xref: /openbsd-src/sys/dev/pci/drm/i915/gt/intel_gtt.c (revision 1a8dbaac879b9f3335ad7fb25429ce63ac1d6bac)
1 // SPDX-License-Identifier: MIT
2 /*
3  * Copyright © 2020 Intel Corporation
4  */
5 
6 #include <linux/slab.h> /* fault-inject.h is not standalone! */
7 
8 #include <linux/fault-inject.h>
9 #include <asm/set_memory.h>
10 
11 #include "i915_trace.h"
12 #include "intel_gt.h"
13 #include "intel_gtt.h"
14 
15 void stash_init(struct pagestash *stash)
16 {
17 	pagevec_init(&stash->pvec);
18 	mtx_init(&stash->lock, IPL_NONE);
19 }
20 
21 static struct vm_page *stash_pop_page(struct pagestash *stash)
22 {
23 	struct vm_page *page = NULL;
24 
25 	spin_lock(&stash->lock);
26 	if (likely(stash->pvec.nr))
27 		page = stash->pvec.pages[--stash->pvec.nr];
28 	spin_unlock(&stash->lock);
29 
30 	return page;
31 }
32 
33 static void stash_push_pagevec(struct pagestash *stash, struct pagevec *pvec)
34 {
35 	unsigned int nr;
36 
37 	spin_lock_nested(&stash->lock, SINGLE_DEPTH_NESTING);
38 
39 	nr = min_t(typeof(nr), pvec->nr, pagevec_space(&stash->pvec));
40 	memcpy(stash->pvec.pages + stash->pvec.nr,
41 	       pvec->pages + pvec->nr - nr,
42 	       sizeof(pvec->pages[0]) * nr);
43 	stash->pvec.nr += nr;
44 
45 	spin_unlock(&stash->lock);
46 
47 	pvec->nr -= nr;
48 }
49 
50 static struct vm_page *vm_alloc_page(struct i915_address_space *vm, gfp_t gfp)
51 {
52 	struct pagevec stack;
53 	struct vm_page *page;
54 
55 	if (I915_SELFTEST_ONLY(should_fail(&vm->fault_attr, 1)))
56 		i915_gem_shrink_all(vm->i915);
57 
58 	page = stash_pop_page(&vm->free_pages);
59 	if (page)
60 		return page;
61 
62 	if (!vm->pt_kmap_wc)
63 		return alloc_page(gfp);
64 
65 	/* Look in our global stash of WC pages... */
66 	page = stash_pop_page(&vm->i915->mm.wc_stash);
67 	if (page)
68 		return page;
69 
70 	/*
71 	 * Otherwise batch allocate pages to amortize cost of set_pages_wc.
72 	 *
73 	 * We have to be careful as page allocation may trigger the shrinker
74 	 * (via direct reclaim) which will fill up the WC stash underneath us.
75 	 * So we add our WB pages into a temporary pvec on the stack and merge
76 	 * them into the WC stash after all the allocations are complete.
77 	 */
78 	pagevec_init(&stack);
79 	do {
80 		struct vm_page *page;
81 
82 		page = alloc_page(gfp);
83 		if (unlikely(!page))
84 			break;
85 
86 		stack.pages[stack.nr++] = page;
87 	} while (pagevec_space(&stack));
88 
89 	if (stack.nr && !set_pages_array_wc(stack.pages, stack.nr)) {
90 		page = stack.pages[--stack.nr];
91 
92 		/* Merge spare WC pages to the global stash */
93 		if (stack.nr)
94 			stash_push_pagevec(&vm->i915->mm.wc_stash, &stack);
95 
96 		/* Push any surplus WC pages onto the local VM stash */
97 		if (stack.nr)
98 			stash_push_pagevec(&vm->free_pages, &stack);
99 	}
100 
101 	/* Return unwanted leftovers */
102 	if (unlikely(stack.nr)) {
103 		WARN_ON_ONCE(set_pages_array_wb(stack.pages, stack.nr));
104 		__pagevec_release(&stack);
105 	}
106 
107 	return page;
108 }
109 
110 static void vm_free_pages_release(struct i915_address_space *vm,
111 				  bool immediate)
112 {
113 	struct pagevec *pvec = &vm->free_pages.pvec;
114 	struct pagevec stack;
115 
116 	lockdep_assert_held(&vm->free_pages.lock);
117 	GEM_BUG_ON(!pagevec_count(pvec));
118 
119 	if (vm->pt_kmap_wc) {
120 		/*
121 		 * When we use WC, first fill up the global stash and then
122 		 * only if full immediately free the overflow.
