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#include <asm/hyperv-tlfs.h>
16
17#include "hyperv_vmbus.h"
18#include "hv_utils_transport.h"
19
20#define VSS_MAJOR  5
21#define VSS_MINOR  0
22#define VSS_VERSION    (VSS_MAJOR << 16 | VSS_MINOR)
23
24#define VSS_VER_COUNT 1
25static const int vss_versions[] = {
26	VSS_VERSION
27};
28
29#define FW_VER_COUNT 1
30static const int fw_versions[] = {
31	UTIL_FW_VERSION
32};
33
34/*
35 * Timeout values are based on expecations from host
36 */
37#define VSS_FREEZE_TIMEOUT (15 * 60)
38
39/*
40 * Global state maintained for transaction that is being processed. For a class
41 * of integration services, including the "VSS service", the specified protocol
42 * is a "request/response" protocol which means that there can only be single
43 * outstanding transaction from the host at any given point in time. We use
44 * this to simplify memory management in this driver - we cache and process
45 * only one message at a time.
46 *
47 * While the request/response protocol is guaranteed by the host, we further
48 * ensure this by serializing packet processing in this driver - we do not
49 * read additional packets from the VMBUs until the current packet is fully
50 * handled.
51 */
52
53static struct {
54	int state;   /* hvutil_device_state */
55	int recv_len; /* number of bytes received. */
56	struct vmbus_channel *recv_channel; /* chn we got the request */
57	u64 recv_req_id; /* request ID. */
58	struct hv_vss_msg  *msg; /* current message */
59} vss_transaction;
60
61
62static void vss_respond_to_host(int error);
63
64/*
65 * This state maintains the version number registered by the daemon.
66 */
67static int dm_reg_value;
68
69static const char vss_devname[] = "vmbus/hv_vss";
70static __u8 *recv_buffer;
71static struct hvutil_transport *hvt;
72
73static void vss_timeout_func(struct work_struct *dummy);
74static void vss_handle_request(struct work_struct *dummy);
75
76static DECLARE_DELAYED_WORK(vss_timeout_work, vss_timeout_func);
77static DECLARE_WORK(vss_handle_request_work, vss_handle_request);
78
79static void vss_poll_wrapper(void *channel)
80{
81	/* Transaction is finished, reset the state here to avoid races. */
82	vss_transaction.state = HVUTIL_READY;
83	tasklet_schedule(&((struct vmbus_channel *)channel)->callback_event);
84}
85
86/*
87 * Callback when data is received from user mode.
88 */
89
90static void vss_timeout_func(struct work_struct *dummy)
91{
92	/*
93	 * Timeout waiting for userspace component to reply happened.
94	 */
95	pr_warn("VSS: timeout waiting for daemon to reply\n");
96	vss_respond_to_host(HV_E_FAIL);
97
98	hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
99}
100
101static void vss_register_done(void)
102{
103	hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
104	pr_debug("VSS: userspace daemon registered\n");
105}
106
107static int vss_handle_handshake(struct hv_vss_msg *vss_msg)
108{
109	u32 our_ver = VSS_OP_REGISTER1;
110
111	switch (vss_msg->vss_hdr.operation) {
112	case VSS_OP_REGISTER:
113		/* Daemon doesn't expect us to reply */
114		dm_reg_value = VSS_OP_REGISTER;
115		break;
116	case VSS_OP_REGISTER1:
117		/* Daemon expects us to reply with our own version */
118		if (hvutil_transport_send(hvt, &our_ver, sizeof(our_ver),
119					  vss_register_done))
120			return -EFAULT;
121		dm_reg_value = VSS_OP_REGISTER1;
122		break;
123	default:
124		return -EINVAL;
125	}
126	pr_info("VSS: userspace daemon ver. %d connected\n", dm_reg_value);
127	return 0;
128}
129
130static int vss_on_msg(void *msg, int len)
131{
132	struct hv_vss_msg *vss_msg = (struct hv_vss_msg *)msg;
133
134	if (len != sizeof(*vss_msg)) {
135		pr_debug("VSS: Message size does not match length\n");
136		return -EINVAL;
137	}
138
139	if (vss_msg->vss_hdr.operation == VSS_OP_REGISTER ||
140	    vss_msg->vss_hdr.operation == VSS_OP_REGISTER1) {
141		/*
142		 * Don't process registration messages if we're in the middle
143		 * of a transaction processing.
