1 /*
2  * Copyright © 2008-2010 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  * Authors:
24  *    Eric Anholt <eric@anholt.net>
25  *    Chris Wilson <chris@chris-wilson.co.uuk>
26  *
27  */
28 
29 #include "gem/i915_gem_context.h"
30 #include "gt/intel_gt_requests.h"
31 
32 #include "i915_drv.h"
33 #include "i915_trace.h"
34 
35 I915_SELFTEST_DECLARE(static struct igt_evict_ctl {
36 	bool fail_if_busy:1;
37 } igt_evict_ctl;)
38 
39 static int ggtt_flush(struct intel_gt *gt)
40 {
41 	/*
42 	 * Not everything in the GGTT is tracked via vma (otherwise we
43 	 * could evict as required with minimal stalling) so we are forced
44 	 * to idle the GPU and explicitly retire outstanding requests in
45 	 * the hopes that we can then remove contexts and the like only
46 	 * bound by their active reference.
47 	 */
48 	return intel_gt_wait_for_idle(gt, MAX_SCHEDULE_TIMEOUT);
49 }
50 
51 static bool
52 mark_free(struct drm_mm_scan *scan,
53 	  struct i915_vma *vma,
54 	  unsigned int flags,
55 	  struct list_head *unwind)
56 {
57 	if (i915_vma_is_pinned(vma))
58 		return false;
59 
60 	list_add(&vma->evict_link, unwind);
61 	return drm_mm_scan_add_block(scan, &vma->node);
62 }
63 
64 /**
65  * i915_gem_evict_something - Evict vmas to make room for binding a new one
66  * @vm: address space to evict from
67  * @min_size: size of the desired free space
68  * @alignment: alignment constraint of the desired free space
69  * @color: color for the desired space
70  * @start: start (inclusive) of the range from which to evict objects
71  * @end: end (exclusive) of the range from which to evict objects
72  * @flags: additional flags to control the eviction algorithm
73  *
74  * This function will try to evict vmas until a free space satisfying the
75  * requirements is found. Callers must check first whether any such hole exists
76  * already before calling this function.
77  *
78  * This function is used by the object/vma binding code.
79  *
80  * Since this function is only used to free up virtual address space it only
81  * ignores pinned vmas, and not object where the backing storage itself is
82  * pinned. Hence obj->pages_pin_count does not protect against eviction.
83  *
84  * To clarify: This is for freeing up virtual address space, not for freeing
85  * memory in e.g. the shrinker.
86  */
87 int
88 i915_gem_evict_something(struct i915_address_space *vm,
89 			 u64 min_size, u64 alignment,
90 			 unsigned long color,
91 			 u64 start, u64 end,
92 			 unsigned flags)
93 {
94 	struct drm_mm_scan scan;
95 	struct list_head eviction_list;
96 	struct i915_vma *vma, *next;
97 	struct drm_mm_node *node;
98 	enum drm_mm_insert_mode mode;
99 	struct i915_vma *active;
100 	int ret;
101 
102 	lockdep_assert_held(&vm->mutex);
103 	trace_i915_gem_evict(vm, min_size, alignment, flags);
104 
105 	/*
106 	 * The goal is to evict objects and amalgamate space in rough LRU order.
107 	 * Since both active and inactive objects reside on the same list,
108 	 * in a mix of creation and last scanned order, as we process the list
109 	 * we sort it into inactive/active, which keeps the active portion
110 	 * in a rough MRU order.
111 	 *
112 	 * The retirement sequence is thus:
113 	 *   1. Inactive objects (already retired, random order)
114 	 *   2. Active objects (will stall on unbinding, oldest scanned first)
115 	 */
116 	mode = DRM_MM_INSERT_BEST;
117 	if (flags & PIN_HIGH)
118 		mode = DRM_MM_INSERT_HIGH;
119 	if (flags & PIN_MAPPABLE)
120 		mode = DRM_MM_INSERT_LOW;
121 	drm_mm_scan_init_with_range(&scan, &vm->mm,
122 				    min_size, alignment, color,
123 				    start, end, mode);
124 
125 	intel_gt_retire_requests(vm->gt);
126 
127 search_again:
128 	active = NULL;
129 	INIT_LIST_HEAD(&eviction_list);
130 	list_for_each_entry_safe(vma, next, &vm->bound_list, vm_link) {
131 		if (vma == active) { /* now seen this vma twice */
132 			if (flags & PIN_NONBLOCK)
133 				break;
134 
135 			active = ERR_PTR(-EAGAIN);
136 		}
137 
138 		/*
139 		 * We keep this list in a rough least-recently scanned order
140 		 * of active elements (inactive elements are cheap to reap).
