xref: /linux/arch/x86/mm/hugetlbpage.c (revision 08ec212c0f92cbf30e3ecc7349f18151714041d6)
1 /*
2  * IA-32 Huge TLB Page Support for Kernel.
3  *
4  * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
5  */
6 
7 #include <linux/init.h>
8 #include <linux/fs.h>
9 #include <linux/mm.h>
10 #include <linux/hugetlb.h>
11 #include <linux/pagemap.h>
12 #include <linux/err.h>
13 #include <linux/sysctl.h>
14 #include <asm/mman.h>
15 #include <asm/tlb.h>
16 #include <asm/tlbflush.h>
17 #include <asm/pgalloc.h>
18 
19 static unsigned long page_table_shareable(struct vm_area_struct *svma,
20 				struct vm_area_struct *vma,
21 				unsigned long addr, pgoff_t idx)
22 {
23 	unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
24 				svma->vm_start;
25 	unsigned long sbase = saddr & PUD_MASK;
26 	unsigned long s_end = sbase + PUD_SIZE;
27 
28 	/* Allow segments to share if only one is marked locked */
29 	unsigned long vm_flags = vma->vm_flags & ~VM_LOCKED;
30 	unsigned long svm_flags = svma->vm_flags & ~VM_LOCKED;
31 
32 	/*
33 	 * match the virtual addresses, permission and the alignment of the
34 	 * page table page.
35 	 */
36 	if (pmd_index(addr) != pmd_index(saddr) ||
37 	    vm_flags != svm_flags ||
38 	    sbase < svma->vm_start || svma->vm_end < s_end)
39 		return 0;
40 
41 	return saddr;
42 }
43 
44 static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
45 {
46 	unsigned long base = addr & PUD_MASK;
47 	unsigned long end = base + PUD_SIZE;
48 
49 	/*
50 	 * check on proper vm_flags and page table alignment
51 	 */
52 	if (vma->vm_flags & VM_MAYSHARE &&
53 	    vma->vm_start <= base && end <= vma->vm_end)
54 		return 1;
55 	return 0;
56 }
57 
58 /*
59  * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
60  * and returns the corresponding pte. While this is not necessary for the
61  * !shared pmd case because we can allocate the pmd later as well, it makes the
62  * code much cleaner. pmd allocation is essential for the shared case because
63  * pud has to be populated inside the same i_mmap_mutex section - otherwise
64  * racing tasks could either miss the sharing (see huge_pte_offset) or select a
65  * bad pmd for sharing.
66  */
67 static pte_t *
68 huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
69 {
70 	struct vm_area_struct *vma = find_vma(mm, addr);
71 	struct address_space *mapping = vma->vm_file->f_mapping;
72 	pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
73 			vma->vm_pgoff;
74 	struct vm_area_struct *svma;
75 	unsigned long saddr;
76 	pte_t *spte = NULL;
77 	pte_t *pte;
78 
79 	if (!vma_shareable(vma, addr))
80 		return (pte_t *)pmd_alloc(mm, pud, addr);
81 
82 	mutex_lock(&mapping->i_mmap_mutex);
83 	vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
84 		if (svma == vma)
85 			continue;
86 
87 		saddr = page_table_shareable(svma, vma, addr, idx);
88 		if (saddr) {
89 			spte = huge_pte_offset(svma->vm_mm, saddr);
90 			if (spte) {
91 				get_page(virt_to_page(spte));
92 				break;
93 			}
94 		}
95 	}
96 
97 	if (!spte)
98 		goto out;
99 
100 	spin_lock(&mm->page_table_lock);
101 	if (pud_none(*pud))
102 		pud_populate(mm, pud, (pmd_t *)((unsigned long)spte & PAGE_MASK));
103 	else
104 		put_page(virt_to_page(spte));
105 	spin_unlock(&mm->page_table_lock);
106 out:
107 	pte = (pte_t *)pmd_alloc(mm, pud, addr);
108 	mutex_unlock(&mapping->i_mmap_mutex);
109 	return pte;
110 }
111 
112 /*
113  * unmap huge page backed by shared pte.
114  *
115  * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
116  * indicated by page_count > 1, unmap is achieved by clearing pud and
117  * decrementing the ref count. If count == 1, the pte page is not shared.
118  *
119  * called with vma->vm_mm->page_table_lock held.
