[mirror_ubuntu-jammy-kernel.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
};

/*
 * 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, HV_HYP_PAGE_SIZE * 2, &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 = HV_HYP_PAGE_SIZE * 2;

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