xref: /linux/drivers/hv/hv_snapshot.c (revision 01b944fe1cd4e21a2a9ed51adbdbafe2d5e905ba)
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 #include "hyperv_vmbus.h"
28 #include "hv_utils_transport.h"
29 
30 #define VSS_MAJOR  5
31 #define VSS_MINOR  0
32 #define VSS_VERSION    (VSS_MAJOR << 16 | VSS_MINOR)
33 
34 #define VSS_USERSPACE_TIMEOUT (msecs_to_jiffies(10 * 1000))
35 
36 /*
37  * Global state maintained for transaction that is being processed. For a class
38  * of integration services, including the "VSS service", the specified protocol
39  * is a "request/response" protocol which means that there can only be single
40  * outstanding transaction from the host at any given point in time. We use
41  * this to simplify memory management in this driver - we cache and process
42  * only one message at a time.
43  *
44  * While the request/response protocol is guaranteed by the host, we further
45  * ensure this by serializing packet processing in this driver - we do not
46  * read additional packets from the VMBUs until the current packet is fully
47  * handled.
48  */
49 
50 static struct {
51 	int state;   /* hvutil_device_state */
52 	int recv_len; /* number of bytes received. */
53 	struct vmbus_channel *recv_channel; /* chn we got the request */
54 	u64 recv_req_id; /* request ID. */
55 	struct hv_vss_msg  *msg; /* current message */
56 	void *vss_context; /* for the channel callback */
57 } vss_transaction;
58 
59 
60 static void vss_respond_to_host(int error);
61 
62 /*
63  * This state maintains the version number registered by the daemon.
64  */
65 static int dm_reg_value;
66 
67 static const char vss_devname[] = "vmbus/hv_vss";
68 static __u8 *recv_buffer;
69 static struct hvutil_transport *hvt;
70 
71 static void vss_send_op(struct work_struct *dummy);
72 static void vss_timeout_func(struct work_struct *dummy);
73 
74 static DECLARE_DELAYED_WORK(vss_timeout_work, vss_timeout_func);
75 static DECLARE_WORK(vss_send_op_work, vss_send_op);
76 
77 /*
78  * Callback when data is received from user mode.
79  */
80 
81 static void vss_timeout_func(struct work_struct *dummy)
82 {
83 	/*
84 	 * Timeout waiting for userspace component to reply happened.
85 	 */
86 	pr_warn("VSS: timeout waiting for daemon to reply\n");
87 	vss_respond_to_host(HV_E_FAIL);
88 
89 	/* Transaction is finished, reset the state. */
90 	if (vss_transaction.state > HVUTIL_READY)
91 		vss_transaction.state = HVUTIL_READY;
92 
93 	hv_poll_channel(vss_transaction.vss_context,
94 			hv_vss_onchannelcallback);
95 }
96 
97 static int vss_handle_handshake(struct hv_vss_msg *vss_msg)
98 {
99 	u32 our_ver = VSS_OP_REGISTER1;
100 
101 	switch (vss_msg->vss_hdr.operation) {
102 	case VSS_OP_REGISTER:
103 		/* Daemon doesn't expect us to reply */
104 		dm_reg_value = VSS_OP_REGISTER;
105 		break;
106 	case VSS_OP_REGISTER1:
107 		/* Daemon expects us to reply with our own version*/
108 		if (hvutil_transport_send(hvt, &our_ver, sizeof(our_ver)))
109 			return -EFAULT;
110 		dm_reg_value = VSS_OP_REGISTER1;
111 		break;
112 	default:
113 		return -EINVAL;
114 	}
115 	vss_transaction.state = HVUTIL_READY;
116 	pr_debug("VSS: userspace daemon ver. %d registered\n", dm_reg_value);
117 	return 0;
118 }
119 
120 static int vss_on_msg(void *msg, int len)
121 {
122 	struct hv_vss_msg *vss_msg = (struct hv_vss_msg *)msg;
123 
124 	if (len != sizeof(*vss_msg))
125 		return -EINVAL;
126 
127 	if (vss_msg->vss_hdr.operation == VSS_OP_REGISTER ||
128 	    vss_msg->vss_hdr.operation == VSS_OP_REGISTER1) {
129 		/*
130 		 * Don't process registration messages if we're in the middle
131 		 * of a transaction processing.
