xref: /kernel/linux/linux-5.10/arch/s390/mm/pgalloc.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  Page table allocation functions
4 *
5 *    Copyright IBM Corp. 2016
6 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
7 */
8
9#include <linux/sysctl.h>
10#include <linux/slab.h>
11#include <linux/mm.h>
12#include <asm/mmu_context.h>
13#include <asm/pgalloc.h>
14#include <asm/gmap.h>
15#include <asm/tlb.h>
16#include <asm/tlbflush.h>
17
18#ifdef CONFIG_PGSTE
19
20int page_table_allocate_pgste = 0;
21EXPORT_SYMBOL(page_table_allocate_pgste);
22
23static struct ctl_table page_table_sysctl[] = {
24	{
25		.procname	= "allocate_pgste",
26		.data		= &page_table_allocate_pgste,
27		.maxlen		= sizeof(int),
28		.mode		= S_IRUGO | S_IWUSR,
29		.proc_handler	= proc_dointvec_minmax,
30		.extra1		= SYSCTL_ZERO,
31		.extra2		= SYSCTL_ONE,
32	},
33	{ }
34};
35
36static struct ctl_table page_table_sysctl_dir[] = {
37	{
38		.procname	= "vm",
39		.maxlen		= 0,
40		.mode		= 0555,
41		.child		= page_table_sysctl,
42	},
43	{ }
44};
45
46static int __init page_table_register_sysctl(void)
47{
48	return register_sysctl_table(page_table_sysctl_dir) ? 0 : -ENOMEM;
49}
50__initcall(page_table_register_sysctl);
51
52#endif /* CONFIG_PGSTE */
53
54unsigned long *crst_table_alloc(struct mm_struct *mm)
55{
56	struct page *page = alloc_pages(GFP_KERNEL, 2);
57
58	if (!page)
59		return NULL;
60	arch_set_page_dat(page, 2);
61	return (unsigned long *) page_to_phys(page);
62}
63
64void crst_table_free(struct mm_struct *mm, unsigned long *table)
65{
66	free_pages((unsigned long) table, 2);
67}
68
69static void __crst_table_upgrade(void *arg)
70{
71	struct mm_struct *mm = arg;
72
73	/* we must change all active ASCEs to avoid the creation of new TLBs */
74	if (current->active_mm == mm) {
75		S390_lowcore.user_asce = mm->context.asce;
76		if (current->thread.mm_segment == USER_DS) {
77			__ctl_load(S390_lowcore.user_asce, 1, 1);
78			/* Mark user-ASCE present in CR1 */
79			clear_cpu_flag(CIF_ASCE_PRIMARY);
80		}
81		if (current->thread.mm_segment == USER_DS_SACF) {
82			__ctl_load(S390_lowcore.user_asce, 7, 7);
83			/* enable_sacf_uaccess does all or nothing */
84			WARN_ON(!test_cpu_flag(CIF_ASCE_SECONDARY));
85		}
86	}
87	__tlb_flush_local();
88}
89
90int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
91{
92	unsigned long *pgd = NULL, *p4d = NULL, *__pgd;
93	unsigned long asce_limit = mm->context.asce_limit;
94
95	/* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */
96	VM_BUG_ON(asce_limit < _REGION2_SIZE);
97
98	if (end <= asce_limit)
99		return 0;
100
101	if (asce_limit == _REGION2_SIZE) {
102		p4d = crst_table_alloc(mm);
103		if (unlikely(!p4d))
104			goto err_p4d;
105		crst_table_init(p4d, _REGION2_ENTRY_EMPTY);
106	}
107	if (end > _REGION1_SIZE) {
108		pgd = crst_table_alloc(mm);
109		if (unlikely(!pgd))
110			goto err_pgd;
111		crst_table_init(pgd, _REGION1_ENTRY_EMPTY);
112	}
113
114	spin_lock_bh(&mm->page_table_lock);
115
116	/*
117	 * This routine gets called with mmap_lock lock held and there is
118	 * no reason to optimize for the case of otherwise. However, if
119	 * that would ever change, the below check will let us know.
