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
  28
  29 /*
  30  * Global state maintained for transaction that is being processed.
  31  * Note that only one transaction can be active at any point in time.
  32  *
  33  * This state is set when we receive a request from the host; we
  34  * cleanup this state when the transaction is completed - when we respond
  35  * to the host with the key value.
  36  */
  37
  38 static struct {
  39         bool active; /* transaction status - active or not */
  40         int recv_len; /* number of bytes received. */
  41         struct vmbus_channel *recv_channel; /* chn we got the request */
  42         u64 recv_req_id; /* request ID. */
  43         struct hv_vss_msg  *msg; /* current message */
  44 } vss_transaction;
  45
  46
  47 static void vss_respond_to_host(int error);
  48
  49 static struct cb_id vss_id = { CN_VSS_IDX, CN_VSS_VAL };
  50 static const char vss_name[] = "vss_kernel_module";
  51 static __u8 *recv_buffer;
  52
  53 static void vss_send_op(struct work_struct *dummy);
  54 static DECLARE_WORK(vss_send_op_work, vss_send_op);
  55
  56 /*
  57  * Callback when data is received from user mode.
  58  */
  59
  60 static void
  61 vss_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
  62 {
  63         struct hv_vss_msg *vss_msg;
  64
  65         vss_msg = (struct hv_vss_msg *)msg->data;
  66
  67         if (vss_msg->vss_hdr.operation == VSS_OP_REGISTER) {
  68                 pr_info("VSS daemon registered\n");
  69                 vss_transaction.active = false;
  70                 if (vss_transaction.recv_channel != NULL)
  71                         hv_vss_onchannelcallback(vss_transaction.recv_channel);
  72                 return;
  73
  74         }
  75         vss_respond_to_host(vss_msg->error);
  76 }
  77
  78
  79 static void vss_send_op(struct work_struct *dummy)
  80 {
  81         int op = vss_transaction.msg->vss_hdr.operation;
  82         struct cn_msg *msg;
  83         struct hv_vss_msg *vss_msg;
  84
  85         msg = kzalloc(sizeof(*msg) + sizeof(*vss_msg), GFP_ATOMIC);
  86         if (!msg)
  87                 return;
  88
  89         vss_msg = (struct hv_vss_msg *)msg->data;
  90
  91         msg->id.idx =  CN_VSS_IDX;
  92         msg->id.val = CN_VSS_VAL;
  93
  94         vss_msg->vss_hdr.operation = op;
  95         msg->len = sizeof(struct hv_vss_msg);
  96
  97         cn_netlink_send(msg, 0, GFP_ATOMIC);
  98         kfree(msg);
  99
 100         return;
 101 }
 102
 103 /*
 104  * Send a response back to the host.
 105  */
 106
 107 static void
 108 vss_respond_to_host(int error)
 109 {
 110         struct icmsg_hdr *icmsghdrp;
 111         u32     buf_len;
 112         struct vmbus_channel *channel;
 113         u64     req_id;
 114
 115         /*
 116          * If a transaction is not active; log and return.
 117          */
 118
 119         if (!vss_transaction.active) {
 120                 /*
 121                  * This is a spurious call!
 122                  */
 123                 pr_warn("VSS: Transaction not active\n");
 124                 return;
 125         }
 126         /*
 127          * Copy the global state for completing the transaction. Note that
 128          * only one transaction can be active at a time.
 129          */
 130
 131         buf_len = vss_transaction.recv_len;
 132         channel = vss_transaction.recv_channel;
 133         req_id = vss_transaction.recv_req_id;
 134         vss_transaction.active = false;
 135
 136         icmsghdrp = (struct icmsg_hdr *)
 137                         &recv_buffer[sizeof(struct vmbuspipe_hdr)];
 138
 139         if (channel->onchannel_callback == NULL)
 140                 /*
 141                  * We have raced with util driver being unloaded;
 142                  * silently return.
 143                  */
 144                 return;
 145
 146         icmsghdrp->status = error;
 147
 148         icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
 149
 150         vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
 151                                 VM_PKT_DATA_INBAND, 0);
 152
 153 }
 154
 155 /*
 156  * This callback is invoked when we get a VSS message from the host.
 157  * The host ensures that only one VSS transaction can be active at a time.