144		 */
145		if (vss_transaction.state > HVUTIL_READY) {
146			pr_debug("VSS: Got unexpected registration request\n");
147			return -EINVAL;
148		}
149
150		return vss_handle_handshake(vss_msg);
151	} else if (vss_transaction.state == HVUTIL_USERSPACE_REQ) {
152		vss_transaction.state = HVUTIL_USERSPACE_RECV;
153
154		if (vss_msg->vss_hdr.operation == VSS_OP_HOT_BACKUP)
155			vss_transaction.msg->vss_cf.flags =
156				VSS_HBU_NO_AUTO_RECOVERY;
157
158		if (cancel_delayed_work_sync(&vss_timeout_work)) {
159			vss_respond_to_host(vss_msg->error);
160			/* Transaction is finished, reset the state. */
161			hv_poll_channel(vss_transaction.recv_channel,
162					vss_poll_wrapper);
163		}
164	} else {
165		/* This is a spurious call! */
166		pr_debug("VSS: Transaction not active\n");
167		return -EINVAL;
168	}
169	return 0;
170}
171
172static void vss_send_op(void)
173{
174	int op = vss_transaction.msg->vss_hdr.operation;
175	int rc;
176	struct hv_vss_msg *vss_msg;
177
178	/* The transaction state is wrong. */
179	if (vss_transaction.state != HVUTIL_HOSTMSG_RECEIVED) {
180		pr_debug("VSS: Unexpected attempt to send to daemon\n");
181		return;
182	}
183
184	vss_msg = kzalloc(sizeof(*vss_msg), GFP_KERNEL);
185	if (!vss_msg)
186		return;
187
188	vss_msg->vss_hdr.operation = op;
189
190	vss_transaction.state = HVUTIL_USERSPACE_REQ;
191
192	schedule_delayed_work(&vss_timeout_work, op == VSS_OP_FREEZE ?
193			VSS_FREEZE_TIMEOUT * HZ : HV_UTIL_TIMEOUT * HZ);
194
195	rc = hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg), NULL);
196	if (rc) {
197		pr_warn("VSS: failed to communicate to the daemon: %d\n", rc);
198		if (cancel_delayed_work_sync(&vss_timeout_work)) {
199			vss_respond_to_host(HV_E_FAIL);
200			vss_transaction.state = HVUTIL_READY;
201		}
202	}
203
204	kfree(vss_msg);
205}
206
207static void vss_handle_request(struct work_struct *dummy)
208{
209	switch (vss_transaction.msg->vss_hdr.operation) {
210	/*
211	 * Initiate a "freeze/thaw" operation in the guest.
212	 * We respond to the host once the operation is complete.
213	 *
214	 * We send the message to the user space daemon and the operation is
215	 * performed in the daemon.
216	 */
217	case VSS_OP_THAW:
218	case VSS_OP_FREEZE:
219	case VSS_OP_HOT_BACKUP:
220		if (vss_transaction.state < HVUTIL_READY) {
221			/* Userspace is not registered yet */
222			pr_debug("VSS: Not ready for request.\n");
223			vss_respond_to_host(HV_E_FAIL);
224			return;
225		}
226
227		pr_debug("VSS: Received request for op code: %d\n",
228			vss_transaction.msg->vss_hdr.operation);
229		vss_transaction.state = HVUTIL_HOSTMSG_RECEIVED;
230		vss_send_op();
231		return;
232	case VSS_OP_GET_DM_INFO:
233		vss_transaction.msg->dm_info.flags = 0;
234		break;
235	default:
236		break;
237	}
238
239	vss_respond_to_host(0);
240	hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
241}
242
243/*
244 * Send a response back to the host.
245 */
246
247static void
248vss_respond_to_host(int error)
249{
250	struct icmsg_hdr *icmsghdrp;
251	u32	buf_len;
252	struct vmbus_channel *channel;
253	u64	req_id;
254
255	/*
256	 * Copy the global state for completing the transaction. Note that
257	 * only one transaction can be active at a time.
258	 */
259
260	buf_len = vss_transaction.recv_len;
261	channel = vss_transaction.recv_channel;
262	req_id = vss_transaction.recv_req_id;
263
264	icmsghdrp = (struct icmsg_hdr *)
265			&recv_buffer[sizeof(struct vmbuspipe_hdr)];
266
267	if (channel->onchannel_callback == NULL)
268		/*
269		 * We have raced with util driver being unloaded;
270		 * silently return.
271		 */
272		return;
273
274	icmsghdrp->status = error;
275
276	icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
277
278	vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
279				VM_PKT_DATA_INBAND, 0);
280
281}
282
283/*
284 * This callback is invoked when we get a VSS message from the host.
285 * The host ensures that only one VSS transaction can be active at a time.
