diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile
index e6abfa02d8b7b5c02e68c793e083bc15e3d6c4c0..0a74b5661186e6b6b8bc6dfbe01d4419bcf40c6a 100644
--- a/drivers/hv/Makefile
+++ b/drivers/hv/Makefile
@@ -5,4 +5,4 @@ obj-$(CONFIG_HYPERV_BALLOON)	+= hv_balloon.o
 hv_vmbus-y := vmbus_drv.o \
 		 hv.o connection.o channel.o \
 		 channel_mgmt.o ring_buffer.o
-hv_utils-y := hv_util.o hv_kvp.o
+hv_utils-y := hv_util.o hv_kvp.o hv_snapshot.o
diff --git a/drivers/hv/hv_snapshot.c b/drivers/hv/hv_snapshot.c
new file mode 100644
index 0000000000000000000000000000000000000000..8ad5653ce447897208c4be576cd16725f70267e1
--- /dev/null
+++ b/drivers/hv/hv_snapshot.c
@@ -0,0 +1,287 @@
+/*
+ * An implementation of host initiated guest snapshot.
+ *
+ *
+ * Copyright (C) 2013, Microsoft, Inc.
+ * Author : K. Y. Srinivasan <kys@microsoft.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/net.h>
+#include <linux/nls.h>
+#include <linux/connector.h>
+#include <linux/workqueue.h>
+#include <linux/hyperv.h>
+
+
+
+/*
+ * Global state maintained for transaction that is being processed.
+ * Note that only one transaction can be active at any point in time.
+ *
+ * This state is set when we receive a request from the host; we
+ * cleanup this state when the transaction is completed - when we respond
+ * to the host with the key value.
+ */
+
+static struct {
+	bool active; /* transaction status - active or not */
+	int recv_len; /* number of bytes received. */
+	struct vmbus_channel *recv_channel; /* chn we got the request */
+	u64 recv_req_id; /* request ID. */
+	struct hv_vss_msg  *msg; /* current message */
+} vss_transaction;
+
+
+static void vss_respond_to_host(int error);
+
+static struct cb_id vss_id = { CN_VSS_IDX, CN_VSS_VAL };
+static const char vss_name[] = "vss_kernel_module";
+static __u8 *recv_buffer;
+
+static void vss_send_op(struct work_struct *dummy);
+static DECLARE_WORK(vss_send_op_work, vss_send_op);
+
+/*
+ * Callback when data is received from user mode.
+ */
+
+static void
+vss_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
+{
+	struct hv_vss_msg *vss_msg;
+
+	vss_msg = (struct hv_vss_msg *)msg->data;
+
+	if (vss_msg->vss_hdr.operation == VSS_OP_REGISTER) {
+		pr_info("VSS daemon registered\n");
+		vss_transaction.active = false;
+		if (vss_transaction.recv_channel != NULL)
+			hv_vss_onchannelcallback(vss_transaction.recv_channel);
+		return;
+
+	}
+	vss_respond_to_host(vss_msg->error);
+}
+
+
+static void vss_send_op(struct work_struct *dummy)
+{
+	int op = vss_transaction.msg->vss_hdr.operation;
+	struct cn_msg *msg;
+	struct hv_vss_msg *vss_msg;
+
+	msg = kzalloc(sizeof(*msg) + sizeof(*vss_msg), GFP_ATOMIC);
+	if (!msg)
+		return;
+
+	vss_msg = (struct hv_vss_msg *)msg->data;
+
+	msg->id.idx =  CN_VSS_IDX;
+	msg->id.val = CN_VSS_VAL;
+
+	vss_msg->vss_hdr.operation = op;
+	msg->len = sizeof(struct hv_vss_msg);
+
+	cn_netlink_send(msg, 0, GFP_ATOMIC);
+	kfree(msg);
+
+	return;
+}
+
+/*
+ * Send a response back to the host.
+ */
+
+static void
+vss_respond_to_host(int error)
+{
+	struct icmsg_hdr *icmsghdrp;
+	u32	buf_len;
+	struct vmbus_channel *channel;
+	u64	req_id;
+
+	/*
+	 * If a transaction is not active; log and return.
+	 */
+
+	if (!vss_transaction.active) {
+		/*
+		 * This is a spurious call!
