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