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1/*
2 * Copyright © 2012-2014 Intel Corporation
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 *
23 */
24
25#include <drm/drmP.h>
26#include <drm/i915_drm.h>
27#include "i915_drv.h"
28#include "i915_trace.h"
29#include "intel_drv.h"
30#include <linux/mmu_context.h>
31#include <linux/mmu_notifier.h>
32#include <linux/mempolicy.h>
33#include <linux/swap.h>
34
35struct i915_mm_struct {
36 struct mm_struct *mm;
37 struct drm_device *dev;
38 struct i915_mmu_notifier *mn;
39 struct hlist_node node;
40 struct kref kref;
41 struct work_struct work;
42};
43
44#if defined(CONFIG_MMU_NOTIFIER)
45#include <linux/interval_tree.h>
46
47struct i915_mmu_notifier {
48 spinlock_t lock;
49 struct hlist_node node;
50 struct mmu_notifier mn;
51 struct rb_root objects;
52};
53
54struct i915_mmu_object {
55 struct i915_mmu_notifier *mn;
56 struct drm_i915_gem_object *obj;
57 struct interval_tree_node it;
58 struct list_head link;
59 struct work_struct work;
60 bool attached;
61};
62
63static void cancel_userptr(struct work_struct *work)
64{
65 struct i915_mmu_object *mo = container_of(work, typeof(*mo), work);
66 struct drm_i915_gem_object *obj = mo->obj;
67 struct drm_device *dev = obj->base.dev;
68
69 mutex_lock(&dev->struct_mutex);
70 /* Cancel any active worker and force us to re-evaluate gup */
71 obj->userptr.work = NULL;
72
73 if (obj->pages != NULL) {
74 struct drm_i915_private *dev_priv = to_i915(dev);
75 struct i915_vma *vma, *tmp;
76 bool was_interruptible;
77
78 was_interruptible = dev_priv->mm.interruptible;
79 dev_priv->mm.interruptible = false;
80
81 list_for_each_entry_safe(vma, tmp, &obj->vma_list, obj_link) {
82 int ret = i915_vma_unbind(vma);
83 WARN_ON(ret && ret != -EIO);
84 }
85 WARN_ON(i915_gem_object_put_pages(obj));
86
87 dev_priv->mm.interruptible = was_interruptible;
88 }
89
90 drm_gem_object_unreference(&obj->base);
91 mutex_unlock(&dev->struct_mutex);
92}
93
94static void add_object(struct i915_mmu_object *mo)
95{
96 if (mo->attached)
97 return;
98
99 interval_tree_insert(&mo->it, &mo->mn->objects);
100 mo->attached = true;
101}
102
103static void del_object(struct i915_mmu_object *mo)
104{
105 if (!mo->attached)
106 return;
107
108 interval_tree_remove(&mo->it, &mo->mn->objects);
109 mo->attached = false;
110}
111
112static void i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn,
113 struct mm_struct *mm,
114 unsigned long start,
115 unsigned long end)
116{
117 struct i915_mmu_notifier *mn =
118 container_of(_mn, struct i915_mmu_notifier, mn);
119 struct i915_mmu_object *mo;
120 struct interval_tree_node *it;
121 LIST_HEAD(cancelled);
122
123 if (RB_EMPTY_ROOT(&mn->objects))
124 return;
125
126 /* interval ranges are inclusive, but invalidate range is exclusive */
127 end--;
128
129 spin_lock(&mn->lock);
130 it = interval_tree_iter_first(&mn->objects, start, end);
131 while (it) {
132 /* The mmu_object is released late when destroying the
133 * GEM object so it is entirely possible to gain a
134 * reference on an object in the process of being freed
135 * since our serialisation is via the spinlock and not
136 * the struct_mutex - and consequently use it after it
137 * is freed and then double free it. To prevent that
138 * use-after-free we only acquire a reference on the
139 * object if it is not in the process of being destroyed.
