diff --git a/src/hip_hcc_internal.h b/src/hip_hcc_internal.h
index 3ee14577b0..658cfbf576 100644
--- a/src/hip_hcc_internal.h
+++ b/src/hip_hcc_internal.h
@@ -1022,6 +1022,27 @@ inline std::ostream& operator<<(std::ostream& os, const ihipCtx_t* c) {
 namespace hip_internal {
 hipError_t memcpyAsync(void* dst, const void* src, size_t sizeBytes, hipMemcpyKind kind,
                        hipStream_t stream);
+
+hipError_t ihipHostMalloc(TlsData *tls, void** ptr, size_t sizeBytes, unsigned int flags);
+
+hipError_t ihipHostFree(TlsData *tls, void* ptr);
+
+};
+
+#define MAX_COOPERATIVE_GPUs 255
+
+// do not change these two structs without changing the device library
+struct mg_sync {
+    uint w0;
+    uint w1;
+};
+
+struct mg_info {
+    struct mg_sync *mgs;
+    uint grid_id;
+    uint num_grids;
+    ulong prev_sum;
+    ulong all_sum;
 };
 
 //---
diff --git a/src/hip_memory.cpp b/src/hip_memory.cpp
index 48b83287f3..c8369685ec 100644
--- a/src/hip_memory.cpp
+++ b/src/hip_memory.cpp
@@ -141,6 +141,103 @@ void* allocAndSharePtr(const char* msg, size_t sizeBytes, ihipCtx_t* ctx, bool s
     return ptr;
 }
 
+hipError_t ihipHostMalloc(TlsData *tls, void** ptr, size_t sizeBytes, unsigned int flags) {
+    hipError_t hip_status = hipSuccess;
+
+    if (HIP_SYNC_HOST_ALLOC) {
+        hipDeviceSynchronize();
+    }
+
+    auto ctx = ihipGetTlsDefaultCtx();
+    if ((ctx == nullptr) || (ptr == nullptr)) {
+        hip_status = hipErrorInvalidValue;
+    }
+    else if (sizeBytes == 0) {
+        hip_status = hipSuccess;
+        // TODO - should size of 0 return err or be siliently ignored?
+    } else {
+        unsigned trueFlags = flags;
+        if (flags == hipHostMallocDefault) {
+            // HCC/ROCM provide a modern system with unified memory and should set both of these
+            // flags by default:
+            trueFlags = hipHostMallocMapped | hipHostMallocPortable;
+        }
+
+
+        const unsigned supportedFlags = hipHostMallocPortable | hipHostMallocMapped |
+                                        hipHostMallocWriteCombined | hipHostMallocCoherent |
+                                        hipHostMallocNonCoherent;
+
+
+        const unsigned coherencyFlags = hipHostMallocCoherent | hipHostMallocNonCoherent;
+
+        if ((flags & ~supportedFlags) || ((flags & coherencyFlags) == coherencyFlags)) {
+            *ptr = nullptr;
+            // can't specify unsupported flags, can't specify both Coherent + NonCoherent
+            hip_status = hipErrorInvalidValue;
+        } else {
+            auto device = ctx->getWriteableDevice();
+#if (__hcc_workweek__ >= 19115)
+            //Avoid mapping host pinned memory to all devices by HCC
+            unsigned amFlags = amHostUnmapped;
+#else
+            unsigned amFlags = 0;
+#endif
+            if (flags & hipHostMallocCoherent) {
+                amFlags |= amHostCoherent;
+            } else if (flags & hipHostMallocNonCoherent) {
+                amFlags |= amHostNonCoherent;
+            } else {
+                // depends on env variables:
+                amFlags |= HIP_HOST_COHERENT ? amHostCoherent : amHostNonCoherent;
+            }
+
+
+            *ptr = hip_internal::allocAndSharePtr(
+                (amFlags & amHostCoherent) ? "finegrained_host" : "pinned_host", sizeBytes, ctx,
+                true  /*shareWithAll*/, amFlags, flags, 0);
+
+            if (sizeBytes && (*ptr == NULL)) {
+                hip_status = hipErrorMemoryAllocation;
+            }
+        }
+    }
+
+    if (HIP_SYNC_HOST_ALLOC) {
+        hipDeviceSynchronize();
+    }
+    return hip_status;
+}
+
+hipError_t ihipHostFree(TlsData *tls, void* ptr) {
+
+    // Synchronize to ensure all work has finished.
+    ihipGetTlsDefaultCtx()->locked_waitAllStreams();  // ignores non-blocking streams, this waits
+                                                      // for all activity to finish.
+
+    hipError_t hipStatus = hipErrorInvalidValue;
+    if (ptr) {
+        hc::accelerator acc;
+#if (__hcc_workweek__ >= 17332)
+        hc::AmPointerInfo amPointerInfo(NULL, NULL, NULL, 0, acc, 0, 0);
+#else
+        hc::AmPointerInfo amPointerInfo(NULL, NULL, 0, acc, 0, 0);
+#endif
+        am_status_t status = hc::am_memtracker_getinfo(&amPointerInfo, ptr);
+        if (status == AM_SUCCESS) {
+            if (amPointerInfo._hostPointer == ptr) {
+                hc::am_free(ptr);
+                hipStatus = hipSuccess;
+            }
+        }
+    } else {
+        // free NULL pointer succeeds and is common technique to initialize runtime
+        hipStatus = hipSuccess;
+    }
+
+    return hipStatus;
+}
+
 