123 		 */
124 		stash_push_pagevec(&vm->i915->mm.wc_stash, pvec);
125 
126 		/*
127 		 * As we have made some room in the VM's free_pages,
128 		 * we can wait for it to fill again. Unless we are
129 		 * inside i915_address_space_fini() and must
130 		 * immediately release the pages!
131 		 */
132 		if (pvec->nr <= (immediate ? 0 : PAGEVEC_SIZE - 1))
133 			return;
134 
135 		/*
136 		 * We have to drop the lock to allow ourselves to sleep,
137 		 * so take a copy of the pvec and clear the stash for
138 		 * others to use it as we sleep.
139 		 */
140 		stack = *pvec;
141 		pagevec_reinit(pvec);
142 		spin_unlock(&vm->free_pages.lock);
143 
144 		pvec = &stack;
145 		set_pages_array_wb(pvec->pages, pvec->nr);
146 
147 		spin_lock(&vm->free_pages.lock);
148 	}
149 
150 	__pagevec_release(pvec);
151 }
152 
153 static void vm_free_page(struct i915_address_space *vm, struct vm_page *page)
154 {
155 	/*
156 	 * On !llc, we need to change the pages back to WB. We only do so
157 	 * in bulk, so we rarely need to change the page attributes here,
158 	 * but doing so requires a stop_machine() from deep inside arch/x86/mm.
159 	 * To make detection of the possible sleep more likely, use an
160 	 * unconditional might_sleep() for everybody.
161 	 */
162 	might_sleep();
163 	spin_lock(&vm->free_pages.lock);
164 	while (!pagevec_space(&vm->free_pages.pvec))
165 		vm_free_pages_release(vm, false);
166 	GEM_BUG_ON(pagevec_count(&vm->free_pages.pvec) >= PAGEVEC_SIZE);
167 	pagevec_add(&vm->free_pages.pvec, page);
168 	spin_unlock(&vm->free_pages.lock);
169 }
170 
171 void __i915_vm_close(struct i915_address_space *vm)
172 {
173 	struct i915_vma *vma, *vn;
174 
175 	if (!atomic_dec_and_mutex_lock(&vm->open, &vm->mutex))
176 		return;
177 
178 	list_for_each_entry_safe(vma, vn, &vm->bound_list, vm_link) {
179 		struct drm_i915_gem_object *obj = vma->obj;
180 
181 		/* Keep the obj (and hence the vma) alive as _we_ destroy it */
182 		if (!kref_get_unless_zero(&obj->base.refcount))
183 			continue;
184 
185 		atomic_and(~I915_VMA_PIN_MASK, &vma->flags);
186 		WARN_ON(__i915_vma_unbind(vma));
187 		__i915_vma_put(vma);
188 
189 		i915_gem_object_put(obj);
190 	}
191 	GEM_BUG_ON(!list_empty(&vm->bound_list));
192 
193 	mutex_unlock(&vm->mutex);
194 }
195 
196 void i915_address_space_fini(struct i915_address_space *vm)
197 {
198 	spin_lock(&vm->free_pages.lock);
199 	if (pagevec_count(&vm->free_pages.pvec))
200 		vm_free_pages_release(vm, true);
201 	GEM_BUG_ON(pagevec_count(&vm->free_pages.pvec));
202 	spin_unlock(&vm->free_pages.lock);
203 
204 	drm_mm_takedown(&vm->mm);
205 
