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 unsigned short 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 unsigned short 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 unsigned short order = p->order; 98 struct hyp_page *buddy; 99 100 memset(hyp_page_to_virt(p), 0, PAGE_SIZE << p->order); 101 102 /* Skip coalescing for 'external' pages being freed into the pool. */ 103 if (phys < pool->range_start || phys >= pool->range_end) 104 goto insert; 105 106 /* 107 * Only the first struct hyp_page of a high-order page (otherwise known 108 * as the 'head') should have p->order set. The non-head pages should 109 * have p->order = HYP_NO_ORDER. Here @p may no longer be the head 110 * after coalescing, so make sure to mark it HYP_NO_ORDER proactively. 111 */ 112 p->order = HYP_NO_ORDER; 113 for (; (order + 1) < pool->max_order; order++) { 114 buddy = __find_buddy_avail(pool, p, order); 115 if (!buddy) 116 break; 117 118 /* Take the buddy out of its list, and coalesce with @p */ 119 page_remove_from_list(buddy); 120 buddy->order = HYP_NO_ORDER; 121 p = min(p, buddy); 122 } 123 124 insert: 125 /* Mark the new head, and insert it */ 126 p->order = order; 127 page_add_to_list(p, &pool->free_area[order]); 128 } 129 130 static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, 131 struct hyp_page *p, 132 unsigned short order) 133 { 134 struct hyp_page *buddy; 135 136 page_remove_from_list(p); 137 while (p->order > order) { 138 /* 139 * The buddy of order n - 1 currently has HYP_NO_ORDER as it 140 * is covered by a higher-level page (whose head is @p). Use 141 * __find_buddy_nocheck() to find it and inject it in the 142 * free_list[n - 1], effectively splitting @p in half. 143 */ 144 p->order--; 145 buddy = __find_buddy_nocheck(pool, p, p->order); 146 buddy->order = p->order; 147 page_add_to_list(buddy, &pool->free_area[buddy->order]); 148 } 149 150 return p; 151 } 152 153 static void __hyp_put_page(struct hyp_pool *pool, struct hyp_page *p) 154 { 155 if (hyp_page_ref_dec_and_test(p)) 156 __hyp_attach_page(pool, p); 157 } 158 159 /* 160 * Changes to the buddy tree and page refcounts must be done with the hyp_pool 161 * lock held. If a refcount change requires an update to the buddy tree (e.g. 162 * hyp_put_page()), both operations must be done within the same critical 163 * section to guarantee transient states (e.g. a page with null refcount but 164 * not yet attached to a free list) can't be observed by well-behaved readers. 165 */ 166 void hyp_put_page(struct hyp_pool *pool, void *addr) 167 { 168 struct hyp_page *p = hyp_virt_to_page(addr); 169 170 hyp_spin_lock(&pool->lock); 171 __hyp_put_page(pool, p); 172 hyp_spin_unlock(&pool->lock); 173 } 174 175 void hyp_get_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_page_ref_inc(p); 181 hyp_spin_unlock(&pool->lock); 182 } 183 184 void hyp_split_page(struct hyp_page *p) 185 { 186 unsigned short order = p->order; 187 unsigned int i; 188 189 p->order = 0; 190 for (i = 1; i < (1 << order); i++) { 191 struct hyp_page *tail = p + i; 192 193 tail->order = 0; 194 hyp_set_page_refcounted(tail); 195 } 196 } 197 198 void *hyp_alloc_pages(struct hyp_pool *pool, unsigned short order) 199 { 200 unsigned short i = order; 201 struct hyp_page *p; 202 203 hyp_spin_lock(&pool->lock); 204 205 /* Look for a high-enough-order page */ 206 while (i < pool->max_order && list_empty(&pool->free_area[i])) 207 i++; 208 if (i >= pool->max_order) { 209 hyp_spin_unlock(&pool->lock); 210 return NULL; 211 } 212 213 /* Extract it from the tree at the right order */ 214 p = node_to_page(pool->free_area[i].next); 215 p = __hyp_extract_page(pool, p, order); 216 217 hyp_set_page_refcounted(p); 218 hyp_spin_unlock(&pool->lock); 219 220 return hyp_page_to_virt(p); 221 } 222 223 int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages, 224 unsigned int reserved_pages) 225 { 226 phys_addr_t phys = hyp_pfn_to_phys(pfn); 227 struct hyp_page *p; 228 int i; 229 230 hyp_spin_lock_init(&pool->lock); 231 pool->max_order = min(MAX_ORDER, get_order((nr_pages + 1) << PAGE_SHIFT)); 232 for (i = 0; i < pool->max_order; i++) 233 INIT_LIST_HEAD(&pool->free_area[i]); 234 pool->range_start = phys; 235 pool->range_end = phys + (nr_pages << PAGE_SHIFT); 236 237 /* Init the vmemmap portion */ 238 p = hyp_phys_to_page(phys); 239 for (i = 0; i < nr_pages; i++) 240 hyp_set_page_refcounted(&p[i]); 241 242 /* Attach the unused pages to the buddy tree */ 243 for (i = reserved_pages; i < nr_pages; i++) 244 __hyp_put_page(pool, &p[i]); 245 246 return 0; 247 } 248