/* * SPDX-License-Identifier: MIT * * Copyright © 2012-2014 Intel Corporation */ #include #include #include #include #include #include "i915_drv.h" #include "i915_gem_ioctls.h" #include "i915_gem_object.h" #include "i915_scatterlist.h" struct i915_mm_struct { struct mm_struct *mm; struct drm_i915_private *i915; struct i915_mmu_notifier *mn; struct hlist_node node; struct kref kref; struct rcu_work work; }; #if defined(CONFIG_MMU_NOTIFIER) #include struct i915_mmu_notifier { spinlock_t lock; struct hlist_node node; struct mmu_notifier mn; struct rb_root_cached objects; struct i915_mm_struct *mm; }; struct i915_mmu_object { struct i915_mmu_notifier *mn; struct drm_i915_gem_object *obj; struct interval_tree_node it; }; static void add_object(struct i915_mmu_object *mo) { GEM_BUG_ON(!RB_EMPTY_NODE(&mo->it.rb)); interval_tree_insert(&mo->it, &mo->mn->objects); } static void del_object(struct i915_mmu_object *mo) { if (RB_EMPTY_NODE(&mo->it.rb)) return; interval_tree_remove(&mo->it, &mo->mn->objects); RB_CLEAR_NODE(&mo->it.rb); } static void __i915_gem_userptr_set_active(struct drm_i915_gem_object *obj, bool value) { struct i915_mmu_object *mo = obj->userptr.mmu_object; /* * During mm_invalidate_range we need to cancel any userptr that * overlaps the range being invalidated. Doing so requires the * struct_mutex, and that risks recursion. In order to cause * recursion, the user must alias the userptr address space with * a GTT mmapping (possible with a MAP_FIXED) - then when we have * to invalidate that mmaping, mm_invalidate_range is called with * the userptr address *and* the struct_mutex held. To prevent that * we set a flag under the i915_mmu_notifier spinlock to indicate * whether this object is valid. */ if (!mo) return; spin_lock(&mo->mn->lock); if (value) add_object(mo); else del_object(mo); spin_unlock(&mo->mn->lock); } static int userptr_mn_invalidate_range_start(struct mmu_notifier *_mn, const struct mmu_notifier_range *range) { struct i915_mmu_notifier *mn = container_of(_mn, struct i915_mmu_notifier, mn); struct interval_tree_node *it; unsigned long end; int ret = 0; if (RB_EMPTY_ROOT(&mn->objects.rb_root)) return 0; /* interval ranges are inclusive, but invalidate range is exclusive */ end = range->end - 1; spin_lock(&mn->lock); it = interval_tree_iter_first(&mn->objects, range->start, end); while (it) { struct drm_i915_gem_object *obj; if (!mmu_notifier_range_blockable(range)) { ret = -EAGAIN; break; } /* * The mmu_object is released late when destroying the * GEM object so it is entirely possible to gain a * reference on an object in the process of being freed * since our serialisation is via the spinlock and not * the struct_mutex - and consequently use it after it * is freed and then double free it. To prevent that * use-after-free we only acquire a reference on the * object if it is not in the process of being destroyed. */ obj = container_of(it, struct i915_mmu_object, it)->obj; if (!kref_get_unless_zero(&obj->base.refcount)) { it = interval_tree_iter_next(it, range->start, end); continue; } spin_unlock(&mn->lock); ret = i915_gem_object_unbind(obj, I915_GEM_OBJECT_UNBIND_ACTIVE | I915_GEM_OBJECT_UNBIND_BARRIER); if (ret == 0) ret = __i915_gem_object_put_pages(obj); i915_gem_object_put(obj); if (ret) return ret; spin_lock(&mn->lock); /* * As we do not (yet) protect the mmu from concurrent insertion * over this range, there is no guarantee that this search will * terminate given a pathologic workload. */ it = interval_tree_iter_first(&mn->objects, range->start, end); } spin_unlock(&mn->lock); return ret; } static const struct mmu_notifier_ops i915_gem_userptr_notifier = { .invalidate_range_start = userptr_mn_invalidate_range_start, }; static struct i915_mmu_notifier * i915_mmu_notifier_create(struct i915_mm_struct *mm) { struct i915_mmu_notifier *mn; mn = kmalloc(sizeof(*mn), GFP_KERNEL); if (mn == NULL) return ERR_PTR(-ENOMEM); spin_lock_init(&mn->lock); mn->mn.ops = &i915_gem_userptr_notifier; mn->objects = RB_ROOT_CACHED; mn->mm = mm; return mn; } static void i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj) { struct i915_mmu_object *mo; mo = fetch_and_zero(&obj->userptr.mmu_object); if (!mo) return; spin_lock(&mo->mn->lock); del_object(mo); spin_unlock(&mo->mn->lock); kfree(mo); } static struct i915_mmu_notifier * i915_mmu_notifier_find(struct i915_mm_struct *mm) { struct i915_mmu_notifier *mn, *old; int err; mn = READ_ONCE(mm->mn); if (likely(mn)) return mn; mn = i915_mmu_notifier_create(mm); if (IS_ERR(mn)) return mn; err = mmu_notifier_register(&mn->mn, mm->mm); if (err) { kfree(mn); return ERR_PTR(err); } old = cmpxchg(&mm->mn, NULL, mn); if (old) { mmu_notifier_unregister(&mn->mn, mm->mm); kfree(mn); mn = old; } return mn; } static int i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj, unsigned flags) { struct i915_mmu_notifier *mn; struct i915_mmu_object *mo; if (flags & I915_USERPTR_UNSYNCHRONIZED) return capable(CAP_SYS_ADMIN) ? 0 : -EPERM; if (GEM_WARN_ON(!obj->userptr.mm)) return -EINVAL; mn = i915_mmu_notifier_find(obj->userptr.mm); if (IS_ERR(mn)) return PTR_ERR(mn); mo = kzalloc(sizeof(*mo), GFP_KERNEL); if (!mo) return -ENOMEM; mo->mn = mn; mo->obj = obj; mo->it.start = obj->userptr.ptr; mo->it.last = obj->userptr.ptr + obj->base.size - 1; RB_CLEAR_NODE(&mo->it.rb); obj->userptr.mmu_object = mo; return 0; } static void i915_mmu_notifier_free(struct i915_mmu_notifier *mn, struct mm_struct *mm) { if (mn == NULL) return; mmu_notifier_unregister(&mn->mn, mm); kfree(mn); } #else static void __i915_gem_userptr_set_active(struct drm_i915_gem_object *obj, bool value) { } static void i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj) { } static int i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj, unsigned flags) { if ((flags & I915_USERPTR_UNSYNCHRONIZED) == 0) return -ENODEV; if (!capable(CAP_SYS_ADMIN)) return -EPERM; return 0; } static void i915_mmu_notifier_free(struct i915_mmu_notifier *mn, struct mm_struct *mm) { } #endif static struct i915_mm_struct * __i915_mm_struct_find(struct drm_i915_private *i915, struct mm_struct *real) { struct i915_mm_struct *it, *mm = NULL; rcu_read_lock(); hash_for_each_possible_rcu(i915->mm_structs, it, node, (unsigned long)real) if (it->mm == real && kref_get_unless_zero(&it->kref)) { mm = it; break; } rcu_read_unlock(); return mm; } static int i915_gem_userptr_init__mm_struct(struct drm_i915_gem_object *obj) { struct drm_i915_private *i915 = to_i915(obj->base.dev); struct i915_mm_struct *mm, *new; int ret = 0; /* During release of the GEM object we hold the struct_mutex. This * precludes us from calling mmput() at that time as that may be * the last reference and so call exit_mmap(). exit_mmap() will * attempt to reap the vma, and if we were holding a GTT mmap * would then call drm_gem_vm_close() and attempt to reacquire * the struct mutex. So in order to avoid that recursion, we have * to defer releasing the mm reference until after we drop the * struct_mutex, i.e. we need to schedule a worker to do the clean * up. */ mm = __i915_mm_struct_find(i915, current->mm); if (mm) goto out; new = kmalloc(sizeof(*mm), GFP_KERNEL); if (!new) return -ENOMEM; kref_init(&new->kref); new->i915 = to_i915(obj->base.dev); new->mm = current->mm; new->mn = NULL; spin_lock(&i915->mm_lock); mm = __i915_mm_struct_find(i915, current->mm); if (!mm) { hash_add_rcu(i915->mm_structs, &new->node, (unsigned long)new->mm); mmgrab(current->mm); mm = new; } spin_unlock(&i915->mm_lock); if (mm != new) kfree(new); out: obj->userptr.mm = mm; return ret; } static void __i915_mm_struct_free__worker(struct work_struct *work) { struct i915_mm_struct *mm = container_of(work, typeof(*mm), work.work); i915_mmu_notifier_free(mm->mn, mm->mm); mmdrop(mm->mm); kfree(mm); } static void __i915_mm_struct_free(struct kref *kref) { struct i915_mm_struct *mm = container_of(kref, typeof(*mm), kref); spin_lock(&mm->i915->mm_lock); hash_del_rcu(&mm->node); spin_unlock(&mm->i915->mm_lock); INIT_RCU_WORK(&mm->work, __i915_mm_struct_free__worker); queue_rcu_work(system_wq, &mm->work); } static void i915_gem_userptr_release__mm_struct(struct drm_i915_gem_object *obj) { if (obj->userptr.mm == NULL) return; kref_put(&obj->userptr.mm->kref, __i915_mm_struct_free); obj->userptr.mm = NULL; } struct get_pages_work { struct work_struct work; struct drm_i915_gem_object *obj; struct task_struct *task; }; static struct sg_table * __i915_gem_userptr_alloc_pages(struct drm_i915_gem_object *obj, struct page **pvec, unsigned long num_pages) { unsigned int max_segment = i915_sg_segment_size(); struct sg_table *st; unsigned int sg_page_sizes; int ret; st = kmalloc(sizeof(*st), GFP_KERNEL); if (!st) return ERR_PTR(-ENOMEM); alloc_table: ret = __sg_alloc_table_from_pages(st, pvec, num_pages, 0, num_pages << PAGE_SHIFT, max_segment, GFP_KERNEL); if (ret) { kfree(st); return ERR_PTR(ret); } ret = i915_gem_gtt_prepare_pages(obj, st); if (ret) { sg_free_table(st); if (max_segment > PAGE_SIZE) { max_segment = PAGE_SIZE; goto alloc_table; } kfree(st); return ERR_PTR(ret); } sg_page_sizes = i915_sg_page_sizes(st->sgl); __i915_gem_object_set_pages(obj, st, sg_page_sizes); return st; } static void __i915_gem_userptr_get_pages_worker(struct work_struct *_work) { struct get_pages_work *work = container_of(_work, typeof(*work), work); struct drm_i915_gem_object *obj = work->obj; const unsigned long npages = obj->base.size >> PAGE_SHIFT; unsigned long pinned; struct page **pvec; int ret; ret = -ENOMEM; pinned = 0; pvec = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL); if (pvec != NULL) { struct mm_struct *mm = obj->userptr.mm->mm; unsigned int flags = 0; int locked = 0; if (!i915_gem_object_is_readonly(obj)) flags |= FOLL_WRITE; ret = -EFAULT; if (mmget_not_zero(mm)) { while (pinned < npages) { if (!locked) { mmap_read_lock(mm); locked = 1; } ret = pin_user_pages_remote (work->task, mm, obj->userptr.ptr + pinned * PAGE_SIZE, npages - pinned, flags, pvec + pinned, NULL, &locked); if (ret < 0) break; pinned += ret; } if (locked) mmap_read_unlock(mm); mmput(mm); } } mutex_lock_nested(&obj->mm.lock, I915_MM_GET_PAGES); if (obj->userptr.work == &work->work) { struct sg_table *pages = ERR_PTR(ret); if (pinned == npages) { pages = __i915_gem_userptr_alloc_pages(obj, pvec, npages); if (!IS_ERR(pages)) { pinned = 0; pages = NULL; } } obj->userptr.work = ERR_CAST(pages); if (IS_ERR(pages)) __i915_gem_userptr_set_active(obj, false); } mutex_unlock(&obj->mm.lock); unpin_user_pages(pvec, pinned); kvfree(pvec); i915_gem_object_put(obj); put_task_struct(work->task); kfree(work); } static struct sg_table * __i915_gem_userptr_get_pages_schedule(struct drm_i915_gem_object *obj) { struct get_pages_work *work; /* Spawn a worker so that we can acquire the * user pages without holding our mutex. Access * to the user pages requires mmap_lock, and we have * a strict lock ordering of mmap_lock, struct_mutex - * we already hold struct_mutex here and so cannot * call gup without encountering a lock inversion. * * Userspace will keep on repeating the operation * (thanks to EAGAIN) until either we hit the fast * path or the worker completes. If the worker is * cancelled or superseded, the task is still run * but the results ignored. (This leads to * complications that we may have a stray object * refcount that we need to be wary of when * checking for existing objects during creation.) * If the worker encounters an error, it reports * that error back to this function through * obj->userptr.work = ERR_PTR. */ work = kmalloc(sizeof(*work), GFP_KERNEL); if (work == NULL) return ERR_PTR(-ENOMEM); obj->userptr.work = &work->work; work->obj = i915_gem_object_get(obj); work->task = current; get_task_struct(work->task); INIT_WORK(&work->work, __i915_gem_userptr_get_pages_worker); queue_work(to_i915(obj->base.dev)->mm.userptr_wq, &work->work); return ERR_PTR(-EAGAIN); } static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj) { const unsigned long num_pages = obj->base.size >> PAGE_SHIFT; struct mm_struct *mm = obj->userptr.mm->mm; struct page **pvec; struct sg_table *pages; bool active; int pinned; unsigned int gup_flags = 0; /* If userspace should engineer that these pages are replaced in * the vma between us binding this page into the GTT and completion * of rendering... Their loss. If they change the mapping of their * pages they need to create a new bo to point to the new vma. * * However, that still leaves open the possibility of the vma * being copied upon fork. Which falls under the same userspace * synchronisation issue as a regular