120  *
121  * returns: 1 successfully unmapped a shared pte page
122  *	    0 the underlying pte page is not shared, or it is the last user
123  */
124 int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
125 {
126 	pgd_t *pgd = pgd_offset(mm, *addr);
127 	pud_t *pud = pud_offset(pgd, *addr);
128 
129 	BUG_ON(page_count(virt_to_page(ptep)) == 0);
130 	if (page_count(virt_to_page(ptep)) == 1)
131 		return 0;
132 
133 	pud_clear(pud);
134 	put_page(virt_to_page(ptep));
135 	*addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
136 	return 1;
137 }
138 
139 pte_t *huge_pte_alloc(struct mm_struct *mm,
140 			unsigned long addr, unsigned long sz)
141 {
142 	pgd_t *pgd;
143 	pud_t *pud;
144 	pte_t *pte = NULL;
145 
146 	pgd = pgd_offset(mm, addr);
147 	pud = pud_alloc(mm, pgd, addr);
148 	if (pud) {
149 		if (sz == PUD_SIZE) {
150 			pte = (pte_t *)pud;
151 		} else {
152 			BUG_ON(sz != PMD_SIZE);
153 			if (pud_none(*pud))
154 				pte = huge_pmd_share(mm, addr, pud);
155 			else
156 				pte = (pte_t *)pmd_alloc(mm, pud, addr);
157 		}
158 	}
159 	BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
160 
161 	return pte;
162 }
163 
164 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
165 {
166 	pgd_t *pgd;
167 	pud_t *pud;
168 	pmd_t *pmd = NULL;
169 
170 	pgd = pgd_offset(mm, addr);
171 	if (pgd_present(*pgd)) {
172 		pud = pud_offset(pgd, addr);
173 		if (pud_present(*pud)) {
174 			if (pud_large(*pud))
175 				return (pte_t *)pud;
176 			pmd = pmd_offset(pud, addr);
177 		}
178 	}
179 	return (pte_t *) pmd;
180 }
181 
182 #if 0	/* This is just for testing */
183 struct page *
184 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
185 {
186 	unsigned long start = address;
187 	int length = 1;
188 	int nr;
189 	struct page *page;
190 	struct vm_area_struct *vma;
191 
192 	vma = find_vma(mm, addr);
193 	if (!vma || !is_vm_hugetlb_page(vma))
194 		return ERR_PTR(-EINVAL);
195 
196 	pte = huge_pte_offset(mm, address);
197 
198 	/* hugetlb should be locked, and hence, prefaulted */
199 	WARN_ON(!pte || pte_none(*pte));
200 
201 	page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
202 
203 	WARN_ON(!PageHead(page));
204 
205 	return page;
206 }
207 
208 int pmd_huge(pmd_t pmd)
209 {
210 	return 0;
211 }
212 
213 int pud_huge(pud_t pud)
214 {
215 	return 0;
216 }
217 
218 struct page *
219 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
220 		pmd_t *pmd, int write)
221 {
222 	return NULL;
223 }
224 
225 #else
226 
227 struct page *
228 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
229 {
230 	return ERR_PTR(-EINVAL);
231 }
232 
233 int pmd_huge(pmd_t pmd)
234 {
235 	return !!(pmd_val(pmd) & _PAGE_PSE);
236 }
237 
238 int pud_huge(pud_t pud)
239 {
240 	return !!(pud_val(pud) & _PAGE_PSE);
241 }
242 
243 struct page *
244 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
245 		pmd_t *pmd, int write)
246 {
247 	struct page *page;
248 
249 	page = pte_page(*(pte_t *)pmd);
250 	if (page)
251 		page += ((address & ~PMD_MASK) >> PAGE_SHIFT);
252 	return page;
253 }
254 
255 struct page *
256 follow_huge_pud(struct mm_struct *mm, unsigned long address,
257 		pud_t *pud, int write)
258 {
259 	struct page *page;
260 
261 	page = pte_page(*(pte_t *)pud);
262 	if (page)
263 		page += ((address & ~PUD_MASK) >> PAGE_SHIFT);
264 	return page;
265 }
266 
267 #endif
268 
269 /* x86_64 also uses this file */
270 
271 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
272 static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
273 		unsigned long addr, unsigned long len,
274 		unsigned long pgoff, unsigned long flags)
275 {
276 	struct hstate *h = hstate_file(file);
277 	struct mm_struct *mm = current->mm;
278 	struct vm_area_struct *vma;
279 	unsigned long start_addr;
280 
281 	if (len > mm->cached_hole_size) {
282 	        start_addr = mm->free_area_cache;
283 	} else {
284 	        start_addr = TASK_UNMAPPED_BASE;
285 	        mm->cached_hole_size = 0;
286 	}
287 
288 full_search:
289 	addr = ALIGN(start_addr, huge_page_size(h));
290 
291 	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
292 		/* At this point:  (!vma || addr < vma->vm_end). */
293 		if (TASK_SIZE - len < addr) {
294 			/*
295 			 * Start a new search - just in case we missed
296 			 * some holes.