141 		 * New entries are added to the end, and we move anything we
142 		 * scan to the end. The assumption is that the working set
143 		 * of applications is either steady state (and thanks to the
144 		 * userspace bo cache it almost always is) or volatile and
145 		 * frequently replaced after a frame, which are self-evicting!
146 		 * Given that assumption, the MRU order of the scan list is
147 		 * fairly static, and keeping it in least-recently scan order
148 		 * is suitable.
149 		 *
150 		 * To notice when we complete one full cycle, we record the
151 		 * first active element seen, before moving it to the tail.
152 		 */
153 		if (active != ERR_PTR(-EAGAIN) && i915_vma_is_active(vma)) {
154 			if (!active)
155 				active = vma;
156 
157 			list_move_tail(&vma->vm_link, &vm->bound_list);
158 			continue;
159 		}
160 
161 		if (mark_free(&scan, vma, flags, &eviction_list))
162 			goto found;
163 	}
164 
165 	/* Nothing found, clean up and bail out! */
166 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
167 		ret = drm_mm_scan_remove_block(&scan, &vma->node);
168 		BUG_ON(ret);
169 	}
170 
171 	/*
172 	 * Can we unpin some objects such as idle hw contents,
173 	 * or pending flips? But since only the GGTT has global entries
174 	 * such as scanouts, rinbuffers and contexts, we can skip the
175 	 * purge when inspecting per-process local address spaces.
176 	 */
177 	if (!i915_is_ggtt(vm) || flags & PIN_NONBLOCK)
178 		return -ENOSPC;
179 
180 	/*
181 	 * Not everything in the GGTT is tracked via VMA using
182 	 * i915_vma_move_to_active(), otherwise we could evict as required
183 	 * with minimal stalling. Instead we are forced to idle the GPU and
184 	 * explicitly retire outstanding requests which will then remove
185 	 * the pinning for active objects such as contexts and ring,
186 	 * enabling us to evict them on the next iteration.
187 	 *
188 	 * To ensure that all user contexts are evictable, we perform
189 	 * a switch to the perma-pinned kernel context. This all also gives
190 	 * us a termination condition, when the last retired context is
191 	 * the kernel's there is no more we can evict.
192 	 */
193 	if (I915_SELFTEST_ONLY(igt_evict_ctl.fail_if_busy))
194 		return -EBUSY;
195 
196 	ret = ggtt_flush(vm->gt);
197 	if (ret)
198 		return ret;
199 
200 	cond_resched();
201 
202 	flags |= PIN_NONBLOCK;
203 	goto search_again;
204 
205 found:
206 	/* drm_mm doesn't allow any other other operations while
207 	 * scanning, therefore store to-be-evicted objects on a
208 	 * temporary list and take a reference for all before
209 	 * calling unbind (which may remove the active reference
210 	 * of any of our objects, thus corrupting the list).
211 	 */
212 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
213 		if (drm_mm_scan_remove_block(&scan, &vma->node))
214 			__i915_vma_pin(vma);
215 		else
216 			list_del(&vma->evict_link);
217 	}
218 
219 	/* Unbinding will emit any required flushes */
220 	ret = 0;
221 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
222 		__i915_vma_unpin(vma);
223 		if (ret == 0)
224 			ret = __i915_vma_unbind(vma);
225 	}
226 
227 	while (ret == 0 && (node = drm_mm_scan_color_evict(&scan))) {
228 		vma = container_of(node, struct i915_vma, node);
229 
230 		/* If we find any non-objects (!vma), we cannot evict them */
231 		if (vma->node.color != I915_COLOR_UNEVICTABLE)
232 			ret = __i915_vma_unbind(vma);
233 		else
234 			ret = -ENOSPC; /* XXX search failed, try again? */
235 	}
236 
237 	return ret;
238 }
239 
240 /**
241  * i915_gem_evict_for_node - Evict vmas to make room for binding a new one
242  * @vm: address space to evict from
243  * @target: range (and color) to evict for
244  * @flags: additional flags to control the eviction algorithm
245  *
246  * This function will try to evict vmas that overlap the target node.
247  *
248  * To clarify: This is for freeing up virtual address space, not for freeing
249  * memory in e.g. the shrinker.
250  */
251 int i915_gem_evict_for_node(struct i915_address_space *vm,
252 			    struct drm_mm_node *target,
253 			    unsigned int flags)
254 {
255 	LIST_HEAD(eviction_list);
256 	struct drm_mm_node *node;
257 	u64 start = target->start;
258 	u64 end = start + target->size;
259 	struct i915_vma *vma, *next;
260 	int ret = 0;
261 
262 	lockdep_assert_held(&vm->mutex);
263 	GEM_BUG_ON(!IS_ALIGNED(start, I915_GTT_PAGE_SIZE));
264 	GEM_BUG_ON(!IS_ALIGNED(end, I915_GTT_PAGE_SIZE));
265 
266 	trace_i915_gem_evict_node(vm, target, flags);
267 
268 	/*
269 	 * Retire before we search the active list. Although we have
270 	 * reasonable accuracy in our retirement lists, we may have
271 	 * a stray pin (preventing eviction) that can only be resolved by
272 	 * retiring.
