xref: /openbmc/linux/arch/x86/mm/pgtable.c (revision 7effbd18)
1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/mm.h>
3 #include <linux/gfp.h>
4 #include <linux/hugetlb.h>
5 #include <asm/pgalloc.h>
6 #include <asm/tlb.h>
7 #include <asm/fixmap.h>
8 #include <asm/mtrr.h>
9 
10 #ifdef CONFIG_DYNAMIC_PHYSICAL_MASK
11 phys_addr_t physical_mask __ro_after_init = (1ULL << __PHYSICAL_MASK_SHIFT) - 1;
12 EXPORT_SYMBOL(physical_mask);
13 #endif
14 
15 #ifdef CONFIG_HIGHPTE
16 #define PGTABLE_HIGHMEM __GFP_HIGHMEM
17 #else
18 #define PGTABLE_HIGHMEM 0
19 #endif
20 
21 #ifndef CONFIG_PARAVIRT
22 static inline
23 void paravirt_tlb_remove_table(struct mmu_gather *tlb, void *table)
24 {
25 	tlb_remove_page(tlb, table);
26 }
27 #endif
28 
29 gfp_t __userpte_alloc_gfp = GFP_PGTABLE_USER | PGTABLE_HIGHMEM;
30 
31 pgtable_t pte_alloc_one(struct mm_struct *mm)
32 {
33 	return __pte_alloc_one(mm, __userpte_alloc_gfp);
34 }
35 
36 static int __init setup_userpte(char *arg)
37 {
38 	if (!arg)
39 		return -EINVAL;
40 
41 	/*
42 	 * "userpte=nohigh" disables allocation of user pagetables in
43 	 * high memory.
44 	 */
45 	if (strcmp(arg, "nohigh") == 0)
46 		__userpte_alloc_gfp &= ~__GFP_HIGHMEM;
47 	else
48 		return -EINVAL;
49 	return 0;
50 }
51 early_param("userpte", setup_userpte);
52 
53 void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
54 {
55 	pgtable_pte_page_dtor(pte);
56 	paravirt_release_pte(page_to_pfn(pte));
57 	paravirt_tlb_remove_table(tlb, pte);
58 }
59 
60 #if CONFIG_PGTABLE_LEVELS > 2
61 void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
62 {
63 	struct page *page = virt_to_page(pmd);
64 	paravirt_release_pmd(__pa(pmd) >> PAGE_SHIFT);
65 	/*
66 	 * NOTE! For PAE, any changes to the top page-directory-pointer-table
67 	 * entries need a full cr3 reload to flush.
68 	 */
69 #ifdef CONFIG_X86_PAE
70 	tlb->need_flush_all = 1;
71 #endif
72 	pgtable_pmd_page_dtor(page);
73 	paravirt_tlb_remove_table(tlb, page);
74 }
75 
76 #if CONFIG_PGTABLE_LEVELS > 3
77 void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
78 {
79 	paravirt_release_pud(__pa(pud) >> PAGE_SHIFT);
80 	paravirt_tlb_remove_table(tlb, virt_to_page(pud));
81 }
82 
83 #if CONFIG_PGTABLE_LEVELS > 4
84 void ___p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d)
85 {
86 	paravirt_release_p4d(__pa(p4d) >> PAGE_SHIFT);
87 	paravirt_tlb_remove_table(tlb, virt_to_page(p4d));
88 }
89 #endif	/* CONFIG_PGTABLE_LEVELS > 4 */
90 #endif	/* CONFIG_PGTABLE_LEVELS > 3 */
91 #endif	/* CONFIG_PGTABLE_LEVELS > 2 */
92 
93 static inline void pgd_list_add(pgd_t *pgd)
94 {
95 	struct page *page = virt_to_page(pgd);
96 
97 	list_add(&page->lru, &pgd_list);
98 }
99 
100 static inline void pgd_list_del(pgd_t *pgd)
101 {
102 	struct page *page = virt_to_page(pgd);
103 
104 	list_del(&page->lru);
105 }
106 
107 #define UNSHARED_PTRS_PER_PGD				\
108 	(SHARED_KERNEL_PMD ? KERNEL_PGD_BOUNDARY : PTRS_PER_PGD)
109 #define MAX_UNSHARED_PTRS_PER_PGD			\
110 	max_t(size_t, KERNEL_PGD_BOUNDARY, PTRS_PER_PGD)
111 
112 
113 static void pgd_set_mm(pgd_t *pgd, struct mm_struct *mm)
114 {
115 	virt_to_page(pgd)->pt_mm = mm;