+		 */
+		pr_warn("VSS: Transaction not active\n");
+		return;
+	}
+	/*
+	 * Copy the global state for completing the transaction. Note that
+	 * only one transaction can be active at a time.
+	 */
+
+	buf_len = vss_transaction.recv_len;
+	channel = vss_transaction.recv_channel;
+	req_id = vss_transaction.recv_req_id;
+	vss_transaction.active = false;
+
+	icmsghdrp = (struct icmsg_hdr *)
+			&recv_buffer[sizeof(struct vmbuspipe_hdr)];
+
+	if (channel->onchannel_callback == NULL)
+		/*
+		 * We have raced with util driver being unloaded;
+		 * silently return.
+		 */
+		return;
+
+	icmsghdrp->status = error;
+
+	icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
+
+	vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
+				VM_PKT_DATA_INBAND, 0);
+
+}
+
+/*
+ * This callback is invoked when we get a VSS message from the host.
+ * The host ensures that only one VSS transaction can be active at a time.
+ */
+
+void hv_vss_onchannelcallback(void *context)
+{
+	struct vmbus_channel *channel = context;
+	u32 recvlen;
+	u64 requestid;
+	struct hv_vss_msg *vss_msg;
+
+
+	struct icmsg_hdr *icmsghdrp;
+	struct icmsg_negotiate *negop = NULL;
+
+	if (vss_transaction.active) {
+		/*
+		 * We will defer processing this callback once
+		 * the current transaction is complete.
+		 */
+		vss_transaction.recv_channel = channel;
+		return;
+	}
+
+	vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 2, &recvlen,
+			 &requestid);
+
+	if (recvlen > 0) {
+		icmsghdrp = (struct icmsg_hdr *)&recv_buffer[
+			sizeof(struct vmbuspipe_hdr)];
+
+		if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
+			vmbus_prep_negotiate_resp(icmsghdrp, negop,
+				 recv_buffer, MAX_SRV_VER, MAX_SRV_VER);
+			/*
+			 * We currently negotiate the highest number the
+			 * host has presented. If this version is not
+			 * atleast 5.0, reject.
+			 */
+			negop = (struct icmsg_negotiate *)&recv_buffer[
+				sizeof(struct vmbuspipe_hdr) +
+				sizeof(struct icmsg_hdr)];
+
+			if (negop->icversion_data[1].major < 5)
+				negop->icframe_vercnt = 0;
+		} else {
+			vss_msg = (struct hv_vss_msg *)&recv_buffer[
+				sizeof(struct vmbuspipe_hdr) +
+				sizeof(struct icmsg_hdr)];
+
+			/*
+			 * Stash away this global state for completing the
+			 * transaction; note transactions are serialized.
+			 */
+
+			vss_transaction.recv_len = recvlen;
+			vss_transaction.recv_channel = channel;
+			vss_transaction.recv_req_id = requestid;
+			vss_transaction.active = true;
+			vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
+
+			switch (vss_msg->vss_hdr.operation) {
+				/*
+				 * Initiate a "freeze/thaw"
+				 * operation in the guest.
+				 * We respond to the host once
+				 * the operation is complete.
+				 *
+				 * We send the message to the
+				 * user space daemon and the
+				 * operation is performed in
+				 * the daemon.
+				 */
+			case VSS_OP_FREEZE:
+			case VSS_OP_THAW:
+				schedule_work(&vss_send_op_work);
+				return;
+
+			case VSS_OP_HOT_BACKUP:
+				vss_msg->vss_cf.flags =
+					 VSS_HBU_NO_AUTO_RECOVERY;
+				vss_respond_to_host(0);
+				return;
+
+			case VSS_OP_GET_DM_INFO:
+				vss_msg->dm_info.flags = 0;
+				vss_respond_to_host(0);
+				return;
+
+			default:
+				vss_respond_to_host(0);
+				return;
+
+			}
+
+		}
+
+		icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
+			| ICMSGHDRFLAG_RESPONSE;
+
+		vmbus_sendpacket(channel, recv_buffer,
+				       recvlen, requestid,
+				       VM_PKT_DATA_INBAND, 0);
+	}
+
+}
+
+int
+hv_vss_init(struct hv_util_service *srv)
+{
+	int err;
+
+	err = cn_add_callback(&vss_id, vss_name, vss_cn_callback);
+	if (err)
+		return err;
+	recv_buffer = srv->recv_buffer;
+
+	/*
+	 * When this driver loads, the user level daemon that
+	 * processes the host requests may not yet be running.