 }  // end namespace hip_internal
 
@@ -301,79 +398,12 @@ hipError_t hipExtMallocWithFlags(void** ptr, size_t sizeBytes, unsigned int flag
     return ihipLogStatus(hip_status);
 }
 
-hipError_t ihipHostMalloc(TlsData *tls, void** ptr, size_t sizeBytes, unsigned int flags) {
-    hipError_t hip_status = hipSuccess;
-
-    if (HIP_SYNC_HOST_ALLOC) {
-        hipDeviceSynchronize();
-    }
-
-    auto ctx = ihipGetTlsDefaultCtx();
-    if ((ctx == nullptr) || (ptr == nullptr)) {
-        hip_status = hipErrorInvalidValue;
-    }
-    else if (sizeBytes == 0) {
-        hip_status = hipSuccess;
-        // TODO - should size of 0 return err or be siliently ignored?
-    } else {
-        unsigned trueFlags = flags;
-        if (flags == hipHostMallocDefault) {
-            // HCC/ROCM provide a modern system with unified memory and should set both of these
-            // flags by default:
-            trueFlags = hipHostMallocMapped | hipHostMallocPortable;
-        }
-
-
-        const unsigned supportedFlags = hipHostMallocPortable | hipHostMallocMapped |
-                                        hipHostMallocWriteCombined | hipHostMallocCoherent |
-                                        hipHostMallocNonCoherent;
-
-
-        const unsigned coherencyFlags = hipHostMallocCoherent | hipHostMallocNonCoherent;
-
-        if ((flags & ~supportedFlags) || ((flags & coherencyFlags) == coherencyFlags)) {
-            *ptr = nullptr;
-            // can't specify unsupported flags, can't specify both Coherent + NonCoherent
-            hip_status = hipErrorInvalidValue;
-        } else {
-            auto device = ctx->getWriteableDevice();
-#if (__hcc_workweek__ >= 19115)
-            //Avoid mapping host pinned memory to all devices by HCC
-            unsigned amFlags = amHostUnmapped;
-#else
-            unsigned amFlags = 0;
-#endif
-            if (flags & hipHostMallocCoherent) {
-                amFlags |= amHostCoherent;
-            } else if (flags & hipHostMallocNonCoherent) {
-                amFlags |= amHostNonCoherent;
-            } else {
-                // depends on env variables:
-                amFlags |= HIP_HOST_COHERENT ? amHostCoherent : amHostNonCoherent;
-            }
-
-
-            *ptr = hip_internal::allocAndSharePtr(
-                (amFlags & amHostCoherent) ? "finegrained_host" : "pinned_host", sizeBytes, ctx,
-                true  /*shareWithAll*/, amFlags, flags, 0);
-
-            if (sizeBytes && (*ptr == NULL)) {
-                hip_status = hipErrorMemoryAllocation;
-            }
-        }
-    }
-
-    if (HIP_SYNC_HOST_ALLOC) {
-        hipDeviceSynchronize();
-    }
-    return hip_status;
-}
 