116 }
117 
118 struct mm_struct *pgd_page_get_mm(struct page *page)
119 {
120 	return page->pt_mm;
121 }
122 
123 static void pgd_ctor(struct mm_struct *mm, pgd_t *pgd)
124 {
125 	/* If the pgd points to a shared pagetable level (either the
126 	   ptes in non-PAE, or shared PMD in PAE), then just copy the
127 	   references from swapper_pg_dir. */
128 	if (CONFIG_PGTABLE_LEVELS == 2 ||
129 	    (CONFIG_PGTABLE_LEVELS == 3 && SHARED_KERNEL_PMD) ||
130 	    CONFIG_PGTABLE_LEVELS >= 4) {
131 		clone_pgd_range(pgd + KERNEL_PGD_BOUNDARY,
132 				swapper_pg_dir + KERNEL_PGD_BOUNDARY,
133 				KERNEL_PGD_PTRS);
134 	}
135 
136 	/* list required to sync kernel mapping updates */
137 	if (!SHARED_KERNEL_PMD) {
138 		pgd_set_mm(pgd, mm);
139 		pgd_list_add(pgd);
140 	}
141 }
142 
143 static void pgd_dtor(pgd_t *pgd)
144 {
145 	if (SHARED_KERNEL_PMD)
146 		return;
147 
148 	spin_lock(&pgd_lock);
149 	pgd_list_del(pgd);
150 	spin_unlock(&pgd_lock);
151 }
152 
153 /*
154  * List of all pgd's needed for non-PAE so it can invalidate entries
155  * in both cached and uncached pgd's; not needed for PAE since the
156  * kernel pmd is shared. If PAE were not to share the pmd a similar
157  * tactic would be needed. This is essentially codepath-based locking
158  * against pageattr.c; it is the unique case in which a valid change
159  * of kernel pagetables can't be lazily synchronized by vmalloc faults.
160  * vmalloc faults work because attached pagetables are never freed.
161  * -- nyc
162  */
163 
164 #ifdef CONFIG_X86_PAE
165 /*
166  * In PAE mode, we need to do a cr3 reload (=tlb flush) when
167  * updating the top-level pagetable entries to guarantee the
168  * processor notices the update.  Since this is expensive, and
169  * all 4 top-level entries are used almost immediately in a
170  * new process's life, we just pre-populate them here.
171  *
172  * Also, if we're in a paravirt environment where the kernel pmd is
173  * not shared between pagetables (!SHARED_KERNEL_PMDS), we allocate
174  * and initialize the kernel pmds here.
175  */
176 #define PREALLOCATED_PMDS	UNSHARED_PTRS_PER_PGD
177 #define MAX_PREALLOCATED_PMDS	MAX_UNSHARED_PTRS_PER_PGD
178 
179 /*
180  * We allocate separate PMDs for the kernel part of the user page-table
181  * when PTI is enabled. We need them to map the per-process LDT into the
182  * user-space page-table.
183  */
184 #define PREALLOCATED_USER_PMDS	 (boot_cpu_has(X86_FEATURE_PTI) ? \
185 					KERNEL_PGD_PTRS : 0)
186 #define MAX_PREALLOCATED_USER_PMDS KERNEL_PGD_PTRS
187 
188 void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd)
189 {
190 	paravirt_alloc_pmd(mm, __pa(pmd) >> PAGE_SHIFT);
191 
192 	/* Note: almost everything apart from _PAGE_PRESENT is
193 	   reserved at the pmd (PDPT) level. */
194 	set_pud(pudp, __pud(__pa(pmd) | _PAGE_PRESENT));
195 
196 	/*
197 	 * According to Intel App note "TLBs, Paging-Structure Caches,
198 	 * and Their Invalidation", April 2007, document 317080-001,
199 	 * section 8.1: in PAE mode we explicitly have to flush the
200 	 * TLB via cr3 if the top-level pgd is changed...
