sem); + mirror->hmm = NULL; + goto again; + } else { + list_add(&mirror->list, &mirror->hmm->mirrors); + up_write(&mirror->hmm->mirrors_sem); + } + + return 0; +} +EXPORT_SYMBOL(hmm_mirror_register); + +/* + * hmm_mirror_unregister() - unregister a mirror + * + * @mirror: new mirror struct to register + * + * Stop mirroring a process address space, and cleanup. + */ +void hmm_mirror_unregister(struct hmm_mirror *mirror) +{ + bool should_unregister = false; + struct mm_struct *mm; + struct hmm *hmm; + + if (mirror->hmm == NULL) + return; + + hmm = mirror->hmm; + down_write(&hmm->mirrors_sem); + list_del_init(&mirror->list); + should_unregister = list_empty(&hmm->mirrors); + mirror->hmm = NULL; + mm = hmm->mm; + hmm->mm = NULL; + up_write(&hmm->mirrors_sem); + + if (!should_unregister || mm == NULL) + return; + + mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm); + + spin_lock(&mm->page_table_lock); + if (mm->hmm == hmm) + mm->hmm = NULL; + spin_unlock(&mm->page_table_lock); + + kfree(hmm); +} +EXPORT_SYMBOL(hmm_mirror_unregister); + +struct hmm_vma_walk { + struct hmm_range *range; + unsigned long last; + bool fault; + bool block; +}; + +static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr, + bool write_fault, uint64_t *pfn) +{ + unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE; + struct hmm_vma_walk *hmm_vma_walk = walk->private; + struct hmm_range *range = hmm_vma_walk->range; + struct vm_area_struct *vma = walk->vma; + vm_fault_t ret; + + flags |= hmm_vma_walk->block ? 0 : FAULT_FLAG_ALLOW_RETRY; + flags |= write_fault ? FAULT_FLAG_WRITE : 0; + ret = handle_mm_fault(vma, addr, flags); + if (ret & VM_FAULT_RETRY) + return -EBUSY; + if (ret & VM_FAULT_ERROR) { + *pfn = range->values[HMM_PFN_ERROR]; + return -EFAULT; + } + + return -EAGAIN; +} + +static int hmm_pfns_bad(unsigned long addr, + 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; + unsigned long i; + + i = (addr - range->start) >> PAGE_SHIFT; + for (; addr < end; addr += PAGE_SIZE, i++) + pfns[i] = range->values[HMM_PFN_ERROR]; + + return 0; +} + +/* + * hmm_vma_walk_hole() - handle a range lacking valid pmd or pte(s) + * @start: range virtual start address (inclusive) + * @end: range virtual end address (exclusive) + * @fault: should we fault or not ? + * @write_fault: write fault ? + * @walk: mm_walk structure + * Returns: 0 on success, -EAGAIN 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_walk_hole_(unsigned long addr, unsigned long end, + bool fault, bool write_fault, + 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; + unsigned long i; + + hmm_vma_walk->last = addr; + i = (addr - range->start) >> PAGE_SHIFT; + for (; addr < end; addr += PAGE_SIZE, i++) { + pfns[i] = range->values[HMM_PFN_NONE]; + if (fault || write_fault) { + int ret; + + ret = hmm_vma_do_fault(walk, addr, write_fault, + &pfns[i]); + if (ret != -EAGAIN) + return ret; + } + } + + return (fault || write_fault) ? -EAGAIN : 0; +} + +static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk, + uint64_t pfns, uint64_t cpu_flags, + bool *fault, bool *write_fault) +{ + struct hmm_range *range = hmm_vma_walk->range; + + *fault = *write_fault = false; + if (!hmm_vma_walk->fault) + return; + + /* We aren't ask to do anything ... */ + if (!(pfns & range->flags[HMM_PFN_VALID])) + return; + /* If this is device memory than only fault if explicitly requested */ + if ((cpu_flags & range->flags[HMM_PFN_DEVICE_PRIVATE])) { + /* Do we fault on device memory ? */ + if (pfns & range->flags[HMM_PFN_DEVICE_PRIVATE]) { + *write_fault = pfns & range->flags[HMM_PFN_WRITE]; + *fault = true; + } + return; + } + + /* If CPU page table is not valid then we need to fault */ + *fault = !