summaryrefslogtreecommitdiffstats
path: root/arch/arm64/kvm/hyp/nvhe/page_alloc.c
blob: d40f0b30b534701d2b35500469e0f79533c9a8c4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2020 Google LLC
 * Author: Quentin Perret <qperret@google.com>
 */

#include <asm/kvm_hyp.h>
#include <nvhe/gfp.h>

u64 __hyp_vmemmap;

/*
 * Index the hyp_vmemmap to find a potential buddy page, but make no assumption
 * about its current state.
 *
 * Example buddy-tree for a 4-pages physically contiguous pool:
 *
 *                 o : Page 3
 *                /
 *               o-o : Page 2
 *              /
 *             /   o : Page 1
 *            /   /
 *           o---o-o : Page 0
 *    Order  2   1 0
 *
 * Example of requests on this pool:
 *   __find_buddy_nocheck(pool, page 0, order 0) => page 1
 *   __find_buddy_nocheck(pool, page 0, order 1) => page 2
 *   __find_buddy_nocheck(pool, page 1, order 0) => page 0
 *   __find_buddy_nocheck(pool, page 2, order 0) => page 3
 */
static struct hyp_page *__find_buddy_nocheck(struct hyp_pool *pool,
					     struct hyp_page *p,
					     unsigned short order)
{
	phys_addr_t addr = hyp_page_to_phys(p);

	addr ^= (PAGE_SIZE << order);

	/*
	 * Don't return a page outside the pool range -- it belongs to
	 * something else and may not be mapped in hyp_vmemmap.
	 */
	if (addr < pool->range_start || addr >= pool->range_end)
		return NULL;

	return hyp_phys_to_page(addr);
}

/* Find a buddy page currently available for allocation */
static struct hyp_page *__find_buddy_avail(struct hyp_pool *pool,
					   struct hyp_page *p,
					   unsigned short order)
{
	struct hyp_page *buddy = __find_buddy_nocheck(pool, p, order);

	if (!buddy || buddy->order != order || buddy->refcount)
		return NULL;

	return buddy;

}

/*
 * Pages that are available for allocation are tracked in free-lists, so we use
 * the pages themselves to store the list nodes to avoid wasting space. As the
 * allocator always returns zeroed pages (which are zeroed on the hyp_put_page()
 * path to optimize allocation speed), we also need to clean-up the list node in
 * each page when we take it out of the list.
 */
static inline void page_remove_from_list(struct hyp_page *p)
{
	struct list_head *node = hyp_page_to_virt(p);

	__list_del_entry(node);
	memset(node, 0, sizeof(*node));
}

static inline void page_add_to_list(struct hyp_page *p, struct list_head *head)
{
	struct list_head *node = hyp_page_to_virt(p);

	INIT_LIST_HEAD(node);
	list_add_tail(node, head);
}

static inline struct hyp_page *node_to_page(struct list_head *node)
{
	return hyp_virt_to_page(node);
}

static void __hyp_attach_page(struct hyp_pool *pool,
			      struct hyp_page *p)
{
	unsigned short order = p->order;
	struct hyp_page *buddy;

	memset(hyp_page_to_virt(p), 0, PAGE_SIZE << p->order);

	/*
	 * Only the first struct hyp_page of a high-order page (otherwise known
	 * as the 'head') should have p->order set. The non-head pages should
	 * have p->order = HYP_NO_ORDER. Here @p may no longer be the head
	 * after coalescing, so make sure to mark it HYP_NO_ORDER proactively.
	 */
	p->order = HYP_NO_ORDER;
	for (; (order + 1) < pool->max_order; order++) {
		buddy = __find_buddy_avail(pool, p, order);
		if (!buddy)
			break;

		/* Take the buddy out of its list, and coalesce with @p */
		page_remove_from_list(buddy);
		buddy->order = HYP_NO_ORDER;
		p = min(p, buddy);
	}