297 			 */
298 			if (start_addr != TASK_UNMAPPED_BASE) {
299 				start_addr = TASK_UNMAPPED_BASE;
300 				mm->cached_hole_size = 0;
301 				goto full_search;
302 			}
303 			return -ENOMEM;
304 		}
305 		if (!vma || addr + len <= vma->vm_start) {
306 			mm->free_area_cache = addr + len;
307 			return addr;
308 		}
309 		if (addr + mm->cached_hole_size < vma->vm_start)
310 		        mm->cached_hole_size = vma->vm_start - addr;
311 		addr = ALIGN(vma->vm_end, huge_page_size(h));
312 	}
313 }
314 
315 static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
316 		unsigned long addr0, unsigned long len,
317 		unsigned long pgoff, unsigned long flags)
318 {
319 	struct hstate *h = hstate_file(file);
320 	struct mm_struct *mm = current->mm;
321 	struct vm_area_struct *vma;
322 	unsigned long base = mm->mmap_base;
323 	unsigned long addr = addr0;
324 	unsigned long largest_hole = mm->cached_hole_size;
325 	unsigned long start_addr;
326 
327 	/* don't allow allocations above current base */
328 	if (mm->free_area_cache > base)
329 		mm->free_area_cache = base;
330 
331 	if (len <= largest_hole) {
332 	        largest_hole = 0;
333 		mm->free_area_cache  = base;
334 	}
335 try_again:
336 	start_addr = mm->free_area_cache;
337 
338 	/* make sure it can fit in the remaining address space */
339 	if (mm->free_area_cache < len)
340 		goto fail;
341 
342 	/* either no address requested or can't fit in requested address hole */
343 	addr = (mm->free_area_cache - len) & huge_page_mask(h);
344 	do {
345 		/*
346 		 * Lookup failure means no vma is above this address,
347 		 * i.e. return with success:
348 		 */
349 		vma = find_vma(mm, addr);
350 		if (!vma)
351 			return addr;
352 
353 		if (addr + len <= vma->vm_start) {
354 			/* remember the address as a hint for next time */
355 		        mm->cached_hole_size = largest_hole;
356 		        return (mm->free_area_cache = addr);
357 		} else if (mm->free_area_cache == vma->vm_end) {
358 			/* pull free_area_cache down to the first hole */
359 			mm->free_area_cache = vma->vm_start;
360 			mm->cached_hole_size = largest_hole;
361 		}
362 
363 		/* remember the largest hole we saw so far */
364 		if (addr + largest_hole < vma->vm_start)
365 		        largest_hole = vma->vm_start - addr;
366 
367 		/* try just below the current vma->vm_start */
368 		addr = (vma->vm_start - len) & huge_page_mask(h);
369 	} while (len <= vma->vm_start);
370 
371 fail:
372 	/*
373 	 * if hint left us with no space for the requested
374 	 * mapping then try again:
375 	 */
376 	if (start_addr != base) {
377 		mm->free_area_cache = base;
378 		largest_hole = 0;
379 		goto try_again;
380 	}
381 	/*
382 	 * A failed mmap() very likely causes application failure,
383 	 * so fall back to the bottom-up function here. This scenario
384 	 * can happen with large stack limits and large mmap()
385 	 * allocations.
386 	 */
387 	mm->free_area_cache = TASK_UNMAPPED_BASE;
388 	mm->cached_hole_size = ~0UL;
389 	addr = hugetlb_get_unmapped_area_bottomup(file, addr0,
390 			len, pgoff, flags);
391 
392 	/*
393 	 * Restore the topdown base:
394 	 */
395 	mm->free_area_cache = base;
396 	mm->cached_hole_size = ~0UL;
397 
398 	return addr;
399 }
400 
401 unsigned long
402 hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
403 		unsigned long len, unsigned long pgoff, unsigned long flags)
404 {
405 	struct hstate *h = hstate_file(file);
406 	struct mm_struct *mm = current->mm;
407 	struct vm_area_struct *vma;
408 
409 	if (len & ~huge_page_mask(h))
410 		return -EINVAL;
411 	if (len > TASK_SIZE)
412 		return -ENOMEM;
413 
414 	if (flags & MAP_FIXED) {
415 		if (prepare_hugepage_range(file, addr, len))
416 			return -EINVAL;
417 		return addr;
418 	}
419 
420 	if (addr) {
421 		addr = ALIGN(addr, huge_page_size(h));
422 		vma = find_vma(mm, addr);
423 		if (TASK_SIZE - len >= addr &&
424 		    (!vma || addr + len <= vma->vm_start))
425 			return addr;
426 	}
427 	if (mm->get_unmapped_area == arch_get_unmapped_area)
428 		return hugetlb_get_unmapped_area_bottomup(file, addr, len,
429 				pgoff, flags);
430 	else
431 		return hugetlb_get_unmapped_area_topdown(file, addr, len,
432 				pgoff, flags);
433 }
434 
435 #endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/
436 
437 #ifdef CONFIG_X86_64
438 static __init int setup_hugepagesz(char *opt)
439 {
440 	unsigned long ps = memparse(opt, &opt);
441 	if (ps == PMD_SIZE) {
442 		hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
443 	} else if (ps == PUD_SIZE && cpu_has_gbpages) {
444 		hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
445 	} else {
446 		printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
447 			ps >> 20);
448 		return 0;
449 	}
450 	return 1;
451 }
452 __setup("hugepagesz=", setup_hugepagesz);
453 #endif
454