201 	 */
202 	flush_tlb_mm(mm);
203 }
204 #else  /* !CONFIG_X86_PAE */
205 
206 /* No need to prepopulate any pagetable entries in non-PAE modes. */
207 #define PREALLOCATED_PMDS	0
208 #define MAX_PREALLOCATED_PMDS	0
209 #define PREALLOCATED_USER_PMDS	 0
210 #define MAX_PREALLOCATED_USER_PMDS 0
211 #endif	/* CONFIG_X86_PAE */
212 
213 static void free_pmds(struct mm_struct *mm, pmd_t *pmds[], int count)
214 {
215 	int i;
216 
217 	for (i = 0; i < count; i++)
218 		if (pmds[i]) {
219 			pgtable_pmd_page_dtor(virt_to_page(pmds[i]));
220 			free_page((unsigned long)pmds[i]);
221 			mm_dec_nr_pmds(mm);
222 		}
223 }
224 
225 static int preallocate_pmds(struct mm_struct *mm, pmd_t *pmds[], int count)
226 {
227 	int i;
228 	bool failed = false;
229 	gfp_t gfp = GFP_PGTABLE_USER;
230 
231 	if (mm == &init_mm)
232 		gfp &= ~__GFP_ACCOUNT;
233 
234 	for (i = 0; i < count; i++) {
235 		pmd_t *pmd = (pmd_t *)__get_free_page(gfp);
236 		if (!pmd)
237 			failed = true;
238 		if (pmd && !pgtable_pmd_page_ctor(virt_to_page(pmd))) {
239 			free_page((unsigned long)pmd);
240 			pmd = NULL;
241 			failed = true;
242 		}
243 		if (pmd)
244 			mm_inc_nr_pmds(mm);
245 		pmds[i] = pmd;
246 	}
247 
248 	if (failed) {
249 		free_pmds(mm, pmds, count);
250 		return -ENOMEM;
251 	}
252 
253 	return 0;
254 }
255 
256 /*
257  * Mop up any pmd pages which may still be attached to the pgd.
258  * Normally they will be freed by munmap/exit_mmap, but any pmd we
259  * preallocate which never got a corresponding vma will need to be
260  * freed manually.
261  */
262 static void mop_up_one_pmd(struct mm_struct *mm, pgd_t *pgdp)
263 {
264 	pgd_t pgd = *pgdp;
265 
266 	if (pgd_val(pgd) != 0) {
267 		pmd_t *pmd = (pmd_t *)pgd_page_vaddr(pgd);
268 
269 		pgd_clear(pgdp);
270 
271 		paravirt_release_pmd(pgd_val(pgd) >> PAGE_SHIFT);
272 		pmd_free(mm, pmd);
273 		mm_dec_nr_pmds(mm);
274 	}
275 }
276 
277 static void pgd_mop_up_pmds(struct mm_struct *mm, pgd_t *pgdp)
278 {
279 	int i;
280 
281 	for (i = 0; i < PREALLOCATED_PMDS; i++)
282 		mop_up_one_pmd(mm, &pgdp[i]);
283 
284 #ifdef CONFIG_PAGE_TABLE_ISOLATION
285 
286 	if (!boot_cpu_has(X86_FEATURE_PTI))
287 		return;
288 
289 	pgdp = kernel_to_user_pgdp(pgdp);
290 
291 	for (i = 0; i < PREALLOCATED_USER_PMDS; i++)
292 		mop_up_one_pmd(mm, &pgdp[i + KERNEL_PGD_BOUNDARY]);
293 #endif
294 }
295 
296 static void pgd_prepopulate_pmd(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmds[])
297 {
298 	p4d_t *p4d;
299 	pud_t *pud;
300 	int i;
301 
302 	p4d = p4d_offset(pgd, 0);
303 	pud = pud_offset(p4d, 0);
304 
305 	for (i = 0; i < PREALLOCATED_PMDS; i++, pud++) {
306 		pmd_t *pmd = pmds[i];
