drivers/hv/hv_snapshot.c

   1 /*
   2  * An implementation of host initiated guest snapshot.
   3  *
   4  *
   5  * Copyright (C) 2013, Microsoft, Inc.
   6  * Author : K. Y. Srinivasan <kys@microsoft.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License version 2 as published
  10  * by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  15  * NON INFRINGEMENT.  See the GNU General Public License for more
  16  * details.
  17  *
  18  */
  19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  20
  21 #include <linux/net.h>
  22 #include <linux/nls.h>
  23 #include <linux/connector.h>
  24 #include <linux/workqueue.h>
  25 #include <linux/hyperv.h>
  26
  27 #define VSS_MAJOR  5
  28 #define VSS_MINOR  0
  29 #define VSS_VERSION    (VSS_MAJOR << 16 | VSS_MINOR)
  30
  31 #define VSS_USERSPACE_TIMEOUT (msecs_to_jiffies(10 * 1000))
  32
  33 /*
  34  * Global state maintained for transaction that is being processed.
  35  * Note that only one transaction can be active at any point in time.
  36  *
  37  * This state is set when we receive a request from the host; we
  38  * cleanup this state when the transaction is completed - when we respond
  39  * to the host with the key value.
  40  */
  41
  42 static struct {
  43         bool active; /* transaction status - active or not */
  44         int recv_len; /* number of bytes received. */
  45         struct vmbus_channel *recv_channel; /* chn we got the request */
  46         u64 recv_req_id; /* request ID. */
  47         struct hv_vss_msg  *msg; /* current message */
  48 } vss_transaction;
  49
  50
  51 static void vss_respond_to_host(int error);
  52
  53 static struct cb_id vss_id = { CN_VSS_IDX, CN_VSS_VAL };
  54 static const char vss_name[] = "vss_kernel_module";
  55 static __u8 *recv_buffer;
  56
  57 static void vss_send_op(struct work_struct *dummy);
  58 static void vss_timeout_func(struct work_struct *dummy);
  59
  60 static DECLARE_DELAYED_WORK(vss_timeout_work, vss_timeout_func);
  61 static DECLARE_WORK(vss_send_op_work, vss_send_op);
  62
  63 /*
  64  * Callback when data is received from user mode.
  65  */
  66
  67 static void vss_timeout_func(struct work_struct *dummy)
  68 {
  69         /*
  70          * Timeout waiting for userspace component to reply happened.
  71          */
  72         pr_warn("VSS: timeout waiting for daemon to reply\n");
  73         vss_respond_to_host(HV_E_FAIL);
  74 }
  75
  76 static void
  77 vss_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
  78 {
  79         struct hv_vss_msg *vss_msg;
  80
  81         vss_msg = (struct hv_vss_msg *)msg->data;
  82
  83         if (vss_msg->vss_hdr.operation == VSS_OP_REGISTER) {
  84                 pr_info("VSS daemon registered\n");
  85                 vss_transaction.active = false;
  86                 if (vss_transaction.recv_channel != NULL)
  87                         hv_vss_onchannelcallback(vss_transaction.recv_channel);
  88                 return;
  89
  90         }
  91         if (cancel_delayed_work_sync(&vss_timeout_work))
  92                 vss_respond_to_host(vss_msg->error);
  93 }
  94
  95
  96 static void vss_send_op(struct work_struct *dummy)
  97 {
  98         int op = vss_transaction.msg->vss_hdr.operation;
  99         struct cn_msg *msg;
 100         struct hv_vss_msg *vss_msg;
 101
 102         msg = kzalloc(sizeof(*msg) + sizeof(*vss_msg), GFP_ATOMIC);
 103         if (!msg)
 104                 return;
 105
 106         vss_msg = (struct hv_vss_msg *)msg->data;
 107
 108         msg->id.idx =  CN_VSS_IDX;
 109         msg->id.val = CN_VSS_VAL;
 110
 111         vss_msg->vss_hdr.operation = op;
 112         msg->len = sizeof(struct hv_vss_msg);
 113
 114         cn_netlink_send(msg, 0, 0, GFP_ATOMIC);
 115         kfree(msg);
 116
 117         return;
 118 }
 119
 120 /*
 121  * Send a response back to the host.
 122  */
 123
 124 static void
 125 vss_respond_to_host(int error)
 126 {
 127         struct icmsg_hdr *icmsghdrp;
 128         u32     buf_len;
 129         struct vmbus_channel *channel;
 130         u64     req_id;
 131
 132         /*
 133          * If a transaction is not active; log and return.
 134          */
 135
 136         if (!vss_transaction.active) {
 137                 /*
 138                  * This is a spurious call!
 139                  */
 140                 pr_warn("VSS: Transaction not active\n");
 141                 return;
 142         }
 143         /*
 144          * Copy the global state for completing the transaction. Note that
 145          * only one transaction can be active at a time.