140 */
141 mo = container_of(it, struct i915_mmu_object, it);
142 if (kref_get_unless_zero(&mo->obj->base.refcount))
143 schedule_work(&mo->work);
144
145 list_add(&mo->link, &cancelled);
146 it = interval_tree_iter_next(it, start, end);
147 }
148 list_for_each_entry(mo, &cancelled, link)
149 del_object(mo);
150 spin_unlock(&mn->lock);
151}
152
153static const struct mmu_notifier_ops i915_gem_userptr_notifier = {
154 .invalidate_range_start = i915_gem_userptr_mn_invalidate_range_start,
155};
156
157static struct i915_mmu_notifier *
158i915_mmu_notifier_create(struct mm_struct *mm)
159{
160 struct i915_mmu_notifier *mn;
161 int ret;
162
163 mn = kmalloc(sizeof(*mn), GFP_KERNEL);
164 if (mn == NULL)
165 return ERR_PTR(-ENOMEM);
166
167 spin_lock_init(&mn->lock);
168 mn->mn.ops = &i915_gem_userptr_notifier;
169 mn->objects = RB_ROOT;
170
171 /* Protected by mmap_sem (write-lock) */
172 ret = __mmu_notifier_register(&mn->mn, mm);
173 if (ret) {
174 kfree(mn);
175 return ERR_PTR(ret);
176 }
177
178 return mn;
179}
180
181static void
182i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj)
183{
184 struct i915_mmu_object *mo;
185
186 mo = obj->userptr.mmu_object;
187 if (mo == NULL)
188 return;
189
190 spin_lock(&mo->mn->lock);
191 del_object(mo);
192 spin_unlock(&mo->mn->lock);
193 kfree(mo);
194
195 obj->userptr.mmu_object = NULL;
196}
197
198static struct i915_mmu_notifier *
199i915_mmu_notifier_find(struct i915_mm_struct *mm)
200{
201 struct i915_mmu_notifier *mn = mm->mn;
202
203 mn = mm->mn;
204 if (mn)
205 return mn;
206
207 down_write(&mm->mm->mmap_sem);
208 mutex_lock(&to_i915(mm->dev)->mm_lock);
209 if ((mn = mm->mn) == NULL) {
210 mn = i915_mmu_notifier_create(mm->mm);
211 if (!IS_ERR(mn))
212 mm->mn = mn;
213 }
214 mutex_unlock(&to_i915(mm->dev)->mm_lock);
215 up_write(&mm->mm->mmap_sem);
216
217 return mn;
218}
219
220static int
221i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj,
222 unsigned flags)
223{
224 struct i915_mmu_notifier *mn;
225 struct i915_mmu_object *mo;
226
227 if (flags & I915_USERPTR_UNSYNCHRONIZED)
228 return capable(CAP_SYS_ADMIN) ? 0 : -EPERM;
229
230 if (WARN_ON(obj->userptr.mm == NULL))
231 return -EINVAL;
232
233 mn = i915_mmu_notifier_find(obj->userptr.mm);
234 if (IS_ERR(mn))
235 return PTR_ERR(mn);
236
237 mo = kzalloc(sizeof(*mo), GFP_KERNEL);
238 if (mo == NULL)
239 return -ENOMEM;
240
241 mo->mn = mn;
242 mo->obj = obj;
243 mo->it.start = obj->userptr.ptr;
244 mo->it.last = obj->userptr.ptr + obj->base.size - 1;
245 INIT_WORK(&mo->work, cancel_userptr);
246
247 obj->userptr.mmu_object = mo;
248 return 0;
249}
250
251static void
252i915_mmu_notifier_free(struct i915_mmu_notifier *mn,
253 struct mm_struct *mm)
254{
255 if (mn == NULL)
256 return;