132 		 */
133 		if (vss_transaction.state > HVUTIL_READY)
134 			return -EINVAL;
135 		return vss_handle_handshake(vss_msg);
136 	} else if (vss_transaction.state == HVUTIL_USERSPACE_REQ) {
137 		vss_transaction.state = HVUTIL_USERSPACE_RECV;
138 		if (cancel_delayed_work_sync(&vss_timeout_work)) {
139 			vss_respond_to_host(vss_msg->error);
140 			/* Transaction is finished, reset the state. */
141 			vss_transaction.state = HVUTIL_READY;
142 			hv_poll_channel(vss_transaction.vss_context,
143 					hv_vss_onchannelcallback);
144 		}
145 	} else {
146 		/* This is a spurious call! */
147 		pr_warn("VSS: Transaction not active\n");
148 		return -EINVAL;
149 	}
150 	return 0;
151 }
152 
153 
154 static void vss_send_op(struct work_struct *dummy)
155 {
156 	int op = vss_transaction.msg->vss_hdr.operation;
157 	int rc;
158 	struct hv_vss_msg *vss_msg;
159 
160 	/* The transaction state is wrong. */
161 	if (vss_transaction.state != HVUTIL_HOSTMSG_RECEIVED)
162 		return;
163 
164 	vss_msg = kzalloc(sizeof(*vss_msg), GFP_KERNEL);
165 	if (!vss_msg)
166 		return;
167 
168 	vss_msg->vss_hdr.operation = op;
169 
170 	vss_transaction.state = HVUTIL_USERSPACE_REQ;
171 	rc = hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg));
172 	if (rc) {
173 		pr_warn("VSS: failed to communicate to the daemon: %d\n", rc);
174 		if (cancel_delayed_work_sync(&vss_timeout_work)) {
175 			vss_respond_to_host(HV_E_FAIL);
176 			vss_transaction.state = HVUTIL_READY;
177 		}
178 	}
179 
180 	kfree(vss_msg);
181 
182 	return;
183 }
184 
185 /*
186  * Send a response back to the host.
187  */
188 
189 static void
190 vss_respond_to_host(int error)
191 {
192 	struct icmsg_hdr *icmsghdrp;
193 	u32	buf_len;
194 	struct vmbus_channel *channel;
195 	u64	req_id;
196 
197 	/*
198 	 * Copy the global state for completing the transaction. Note that
199 	 * only one transaction can be active at a time.
200 	 */
201 
202 	buf_len = vss_transaction.recv_len;
203 	channel = vss_transaction.recv_channel;
204 	req_id = vss_transaction.recv_req_id;
205 
206 	icmsghdrp = (struct icmsg_hdr *)
207 			&recv_buffer[sizeof(struct vmbuspipe_hdr)];
208 
209 	if (channel->onchannel_callback == NULL)
210 		/*
211 		 * We have raced with util driver being unloaded;
212 		 * silently return.
213 		 */
214 		return;
215 
216 	icmsghdrp->status = error;
217 
218 	icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
219 
220 	vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
221 				VM_PKT_DATA_INBAND, 0);
222 
223 }
224 
225 /*
226  * This callback is invoked when we get a VSS message from the host.
227  * The host ensures that only one VSS transaction can be active at a time.
228  */
229 
230 void hv_vss_onchannelcallback(void *context)
231 {
232 	struct vmbus_channel *channel = context;
233 	u32 recvlen;
234 	u64 requestid;
235 	struct hv_vss_msg *vss_msg;
236 
237 
238 	struct icmsg_hdr *icmsghdrp;
239 	struct icmsg_negotiate *negop = NULL;
240 
241 	if (vss_transaction.state > HVUTIL_READY) {
242 		/*
243 		 * We will defer processing this callback once
244 		 * the current transaction is complete.
