// 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
  ");
  	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
  ");
  }

  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
  ", 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
  ");

  		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
  ");

  			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
  ");

  		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
  ");

  		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
  ", 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.
  ");

  			vss_respond_to_host(HV_E_FAIL);
  			return;
  		}

  
  		pr_debug("VSS: Received request for op code: %d
  ",
  			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;

  	vmbus_recvpacket(channel, recv_buffer, HV_HYP_PAGE_SIZE * 2, &recvlen,

  			 &requestid);
  
  	if (recvlen > 0) {
  		icmsghdrp = (struct icmsg_hdr *)&recv_buffer[
  			sizeof(struct vmbuspipe_hdr)];
  
  		if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {

  			if (vmbus_prep_negotiate_resp(icmsghdrp,

  				 recv_buffer, fw_versions, FW_VER_COUNT,
  				 vss_versions, VSS_VER_COUNT,

  				 NULL, &vss_srv_version)) {
  
  				pr_info("VSS IC version %d.%d
  ",
  					vss_srv_version >> 16,
  					vss_srv_version & 0xFFFF);
  			}

  		} 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_req_id = requestid;

  			vss_transaction.msg = (struct hv_vss_msg *)vss_msg;

  			schedule_work(&vss_handle_request_work);
  			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.
  ");
  		return -ENOTSUPP;
  	}

  	recv_buffer = srv->recv_buffer;

  	vss_transaction.recv_channel = srv->channel;

  
  	/*
  	 * 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
  ");

  		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);

  }