+	 * Defer processing channel callbacks until the daemon
+	 * has registered.
+	 */
+	vss_transaction.active = true;
+	return 0;
+}
+
+void hv_vss_deinit(void)
+{
+	cn_del_callback(&vss_id);
+	cancel_work_sync(&vss_send_op_work);
+}
diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 1d4cbd8e8261ef3f46f71005315a39f4d6d2c680..2f561c5dfe249085c89e6328b390c0d414e332ce 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -49,6 +49,12 @@ static struct hv_util_service util_kvp = {
 	.util_deinit = hv_kvp_deinit,
 };
 
+static struct hv_util_service util_vss = {
+	.util_cb = hv_vss_onchannelcallback,
+	.util_init = hv_vss_init,
+	.util_deinit = hv_vss_deinit,
+};
+
 static void perform_shutdown(struct work_struct *dummy)
 {
 	orderly_poweroff(true);
@@ -339,6 +345,10 @@ static const struct hv_vmbus_device_id id_table[] = {
 	{ HV_KVP_GUID,
 	  .driver_data = (unsigned long)&util_kvp
 	},
+	/* VSS GUID */
+	{ HV_VSS_GUID,
+	  .driver_data = (unsigned long)&util_vss
+	},
 	{ },
 };
 
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index df77ba9a8166e8959e07c3dd1325b9e4c8fa99dd..95d0850584dad6dc13febbe13c91afbcb6f58b46 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -27,6 +27,63 @@
 
 #include <linux/types.h>
 
+
+/*
+ * Implementation of host controlled snapshot of the guest.
+ */
+
+#define VSS_OP_REGISTER 128
+
+enum hv_vss_op {
+	VSS_OP_CREATE = 0,
+	VSS_OP_DELETE,
+	VSS_OP_HOT_BACKUP,
+	VSS_OP_GET_DM_INFO,
+	VSS_OP_BU_COMPLETE,
+	/*
+	 * Following operations are only supported with IC version >= 5.0
+	 */
+	VSS_OP_FREEZE, /* Freeze the file systems in the VM */
+	VSS_OP_THAW, /* Unfreeze the file systems */
+	VSS_OP_AUTO_RECOVER,
+	VSS_OP_COUNT /* Number of operations, must be last */
+};
+
+
+/*
+ * Header for all VSS messages.
+ */
+struct hv_vss_hdr {
+	__u8 operation;
+	__u8 reserved[7];
+} __attribute__((packed));
+
+
+/*
+ * Flag values for the hv_vss_check_feature. Linux supports only
+ * one value.
+ */
+#define VSS_HBU_NO_AUTO_RECOVERY	0x00000005
+
+struct hv_vss_check_feature {
+	__u32 flags;
+} __attribute__((packed));
+
+struct hv_vss_check_dm_info {
+	__u32 flags;
+} __attribute__((packed));
+
+struct hv_vss_msg {
+	union {
+		struct hv_vss_hdr vss_hdr;
+		int error;
+	};
+	union {
+		struct hv_vss_check_feature vss_cf;
+		struct hv_vss_check_dm_info dm_info;
+	};
+} __attribute__((packed));
+
 /*
  * An implementation of HyperV key value pair (KVP) functionality for Linux.
  *
@@ -1252,6 +1309,14 @@ void vmbus_driver_unregister(struct hv_driver *hv_driver);
 			0xb9, 0x8b, 0x8b, 0xa1, 0xa1, 0xf3, 0xf9, 0x5a \
 		}
 
+/*
+ * VSS (Backup/Restore) GUID
+ */
+#define HV_VSS_GUID \
+	.guid = { \
+			0x29, 0x2e, 0xfa, 0x35, 0x23, 0xea, 0x36, 0x42, \
+			0x96, 0xae, 0x3a, 0x6e, 0xba, 0xcb, 0xa4,  0x40 \
+		}
 /*
  * Common header for Hyper-V ICs
  */
@@ -1356,6 +1421,10 @@ int hv_kvp_init(struct hv_util_service *);
 void hv_kvp_deinit(void);
 void hv_kvp_onchannelcallback(void *);
 
+int hv_vss_init(struct hv_util_service *);
+void hv_vss_deinit(void);
+void hv_vss_onchannelcallback(void *);
+
 /*
  * Negotiated version with the Host.