206 	mutex_destroy(&vm->mutex);
207 }
208 
209 static void __i915_vm_release(struct work_struct *work)
210 {
211 	struct i915_address_space *vm =
212 		container_of(work, struct i915_address_space, rcu.work);
213 
214 	vm->cleanup(vm);
215 	i915_address_space_fini(vm);
216 
217 	kfree(vm);
218 }
219 
220 void i915_vm_release(struct kref *kref)
221 {
222 	struct i915_address_space *vm =
223 		container_of(kref, struct i915_address_space, ref);
224 
225 	GEM_BUG_ON(i915_is_ggtt(vm));
226 	trace_i915_ppgtt_release(vm);
227 
228 	queue_rcu_work(vm->i915->wq, &vm->rcu);
229 }
230 
231 void i915_address_space_init(struct i915_address_space *vm, int subclass)
232 {
233 	kref_init(&vm->ref);
234 	INIT_RCU_WORK(&vm->rcu, __i915_vm_release);
235 	atomic_set(&vm->open, 1);
236 
237 	/*
238 	 * The vm->mutex must be reclaim safe (for use in the shrinker).
239 	 * Do a dummy acquire now under fs_reclaim so that any allocation
240 	 * attempt holding the lock is immediately reported by lockdep.
241 	 */
242 	rw_init(&vm->mutex, "vmlk");
243 	lockdep_set_subclass(&vm->mutex, subclass);
244 	i915_gem_shrinker_taints_mutex(vm->i915, &vm->mutex);
245 
246 	GEM_BUG_ON(!vm->total);
247 	drm_mm_init(&vm->mm, 0, vm->total);
248 	vm->mm.head_node.color = I915_COLOR_UNEVICTABLE;
249 
250 	stash_init(&vm->free_pages);
251 
252 	INIT_LIST_HEAD(&vm->bound_list);
253 }
254 
255 void clear_pages(struct i915_vma *vma)
256 {
257 	GEM_BUG_ON(!vma->pages);
258 
259 	if (vma->pages != vma->obj->mm.pages) {
260 		sg_free_table(vma->pages);
261 		kfree(vma->pages);
262 	}
263 	vma->pages = NULL;
264 
265 	memset(&vma->page_sizes, 0, sizeof(vma->page_sizes));
266 }
267 
268 #ifdef __linux__
269 static int __setup_page_dma(struct i915_address_space *vm,
270 			    struct i915_page_dma *p,
271 			    gfp_t gfp)
272 {
273 	p->page = vm_alloc_page(vm, gfp | I915_GFP_ALLOW_FAIL);
274 	if (unlikely(!p->page))
275 		return -ENOMEM;
276 
277 	p->daddr = dma_map_page_attrs(vm->dma,
278 				      p->page, 0, PAGE_SIZE,
279 				      PCI_DMA_BIDIRECTIONAL,
280 				      DMA_ATTR_SKIP_CPU_SYNC |
281 				      DMA_ATTR_NO_WARN);
282 	if (unlikely(dma_mapping_error(vm->dma, p->daddr))) {
283 		vm_free_page(vm, p->page);
284 		return -ENOMEM;
285 	}
286 
287 	return 0;
288 }
289 #else
290 static int __setup_page_dma(struct i915_address_space *vm,
291 			    struct i915_page_dma *p,
292 			    gfp_t gfp)
293 {
294 	p->page = vm_alloc_page(vm, gfp | I915_GFP_ALLOW_FAIL);
295 	if (unlikely(!p->page))
296 		return -ENOMEM;
297 
298 	p->daddr = VM_PAGE_TO_PHYS(p->page);
299 
300 	return 0;
301 }
302 #endif
303 