bo, except that this time * the process may not be expecting that a particular piece of * memory is tied to the GPU. * * Fortunately, we can hook into the mmu_notifier in order to * discard the page references prior to anything nasty happening * to the vma (discard or cloning) which should prevent the more * egregious cases from causing harm. */ if (obj->userptr.work) { /* active flag should still be held for the pending work */ if (IS_ERR(obj->userptr.work)) return PTR_ERR(obj->userptr.work); else return -EAGAIN; } pvec = NULL; pinned = 0; if (mm == current->mm) { pvec = kvmalloc_array(num_pages, sizeof(struct page *), GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN); /* * Using __get_user_pages_fast() with a read-only * access is questionable. A read-only page may be * COW-broken, and then this might end up giving * the wrong side of the COW.. * * We may or may not care. */ if (pvec) { /* defer to worker if malloc fails */ if (!i915_gem_object_is_readonly(obj)) gup_flags |= FOLL_WRITE; pinned = pin_user_pages_fast_only(obj->userptr.ptr, num_pages, gup_flags, pvec); } } active = false; if (pinned < 0) { pages = ERR_PTR(pinned); pinned = 0; } else if (pinned < num_pages) { pages = __i915_gem_userptr_get_pages_schedule(obj); active = pages == ERR_PTR(-EAGAIN); } else { pages = __i915_gem_userptr_alloc_pages(obj, pvec, num_pages); active = !IS_ERR(pages); } if (active) __i915_gem_userptr_set_active(obj, true); if (IS_ERR(pages)) unpin_user_pages(pvec, pinned); kvfree(pvec); return PTR_ERR_OR_ZERO(pages); } static void i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj, struct sg_table *pages) { struct sgt_iter sgt_iter; struct page *page; /* Cancel any inflight work and force them to restart their gup */ obj->userptr.work = NULL; __i915_gem_userptr_set_active(obj, false); if (!pages) return; __i915_gem_object_release_shmem(obj, pages, true); i915_gem_gtt_finish_pages(obj, pages); /* * We always mark objects as dirty when they are used by the GPU, * just in case. However, if we set the vma as being read-only we know * that the object will never have been written to. */ if (i915_gem_object_is_readonly(obj)) obj->mm.dirty = false; for_each_sgt_page(page, sgt_iter, pages) { if (obj->mm.dirty && trylock_page(page)) { /* * As this may not be anonymous memory (e.g. shmem) * but exist on a real mapping, we have to lock * the page in order to dirty it -- holding * the page reference is not sufficient to * prevent the inode from being truncated. * Play safe and take the lock. * * However...! * * The mmu-notifier can be invalidated for a * migrate_page, that is alreadying holding the lock * on the page. Such a try_to_unmap() will result * in us calling put_pages() and so recursively try * to lock the page. We avoid that deadlock with * a trylock_page() and in exchange we risk missing * some page dirtying. */ set_page_dirty(page); unlock_page(page); } mark_page_accessed(page); unpin_user_page(page); } obj->mm.dirty = false; sg_free_table(pages); kfree(pages); } static void i915_gem_userptr_release(struct drm_i915_gem_object *obj) { i915_gem_userptr_release__mmu_notifier(obj); i915_gem_userptr_release__mm_struct(obj); } static int i915_gem_userptr_dmabuf_export(struct drm_i915_gem_object *obj) { if (obj->userptr.mmu_object) return 0; return i915_gem_userptr_init__mmu_notifier(obj, 0); } static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = { .name = "i915_gem_object_userptr", .flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE | I915_GEM_OBJECT_IS_SHRINKABLE | I915_GEM_OBJECT_NO_MMAP | I915_GEM_OBJECT_ASYNC_CANCEL, .get_pages = i915_gem_userptr_get_pages, .put_pages = i915_gem_userptr_put_pages, .dmabuf_export = i915_gem_userptr_dmabuf_export, .release = i915_gem_userptr_release, }; /* * Creates a new mm object that wraps some normal memory from the process * context - user memory. * * We impose several restrictions upon the memory being mapped * into the GPU. * 1. It must be page aligned (both start/end addresses, i.e ptr and size). * 2. It must be normal system memory, not a pointer into another map of IO * space (e.g. it must not be a GTT mmapping of another object). * 3. We only allow a bo