Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 1 | /* |
| 2 | * Support for RAM backed by mmaped host memory. |
| 3 | * |
| 4 | * Copyright (c) 2015 Red Hat, Inc. |
| 5 | * |
| 6 | * Authors: |
| 7 | * Michael S. Tsirkin <mst@redhat.com> |
| 8 | * |
| 9 | * This work is licensed under the terms of the GNU GPL, version 2 or |
| 10 | * later. See the COPYING file in the top-level directory. |
| 11 | */ |
Markus Armbruster | a9c9427 | 2016-06-22 19:11:19 +0200 | [diff] [blame] | 12 | |
Zhang Yi | 119906af | 2019-04-22 08:48:48 +0800 | [diff] [blame] | 13 | #ifdef CONFIG_LINUX |
| 14 | #include <linux/mman.h> |
| 15 | #else /* !CONFIG_LINUX */ |
| 16 | #define MAP_SYNC 0x0 |
| 17 | #define MAP_SHARED_VALIDATE 0x0 |
| 18 | #endif /* CONFIG_LINUX */ |
| 19 | |
Peter Maydell | aafd758 | 2016-01-29 17:49:55 +0000 | [diff] [blame] | 20 | #include "qemu/osdep.h" |
Markus Armbruster | a9c9427 | 2016-06-22 19:11:19 +0200 | [diff] [blame] | 21 | #include "qemu/mmap-alloc.h" |
Cao jin | 4a3ecf2 | 2016-11-02 21:44:46 +0800 | [diff] [blame] | 22 | #include "qemu/host-utils.h" |
David Hildenbrand | d94e0bc | 2021-05-10 13:43:22 +0200 | [diff] [blame] | 23 | #include "qemu/cutils.h" |
David Hildenbrand | 8dbe22c | 2021-05-10 13:43:21 +0200 | [diff] [blame] | 24 | #include "qemu/error-report.h" |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 25 | |
Michael S. Tsirkin | 7197fb4 | 2015-12-02 21:14:12 +0200 | [diff] [blame] | 26 | #define HUGETLBFS_MAGIC 0x958458f6 |
| 27 | |
| 28 | #ifdef CONFIG_LINUX |
| 29 | #include <sys/vfs.h> |
| 30 | #endif |
| 31 | |
| 32 | size_t qemu_fd_getpagesize(int fd) |
| 33 | { |
| 34 | #ifdef CONFIG_LINUX |
| 35 | struct statfs fs; |
| 36 | int ret; |
| 37 | |
| 38 | if (fd != -1) { |
| 39 | do { |
| 40 | ret = fstatfs(fd, &fs); |
| 41 | } while (ret != 0 && errno == EINTR); |
| 42 | |
| 43 | if (ret == 0 && fs.f_type == HUGETLBFS_MAGIC) { |
| 44 | return fs.f_bsize; |
| 45 | } |
| 46 | } |
Peter Maydell | 57d1f6d | 2017-12-08 16:57:28 +0000 | [diff] [blame] | 47 | #ifdef __sparc__ |
| 48 | /* SPARC Linux needs greater alignment than the pagesize */ |
| 49 | return QEMU_VMALLOC_ALIGN; |
| 50 | #endif |
Michael S. Tsirkin | 7197fb4 | 2015-12-02 21:14:12 +0200 | [diff] [blame] | 51 | #endif |
| 52 | |
Marc-André Lureau | 8e3b0cb | 2022-03-23 19:57:22 +0400 | [diff] [blame] | 53 | return qemu_real_host_page_size(); |
Michael S. Tsirkin | 7197fb4 | 2015-12-02 21:14:12 +0200 | [diff] [blame] | 54 | } |
| 55 | |
David Hildenbrand | d94e0bc | 2021-05-10 13:43:22 +0200 | [diff] [blame] | 56 | #define OVERCOMMIT_MEMORY_PATH "/proc/sys/vm/overcommit_memory" |
| 57 | static bool map_noreserve_effective(int fd, uint32_t qemu_map_flags) |
| 58 | { |
| 59 | #if defined(__linux__) |
| 60 | const bool readonly = qemu_map_flags & QEMU_MAP_READONLY; |
| 61 | const bool shared = qemu_map_flags & QEMU_MAP_SHARED; |
| 62 | gchar *content = NULL; |
| 63 | const char *endptr; |
| 64 | unsigned int tmp; |
| 65 | |
