Index: libomptarget/include/omptarget.h
===================================================================
--- libomptarget/include/omptarget.h
+++ libomptarget/include/omptarget.h
@@ -47,6 +47,8 @@
   OMP_TGT_MAPTYPE_LITERAL         = 0x100,
   // mapping is implicit
   OMP_TGT_MAPTYPE_IMPLICIT        = 0x200,
+  // copy data to device
+  OMP_TGT_MAPTYPE_CLOSE           = 0x400,
   // member of struct, member given by [16 MSBs] - 1
   OMP_TGT_MAPTYPE_MEMBER_OF       = 0xffff000000000000
 };
Index: libomptarget/src/device.h
===================================================================
--- libomptarget/src/device.h
+++ libomptarget/src/device.h
@@ -137,11 +137,13 @@
   long getMapEntryRefCnt(void *HstPtrBegin);
   LookupResult lookupMapping(void *HstPtrBegin, int64_t Size);
   void *getOrAllocTgtPtr(void *HstPtrBegin, void *HstPtrBase, int64_t Size,
-      bool &IsNew, bool &IsHostPtr, bool IsImplicit, bool UpdateRefCount = true);
+      bool &IsNew, bool &IsHostPtr, bool IsImplicit, bool UpdateRefCount = true,
+      bool HasCloseModifier = false);
   void *getTgtPtrBegin(void *HstPtrBegin, int64_t Size);
   void *getTgtPtrBegin(void *HstPtrBegin, int64_t Size, bool &IsLast,
       bool UpdateRefCount, bool &IsHostPtr);
-  int deallocTgtPtr(void *TgtPtrBegin, int64_t Size, bool ForceDelete);
+  int deallocTgtPtr(void *TgtPtrBegin, int64_t Size, bool ForceDelete,
+                    bool HasCloseModifier = false);
   int associatePtr(void *HstPtrBegin, void *TgtPtrBegin, int64_t Size);
   int disassociatePtr(void *HstPtrBegin);
 
Index: libomptarget/src/device.cpp
===================================================================
--- libomptarget/src/device.cpp
+++ libomptarget/src/device.cpp
@@ -158,7 +158,7 @@
 // to do an illegal mapping.
 void *DeviceTy::getOrAllocTgtPtr(void *HstPtrBegin, void *HstPtrBase,
     int64_t Size, bool &IsNew, bool &IsHostPtr, bool IsImplicit,
-    bool UpdateRefCount) {
+    bool UpdateRefCount, bool HasCloseModifier) {
   void *rc = NULL;
   IsHostPtr = false;
   DataMapMtx.lock();
@@ -168,9 +168,9 @@
   // privatized use host address. Any explicitly mapped variables also use
   // host address where correctness is not impeded. In all other cases
   // maps are respected.
-  // TODO: In addition to the mapping rules above, when the close map
-  // modifier is implemented, foce the mapping of the variable to the device.
-  if (RTLRequiresFlags & OMP_REQ_UNIFIED_SHARED_MEMORY &&
+  // In addition to the mapping rules above, the close map
+  // modifier forces the mapping of the variable to the device.
+  if (RTLRequiresFlags & OMP_REQ_UNIFIED_SHARED_MEMORY && !HasCloseModifier &&
       (IsImplicit || !lr.Flags.IsContained || Size)) {
     DP("Return HstPtrBegin " DPxMOD " Size=%ld RefCount=%s\n",
        DPxPTR((uintptr_t)HstPtrBegin), Size, (UpdateRefCount ? " updated" : ""));
@@ -202,8 +202,8 @@
       IsNew = true;
       uintptr_t tp = (uintptr_t)RTL->data_alloc(RTLDeviceID, Size, HstPtrBegin);
       DP("Creating new map entry: HstBase=" DPxMOD ", HstBegin=" DPxMOD ", "
-          "HstEnd=" DPxMOD ", TgtBegin=" DPxMOD "\n", DPxPTR(HstPtrBase),
-          DPxPTR(HstPtrBegin), DPxPTR((uintptr_t)HstPtrBegin + Size), DPxPTR(tp));
+         "HstEnd=" DPxMOD ", TgtBegin=" DPxMOD "\n", DPxPTR(HstPtrBase),
+         DPxPTR(HstPtrBegin), DPxPTR((uintptr_t)HstPtrBegin + Size), DPxPTR(tp));
       HostDataToTargetMap.push_front(HostDataToTargetTy((uintptr_t)HstPtrBase,
           (uintptr_t)HstPtrBegin, (uintptr_t)HstPtrBegin + Size, tp));
       rc = (void *)tp;
@@ -274,8 +274,9 @@
   return NULL;
 }
 