as large as we could in theory map into the GTT, * that is we limit the size to the total size of the GTT. * 4. The bo is marked as being snoopable. The backing pages are left * accessible directly by the CPU, but reads and writes by the GPU may * incur the cost of a snoop (unless you have an LLC architecture). * * Synchronisation between multiple users and the GPU is left to userspace * through the normal set-domain-ioctl. The kernel will enforce that the * GPU relinquishes the VMA before it is returned back to the system * i.e. upon free(), munmap() or process termination. However, the userspace * malloc() library may not immediately relinquish the VMA after free() and * instead reuse it whilst the GPU is still reading and writing to the VMA. * Caveat emptor. * * Also note, that the object created here is not currently a "first class" * object, in that several ioctls are banned. These are the CPU access * ioctls: mmap(), pwrite and pread. In practice, you are expected to use * direct access via your pointer rather than use those ioctls. Another * restriction is that we do not allow userptr surfaces to be pinned to the * hardware and so we reject any attempt to create a framebuffer out of a * userptr. * * If you think this is a good interface to use to pass GPU memory between * drivers, please use dma-buf instead. In fact, wherever possible use * dma-buf instead. */ int i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file) { static struct lock_class_key lock_class; struct drm_i915_private *dev_priv = to_i915(dev); struct drm_i915_gem_userptr *args = data; struct drm_i915_gem_object *obj; int ret; u32 handle; if (!HAS_LLC(dev_priv) && !HAS_SNOOP(dev_priv)) { /* We cannot support coherent userptr objects on hw without * LLC and broken snooping. */ return -ENODEV; } if (args->flags & ~(I915_USERPTR_READ_ONLY | I915_USERPTR_UNSYNCHRONIZED)) return -EINVAL; /* * XXX: There is a prevalence of the assumption that we fit the * object's page count inside a 32bit _signed_ variable. Let's document * this and catch if we ever need to fix it. In the meantime, if you do * spot such a local variable, please consider fixing! * * Aside from our own locals (for which we have no excuse!): * - sg_table embeds unsigned int for num_pages * - get_user_pages*() mixed ints with longs */ if (args->user_size >> PAGE_SHIFT > INT_MAX) return -E2BIG; if (overflows_type(args->user_size, obj->base.size)) return -E2BIG; if (!args->user_size) return -EINVAL; if (offset_in_page(args->user_ptr | args->user_size)) return -EINVAL; if (!access_ok((char __user *)(unsigned long)args->user_ptr, args->user_size)) return -EFAULT; if (args->flags & I915_USERPTR_READ_ONLY) { /* * On almost all of the older hw, we cannot tell the GPU that * a page is readonly. */ if (!dev_priv->gt.vm->has_read_only) return -ENODEV; } obj = i915_gem_object_alloc(); if (obj == NULL) return -ENOMEM; drm_gem_private_object_init(dev, &obj->base, args->user_size); i915_gem_object_init(obj, &i915_gem_userptr_ops, &lock_class); obj->read_domains = I915_GEM_DOMAIN_CPU; obj->write_domain = I915_GEM_DOMAIN_CPU; i915_gem_object_set_cache_coherency(obj, I915_CACHE_LLC); obj->userptr.ptr = args->user_ptr; if (args->flags & I915_USERPTR_READ_ONLY) i915_gem_object_set_readonly(obj); /* And keep a pointer to the current->mm for resolving the user pages * at binding. This means that we need to hook into the mmu_notifier * in order to detect if the mmu is destroyed. */ ret = i915_gem_userptr_init__mm_struct(obj); if (ret == 0) ret = i915_gem_userptr_init__mmu_notifier(obj, args->flags); if (ret == 0) ret = drm_gem_handle_create(file, &obj->base, &handle); /* drop reference from allocate - handle holds it now */ i915_gem_object_put(obj); if (ret) return ret; args->handle = handle; return 0; } int i915_gem_init_userptr(struct drm_i915_private *dev_priv) { spin_lock_init(&dev_priv->mm_lock); hash_init(dev_priv->mm_structs); dev_priv->mm.userptr_wq = alloc_workqueue("i915-userptr-acquire", WQ_HIGHPRI | WQ_UNBOUND, 0); if (!dev_priv->mm.userptr_wq) return -ENOMEM; return 0; } void i915_gem_cleanup_userptr(struct drm_i915_private *dev_priv) { destroy_workqueue(dev_priv->mm.userptr_wq); }