 hipError_t hipHostMalloc(void** ptr, size_t sizeBytes, unsigned int flags) {
     HIP_INIT_SPECIAL_API(hipHostMalloc, (TRACE_MEM), ptr, sizeBytes, flags);
     HIP_SET_DEVICE();
     hipError_t hip_status = hipSuccess;
-    hip_status = ihipHostMalloc(tls, ptr, sizeBytes, flags);
+    hip_status = hip_internal::ihipHostMalloc(tls, ptr, sizeBytes, flags);
     return ihipLogStatus(hip_status);
 }
 
@@ -384,7 +414,7 @@ hipError_t hipMallocManaged(void** devPtr, size_t size, unsigned int flags) {
     if(flags != hipMemAttachGlobal)
         hip_status = hipErrorInvalidValue;
     else
-        hip_status = ihipHostMalloc(tls, devPtr, size, hipHostMallocDefault);
+        hip_status = hip_internal::ihipHostMalloc(tls, devPtr, size, hipHostMallocDefault);
     return ihipLogStatus(hip_status);
 }
 
@@ -2146,30 +2176,8 @@ hipError_t hipFree(void* ptr) {
 hipError_t hipHostFree(void* ptr) {
     HIP_INIT_SPECIAL_API(hipHostFree, (TRACE_MEM), ptr);
 
-    // Synchronize to ensure all work has finished.
-    ihipGetTlsDefaultCtx()->locked_waitAllStreams();  // ignores non-blocking streams, this waits
-                                                      // for all activity to finish.
-
-
-    hipError_t hipStatus = hipErrorInvalidValue;
-    if (ptr) {
-        hc::accelerator acc;
-#if (__hcc_workweek__ >= 17332)
-        hc::AmPointerInfo amPointerInfo(NULL, NULL, NULL, 0, acc, 0, 0);
-#else
-        hc::AmPointerInfo amPointerInfo(NULL, NULL, 0, acc, 0, 0);
-#endif
-        am_status_t status = hc::am_memtracker_getinfo(&amPointerInfo, ptr);
-        if (status == AM_SUCCESS) {
-            if (amPointerInfo._hostPointer == ptr) {
-                hc::am_free(ptr);
-                hipStatus = hipSuccess;
-            }
-        }
-    } else {
-        // free NULL pointer succeeds and is common technique to initialize runtime
-        hipStatus = hipSuccess;
-    }
+    hipError_t hipStatus = hipSuccess;
+    hipStatus = hip_internal::ihipHostFree(tls, ptr);
 
     return ihipLogStatus(hipStatus);
 };
diff --git a/src/hip_module.cpp b/src/hip_module.cpp
index b3afdd4ffe..ac239105b8 100644
--- a/src/hip_module.cpp
+++ b/src/hip_module.cpp
@@ -137,7 +137,8 @@ hipError_t ihipModuleLaunchKernel(TlsData *tls, hipFunction_t f, uint32_t global
                                   uint32_t localWorkSizeX, uint32_t localWorkSizeY,
                                   uint32_t localWorkSizeZ, size_t sharedMemBytes,
                                   hipStream_t hStream, void** kernelParams, void** extra,
-                                  hipEvent_t startEvent, hipEvent_t stopEvent, uint32_t flags, bool isStreamLocked = 0) {
+                                  hipEvent_t startEvent, hipEvent_t stopEvent, uint32_t flags, bool isStreamLocked = 0,
+                                  void** impCoopParams = 0) {
     using namespace hip_impl;
 
     auto ctx = ihipGetTlsDefaultCtx();
@@ -181,10 +182,17 @@ hipError_t ihipModuleLaunchKernel(TlsData *tls, hipFunction_t f, uint32_t global
             return hipErrorInvalidValue;
         }
 
