[linux-block.git] / drivers / hv / hv_snapshot.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * An implementation of host initiated guest snapshot.
 *
 * Copyright (C) 2013, Microsoft, Inc.
 * Author : K. Y. Srinivasan <kys@microsoft.com>
 */
#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>
#include <asm/hyperv-tlfs.h>

#include "hyperv_vmbus.h"
#include "hv_utils_transport.h"

#define VSS_MAJOR  5
#define VSS_MINOR  0
#define VSS_VERSION    (VSS_MAJOR << 16 | VSS_MINOR)

#define VSS_VER_COUNT 1
static const int vss_versions[] = {
	VSS_VERSION
};

#define FW_VER_COUNT 1
static const int fw_versions[] = {
	UTIL_FW_VERSION
};

/* See comment with struct hv_vss_msg regarding the max VMbus packet size */
#define VSS_MAX_PKT_SIZE (HV_HYP_PAGE_SIZE * 2)

/*
 * Timeout values are based on expecations from host
 */
#define VSS_FREEZE_TIMEOUT (15 * 60)

/*
 * Global state maintained for transaction that is being processed. For a class
 * of integration services, including the "VSS service", the specified protocol
 * is a "request/response" protocol which means that there can only be single
 * outstanding transaction from the host at any given point in time. We use
 * this to simplify memory management in this driver - we cache and process
 * only one message at a time.
 *
 * While the request/response protocol is guaranteed by the host, we further
 * ensure this by serializing packet processing in this driver - we do not
 * read additional packets from the VMBUs until the current packet is fully
 * handled.
 */

static struct {
	int state;   /* hvutil_device_state */
	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);

/*
 * This state maintains the version number registered by the daemon.
 */
static int dm_reg_value;

static const char vss_devname[] = "vmbus/hv_vss";
static __u8 *recv_buffer;
static struct hvutil_transport *hvt;

static void vss_timeout_func(struct work_struct *dummy);
static void vss_handle_request(struct work_struct *dummy);

static DECLARE_DELAYED_WORK(vss_timeout_work, vss_timeout_func);
static DECLARE_WORK(vss_handle_request_work, vss_handle_request);

static void vss_poll_wrapper(void *channel)
{
	/* Transaction is finished, reset the state here to avoid races. */
	vss_transaction.state = HVUTIL_READY;
	tasklet_schedule(&((struct vmbus_channel *)channel)->callback_event);
}

/*
 * Callback when data is received from user mode.
 */

static void vss_timeout_func(struct work_struct *dummy)
{
	/*
	 * Timeout waiting for userspace component to reply happened.
	 */
	pr_warn("VSS: timeout waiting for daemon to reply\n");
	vss_respond_to_host(HV_E_FAIL);

	hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
}

static void vss_register_done(void)
{
	hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
	pr_debug("VSS: userspace daemon registered\n");
}

static int vss_handle_handshake(struct hv_vss_msg *vss_msg)
{
	u32 our_ver = VSS_OP_REGISTER1;

	switch (vss_msg->vss_hdr.operation) {
	case VSS_OP_REGISTER:
		/* Daemon doesn't expect us to reply */
		dm_reg_value = VSS_OP_REGISTER;
		break;
	case VSS_OP_REGISTER1:
		/* Daemon expects us to reply with our own version */
		if (hvutil_transport_send(hvt, &our_ver, sizeof(our_ver),
					  vss_register_done))
			return -EFAULT;
		dm_reg_value = VSS_OP_REGISTER1;
		break;
	default:
		return -EINVAL;
	}
	pr_info("VSS: userspace daemon ver. %d connected\n", dm_reg_value);
	return 0;
}

static int vss_on_msg(void *msg, int len)
{
	struct hv_vss_msg *vss_msg = (struct hv_vss_msg *)msg;

	if (len != sizeof(*vss_msg)) {
		pr_debug("VSS: Message size does not match length\n");
		return -EINVAL;
	}