286 */
287
288void hv_vss_onchannelcallback(void *context)
289{
290	struct vmbus_channel *channel = context;
291	u32 recvlen;
292	u64 requestid;
293	struct hv_vss_msg *vss_msg;
294	int vss_srv_version;
295
296	struct icmsg_hdr *icmsghdrp;
297
298	if (vss_transaction.state > HVUTIL_READY)
299		return;
300
301	vmbus_recvpacket(channel, recv_buffer, HV_HYP_PAGE_SIZE * 2, &recvlen,
302			 &requestid);
303
304	if (recvlen > 0) {
305		icmsghdrp = (struct icmsg_hdr *)&recv_buffer[
306			sizeof(struct vmbuspipe_hdr)];
307
308		if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
309			if (vmbus_prep_negotiate_resp(icmsghdrp,
310				 recv_buffer, fw_versions, FW_VER_COUNT,
311				 vss_versions, VSS_VER_COUNT,
312				 NULL, &vss_srv_version)) {
313
314				pr_info("VSS IC version %d.%d\n",
315					vss_srv_version >> 16,
316					vss_srv_version & 0xFFFF);
317			}
318		} else {
319			vss_msg = (struct hv_vss_msg *)&recv_buffer[
320				sizeof(struct vmbuspipe_hdr) +
321				sizeof(struct icmsg_hdr)];
322
323			/*
324			 * Stash away this global state for completing the
325			 * transaction; note transactions are serialized.
326			 */
327
328			vss_transaction.recv_len = recvlen;
329			vss_transaction.recv_req_id = requestid;
330			vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
331
332			schedule_work(&vss_handle_request_work);
333			return;
334		}
335
336		icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
337			| ICMSGHDRFLAG_RESPONSE;
338
339		vmbus_sendpacket(channel, recv_buffer,
340				       recvlen, requestid,
341				       VM_PKT_DATA_INBAND, 0);
342	}
343
344}
345
346static void vss_on_reset(void)
347{
348	if (cancel_delayed_work_sync(&vss_timeout_work))
349		vss_respond_to_host(HV_E_FAIL);
350	vss_transaction.state = HVUTIL_DEVICE_INIT;
351}
352
353int
354hv_vss_init(struct hv_util_service *srv)
355{
356	if (vmbus_proto_version < VERSION_WIN8_1) {
357		pr_warn("Integration service 'Backup (volume snapshot)'"
358			" not supported on this host version.\n");
359		return -ENOTSUPP;
360	}
361	recv_buffer = srv->recv_buffer;
362	vss_transaction.recv_channel = srv->channel;
363
364	/*
365	 * When this driver loads, the user level daemon that
366	 * processes the host requests may not yet be running.
367	 * Defer processing channel callbacks until the daemon
368	 * has registered.
369	 */
370	vss_transaction.state = HVUTIL_DEVICE_INIT;
371
372	hvt = hvutil_transport_init(vss_devname, CN_VSS_IDX, CN_VSS_VAL,
373				    vss_on_msg, vss_on_reset);
374	if (!hvt) {
375		pr_warn("VSS: Failed to initialize transport\n");
376		return -EFAULT;
377	}
378
379	return 0;
380}
381
382static void hv_vss_cancel_work(void)
383{
384	cancel_delayed_work_sync(&vss_timeout_work);
385	cancel_work_sync(&vss_handle_request_work);
386}
387
388int hv_vss_pre_suspend(void)
389{
390	struct vmbus_channel *channel = vss_transaction.recv_channel;
391	struct hv_vss_msg *vss_msg;
392
393	/*
394	 * Fake a THAW message for the user space daemon in case the daemon
395	 * has frozen the file systems. It doesn't matter if there is already
396	 * a message pending to be delivered to the user space since we force
397	 * vss_transaction.state to be HVUTIL_READY, so the user space daemon's
398	 * write() will fail with EINVAL (see vss_on_msg()), and the daemon
399	 * will reset the device by closing and re-opening it.
400	 */
401	vss_msg = kzalloc(sizeof(*vss_msg), GFP_KERNEL);
402	if (!vss_msg)
403		return -ENOMEM;
404
405	tasklet_disable(&channel->callback_event);
406
407	vss_msg->vss_hdr.operation = VSS_OP_THAW;
408
409	/* Cancel any possible pending work. */
410	hv_vss_cancel_work();
411
412	/* We don't care about the return value. */
413	hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg), NULL);
414
415	kfree(vss_msg);
416
417	vss_transaction.state = HVUTIL_READY;
418
419	/* tasklet_enable() will be called in hv_vss_pre_resume(). */
420	return 0;
421}
422
423int hv_vss_pre_resume(void)
424{
425	struct vmbus_channel *channel = vss_transaction.recv_channel;
426
427	tasklet_enable(&channel->callback_event);
428
429	return 0;
430}
431
432void hv_vss_deinit(void)
433{
434	vss_transaction.state = HVUTIL_DEVICE_DYING;
435
436	hv_vss_cancel_work();
437
438	hvutil_transport_destroy(hvt);
439}
440