304 int setup_page_dma(struct i915_address_space *vm, struct i915_page_dma *p)
305 {
306 	return __setup_page_dma(vm, p, __GFP_HIGHMEM);
307 }
308 
309 void cleanup_page_dma(struct i915_address_space *vm, struct i915_page_dma *p)
310 {
311 #ifdef __linux__
312 	dma_unmap_page(vm->dma, p->daddr, PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
313 #endif
314 	vm_free_page(vm, p->page);
315 }
316 
317 void
318 fill_page_dma(const struct i915_page_dma *p, const u64 val, unsigned int count)
319 {
320 	kunmap_atomic(memset64(kmap_atomic(p->page), val, count));
321 }
322 
323 static void poison_scratch_page(struct vm_page *page, unsigned long size)
324 {
325 	if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
326 		return;
327 
328 	GEM_BUG_ON(!IS_ALIGNED(size, PAGE_SIZE));
329 
330 	do {
331 		void *vaddr;
332 
333 		vaddr = kmap(page);
334 #ifdef __linux__
335 		memset(vaddr, POISON_FREE, PAGE_SIZE);
336 		kunmap(page);
337 #else
338 		poison_mem(vaddr, PAGE_SIZE);
339 		kunmap_va(vaddr);
340 #endif
341 
342 		page = pfn_to_page(page_to_pfn(page) + 1);
343 		size -= PAGE_SIZE;
344 	} while (size);
345 }
346 
347 int setup_scratch_page(struct i915_address_space *vm, gfp_t gfp)
348 {
349 	unsigned long size;
350 
351 	/*
352 	 * In order to utilize 64K pages for an object with a size < 2M, we will
353 	 * need to support a 64K scratch page, given that every 16th entry for a
354 	 * page-table operating in 64K mode must point to a properly aligned 64K
355 	 * region, including any PTEs which happen to point to scratch.
356 	 *
357 	 * This is only relevant for the 48b PPGTT where we support
358 	 * huge-gtt-pages, see also i915_vma_insert(). However, as we share the
359 	 * scratch (read-only) between all vm, we create one 64k scratch page
360 	 * for all.
361 	 */
362 	size = I915_GTT_PAGE_SIZE_4K;
363 	if (i915_vm_is_4lvl(vm) &&
364 	    HAS_PAGE_SIZES(vm->i915, I915_GTT_PAGE_SIZE_64K)) {
365 		size = I915_GTT_PAGE_SIZE_64K;
366 		gfp |= __GFP_NOWARN;
367 	}
368 	gfp |= __GFP_ZERO | __GFP_RETRY_MAYFAIL;
369 
370 	do {
371 		unsigned int order = get_order(size);
372 		struct vm_page *page;
373 		dma_addr_t addr;
374 
375 		page = alloc_pages(gfp, order);
376 		if (unlikely(!page))
377 			goto skip;
378 
379 		/*
380 		 * Use a non-zero scratch page for debugging.
381 		 *
382 		 * We want a value that should be reasonably obvious
383 		 * to spot in the error state, while also causing a GPU hang
384 		 * if executed. We prefer using a clear page in production, so
385 		 * should it ever be accidentally used, the effect should be
386 		 * fairly benign.