	if (vss_msg->vss_hdr.operation == VSS_OP_REGISTER ||
	    vss_msg->vss_hdr.operation == VSS_OP_REGISTER1) {
		/*
		 * Don't process registration messages if we're in the middle
		 * of a transaction processing.
		 */
		if (vss_transaction.state > HVUTIL_READY) {
			pr_debug("VSS: Got unexpected registration request\n");
			return -EINVAL;
		}

		return vss_handle_handshake(vss_msg);
	} else if (vss_transaction.state == HVUTIL_USERSPACE_REQ) {
		vss_transaction.state = HVUTIL_USERSPACE_RECV;

		if (vss_msg->vss_hdr.operation == VSS_OP_HOT_BACKUP)
			vss_transaction.msg->vss_cf.flags =
				VSS_HBU_NO_AUTO_RECOVERY;

		if (cancel_delayed_work_sync(&vss_timeout_work)) {
			vss_respond_to_host(vss_msg->error);
			/* Transaction is finished, reset the state. */
			hv_poll_channel(vss_transaction.recv_channel,
					vss_poll_wrapper);
		}
	} else {
		/* This is a spurious call! */
		pr_debug("VSS: Transaction not active\n");
		return -EINVAL;
	}
	return 0;
}

static void vss_send_op(void)
{
	int op = vss_transaction.msg->vss_hdr.operation;
	int rc;
	struct hv_vss_msg *vss_msg;

	/* The transaction state is wrong. */
	if (vss_transaction.state != HVUTIL_HOSTMSG_RECEIVED) {
		pr_debug("VSS: Unexpected attempt to send to daemon\n");
		return;
	}

	vss_msg = kzalloc(sizeof(*vss_msg), GFP_KERNEL);
	if (!vss_msg)
		return;

	vss_msg->vss_hdr.operation = op;

	vss_transaction.state = HVUTIL_USERSPACE_REQ;

	schedule_delayed_work(&vss_timeout_work, op == VSS_OP_FREEZE ?
			VSS_FREEZE_TIMEOUT * HZ : HV_UTIL_TIMEOUT * HZ);

	rc = hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg), NULL);
	if (rc) {
		pr_warn("VSS: failed to communicate to the daemon: %d\n", rc);
		if (cancel_delayed_work_sync(&vss_timeout_work)) {
			vss_respond_to_host(HV_E_FAIL);
			vss_transaction.state = HVUTIL_READY;
		}
	}

	kfree(vss_msg);
}

static void vss_handle_request(struct work_struct *dummy)
{
	switch (vss_transaction.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_THAW:
	case VSS_OP_FREEZE:
	case VSS_OP_HOT_BACKUP:
		if (vss_transaction.state < HVUTIL_READY) {
			/* Userspace is not registered yet */
			pr_debug("VSS: Not ready for request.\n");
			vss_respond_to_host(HV_E_FAIL);
			return;
		}

		pr_debug("VSS: Received request for op code: %d\n",
			vss_transaction.msg->vss_hdr.operation);
		vss_transaction.state = HVUTIL_HOSTMSG_RECEIVED;
		vss_send_op();
		return;
	case VSS_OP_GET_DM_INFO:
		vss_transaction.msg->dm_info.flags = 0;
		break;
	default:
		break;
	}

	vss_respond_to_host(0);
	hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
}

/*
 * 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;

	/*
	 * 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;

	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;
	int vss_srv_version;

	struct icmsg_hdr *icmsghdrp;

	if (vss_transaction.state > HVUTIL_READY)
		return;

	if (vmbus_recvpacket(channel, recv_buffer, VSS_MAX_PKT_SIZE, &recvlen, &requestid)) {
		pr_err_ratelimited("VSS request received. Could not read into recv buf\n");
		return;
	}

	if (!recvlen)
		return;

