diff options
| -rw-r--r-- | exec.c | 22 |
1 files changed, 21 insertions, 1 deletions
@@ -1229,6 +1229,15 @@ void qemu_mutex_unlock_ramlist(void) } #ifdef __linux__ +static int64_t get_file_size(int fd) +{ + int64_t size = lseek(fd, 0, SEEK_END); + if (size < 0) { + return -errno; + } + return size; +} + static void *file_ram_alloc(RAMBlock *block, ram_addr_t memory, const char *path, @@ -1240,6 +1249,7 @@ static void *file_ram_alloc(RAMBlock *block, char *c; void *area = MAP_FAILED; int fd = -1; + int64_t file_size; if (kvm_enabled() && !kvm_has_sync_mmu()) { error_setg(errp, @@ -1302,6 +1312,8 @@ static void *file_ram_alloc(RAMBlock *block, } #endif + file_size = get_file_size(fd); + if (memory < block->page_size) { error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to " "or larger than page size 0x%zx", @@ -1316,8 +1328,16 @@ static void *file_ram_alloc(RAMBlock *block, * hosts, so don't bother bailing out on errors. * If anything goes wrong with it under other filesystems, * mmap will fail. + * + * Do not truncate the non-empty backend file to avoid corrupting + * the existing data in the file. Disabling shrinking is not + * enough. For example, the current vNVDIMM implementation stores + * the guest NVDIMM labels at the end of the backend file. If the + * backend file is later extended, QEMU will not be able to find + * those labels. Therefore, extending the non-empty backend file + * is disabled as well. */ - if (ftruncate(fd, memory)) { + if (!file_size && ftruncate(fd, memory)) { perror("ftruncate"); } |