(cpu_flags & range->flags[HMM_PFN_VALID]); + /* Need to write fault ? */ + if ((pfns & range->flags[HMM_PFN_WRITE]) && + !(cpu_flags & range->flags[HMM_PFN_WRITE])) { + *write_fault = true; + *fault = true; + } +} + +static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk, + const uint64_t *pfns, unsigned long npages, + uint64_t cpu_flags, bool *fault, + bool *write_fault) +{ + unsigned long i; + + if (!hmm_vma_walk->fault) { + *fault = *write_fault = false; + return; + } + + for (i = 0; i < npages; ++i) { + hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags, + fault, write_fault); + if ((*fault) || (*write_fault)) + return; + } +} + +static int hmm_vma_walk_hole(unsigned long addr, unsigned long end, + struct mm_walk *walk) +{ + struct hmm_vma_walk *hmm_vma_walk = walk->private; + struct hmm_range *range = hmm_vma_walk->range; + bool fault, write_fault; + unsigned long i, npages; + uint64_t *pfns; + + i = (addr - range->start) >> PAGE_SHIFT; + npages = (end - addr) >> PAGE_SHIFT; + pfns = &range->pfns[i]; + hmm_range_need_fault(hmm_vma_walk, pfns, npages, + 0, &fault, &write_fault); + return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk); +} + +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]; +} + +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; + bool fault, write_fault; + uint64_t cpu_flags; + + npages = (end - addr) >> PAGE_SHIFT; + cpu_flags = pmd_to_hmm_pfn_flags(range, pmd); + hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags, + &fault, &write_fault); + + if (pmd_protnone(pmd) || fault || write_fault) + return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk); + + pfn = pmd_pfn(pmd) + pte_index(addr); + for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) + pfns[i] = hmm_pfn_from_pfn(range, pfn) | cpu_flags; + hmm_vma_walk->last = end; + return 0; +} + +static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte) +{ + if (pte_none(pte) || !pte_present(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; + struct vm_area_struct *vma = walk->vma; + bool fault, write_fault; + uint64_t cpu_flags; + pte_t pte = *ptep; + uint64_t orig_pfn = *pfn; + + *pfn = range->values[HMM_PFN_NONE]; + cpu_flags = pte_to_hmm_pfn_flags(range, pte); + hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags, + &fault, &write_fault); + + if (pte_none(pte)) { + if (fault || write_fault) + goto fault; + return 0; + } + + if (!pte_present(pte)) { + swp_entry_t entry = pte_to_swp_entry(pte); + + if (!non_swap_entry(entry)) { + if (fault || write_fault) + goto fault; + return 0; + } + + /* + * This is a special swap entry, ignore migration, use + * device and report anything else as error. + */ + if (is_device_private_entry(entry)) { + cpu_flags = range->flags[HMM_PFN_VALID] | + range->flags[HMM_PFN_DEVICE_PRIVATE]; + cpu_flags |= is_write_device_private_entry(entry) ? + range->flags[HMM_PFN_WRITE] : 0; + hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags, + &fault, &write_fault); + if (fault || write_fault) + goto fault; + *pfn = hmm_pfn_from_pfn(range, swp_offset(entry)); + *pfn |= cpu_flags; + return 0; + } + + if (is_migration_entry(entry)) { + if (fault || write_fault) { + pte_unmap(ptep); + hmm_vma_walk->last = addr; + migration_entry_wait(vma->vm_mm, + pmdp, addr); + return -EAGAIN; + } + return 0; + } + + /* Report error for everything else */ + *pfn = range->values[HMM_PFN_ERROR]; + return -EFAULT; + } + + if (fault || write_fault) + goto fault; + + *pfn = hmm_pfn_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_walk_hole_(addr, end, fault, write_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; + unsigned long addr = start, i; + pte_t *ptep; + + i = (addr - range->start) >> PAGE_SHIFT; + +again: + if (pmd_none(*pmdp)) + return hmm_vma_walk_hole(start, end, walk); + + if (pmd_huge(*pmdp) && (range->vma->vm_flags & VM_HUGETLB)) + return hmm_pfns_bad(start, end, walk); + + if (pmd_devmap(*pmdp) || pmd_trans_huge(*pmdp)) { + pmd_t pmd; + + /* + * No need to take pmd_lock here, even if some other threads + * is splitting the huge pmd we will get that event through + * mmu_notifier callback. + * + * So just read pmd value and check again its 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[i], pmd); + } + + if (pmd_bad(*pmdp)) + return hmm_pfns_bad(start, end, walk); + + ptep = pte_offset_map(pmdp, addr); + for (; addr < end; addr += PAGE_SIZE, ptep++, i++) { + int r; + + r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]); + if (r) { + /* hmm_vma_handle_pte() did unmap pte directory */ + hmm_vma_walk->last = addr; + return r; + } + } + pte_unmap(ptep - 1); + + hmm_vma_walk->last = addr; + return 0; +} + +static void hmm_pfns_clear(struct hmm_range *range, + uint64_t *pfns, + unsigned long addr, + unsigned long end) +{ + for (; addr < end; addr += PAGE_SIZE, pfns++) + *pfns = range->values[HMM_PFN_NONE]; +} + +static void hmm_pfns_special(struct hmm_range *range) +{ + unsigned long addr = range->start, i = 0; + + for (; addr < range->end; addr += PAGE_SIZE, i++) + range->pfns[i] = range->values[HMM_PFN_SPECIAL]; +} + +/* + * hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses + * @range: range being snapshotted + * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid + * vma permission, 0 success + * + * This snapshots the CPU page table for a range of virtual addresses. Snapshot + * validity is tracked by range struct. See hmm_vma_range_done() for further + * information. + * + * The range struct is initialized here. It tracks the CPU page table, but only + * if the function returns success (0), in which case the caller must then call + * hmm_vma_range_done() to stop CPU page table update tracking on this range. + * + * NOT CALLING hmm_vma_range_done() IF FUNCTION RETURNS 0 WILL LEAD TO SERIOUS + * MEMORY CORRUPTION ! YOU HAVE BEEN WARNED ! + */ +int hmm_vma_get_pfns(struct hmm_range *range) +{ + struct vm_area_struct *vma = range->vma; + struct hmm_vma_walk hmm_vma_walk; + struct mm_walk mm_walk; + struct hmm *hmm; + + /* Sanity check, this really should not happen ! */ + if (range->start < vma->vm_start || range->start >= vma->vm_end) + return -EINVAL; + if (range->end < vma->vm_start || range->end > vma->vm_end) + return -EINVAL; + + hmm = hmm_register(vma->vm_mm); + if (!hmm) + return -ENOMEM; + /* Caller must have registered a mirror, via hmm_mirror_register() ! */ + if (!hmm->mmu_notifier.ops) + return -EINVAL; + + /* FIXME support hugetlb fs */ + if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) || + vma_is_dax(vma)) { + hmm_pfns_special(range); + return -EINVAL; + } + + if (!