-        // Insert 48-bytes at the end for implicit kernel arguments and fill with value zero.
+        // Insert 56-bytes at the end for implicit kernel arguments and fill with value zero.
         size_t padSize = (~kernargs.size() + 1) & (HIP_IMPLICIT_KERNARG_ALIGNMENT - 1);
         kernargs.insert(kernargs.end(), padSize + HIP_IMPLICIT_KERNARG_SIZE, 0);
 
+        if (impCoopParams) {
+            const auto p{static_cast<const char*>(*impCoopParams)};
+            // The sixth index is for multi-grid synchronization
+            kernargs.insert((kernargs.cend() - padSize - HIP_IMPLICIT_KERNARG_SIZE) + 6 * HIP_IMPLICIT_KERNARG_ALIGNMENT,
+                            p, p + HIP_IMPLICIT_KERNARG_ALIGNMENT);
+        }
+
         /*
           Kernel argument preparation.
         */
@@ -449,6 +457,10 @@ hipError_t hipLaunchCooperativeKernel(const void* f, dim3 gridDim,
         return ihipLogStatus(hipErrorLaunchFailure);
     }
 
+    size_t impCoopArg = 1;
+    void* impCoopParams[1];
+    impCoopParams[0] = &impCoopArg;
+
     // launch the main kernel
     result = ihipModuleLaunchKernel(tls, kd,
             gridDim.x * blockDimX.x,
@@ -456,7 +468,7 @@ hipError_t hipLaunchCooperativeKernel(const void* f, dim3 gridDim,
             gridDim.z * blockDimX.z,
             blockDimX.x, blockDimX.y, blockDimX.z,
             sharedMemBytes, stream, kernelParams, nullptr, nullptr,
-            nullptr, 0, true);
+            nullptr, 0, true, impCoopParams);
 
     stream->criticalData().unlock();
 #if (__hcc_workweek__ >= 19213)
@@ -472,7 +484,7 @@ hipError_t hipLaunchCooperativeKernelMultiDevice(hipLaunchParams* launchParamsLi
     HIP_INIT_API(hipLaunchCooperativeKernelMultiDevice, launchParamsList, numDevices, flags);
     hipError_t result;
 
-    if (numDevices > g_deviceCnt || launchParamsList == nullptr) {
+    if (numDevices > g_deviceCnt || launchParamsList == nullptr || numDevices > MAX_COOPERATIVE_GPUs) {
         return ihipLogStatus(hipErrorInvalidValue);
     }
 
@@ -523,6 +535,32 @@ hipError_t hipLaunchCooperativeKernelMultiDevice(hipLaunchParams* launchParamsLi
                 kargs.getHandle());
     }
 
+    mg_sync *mg_sync_ptr = 0;
+    mg_info *mg_info_ptr[MAX_COOPERATIVE_GPUs] = {0};
+
+    result = hip_internal::ihipHostMalloc(tls, (void **)&mg_sync_ptr, sizeof(mg_sync), hipHostMallocDefault);
+    if (result != hipSuccess) {
+        return ihipLogStatus(hipErrorInvalidValue);
+    }
+    mg_sync_ptr->w0 = 0;
+    mg_sync_ptr->w1 = 0;
+
+    uint all_sum = 0;
+    for (int i = 0; i < numDevices; ++i) {
+        result = hip_internal::ihipHostMalloc(tls, (void **)&mg_info_ptr[i], sizeof(mg_info), hipHostMallocDefault);
+        if (result != hipSuccess) {
+            hip_internal::ihipHostFree(tls, mg_sync_ptr);
+            for (int j = 0; j < i; ++j) {
+                hip_internal::ihipHostFree(tls, mg_info_ptr[j]);
+            }
+            return ihipLogStatus(hipErrorInvalidValue);
+        }
+        // calculate the sum of sizes of all grids
+        const hipLaunchParams& lp = launchParamsList[i];
+        all_sum += lp.blockDim.x * lp.blockDim.y * lp.blockDim.z *
+                   lp.gridDim.x  * lp.gridDim.y  * lp.gridDim.z;
+    }
+
     // lock all streams before launching the blit kernels for initializing the GWS and main kernels to each device
     for (int i = 0; i < numDevices; ++i) {
         LockedAccessor_StreamCrit_t streamCrit(launchParamsList[i].stream->criticalData(), false);
@@ -531,7 +569,7 @@ hipError_t hipLaunchCooperativeKernelMultiDevice(hipLaunchParams* launchParamsLi
 #endif
     }
 
