drivers/hv/hv_snapshot.c

   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
  16 #include "hyperv_vmbus.h"
  17 #include "hv_utils_transport.h"
  18
  19 #define VSS_MAJOR  5
  20 #define VSS_MINOR  0
  21 #define VSS_VERSION    (VSS_MAJOR << 16 | VSS_MINOR)
  22
  23 #define VSS_VER_COUNT 1
  24 static const int vss_versions[] = {
  25         VSS_VERSION
  26 };
  27
  28 #define FW_VER_COUNT 1
  29 static const int fw_versions[] = {
  30         UTIL_FW_VERSION
  31 };
  32
  33 /*
  34  * Timeout values are based on expecations from host
  35  */
  36 #define VSS_FREEZE_TIMEOUT (15 * 60)
  37
  38 /*
  39  * Global state maintained for transaction that is being processed. For a class
  40  * of integration services, including the "VSS service", the specified protocol
  41  * is a "request/response" protocol which means that there can only be single
  42  * outstanding transaction from the host at any given point in time. We use
  43  * this to simplify memory management in this driver - we cache and process
  44  * only one message at a time.
  45  *
  46  * While the request/response protocol is guaranteed by the host, we further
  47  * ensure this by serializing packet processing in this driver - we do not
  48  * read additional packets from the VMBUs until the current packet is fully
  49  * handled.
  50  */
  51
  52 static struct {
  53         int state;   /* hvutil_device_state */
  54         int recv_len; /* number of bytes received. */
  55         struct vmbus_channel *recv_channel; /* chn we got the request */
  56         u64 recv_req_id; /* request ID. */
  57         struct hv_vss_msg  *msg; /* current message */
  58 } vss_transaction;
  59
  60
  61 static void vss_respond_to_host(int error);
  62
  63 /*
  64  * This state maintains the version number registered by the daemon.
  65  */
  66 static int dm_reg_value;
  67
  68 static const char vss_devname[] = "vmbus/hv_vss";
  69 static __u8 *recv_buffer;
  70 static struct hvutil_transport *hvt;
  71
  72 static void vss_timeout_func(struct work_struct *dummy);
  73 static void vss_handle_request(struct work_struct *dummy);
  74
  75 static DECLARE_DELAYED_WORK(vss_timeout_work, vss_timeout_func);
  76 static DECLARE_WORK(vss_handle_request_work, vss_handle_request);
  77
  78 static void vss_poll_wrapper(void *channel)
  79 {
  80         /* Transaction is finished, reset the state here to avoid races. */
  81         vss_transaction.state = HVUTIL_READY;
  82         hv_vss_onchannelcallback(channel);
  83 }
  84
  85 /*
  86  * Callback when data is received from user mode.
  87  */
  88
  89 static void vss_timeout_func(struct work_struct *dummy)
  90 {
  91         /*
  92          * Timeout waiting for userspace component to reply happened.
  93          */
  94         pr_warn("VSS: timeout waiting for daemon to reply\n");
  95         vss_respond_to_host(HV_E_FAIL);
  96
  97         hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
  98 }
  99
 100 static void vss_register_done(void)
 101 {
 102         hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
 103         pr_debug("VSS: userspace daemon registered\n");
 104 }
 105
 106 static int vss_handle_handshake(struct hv_vss_msg *vss_msg)
 107 {
 108         u32 our_ver = VSS_OP_REGISTER1;
 109
 110         switch (vss_msg->vss_hdr.operation) {
 111         case VSS_OP_REGISTER:
 112                 /* Daemon doesn't expect us to reply */
 113                 dm_reg_value = VSS_OP_REGISTER;
 114                 break;
 115         case VSS_OP_REGISTER1:
 116                 /* Daemon expects us to reply with our own version */
 117                 if (hvutil_transport_send(hvt, &our_ver, sizeof(our_ver),
 118                                           vss_register_done))
 119                         return -EFAULT;
 120                 dm_reg_value = VSS_OP_REGISTER1;
 121                 break;
 122         default:
 123                 return -EINVAL;
 124         }
 125         pr_info("VSS: userspace daemon ver. %d connected\n", dm_reg_value);
 126         return 0;
 127 }
 128
 129 static int vss_on_msg(void *msg, int len)
 130 {
 131         struct hv_vss_msg *vss_msg = (struct hv_vss_msg *)msg;
 132
 133         if (len != sizeof(*vss_msg)) {
 134                 pr_debug("VSS: Message size does not match length\n");
 135                 return -EINVAL;
 136         }
 137
 138         if (vss_msg->vss_hdr.operation == VSS_OP_REGISTER ||
 139             vss_msg->vss_hdr.operation == VSS_OP_REGISTER1) {
 140                 /*
 141                  * Don't process registration messages if we're in the middle
 142                  * of a transaction processing.