(vma->vm_flags & VM_READ)) { + /* + * If vma do not allow read access, then assume that it does + * not allow write access, either. Architecture that allow + * write without read access are not supported by HMM, because + * operations such has atomic access would not work. + */ + hmm_pfns_clear(range, range->pfns, range->start, range->end); + return -EPERM; + } + + /* Initialize range to track CPU page table update */ + spin_lock(&hmm->lock); + range->valid = true; + list_add_rcu(&range->list, &hmm->ranges); + spin_unlock(&hmm->lock); + + hmm_vma_walk.fault = false; + hmm_vma_walk.range = range; + mm_walk.private = &hmm_vma_walk; + + mm_walk.vma = vma; + mm_walk.mm = vma->vm_mm; + mm_walk.pte_entry = NULL; + mm_walk.test_walk = NULL; + mm_walk.hugetlb_entry = NULL; + mm_walk.pmd_entry = hmm_vma_walk_pmd; + mm_walk.pte_hole = hmm_vma_walk_hole; + + walk_page_range(range->start, range->end, &mm_walk); + return 0; +} +EXPORT_SYMBOL(hmm_vma_get_pfns); + +/* + * hmm_vma_range_done() - stop tracking change to CPU page table over a range + * @range: range being tracked + * Returns: false if range data has been invalidated, true otherwise + * + * Range struct is used to track updates to the CPU page table after a call to + * either hmm_vma_get_pfns() or hmm_vma_fault(). Once the device driver is done + * using the data, or wants to lock updates to the data it got from those + * functions, it must call the hmm_vma_range_done() function, which will then + * stop tracking CPU page table updates. + * + * Note that device driver must still implement general CPU page table update + * tracking either by using hmm_mirror (see hmm_mirror_register()) or by using + * the mmu_notifier API directly. + * + * CPU page table update tracking done through hmm_range is only temporary and + * to be used while trying to duplicate CPU page table contents for a range of + * virtual addresses. + * + * There are two ways to use this : + * again: + * hmm_vma_get_pfns(range); or hmm_vma_fault(...); + * trans = device_build_page_table_update_transaction(pfns); + * device_page_table_lock(); + * if (!hmm_vma_range_done(range)) { + * device_page_table_unlock(); + * goto again; + * } + * device_commit_transaction(trans); + * device_page_table_unlock(); + * + * Or: + * hmm_vma_get_pfns(range); or hmm_vma_fault(...); + * device_page_table_lock(); + * hmm_vma_range_done(range); + * device_update_page_table(range->pfns); + * device_page_table_unlock(); + */ +bool hmm_vma_range_done(struct hmm_range *range) +{ + unsigned long npages = (range->end - range->start) >> PAGE_SHIFT; + struct hmm *hmm; + + if (range->end <= range->start) { + BUG(); + return false; + } + + hmm = hmm_register(range->vma->vm_mm); + if (!hmm) { + memset(range->pfns, 0, sizeof(*range->pfns) * npages); + return false; + } + + spin_lock(&hmm->lock); + list_del_rcu(&range->list); + spin_unlock(&hmm->lock); + + return range->valid; +} +EXPORT_SYMBOL(hmm_vma_range_done); + +/* + * hmm_vma_fault() - try to fault some address in a virtual address range + * @range: range being faulted + * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem) + * Returns: 0 success, error otherwise (-EAGAIN means mmap_sem have been drop) + * + * This is similar to a regular CPU page fault except that it will not trigger + * any memory migration if the memory being faulted is not accessible by CPUs. + * + * On error, for one virtual address in the range, the function will mark the + * corresponding HMM pfn entry with an error flag. + * + * Expected use pattern: + * retry: + * down_read(&mm->mmap_sem); + * // Find vma and address device wants to fault, initialize hmm_pfn_t + * // array accordingly + * ret = hmm_vma_fault(range, write, block); + * switch (ret) { + * case -EAGAIN: + * hmm_vma_range_done(range); + * // You might want to rate limit or yield to play nicely, you may + * // also commit any valid pfn in the array assuming that you are + * // getting true from hmm_vma_range_monitor_end() + * goto retry; + * case 0: + * break; + * case -ENOMEM: + * case -EINVAL: + * case -EPERM: + * default: + * // Handle error ! + * up_read(&mm->mmap_sem) + * return; + * } + * // Take