-int DeviceTy::deallocTgtPtr(void *HstPtrBegin, int64_t Size, bool ForceDelete) {
-  if (RTLRequiresFlags & OMP_REQ_UNIFIED_SHARED_MEMORY)
+int DeviceTy::deallocTgtPtr(void *HstPtrBegin, int64_t Size, bool ForceDelete,
+                            bool HasCloseModifier) {
+  if (RTLRequiresFlags & OMP_REQ_UNIFIED_SHARED_MEMORY && !HasCloseModifier)
     return OFFLOAD_SUCCESS;
   // Check if the pointer is contained in any sub-nodes.
   int rc;
Index: libomptarget/src/omptarget.cpp
===================================================================
--- libomptarget/src/omptarget.cpp
+++ libomptarget/src/omptarget.cpp
@@ -244,6 +244,9 @@
     bool IsNew, Pointer_IsNew;
     bool IsHostPtr = false;
     bool IsImplicit = arg_types[i] & OMP_TGT_MAPTYPE_IMPLICIT;
+    // Force the creation of a device side copy of the data when:
+    // a close map modifier was associated with a map that contained a to.
+    bool HasCloseModifier = arg_types[i] & OMP_TGT_MAPTYPE_CLOSE;
     // UpdateRef is based on MEMBER_OF instead of TARGET_PARAM because if we
     // have reached this point via __tgt_target_data_begin and not __tgt_target
     // then no argument is marked as TARGET_PARAM ("omp target data map" is not
@@ -254,7 +257,8 @@
       DP("Has a pointer entry: \n");
       // base is address of pointer.
       Pointer_TgtPtrBegin = Device.getOrAllocTgtPtr(HstPtrBase, HstPtrBase,
-          sizeof(void *), Pointer_IsNew, IsHostPtr, IsImplicit, UpdateRef);
+          sizeof(void *), Pointer_IsNew, IsHostPtr, IsImplicit, UpdateRef,
+          HasCloseModifier);
       if (!Pointer_TgtPtrBegin) {
         DP("Call to getOrAllocTgtPtr returned null pointer (device failure or "
             "illegal mapping).\n");
@@ -270,7 +274,7 @@
     }
 
     void *TgtPtrBegin = Device.getOrAllocTgtPtr(HstPtrBegin, HstPtrBase,
-        data_size, IsNew, IsHostPtr, IsImplicit, UpdateRef);
+        data_size, IsNew, IsHostPtr, IsImplicit, UpdateRef, HasCloseModifier);
     if (!TgtPtrBegin && data_size) {
       // If data_size==0, then the argument could be a zero-length pointer to
       // NULL, so getOrAlloc() returning NULL is not an error.
@@ -290,8 +294,10 @@
 
     if (arg_types[i] & OMP_TGT_MAPTYPE_TO) {
       bool copy = false;
-      if (!(Device.RTLRequiresFlags & OMP_REQ_UNIFIED_SHARED_MEMORY)) {
-        if (IsNew || (arg_types[i] & OMP_TGT_MAPTYPE_ALWAYS)) {
+      if (!(Device.RTLRequiresFlags & OMP_REQ_UNIFIED_SHARED_MEMORY) ||
+          HasCloseModifier) {
+        if (IsNew || (arg_types[i] & OMP_TGT_MAPTYPE_ALWAYS) ||
+            HasCloseModifier) {
           copy = true;
         } else if (arg_types[i] & OMP_TGT_MAPTYPE_MEMBER_OF) {
           // Copy data only if the "parent" struct has RefCount==1.
@@ -370,6 +376,7 @@
     bool UpdateRef = !(arg_types[i] & OMP_TGT_MAPTYPE_MEMBER_OF) ||
         (arg_types[i] & OMP_TGT_MAPTYPE_PTR_AND_OBJ);
     bool ForceDelete = arg_types[i] & OMP_TGT_MAPTYPE_DELETE;
+    bool HasCloseModifier = arg_types[i] & OMP_TGT_MAPTYPE_CLOSE;
 
     // If PTR_AND_OBJ, HstPtrBegin is address of pointee
     void *TgtPtrBegin = Device.getTgtPtrBegin(HstPtrBegin, data_size, IsLast,
@@ -390,7 +397,8 @@
       if (arg_types[i] & OMP_TGT_MAPTYPE_FROM) {
         bool Always = arg_types[i] & OMP_TGT_MAPTYPE_ALWAYS;
         bool CopyMember = false;
-        if (!(Device.RTLRequiresFlags & OMP_REQ_UNIFIED_SHARED_MEMORY)) {
+        if (!(Device.RTLRequiresFlags & OMP_REQ_UNIFIED_SHARED_MEMORY) ||
+            HasCloseModifier) {
           if ((arg_types[i] & OMP_TGT_MAPTYPE_MEMBER_OF) &&
               !(arg_types[i] & OMP_TGT_MAPTYPE_PTR_AND_OBJ)) {
             // Copy data only if the "parent" struct has RefCount==1.
@@ -403,7 +411,7 @@
           }
         }
 
-        if ((DelEntry || Always || CopyMember) &&
+        if ((DelEntry || Always || CopyMember || HasCloseModifier) &&
             !(Device.RTLRequiresFlags & OMP_REQ_UNIFIED_SHARED_MEMORY &&
               TgtPtrBegin == HstPtrBegin)) {
           DP("Moving %" PRId64 " bytes (tgt:" DPxMOD ") -> (hst:" DPxMOD ")\n",
@@ -455,7 +463,8 @@
 