387 		 */
388 		poison_scratch_page(page, size);
389 
390 #ifdef __linux__
391 		addr = dma_map_page_attrs(vm->dma,
392 					  page, 0, size,
393 					  PCI_DMA_BIDIRECTIONAL,
394 					  DMA_ATTR_SKIP_CPU_SYNC |
395 					  DMA_ATTR_NO_WARN);
396 		if (unlikely(dma_mapping_error(vm->dma, addr)))
397 			goto free_page;
398 #else
399 		addr = VM_PAGE_TO_PHYS(page);
400 #endif
401 
402 		if (unlikely(!IS_ALIGNED(addr, size)))
403 			goto unmap_page;
404 
405 		vm->scratch[0].base.page = page;
406 		vm->scratch[0].base.daddr = addr;
407 		vm->scratch_order = order;
408 		return 0;
409 
410 unmap_page:
411 #ifdef __linux__
412 		dma_unmap_page(vm->dma, addr, size, PCI_DMA_BIDIRECTIONAL);
413 free_page:
414 #endif
415 		__free_pages(page, order);
416 skip:
417 		if (size == I915_GTT_PAGE_SIZE_4K)
418 			return -ENOMEM;
419 
420 		size = I915_GTT_PAGE_SIZE_4K;
421 		gfp &= ~__GFP_NOWARN;
422 	} while (1);
423 }
424 
425 void cleanup_scratch_page(struct i915_address_space *vm)
426 {
427 	struct i915_page_dma *p = px_base(&vm->scratch[0]);
428 	unsigned int order = vm->scratch_order;
429 
430 #ifdef __linux__
431 	dma_unmap_page(vm->dma, p->daddr, BIT(order) << PAGE_SHIFT,
432 		       PCI_DMA_BIDIRECTIONAL);
433 #endif
434 	__free_pages(p->page, order);
435 }
436 
437 void free_scratch(struct i915_address_space *vm)
438 {
439 	int i;
440 
441 	if (!px_dma(&vm->scratch[0])) /* set to 0 on clones */
442 		return;
443 
444 	for (i = 1; i <= vm->top; i++) {
445 		if (!px_dma(&vm->scratch[i]))
446 			break;
447 		cleanup_page_dma(vm, px_base(&vm->scratch[i]));
448 	}
449 
450 	cleanup_scratch_page(vm);
451 }
452 
453 void gtt_write_workarounds(struct intel_gt *gt)
454 {
455 	struct drm_i915_private *i915 = gt->i915;
456 	struct intel_uncore *uncore = gt->uncore;
457 
458 	/*
459 	 * This function is for gtt related workarounds. This function is
460 	 * called on driver load and after a GPU reset, so you can place
461 	 * workarounds here even if they get overwritten by GPU reset.
462 	 */
463 	/* WaIncreaseDefaultTLBEntries:chv,bdw,skl,bxt,kbl,glk,cfl,cnl,icl */
464 	if (IS_BROADWELL(i915))
465 		intel_uncore_write(uncore,
466 				   GEN8_L3_LRA_1_GPGPU,
467 				   GEN8_L3_LRA_1_GPGPU_DEFAULT_VALUE_BDW);
468 	else if (IS_CHERRYVIEW(i915))
469 		intel_uncore_write(uncore,
470 				   GEN8_L3_LRA_1_GPGPU,
471 				   GEN8_L3_LRA_1_GPGPU_DEFAULT_VALUE_CHV);
472 	else if (IS_GEN9_LP(i915))
473 		intel_uncore_write(uncore,
474 				   GEN8_L3_LRA_1_GPGPU,
475 				   GEN9_L3_LRA_1_GPGPU_DEFAULT_VALUE_BXT);
476 	else if (INTEL_GEN(i915) >= 9 && INTEL_GEN(i915) <= 11)
477 		intel_uncore_write(uncore,
478 				   GEN8_L3_LRA_1_GPGPU,
479 				   GEN9_L3_LRA_1_GPGPU_DEFAULT_VALUE_SKL);
480 
481 	/*
482 	 * To support 64K PTEs we need to first enable the use of the
483 	 * Intermediate-Page-Size(IPS) bit of the PDE field via some magical
484 	 * mmio, otherwise the page-walker will simply ignore the IPS bit. This
485 	 * shouldn't be needed after GEN10.
486 	 *
487 	 * 64K pages were first introduced from BDW+, although technically they
488 	 * only *work* from gen9+. For pre-BDW we instead have the option for
489 	 * 32K pages, but we don't currently have any support for it in our
490 	 * driver.