device driver lock that serialize device page table update + * driver_lock_device_page_table_update(); + * hmm_vma_range_done(range); + * // Commit pfns we got from hmm_vma_fault() + * driver_unlock_device_page_table_update(); + * up_read(&mm->mmap_sem) + * + * YOU MUST CALL hmm_vma_range_done() AFTER THIS FUNCTION RETURN SUCCESS (0) + * BEFORE FREEING THE range struct OR YOU WILL HAVE SERIOUS MEMORY CORRUPTION ! + * + * YOU HAVE BEEN WARNED ! + */ +int hmm_vma_fault(struct hmm_range *range, bool block) +{ + struct vm_area_struct *vma = range->vma; + unsigned long start = range->start; + struct hmm_vma_walk hmm_vma_walk; + struct mm_walk mm_walk; + struct hmm *hmm; + int ret; + + /* Sanity check, this really should not happen ! */ + if (range->start < vma->vm_start || range->start >= vma->vm_end) + return -EINVAL; + if (range->end < vma->vm_start || range->end > vma->vm_end) + return -EINVAL; + + hmm = hmm_register(vma->vm_mm); + if (!hmm) { + hmm_pfns_clear(range, range->pfns, range->start, range->end); + return -ENOMEM; + } + /* Caller must have registered a mirror using hmm_mirror_register() */ + if (!hmm->mmu_notifier.ops) + return -EINVAL; + + /* FIXME support hugetlb fs */ + if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) || + vma_is_dax(vma)) { + hmm_pfns_special(range); + return -EINVAL; + } + + if (!(vma->vm_flags & VM_READ)) { + /* + * If vma do not allow read access, then assume that it does + * not allow write access, either. Architecture that allow + * write without read access are not supported by HMM, because + * operations such has atomic access would not work. + */ + hmm_pfns_clear(range, range->pfns, range->start, range->end); + return -EPERM; + } + + /* Initialize range to track CPU page table update */ + spin_lock(&hmm->lock); + range->valid = true; + list_add_rcu(&range->list, &hmm->ranges); + spin_unlock(&hmm->lock); + + hmm_vma_walk.fault = true; + hmm_vma_walk.block = block; + hmm_vma_walk.range = range; + mm_walk.private = &hmm_vma_walk; + hmm_vma_walk.last = range->start; + + mm_walk.vma = vma; + mm_walk.mm = vma->vm_mm; + mm_walk.pte_entry = NULL; + mm_walk.test_walk = NULL; + mm_walk.hugetlb_entry = NULL; + mm_walk.pmd_entry = hmm_vma_walk_pmd; + mm_walk.pte_hole = hmm_vma_walk_hole; + + do { + ret = walk_page_range(start, range->end, &mm_walk); + start = hmm_vma_walk.last; + } while (ret == -EAGAIN); + + if (ret) { + unsigned long i; + + i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT; + hmm_pfns_clear(range, &range->pfns[i], hmm_vma_walk.last, + range->end); + hmm_vma_range_done(range); + } + return ret; +} +EXPORT_SYMBOL(hmm_vma_fault); +#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */ + + +#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) || IS_ENABLED(CONFIG_DEVICE_PUBLIC) +struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma, + unsigned long addr) +{ + struct page *page; + + page = alloc_page_vma(GFP_HIGHUSER, vma, addr); + if (!page) + return NULL; + lock_page(page); + return page; +} +EXPORT_SYMBOL(hmm_vma_alloc_locked_page); + + +static void hmm_devmem_ref_release(struct percpu_ref *ref) +{ + struct hmm_devmem *devmem; + + devmem = container_of(ref, struct hmm_devmem, ref); + complete(&devmem->completion); +} + +static void hmm_devmem_ref_exit(void *data) +{ + struct percpu_ref *ref = data; + struct hmm_devmem *devmem; + + devmem = container_of(ref, struct hmm_devmem, ref); + percpu_ref_exit(ref); +} + +static void hmm_devmem_ref_kill(void *data) +{ + struct percpu_ref *ref = data; + struct hmm_devmem *devmem; + + devmem = container_of(ref, struct