	/* Ensure recvlen is big enough to read header data */
	if (recvlen < ICMSG_HDR) {
		pr_err_ratelimited("VSS request received. Packet length too small: %d\n",
				   recvlen);
		return;
	}

	icmsghdrp = (struct icmsg_hdr *)&recv_buffer[sizeof(struct vmbuspipe_hdr)];

	if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
		if (vmbus_prep_negotiate_resp(icmsghdrp,
				recv_buffer, recvlen,
				fw_versions, FW_VER_COUNT,
				vss_versions, VSS_VER_COUNT,
				NULL, &vss_srv_version)) {

			pr_info("VSS IC version %d.%d\n",
				vss_srv_version >> 16,
				vss_srv_version & 0xFFFF);
		}
	} else if (icmsghdrp->icmsgtype == ICMSGTYPE_VSS) {
		/* Ensure recvlen is big enough to contain hv_vss_msg */
		if (recvlen < ICMSG_HDR + sizeof(struct hv_vss_msg)) {
			pr_err_ratelimited("Invalid VSS msg. Packet length too small: %u\n",
					   recvlen);
			return;
		}
		vss_msg = (struct hv_vss_msg *)&recv_buffer[ICMSG_HDR];

		/*
		 * Stash away this global state for completing the
		 * transaction; note transactions are serialized.
		 */

		vss_transaction.recv_len = recvlen;
		vss_transaction.recv_req_id = requestid;
		vss_transaction.msg = (struct hv_vss_msg *)vss_msg;

		schedule_work(&vss_handle_request_work);
		return;
	} else {
		pr_err_ratelimited("VSS request received. Invalid msg type: %d\n",
				   icmsghdrp->icmsgtype);
		return;
	}

	icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION |
		ICMSGHDRFLAG_RESPONSE;
	vmbus_sendpacket(channel, recv_buffer, recvlen, requestid,
			 VM_PKT_DATA_INBAND, 0);
}

static void vss_on_reset(void)
{
	if (cancel_delayed_work_sync(&vss_timeout_work))
		vss_respond_to_host(HV_E_FAIL);
	vss_transaction.state = HVUTIL_DEVICE_INIT;
}

int
hv_vss_init(struct hv_util_service *srv)
{
	if (vmbus_proto_version < VERSION_WIN8_1) {
		pr_warn("Integration service 'Backup (volume snapshot)'"
			" not supported on this host version.\n");
		return -ENOTSUPP;
	}
	recv_buffer = srv->recv_buffer;
	vss_transaction.recv_channel = srv->channel;
	vss_transaction.recv_channel->max_pkt_size = VSS_MAX_PKT_SIZE;

	/*
	 * 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.state = HVUTIL_DEVICE_INIT;

	hvt = hvutil_transport_init(vss_devname, CN_VSS_IDX, CN_VSS_VAL,
				    vss_on_msg, vss_on_reset);
	if (!hvt) {
		pr_warn("VSS: Failed to initialize transport\n");
		return -EFAULT;
	}

	return 0;
}

static void hv_vss_cancel_work(void)
{
	cancel_delayed_work_sync(&vss_timeout_work);
	cancel_work_sync(&vss_handle_request_work);
}

int hv_vss_pre_suspend(void)
{
	struct vmbus_channel *channel = vss_transaction.recv_channel;
	struct hv_vss_msg *vss_msg;

	/*
	 * Fake a THAW message for the user space daemon in case the daemon
	 * has frozen the file systems. It doesn't matter if there is already
	 * a message pending to be delivered to the user space since we force
	 * vss_transaction.state to be HVUTIL_READY, so the user space daemon's
	 * write() will fail with EINVAL (see vss_on_msg()), and the daemon
	 * will reset the device by closing and re-opening it.
	 */
	vss_msg = kzalloc(sizeof(*vss_msg), GFP_KERNEL);
	if (!vss_msg)
		return -ENOMEM;

	tasklet_disable(&channel->callback_event);

	vss_msg->vss_hdr.operation = VSS_OP_THAW;

	/* Cancel any possible pending work. */
	hv_vss_cancel_work();

	/* We don't care about the return value. */
	hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg), NULL);

	kfree(vss_msg);

	vss_transaction.state = HVUTIL_READY;