307 
308 		if (i >= KERNEL_PGD_BOUNDARY)
309 			memcpy(pmd, (pmd_t *)pgd_page_vaddr(swapper_pg_dir[i]),
310 			       sizeof(pmd_t) * PTRS_PER_PMD);
311 
312 		pud_populate(mm, pud, pmd);
313 	}
314 }
315 
316 #ifdef CONFIG_PAGE_TABLE_ISOLATION
317 static void pgd_prepopulate_user_pmd(struct mm_struct *mm,
318 				     pgd_t *k_pgd, pmd_t *pmds[])
319 {
320 	pgd_t *s_pgd = kernel_to_user_pgdp(swapper_pg_dir);
321 	pgd_t *u_pgd = kernel_to_user_pgdp(k_pgd);
322 	p4d_t *u_p4d;
323 	pud_t *u_pud;
324 	int i;
325 
326 	u_p4d = p4d_offset(u_pgd, 0);
327 	u_pud = pud_offset(u_p4d, 0);
328 
329 	s_pgd += KERNEL_PGD_BOUNDARY;
330 	u_pud += KERNEL_PGD_BOUNDARY;
331 
332 	for (i = 0; i < PREALLOCATED_USER_PMDS; i++, u_pud++, s_pgd++) {
333 		pmd_t *pmd = pmds[i];
334 
335 		memcpy(pmd, (pmd_t *)pgd_page_vaddr(*s_pgd),
336 		       sizeof(pmd_t) * PTRS_PER_PMD);
337 
338 		pud_populate(mm, u_pud, pmd);
339 	}
340 
341 }
342 #else
343 static void pgd_prepopulate_user_pmd(struct mm_struct *mm,
344 				     pgd_t *k_pgd, pmd_t *pmds[])
345 {
346 }
347 #endif
348 /*
349  * Xen paravirt assumes pgd table should be in one page. 64 bit kernel also
350  * assumes that pgd should be in one page.
351  *
352  * But kernel with PAE paging that is not running as a Xen domain
353  * only needs to allocate 32 bytes for pgd instead of one page.
354  */
355 #ifdef CONFIG_X86_PAE
356 
357 #include <linux/slab.h>
358 
359 #define PGD_SIZE	(PTRS_PER_PGD * sizeof(pgd_t))
360 #define PGD_ALIGN	32
361 
362 static struct kmem_cache *pgd_cache;
363 
364 void __init pgtable_cache_init(void)
365 {
366 	/*
367 	 * When PAE kernel is running as a Xen domain, it does not use
368 	 * shared kernel pmd. And this requires a whole page for pgd.
369 	 */
370 	if (!SHARED_KERNEL_PMD)
371 		return;
372 
373 	/*
374 	 * when PAE kernel is not running as a Xen domain, it uses
375 	 * shared kernel pmd. Shared kernel pmd does not require a whole
376 	 * page for pgd. We are able to just allocate a 32-byte for pgd.
377 	 * During boot time, we create a 32-byte slab for pgd table allocation.
378 	 */
379 	pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_ALIGN,
380 				      SLAB_PANIC, NULL);
381 }
382 
383 static inline pgd_t *_pgd_alloc(void)
384 {
385 	/*
386 	 * If no SHARED_KERNEL_PMD, PAE kernel is running as a Xen domain.
387 	 * We allocate one page for pgd.
388 	 */
389 	if (!SHARED_KERNEL_PMD)
390 		return (pgd_t *)__get_free_pages(GFP_PGTABLE_USER,
391 						 PGD_ALLOCATION_ORDER);
392 
393 	/*
394 	 * Now PAE kernel is not running as a Xen domain. We can allocate
395 	 * a 32-byte slab for pgd to save memory space.
