}
#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,
char *c;
void *area = MAP_FAILED;
int fd = -1;
+ int64_t file_size;
if (kvm_enabled() && !kvm_has_sync_mmu()) {
error_setg(errp,
}
#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",
* 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");
}