120	 */
121	VM_BUG_ON(asce_limit != mm->context.asce_limit);
122
123	if (p4d) {
124		__pgd = (unsigned long *) mm->pgd;
125		p4d_populate(mm, (p4d_t *) p4d, (pud_t *) __pgd);
126		mm->pgd = (pgd_t *) p4d;
127		mm->context.asce_limit = _REGION1_SIZE;
128		mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
129			_ASCE_USER_BITS | _ASCE_TYPE_REGION2;
130		mm_inc_nr_puds(mm);
131	}
132	if (pgd) {
133		__pgd = (unsigned long *) mm->pgd;
134		pgd_populate(mm, (pgd_t *) pgd, (p4d_t *) __pgd);
135		mm->pgd = (pgd_t *) pgd;
136		mm->context.asce_limit = TASK_SIZE_MAX;
137		mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
138			_ASCE_USER_BITS | _ASCE_TYPE_REGION1;
139	}
140
141	spin_unlock_bh(&mm->page_table_lock);
142
143	on_each_cpu(__crst_table_upgrade, mm, 0);
144
145	return 0;
146
147err_pgd:
148	crst_table_free(mm, p4d);
149err_p4d:
150	return -ENOMEM;
151}
152
153static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
154{
155	unsigned int old, new;
156
157	do {
158		old = atomic_read(v);
159		new = old ^ bits;
160	} while (atomic_cmpxchg(v, old, new) != old);
161	return new;
162}
163
164#ifdef CONFIG_PGSTE
165
166struct page *page_table_alloc_pgste(struct mm_struct *mm)
167{
168	struct page *page;
169	u64 *table;
170
171	page = alloc_page(GFP_KERNEL);
172	if (page) {
173		table = (u64 *)page_to_phys(page);
174		memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
175		memset64(table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
176	}
177	return page;
178}
179
180void page_table_free_pgste(struct page *page)
181{
182	__free_page(page);
183}
184
185#endif /* CONFIG_PGSTE */
186
187/*
188 * page table entry allocation/free routines.
189 */
190unsigned long *page_table_alloc(struct mm_struct *mm)
191{
192	unsigned long *table;
193	struct page *page;
194	unsigned int mask, bit;
195
196	/* Try to get a fragment of a 4K page as a 2K page table */
197	if (!mm_alloc_pgste(mm)) {
198		table = NULL;
199		spin_lock_bh(&mm->context.lock);
200		if (!list_empty(&mm->context.pgtable_list)) {
201			page = list_first_entry(&mm->context.pgtable_list,
202						struct page, lru);
203			mask = atomic_read(&page->_refcount) >> 24;
204			mask = (mask | (mask >> 4)) & 3;
205			if (mask != 3) {
206				table = (unsigned long *) page_to_phys(page);
207				bit = mask & 1;		/* =1 -> second 2K */
208				if (bit)
209					table += PTRS_PER_PTE;
210				atomic_xor_bits(&page->_refcount,
211							1U << (bit + 24));
212				list_del(&page->lru);
213			}
214		}
215		spin_unlock_bh(&mm->context.lock);
216		if (table)
217			return table;
218	}
219	/* Allocate a fresh page */
220	page = alloc_page(GFP_KERNEL);
221	if (!page)
222		return NULL;
223	if (!pgtable_pte_page_ctor(page)) {
224		__free_page(page);
225		return NULL;
226	}
227	arch_set_page_dat(page, 0);
228	/* Initialize page table */
229	table = (unsigned long *) page_to_phys(page);
230	if (mm_alloc_pgste(mm)) {
231		/* Return 4K page table with PGSTEs */
232		atomic_xor_bits(&page->_refcount, 3 << 24);
233		memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
234		memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
235	} else {
236		/* Return the first 2K fragment of the page */
237		atomic_xor_bits(&page->_refcount, 1 << 24);
238		memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE);
239		spin_lock_bh(&mm->context.lock);
240		list_add(&page->lru, &mm->context.pgtable_list);
241		spin_unlock_bh(&mm->context.lock);
242	}
243	return table;
244}
245
246void page_table_free(struct mm_struct *mm, unsigned long *table)
247{
248	struct page *page;
249	unsigned int bit, mask;
250
251	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
252	if (!mm_alloc_pgste(mm)) {
253		/* Free 2K page table fragment of a 4K page */
254		bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
255		spin_lock_bh(&mm->context.lock);