	/* tasklet_enable() will be called in hv_vss_pre_resume(). */
	return 0;
}

int hv_vss_pre_resume(void)
{
	struct vmbus_channel *channel = vss_transaction.recv_channel;

	tasklet_enable(&channel->callback_event);

	return 0;
}

void hv_vss_deinit(void)
{
	vss_transaction.state = HVUTIL_DEVICE_DYING;

	hv_vss_cancel_work();

	hvutil_transport_destroy(hvt);
}
Commit	Line	Data
43aa3132	1	// SPDX-License-Identifier: GPL-2.0-only
96dd86fa S	2	/*
	3	* An implementation of host initiated guest snapshot.
	4	*
96dd86fa S	5	* Copyright (C) 2013, Microsoft, Inc.
96dd86fa S	6	* Author : K. Y. Srinivasan <kys@microsoft.com>
96dd86fa S	7	*/
	8	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
	9
	10	#include <linux/net.h>
	11	#include <linux/nls.h>
	12	#include <linux/connector.h>
	13	#include <linux/workqueue.h>
	14	#include <linux/hyperv.h>
b14d749a	15	#include <asm/hyperv-tlfs.h>
96dd86fa	16
3647a83d	17	#include "hyperv_vmbus.h"
6472f80a	18	#include "hv_utils_transport.h"
3647a83d	19
6741335b S	20	#define VSS_MAJOR 5
6741335b S	21	#define VSS_MINOR 0
3a491605	22	#define VSS_VERSION (VSS_MAJOR << 16 \| VSS_MINOR)
6741335b	23
a1656454 AN	24	#define VSS_VER_COUNT 1
	25	static const int vss_versions[] = {
	26	VSS_VERSION
	27	};
	28
	29	#define FW_VER_COUNT 1
	30	static const int fw_versions[] = {
	31	UTIL_FW_VERSION
	32	};
	33
6de74d10 MK	34	/* See comment with struct hv_vss_msg regarding the max VMbus packet size */
	35	#define VSS_MAX_PKT_SIZE (HV_HYP_PAGE_SIZE * 2)
	36
b357fd39 AN	37	/*
	38	* Timeout values are based on expecations from host
	39	*/
	40	#define VSS_FREEZE_TIMEOUT (15 * 60)
96dd86fa S	41
96dd86fa S	42	/*
086a6f68 VK	43	* Global state maintained for transaction that is being processed. For a class
	44	* of integration services, including the "VSS service", the specified protocol
	45	* is a "request/response" protocol which means that there can only be single
	46	* outstanding transaction from the host at any given point in time. We use
	47	* this to simplify memory management in this driver - we cache and process
	48	* only one message at a time.
96dd86fa	49	*
086a6f68 VK	50	* While the request/response protocol is guaranteed by the host, we further
	51	* ensure this by serializing packet processing in this driver - we do not
	52	* read additional packets from the VMBUs until the current packet is fully
	53	* handled.
96dd86fa S	54	*/
	55
	56	static struct {
086a6f68	57	int state; /* hvutil_device_state */
96dd86fa S	58	int recv_len; /* number of bytes received. */
	59	struct vmbus_channel recv_channel; / chn we got the request */
	60	u64 recv_req_id; /* request ID. */
	61	struct hv_vss_msg msg; / current message */
	62	} vss_transaction;
	63
	64
	65	static void vss_respond_to_host(int error);
	66
cd8dc054 VK	67	/*
	68	* This state maintains the version number registered by the daemon.
	69	*/
	70	static int dm_reg_value;
	71
6472f80a	72	static const char vss_devname[] = "vmbus/hv_vss";
96dd86fa	73	static __u8 *recv_buffer;
6472f80a	74	static struct hvutil_transport *hvt;
96dd86fa	75
64914207	76	static void vss_timeout_func(struct work_struct *dummy);