491 	 */
492 	if (HAS_PAGE_SIZES(i915, I915_GTT_PAGE_SIZE_64K) &&
493 	    INTEL_GEN(i915) <= 10)
494 		intel_uncore_rmw(uncore,
495 				 GEN8_GAMW_ECO_DEV_RW_IA,
496 				 0,
497 				 GAMW_ECO_ENABLE_64K_IPS_FIELD);
498 
499 	if (IS_GEN_RANGE(i915, 8, 11)) {
500 		bool can_use_gtt_cache = true;
501 
502 		/*
503 		 * According to the BSpec if we use 2M/1G pages then we also
504 		 * need to disable the GTT cache. At least on BDW we can see
505 		 * visual corruption when using 2M pages, and not disabling the
506 		 * GTT cache.
507 		 */
508 		if (HAS_PAGE_SIZES(i915, I915_GTT_PAGE_SIZE_2M))
509 			can_use_gtt_cache = false;
510 
511 		/* WaGttCachingOffByDefault */
512 		intel_uncore_write(uncore,
513 				   HSW_GTT_CACHE_EN,
514 				   can_use_gtt_cache ? GTT_CACHE_EN_ALL : 0);
515 		drm_WARN_ON_ONCE(&i915->drm, can_use_gtt_cache &&
516 				 intel_uncore_read(uncore,
517 						   HSW_GTT_CACHE_EN) == 0);
518 	}
519 }
520 
521 static void tgl_setup_private_ppat(struct intel_uncore *uncore)
522 {
523 	/* TGL doesn't support LLC or AGE settings */
524 	intel_uncore_write(uncore, GEN12_PAT_INDEX(0), GEN8_PPAT_WB);
525 	intel_uncore_write(uncore, GEN12_PAT_INDEX(1), GEN8_PPAT_WC);
526 	intel_uncore_write(uncore, GEN12_PAT_INDEX(2), GEN8_PPAT_WT);
527 	intel_uncore_write(uncore, GEN12_PAT_INDEX(3), GEN8_PPAT_UC);
528 	intel_uncore_write(uncore, GEN12_PAT_INDEX(4), GEN8_PPAT_WB);
529 	intel_uncore_write(uncore, GEN12_PAT_INDEX(5), GEN8_PPAT_WB);
530 	intel_uncore_write(uncore, GEN12_PAT_INDEX(6), GEN8_PPAT_WB);
531 	intel_uncore_write(uncore, GEN12_PAT_INDEX(7), GEN8_PPAT_WB);
532 }
533 
534 static void cnl_setup_private_ppat(struct intel_uncore *uncore)
535 {
536 	intel_uncore_write(uncore,
537 			   GEN10_PAT_INDEX(0),
538 			   GEN8_PPAT_WB | GEN8_PPAT_LLC);
539 	intel_uncore_write(uncore,
540 			   GEN10_PAT_INDEX(1),
541 			   GEN8_PPAT_WC | GEN8_PPAT_LLCELLC);
542 	intel_uncore_write(uncore,
543 			   GEN10_PAT_INDEX(2),
544 			   GEN8_PPAT_WT | GEN8_PPAT_LLCELLC);
545 	intel_uncore_write(uncore,
546 			   GEN10_PAT_INDEX(3),
547 			   GEN8_PPAT_UC);
548 	intel_uncore_write(uncore,
549 			   GEN10_PAT_INDEX(4),
550 			   GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(0));
551 	intel_uncore_write(uncore,
552 			   GEN10_PAT_INDEX(5),
553 			   GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(1));
554 	intel_uncore_write(uncore,
555 			   GEN10_PAT_INDEX(6),
556 			   GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(2));
557 	intel_uncore_write(uncore,
558 			   GEN10_PAT_INDEX(7),
559 			   GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(3));
560 }
561 
562 /*
563  * The GGTT and PPGTT need a private PPAT setup in order to handle cacheability
564  * bits. When using advanced contexts each context stores its own PAT, but
565  * writing this data shouldn't be harmful even in those cases.