 143                  */
 144                 if (vss_transaction.state > HVUTIL_READY) {
 145                         pr_debug("VSS: Got unexpected registration request\n");
 146                         return -EINVAL;
 147                 }
 148
 149                 return vss_handle_handshake(vss_msg);
 150         } else if (vss_transaction.state == HVUTIL_USERSPACE_REQ) {
 151                 vss_transaction.state = HVUTIL_USERSPACE_RECV;
 152
 153                 if (vss_msg->vss_hdr.operation == VSS_OP_HOT_BACKUP)
 154                         vss_transaction.msg->vss_cf.flags =
 155                                 VSS_HBU_NO_AUTO_RECOVERY;
 156
 157                 if (cancel_delayed_work_sync(&vss_timeout_work)) {
 158                         vss_respond_to_host(vss_msg->error);
 159                         /* Transaction is finished, reset the state. */
 160                         hv_poll_channel(vss_transaction.recv_channel,
 161                                         vss_poll_wrapper);
 162                 }
 163         } else {
 164                 /* This is a spurious call! */
 165                 pr_debug("VSS: Transaction not active\n");
 166                 return -EINVAL;
 167         }
 168         return 0;
 169 }
 170
 171 static void vss_send_op(void)
 172 {
 173         int op = vss_transaction.msg->vss_hdr.operation;
 174         int rc;
 175         struct hv_vss_msg *vss_msg;
 176
 177         /* The transaction state is wrong. */
 178         if (vss_transaction.state != HVUTIL_HOSTMSG_RECEIVED) {
 179                 pr_debug("VSS: Unexpected attempt to send to daemon\n");
 180                 return;
 181         }
 182
 183         vss_msg = kzalloc(sizeof(*vss_msg), GFP_KERNEL);
 184         if (!vss_msg)
 185                 return;
 186
 187         vss_msg->vss_hdr.operation = op;
 188
 189         vss_transaction.state = HVUTIL_USERSPACE_REQ;
 190
 191         schedule_delayed_work(&vss_timeout_work, op == VSS_OP_FREEZE ?
 192                         VSS_FREEZE_TIMEOUT * HZ : HV_UTIL_TIMEOUT * HZ);
 193
 194         rc = hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg), NULL);
 195         if (rc) {
 196                 pr_warn("VSS: failed to communicate to the daemon: %d\n", rc);
 197                 if (cancel_delayed_work_sync(&vss_timeout_work)) {
 198                         vss_respond_to_host(HV_E_FAIL);
 199                         vss_transaction.state = HVUTIL_READY;
 200                 }
 201         }
 202
 203         kfree(vss_msg);
 204 }
 205
 206 static void vss_handle_request(struct work_struct *dummy)
 207 {
 208         switch (vss_transaction.msg->vss_hdr.operation) {
 209         /*
 210          * Initiate a "freeze/thaw" operation in the guest.
 211          * We respond to the host once the operation is complete.
 212          *
 213          * We send the message to the user space daemon and the operation is
 214          * performed in the daemon.
 215          */
 216         case VSS_OP_THAW:
 217         case VSS_OP_FREEZE:
 218         case VSS_OP_HOT_BACKUP:
 219                 if (vss_transaction.state < HVUTIL_READY) {
 220                         /* Userspace is not registered yet */
 221                         pr_debug("VSS: Not ready for request.\n");
 222                         vss_respond_to_host(HV_E_FAIL);
 223                         return;
 224                 }
 225
 226                 pr_debug("VSS: Received request for op code: %d\n",
 227                         vss_transaction.msg->vss_hdr.operation);
 228                 vss_transaction.state = HVUTIL_HOSTMSG_RECEIVED;
 229                 vss_send_op();
 230                 return;
 231         case VSS_OP_GET_DM_INFO:
 232                 vss_transaction.msg->dm_info.flags = 0;
 233                 break;
 234         default:
 235                 break;
 236         }
 237
 238         vss_respond_to_host(0);
 239         hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
 240 }
 241
 242 /*
 243  * Send a response back to the host.
 244  */
 245
 246 static void
 247 vss_respond_to_host(int error)
 248 {
 249         struct icmsg_hdr *icmsghdrp;
 250         u32     buf_len;
 251         struct vmbus_channel *channel;
 252         u64     req_id;
 253
 254         /*
 255          * Copy the global state for completing the transaction. Note that
 256          * only one transaction can be active at a time.