497af84b	77	static void vss_handle_request(struct work_struct *dummy);
64914207 VK	78
64914207 VK	79	static DECLARE_DELAYED_WORK(vss_timeout_work, vss_timeout_func);
497af84b	80	static DECLARE_WORK(vss_handle_request_work, vss_handle_request);
96dd86fa	81
3cace4a6 OH	82	static void vss_poll_wrapper(void *channel)
	83	{
	84	/* Transaction is finished, reset the state here to avoid races. */
	85	vss_transaction.state = HVUTIL_READY;
238d2ed8	86	tasklet_schedule(&((struct vmbus_channel *)channel)->callback_event);
3cace4a6 OH	87	}
3cace4a6 OH	88
96dd86fa S	89	/*
	90	* Callback when data is received from user mode.
	91	*/
	92
64914207 VK	93	static void vss_timeout_func(struct work_struct *dummy)
	94	{
	95	/*
	96	* Timeout waiting for userspace component to reply happened.
	97	*/
	98	pr_warn("VSS: timeout waiting for daemon to reply\n");
	99	vss_respond_to_host(HV_E_FAIL);
38c06c29	100
3cace4a6	101	hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
64914207 VK	102	}
64914207 VK	103
e0fa3e5e VK	104	static void vss_register_done(void)
	105	{
	106	hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
	107	pr_debug("VSS: userspace daemon registered\n");
	108	}
	109
cd8dc054 VK	110	static int vss_handle_handshake(struct hv_vss_msg *vss_msg)
	111	{
	112	u32 our_ver = VSS_OP_REGISTER1;
	113
	114	switch (vss_msg->vss_hdr.operation) {
	115	case VSS_OP_REGISTER:
	116	/* Daemon doesn't expect us to reply */
	117	dm_reg_value = VSS_OP_REGISTER;
	118	break;
	119	case VSS_OP_REGISTER1:
e0fa3e5e VK	120	/* Daemon expects us to reply with our own version */
	121	if (hvutil_transport_send(hvt, &our_ver, sizeof(our_ver),
	122	vss_register_done))
cd8dc054 VK	123	return -EFAULT;
	124	dm_reg_value = VSS_OP_REGISTER1;
	125	break;
	126	default:
	127	return -EINVAL;
	128	}
23d2cc0c	129	pr_info("VSS: userspace daemon ver. %d connected\n", dm_reg_value);
cd8dc054 VK	130	return 0;
	131	}
	132
6472f80a	133	static int vss_on_msg(void *msg, int len)
96dd86fa	134	{
6472f80a	135	struct hv_vss_msg vss_msg = (struct hv_vss_msg )msg;
96dd86fa	136
23d2cc0c AN	137	if (len != sizeof(*vss_msg)) {
23d2cc0c AN	138	pr_debug("VSS: Message size does not match length\n");
6472f80a	139	return -EINVAL;
23d2cc0c	140	}
96dd86fa	141
cd8dc054 VK	142	if (vss_msg->vss_hdr.operation == VSS_OP_REGISTER \|\|
	143	vss_msg->vss_hdr.operation == VSS_OP_REGISTER1) {
	144	/*
	145	* Don't process registration messages if we're in the middle
	146	* of a transaction processing.
	147	*/
23d2cc0c AN	148	if (vss_transaction.state > HVUTIL_READY) {
23d2cc0c AN	149	pr_debug("VSS: Got unexpected registration request\n");
cd8dc054	150	return -EINVAL;
23d2cc0c AN	151	}
23d2cc0c AN	152
cd8dc054	153	return vss_handle_handshake(vss_msg);
086a6f68 VK	154	} else if (vss_transaction.state == HVUTIL_USERSPACE_REQ) {
086a6f68 VK	155	vss_transaction.state = HVUTIL_USERSPACE_RECV;
db886e4d AN	156
	157	if (vss_msg->vss_hdr.operation == VSS_OP_HOT_BACKUP)
	158	vss_transaction.msg->vss_cf.flags =
	159	VSS_HBU_NO_AUTO_RECOVERY;
	160
086a6f68 VK	161	if (cancel_delayed_work_sync(&vss_timeout_work)) {
	162	vss_respond_to_host(vss_msg->error);
	163	/* Transaction is finished, reset the state. */