396 	 */
397 	return kmem_cache_alloc(pgd_cache, GFP_PGTABLE_USER);
398 }
399 
400 static inline void _pgd_free(pgd_t *pgd)
401 {
402 	if (!SHARED_KERNEL_PMD)
403 		free_pages((unsigned long)pgd, PGD_ALLOCATION_ORDER);
404 	else
405 		kmem_cache_free(pgd_cache, pgd);
406 }
407 #else
408 
409 static inline pgd_t *_pgd_alloc(void)
410 {
411 	return (pgd_t *)__get_free_pages(GFP_PGTABLE_USER,
412 					 PGD_ALLOCATION_ORDER);
413 }
414 
415 static inline void _pgd_free(pgd_t *pgd)
416 {
417 	free_pages((unsigned long)pgd, PGD_ALLOCATION_ORDER);
418 }
419 #endif /* CONFIG_X86_PAE */
420 
421 pgd_t *pgd_alloc(struct mm_struct *mm)
422 {
423 	pgd_t *pgd;
424 	pmd_t *u_pmds[MAX_PREALLOCATED_USER_PMDS];
425 	pmd_t *pmds[MAX_PREALLOCATED_PMDS];
426 
427 	pgd = _pgd_alloc();
428 
429 	if (pgd == NULL)
430 		goto out;
431 
432 	mm->pgd = pgd;
433 
434 	if (sizeof(pmds) != 0 &&
435 			preallocate_pmds(mm, pmds, PREALLOCATED_PMDS) != 0)
436 		goto out_free_pgd;
437 
438 	if (sizeof(u_pmds) != 0 &&
439 			preallocate_pmds(mm, u_pmds, PREALLOCATED_USER_PMDS) != 0)
440 		goto out_free_pmds;
441 
442 	if (paravirt_pgd_alloc(mm) != 0)
443 		goto out_free_user_pmds;
444 
445 	/*
446 	 * Make sure that pre-populating the pmds is atomic with
447 	 * respect to anything walking the pgd_list, so that they
448 	 * never see a partially populated pgd.
449 	 */
450 	spin_lock(&pgd_lock);
451 
452 	pgd_ctor(mm, pgd);
453 	if (sizeof(pmds) != 0)
454 		pgd_prepopulate_pmd(mm, pgd, pmds);
455 
456 	if (sizeof(u_pmds) != 0)
457 		pgd_prepopulate_user_pmd(mm, pgd, u_pmds);
458 
459 	spin_unlock(&pgd_lock);
460 
461 	return pgd;
462 
463 out_free_user_pmds:
464 	if (sizeof(u_pmds) != 0)
465 		free_pmds(mm, u_pmds, PREALLOCATED_USER_PMDS);
466 out_free_pmds:
467 	if (sizeof(pmds) != 0)
468 		free_pmds(mm, pmds, PREALLOCATED_PMDS);
469 out_free_pgd:
470 	_pgd_free(pgd);
471 out:
472 	return NULL;
473 }
474 
475 void pgd_free(struct mm_struct *mm, pgd_t *pgd)
476 {
477 	pgd_mop_up_pmds(mm, pgd);
478 	pgd_dtor(pgd);
479 	paravirt_pgd_free(mm, pgd);
480 	_pgd_free(pgd);
481 }
482 
483 /*
484  * Used to set accessed or dirty bits in the page table entries
485  * on other architectures. On x86, the accessed and dirty bits
486  * are tracked by hardware. However, do_wp_page calls this function
487  * to also make the pte writeable at the same time the dirty bit is
488  * set. In that case we do actually need to write the PTE.
489  */
490 int ptep_set_access_flags(struct vm_area_struct *vma,
491 			  unsigned long address, pte_t *ptep,
492 			  pte_t entry, int dirty)
493 {
494 	int changed = !pte_same(*ptep, entry);
495 
496 	if (changed && dirty)
497 		set_pte(ptep, entry);
498 
499 	return changed;
500 }
501 
502 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
503 int pmdp_set_access_flags(struct vm_area_struct *vma,
504 			  unsigned long address, pmd_t *pmdp,
505 			  pmd_t entry, int dirty)
506 {
507 	int changed = !pmd_same(*pmdp, entry);
508 
509 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
510 
511 	if (changed && dirty) {
512 		set_pmd(pmdp, entry);
513 		/*
514 		 * We had a write-protection fault here and changed the pmd
515 		 * to to more permissive. No need to flush the TLB for that,
516 		 * #PF is architecturally guaranteed to do that and in the
517 		 * worst-case we'll generate a spurious fault.