hmm_devmem, ref); + percpu_ref_kill(ref); + wait_for_completion(&devmem->completion); +} + +static int hmm_devmem_fault(struct vm_area_struct *vma, + unsigned long addr, + const struct page *page, + unsigned int flags, + pmd_t *pmdp) +{ + struct hmm_devmem *devmem = page->pgmap->data; + + return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp); +} + +static void hmm_devmem_free(struct page *page, void *data) +{ + struct hmm_devmem *devmem = data; + + page->mapping = NULL; + + devmem->ops->free(devmem, page); +} + +static DEFINE_MUTEX(hmm_devmem_lock); +static RADIX_TREE(hmm_devmem_radix, GFP_KERNEL); + +static void hmm_devmem_radix_release(struct resource *resource) +{ + resource_size_t key; + + mutex_lock(&hmm_devmem_lock); + for (key = resource->start; + key <= resource->end; + key += PA_SECTION_SIZE) + radix_tree_delete(&hmm_devmem_radix, key >> PA_SECTION_SHIFT); + mutex_unlock(&hmm_devmem_lock); +} + +static void hmm_devmem_release(void *data) +{ + struct hmm_devmem *devmem = data; + struct resource *resource = devmem->resource; + unsigned long start_pfn, npages; + struct page *page; + int nid; + + /* pages are dead and unused, undo the arch mapping */ + start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT; + npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT; + + page = pfn_to_page(start_pfn); + nid = page_to_nid(page); + + mem_hotplug_begin(); + if (resource->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) + __remove_pages(start_pfn, npages, NULL); + else + arch_remove_memory(nid, start_pfn << PAGE_SHIFT, + npages << PAGE_SHIFT, NULL); + mem_hotplug_done(); + + hmm_devmem_radix_release(resource); +} + +static int hmm_devmem_pages_create(struct hmm_devmem *devmem) +{ + resource_size_t key, align_start, align_size, align_end; + struct device *device = devmem->device; + int ret, nid, is_ram; + unsigned long pfn; + + align_start = devmem->resource->start & ~(PA_SECTION_SIZE - 1); + align_size = ALIGN(devmem->resource->start + + resource_size(devmem->resource), + PA_SECTION_SIZE) - align_start; + + is_ram = region_intersects(align_start, align_size, + IORESOURCE_SYSTEM_RAM, + IORES_DESC_NONE); + if (is_ram == REGION_MIXED) { + WARN_ONCE(1, "%s attempted on mixed region %pr\n", + __func__, devmem->resource); + return -ENXIO; + } + if (is_ram == REGION_INTERSECTS) + return -ENXIO; + + if (devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY) + devmem->pagemap.type = MEMORY_DEVICE_PUBLIC; + else + devmem->pagemap.type = MEMORY_DEVICE_PRIVATE; + + devmem->pagemap.res = *devmem->resource; + devmem->pagemap.page_fault = hmm_devmem_fault; + devmem->pagemap.page_free = hmm_devmem_free; + devmem->pagemap.dev = devmem->device; + devmem->pagemap.ref = &devmem->ref; + devmem->pagemap.data = devmem; + + mutex_lock(&hmm_devmem_lock); + align_end = align_start + align_size - 1; + for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) { + struct hmm_devmem *dup; + + dup = radix_tree_lookup(&hmm_devmem_radix, + key >> PA_SECTION_SHIFT); + if (dup) { + dev_err(device, "%s: collides with mapping for %s\n", + __func__, dev_name(dup->device)); + mutex_unlock(&hmm_devmem_lock); + ret = -EBUSY; + goto error; + } + ret = radix_tree_insert(&hmm_devmem_radix, + key >> PA_SECTION_SHIFT, + devmem); + if (ret) { + dev_err(device, "%s: failed: %d\n", __func__, ret); + mutex_unlock(&hmm_devmem_lock); + goto error_radix; + } + } + mutex_unlock(&hmm_devmem_lock); + + nid = dev_to_node(device); + if (nid < 0) + nid = numa_mem_id(); + + mem_hotplug_begin(); + /* + * For device private memory we call add_pages() as we only need to + * allocate and initialize