257
258 mmu_notifier_unregister(&mn->mn, mm);
259 kfree(mn);
260}
261
262#else
263
264static void
265i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj)
266{
267}
268
269static int
270i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj,
271 unsigned flags)
272{
273 if ((flags & I915_USERPTR_UNSYNCHRONIZED) == 0)
274 return -ENODEV;
275
276 if (!capable(CAP_SYS_ADMIN))
277 return -EPERM;
278
279 return 0;
280}
281
282static void
283i915_mmu_notifier_free(struct i915_mmu_notifier *mn,
284 struct mm_struct *mm)
285{
286}
287
288#endif
289
290static struct i915_mm_struct *
291__i915_mm_struct_find(struct drm_i915_private *dev_priv, struct mm_struct *real)
292{
293 struct i915_mm_struct *mm;
294
295 /* Protected by dev_priv->mm_lock */
296 hash_for_each_possible(dev_priv->mm_structs, mm, node, (unsigned long)real)
297 if (mm->mm == real)
298 return mm;
299
300 return NULL;
301}
302
303static int
304i915_gem_userptr_init__mm_struct(struct drm_i915_gem_object *obj)
305{
306 struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
307 struct i915_mm_struct *mm;
308 int ret = 0;
309
310 /* During release of the GEM object we hold the struct_mutex. This
311 * precludes us from calling mmput() at that time as that may be
312 * the last reference and so call exit_mmap(). exit_mmap() will
313 * attempt to reap the vma, and if we were holding a GTT mmap
314 * would then call drm_gem_vm_close() and attempt to reacquire
315 * the struct mutex. So in order to avoid that recursion, we have
316 * to defer releasing the mm reference until after we drop the
317 * struct_mutex, i.e. we need to schedule a worker to do the clean
318 * up.
319 */
320 mutex_lock(&dev_priv->mm_lock);
321 mm = __i915_mm_struct_find(dev_priv, current->mm);
322 if (mm == NULL) {
323 mm = kmalloc(sizeof(*mm), GFP_KERNEL);
324 if (mm == NULL) {
325 ret = -ENOMEM;
326 goto out;
327 }
328
329 kref_init(&mm->kref);
330 mm->dev = obj->base.dev;
331
332 mm->mm = current->mm;
333 atomic_inc(¤t->mm->mm_count);
334
335 mm->mn = NULL;
336
337 /* Protected by dev_priv->mm_lock */
338 hash_add(dev_priv->mm_structs,
339 &mm->node, (unsigned long)mm->mm);
340 } else
341 kref_get(&mm->kref);
342
343 obj->userptr.mm = mm;
344out:
345 mutex_unlock(&dev_priv->mm_lock);
346 return ret;
347}
348
349static void
350__i915_mm_struct_free__worker(struct work_struct *work)
351{
352 struct i915_mm_struct *mm = container_of(work, typeof(*mm), work);
353 i915_mmu_notifier_free(mm->mn, mm->mm);
354 mmdrop(mm->mm);
355 kfree(mm);
356}
357
358static void
359__i915_mm_struct_free(struct kref *kref)
360{
361 struct i915_mm_struct *mm = container_of(kref, typeof(*mm), kref);
362
363 /* Protected by dev_priv->mm_lock */
364 hash_del(&mm->node);