273 	 */
274 	intel_gt_retire_requests(vm->gt);
275 
276 	if (i915_vm_has_cache_coloring(vm)) {
277 		/* Expand search to cover neighbouring guard pages (or lack!) */
278 		if (start)
279 			start -= I915_GTT_PAGE_SIZE;
280 
281 		/* Always look at the page afterwards to avoid the end-of-GTT */
282 		end += I915_GTT_PAGE_SIZE;
283 	}
284 	GEM_BUG_ON(start >= end);
285 
286 	drm_mm_for_each_node_in_range(node, &vm->mm, start, end) {
287 		/* If we find any non-objects (!vma), we cannot evict them */
288 		if (node->color == I915_COLOR_UNEVICTABLE) {
289 			ret = -ENOSPC;
290 			break;
291 		}
292 
293 		GEM_BUG_ON(!drm_mm_node_allocated(node));
294 		vma = container_of(node, typeof(*vma), node);
295 
296 		/*
297 		 * If we are using coloring to insert guard pages between
298 		 * different cache domains within the address space, we have
299 		 * to check whether the objects on either side of our range
300 		 * abutt and conflict. If they are in conflict, then we evict
301 		 * those as well to make room for our guard pages.
302 		 */
303 		if (i915_vm_has_cache_coloring(vm)) {
304 			if (node->start + node->size == target->start) {
305 				if (node->color == target->color)
306 					continue;
307 			}
308 			if (node->start == target->start + target->size) {
309 				if (node->color == target->color)
310 					continue;
311 			}
312 		}
313 
314 		if (i915_vma_is_pinned(vma)) {
315 			ret = -ENOSPC;
316 			break;
317 		}
318 
319 		if (flags & PIN_NONBLOCK && i915_vma_is_active(vma)) {
320 			ret = -ENOSPC;
321 			break;
322 		}
323 
324 		/*
325 		 * Never show fear in the face of dragons!
326 		 *
327 		 * We cannot directly remove this node from within this
328 		 * iterator and as with i915_gem_evict_something() we employ
329 		 * the vma pin_count in order to prevent the action of
330 		 * unbinding one vma from freeing (by dropping its active
331 		 * reference) another in our eviction list.
332 		 */
333 		__i915_vma_pin(vma);
334 		list_add(&vma->evict_link, &eviction_list);
335 	}
336 
337 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
338 		__i915_vma_unpin(vma);
339 		if (ret == 0)
340 			ret = __i915_vma_unbind(vma);
341 	}
342 
343 	return ret;
344 }
345 
346 /**
347  * i915_gem_evict_vm - Evict all idle vmas from a vm
348  * @vm: Address space to cleanse
349  *
350  * This function evicts all vmas from a vm.
351  *
352  * This is used by the execbuf code as a last-ditch effort to defragment the
353  * address space.
354  *
355  * To clarify: This is for freeing up virtual address space, not for freeing
356  * memory in e.g. the shrinker.
357  */
358 int i915_gem_evict_vm(struct i915_address_space *vm)
359 {
360 	int ret = 0;
361 
362 	lockdep_assert_held(&vm->mutex);
363 	trace_i915_gem_evict_vm(vm);
364 
365 	/* Switch back to the default context in order to unpin
366 	 * the existing context objects. However, such objects only
367 	 * pin themselves inside the global GTT and performing the
368 	 * switch otherwise is ineffective.
369 	 */
370 	if (i915_is_ggtt(vm)) {
371 		ret = ggtt_flush(vm->gt);
372 		if (ret)
373 			return ret;
374 	}
375 
376 	do {
377 		struct i915_vma *vma, *vn;
378 		LIST_HEAD(eviction_list);
379 
380 		list_for_each_entry(vma, &vm->bound_list, vm_link) {
381 			if (i915_vma_is_pinned(vma))
382 				continue;
383 
384 			__i915_vma_pin(vma);
385 			list_add(&vma->evict_link, &eviction_list);
386 		}
387 		if (list_empty(&eviction_list))
388 			break;
389 
390 		ret = 0;
391 		list_for_each_entry_safe(vma, vn, &eviction_list, evict_link) {
392 			__i915_vma_unpin(vma);
393 			if (ret == 0)
394 				ret = __i915_vma_unbind(vma);
395 			if (ret != -EINTR) /* "Get me out of here!" */
396 				ret = 0;
397 		}
398 	} while (ret == 0);
399 
400 	return ret;
401 }
402 
403 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
404 #include "selftests/i915_gem_evict.c"
405 #endif
406