	/* Mark the new head, and insert it */
	p->order = order;
	page_add_to_list(p, &pool->free_area[order]);
}

static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool,
					   struct hyp_page *p,
					   unsigned short order)
{
	struct hyp_page *buddy;

	page_remove_from_list(p);
	while (p->order > order) {
		/*
		 * The buddy of order n - 1 currently has HYP_NO_ORDER as it
		 * is covered by a higher-level page (whose head is @p). Use
		 * __find_buddy_nocheck() to find it and inject it in the
		 * free_list[n - 1], effectively splitting @p in half.
		 */
		p->order--;
		buddy = __find_buddy_nocheck(pool, p, p->order);
		buddy->order = p->order;
		page_add_to_list(buddy, &pool->free_area[buddy->order]);
	}

	return p;
}

static inline void hyp_page_ref_inc(struct hyp_page *p)
{
	BUG_ON(p->refcount == USHRT_MAX);
	p->refcount++;
}

static inline int hyp_page_ref_dec_and_test(struct hyp_page *p)
{
	BUG_ON(!p->refcount);
	p->refcount--;
	return (p->refcount == 0);
}

static inline void hyp_set_page_refcounted(struct hyp_page *p)
{
	BUG_ON(p->refcount);
	p->refcount = 1;
}

static void __hyp_put_page(struct hyp_pool *pool, struct hyp_page *p)
{
	if (hyp_page_ref_dec_and_test(p))
		__hyp_attach_page(pool, p);
}

/*
 * Changes to the buddy tree and page refcounts must be done with the hyp_pool
 * lock held. If a refcount change requires an update to the buddy tree (e.g.
 * hyp_put_page()), both operations must be done within the same critical
 * section to guarantee transient states (e.g. a page with null refcount but
 * not yet attached to a free list) can't be observed by well-behaved readers.
 */
void hyp_put_page(struct hyp_pool *pool, void *addr)
{
	struct hyp_page *p = hyp_virt_to_page(addr);

	hyp_spin_lock(&pool->lock);
	__hyp_put_page(pool, p);
	hyp_spin_unlock(&pool->lock);
}

void hyp_get_page(struct hyp_pool *pool, void *addr)
{
	struct hyp_page *p = hyp_virt_to_page(addr);

	hyp_spin_lock(&pool->lock);
	hyp_page_ref_inc(p);
	hyp_spin_unlock(&pool->lock);
}

void hyp_split_page(struct hyp_page *p)
{
	unsigned short order = p->order;
	unsigned int i;

	p->order = 0;
	for (i = 1; i < (1 << order); i++) {
		struct hyp_page *tail = p + i;

		tail->order = 0;
		hyp_set_page_refcounted(tail);
	}
}

void *hyp_alloc_pages(struct hyp_pool *pool, unsigned short order)
{
	unsigned short i = order;
	struct hyp_page *p;

	hyp_spin_lock(&pool->lock);

	/* Look for a high-enough-order page */
	while (i < pool->max_order && list_empty(&pool->free_area[i]))
		i++;
	if (i >= pool->max_order) {
		hyp_spin_unlock(&pool->lock);
		return NULL;
	}

	/* Extract it from the tree at the right order */
	p = node_to_page(pool->free_area[i].next);
	p = __hyp_extract_page(pool, p, order);

	hyp_set_page_refcounted(p);
	hyp_spin_unlock(&pool->lock);

	return hyp_page_to_virt(p);
}

int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages,
		  unsigned int reserved_pages)
{
	phys_addr_t phys = hyp_pfn_to_phys(pfn);
	struct hyp_page *p;
	int i;

	hyp_spin_lock_init(&pool->lock);
	pool->max_order = min(MAX_ORDER, get_order((nr_pages + 1) << PAGE_SHIFT));
	for (i = 0; i < pool->max_order; i++)
		INIT_LIST_HEAD(&pool->free_area[i]);
	pool->range_start = phys;
	pool->range_end = phys + (nr_pages << PAGE_SHIFT);

	/* Init the vmemmap portion */
	p = hyp_phys_to_page(phys);
	for (i = 0; i < nr_pages; i++) {
		p[i].order = 0;
		hyp_set_page_refcounted(&p[i]);
	}

	/* Attach the unused pages to the buddy tree */
	for (i = reserved_pages; i < nr_pages; i++)
		__hyp_put_page(pool, &p[i]);

	return 0;
}