diff options
Diffstat (limited to 'util/mmap-alloc.c')
| -rw-r--r-- | util/mmap-alloc.c | 265 |
1 files changed, 212 insertions, 53 deletions
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c index fd329eccd8..ed14f9c64d 100644 --- a/util/mmap-alloc.c +++ b/util/mmap-alloc.c @@ -10,15 +10,52 @@ * later. See the COPYING file in the top-level directory. */ +#ifdef CONFIG_LINUX +#include <linux/mman.h> +#else /* !CONFIG_LINUX */ +#define MAP_SYNC 0x0 +#define MAP_SHARED_VALIDATE 0x0 +#endif /* CONFIG_LINUX */ + #include "qemu/osdep.h" #include "qemu/mmap-alloc.h" #include "qemu/host-utils.h" +#include "qemu/cutils.h" +#include "qemu/error-report.h" #define HUGETLBFS_MAGIC 0x958458f6 #ifdef CONFIG_LINUX #include <sys/vfs.h> +#include <linux/magic.h> +#endif + +QemuFsType qemu_fd_getfs(int fd) +{ +#ifdef CONFIG_LINUX + struct statfs fs; + int ret; + + if (fd < 0) { + return QEMU_FS_TYPE_UNKNOWN; + } + + do { + ret = fstatfs(fd, &fs); + } while (ret != 0 && errno == EINTR); + + switch (fs.f_type) { + case TMPFS_MAGIC: + return QEMU_FS_TYPE_TMPFS; + case HUGETLBFS_MAGIC: + return QEMU_FS_TYPE_HUGETLBFS; + default: + return QEMU_FS_TYPE_UNKNOWN; + } +#else + return QEMU_FS_TYPE_UNKNOWN; #endif +} size_t qemu_fd_getpagesize(int fd) { @@ -41,49 +78,84 @@ size_t qemu_fd_getpagesize(int fd) #endif #endif - return getpagesize(); + return qemu_real_host_page_size(); } -size_t qemu_mempath_getpagesize(const char *mem_path) +#define OVERCOMMIT_MEMORY_PATH "/proc/sys/vm/overcommit_memory" +static bool map_noreserve_effective(int fd, uint32_t qemu_map_flags) { -#ifdef CONFIG_LINUX - struct statfs fs; - int ret; +#if defined(__linux__) + const bool readonly = qemu_map_flags & QEMU_MAP_READONLY; + const bool shared = qemu_map_flags & QEMU_MAP_SHARED; + gchar *content = NULL; + const char *endptr; + unsigned int tmp; - if (mem_path) { - do { - ret = statfs(mem_path, &fs); - } while (ret != 0 && errno == EINTR); + /* + * hugeltb accounting is different than ordinary swap reservation: + * a) Hugetlb pages from the pool are reserved for both private and + * shared mappings. For shared mappings, all mappers have to specify + * MAP_NORESERVE. + * b) MAP_NORESERVE is not affected by /proc/sys/vm/overcommit_memory. + */ + if (qemu_fd_getpagesize(fd) != qemu_real_host_page_size()) { + return true; + } - if (ret != 0) { - fprintf(stderr, "Couldn't statfs() memory path: %s\n", - strerror(errno)); - exit(1); - } + /* + * Accountable mappings in the kernel that can be affected by MAP_NORESEVE + * are private writable mappings (see mm/mmap.c:accountable_mapping() in + * Linux). For all shared or readonly mappings, MAP_NORESERVE is always + * implicitly active -- no reservation; this includes shmem. The only + * exception is shared anonymous memory, it is accounted like private + * anonymous memory. + */ + if (readonly || (shared && fd >= 0)) { + return true; + } - if (fs.f_type == HUGETLBFS_MAGIC) { - /* It's hugepage, return the huge page size */ - return fs.f_bsize; + /* + * MAP_NORESERVE is globally ignored for applicable !hugetlb mappings when + * memory overcommit is set to "never". Sparse memory regions aren't really + * possible in this system configuration. + * + * Bail out now instead of silently committing way more memory than + * currently desired by the user. + */ + if (g_file_get_contents(OVERCOMMIT_MEMORY_PATH, &content, NULL, NULL) && + !qemu_strtoui(content, &endptr, 0, &tmp) && + (!endptr || *endptr == '\n')) { + if (tmp == 2) { + error_report("Skipping reservation of swap space is not supported:" + " \"" OVERCOMMIT_MEMORY_PATH "\" is \"2\""); + return false; } + return true; } -#ifdef __sparc__ - /* SPARC Linux needs greater alignment than the pagesize */ - return QEMU_VMALLOC_ALIGN; + /* this interface has been around since Linux 2.6 */ + error_report("Skipping reservation of swap space is not supported:" + " Could not read: \"" OVERCOMMIT_MEMORY_PATH "\""); + return false; #endif -#endif - - return getpagesize(); + /* + * E.g., FreeBSD used to define MAP_NORESERVE, never implemented it, + * and removed it a while ago. + */ + error_report("Skipping reservation of swap space is not supported"); + return false; } -void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared) +/* + * Reserve a new memory region of the requested size to be used for mapping + * from the given fd (if any). + */ +static void *mmap_reserve(size_t size, int fd) { - /* - * Note: this always allocates at least one extra page of virtual address - * space, even if size is already aligned. - */ - size_t total = size + align; + int flags = MAP_PRIVATE; + #if defined(__powerpc64__) && defined(__linux__) - /* On ppc64 mappings in the same segment (aka slice) must share the same + /* + * On ppc64 mappings in the same segment (aka slice) must share the same * page size. Since we will be re-allocating part of