256		mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
257		mask >>= 24;
258		if (mask & 3)
259			list_add(&page->lru, &mm->context.pgtable_list);
260		else
261			list_del(&page->lru);
262		spin_unlock_bh(&mm->context.lock);
263		mask = atomic_xor_bits(&page->_refcount, 0x10U << (bit + 24));
264		mask >>= 24;
265		if (mask != 0)
266			return;
267	} else {
268		atomic_xor_bits(&page->_refcount, 3U << 24);
269	}
270
271	pgtable_pte_page_dtor(page);
272	__free_page(page);
273}
274
275void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
276			 unsigned long vmaddr)
277{
278	struct mm_struct *mm;
279	struct page *page;
280	unsigned int bit, mask;
281
282	mm = tlb->mm;
283	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
284	if (mm_alloc_pgste(mm)) {
285		gmap_unlink(mm, table, vmaddr);
286		table = (unsigned long *) (__pa(table) | 3);
287		tlb_remove_table(tlb, table);
288		return;
289	}
290	bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
291	spin_lock_bh(&mm->context.lock);
292	mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
293	mask >>= 24;
294	if (mask & 3)
295		list_add_tail(&page->lru, &mm->context.pgtable_list);
296	else
297		list_del(&page->lru);
298	spin_unlock_bh(&mm->context.lock);
299	table = (unsigned long *) (__pa(table) | (1U << bit));
300	tlb_remove_table(tlb, table);
301}
302
303void __tlb_remove_table(void *_table)
304{
305	unsigned int mask = (unsigned long) _table & 3;
306	void *table = (void *)((unsigned long) _table ^ mask);
307	struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
308
309	switch (mask) {
310	case 0:		/* pmd, pud, or p4d */
311		free_pages((unsigned long) table, 2);
312		break;
313	case 1:		/* lower 2K of a 4K page table */
314	case 2:		/* higher 2K of a 4K page table */
315		mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24));
316		mask >>= 24;
317		if (mask != 0)
318			break;
319		fallthrough;
320	case 3:		/* 4K page table with pgstes */
321		if (mask & 3)
322			atomic_xor_bits(&page->_refcount, 3 << 24);
323		pgtable_pte_page_dtor(page);
324		__free_page(page);
325		break;
326	}
327}
328
329/*
330 * Base infrastructure required to generate basic asces, region, segment,
331 * and page tables that do not make use of enhanced features like EDAT1.
332 */
333
334static struct kmem_cache *base_pgt_cache;
335
336static unsigned long base_pgt_alloc(void)
337{
338	u64 *table;
339
340	table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
341	if (table)
342		memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
343	return (unsigned long) table;
344}
345
346static void base_pgt_free(unsigned long table)
347{
348	kmem_cache_free(base_pgt_cache, (void *) table);
349}
350
351static unsigned long base_crst_alloc(unsigned long val)
352{
353	unsigned long table;
354
355	table =	 __get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
356	if (table)
357		crst_table_init((unsigned long *)table, val);
358	return table;
359}
360
361static void base_crst_free(unsigned long table)
362{
363	free_pages(table, CRST_ALLOC_ORDER);
364}
365
366#define BASE_ADDR_END_FUNC(NAME, SIZE)					\
367static inline unsigned long base_##NAME##_addr_end(unsigned long addr,	\
368						   unsigned long end)	\
369{									\
370	unsigned long next = (addr + (SIZE)) & ~((SIZE) - 1);		\
371									\
372	return (next - 1) < (end - 1) ? next : end;			\
373}
374
375BASE_ADDR_END_FUNC(page,    _PAGE_SIZE)
376BASE_ADDR_END_FUNC(segment, _SEGMENT_SIZE)
377BASE_ADDR_END_FUNC(region3, _REGION3_SIZE)
378BASE_ADDR_END_FUNC(region2, _REGION2_SIZE)
379BASE_ADDR_END_FUNC(region1, _REGION1_SIZE)
380
381static inline unsigned long base_lra(unsigned long address)
382{
383	unsigned long real;
384
385	asm volatile(
386		"	lra	%0,0(%1)\n"
387		: "=d" (real) : "a" (address) : "cc");
388	return real;
389}
390