3cace4a6 OH	164	hv_poll_channel(vss_transaction.recv_channel,
3cace4a6 OH	165	vss_poll_wrapper);
086a6f68 VK	166	}
	167	} else {
	168	/* This is a spurious call! */
23d2cc0c	169	pr_debug("VSS: Transaction not active\n");
6472f80a	170	return -EINVAL;
96dd86fa	171	}
6472f80a	172	return 0;
96dd86fa S	173	}
96dd86fa S	174
497af84b	175	static void vss_send_op(void)
96dd86fa S	176	{
96dd86fa S	177	int op = vss_transaction.msg->vss_hdr.operation;
8d9560eb	178	int rc;
96dd86fa S	179	struct hv_vss_msg *vss_msg;
96dd86fa S	180
086a6f68	181	/* The transaction state is wrong. */
23d2cc0c AN	182	if (vss_transaction.state != HVUTIL_HOSTMSG_RECEIVED) {
23d2cc0c AN	183	pr_debug("VSS: Unexpected attempt to send to daemon\n");
086a6f68	184	return;
23d2cc0c	185	}
086a6f68	186
6472f80a VK	187	vss_msg = kzalloc(sizeof(*vss_msg), GFP_KERNEL);
6472f80a VK	188	if (!vss_msg)
96dd86fa S	189	return;
96dd86fa S	190
96dd86fa	191	vss_msg->vss_hdr.operation = op;
96dd86fa	192
086a6f68	193	vss_transaction.state = HVUTIL_USERSPACE_REQ;
497af84b	194
b357fd39 AN	195	schedule_delayed_work(&vss_timeout_work, op == VSS_OP_FREEZE ?
b357fd39 AN	196	VSS_FREEZE_TIMEOUT * HZ : HV_UTIL_TIMEOUT * HZ);
497af84b	197
e0fa3e5e	198	rc = hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg), NULL);
8d9560eb VK	199	if (rc) {
8d9560eb VK	200	pr_warn("VSS: failed to communicate to the daemon: %d\n", rc);
086a6f68	201	if (cancel_delayed_work_sync(&vss_timeout_work)) {
8d9560eb	202	vss_respond_to_host(HV_E_FAIL);
086a6f68 VK	203	vss_transaction.state = HVUTIL_READY;
086a6f68 VK	204	}
8d9560eb	205	}
086a6f68	206
6472f80a	207	kfree(vss_msg);
96dd86fa S	208	}
96dd86fa S	209
497af84b AN	210	static void vss_handle_request(struct work_struct *dummy)
	211	{
	212	switch (vss_transaction.msg->vss_hdr.operation) {
	213	/*
	214	* Initiate a "freeze/thaw" operation in the guest.
	215	* We respond to the host once the operation is complete.
	216	*
	217	* We send the message to the user space daemon and the operation is
	218	* performed in the daemon.
	219	*/
	220	case VSS_OP_THAW:
	221	case VSS_OP_FREEZE:
db886e4d	222	case VSS_OP_HOT_BACKUP:
497af84b AN	223	if (vss_transaction.state < HVUTIL_READY) {
497af84b AN	224	/* Userspace is not registered yet */
23d2cc0c	225	pr_debug("VSS: Not ready for request.\n");
497af84b AN	226	vss_respond_to_host(HV_E_FAIL);
	227	return;
	228	}
23d2cc0c AN	229
	230	pr_debug("VSS: Received request for op code: %d\n",
	231	vss_transaction.msg->vss_hdr.operation);
497af84b AN	232	vss_transaction.state = HVUTIL_HOSTMSG_RECEIVED;
	233	vss_send_op();
	234	return;
497af84b AN	235	case VSS_OP_GET_DM_INFO:
	236	vss_transaction.msg->dm_info.flags = 0;
	237	break;
	238	default:
	239	break;
	240	}
	241
	242	vss_respond_to_host(0);
	243	hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
	244	}
	245
96dd86fa S	246	/*
	247	* Send a response back to the host.
	248	*/
	249
	250	static void
	251	vss_respond_to_host(int error)
	252	{
	253	struct icmsg_hdr *icmsghdrp;
	254	u32 buf_len;
	255	struct vmbus_channel *channel;
	256	u64 req_id;
	257
96dd86fa S	258	/*
	259	* Copy the global state for completing the transaction. Note that