  */
diff --git a/include/uapi/linux/connector.h b/include/uapi/linux/connector.h
index 8761a0349c7436ec0728d569e0fb58d9240ece3b..4cb283505e457d002e3d3bffb33e1c9b7fb2357b 100644
--- a/include/uapi/linux/connector.h
+++ b/include/uapi/linux/connector.h
@@ -44,8 +44,11 @@
 #define CN_VAL_DRBD			0x1
 #define CN_KVP_IDX			0x9	/* HyperV KVP */
 #define CN_KVP_VAL			0x1	/* queries from the kernel */
+#define CN_VSS_IDX			0xA     /* HyperV VSS */
+#define CN_VSS_VAL			0x1     /* queries from the kernel */
 
-#define CN_NETLINK_USERS		10	/* Highest index + 1 */
+
+#define CN_NETLINK_USERS		11	/* Highest index + 1 */
 
 /*
  * Maximum connector's message size.
diff --git a/tools/hv/hv_vss_daemon.c b/tools/hv/hv_vss_daemon.c
new file mode 100644
index 0000000000000000000000000000000000000000..95269952aa9259664919846f3e0091ac961c94b6
--- /dev/null
+++ b/tools/hv/hv_vss_daemon.c
@@ -0,0 +1,220 @@
+/*
+ * An implementation of the host initiated guest snapshot for Hyper-V.
+ *
+ *
+ * Copyright (C) 2013, Microsoft, Inc.
+ * Author : K. Y. Srinivasan <kys@microsoft.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ */
+
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/poll.h>
+#include <linux/types.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <ctype.h>
+#include <errno.h>
+#include <arpa/inet.h>
+#include <linux/connector.h>
+#include <linux/hyperv.h>
+#include <linux/netlink.h>
+#include <syslog.h>
+
+static char vss_recv_buffer[4096];
+static char vss_send_buffer[4096];
+static struct sockaddr_nl addr;
+
+#ifndef SOL_NETLINK
+#define SOL_NETLINK 270
+#endif
+
+
+static int vss_operate(int operation)
+{
+	char *fs_op;
+	char cmd[512];
+	char buf[512];
+	FILE *file;
+	char *p;
+	char *x;
+	int error;
+
+	switch (operation) {
+	case VSS_OP_FREEZE:
+		fs_op = "-f ";
+		break;
+	case VSS_OP_THAW:
+		fs_op = "-u ";
+		break;
+	}
+
+	file = popen("mount | awk '/^\/dev\// { print $3}'", "r");
+	if (file == NULL)
+		return;
+
+	while ((p = fgets(buf, sizeof(buf), file)) != NULL) {
+		x = strchr(p, '\n');
+		*x = '\0';
+		if (!strncmp(p, "/", sizeof("/")))
+			continue;
+
+		sprintf(cmd, "%s %s %s", "fsfreeze ", fs_op, p);
+		syslog(LOG_INFO, "VSS cmd is %s\n", cmd);
+		error = system(cmd);
+	}
+	pclose(file);
+
+	sprintf(cmd, "%s %s %s", "fsfreeze ", fs_op, "/");
+	syslog(LOG_INFO, "VSS cmd is %s\n", cmd);
+	error = system(cmd);
+
+	return error;
+}
+
+static int netlink_send(int fd, struct cn_msg *msg)
+{
+	struct nlmsghdr *nlh;
+	unsigned int size;
+	struct msghdr message;
+	char buffer[64];
+	struct iovec iov[2];
+
+	size = NLMSG_SPACE(sizeof(struct cn_msg) + msg->len);
+
+	nlh = (struct nlmsghdr *)buffer;
+	nlh->nlmsg_seq = 0;
+	nlh->nlmsg_pid = getpid();
+	nlh->nlmsg_type = NLMSG_DONE;
+	nlh->nlmsg_len = NLMSG_LENGTH(size - sizeof(*nlh));
+	nlh->nlmsg_flags = 0;
+