518 		 */
519 	}
520 
521 	return changed;
522 }
523 
524 int pudp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
525 			  pud_t *pudp, pud_t entry, int dirty)
526 {
527 	int changed = !pud_same(*pudp, entry);
528 
529 	VM_BUG_ON(address & ~HPAGE_PUD_MASK);
530 
531 	if (changed && dirty) {
532 		set_pud(pudp, entry);
533 		/*
534 		 * We had a write-protection fault here and changed the pud
535 		 * to to more permissive. No need to flush the TLB for that,
536 		 * #PF is architecturally guaranteed to do that and in the
537 		 * worst-case we'll generate a spurious fault.
538 		 */
539 	}
540 
541 	return changed;
542 }
543 #endif
544 
545 int ptep_test_and_clear_young(struct vm_area_struct *vma,
546 			      unsigned long addr, pte_t *ptep)
547 {
548 	int ret = 0;
549 
550 	if (pte_young(*ptep))
551 		ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
552 					 (unsigned long *) &ptep->pte);
553 
554 	return ret;
555 }
556 
557 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
558 int pmdp_test_and_clear_young(struct vm_area_struct *vma,
559 			      unsigned long addr, pmd_t *pmdp)
560 {
561 	int ret = 0;
562 
563 	if (pmd_young(*pmdp))
564 		ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
565 					 (unsigned long *)pmdp);
566 
567 	return ret;
568 }
569 #endif
570 
571 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
572 int pudp_test_and_clear_young(struct vm_area_struct *vma,
573 			      unsigned long addr, pud_t *pudp)
574 {
575 	int ret = 0;
576 
577 	if (pud_young(*pudp))
578 		ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
579 					 (unsigned long *)pudp);
580 
581 	return ret;
582 }
583 #endif
584 
585 int ptep_clear_flush_young(struct vm_area_struct *vma,
586 			   unsigned long address, pte_t *ptep)
587 {
588 	/*
589 	 * On x86 CPUs, clearing the accessed bit without a TLB flush
590 	 * doesn't cause data corruption. [ It could cause incorrect
591 	 * page aging and the (mistaken) reclaim of hot pages, but the
592 	 * chance of that should be relatively low. ]
593 	 *
594 	 * So as a performance optimization don't flush the TLB when
595 	 * clearing the accessed bit, it will eventually be flushed by
596 	 * a context switch or a VM operation anyway. [ In the rare
597 	 * event of it not getting flushed for a long time the delay
598 	 * shouldn't really matter because there's no real memory
599 	 * pressure for swapout to react to. ]
600 	 */
601 	return ptep_test_and_clear_young(vma, address, ptep);
602 }
603 
604 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
605 int pmdp_clear_flush_young(struct vm_area_struct *vma,
606 			   unsigned long address, pmd_t *pmdp)
607 {
608 	int young;
609 
610 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
611 
612 	young = pmdp_test_and_clear_young(vma, address, pmdp);
613 	if (young)
614 		flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
615 
616 	return young;
617 }
618 
619 pmd_t pmdp_invalidate_ad(struct vm_area_struct *vma, unsigned long address,
620 			 pmd_t *pmdp)
621 {
622 	/*
623 	 * No flush is necessary. Once an invalid PTE is established, the PTE's
624 	 * access and dirty bits cannot be updated.
625 	 */
626 	return pmdp_establish(vma, address, pmdp, pmd_mkinvalid(*pmdp));
627 }
628 #endif
629 
630 /**
631  * reserve_top_address - reserves a hole in the top of kernel address space
632  * @reserve - size of hole to reserve
633  *
634  * Can be used to relocate the fixmap area and poke a hole in the top
635  * of kernel address space to make room for a hypervisor.