this segment * from the supplied fd, we should make sure to use the same page size, to * this end we mmap the supplied fd. In this case, set MAP_NORESERVE to @@ -91,36 +163,123 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared) * We do this unless we are using the system page size, in which case * anonymous memory is OK. */ - int anonfd = fd == -1 || qemu_fd_getpagesize(fd) == getpagesize() ? -1 : fd; - int flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE; - void *ptr = mmap(0, total, PROT_NONE, flags | MAP_PRIVATE, anonfd, 0); + if (fd == -1 || qemu_fd_getpagesize(fd) == qemu_real_host_page_size()) { + fd = -1; + flags |= MAP_ANONYMOUS; + } else { + flags |= MAP_NORESERVE; + } #else - void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + fd = -1; + flags |= MAP_ANONYMOUS; #endif - size_t offset; - void *ptr1; - if (ptr == MAP_FAILED) { + return mmap(0, size, PROT_NONE, flags, fd, 0); +} + +/* + * Activate memory in a reserved region from the given fd (if any), to make + * it accessible. + */ +static void *mmap_activate(void *ptr, size_t size, int fd, + uint32_t qemu_map_flags, off_t map_offset) +{ + const bool noreserve = qemu_map_flags & QEMU_MAP_NORESERVE; + const bool readonly = qemu_map_flags & QEMU_MAP_READONLY; + const bool shared = qemu_map_flags & QEMU_MAP_SHARED; + const bool sync = qemu_map_flags & QEMU_MAP_SYNC; + const int prot = PROT_READ | (readonly ? 0 : PROT_WRITE); + int map_sync_flags = 0; + int flags = MAP_FIXED; + void *activated_ptr; + + if (noreserve && !map_noreserve_effective(fd, qemu_map_flags)) { + return MAP_FAILED; + } + + flags |= fd == -1 ? MAP_ANONYMOUS : 0; + flags |= shared ? MAP_SHARED : MAP_PRIVATE; + flags |= noreserve ? MAP_NORESERVE : 0; + if (shared && sync) { + map_sync_flags = MAP_SYNC | MAP_SHARED_VALIDATE; + } + + activated_ptr = mmap(ptr, size, prot, flags | map_sync_flags, fd, + map_offset); + if (activated_ptr == MAP_FAILED && map_sync_flags) { + if (errno == ENOTSUP) { + char *proc_link = g_strdup_printf("/proc/self/fd/%d", fd); + char *file_name = g_malloc0(PATH_MAX); + int len = readlink(proc_link, file_name, PATH_MAX - 1); + + if (len < 0) { + len = 0; + } + file_name[len] = '\0'; + fprintf(stderr, "Warning: requesting persistence across crashes " + "for backend file %s failed. Proceeding without " + "persistence, data might become corrupted in case of host " + "crash.\n", file_name); + g_free(proc_link); + g_free(file_name); + warn_report("Using non DAX backing file with 'pmem=on' option" + " is deprecated"); + } + /* + * If mmap failed with MAP_SHARED_VALIDATE | MAP_SYNC, we will try + * again without these flags to handle backwards compatibility. + */ + activated_ptr = mmap(ptr, size, prot, flags, fd, map_offset); + } + return activated_ptr; +} + +static inline size_t mmap_guard_pagesize(int fd) +{ +#if defined(__powerpc64__) && defined(__linux__) + /* Mappings in the same segment must share the same page size */ + return qemu_fd_getpagesize(fd); +#else + return qemu_real_host_page_size(); +#endif +} + +void *qemu_ram_mmap(int fd, + size_t size, + size_t align, + uint32_t qemu_map_flags, + off_t map_offset) +{ + const size_t guard_pagesize = mmap_guard_pagesize(fd); + size_t offset, total; + void *ptr, *guardptr; + + /* + * Note: this always allocates at least one extra page of virtual address + * space, even if size is already aligned. + */ + total = size + align; + + guardptr = mmap_reserve(total, fd); + if (guardptr == MAP_FAILED) { return MAP_FAILED; } assert(is_power_of_2(align)); /* Always align to host page size */ - assert(align >= getpagesize()); - - offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr; - ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE, - MAP_FIXED | - (fd == -1 ? MAP_ANONYMOUS : 0) | - (shared ? MAP_SHARED : MAP_PRIVATE), - fd, 0); - if (ptr1 == MAP_FAILED) { - munmap(ptr, total); + assert(align >= guard_pagesize); + + offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr; + + ptr = mmap_activate(guardptr + offset, size, fd, qemu_map_flags, + map_offset); + if (ptr == MAP_FAILED) { + munmap(guardptr, total); return MAP_FAILED; } if (offset > 0) { - munmap(ptr, offset); + munmap(guardptr, offset); } /* @@ -128,17 +287,17 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared) * a guard page guarding against potential buffer overflows. */ total -= offset; - if (total > size + getpagesize()) { - munmap(ptr1 + size + getpagesize(), total - size - getpagesize()); + if (total > size + guard_pagesize) { + munmap(ptr + size + guard_pagesize, total - size - guard_pagesize); } - return ptr1; + return ptr; } -void qemu_ram_munmap(void *ptr, size_t size) +void qemu_ram_munmap(int fd, void *ptr, size_t size) { if (ptr) { /* Unmap both the RAM block and the guard page */ - munmap(ptr, size + getpagesize()); + munmap(ptr, size + mmap_guard_pagesize(fd)); } } |