391static int base_page_walk(unsigned long origin, unsigned long addr,
392			  unsigned long end, int alloc)
393{
394	unsigned long *pte, next;
395
396	if (!alloc)
397		return 0;
398	pte = (unsigned long *) origin;
399	pte += (addr & _PAGE_INDEX) >> _PAGE_SHIFT;
400	do {
401		next = base_page_addr_end(addr, end);
402		*pte = base_lra(addr);
403	} while (pte++, addr = next, addr < end);
404	return 0;
405}
406
407static int base_segment_walk(unsigned long origin, unsigned long addr,
408			     unsigned long end, int alloc)
409{
410	unsigned long *ste, next, table;
411	int rc;
412
413	ste = (unsigned long *) origin;
414	ste += (addr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
415	do {
416		next = base_segment_addr_end(addr, end);
417		if (*ste & _SEGMENT_ENTRY_INVALID) {
418			if (!alloc)
419				continue;
420			table = base_pgt_alloc();
421			if (!table)
422				return -ENOMEM;
423			*ste = table | _SEGMENT_ENTRY;
424		}
425		table = *ste & _SEGMENT_ENTRY_ORIGIN;
426		rc = base_page_walk(table, addr, next, alloc);
427		if (rc)
428			return rc;
429		if (!alloc)
430			base_pgt_free(table);
431		cond_resched();
432	} while (ste++, addr = next, addr < end);
433	return 0;
434}
435
436static int base_region3_walk(unsigned long origin, unsigned long addr,
437			     unsigned long end, int alloc)
438{
439	unsigned long *rtte, next, table;
440	int rc;
441
442	rtte = (unsigned long *) origin;
443	rtte += (addr & _REGION3_INDEX) >> _REGION3_SHIFT;
444	do {
445		next = base_region3_addr_end(addr, end);
446		if (*rtte & _REGION_ENTRY_INVALID) {
447			if (!alloc)
448				continue;
449			table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
450			if (!table)
451				return -ENOMEM;
452			*rtte = table | _REGION3_ENTRY;
453		}
454		table = *rtte & _REGION_ENTRY_ORIGIN;
455		rc = base_segment_walk(table, addr, next, alloc);
456		if (rc)
457			return rc;
458		if (!alloc)
459			base_crst_free(table);
460	} while (rtte++, addr = next, addr < end);
461	return 0;
462}
463
464static int base_region2_walk(unsigned long origin, unsigned long addr,
465			     unsigned long end, int alloc)
466{
467	unsigned long *rste, next, table;
468	int rc;
469
470	rste = (unsigned long *) origin;
471	rste += (addr & _REGION2_INDEX) >> _REGION2_SHIFT;
472	do {
473		next = base_region2_addr_end(addr, end);
474		if (*rste & _REGION_ENTRY_INVALID) {
475			if (!alloc)
476				continue;
477			table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
478			if (!table)
479				return -ENOMEM;
480			*rste = table | _REGION2_ENTRY;
481		}
482		table = *rste & _REGION_ENTRY_ORIGIN;
483		rc = base_region3_walk(table, addr, next, alloc);
484		if (rc)
485			return rc;
486		if (!alloc)
487			base_crst_free(table);
488	} while (rste++, addr = next, addr < end);
489	return 0;
490}
491
492static int base_region1_walk(unsigned long origin, unsigned long addr,
493			     unsigned long end, int alloc)
494{
495	unsigned long *rfte, next, table;
496	int rc;
497
498	rfte = (unsigned long *) origin;
499	rfte += (addr & _REGION1_INDEX) >> _REGION1_SHIFT;
500	do {
501		next = base_region1_addr_end(addr, end);
502		if (*rfte & _REGION_ENTRY_INVALID) {
503			if (!alloc)
504				continue;
505			table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
506			if (!table)
507				return -ENOMEM;
508			*rfte = table | _REGION1_ENTRY;
509		}
510		table = *rfte & _REGION_ENTRY_ORIGIN;
511		rc = base_region2_walk(table, addr, next, alloc);
512		if (rc)
513			return rc;
514		if (!alloc)
515			base_crst_free(table);
516	} while (rfte++, addr = next, addr < end);
517	return 0;
518}
519
520/**
521 * base_asce_free - free asce and tables returned from base_asce_alloc()
522 * @asce: asce to be freed
523 *
524 * Frees all region, segment, and page tables that were allocated with a
525 * corresponding base_asce_alloc() call.