| 66 | /* |
| 67 | * hugeltb accounting is different than ordinary swap reservation: |
| 68 | * a) Hugetlb pages from the pool are reserved for both private and |
| 69 | * shared mappings. For shared mappings, all mappers have to specify |
| 70 | * MAP_NORESERVE. |
| 71 | * b) MAP_NORESERVE is not affected by /proc/sys/vm/overcommit_memory. |
| 72 | */ |
Marc-André Lureau | 8e3b0cb | 2022-03-23 19:57:22 +0400 | [diff] [blame] | 73 | if (qemu_fd_getpagesize(fd) != qemu_real_host_page_size()) { |
David Hildenbrand | d94e0bc | 2021-05-10 13:43:22 +0200 | [diff] [blame] | 74 | return true; |
| 75 | } |
| 76 | |
| 77 | /* |
| 78 | * Accountable mappings in the kernel that can be affected by MAP_NORESEVE |
| 79 | * are private writable mappings (see mm/mmap.c:accountable_mapping() in |
| 80 | * Linux). For all shared or readonly mappings, MAP_NORESERVE is always |
| 81 | * implicitly active -- no reservation; this includes shmem. The only |
| 82 | * exception is shared anonymous memory, it is accounted like private |
| 83 | * anonymous memory. |
| 84 | */ |
| 85 | if (readonly || (shared && fd >= 0)) { |
| 86 | return true; |
| 87 | } |
| 88 | |
| 89 | /* |
| 90 | * MAP_NORESERVE is globally ignored for applicable !hugetlb mappings when |
| 91 | * memory overcommit is set to "never". Sparse memory regions aren't really |
| 92 | * possible in this system configuration. |
| 93 | * |
| 94 | * Bail out now instead of silently committing way more memory than |
| 95 | * currently desired by the user. |
| 96 | */ |
| 97 | if (g_file_get_contents(OVERCOMMIT_MEMORY_PATH, &content, NULL, NULL) && |
| 98 | !qemu_strtoui(content, &endptr, 0, &tmp) && |
| 99 | (!endptr || *endptr == '\n')) { |
| 100 | if (tmp == 2) { |
| 101 | error_report("Skipping reservation of swap space is not supported:" |
| 102 | " \"" OVERCOMMIT_MEMORY_PATH "\" is \"2\""); |
| 103 | return false; |
| 104 | } |
| 105 | return true; |
| 106 | } |
| 107 | /* this interface has been around since Linux 2.6 */ |
| 108 | error_report("Skipping reservation of swap space is not supported:" |
| 109 | " Could not read: \"" OVERCOMMIT_MEMORY_PATH "\""); |
| 110 | return false; |
| 111 | #endif |
| 112 | /* |
| 113 | * E.g., FreeBSD used to define MAP_NORESERVE, never implemented it, |
| 114 | * and removed it a while ago. |
| 115 | */ |
| 116 | error_report("Skipping reservation of swap space is not supported"); |
| 117 | return false; |
| 118 | } |
| 119 | |
David Hildenbrand | 01c26ad | 2021-05-10 13:43:15 +0200 | [diff] [blame] | 120 | /* |
| 121 | * Reserve a new memory region of the requested size to be used for mapping |
| 122 | * from the given fd (if any). |
| 123 | */ |
| 124 | static void *mmap_reserve(size_t size, int fd) |
| 125 | { |
| 126 | int flags = MAP_PRIVATE; |
| 127 | |
| 128 | #if defined(__powerpc64__) && defined(__linux__) |
| 129 | /* |
| 130 | * On ppc64 mappings in the same segment (aka slice) must share the same |
| 131 | * page size. Since we will be re-allocating part of this segment |
