diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -620,7 +620,7 @@
 	 * handling for sv_minuser here, like is done for exec_new_vmspace().
 	 */
 	vm_map_init(&vmspace0.vm_map, vmspace_pmap(&vmspace0),
-	    p->p_sysent->sv_minuser, p->p_sysent->sv_maxuser);
+	    p->p_sysent->sv_minuser, p->p_sysent->sv_maxuser, false);
 
 	/*
 	 * Call the init and ctor for the new thread and proc.  We wait
diff --git a/sys/vm/vm_kern.c b/sys/vm/vm_kern.c
--- a/sys/vm/vm_kern.c
+++ b/sys/vm/vm_kern.c
@@ -455,7 +455,7 @@
 	if (ret != KERN_SUCCESS)
 		panic("kmem_subinit: bad status return of %d", ret);
 	*max = *min + size;
-	vm_map_init(map, vm_map_pmap(parent), *min, *max);
+	vm_map_init(map, vm_map_pmap(parent), *min, *max, false);
 	if (vm_map_submap(parent, *min, *max, map) != KERN_SUCCESS)
 		panic("kmem_subinit: unable to change range to submap");
 }
@@ -830,8 +830,7 @@
 	vm_size_t quantum;
 	int domain;
 
-	vm_map_init(kernel_map, kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
-	kernel_map->system_map = 1;
+	vm_map_init(kernel_map, kernel_pmap, VM_MIN_KERNEL_ADDRESS, end, true);
 	vm_map_lock(kernel_map);
 	/* N.B.: cannot use kgdb to debug, starting with this assignment ... */
 	(void)vm_map_insert(kernel_map, NULL, 0,
diff --git a/sys/vm/vm_map.h b/sys/vm/vm_map.h
--- a/sys/vm/vm_map.h
+++ b/sys/vm/vm_map.h
@@ -203,8 +203,10 @@
  */
 struct vm_map {
 	struct vm_map_entry header;	/* List of entries */
-	struct sx lock;			/* Lock for map data */
-	struct mtx system_mtx;
+	union {
+		struct sx lock;			/* Lock for map data */
+		struct mtx system_mtx;
+	};
 	int nentries;			/* Number of entries */
 	vm_size_t size;			/* virtual size */
 	u_int timestamp;		/* Version number */
@@ -483,7 +485,7 @@
     vm_prot_t, vm_prot_t, int);
 vm_offset_t vm_map_findspace(vm_map_t, vm_offset_t, vm_size_t);
 int vm_map_inherit (vm_map_t, vm_offset_t, vm_offset_t, vm_inherit_t);
-void vm_map_init(vm_map_t, pmap_t, vm_offset_t, vm_offset_t);
+void vm_map_init(vm_map_t, pmap_t, vm_offset_t, vm_offset_t, bool);
 int vm_map_insert (vm_map_t, vm_object_t, vm_ooffset_t, vm_offset_t, vm_offset_t, vm_prot_t, vm_prot_t, int);
 int vm_map_lookup (vm_map_t *, vm_offset_t, vm_prot_t, vm_map_entry_t *, vm_object_t *,
     vm_pindex_t *, vm_prot_t *, boolean_t *);
diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -126,7 +126,7 @@
 static uma_zone_t vmspace_zone;
 static int vmspace_zinit(void *mem, int size, int flags);
 static void _vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min,
-    vm_offset_t max);
+    vm_offset_t max, bool system_map);
 static void vm_map_entry_deallocate(vm_map_entry_t entry, boolean_t system_map);
 static void vm_map_entry_dispose(vm_map_t map, vm_map_entry_t entry);
 static void vm_map_entry_unwire(vm_map_t map, vm_map_entry_t entry);
@@ -293,8 +293,6 @@
 	map = &vm->vm_map;
 
 	memset(map, 0, sizeof(*map));
-	mtx_init(&map->system_mtx, "vm map (system)", NULL,
-	    MTX_DEF | MTX_DUPOK);
 	sx_init(&map->lock, "vm map (user)");
 	PMAP_LOCK_INIT(vmspace_pmap(vm));
 	return (0);
@@ -330,7 +328,7 @@
 		return (NULL);
 	}
 	CTR1(KTR_VM, "vmspace_alloc: %p", vm);
-	_vm_map_init(&vm->vm_map, vmspace_pmap(vm), min, max);
+	_vm_map_init(&vm->vm_map, vmspace_pmap(vm), min, max, false);
 	refcount_init(&vm->vm_refcnt, 1);
 	vm->vm_shm = NULL;
 	vm->vm_swrss = 0;
@@ -885,12 +883,13 @@
  * such as that in the vmspace structure.
  */
 static void
-_vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max)
+_vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max,
+    bool system_map)
 {
 
 	map->header.eflags = MAP_ENTRY_HEADER;
 	map->needs_wakeup = FALSE;
-	map->system_map = 0;
+	map->system_map = system_map;
 	map->pmap = pmap;
 	map->header.end = min;
 	map->header.start = max;
@@ -906,13 +905,16 @@
 }
 
 void
-vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max)
+vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max,
+    bool system_map)
 {
 
-	_vm_map_init(map, pmap, min, max);
-	mtx_init(&map->system_mtx, "vm map (system)", NULL,
-	    MTX_DEF | MTX_DUPOK);
-	sx_init(&map->lock, "vm map (user)");
+	_vm_map_init(map, pmap, min, max, system_map);
+	if (system_map)
+		mtx_init(&map->system_mtx, "vm map (system)", NULL,
+		    MTX_DEF | MTX_DUPOK);
+	else
+		sx_init(&map->lock, "vm map (user)");
 }
 
 /*