526 */
527void base_asce_free(unsigned long asce)
528{
529	unsigned long table = asce & _ASCE_ORIGIN;
530
531	if (!asce)
532		return;
533	switch (asce & _ASCE_TYPE_MASK) {
534	case _ASCE_TYPE_SEGMENT:
535		base_segment_walk(table, 0, _REGION3_SIZE, 0);
536		break;
537	case _ASCE_TYPE_REGION3:
538		base_region3_walk(table, 0, _REGION2_SIZE, 0);
539		break;
540	case _ASCE_TYPE_REGION2:
541		base_region2_walk(table, 0, _REGION1_SIZE, 0);
542		break;
543	case _ASCE_TYPE_REGION1:
544		base_region1_walk(table, 0, TASK_SIZE_MAX, 0);
545		break;
546	}
547	base_crst_free(table);
548}
549
550static int base_pgt_cache_init(void)
551{
552	static DEFINE_MUTEX(base_pgt_cache_mutex);
553	unsigned long sz = _PAGE_TABLE_SIZE;
554
555	if (base_pgt_cache)
556		return 0;
557	mutex_lock(&base_pgt_cache_mutex);
558	if (!base_pgt_cache)
559		base_pgt_cache = kmem_cache_create("base_pgt", sz, sz, 0, NULL);
560	mutex_unlock(&base_pgt_cache_mutex);
561	return base_pgt_cache ? 0 : -ENOMEM;
562}
563
564/**
565 * base_asce_alloc - create kernel mapping without enhanced DAT features
566 * @addr: virtual start address of kernel mapping
567 * @num_pages: number of consecutive pages
568 *
569 * Generate an asce, including all required region, segment and page tables,
570 * that can be used to access the virtual kernel mapping. The difference is
571 * that the returned asce does not make use of any enhanced DAT features like
572 * e.g. large pages. This is required for some I/O functions that pass an
573 * asce, like e.g. some service call requests.
574 *
575 * Note: the returned asce may NEVER be attached to any cpu. It may only be
576 *	 used for I/O requests. tlb entries that might result because the
577 *	 asce was attached to a cpu won't be cleared.
578 */
579unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
580{
581	unsigned long asce, table, end;
582	int rc;
583
584	if (base_pgt_cache_init())
585		return 0;
586	end = addr + num_pages * PAGE_SIZE;
587	if (end <= _REGION3_SIZE) {
588		table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
589		if (!table)
590			return 0;
591		rc = base_segment_walk(table, addr, end, 1);
592		asce = table | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
593	} else if (end <= _REGION2_SIZE) {
594		table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
595		if (!table)
596			return 0;
597		rc = base_region3_walk(table, addr, end, 1);
598		asce = table | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
599	} else if (end <= _REGION1_SIZE) {
600		table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
601		if (!table)
602			return 0;
603		rc = base_region2_walk(table, addr, end, 1);
604		asce = table | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
605	} else {
606		table = base_crst_alloc(_REGION1_ENTRY_EMPTY);
607		if (!table)
608			return 0;
609		rc = base_region1_walk(table, addr, end, 1);
610		asce = table | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
611	}
612	if (rc) {
613		base_asce_free(asce);
614		asce = 0;
615	}
616	return asce;
617}
618