| 132 | * from the supplied fd, we should make sure to use the same page size, to |
| 133 | * this end we mmap the supplied fd. In this case, set MAP_NORESERVE to |
| 134 | * avoid allocating backing store memory. |
| 135 | * We do this unless we are using the system page size, in which case |
| 136 | * anonymous memory is OK. |
| 137 | */ |
Marc-André Lureau | 8e3b0cb | 2022-03-23 19:57:22 +0400 | [diff] [blame] | 138 | if (fd == -1 || qemu_fd_getpagesize(fd) == qemu_real_host_page_size()) { |
David Hildenbrand | 01c26ad | 2021-05-10 13:43:15 +0200 | [diff] [blame] | 139 | fd = -1; |
| 140 | flags |= MAP_ANONYMOUS; |
| 141 | } else { |
| 142 | flags |= MAP_NORESERVE; |
| 143 | } |
| 144 | #else |
| 145 | fd = -1; |
| 146 | flags |= MAP_ANONYMOUS; |
| 147 | #endif |
| 148 | |
| 149 | return mmap(0, size, PROT_NONE, flags, fd, 0); |
| 150 | } |
| 151 | |
David Hildenbrand | d01cbf8 | 2021-05-10 13:43:16 +0200 | [diff] [blame] | 152 | /* |
| 153 | * Activate memory in a reserved region from the given fd (if any), to make |
| 154 | * it accessible. |
| 155 | */ |
David Hildenbrand | b444f5c | 2021-05-10 13:43:20 +0200 | [diff] [blame] | 156 | static void *mmap_activate(void *ptr, size_t size, int fd, |
| 157 | uint32_t qemu_map_flags, off_t map_offset) |
David Hildenbrand | d01cbf8 | 2021-05-10 13:43:16 +0200 | [diff] [blame] | 158 | { |
David Hildenbrand | 8dbe22c | 2021-05-10 13:43:21 +0200 | [diff] [blame] | 159 | const bool noreserve = qemu_map_flags & QEMU_MAP_NORESERVE; |
David Hildenbrand | b444f5c | 2021-05-10 13:43:20 +0200 | [diff] [blame] | 160 | const bool readonly = qemu_map_flags & QEMU_MAP_READONLY; |
| 161 | const bool shared = qemu_map_flags & QEMU_MAP_SHARED; |
| 162 | const bool sync = qemu_map_flags & QEMU_MAP_SYNC; |
David Hildenbrand | d01cbf8 | 2021-05-10 13:43:16 +0200 | [diff] [blame] | 163 | const int prot = PROT_READ | (readonly ? 0 : PROT_WRITE); |
| 164 | int map_sync_flags = 0; |
| 165 | int flags = MAP_FIXED; |
| 166 | void *activated_ptr; |
| 167 | |
David Hildenbrand | d94e0bc | 2021-05-10 13:43:22 +0200 | [diff] [blame] | 168 | if (noreserve && !map_noreserve_effective(fd, qemu_map_flags)) { |
David Hildenbrand | 8dbe22c | 2021-05-10 13:43:21 +0200 | [diff] [blame] | 169 | return MAP_FAILED; |
| 170 | } |
| 171 | |
David Hildenbrand | d01cbf8 | 2021-05-10 13:43:16 +0200 | [diff] [blame] | 172 | flags |= fd == -1 ? MAP_ANONYMOUS : 0; |
| 173 | flags |= shared ? MAP_SHARED : MAP_PRIVATE; |
David Hildenbrand | d94e0bc | 2021-05-10 13:43:22 +0200 | [diff] [blame] | 174 | flags |= noreserve ? MAP_NORESERVE : 0; |
David Hildenbrand | b444f5c | 2021-05-10 13:43:20 +0200 | [diff] [blame] | 175 | if (shared && sync) { |
David Hildenbrand | d01cbf8 | 2021-05-10 13:43:16 +0200 | [diff] [blame] | 176 | map_sync_flags = MAP_SYNC | MAP_SHARED_VALIDATE; |
| 177 | } |
| 178 | |
| 179 | activated_ptr = mmap(ptr, size, prot, flags | map_sync_flags, fd, |
| 180 | map_offset); |