	260	* only one transaction can be active at a time.
	261	*/
	262
	263	buf_len = vss_transaction.recv_len;
	264	channel = vss_transaction.recv_channel;
	265	req_id = vss_transaction.recv_req_id;
96dd86fa S	266
	267	icmsghdrp = (struct icmsg_hdr *)
	268	&recv_buffer[sizeof(struct vmbuspipe_hdr)];
	269
	270	if (channel->onchannel_callback == NULL)
	271	/*
	272	* We have raced with util driver being unloaded;
	273	* silently return.
	274	*/
	275	return;
	276
	277	icmsghdrp->status = error;
	278
	279	icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION \| ICMSGHDRFLAG_RESPONSE;
	280
	281	vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
	282	VM_PKT_DATA_INBAND, 0);
	283
	284	}
	285
	286	/*
	287	* This callback is invoked when we get a VSS message from the host.
	288	* The host ensures that only one VSS transaction can be active at a time.
	289	*/
	290
	291	void hv_vss_onchannelcallback(void *context)
	292	{
	293	struct vmbus_channel *channel = context;
	294	u32 recvlen;
	295	u64 requestid;
	296	struct hv_vss_msg *vss_msg;
1274a690	297	int vss_srv_version;
96dd86fa S	298
96dd86fa S	299	struct icmsg_hdr *icmsghdrp;
96dd86fa	300
3cace4a6	301	if (vss_transaction.state > HVUTIL_READY)
96dd86fa	302	return;
96dd86fa	303
6de74d10	304	if (vmbus_recvpacket(channel, recv_buffer, VSS_MAX_PKT_SIZE, &recvlen, &requestid)) {
06caa778 AB	305	pr_err_ratelimited("VSS request received. Could not read into recv buf\n");
	306	return;
	307	}
	308
	309	if (!recvlen)
	310	return;
	311
	312	/* Ensure recvlen is big enough to read header data */
	313	if (recvlen < ICMSG_HDR) {
	314	pr_err_ratelimited("VSS request received. Packet length too small: %d\n",
	315	recvlen);
	316	return;
	317	}
	318
	319	icmsghdrp = (struct icmsg_hdr *)&recv_buffer[sizeof(struct vmbuspipe_hdr)];
	320
	321	if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
	322	if (vmbus_prep_negotiate_resp(icmsghdrp,
	323	recv_buffer, recvlen,
	324	fw_versions, FW_VER_COUNT,
	325	vss_versions, VSS_VER_COUNT,
	326	NULL, &vss_srv_version)) {
	327
	328	pr_info("VSS IC version %d.%d\n",
	329	vss_srv_version >> 16,
	330	vss_srv_version & 0xFFFF);
	331	}
	332	} else if (icmsghdrp->icmsgtype == ICMSGTYPE_VSS) {
	333	/* Ensure recvlen is big enough to contain hv_vss_msg */
	334	if (recvlen < ICMSG_HDR + sizeof(struct hv_vss_msg)) {
	335	pr_err_ratelimited("Invalid VSS msg. Packet length too small: %u\n",
	336	recvlen);
497af84b	337	return;
96dd86fa	338	}
06caa778 AB	339	vss_msg = (struct hv_vss_msg *)&recv_buffer[ICMSG_HDR];
	340
	341	/*
	342	* Stash away this global state for completing the
	343	* transaction; note transactions are serialized.
	344	*/
96dd86fa	345
06caa778 AB	346	vss_transaction.recv_len = recvlen;
	347	vss_transaction.recv_req_id = requestid;
	348	vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
96dd86fa	349
06caa778 AB	350	schedule_work(&vss_handle_request_work);
	351	return;
	352	} else {
	353	pr_err_ratelimited("VSS request received. Invalid msg type: %d\n",
	354	icmsghdrp->icmsgtype);
	355	return;
96dd86fa S	356	}
96dd86fa S	357
06caa778 AB	358	icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION \|
	359	ICMSGHDRFLAG_RESPONSE;