636  */
637 void __init reserve_top_address(unsigned long reserve)
638 {
639 #ifdef CONFIG_X86_32
640 	BUG_ON(fixmaps_set > 0);
641 	__FIXADDR_TOP = round_down(-reserve, 1 << PMD_SHIFT) - PAGE_SIZE;
642 	printk(KERN_INFO "Reserving virtual address space above 0x%08lx (rounded to 0x%08lx)\n",
643 	       -reserve, __FIXADDR_TOP + PAGE_SIZE);
644 #endif
645 }
646 
647 int fixmaps_set;
648 
649 void __native_set_fixmap(enum fixed_addresses idx, pte_t pte)
650 {
651 	unsigned long address = __fix_to_virt(idx);
652 
653 #ifdef CONFIG_X86_64
654        /*
655 	* Ensure that the static initial page tables are covering the
656 	* fixmap completely.
657 	*/
658 	BUILD_BUG_ON(__end_of_permanent_fixed_addresses >
659 		     (FIXMAP_PMD_NUM * PTRS_PER_PTE));
660 #endif
661 
662 	if (idx >= __end_of_fixed_addresses) {
663 		BUG();
664 		return;
665 	}
666 	set_pte_vaddr(address, pte);
667 	fixmaps_set++;
668 }
669 
670 void native_set_fixmap(unsigned /* enum fixed_addresses */ idx,
671 		       phys_addr_t phys, pgprot_t flags)
672 {
673 	/* Sanitize 'prot' against any unsupported bits: */
674 	pgprot_val(flags) &= __default_kernel_pte_mask;
675 
676 	__native_set_fixmap(idx, pfn_pte(phys >> PAGE_SHIFT, flags));
677 }
678 
679 #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
680 #ifdef CONFIG_X86_5LEVEL
681 /**
682  * p4d_set_huge - setup kernel P4D mapping
683  *
684  * No 512GB pages yet -- always return 0
685  */
686 int p4d_set_huge(p4d_t *p4d, phys_addr_t addr, pgprot_t prot)
687 {
688 	return 0;
689 }
690 
691 /**
692  * p4d_clear_huge - clear kernel P4D mapping when it is set
693  *
694  * No 512GB pages yet -- always return 0
695  */
696 void p4d_clear_huge(p4d_t *p4d)
697 {
698 }
699 #endif
700 
701 /**
702  * pud_set_huge - setup kernel PUD mapping
703  *
704  * MTRRs can override PAT memory types with 4KiB granularity. Therefore, this
705  * function sets up a huge page only if any of the following conditions are met:
706  *
707  * - MTRRs are disabled, or
708  *
709  * - MTRRs are enabled and the range is completely covered by a single MTRR, or
710  *
711  * - MTRRs are enabled and the corresponding MTRR memory type is WB, which
712  *   has no effect on the requested PAT memory type.
713  *
714  * Callers should try to decrease page size (1GB -> 2MB -> 4K) if the bigger
715  * page mapping attempt fails.
716  *
717  * Returns 1 on success and 0 on failure.
718  */
719 int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
720 {
721 	u8 mtrr, uniform;
722 
723 	mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE, &uniform);
724 	if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) &&
725 	    (mtrr != MTRR_TYPE_WRBACK))
726 		return 0;
727 
728 	/* Bail out if we are we on a populated non-leaf entry: */
729 	if (pud_present(*pud) && !pud_huge(*pud))
730 		return 0;
731 
732 	set_pte((pte_t *)pud, pfn_pte(
733 		(u64)addr >> PAGE_SHIFT,
734 		__pgprot(protval_4k_2_large(pgprot_val(prot)) | _PAGE_PSE)));
735 
736 	return 1;
737 }
738 
739 /**
740  * pmd_set_huge - setup kernel PMD mapping
741  *
742  * See text over pud_set_huge() above.
743  *
744  * Returns 1 on success and 0 on failure.
745  */
746 int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
747 {
748 	u8 mtrr, uniform;
749 
750 	mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE, &uniform);
751 	if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) &&
752 	    (mtrr != MTRR_TYPE_WRBACK)) {
753 		pr_warn_once("%s: Cannot satisfy [mem %#010llx-%#010llx] with a huge-page mapping due to MTRR override.\n",
754 			     __func__, addr, addr + PMD_SIZE);
755 		return 0;
756 	}
757 
758 	/* Bail out if we are we on a populated non-leaf entry: */
759 	if (pmd_present(*pmd) && !pmd_huge(*pmd))
760 		return 0;
761 
762 	set_pte((pte_t *)pmd, pfn_pte(
763 		(u64)addr >> PAGE_SHIFT,
764 		__pgprot(protval_4k_2_large(pgprot_val(prot)) | _PAGE_PSE)));
765 
766 	return 1;
767 }
768 
769 /**
770  * pud_clear_huge - clear kernel PUD mapping when it is set
771  *
772  * Returns 1 on success and 0 on failure (no PUD map is found).