365 mutex_unlock(&to_i915(mm->dev)->mm_lock);
366
367 INIT_WORK(&mm->work, __i915_mm_struct_free__worker);
368 schedule_work(&mm->work);
369}
370
371static void
372i915_gem_userptr_release__mm_struct(struct drm_i915_gem_object *obj)
373{
374 if (obj->userptr.mm == NULL)
375 return;
376
377 kref_put_mutex(&obj->userptr.mm->kref,
378 __i915_mm_struct_free,
379 &to_i915(obj->base.dev)->mm_lock);
380 obj->userptr.mm = NULL;
381}
382
383struct get_pages_work {
384 struct work_struct work;
385 struct drm_i915_gem_object *obj;
386 struct task_struct *task;
387};
388
389#if IS_ENABLED(CONFIG_SWIOTLB)
390#define swiotlb_active() swiotlb_nr_tbl()
391#else
392#define swiotlb_active() 0
393#endif
394
395static int
396st_set_pages(struct sg_table **st, struct page **pvec, int num_pages)
397{
398 struct scatterlist *sg;
399 int ret, n;
400
401 *st = kmalloc(sizeof(**st), GFP_KERNEL);
402 if (*st == NULL)
403 return -ENOMEM;
404
405 if (swiotlb_active()) {
406 ret = sg_alloc_table(*st, num_pages, GFP_KERNEL);
407 if (ret)
408 goto err;
409
410 for_each_sg((*st)->sgl, sg, num_pages, n)
411 sg_set_page(sg, pvec[n], PAGE_SIZE, 0);
412 } else {
413 ret = sg_alloc_table_from_pages(*st, pvec, num_pages,
414 0, num_pages << PAGE_SHIFT,
415 GFP_KERNEL);
416 if (ret)
417 goto err;
418 }
419
420 return 0;
421
422err:
423 kfree(*st);
424 *st = NULL;
425 return ret;
426}
427
428static int
429__i915_gem_userptr_set_pages(struct drm_i915_gem_object *obj,
430 struct page **pvec, int num_pages)
431{
432 int ret;
433
434 ret = st_set_pages(&obj->pages, pvec, num_pages);
435 if (ret)
436 return ret;
437
438 ret = i915_gem_gtt_prepare_object(obj);
439 if (ret) {
440 sg_free_table(obj->pages);
441 kfree(obj->pages);
442 obj->pages = NULL;
443 }
444
445 return ret;
446}
447
448static int
449__i915_gem_userptr_set_active(struct drm_i915_gem_object *obj,
450 bool value)
451{
452 int ret = 0;
453
454 /* During mm_invalidate_range we need to cancel any userptr that
455 * overlaps the range being invalidated. Doing so requires the
456 * struct_mutex, and that risks recursion. In order to cause
457 * recursion, the user must alias the userptr address space with
458 * a GTT mmapping (possible with a MAP_FIXED) - then when we have
459 * to invalidate that mmaping, mm_invalidate_range is called with
460 * the userptr address *and* the struct_mutex held. To prevent that
461 * we set a flag under the i915_mmu_notifier spinlock to indicate
462 * whether this object is valid.
463 */
464#if defined(CONFIG_MMU_NOTIFIER)
465 if (obj->userptr.mmu_object == NULL)
466 return 0;
467
468 spin_lock(&obj->userptr.mmu_object->mn->lock);
469 /* In order to serialise get_pages with an outstanding
470 * cancel_userptr, we must drop the struct_mutex and try again.
