diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index e319ec1ad8..52fdc0a48a 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -15,6 +15,7 @@
 #include "sysemu/hostmem.h"
 #include "sysemu/sysemu.h"
 #include "qom/object_interfaces.h"
+#include "qapi-visit.h"
 
 /* hostmem-file.c */
 /**
@@ -35,6 +36,7 @@ struct HostMemoryBackendFile {
     bool discard_data;
     char *mem_path;
     uint64_t align;
+    OnOffAuto sync;
 };
 
 static void
@@ -60,7 +62,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
         memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
                                  path,
                                  backend->size, fb->align, fb->share,
-                                 fb->mem_path, errp);
+                                 fb->sync, fb->mem_path, errp);
         g_free(path);
     }
 #endif
@@ -150,6 +152,38 @@ static void file_memory_backend_set_align(Object *o, Visitor *v,
     error_propagate(errp, local_err);
 }
 
+static void file_memory_backend_get_sync(
+    Object *obj, Visitor *v, const char *name, void *opaque, Error **errp)
+{
+    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
+    OnOffAuto value = fb->sync;
+
+    visit_type_OnOffAuto(v, name, &value, errp);
+}
+
+static void file_memory_backend_set_sync(
+    Object *obj, Visitor *v, const char *name, void *opaque, Error **errp)
+{
+    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
+    Error *local_err = NULL;
+    OnOffAuto value;
+
+    if (host_memory_backend_mr_inited(backend)) {
+        error_setg(&local_err, "cannot change property value");
+        goto out;
+    }
+
+    visit_type_OnOffAuto(v, name, &value, &local_err);
+    if (local_err) {
+        goto out;
+    }
+    fb->sync = value;
+
+ out:
+    error_propagate(errp, local_err);
+}
+
 static void file_backend_unparent(Object *obj)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
@@ -184,6 +218,9 @@ file_backend_class_init(ObjectClass *oc, void *data)
         file_memory_backend_get_align,
         file_memory_backend_set_align,
         NULL, NULL, &error_abort);
+    object_class_property_add(oc, "sync", "OnOffAuto",
+        file_memory_backend_get_sync, file_memory_backend_set_sync,
+        NULL, NULL, &error_abort);
 }
 
 static void file_backend_instance_finalize(Object *o)
diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt
index e903d8bb09..49b174fe66 100644
--- a/docs/nvdimm.txt
+++ b/docs/nvdimm.txt
@@ -143,10 +143,23 @@ Guest Data Persistence
 ----------------------
 
 Though QEMU supports multiple types of vNVDIMM backends on Linux,
-currently the only one that can guarantee the guest write persistence
+if MAP_SYNC is not supported by the host kernel and the backends,
+the only backend that can guarantee the guest write persistence
 is the device DAX on the real NVDIMM device (e.g., /dev/dax0.0), to
 which all guest access do not involve any host-side kernel cache.
 
+mmap(2) flag MAP_SYNC is added since Linux kernel 4.15. On such
+systems, QEMU can mmap(2) the backend with MAP_SYNC, which can
+guarantee the guest write persistence to vNVDIMM. Besides the host
+kernel support, enabling MAP_SYNC in QEMU also requires:
+
+ - the backend is a file supporting DAX, e.g., a file on an ext4 or
+   xfs file system mounted with "-o dax",
+
+ - 'sync' option of memory-backend-file is not 'off', and
+
+ - 'share' option of memory-backend-file is 'on'.
+
 When using other types of backends, it's suggested to set 'unarmed'
 option of '-device nvdimm' to 'on', which sets the unarmed flag of the
 guest NVDIMM region mapping structure.  This unarmed flag indicates
diff --git a/exec.c b/exec.c
index f4254cb6d3..ce13f8cb21 100644
--- a/exec.c
+++ b/exec.c
@@ -1600,6 +1600,7 @@ static void *file_ram_alloc(RAMBlock *block,
                             ram_addr_t memory,
                             int fd,
                             bool truncate,
+                            OnOffAuto sync,
                             Error **errp)
 {
     void *area;
@@ -1646,7 +1647,7 @@ static void *file_ram_alloc(RAMBlock *block,
     }
 
     area = qemu_ram_mmap(fd, memory, block->mr->align,
-                         block->flags & RAM_SHARED, ON_OFF_AUTO_OFF);
+                         block->flags & RAM_SHARED, sync);
     if (area == MAP_FAILED) {
         error_setg_errno(errp, errno,
                          "unable to map backing store for guest RAM");
@@ -1974,7 +1975,7 @@ static void ram_block_add(RAMBlock *new_block, Error **errp)
 
 #ifdef __linux__
 RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
-                                 bool share, int fd,
+                                 bool share, OnOffAuto sync, int fd,
                                  Error **errp)
 {
     RAMBlock *new_block;
@@ -2017,7 +2018,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
     new_block->used_length = size;
     new_block->max_length = size;
     new_block->flags = share ? RAM_SHARED : 0;
-    new_block->host = file_ram_alloc(new_block, size, fd, !file_size, errp);
+    new_block->host = file_ram_alloc(new_block, size, fd, !file_size, sync,
+                                     errp);
     if (!new_block->host) {
         g_free(new_block);
         return NULL;
@@ -2035,7 +2037,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
 
 
 RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
-                                   bool share, const char *mem_path,
+                                   bool share, OnOffAuto sync,
+                                   const char *mem_path,
                                    Error **errp)
 {
     int fd;
@@ -2047,7 +2050,7 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
         return NULL;
     }
 
