1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2020 Google LLC 4 * Author: Quentin Perret <qperret@google.com> 5 */ 6 7 #include <asm/kvm_hyp.h> 8 #include <nvhe/gfp.h> 9 10 u64 __hyp_vmemmap; 11 12 /* 13 * Index the hyp_vmemmap to find a potential buddy page, but make no assumption 14 * about its current state. 15 * 16 * Example buddy-tree for a 4-pages physically contiguous pool: 17 * 18 * o : Page 3 19 * / 20 * o-o : Page 2 21 * / 22 * / o : Page 1 23 * / / 24 * o---o-o : Page 0 25 * Order 2 1 0 26 * 27 * Example of requests on this pool: 28 * __find_buddy_nocheck(pool, page 0, order 0) => page 1 29 * __find_buddy_nocheck(pool, page 0, order 1) => page 2 30 * __find_buddy_nocheck(pool, page 1, order 0) => page 0 31 * __find_buddy_nocheck(pool, page 2, order 0) => page 3 32 */ 33 static struct hyp_page *__find_buddy_nocheck(struct hyp_pool *pool, 34 struct hyp_page *p, 35 u8 order) 36 { 37 phys_addr_t addr = hyp_page_to_phys(p); 38 39 addr ^= (PAGE_SIZE << order); 40 41 /* 42 * Don't return a page outside the pool range -- it belongs to 43 * something else and may not be mapped in hyp_vmemmap. 44 */ 45 if (addr < pool->range_start || addr >= pool->range_end) 46 return NULL; 47 48 return hyp_phys_to_page(addr); 49 } 50 51 /* Find a buddy page currently available for allocation */ 52 static struct hyp_page *__find_buddy_avail(struct hyp_pool *pool, 53 struct hyp_page *p, 54 u8 order) 55 { 56 struct hyp_page *buddy = __find_buddy_nocheck(pool, p, order); 57 58 if (!buddy || buddy->order != order || buddy->refcount) 59 return NULL; 60 61 return buddy; 62 63 } 64 65 /* 66 * Pages that are available for allocation are tracked in free-lists, so we use 67 * the pages themselves to store the list nodes to avoid wasting space. As the 68 * allocator always returns zeroed pages (which are zeroed on the hyp_put_page() 69 * path to optimize allocation speed), we also need to clean-up the list node in 70 * each page when we take it out of the list. 71 */ 72 static inline void page_remove_from_list(struct hyp_page *p) 73 { 74 struct list_head *node = hyp_page_to_virt(p); 75 76 __list_del_entry(node); 77 memset(node, 0, sizeof(*node)); 78 } 79 80 static inline void page_add_to_list(struct hyp_page *p, struct list_head *head) 81 { 82 struct list_head *node = hyp_page_to_virt(p); 83 84 INIT_LIST_HEAD(node); 85 list_add_tail(node, head); 86 } 87 88 static inline struct hyp_page *node_to_page(struct list_head *node) 89 { 90 return hyp_virt_to_page(node); 91 } 92 93 static void __hyp_attach_page(struct hyp_pool *pool, 94 struct hyp_page *p) 95 { 96 phys_addr_t phys = hyp_page_to_phys(p); 97 struct hyp_page *buddy; 98 bool coalesce = true; 99 u8 order = p->order; 100 101 /* 102 * 'external' pages are never coalesced and their ->order field 103 * untrusted as they bypass hyp_pool_init(). Enforce order-0. 104 */ 105 if (phys < pool->range_start || phys >= pool->range_end) { 106 order = 0; 107 coalesce = false; 108 } 109 110 memset(hyp_page_to_virt(p), 0, PAGE_SIZE << order); 111 112 if (!coalesce) 113 goto insert; 114 115 /* 116 * Only the first struct hyp_page of a high-order page (otherwise known 117 * as the 'head') should have p->order set. The non-head pages should 118 * have p->order = HYP_NO_ORDER. Here @p may no longer be the head 119 * after coalescing, so make sure to mark it HYP_NO_ORDER proactively. 