471 */
472 if (!value)
473 del_object(obj->userptr.mmu_object);
474 else if (!work_pending(&obj->userptr.mmu_object->work))
475 add_object(obj->userptr.mmu_object);
476 else
477 ret = -EAGAIN;
478 spin_unlock(&obj->userptr.mmu_object->mn->lock);
479#endif
480
481 return ret;
482}
483
484static void
485__i915_gem_userptr_get_pages_worker(struct work_struct *_work)
486{
487 struct get_pages_work *work = container_of(_work, typeof(*work), work);
488 struct drm_i915_gem_object *obj = work->obj;
489 struct drm_device *dev = obj->base.dev;
490 const int npages = obj->base.size >> PAGE_SHIFT;
491 struct page **pvec;
492 int pinned, ret;
493
494 ret = -ENOMEM;
495 pinned = 0;
496
497 pvec = kmalloc(npages*sizeof(struct page *),
498 GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
499 if (pvec == NULL)
500 pvec = drm_malloc_ab(npages, sizeof(struct page *));
501 if (pvec != NULL) {
502 struct mm_struct *mm = obj->userptr.mm->mm;
503
504 ret = -EFAULT;
505 if (atomic_inc_not_zero(&mm->mm_users)) {
506 down_read(&mm->mmap_sem);
507 while (pinned < npages) {
508 ret = get_user_pages_remote
509 (work->task, mm,
510 obj->userptr.ptr + pinned * PAGE_SIZE,
511 npages - pinned,
512 !obj->userptr.read_only, 0,
513 pvec + pinned, NULL);
514 if (ret < 0)
515 break;
516
517 pinned += ret;
518 }
519 up_read(&mm->mmap_sem);
520 mmput(mm);
521 }
522 }
523
524 mutex_lock(&dev->struct_mutex);
525 if (obj->userptr.work == &work->work) {
526 if (pinned == npages) {
527 ret = __i915_gem_userptr_set_pages(obj, pvec, npages);
528 if (ret == 0) {
529 list_add_tail(&obj->global_list,
530 &to_i915(dev)->mm.unbound_list);
531 obj->get_page.sg = obj->pages->sgl;
532 obj->get_page.last = 0;
533 pinned = 0;
534 }
535 }
536 obj->userptr.work = ERR_PTR(ret);
537 if (ret)
538 __i915_gem_userptr_set_active(obj, false);
539 }
540
541 obj->userptr.workers--;
542 drm_gem_object_unreference(&obj->base);
543 mutex_unlock(&dev->struct_mutex);
544
545 release_pages(pvec, pinned, 0);
546 drm_free_large(pvec);
547
548 put_task_struct(work->task);
549 kfree(work);
550}
551
552static int
553__i915_gem_userptr_get_pages_schedule(struct drm_i915_gem_object *obj,
554 bool *active)
555{
556 struct get_pages_work *work;
557
558 /* Spawn a worker so that we can acquire the
559 * user pages without holding our mutex. Access
560 * to the user pages requires mmap_sem, and we have
561 * a strict lock ordering of mmap_sem, struct_mutex -
562 * we already hold struct_mutex here and so cannot
563 * call gup without encountering a lock inversion.
564 *
565 * Userspace will keep on repeating the operation
566 * (thanks to EAGAIN) until either we hit the fast
567 * path or the worker completes. If the worker is
568 * cancelled or superseded, the task is still run
569 * but the results ignored. (This leads to
570 * complications that we may have a stray object
571 * refcount that we need to be wary of when
572 * checking for existing objects during creation.)
573 * If the worker encounters an error, it reports
574 * that error back to this function through
575 * obj->userptr.work = ERR_PTR.
576 */
577 if (obj->userptr.workers >= I915_GEM_USERPTR_MAX_WORKERS)
578 return -EAGAIN;
579
580 work = kmalloc(sizeof(*work), GFP_KERNEL);
581 if (work == NULL)
582 return -ENOMEM;
583
584 obj->userptr.work = &work->work;
585 obj->userptr.workers++;
586
587 work->obj = obj;
588 drm_gem_object_reference(&obj->base);
589
590 work->task = current;
591 get_task_struct(work->task);
592
593 INIT_WORK(&work->work, __i915_gem_userptr_get_pages_worker);
594 schedule_work(&work->work);
595
596 *active = true;
597 return -EAGAIN;
598}
599
600static int
601i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
602{
603 const int num_pages = obj->base.size >> PAGE_SHIFT;
604 struct page **pvec;
605 int pinned, ret;
606 bool active;
607
608 /* If userspace should engineer that these pages are replaced in
609 * the vma between us binding this page into the GTT and completion
610 * of rendering... Their loss. If they change the mapping of their
611 * pages they need to create a new bo to point to the new vma.
612 *
613 * However, that still leaves open the possibility of the vma
614 * being copied upon fork. Which falls under the same userspace
615 * synchronisation issue as a regular bo, except that this time
616 * the process may not be expecting that a particular piece of
617 * memory is tied to the GPU.
