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         int rc;
 100         struct cn_msg *msg;
 101         struct hv_vss_msg *vss_msg;
 102
 103         msg = kzalloc(sizeof(*msg) + sizeof(*vss_msg), GFP_ATOMIC);
 104         if (!msg)
 105                 return;
 106
 107         vss_msg = (struct hv_vss_msg *)msg->data;
 108
 109         msg->id.idx =  CN_VSS_IDX;
 110         msg->id.val = CN_VSS_VAL;
 111
 112         vss_msg->vss_hdr.operation = op;
 113         msg->len = sizeof(struct hv_vss_msg);
 114
 115         rc = cn_netlink_send(msg, 0, 0, GFP_ATOMIC);
 116         if (rc) {
 117                 pr_warn("VSS: failed to communicate to the daemon: %d\n", rc);
 118                 if (cancel_delayed_work_sync(&vss_timeout_work))
 119                         vss_respond_to_host(HV_E_FAIL);
 120         }
 121         kfree(msg);
 122
 123         return;
 124 }
 125
 126 /*
 127  * Send a response back to the host.
 128  */
 129
 130 static void
 131 vss_respond_to_host(int error)
 132 {
 133         struct icmsg_hdr *icmsghdrp;
 134         u32     buf_len;
 135         struct vmbus_channel *channel;
 136         u64     req_id;
 137
 138         /*
 139          * If a transaction is not active; log and return.
 140          */
 141
 142         if (!vss_transaction.active) {
 143                 /*
 144                  * This is a spurious call!
 145                  */
 146                 pr_warn("VSS: Transaction not active\n");
 147                 return;
 148         }
 149         /*
 150          * Copy the global state for completing the transaction. Note that
 151          * only one transaction can be active at a time.
 152          */
 153
 154         buf_len = vss_transaction.recv_len;
 155         channel = vss_transaction.recv_channel;
 156         req_id = vss_transaction.recv_req_id;
 157         vss_transaction.active = false;
 158
 159         icmsghdrp = (struct icmsg_hdr *)
 160                         &recv_buffer[sizeof(struct vmbuspipe_hdr)];
 161
 162         if (channel->onchannel_callback == NULL)
 163                 /*
 164                  * We have raced with util driver being unloaded;
 165                  * silently return.
 166                  */
 167                 return;
 168
 169         icmsghdrp->status = error;
 170
 171         icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
 172
 173         vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
 174                                 VM_PKT_DATA_INBAND, 0);
 175
 176 }
 177
 178 /*
 179  * This callback is invoked when we get a VSS message from the host.
 180  * The host ensures that only one VSS transaction can be active at a time.
 181  */
 182
 183 void hv_vss_onchannelcallback(void *context)
 184 {
 185         struct vmbus_channel *channel = context;
 186         u32 recvlen;
 187         u64 requestid;
 188         struct hv_vss_msg *vss_msg;
 189
 190
 191         struct icmsg_hdr *icmsghdrp;
 192         struct icmsg_negotiate *negop = NULL;
 193
 194         if (vss_transaction.active) {
 195                 /*
 196                  * We will defer processing this callback once
 197                  * the current transaction is complete.
 198                  */
 199                 vss_transaction.recv_channel = channel;
 200                 return;
 201         }
 202
 203         vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 2, &recvlen,
 204                          &requestid);
 205
 206         if (recvlen > 0) {
 207                 icmsghdrp = (struct icmsg_hdr *)&recv_buffer[
 208                         sizeof(struct vmbuspipe_hdr)];
 209
 210                 if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
 211                         vmbus_prep_negotiate_resp(icmsghdrp, negop,
 212                                  recv_buffer, UTIL_FW_VERSION,
 213                                  VSS_VERSION);
 214                 } else {
 215                         vss_msg = (struct hv_vss_msg *)&recv_buffer[
 216                                 sizeof(struct vmbuspipe_hdr) +
 217                                 sizeof(struct icmsg_hdr)];
 218
 219                         /*
 220                          * Stash away this global state for completing the
 221                          * transaction; note transactions are serialized.
 222                          */
 223
 224                         vss_transaction.recv_len = recvlen;
 225                         vss_transaction.recv_channel = channel;
 226                         vss_transaction.recv_req_id = requestid;
 227                         vss_transaction.active = true;
 228                         vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
 229
 230                         switch (vss_msg->vss_hdr.operation) {
 231                                 /*
 232                                  * Initiate a "freeze/thaw"
 233                                  * operation in the guest.
 234                                  * We respond to the host once
 235                                  * the operation is complete.
 236                                  *
 237                                  * We send the message to the
 238                                  * user space daemon and the
 239                                  * operation is performed in
 240                                  * the daemon.
 241                                  */
 242                         case VSS_OP_FREEZE:
 243                         case VSS_OP_THAW:
 244                                 schedule_work(&vss_send_op_work);
 245                                 schedule_delayed_work(&vss_timeout_work,
 246                                                       VSS_USERSPACE_TIMEOUT);
 247                                 return;
 248
 249                         case VSS_OP_HOT_BACKUP:
 250                                 vss_msg->vss_cf.flags =
 251                                          VSS_HBU_NO_AUTO_RECOVERY;
 252                                 vss_respond_to_host(0);
 253                                 return;
 254
 255                         case VSS_OP_GET_DM_INFO:
 256                                 vss_msg->dm_info.flags = 0;
 257                                 vss_respond_to_host(0);
 258                                 return;
 259
 260                         default:
 261                                 vss_respond_to_host(0);
 262                                 return;
 263
 264                         }
 265
 266                 }
 267
 268                 icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
 269                         | ICMSGHDRFLAG_RESPONSE;
 270
 271                 vmbus_sendpacket(channel, recv_buffer,
 272                                        recvlen, requestid,
 273                                        VM_PKT_DATA_INBAND, 0);
 274         }
 275
 276 }
 277
 278 int
 279 hv_vss_init(struct hv_util_service *srv)
 280 {
 281         int err;
 282
 283         err = cn_add_callback(&vss_id, vss_name, vss_cn_callback);
 284         if (err)
 285                 return err;
 286         recv_buffer = srv->recv_buffer;
 287
 288         /*
 289          * When this driver loads, the user level daemon that
 290          * processes the host requests may not yet be running.
 291          * Defer processing channel callbacks until the daemon
 292          * has registered.
 293          */
 294         vss_transaction.active = true;
 295         return 0;
 296 }
 297
 298 void hv_vss_deinit(void)
 299 {
 300         cn_del_callback(&vss_id);
 301         cancel_delayed_work_sync(&vss_timeout_work);
 302         cancel_work_sync(&vss_send_op_work);
 303 }