 257          */
 258
 259         buf_len = vss_transaction.recv_len;
 260         channel = vss_transaction.recv_channel;
 261         req_id = vss_transaction.recv_req_id;
 262
 263         icmsghdrp = (struct icmsg_hdr *)
 264                         &recv_buffer[sizeof(struct vmbuspipe_hdr)];
 265
 266         if (channel->onchannel_callback == NULL)
 267                 /*
 268                  * We have raced with util driver being unloaded;
 269                  * silently return.
 270                  */
 271                 return;
 272
 273         icmsghdrp->status = error;
 274
 275         icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
 276
 277         vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
 278                                 VM_PKT_DATA_INBAND, 0);
 279
 280 }
 281
 282 /*
 283  * This callback is invoked when we get a VSS message from the host.
 284  * The host ensures that only one VSS transaction can be active at a time.
 285  */
 286
 287 void hv_vss_onchannelcallback(void *context)
 288 {
 289         struct vmbus_channel *channel = context;
 290         u32 recvlen;
 291         u64 requestid;
 292         struct hv_vss_msg *vss_msg;
 293         int vss_srv_version;
 294
 295         struct icmsg_hdr *icmsghdrp;
 296
 297         if (vss_transaction.state > HVUTIL_READY)
 298                 return;
 299
 300         vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 2, &recvlen,
 301                          &requestid);
 302
 303         if (recvlen > 0) {
 304                 icmsghdrp = (struct icmsg_hdr *)&recv_buffer[
 305                         sizeof(struct vmbuspipe_hdr)];
 306
 307                 if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
 308                         if (vmbus_prep_negotiate_resp(icmsghdrp,
 309                                  recv_buffer, fw_versions, FW_VER_COUNT,
 310                                  vss_versions, VSS_VER_COUNT,
 311                                  NULL, &vss_srv_version)) {
 312
 313                                 pr_info("VSS IC version %d.%d\n",
 314                                         vss_srv_version >> 16,
 315                                         vss_srv_version & 0xFFFF);
 316                         }
 317                 } else {
 318                         vss_msg = (struct hv_vss_msg *)&recv_buffer[
 319                                 sizeof(struct vmbuspipe_hdr) +
 320                                 sizeof(struct icmsg_hdr)];
 321
 322                         /*
 323                          * Stash away this global state for completing the
 324                          * transaction; note transactions are serialized.
 325                          */
 326
 327                         vss_transaction.recv_len = recvlen;
 328                         vss_transaction.recv_req_id = requestid;
 329                         vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
 330
 331                         schedule_work(&vss_handle_request_work);
 332                         return;
 333                 }
 334
 335                 icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
 336                         | ICMSGHDRFLAG_RESPONSE;
 337
 338                 vmbus_sendpacket(channel, recv_buffer,
 339                                        recvlen, requestid,
 340                                        VM_PKT_DATA_INBAND, 0);
 341         }
 342
 343 }
 344
 345 static void vss_on_reset(void)
 346 {
 347         if (cancel_delayed_work_sync(&vss_timeout_work))
 348                 vss_respond_to_host(HV_E_FAIL);
 349         vss_transaction.state = HVUTIL_DEVICE_INIT;
 350 }
 351
 352 int
 353 hv_vss_init(struct hv_util_service *srv)
 354 {
 355         if (vmbus_proto_version < VERSION_WIN8_1) {
 356                 pr_warn("Integration service 'Backup (volume snapshot)'"
 357                         " not supported on this host version.\n");
 358                 return -ENOTSUPP;
 359         }
 360         recv_buffer = srv->recv_buffer;
 361         vss_transaction.recv_channel = srv->channel;
 362
 363         /*
 364          * When this driver loads, the user level daemon that
 365          * processes the host requests may not yet be running.
 366          * Defer processing channel callbacks until the daemon
 367          * has registered.
 368          */
 369         vss_transaction.state = HVUTIL_DEVICE_INIT;
 370
 371         hvt = hvutil_transport_init(vss_devname, CN_VSS_IDX, CN_VSS_VAL,
 372                                     vss_on_msg, vss_on_reset);
 373         if (!hvt) {
 374                 pr_warn("VSS: Failed to initialize transport\n");
 375                 return -EFAULT;
 376         }
 377
 378         return 0;
 379 }
 380
 381 void hv_vss_deinit(void)
 382 {
 383         vss_transaction.state = HVUTIL_DEVICE_DYING;
 384         cancel_delayed_work_sync(&vss_timeout_work);
 385         cancel_work_sync(&vss_handle_request_work);
 386         hvutil_transport_destroy(hvt);
 387 }