618 *
619 * Fortunately, we can hook into the mmu_notifier in order to
620 * discard the page references prior to anything nasty happening
621 * to the vma (discard or cloning) which should prevent the more
622 * egregious cases from causing harm.
623 */
624 if (IS_ERR(obj->userptr.work)) {
625 /* active flag will have been dropped already by the worker */
626 ret = PTR_ERR(obj->userptr.work);
627 obj->userptr.work = NULL;
628 return ret;
629 }
630 if (obj->userptr.work)
631 /* active flag should still be held for the pending work */
632 return -EAGAIN;
633
634 /* Let the mmu-notifier know that we have begun and need cancellation */
635 ret = __i915_gem_userptr_set_active(obj, true);
636 if (ret)
637 return ret;
638
639 pvec = NULL;
640 pinned = 0;
641 if (obj->userptr.mm->mm == current->mm) {
642 pvec = kmalloc(num_pages*sizeof(struct page *),
643 GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
644 if (pvec == NULL) {
645 pvec = drm_malloc_ab(num_pages, sizeof(struct page *));
646 if (pvec == NULL) {
647 __i915_gem_userptr_set_active(obj, false);
648 return -ENOMEM;
649 }
650 }
651
652 pinned = __get_user_pages_fast(obj->userptr.ptr, num_pages,
653 !obj->userptr.read_only, pvec);
654 }
655
656 active = false;
657 if (pinned < 0)
658 ret = pinned, pinned = 0;
659 else if (pinned < num_pages)
660 ret = __i915_gem_userptr_get_pages_schedule(obj, &active);
661 else
662 ret = __i915_gem_userptr_set_pages(obj, pvec, num_pages);
663 if (ret) {
664 __i915_gem_userptr_set_active(obj, active);
665 release_pages(pvec, pinned, 0);
666 }
667 drm_free_large(pvec);
668 return ret;
669}
670
671static void
672i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj)
673{
674 struct sg_page_iter sg_iter;
675
676 BUG_ON(obj->userptr.work != NULL);
677 __i915_gem_userptr_set_active(obj, false);
678
679 if (obj->madv != I915_MADV_WILLNEED)
680 obj->dirty = 0;
681
682 i915_gem_gtt_finish_object(obj);
683
684 for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0) {
685 struct page *page = sg_page_iter_page(&sg_iter);
686
687 if (obj->dirty)
688 set_page_dirty(page);
689
690 mark_page_accessed(page);
691 put_page(page);
692 }
693 obj->dirty = 0;
694
695 sg_free_table(obj->pages);
696 kfree(obj->pages);
697}
698
699static void
700i915_gem_userptr_release(struct drm_i915_gem_object *obj)
701{
702 i915_gem_userptr_release__mmu_notifier(obj);
703 i915_gem_userptr_release__mm_struct(obj);
704}
705
706static int
707i915_gem_userptr_dmabuf_export(struct drm_i915_gem_object *obj)
708{
709 if (obj->userptr.mmu_object)
710 return 0;
711
712 return i915_gem_userptr_init__mmu_notifier(obj, 0);
713}
714
715static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = {
716 .flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE,
717 .get_pages = i915_gem_userptr_get_pages,
718 .put_pages = i915_gem_userptr_put_pages,
719 .dmabuf_export = i915_gem_userptr_dmabuf_export,
720 .release = i915_gem_userptr_release,
721};
722
723/**
724 * Creates a new mm object that wraps some normal memory from the process
725 * context - user memory.
726 *
727 * We impose several restrictions upon the memory being mapped
728 * into the GPU.
729 * 1. It must be page aligned (both start/end addresses, i.e ptr and size).
730 * 2. It must be normal system memory, not a pointer into another map of IO
731 * space (e.g. it must not be a GTT mmapping of another object).
732 * 3. We only allow a bo as large as we could in theory map into the GTT,
733 * that is we limit the size to the total size of the GTT.