	360	vmbus_sendpacket(channel, recv_buffer, recvlen, requestid,
	361	VM_PKT_DATA_INBAND, 0);
96dd86fa S	362	}
96dd86fa S	363
6472f80a VK	364	static void vss_on_reset(void)
	365	{
	366	if (cancel_delayed_work_sync(&vss_timeout_work))
	367	vss_respond_to_host(HV_E_FAIL);
	368	vss_transaction.state = HVUTIL_DEVICE_INIT;
	369	}
	370
96dd86fa S	371	int
	372	hv_vss_init(struct hv_util_service *srv)
	373	{
ed9ba608 OH	374	if (vmbus_proto_version < VERSION_WIN8_1) {
	375	pr_warn("Integration service 'Backup (volume snapshot)'"
	376	" not supported on this host version.\n");
	377	return -ENOTSUPP;
	378	}
96dd86fa	379	recv_buffer = srv->recv_buffer;
b9830d12	380	vss_transaction.recv_channel = srv->channel;
6de74d10	381	vss_transaction.recv_channel->max_pkt_size = VSS_MAX_PKT_SIZE;
96dd86fa S	382
	383	/*
	384	* When this driver loads, the user level daemon that
	385	* processes the host requests may not yet be running.
	386	* Defer processing channel callbacks until the daemon
	387	* has registered.
	388	*/
086a6f68 VK	389	vss_transaction.state = HVUTIL_DEVICE_INIT;
086a6f68 VK	390
6472f80a VK	391	hvt = hvutil_transport_init(vss_devname, CN_VSS_IDX, CN_VSS_VAL,
6472f80a VK	392	vss_on_msg, vss_on_reset);
23d2cc0c AN	393	if (!hvt) {
23d2cc0c AN	394	pr_warn("VSS: Failed to initialize transport\n");
6472f80a	395	return -EFAULT;
23d2cc0c	396	}
6472f80a	397
96dd86fa S	398	return 0;
	399	}
	400
54e19d34	401	static void hv_vss_cancel_work(void)
96dd86fa	402	{
64914207	403	cancel_delayed_work_sync(&vss_timeout_work);
497af84b	404	cancel_work_sync(&vss_handle_request_work);
54e19d34 DC	405	}
	406
	407	int hv_vss_pre_suspend(void)
	408	{
	409	struct vmbus_channel *channel = vss_transaction.recv_channel;
	410	struct hv_vss_msg *vss_msg;
	411
	412	/*
	413	* Fake a THAW message for the user space daemon in case the daemon
	414	* has frozen the file systems. It doesn't matter if there is already
	415	* a message pending to be delivered to the user space since we force
	416	* vss_transaction.state to be HVUTIL_READY, so the user space daemon's
	417	* write() will fail with EINVAL (see vss_on_msg()), and the daemon
	418	* will reset the device by closing and re-opening it.
	419	*/
	420	vss_msg = kzalloc(sizeof(*vss_msg), GFP_KERNEL);
	421	if (!vss_msg)
	422	return -ENOMEM;
	423
	424	tasklet_disable(&channel->callback_event);
	425
	426	vss_msg->vss_hdr.operation = VSS_OP_THAW;
	427
	428	/* Cancel any possible pending work. */
	429	hv_vss_cancel_work();
	430
	431	/* We don't care about the return value. */
	432	hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg), NULL);
	433
	434	kfree(vss_msg);
	435
	436	vss_transaction.state = HVUTIL_READY;
	437
	438	/* tasklet_enable() will be called in hv_vss_pre_resume(). */
	439	return 0;
	440	}
	441
	442	int hv_vss_pre_resume(void)
	443	{
	444	struct vmbus_channel *channel = vss_transaction.recv_channel;
	445
	446	tasklet_enable(&channel->callback_event);
	447
	448	return 0;
	449	}
	450
	451	void hv_vss_deinit(void)
	452	{
	453	vss_transaction.state = HVUTIL_DEVICE_DYING;
	454
	455	hv_vss_cancel_work();
	456
6472f80a	457	hvutil_transport_destroy(hvt);
96dd86fa	458	}