566  */
567 static void bdw_setup_private_ppat(struct intel_uncore *uncore)
568 {
569 	u64 pat;
570 
571 	pat = GEN8_PPAT(0, GEN8_PPAT_WB | GEN8_PPAT_LLC) |	/* for normal objects, no eLLC */
572 	      GEN8_PPAT(1, GEN8_PPAT_WC | GEN8_PPAT_LLCELLC) |	/* for something pointing to ptes? */
573 	      GEN8_PPAT(2, GEN8_PPAT_WT | GEN8_PPAT_LLCELLC) |	/* for scanout with eLLC */
574 	      GEN8_PPAT(3, GEN8_PPAT_UC) |			/* Uncached objects, mostly for scanout */
575 	      GEN8_PPAT(4, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(0)) |
576 	      GEN8_PPAT(5, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(1)) |
577 	      GEN8_PPAT(6, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(2)) |
578 	      GEN8_PPAT(7, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(3));
579 
580 	intel_uncore_write(uncore, GEN8_PRIVATE_PAT_LO, lower_32_bits(pat));
581 	intel_uncore_write(uncore, GEN8_PRIVATE_PAT_HI, upper_32_bits(pat));
582 }
583 
584 static void chv_setup_private_ppat(struct intel_uncore *uncore)
585 {
586 	u64 pat;
587 
588 	/*
589 	 * Map WB on BDW to snooped on CHV.
590 	 *
591 	 * Only the snoop bit has meaning for CHV, the rest is
592 	 * ignored.
593 	 *
594 	 * The hardware will never snoop for certain types of accesses:
595 	 * - CPU GTT (GMADR->GGTT->no snoop->memory)
596 	 * - PPGTT page tables
597 	 * - some other special cycles
598 	 *
599 	 * As with BDW, we also need to consider the following for GT accesses:
600 	 * "For GGTT, there is NO pat_sel[2:0] from the entry,
601 	 * so RTL will always use the value corresponding to
602 	 * pat_sel = 000".
603 	 * Which means we must set the snoop bit in PAT entry 0
604 	 * in order to keep the global status page working.
605 	 */
606 
607 	pat = GEN8_PPAT(0, CHV_PPAT_SNOOP) |
608 	      GEN8_PPAT(1, 0) |
609 	      GEN8_PPAT(2, 0) |
610 	      GEN8_PPAT(3, 0) |
611 	      GEN8_PPAT(4, CHV_PPAT_SNOOP) |
612 	      GEN8_PPAT(5, CHV_PPAT_SNOOP) |
613 	      GEN8_PPAT(6, CHV_PPAT_SNOOP) |
614 	      GEN8_PPAT(7, CHV_PPAT_SNOOP);
615 
616 	intel_uncore_write(uncore, GEN8_PRIVATE_PAT_LO, lower_32_bits(pat));
617 	intel_uncore_write(uncore, GEN8_PRIVATE_PAT_HI, upper_32_bits(pat));
618 }
619 
620 void setup_private_pat(struct intel_uncore *uncore)
621 {
622 	struct drm_i915_private *i915 = uncore->i915;
623 
624 	GEM_BUG_ON(INTEL_GEN(i915) < 8);
625 
626 	if (INTEL_GEN(i915) >= 12)
627 		tgl_setup_private_ppat(uncore);
628 	else if (INTEL_GEN(i915) >= 10)
629 		cnl_setup_private_ppat(uncore);
630 	else if (IS_CHERRYVIEW(i915) || IS_GEN9_LP(i915))
631 		chv_setup_private_ppat(uncore);
632 	else
633 		bdw_setup_private_ppat(uncore);
634 }
635 
636 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
637 #include "selftests/mock_gtt.c"
638 #endif
639