summaryrefslogtreecommitdiffstats
path: root/drivers/xen/xenbus/xenbus_comms.c
blob: 2eff7a6aaa20a8e920ed4f0e7b024a941e791580 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
/******************************************************************************
 * xenbus_comms.c
 *
 * Low level code to talks to Xen Store: ringbuffer and event channel.
 *
 * Copyright (C) 2005 Rusty Russell, IBM Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <linux/wait.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/err.h>
#include <xen/xenbus.h>
#include <asm/xen/hypervisor.h>
#include <xen/events.h>
#include <xen/page.h>
#include "xenbus_comms.h"

static int xenbus_irq;

static DECLARE_WORK(probe_work, xenbus_probe);

static DECLARE_WAIT_QUEUE_HEAD(xb_waitq);

static irqreturn_t wake_waiting(int irq, void *unused)
{
	if (unlikely(xenstored_ready == 0)) {
		xenstored_ready = 1;
		schedule_work(&probe_work);
	}

	wake_up(&xb_waitq);
	return IRQ_HANDLED;
}

static int check_indexes(XENSTORE_RING_IDX cons, XENSTORE_RING_IDX prod)
{
	return ((prod - cons) <= XENSTORE_RING_SIZE);
}

static void *get_output_chunk(XENSTORE_RING_IDX cons,
			      XENSTORE_RING_IDX prod,
			      char *buf, uint32_t *len)
{
	*len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod);
	if ((XENSTORE_RING_SIZE - (prod - cons)) < *len)
		*len = XENSTORE_RING_SIZE - (prod - cons);
	return buf + MASK_XENSTORE_IDX(prod);
}

static const void *get_input_chunk(XENSTORE_RING_IDX cons,
				   XENSTORE_RING_IDX prod,
				   const char *buf, uint32_t *len)
{
	*len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(cons);
	if ((prod - cons) < *len)
		*len = prod - cons;
	return buf + MASK_XENSTORE_IDX(cons);
}

/**
 * xb_write - low level write
 * @data: buffer to send
 * @len: length of buffer
 *
 * Returns 0 on success, error otherwise.
 */
int xb_write(const void *data, unsigned len)
{
	struct xenstore_domain_interface *intf = xen_store_interface;
	XENSTORE_RING_IDX cons, prod;
	int rc;

	while (len != 0) {
		void *dst;
		unsigned int avail;

		rc = wait_event_interruptible(
			xb_waitq,
			(intf->req_prod - intf->req_cons) !=
			XENSTORE_RING_SIZE);
		if (rc < 0)
			return rc;

		/* Read indexes, then verify. */
		cons = intf->req_cons;
		prod = intf->req_prod;
		if (!check_indexes(cons, prod)) {
			intf->req_cons = intf->req_prod = 0;
			return -EIO;
		}

		dst = get_output_chunk(cons, prod, intf->req, &avail);
		if (avail == 0)
			continue;
		if (avail > len)
			avail = len;

		/* Must write data /after/ reading the consumer index. */
		mb();

		memcpy(dst, data, avail);
		data += avail;
		len -= avail;

		/* Other side must not see new producer until data is there. */
		wmb();
		intf->req_prod += avail;

		/* Implies mb(): other side will see the updated producer. */
		notify_remote_via_evtchn(xen_store_evtchn);
	}

	return 0;
}

int xb_data_to_read(void)
{
	struct xenstore_domain_interface *intf = xen_store_interface;
	return (intf->rsp_cons != intf->rsp_prod);
}

int xb_wait_for_data_to_read(void)
{
	return wait_event_interruptible(xb_waitq, xb_data_to_read());
}

int xb_read(void *data, unsigned len)
{
	struct xenstore_domain_interface *intf = xen_store_interface;
	XENSTORE_RING_IDX cons, prod;
	int rc;

	while (len != 0) {
		unsigned int avail;
		const char *src;

		rc = xb_wait_for_data_to_read();
		if (rc < 0)
			return rc;

		/* Read indexes, then verify. */
		cons = intf->rsp_cons;
		prod = intf->rsp_prod;
		if (!check_indexes(cons, prod)) {
			intf->rsp_cons = intf->rsp_prod = 0;
			return -EIO;
		}

		src = get_input_chunk(cons, prod, intf->rsp, &avail);
		if (avail == 0)
			continue;
		if (avail > len)
			avail = len;

		/* Must read data /after/ reading the producer index. */
		rmb();

		memcpy(data, src, avail);
		data += avail;
		len -= avail;

		/* Other side must not see free space until we've copied out */
		mb();
		intf->rsp_cons += avail;

		pr_debug("Finished read of %i bytes (%i to go)\n", avail, len);

		/* Implies mb(): other side will see the updated consumer. */
		notify_remote_via_evtchn(xen_store_evtchn);
	}

	return 0;
}

/**
 * xb_init_comms - Set up interrupt handler off store event channel.
 */
int xb_init_comms(void)
{
	struct xenstore_domain_interface *intf = xen_store_interface;

	if (intf->req_prod != intf->req_cons)
		printk(KERN_ERR "XENBUS request ring is not quiescent "
		       "(%08x:%08x)!\n", intf->req_cons, intf->req_prod);

	if (intf->rsp_prod != intf->rsp_cons) {
		printk(KERN_WARNING "XENBUS response ring is not quiescent "
		       "(%08x:%08x): fixing up\n",
		       intf->rsp_cons, intf->rsp_prod);
		/* breaks kdump */
		if (!reset_devices)
			intf->rsp_cons = intf->rsp_prod;
	}

	if (xenbus_irq) {
		/* Already have an irq; assume we're resuming */
		rebind_evtchn_irq(xen_store_evtchn, xenbus_irq);
	} else {
		int err;
		err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting,
						0, "xenbus", &xb_waitq);
		if (err <= 0) {
			printk(KERN_ERR "XENBUS request irq failed %i\n", err);
			return err;
		}

		xenbus_irq = err;
	}

	return 0;
}
OpenPOWER on IntegriCloud