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 int 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 int 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 static void __hyp_attach_page(struct hyp_pool *pool, 66 struct hyp_page *p) 67 { 68 unsigned int order = p->order; 69 struct hyp_page *buddy; 70 71 memset(hyp_page_to_virt(p), 0, PAGE_SIZE << p->order); 72 73 /* 74 * Only the first struct hyp_page of a high-order page (otherwise known 75 * as the 'head') should have p->order set. The non-head pages should 76 * have p->order = HYP_NO_ORDER. Here @p may no longer be the head 77 * after coallescing, so make sure to mark it HYP_NO_ORDER proactively. 78 */ 79 p->order = HYP_NO_ORDER; 80 for (; (order + 1) < pool->max_order; order++) { 81 buddy = __find_buddy_avail(pool, p, order); 82 if (!buddy) 83 break; 84 85 /* Take the buddy out of its list, and coallesce with @p */ 86 list_del_init(&buddy->node); 87 buddy->order = HYP_NO_ORDER; 88 p = min(p, buddy); 89 } 90 91 /* Mark the new head, and insert it */ 92 p->order = order; 93 list_add_tail(&p->node, &pool->free_area[order]); 94 } 95 96 static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, 97 struct hyp_page *p, 98 unsigned int order) 99 { 100 struct hyp_page *buddy; 101 102 list_del_init(&p->node); 103 while (p->order > order) { 104 /* 105 * The buddy of order n - 1 currently has HYP_NO_ORDER as it 106 * is covered by a higher-level page (whose head is @p). Use 107 * __find_buddy_nocheck() to find it and inject it in the 108 * free_list[n - 1], effectively splitting @p in half. 109 */ 110 p->order--; 111 buddy = __find_buddy_nocheck(pool, p, p->order); 112 buddy->order = p->order; 113 list_add_tail(&buddy->node, &pool->free_area[buddy->order]); 114 } 115 116 return p; 117 } 118 119 static inline void hyp_page_ref_inc(struct hyp_page *p) 120 { 121 p->refcount++; 122 } 123 124 static inline int hyp_page_ref_dec_and_test(struct hyp_page *p) 125 { 126 p->refcount--; 127 return (p->refcount == 0); 128 } 129 130 static inline void hyp_set_page_refcounted(struct hyp_page *p) 131 { 132 BUG_ON(p->refcount); 133 p->refcount = 1; 134 } 135 136 static void __hyp_put_page(struct hyp_pool *pool, struct hyp_page *p) 137 { 138 if (hyp_page_ref_dec_and_test(p)) 139 __hyp_attach_page(pool, p); 140 } 141 142 /* 143 * Changes to the buddy tree and page refcounts must be done with the hyp_pool 144 * lock held. If a refcount change requires an update to the buddy tree (e.g. 145 * hyp_put_page()), both operations must be done within the same critical 146 * section to guarantee transient states (e.g. a page with null refcount but 147 * not yet attached to a free list) can't be observed by well-behaved readers. 148 */ 149 void hyp_put_page(void *addr) 150 { 151 struct hyp_page *p = hyp_virt_to_page(addr); 152 struct hyp_pool *pool = hyp_page_to_pool(p); 153 154 hyp_spin_lock(&pool->lock); 155 __hyp_put_page(pool, p); 156 hyp_spin_unlock(&pool->lock); 157 } 158 159 void hyp_get_page(void *addr) 160 { 161 struct hyp_page *p = hyp_virt_to_page(addr); 162 struct hyp_pool *pool = hyp_page_to_pool(p); 163 164 hyp_spin_lock(&pool->lock); 165 hyp_page_ref_inc(p); 166 hyp_spin_unlock(&pool->lock); 167 } 168 169 void *hyp_alloc_pages(struct hyp_pool *pool, unsigned int order) 170 { 171 unsigned int i = order; 172 struct hyp_page *p; 173 174 hyp_spin_lock(&pool->lock); 175 176 /* Look for a high-enough-order page */ 177 while (i < pool->max_order && list_empty(&pool->free_area[i])) 178 i++; 179 if (i >= pool->max_order) { 180 hyp_spin_unlock(&pool->lock); 181 return NULL; 182 } 183 184 /* Extract it from the tree at the right order */ 185 p = list_first_entry(&pool->free_area[i], struct hyp_page, node); 186 p = __hyp_extract_page(pool, p, order); 187 188 hyp_set_page_refcounted(p); 189 hyp_spin_unlock(&pool->lock); 190 191 return hyp_page_to_virt(p); 192 } 193 194 int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages, 195 unsigned int reserved_pages) 196 { 197 phys_addr_t phys = hyp_pfn_to_phys(pfn); 198 struct hyp_page *p; 199 int i; 200 201 hyp_spin_lock_init(&pool->lock); 202 pool->max_order = min(MAX_ORDER, get_order(nr_pages << PAGE_SHIFT)); 203 for (i = 0; i < pool->max_order; i++) 204 INIT_LIST_HEAD(&pool->free_area[i]); 205 pool->range_start = phys; 206 pool->range_end = phys + (nr_pages << PAGE_SHIFT); 207 208 /* Init the vmemmap portion */ 209 p = hyp_phys_to_page(phys); 210 for (i = 0; i < nr_pages; i++) { 211 p[i].pool = pool; 212 p[i].order = 0; 213 INIT_LIST_HEAD(&p[i].node); 214 hyp_set_page_refcounted(&p[i]); 215 } 216 217 /* Attach the unused pages to the buddy tree */ 218 for (i = reserved_pages; i < nr_pages; i++) 219 __hyp_put_page(pool, &p[i]); 220 221 return 0; 222 } 223