| 181 | if (activated_ptr == MAP_FAILED && map_sync_flags) { |
| 182 | if (errno == ENOTSUP) { |
| 183 | char *proc_link = g_strdup_printf("/proc/self/fd/%d", fd); |
| 184 | char *file_name = g_malloc0(PATH_MAX); |
| 185 | int len = readlink(proc_link, file_name, PATH_MAX - 1); |
| 186 | |
| 187 | if (len < 0) { |
| 188 | len = 0; |
| 189 | } |
| 190 | file_name[len] = '\0'; |
| 191 | fprintf(stderr, "Warning: requesting persistence across crashes " |
| 192 | "for backend file %s failed. Proceeding without " |
| 193 | "persistence, data might become corrupted in case of host " |
| 194 | "crash.\n", file_name); |
| 195 | g_free(proc_link); |
| 196 | g_free(file_name); |
Igor Mammedov | cdcf766 | 2021-01-11 15:33:32 -0500 | [diff] [blame] | 197 | warn_report("Using non DAX backing file with 'pmem=on' option" |
| 198 | " is deprecated"); |
David Hildenbrand | d01cbf8 | 2021-05-10 13:43:16 +0200 | [diff] [blame] | 199 | } |
| 200 | /* |
| 201 | * If mmap failed with MAP_SHARED_VALIDATE | MAP_SYNC, we will try |
| 202 | * again without these flags to handle backwards compatibility. |
| 203 | */ |
| 204 | activated_ptr = mmap(ptr, size, prot, flags, fd, map_offset); |
| 205 | } |
| 206 | return activated_ptr; |
| 207 | } |
| 208 | |
David Hildenbrand | adad0b3 | 2021-05-10 13:43:14 +0200 | [diff] [blame] | 209 | static inline size_t mmap_guard_pagesize(int fd) |
| 210 | { |
| 211 | #if defined(__powerpc64__) && defined(__linux__) |
| 212 | /* Mappings in the same segment must share the same page size */ |
| 213 | return qemu_fd_getpagesize(fd); |
| 214 | #else |
Marc-André Lureau | 8e3b0cb | 2022-03-23 19:57:22 +0400 | [diff] [blame] | 215 | return qemu_real_host_page_size(); |
David Hildenbrand | adad0b3 | 2021-05-10 13:43:14 +0200 | [diff] [blame] | 216 | #endif |
| 217 | } |
| 218 | |
Zhang Yi | 2ac0f16 | 2019-02-08 18:10:37 +0800 | [diff] [blame] | 219 | void *qemu_ram_mmap(int fd, |
| 220 | size_t size, |
| 221 | size_t align, |
David Hildenbrand | b444f5c | 2021-05-10 13:43:20 +0200 | [diff] [blame] | 222 | uint32_t qemu_map_flags, |
Jagannathan Raman | 44a4ff3 | 2021-01-29 11:46:04 -0500 | [diff] [blame] | 223 | off_t map_offset) |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 224 | { |
David Hildenbrand | adad0b3 | 2021-05-10 13:43:14 +0200 | [diff] [blame] | 225 | const size_t guard_pagesize = mmap_guard_pagesize(fd); |
David Hildenbrand | d01cbf8 | 2021-05-10 13:43:16 +0200 | [diff] [blame] | 226 | size_t offset, total; |
| 227 | void *ptr, *guardptr; |
Murilo Opsfelder Araujo | 2044c3e | 2019-01-30 21:36:04 -0200 | [diff] [blame] | 228 | |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 229 | /* |
| 230 | * Note: this always allocates at least one extra page of virtual address |
| 231 | * space, even if size is already aligned. |
| 232 | */ |
Murilo Opsfelder Araujo | 2044c3e | 2019-01-30 21:36:04 -0200 | [diff] [blame] | 233 | total = size + align; |
| 234 | |