734 * 4. The bo is marked as being snoopable. The backing pages are left
735 * accessible directly by the CPU, but reads and writes by the GPU may
736 * incur the cost of a snoop (unless you have an LLC architecture).
737 *
738 * Synchronisation between multiple users and the GPU is left to userspace
739 * through the normal set-domain-ioctl. The kernel will enforce that the
740 * GPU relinquishes the VMA before it is returned back to the system
741 * i.e. upon free(), munmap() or process termination. However, the userspace
742 * malloc() library may not immediately relinquish the VMA after free() and
743 * instead reuse it whilst the GPU is still reading and writing to the VMA.
744 * Caveat emptor.
745 *
746 * Also note, that the object created here is not currently a "first class"
747 * object, in that several ioctls are banned. These are the CPU access
748 * ioctls: mmap(), pwrite and pread. In practice, you are expected to use
749 * direct access via your pointer rather than use those ioctls. Another
750 * restriction is that we do not allow userptr surfaces to be pinned to the
751 * hardware and so we reject any attempt to create a framebuffer out of a
752 * userptr.
753 *
754 * If you think this is a good interface to use to pass GPU memory between
755 * drivers, please use dma-buf instead. In fact, wherever possible use
756 * dma-buf instead.
757 */
758int
759i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
760{
761 struct drm_i915_gem_userptr *args = data;
762 struct drm_i915_gem_object *obj;
763 int ret;
764 u32 handle;
765
766 if (args->flags & ~(I915_USERPTR_READ_ONLY |
767 I915_USERPTR_UNSYNCHRONIZED))
768 return -EINVAL;
769
770 if (offset_in_page(args->user_ptr | args->user_size))
771 return -EINVAL;
772
773 if (!access_ok(args->flags & I915_USERPTR_READ_ONLY ? VERIFY_READ : VERIFY_WRITE,
774 (char __user *)(unsigned long)args->user_ptr, args->user_size))
775 return -EFAULT;
776
777 if (args->flags & I915_USERPTR_READ_ONLY) {
778 /* On almost all of the current hw, we cannot tell the GPU that a
779 * page is readonly, so this is just a placeholder in the uAPI.
780 */
781 return -ENODEV;
782 }
783
784 obj = i915_gem_object_alloc(dev);
785 if (obj == NULL)
786 return -ENOMEM;
787
788 drm_gem_private_object_init(dev, &obj->base, args->user_size);
789 i915_gem_object_init(obj, &i915_gem_userptr_ops);
790 obj->cache_level = I915_CACHE_LLC;
791 obj->base.write_domain = I915_GEM_DOMAIN_CPU;
792 obj->base.read_domains = I915_GEM_DOMAIN_CPU;
793
794 obj->userptr.ptr = args->user_ptr;
795 obj->userptr.read_only = !!(args->flags & I915_USERPTR_READ_ONLY);
796
797 /* And keep a pointer to the current->mm for resolving the user pages
798 * at binding. This means that we need to hook into the mmu_notifier
799 * in order to detect if the mmu is destroyed.
800 */
801 ret = i915_gem_userptr_init__mm_struct(obj);
802 if (ret == 0)
803 ret = i915_gem_userptr_init__mmu_notifier(obj, args->flags);
804 if (ret == 0)
805 ret = drm_gem_handle_create(file, &obj->base, &handle);
806
807 /* drop reference from allocate - handle holds it now */
808 drm_gem_object_unreference_unlocked(&obj->base);
809 if (ret)
810 return ret;
811
812 args->handle = handle;
813 return 0;
814}
815
816int
817i915_gem_init_userptr(struct drm_device *dev)
818{
819 struct drm_i915_private *dev_priv = to_i915(dev);
820 mutex_init(&dev_priv->mm_lock);
821 hash_init(dev_priv->mm_structs);
822 return 0;
823}