245 		 */
246 		vss_transaction.vss_context = context;
247 		return;
248 	}
249 	vss_transaction.vss_context = NULL;
250 
251 	vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 2, &recvlen,
252 			 &requestid);
253 
254 	if (recvlen > 0) {
255 		icmsghdrp = (struct icmsg_hdr *)&recv_buffer[
256 			sizeof(struct vmbuspipe_hdr)];
257 
258 		if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
259 			vmbus_prep_negotiate_resp(icmsghdrp, negop,
260 				 recv_buffer, UTIL_FW_VERSION,
261 				 VSS_VERSION);
262 		} else {
263 			vss_msg = (struct hv_vss_msg *)&recv_buffer[
264 				sizeof(struct vmbuspipe_hdr) +
265 				sizeof(struct icmsg_hdr)];
266 
267 			/*
268 			 * Stash away this global state for completing the
269 			 * transaction; note transactions are serialized.
270 			 */
271 
272 			vss_transaction.recv_len = recvlen;
273 			vss_transaction.recv_channel = channel;
274 			vss_transaction.recv_req_id = requestid;
275 			vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
276 
277 			switch (vss_msg->vss_hdr.operation) {
278 				/*
279 				 * Initiate a "freeze/thaw"
280 				 * operation in the guest.
281 				 * We respond to the host once
282 				 * the operation is complete.
283 				 *
284 				 * We send the message to the
285 				 * user space daemon and the
286 				 * operation is performed in
287 				 * the daemon.
288 				 */
289 			case VSS_OP_FREEZE:
290 			case VSS_OP_THAW:
291 				if (vss_transaction.state < HVUTIL_READY) {
292 					/* Userspace is not registered yet */
293 					vss_respond_to_host(HV_E_FAIL);
294 					return;
295 				}
296 				vss_transaction.state = HVUTIL_HOSTMSG_RECEIVED;
297 				schedule_work(&vss_send_op_work);
298 				schedule_delayed_work(&vss_timeout_work,
299 						      VSS_USERSPACE_TIMEOUT);
300 				return;
301 
302 			case VSS_OP_HOT_BACKUP:
303 				vss_msg->vss_cf.flags =
304 					 VSS_HBU_NO_AUTO_RECOVERY;
305 				vss_respond_to_host(0);
306 				return;
307 
308 			case VSS_OP_GET_DM_INFO:
309 				vss_msg->dm_info.flags = 0;
310 				vss_respond_to_host(0);
311 				return;
312 
313 			default:
314 				vss_respond_to_host(0);
315 				return;
316 
317 			}
318 
319 		}
320 
321 		icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
322 			| ICMSGHDRFLAG_RESPONSE;
323 
324 		vmbus_sendpacket(channel, recv_buffer,
325 				       recvlen, requestid,
326 				       VM_PKT_DATA_INBAND, 0);
327 	}
328 
329 }
330 
331 static void vss_on_reset(void)
332 {
333 	if (cancel_delayed_work_sync(&vss_timeout_work))
334 		vss_respond_to_host(HV_E_FAIL);
335 	vss_transaction.state = HVUTIL_DEVICE_INIT;
336 }
337 
338 int
339 hv_vss_init(struct hv_util_service *srv)
340 {
341 	recv_buffer = srv->recv_buffer;
342 
343 	/*
344 	 * When this driver loads, the user level daemon that
345 	 * processes the host requests may not yet be running.
346 	 * Defer processing channel callbacks until the daemon
347 	 * has registered.
348 	 */
349 	vss_transaction.state = HVUTIL_DEVICE_INIT;
350 
351 	hvt = hvutil_transport_init(vss_devname, CN_VSS_IDX, CN_VSS_VAL,
352 				    vss_on_msg, vss_on_reset);
353 	if (!hvt)
354 		return -EFAULT;
355 
356 	return 0;
357 }
358 
359 void hv_vss_deinit(void)
360 {
361 	vss_transaction.state = HVUTIL_DEVICE_DYING;
362 	cancel_delayed_work_sync(&vss_timeout_work);
363 	cancel_work_sync(&vss_send_op_work);
364 	hvutil_transport_destroy(hvt);
365 }
366