120 */ 121 p->order = HYP_NO_ORDER; 122 for (; (order + 1) <= pool->max_order; order++) { 123 buddy = __find_buddy_avail(pool, p, order); 124 if (!buddy) 125 break; 126 127 /* Take the buddy out of its list, and coalesce with @p */ 128 page_remove_from_list(buddy); 129 buddy->order = HYP_NO_ORDER; 130 p = min(p, buddy); 131 } 132 133 insert: 134 /* Mark the new head, and insert it */ 135 p->order = order; 136 page_add_to_list(p, &pool->free_area[order]); 137 } 138 139 static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, 140 struct hyp_page *p, 141 u8 order) 142 { 143 struct hyp_page *buddy; 144 145 page_remove_from_list(p); 146 while (p->order > order) { 147 /* 148 * The buddy of order n - 1 currently has HYP_NO_ORDER as it 149 * is covered by a higher-level page (whose head is @p). Use 150 * __find_buddy_nocheck() to find it and inject it in the 151 * free_list[n - 1], effectively splitting @p in half. 152 */ 153 p->order--; 154 buddy = __find_buddy_nocheck(pool, p, p->order); 155 buddy->order = p->order; 156 page_add_to_list(buddy, &pool->free_area[buddy->order]); 157 } 158 159 return p; 160 } 161 162 static void __hyp_put_page(struct hyp_pool *pool, struct hyp_page *p) 163 { 164 if (hyp_page_ref_dec_and_test(p)) 165 __hyp_attach_page(pool, p); 166 } 167 168 /* 169 * Changes to the buddy tree and page refcounts must be done with the hyp_pool 170 * lock held. If a refcount change requires an update to the buddy tree (e.g. 171 * hyp_put_page()), both operations must be done within the same critical 172 * section to guarantee transient states (e.g. a page with null refcount but 173 * not yet attached to a free list) can't be observed by well-behaved readers. 174 */ 175 void hyp_put_page(struct hyp_pool *pool, void *addr) 176 { 177 struct hyp_page *p = hyp_virt_to_page(addr); 178 179 hyp_spin_lock(&pool->lock); 180 __hyp_put_page(pool, p); 181 hyp_spin_unlock(&pool->lock); 182 } 183 184 void hyp_get_page(struct hyp_pool *pool, void *addr) 185 { 186 struct hyp_page *p = hyp_virt_to_page(addr); 187 188 hyp_spin_lock(&pool->lock); 189 hyp_page_ref_inc(p); 190 hyp_spin_unlock(&pool->lock); 191 } 192 193 void hyp_split_page(struct hyp_page *p) 194 { 195 u8 order = p->order; 196 unsigned int i; 197 198 p->order = 0; 199 for (i = 1; i < (1 << order); i++) { 200 struct hyp_page *tail = p + i; 201 202 tail->order = 0; 203 hyp_set_page_refcounted(tail); 204 } 205 } 206 207 void *hyp_alloc_pages(struct hyp_pool *pool, u8 order) 208 { 209 struct hyp_page *p; 210 u8 i = order; 211 212 hyp_spin_lock(&pool->lock); 213 214 /* Look for a high-enough-order page */ 215 while (i <= pool->max_order && list_empty(&pool->free_area[i])) 216 i++; 217 if (i > pool->max_order) { 218 hyp_spin_unlock(&pool->lock); 219 return NULL; 220 } 221 222 /* Extract it from the tree at the right order */ 223 p = node_to_page(pool->free_area[i].next); 224 p = __hyp_extract_page(pool, p, order); 225 226 hyp_set_page_refcounted(p); 227 hyp_spin_unlock(&pool->lock); 228 229 return hyp_page_to_virt(p); 230 } 231 232 int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages, 233 unsigned int reserved_pages) 234 { 235 phys_addr_t phys = hyp_pfn_to_phys(pfn); 236 struct hyp_page *p; 237 int i; 238 239 hyp_spin_lock_init(&pool->lock); 240 pool->max_order = min(MAX_PAGE_ORDER, 241 get_order(nr_pages << PAGE_SHIFT)); 242 for (i = 0; i <= pool->max_order; i++) 243 INIT_LIST_HEAD(&pool->free_area[i]); 244 pool->range_start = phys; 245 pool->range_end = phys + (nr_pages << PAGE_SHIFT); 246 247 /* Init the vmemmap portion */ 248 p = hyp_phys_to_page(phys); 249 for (i = 0; i < nr_pages; i++) { 250 hyp_set_page_refcounted(&p[i]); 251 p[i].order = 0; 252 } 253 254 /* Attach the unused pages to the buddy tree */ 255 for (i = reserved_pages; i < nr_pages; i++) 256 __hyp_put_page(pool, &p[i]); 257 258 return 0; 259 } 260