       // Deallocate map
       if (DelEntry) {
-        int rt = Device.deallocTgtPtr(HstPtrBegin, data_size, ForceDelete);
+        int rt = Device.deallocTgtPtr(HstPtrBegin, data_size, ForceDelete,
+                                      HasCloseModifier);
         if (rt != OFFLOAD_SUCCESS) {
           DP("Deallocating data from device failed.\n");
           return OFFLOAD_FAIL;
Index: libomptarget/test/unified_shared_memory/close_modifier.c
===================================================================
--- /dev/null
+++ libomptarget/test/unified_shared_memory/close_modifier.c
@@ -0,0 +1,143 @@
+// RUN: %libomptarget-compile-run-and-check-aarch64-unknown-linux-gnu
+// RUN: %libomptarget-compile-run-and-check-powerpc64-ibm-linux-gnu
+// RUN: %libomptarget-compile-run-and-check-powerpc64le-ibm-linux-gnu
+// RUN: %libomptarget-compile-run-and-check-x86_64-pc-linux-gnu
+
+#include <stdio.h>
+#include <omp.h>
+
+// ---------------------------------------------------------------------------
+// Various definitions copied from OpenMP RTL
+
+extern void __tgt_register_requires(int64_t);
+
+// End of definitions copied from OpenMP RTL.
+// ---------------------------------------------------------------------------
+
+#pragma omp requires unified_shared_memory
+
+#define N 1024
+
+int main(int argc, char *argv[]) {
+  int fails;
+  void *host_alloc, *device_alloc;
+  void *host_data, *device_data;
+  int *alloc = (int *)malloc(N*sizeof(int));
+  int data[N];
+
+  // Manual registration of requires flags for Clang versions
+  // that do not support requires.
+  __tgt_register_requires(8);
+
+  for (int i=0; i<N; ++i) {
+    alloc[i] = 10;
+    data[i] = 1;
+  }
+
+  host_data = &data[0];
+  host_alloc = &alloc[0];
+
+  //
+  // Test that updates on the device are not visible to host
+  // when only a TO mapping is used.
+  //
+  #pragma omp target map(tofrom: device_data, device_alloc) \
+                     map(close,to: alloc[:N], data[:N])
+  {
+    device_data = &data[0];
+    device_alloc = &alloc[0];
+
+    for (int i=0; i<N; i++) {
+      alloc[i] += 1;
+      data[i] += 1;
+    }
+  }
+
+  // CHECK: Address of alloc on device different from host address.
+  if (device_alloc != host_alloc)
+    printf("Address of alloc on device different from host address.\n");
+
+  // CHECK: Address of data on device different from host address.
+  if (device_data != host_data)
+    printf("Address of data on device different from host address.\n");
+
+  // On the host, check that the arrays have been updated.
+  // CHECK: Alloc host values not updated: Succeeded
+  fails = 0;
+  for (int i=0; i<N; i++) {
+    if (alloc[i] != 10)
+      fails++;
+  }
+  printf("Alloc host values not updated: %s\n",
+         (fails == 0) ? "Succeeded" : "Failed");
+
+  // CHECK: Data host values not updated: Succeeded
+  fails = 0;
+  for (int i=0; i<N; i++) {
+    if (data[i] != 1)
+      fails++;
+  }
+  printf("Data host values not updated: %s\n",
+         (fails == 0) ? "Succeeded" : "Failed");
+
+  //
+  // Test that updates on the device are visible on host
+  // when a from is used.
+  //
+
+  for (int i=0; i<N; i++) {
+    alloc[i] += 1;
+    data[i] += 1;
+  }
+
+  #pragma omp target map(close,tofrom: alloc[:N], data[:N])
+  {
+    // CHECK: Alloc device values are correct: Succeeded
+    fails = 0;
+    for (int i=0; i<N; i++) {
+      if (alloc[i] != 11)
+        fails++;
+    }
+    printf("Alloc device values are correct: %s\n",
+           (fails == 0) ? "Succeeded" : "Failed");
+    // CHECK: Data device values are correct: Succeeded
+    fails = 0;
+    for (int i=0; i<N; i++) {
+      if (data[i] != 2)
+        fails++;
+    }
+    printf("Data device values are correct: %s\n",
+           (fails == 0) ? "Succeeded" : "Failed");
+
+    // Update values on the device
+    for (int i=0; i<N; i++) {
+      alloc[i] += 1;
+      data[i] += 1;
+    }
+  }
+
+  // CHECK: Alloc host values updated: Succeeded
+  fails = 0;
+  for (int i=0; i<N; i++) {
+    if (alloc[i] != 12)
+      fails++;
+  }
+  printf("Alloc host values updated: %s\n",
+         (fails == 0) ? "Succeeded" : "Failed");
+
+  // CHECK: Data host values updated: Succeeded
+  fails = 0;
+  for (int i=0; i<N; i++) {
+    if (data[i] != 3)
+      fails++;
+  }
+  printf("Data host values updated: %s\n",
+         (fails == 0) ? "Succeeded" : "Failed");
+
+  free(alloc);
+
+  // CHECK: Done!
+  printf("Done!\n");
+
+  return 0;
+}