773  */
774 int pud_clear_huge(pud_t *pud)
775 {
776 	if (pud_large(*pud)) {
777 		pud_clear(pud);
778 		return 1;
779 	}
780 
781 	return 0;
782 }
783 
784 /**
785  * pmd_clear_huge - clear kernel PMD mapping when it is set
786  *
787  * Returns 1 on success and 0 on failure (no PMD map is found).
788  */
789 int pmd_clear_huge(pmd_t *pmd)
790 {
791 	if (pmd_large(*pmd)) {
792 		pmd_clear(pmd);
793 		return 1;
794 	}
795 
796 	return 0;
797 }
798 
799 #ifdef CONFIG_X86_64
800 /**
801  * pud_free_pmd_page - Clear pud entry and free pmd page.
802  * @pud: Pointer to a PUD.
803  * @addr: Virtual address associated with pud.
804  *
805  * Context: The pud range has been unmapped and TLB purged.
806  * Return: 1 if clearing the entry succeeded. 0 otherwise.
807  *
808  * NOTE: Callers must allow a single page allocation.
809  */
810 int pud_free_pmd_page(pud_t *pud, unsigned long addr)
811 {
812 	pmd_t *pmd, *pmd_sv;
813 	pte_t *pte;
814 	int i;
815 
816 	pmd = pud_pgtable(*pud);
817 	pmd_sv = (pmd_t *)__get_free_page(GFP_KERNEL);
818 	if (!pmd_sv)
819 		return 0;
820 
821 	for (i = 0; i < PTRS_PER_PMD; i++) {
822 		pmd_sv[i] = pmd[i];
823 		if (!pmd_none(pmd[i]))
824 			pmd_clear(&pmd[i]);
825 	}
826 
827 	pud_clear(pud);
828 
829 	/* INVLPG to clear all paging-structure caches */
830 	flush_tlb_kernel_range(addr, addr + PAGE_SIZE-1);
831 
832 	for (i = 0; i < PTRS_PER_PMD; i++) {
833 		if (!pmd_none(pmd_sv[i])) {
834 			pte = (pte_t *)pmd_page_vaddr(pmd_sv[i]);
835 			free_page((unsigned long)pte);
836 		}
837 	}
838 
839 	free_page((unsigned long)pmd_sv);
840 
841 	pgtable_pmd_page_dtor(virt_to_page(pmd));
842 	free_page((unsigned long)pmd);
843 
844 	return 1;
845 }
846 
847 /**
848  * pmd_free_pte_page - Clear pmd entry and free pte page.
849  * @pmd: Pointer to a PMD.
850  * @addr: Virtual address associated with pmd.
851  *
852  * Context: The pmd range has been unmapped and TLB purged.
853  * Return: 1 if clearing the entry succeeded. 0 otherwise.
854  */
855 int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
856 {
857 	pte_t *pte;
858 
859 	pte = (pte_t *)pmd_page_vaddr(*pmd);
860 	pmd_clear(pmd);
861 
862 	/* INVLPG to clear all paging-structure caches */
863 	flush_tlb_kernel_range(addr, addr + PAGE_SIZE-1);
864 
865 	free_page((unsigned long)pte);
866 
867 	return 1;
868 }
869 
870 #else /* !CONFIG_X86_64 */
871 
872 /*
873  * Disable free page handling on x86-PAE. This assures that ioremap()
874  * does not update sync'd pmd entries. See vmalloc_sync_one().
875  */
876 int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
877 {
878 	return pmd_none(*pmd);
879 }
880 
881 #endif /* CONFIG_X86_64 */
882 #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */
883