-    // launch the init_gws kernel to initialize the GWS followed by launching the main kernels for each device
+    // launch the init_gws kernel to initialize the GWS for each device
     for (int i = 0; i < numDevices; ++i) {
         const hipLaunchParams& lp = launchParamsList[i];
 
@@ -549,8 +587,32 @@ hipError_t hipLaunchCooperativeKernelMultiDevice(hipLaunchParams* launchParamsLi
                 launchParamsList[j].stream->criticalData()._av.release_locked_hsa_queue();
 #endif
             }
+            hip_internal::ihipHostFree(tls, mg_sync_ptr);
+            for (int j = 0; j < numDevices; ++j) {
+                hip_internal::ihipHostFree(tls, mg_info_ptr[j]);
+            }
+
             return ihipLogStatus(hipErrorLaunchFailure);
         }
+    }
+
+    void* impCoopParams[1];
+    ulong prev_sum = 0;
+    // launch the main kernels for each device
+    for (int i = 0; i < numDevices; ++i) {
+        const hipLaunchParams& lp = launchParamsList[i];
+
+        //initialize and setup the implicit kernel argument for multi-grid sync
+        mg_info_ptr[i]->mgs       = mg_sync_ptr;
+        mg_info_ptr[i]->grid_id   = i;
+        mg_info_ptr[i]->num_grids = numDevices;
+        mg_info_ptr[i]->all_sum   = all_sum;
+        mg_info_ptr[i]->prev_sum  = prev_sum;
+        prev_sum += lp.blockDim.x * lp.blockDim.y * lp.blockDim.z *
+                    lp.gridDim.x  * lp.gridDim.y  * lp.gridDim.z;
+
+
+        impCoopParams[0] = &mg_info_ptr[i];
 
         result = ihipModuleLaunchKernel(tls, kds[i],
                 lp.gridDim.x * lp.blockDim.x,
@@ -559,7 +621,23 @@ hipError_t hipLaunchCooperativeKernelMultiDevice(hipLaunchParams* launchParamsLi
                 lp.blockDim.x, lp.blockDim.y,
                 lp.blockDim.z, lp.sharedMem,
                 lp.stream, lp.args, nullptr, nullptr, nullptr, 0,
-                true);
+                true, impCoopParams);
+
+        if (result != hipSuccess) {
+            for (int j = 0; j < numDevices; ++j) {
+                launchParamsList[j].stream->criticalData().unlock();
+#if (__hcc_workweek__ >= 19213)
+                launchParamsList[j].stream->criticalData()._av.release_locked_hsa_queue();
+#endif
+            }
+            hip_internal::ihipHostFree(tls, mg_sync_ptr);
+            for (int j = 0; j < numDevices; ++j) {
+                hip_internal::ihipHostFree(tls, mg_info_ptr[j]);
+            }
+
+            return ihipLogStatus(hipErrorLaunchFailure);
+        }
+
     }
 
     // unlock all streams
@@ -573,6 +651,11 @@ hipError_t hipLaunchCooperativeKernelMultiDevice(hipLaunchParams* launchParamsLi
     free(gwsKds);
     free(kds);
 
+    hip_internal::ihipHostFree(tls, mg_sync_ptr);
+    for (int j = 0; j < numDevices; ++j) {
+        hip_internal::ihipHostFree(tls, mg_info_ptr[j]);
+    }
+
     return ihipLogStatus(result);
 }