 158  */
 159
 160 void hv_vss_onchannelcallback(void *context)
 161 {
 162         struct vmbus_channel *channel = context;
 163         u32 recvlen;
 164         u64 requestid;
 165         struct hv_vss_msg *vss_msg;
 166
 167
 168         struct icmsg_hdr *icmsghdrp;
 169         struct icmsg_negotiate *negop = NULL;
 170
 171         if (vss_transaction.active) {
 172                 /*
 173                  * We will defer processing this callback once
 174                  * the current transaction is complete.
 175                  */
 176                 vss_transaction.recv_channel = channel;
 177                 return;
 178         }
 179
 180         vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 2, &recvlen,
 181                          &requestid);
 182
 183         if (recvlen > 0) {
 184                 icmsghdrp = (struct icmsg_hdr *)&recv_buffer[
 185                         sizeof(struct vmbuspipe_hdr)];
 186
 187                 if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
 188                         vmbus_prep_negotiate_resp(icmsghdrp, negop,
 189                                  recv_buffer, MAX_SRV_VER, MAX_SRV_VER);
 190                         /*
 191                          * We currently negotiate the highest number the
 192                          * host has presented. If this version is not
 193                          * atleast 5.0, reject.
 194                          */
 195                         negop = (struct icmsg_negotiate *)&recv_buffer[
 196                                 sizeof(struct vmbuspipe_hdr) +
 197                                 sizeof(struct icmsg_hdr)];
 198
 199                         if (negop->icversion_data[1].major < 5)
 200                                 negop->icframe_vercnt = 0;
 201                 } else {
 202                         vss_msg = (struct hv_vss_msg *)&recv_buffer[
 203                                 sizeof(struct vmbuspipe_hdr) +
 204                                 sizeof(struct icmsg_hdr)];
 205
 206                         /*
 207                          * Stash away this global state for completing the
 208                          * transaction; note transactions are serialized.
 209                          */
 210
 211                         vss_transaction.recv_len = recvlen;
 212                         vss_transaction.recv_channel = channel;
 213                         vss_transaction.recv_req_id = requestid;
 214                         vss_transaction.active = true;
 215                         vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
 216
 217                         switch (vss_msg->vss_hdr.operation) {
 218                                 /*
 219                                  * Initiate a "freeze/thaw"
 220                                  * operation in the guest.
 221                                  * We respond to the host once
 222                                  * the operation is complete.
 223                                  *
 224                                  * We send the message to the
 225                                  * user space daemon and the
 226                                  * operation is performed in
 227                                  * the daemon.
 228                                  */
 229                         case VSS_OP_FREEZE:
 230                         case VSS_OP_THAW:
 231                                 schedule_work(&vss_send_op_work);
 232                                 return;
 233
 234                         case VSS_OP_HOT_BACKUP:
 235                                 vss_msg->vss_cf.flags =
 236                                          VSS_HBU_NO_AUTO_RECOVERY;
 237                                 vss_respond_to_host(0);
 238                                 return;
 239
 240                         case VSS_OP_GET_DM_INFO:
 241                                 vss_msg->dm_info.flags = 0;
 242                                 vss_respond_to_host(0);
 243                                 return;
 244
 245                         default:
 246                                 vss_respond_to_host(0);
 247                                 return;
 248
 249                         }
 250
 251                 }
 252
 253                 icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
 254                         | ICMSGHDRFLAG_RESPONSE;
 255
 256                 vmbus_sendpacket(channel, recv_buffer,
 257                                        recvlen, requestid,
 258                                        VM_PKT_DATA_INBAND, 0);
 259         }
 260
 261 }
 262
 263 int
 264 hv_vss_init(struct hv_util_service *srv)
 265 {
 266         int err;
 267
 268         err = cn_add_callback(&vss_id, vss_name, vss_cn_callback);
 269         if (err)
 270                 return err;
 271         recv_buffer = srv->recv_buffer;
 272
 273         /*
 274          * When this driver loads, the user level daemon that
 275          * processes the host requests may not yet be running.
 276          * Defer processing channel callbacks until the daemon
 277          * has registered.
 278          */
 279         vss_transaction.active = true;
 280         return 0;
 281 }
 282
 283 void hv_vss_deinit(void)
 284 {
 285         cn_del_callback(&vss_id);
 286         cancel_work_sync(&vss_send_op_work);
 287 }