 146          */
 147
 148         buf_len = vss_transaction.recv_len;
 149         channel = vss_transaction.recv_channel;
 150         req_id = vss_transaction.recv_req_id;
 151         vss_transaction.active = false;
 152
 153         icmsghdrp = (struct icmsg_hdr *)
 154                         &recv_buffer[sizeof(struct vmbuspipe_hdr)];
 155
 156         if (channel->onchannel_callback == NULL)
 157                 /*
 158                  * We have raced with util driver being unloaded;
 159                  * silently return.
 160                  */
 161                 return;
 162
 163         icmsghdrp->status = error;
 164
 165         icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
 166
 167         vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
 168                                 VM_PKT_DATA_INBAND, 0);
 169
 170 }
 171
 172 /*
 173  * This callback is invoked when we get a VSS message from the host.
 174  * The host ensures that only one VSS transaction can be active at a time.
 175  */
 176
 177 void hv_vss_onchannelcallback(void *context)
 178 {
 179         struct vmbus_channel *channel = context;
 180         u32 recvlen;
 181         u64 requestid;
 182         struct hv_vss_msg *vss_msg;
 183
 184
 185         struct icmsg_hdr *icmsghdrp;
 186         struct icmsg_negotiate *negop = NULL;
 187
 188         if (vss_transaction.active) {
 189                 /*
 190                  * We will defer processing this callback once
 191                  * the current transaction is complete.
 192                  */
 193                 vss_transaction.recv_channel = channel;
 194                 return;
 195         }
 196
 197         vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 2, &recvlen,
 198                          &requestid);
 199
 200         if (recvlen > 0) {
 201                 icmsghdrp = (struct icmsg_hdr *)&recv_buffer[
 202                         sizeof(struct vmbuspipe_hdr)];
 203
 204                 if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
 205                         vmbus_prep_negotiate_resp(icmsghdrp, negop,
 206                                  recv_buffer, UTIL_FW_VERSION,
 207                                  VSS_VERSION);
 208                 } else {
 209                         vss_msg = (struct hv_vss_msg *)&recv_buffer[
 210                                 sizeof(struct vmbuspipe_hdr) +
 211                                 sizeof(struct icmsg_hdr)];
 212
 213                         /*
 214                          * Stash away this global state for completing the
 215                          * transaction; note transactions are serialized.
 216                          */
 217
 218                         vss_transaction.recv_len = recvlen;
 219                         vss_transaction.recv_channel = channel;
 220                         vss_transaction.recv_req_id = requestid;
 221                         vss_transaction.active = true;
 222                         vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
 223
 224                         switch (vss_msg->vss_hdr.operation) {
 225                                 /*
 226                                  * Initiate a "freeze/thaw"
 227                                  * operation in the guest.
 228                                  * We respond to the host once
 229                                  * the operation is complete.
 230                                  *
 231                                  * We send the message to the
 232                                  * user space daemon and the
 233                                  * operation is performed in
 234                                  * the daemon.
 235                                  */
 236                         case VSS_OP_FREEZE:
 237                         case VSS_OP_THAW:
 238                                 schedule_work(&vss_send_op_work);
 239                                 schedule_delayed_work(&vss_timeout_work,
 240                                                       VSS_USERSPACE_TIMEOUT);
 241                                 return;
 242
 243                         case VSS_OP_HOT_BACKUP:
 244                                 vss_msg->vss_cf.flags =
 245                                          VSS_HBU_NO_AUTO_RECOVERY;
 246                                 vss_respond_to_host(0);
 247                                 return;
 248
 249                         case VSS_OP_GET_DM_INFO:
 250                                 vss_msg->dm_info.flags = 0;
 251                                 vss_respond_to_host(0);
 252                                 return;
 253
 254                         default:
 255                                 vss_respond_to_host(0);
 256                                 return;
 257
 258                         }
 259
 260                 }
 261
 262                 icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
 263                         | ICMSGHDRFLAG_RESPONSE;
 264
 265                 vmbus_sendpacket(channel, recv_buffer,
 266                                        recvlen, requestid,
 267                                        VM_PKT_DATA_INBAND, 0);
 268         }
 269
 270 }
 271
 272 int
 273 hv_vss_init(struct hv_util_service *srv)
 274 {
 275         int err;
 276
 277         err = cn_add_callback(&vss_id, vss_name, vss_cn_callback);
 278         if (err)
 279                 return err;
 280         recv_buffer = srv->recv_buffer;
 281
 282         /*
 283          * When this driver loads, the user level daemon that
 284          * processes the host requests may not yet be running.
 285          * Defer processing channel callbacks until the daemon
 286          * has registered.
 287          */
 288         vss_transaction.active = true;
 289         return 0;
 290 }
 291
 292 void hv_vss_deinit(void)
 293 {
 294         cn_del_callback(&vss_id);
 295         cancel_delayed_work_sync(&vss_timeout_work);
 296         cancel_work_sync(&vss_send_op_work);
 297 }