-    block = qemu_ram_alloc_from_fd(size, mr, share, fd, errp);
+    block = qemu_ram_alloc_from_fd(size, mr, share, sync, fd, errp);
     if (!block) {
         if (created) {
             unlink(mem_path);
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 07c5d6d597..ff3cd583e9 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -468,6 +468,9 @@ void memory_region_init_resizeable_ram(MemoryRegion *mr,
  * @align: alignment of the region base address; if 0, the default alignment
  *         (getpagesize()) will be used.
  * @share: %true if memory must be mmaped with the MAP_SHARED flag
+ * @sync: %ON_OFF_AUTO_ON if memory must be mapped with MAP_SYNC flag;
+ *        %ON_OFF_AUTO_OFF if memory cannot be mapped with MAP_SYNC flag;
+ *        %ON_OFF_AUTO_AUTO directs QEMU to mmap with MAP_SYNC flag if possible
  * @path: the path in which to allocate the RAM.
  * @errp: pointer to Error*, to store an error if it happens.
  *
@@ -480,6 +483,7 @@ void memory_region_init_ram_from_file(MemoryRegion *mr,
                                       uint64_t size,
                                       uint64_t align,
                                       bool share,
+                                      OnOffAuto sync,
                                       const char *path,
                                       Error **errp);
 
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 6cbc02aa0f..4494ae9132 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -73,10 +73,10 @@ static inline unsigned long int ramblock_recv_bitmap_offset(void *host_addr,
 long qemu_getrampagesize(void);
 unsigned long last_ram_page(void);
 RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
-                                   bool share, const char *mem_path,
-                                   Error **errp);
+                                   bool share, OnOffAuto sync,
+                                   const char *mem_path, Error **errp);
 RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
-                                 bool share, int fd,
+                                 bool share, OnOffAuto sync, int fd,
                                  Error **errp);
 RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
                                   MemoryRegion *mr, Error **errp);
diff --git a/memory.c b/memory.c
index 449a1429b9..e22f51394e 100644
--- a/memory.c
+++ b/memory.c
@@ -1572,6 +1572,7 @@ void memory_region_init_ram_from_file(MemoryRegion *mr,
                                       uint64_t size,
                                       uint64_t align,
                                       bool share,
+                                      OnOffAuto sync,
                                       const char *path,
                                       Error **errp)
 {
@@ -1580,7 +1581,7 @@ void memory_region_init_ram_from_file(MemoryRegion *mr,
     mr->terminates = true;
     mr->destructor = memory_region_destructor_ram;
     mr->align = align;
-    mr->ram_block = qemu_ram_alloc_from_file(size, mr, share, path, errp);
+    mr->ram_block = qemu_ram_alloc_from_file(size, mr, share, sync, path, errp);
     mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0;
 }
 
@@ -1596,7 +1597,8 @@ void memory_region_init_ram_from_fd(MemoryRegion *mr,
     mr->ram = true;
     mr->terminates = true;
     mr->destructor = memory_region_destructor_ram;
-    mr->ram_block = qemu_ram_alloc_from_fd(size, mr, share, fd, errp);
+    mr->ram_block = qemu_ram_alloc_from_fd(size, mr, share, ON_OFF_AUTO_OFF, fd,
+                                           errp);
     mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0;
 }
 #endif
diff --git a/numa.c b/numa.c
index 83675a03f3..93180510a4 100644
--- a/numa.c
+++ b/numa.c
@@ -457,7 +457,7 @@ static void allocate_system_memory_nonnuma(MemoryRegion *mr, Object *owner,
 #ifdef __linux__
         Error *err = NULL;
         memory_region_init_ram_from_file(mr, owner, name, ram_size, 0, false,
-                                         mem_path, &err);
+                                         ON_OFF_AUTO_OFF, mem_path, &err);
         if (err) {
             error_report_err(err);
             if (mem_prealloc) {
diff --git a/qemu-options.hx b/qemu-options.hx
index 5ff741a4af..3ee423e6a8 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3974,7 +3974,7 @@ property must be set.  These objects are placed in the
 
 @table @option
 
-@item -object memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align}
+@item -object memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align},sync=@var{on|off|auto}
 
 Creates a memory file backend object, which can be used to back
 the guest RAM with huge pages.
@@ -4034,6 +4034,25 @@ requires an alignment different than the default one used by QEMU, eg
 the device DAX /dev/dax0.0 requires 2M alignment rather than 4K. In
 such cases, users can specify the required alignment via this option.
 
+The @option{sync} option specifies whether QEMU mmap(2) @option{mem-path}
+with MAP_SYNC flag, which can fully guarantee the guest write
+persistence to @option{mem-path}. MAP_SYNC requires supports from both
+the host kernel (since Linux kernel 4.15) and @option{mem-path} (only
+files supporting DAX). It can take one of following values:
+
+@table @option
+@item @var{on}
+try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or
+@option{share}=@var{off}, QEMU will abort
+
+@item @var{off}
+never pass MAP_SYNC to mmap(2)
+
+@item @var{auto} (default)
+if MAP_SYNC is supported and @option{share}=@var{on}, work as if
+@option{sync}=@var{on}; otherwise, work as if @option{sync}=@var{off}
+@end table
+
 @item -object memory-backend-ram,id=@var{id},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},size=@var{size},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave}
 
 Creates a memory backend object, which can be used to back the guest RAM.