David Hildenbrand | 01c26ad | 2021-05-10 13:43:15 +0200 | [diff] [blame] | 235 | guardptr = mmap_reserve(total, fd); |
Murilo Opsfelder Araujo | 2044c3e | 2019-01-30 21:36:04 -0200 | [diff] [blame] | 236 | if (guardptr == MAP_FAILED) { |
Michael S. Tsirkin | 9d4ec93 | 2015-10-25 17:07:45 +0200 | [diff] [blame] | 237 | return MAP_FAILED; |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 238 | } |
| 239 | |
Cao jin | 4a3ecf2 | 2016-11-02 21:44:46 +0800 | [diff] [blame] | 240 | assert(is_power_of_2(align)); |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 241 | /* Always align to host page size */ |
David Hildenbrand | adad0b3 | 2021-05-10 13:43:14 +0200 | [diff] [blame] | 242 | assert(align >= guard_pagesize); |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 243 | |
Murilo Opsfelder Araujo | 2044c3e | 2019-01-30 21:36:04 -0200 | [diff] [blame] | 244 | offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr; |
| 245 | |
David Hildenbrand | b444f5c | 2021-05-10 13:43:20 +0200 | [diff] [blame] | 246 | ptr = mmap_activate(guardptr + offset, size, fd, qemu_map_flags, |
David Hildenbrand | d01cbf8 | 2021-05-10 13:43:16 +0200 | [diff] [blame] | 247 | map_offset); |
Murilo Opsfelder Araujo | 2044c3e | 2019-01-30 21:36:04 -0200 | [diff] [blame] | 248 | if (ptr == MAP_FAILED) { |
| 249 | munmap(guardptr, total); |
Michael S. Tsirkin | 9d4ec93 | 2015-10-25 17:07:45 +0200 | [diff] [blame] | 250 | return MAP_FAILED; |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 251 | } |
| 252 | |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 253 | if (offset > 0) { |
Murilo Opsfelder Araujo | 2044c3e | 2019-01-30 21:36:04 -0200 | [diff] [blame] | 254 | munmap(guardptr, offset); |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 255 | } |
| 256 | |
| 257 | /* |
| 258 | * Leave a single PROT_NONE page allocated after the RAM block, to serve as |
| 259 | * a guard page guarding against potential buffer overflows. |
| 260 | */ |
Cao jin | 6e4c890 | 2016-11-02 21:44:47 +0800 | [diff] [blame] | 261 | total -= offset; |
David Hildenbrand | adad0b3 | 2021-05-10 13:43:14 +0200 | [diff] [blame] | 262 | if (total > size + guard_pagesize) { |
| 263 | munmap(ptr + size + guard_pagesize, total - size - guard_pagesize); |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 264 | } |
| 265 | |
Murilo Opsfelder Araujo | 2044c3e | 2019-01-30 21:36:04 -0200 | [diff] [blame] | 266 | return ptr; |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 267 | } |
| 268 | |
Murilo Opsfelder Araujo | 53adb9d | 2019-01-30 21:36:05 -0200 | [diff] [blame] | 269 | void qemu_ram_munmap(int fd, void *ptr, size_t size) |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 270 | { |
| 271 | if (ptr) { |
| 272 | /* Unmap both the RAM block and the guard page */ |
David Hildenbrand | adad0b3 | 2021-05-10 13:43:14 +0200 | [diff] [blame] | 273 | munmap(ptr, size + mmap_guard_pagesize(fd)); |
Michael S. Tsirkin | 794e8f3 | 2015-09-24 14:41:17 +0300 | [diff] [blame] | 274 | } |
| 275 | } |