+	iov[0].iov_base = nlh;
+	iov[0].iov_len = sizeof(*nlh);
+
+	iov[1].iov_base = msg;
+	iov[1].iov_len = size;
+
+	memset(&message, 0, sizeof(message));
+	message.msg_name = &addr;
+	message.msg_namelen = sizeof(addr);
+	message.msg_iov = iov;
+	message.msg_iovlen = 2;
+
+	return sendmsg(fd, &message, 0);
+}
+
+int main(void)
+{
+	int fd, len, nl_group;
+	int error;
+	struct cn_msg *message;
+	struct pollfd pfd;
+	struct nlmsghdr *incoming_msg;
+	struct cn_msg	*incoming_cn_msg;
+	int	op;
+	struct hv_vss_msg *vss_msg;
+
+	daemon(1, 0);
+	openlog("Hyper-V VSS", 0, LOG_USER);
+	syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
+
+	fd = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
+	if (fd < 0) {
+		syslog(LOG_ERR, "netlink socket creation failed; error:%d", fd);
+		exit(EXIT_FAILURE);
+	}
+	addr.nl_family = AF_NETLINK;
+	addr.nl_pad = 0;
+	addr.nl_pid = 0;
+	addr.nl_groups = 0;
+
+
+	error = bind(fd, (struct sockaddr *)&addr, sizeof(addr));
+	if (error < 0) {
+		syslog(LOG_ERR, "bind failed; error:%d", error);
+		close(fd);
+		exit(EXIT_FAILURE);
+	}
+	nl_group = CN_VSS_IDX;
+	setsockopt(fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &nl_group, sizeof(nl_group));
+	/*
+	 * Register ourselves with the kernel.
+	 */
+	message = (struct cn_msg *)vss_send_buffer;
+	message->id.idx = CN_VSS_IDX;
+	message->id.val = CN_VSS_VAL;
+	message->ack = 0;
+	vss_msg = (struct hv_vss_msg *)message->data;
+	vss_msg->vss_hdr.operation = VSS_OP_REGISTER;
+
+	message->len = sizeof(struct hv_vss_msg);
+
+	len = netlink_send(fd, message);
+	if (len < 0) {
+		syslog(LOG_ERR, "netlink_send failed; error:%d", len);
+		close(fd);
+		exit(EXIT_FAILURE);
+	}
+
+	pfd.fd = fd;
+
+	while (1) {
+		struct sockaddr *addr_p = (struct sockaddr *) &addr;
+		socklen_t addr_l = sizeof(addr);
+		pfd.events = POLLIN;
+		pfd.revents = 0;
+		poll(&pfd, 1, -1);
+
+		len = recvfrom(fd, vss_recv_buffer, sizeof(vss_recv_buffer), 0,
+				addr_p, &addr_l);
+
+		if (len < 0 || addr.nl_pid) {
+			syslog(LOG_ERR, "recvfrom failed; pid:%u error:%d %s",
+					addr.nl_pid, errno, strerror(errno));
+			close(fd);
+			return -1;
+		}
+
+		incoming_msg = (struct nlmsghdr *)vss_recv_buffer;
+
+		if (incoming_msg->nlmsg_type != NLMSG_DONE)
+			continue;
+
+		incoming_cn_msg = (struct cn_msg *)NLMSG_DATA(incoming_msg);
+		vss_msg = (struct hv_vss_msg *)incoming_cn_msg->data;
+		op = vss_msg->vss_hdr.operation;
+		error =  HV_S_OK;
+
+		switch (op) {
+		case VSS_OP_FREEZE:
+		case VSS_OP_THAW:
+			error = vss_operate(op);
+			if (error)
+				error = HV_E_FAIL;
+			break;
+		default:
+			syslog(LOG_ERR, "Illegal op:%d\n", op);
+		}
+		vss_msg->error = error;
+		len = netlink_send(fd, incoming_cn_msg);
+		if (len < 0) {
+			syslog(LOG_ERR, "net_link send failed; error:%d", len);
+			exit(EXIT_FAILURE);
+		}
+	}
+
+}