struct page for the device memory. More- + * over the device memory is un-accessible thus we do not want to + * create a linear mapping for the memory like arch_add_memory() + * would do. + * + * For device public memory, which is accesible by the CPU, we do + * want the linear mapping and thus use arch_add_memory(). + */ + if (devmem->pagemap.type == MEMORY_DEVICE_PUBLIC) + ret = arch_add_memory(nid, align_start, align_size, NULL, + false); + else + ret = add_pages(nid, align_start >> PAGE_SHIFT, + align_size >> PAGE_SHIFT, NULL, false); + if (ret) { + mem_hotplug_done(); + goto error_add_memory; + } + move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE], + align_start >> PAGE_SHIFT, + align_size >> PAGE_SHIFT, NULL); + mem_hotplug_done(); + + for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) { + struct page *page = pfn_to_page(pfn); + + page->pgmap = &devmem->pagemap; + } + return 0; + +error_add_memory: + untrack_pfn(NULL, PHYS_PFN(align_start), align_size); +error_radix: + hmm_devmem_radix_release(devmem->resource); +error: + return ret; +} + +/* + * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory + * + * @ops: memory event device driver callback (see struct hmm_devmem_ops) + * @device: device struct to bind the resource too + * @size: size in bytes of the device memory to add + * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise + * + * This function first finds an empty range of physical address big enough to + * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which + * in turn allocates struct pages. It does not do anything beyond that; all + * events affecting the memory will go through the various callbacks provided + * by hmm_devmem_ops struct. + * + * Device driver should call this function during device initialization and + * is then responsible of memory management. HMM only provides helpers. + */ +struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops, + struct device *device, + unsigned long size) +{ + struct hmm_devmem *devmem; + resource_size_t addr; + int ret; + + dev_pagemap_get_ops(); + + devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL); + if (!devmem) + return ERR_PTR(-ENOMEM); + + init_completion(&devmem->completion); + devmem->pfn_first = -1UL; + devmem->pfn_last = -1UL; + devmem->resource = NULL; + devmem->device = device; + devmem->ops = ops; + + ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release, + 0, GFP_KERNEL); + if (ret) + return ERR_PTR(ret); + + ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit, &devmem->ref); + if (ret) + return ERR_PTR(ret); + + size = ALIGN(size, PA_SECTION_SIZE); + addr = min((unsigned long)iomem_resource.end, + (1UL << MAX_PHYSMEM_BITS) - 1); + addr = addr - size + 1UL; + + /* + * FIXME add a new helper to quickly walk resource tree and find free + * range + * + * FIXME what about ioport_resource resource ? + */ + for (; addr > size && addr >= iomem_resource.start; addr -= size) { + ret = region_intersects(addr, size, 0, IORES_DESC_NONE); + if (ret != REGION_DISJOINT) + continue; + + devmem->resource = devm_request_mem_region(device, addr, size, + dev_name(device)); + if (!devmem->resource) + return ERR_PTR(-ENOMEM); + break; + } + if (!devmem->resource) + return ERR_PTR(-ERANGE); + + devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY; + devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT; + devmem->pfn_last = devmem->pfn_first + + (resource_size(devmem->resource) >> PAGE_SHIFT); + + ret = hmm_devmem_pages_create(devmem); + if (ret) + return ERR_PTR(ret); + + ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem); + if (ret) + return ERR_PTR(ret); + + return devmem; +} +EXPORT_SYMBOL_GPL(hmm_devmem_add); + +struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops, + struct device *device, + struct resource *res) +{ + struct hmm_devmem *devmem; + int ret; + + if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY) + return ERR_PTR(-EINVAL); + + dev_pagemap_get_ops(); + + devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL); + if (!devmem) + return ERR_PTR(-ENOMEM); + + init_completion(&devmem->completion); + devmem->pfn_first = -1UL; + devmem->pfn_last = -1UL; + devmem->resource = res; + devmem->device = device; + devmem->ops = ops; + + ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release, + 0, GFP_KERNEL); + if (ret) + return ERR_PTR(ret); + + ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit, + &devmem->ref); + if (ret) + return ERR_PTR(ret); + + devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT; + devmem->pfn_last = devmem->pfn_first + + (resource_size(devmem->resource) >> PAGE_SHIFT); + + ret = hmm_devmem_pages_create(devmem); + if (ret) + return ERR_PTR(ret); + + ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem); + if (ret) + return ERR_PTR(ret); + + ret = devm_add_action_or_reset(device, hmm_devmem_ref_kill, + &devmem->ref); + if (ret) + return ERR_PTR(ret); + + return devmem; +} +EXPORT_SYMBOL_GPL(hmm_devmem_add_resource); + +/* + * A device driver that wants to handle multiple devices memory through a + * single fake device can use hmm_device to do so. This is purely a helper + * and it is not needed to make use of any HMM functionality. + */ +#define HMM_DEVICE_MAX 256 + +static DECLARE_BITMAP(hmm_device_mask, HMM_DEVICE_MAX); +static DEFINE_SPINLOCK(hmm_device_lock); +static struct class *hmm_device_class; +static dev_t hmm_device_devt; + +static void hmm_device_release(struct device *device) +{ + struct hmm_device *hmm_device; + + hmm_device = container_of(device, struct hmm_device, device); + spin_lock(&hmm_device_lock); + clear_bit(hmm_device->minor, hmm_device_mask); + spin_unlock(&hmm_device_lock); + + kfree(hmm_device); +} + +struct hmm_device *hmm_device_new(void *drvdata) +{ + struct hmm_device *hmm_device; + + hmm_device = kzalloc(sizeof(*hmm_device), GFP_KERNEL); + if (!hmm_device) + return ERR_PTR(-ENOMEM); + + spin_lock(&hmm_device_lock); + hmm_device->minor = find_first_zero_bit(hmm_device_mask, HMM_DEVICE_MAX); + if (hmm_device->minor >= HMM_DEVICE_MAX) { + spin_unlock(&hmm_device_lock); + kfree(hmm_device); + return ERR_PTR(-EBUSY); + } + set_bit(hmm_device->minor, hmm_device_mask); + spin_unlock(&hmm_device_lock); + + dev_set_name(&hmm_device->device, "hmm_device%d", hmm_device->minor); + hmm_device->device.devt = MKDEV(MAJOR(hmm_device_devt), + hmm_device->minor); + hmm_device->device.release = hmm_device_release; + dev_set_drvdata(&hmm_device->device, drvdata); + hmm_device->device.class = hmm_device_class; + device_initialize(&hmm_device->device); + + return hmm_device; +} +EXPORT_SYMBOL(hmm_device_new); + +void hmm_device_put(struct hmm_device *hmm_device) +{ + put_device(&hmm_device->device); +} +EXPORT_SYMBOL(hmm_device_put); + +static int __init hmm_init(void) +{ + int ret; + + ret = alloc_chrdev_region(&hmm_device_devt, 0, + HMM_DEVICE_MAX, + "hmm_device"); + if (ret) + return ret; + + hmm_device_class = class_create(THIS_MODULE, "hmm_device"); + if (IS_ERR(hmm_device_class)) { + unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX); + return PTR_ERR(hmm_device_class); + } + return 0; +} + +device_initcall(hmm_init); +#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */ |