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Jeremy Fitzhardinge4bac07c2007-07-17 18:37:06 -07001/******************************************************************************
2 * xenbus_comms.c
3 *
4 * Low level code to talks to Xen Store: ringbuffer and event channel.
5 *
6 * Copyright (C) 2005 Rusty Russell, IBM Corporation
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License version 2
10 * as published by the Free Software Foundation; or, when distributed
11 * separately from the Linux kernel or incorporated into other
12 * software packages, subject to the following license:
13 *
14 * Permission is hereby granted, free of charge, to any person obtaining a copy
15 * of this source file (the "Software"), to deal in the Software without
16 * restriction, including without limitation the rights to use, copy, modify,
17 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
18 * and to permit persons to whom the Software is furnished to do so, subject to
19 * the following conditions:
20 *
21 * The above copyright notice and this permission notice shall be included in
22 * all copies or substantial portions of the Software.
23 *
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
26 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
27 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
28 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
29 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
30 * IN THE SOFTWARE.
31 */
32
Joe Perches283c0972013-06-28 03:21:41 -070033#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
34
Jeremy Fitzhardinge4bac07c2007-07-17 18:37:06 -070035#include <linux/wait.h>
36#include <linux/interrupt.h>
37#include <linux/sched.h>
38#include <linux/err.h>
39#include <xen/xenbus.h>
40#include <asm/xen/hypervisor.h>
41#include <xen/events.h>
42#include <xen/page.h>
43#include "xenbus_comms.h"
44
45static int xenbus_irq;
46
47static DECLARE_WORK(probe_work, xenbus_probe);
48
49static DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
50
51static irqreturn_t wake_waiting(int irq, void *unused)
52{
53 if (unlikely(xenstored_ready == 0)) {
54 xenstored_ready = 1;
55 schedule_work(&probe_work);
56 }
57
58 wake_up(&xb_waitq);
59 return IRQ_HANDLED;
60}
61
62static int check_indexes(XENSTORE_RING_IDX cons, XENSTORE_RING_IDX prod)
63{
64 return ((prod - cons) <= XENSTORE_RING_SIZE);
65}
66
67static void *get_output_chunk(XENSTORE_RING_IDX cons,
68 XENSTORE_RING_IDX prod,
69 char *buf, uint32_t *len)
70{
71 *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod);
72 if ((XENSTORE_RING_SIZE - (prod - cons)) < *len)
73 *len = XENSTORE_RING_SIZE - (prod - cons);
74 return buf + MASK_XENSTORE_IDX(prod);
75}
76
77static const void *get_input_chunk(XENSTORE_RING_IDX cons,
78 XENSTORE_RING_IDX prod,
79 const char *buf, uint32_t *len)
80{
81 *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(cons);
82 if ((prod - cons) < *len)
83 *len = prod - cons;
84 return buf + MASK_XENSTORE_IDX(cons);
85}
86
87/**
88 * xb_write - low level write
89 * @data: buffer to send
90 * @len: length of buffer
91 *
92 * Returns 0 on success, error otherwise.
93 */
94int xb_write(const void *data, unsigned len)
95{
96 struct xenstore_domain_interface *intf = xen_store_interface;
97 XENSTORE_RING_IDX cons, prod;
98 int rc;
99
100 while (len != 0) {
101 void *dst;
102 unsigned int avail;
103
104 rc = wait_event_interruptible(
105 xb_waitq,
106 (intf->req_prod - intf->req_cons) !=
107 XENSTORE_RING_SIZE);
108 if (rc < 0)
109 return rc;
110
111 /* Read indexes, then verify. */
112 cons = intf->req_cons;
113 prod = intf->req_prod;
114 if (!check_indexes(cons, prod)) {
115 intf->req_cons = intf->req_prod = 0;
116 return -EIO;
117 }
118
119 dst = get_output_chunk(cons, prod, intf->req, &avail);
120 if (avail == 0)
121 continue;
122 if (avail > len)
123 avail = len;
124
125 /* Must write data /after/ reading the consumer index. */
126 mb();
127
128 memcpy(dst, data, avail);
129 data += avail;
130 len -= avail;
131
132 /* Other side must not see new producer until data is there. */
133 wmb();
134 intf->req_prod += avail;
135
136 /* Implies mb(): other side will see the updated producer. */
137 notify_remote_via_evtchn(xen_store_evtchn);
138 }
139
140 return 0;
141}
142
143int xb_data_to_read(void)
144{
145 struct xenstore_domain_interface *intf = xen_store_interface;
146 return (intf->rsp_cons != intf->rsp_prod);
147}
148
149int xb_wait_for_data_to_read(void)
150{
151 return wait_event_interruptible(xb_waitq, xb_data_to_read());
152}
153
154int xb_read(void *data, unsigned len)
155{
156 struct xenstore_domain_interface *intf = xen_store_interface;
157 XENSTORE_RING_IDX cons, prod;
158 int rc;
159
160 while (len != 0) {
161 unsigned int avail;
162 const char *src;
163
164 rc = xb_wait_for_data_to_read();
165 if (rc < 0)
166 return rc;
167
168 /* Read indexes, then verify. */
169 cons = intf->rsp_cons;
170 prod = intf->rsp_prod;
171 if (!check_indexes(cons, prod)) {
172 intf->rsp_cons = intf->rsp_prod = 0;
173 return -EIO;
174 }
175
176 src = get_input_chunk(cons, prod, intf->rsp, &avail);
177 if (avail == 0)
178 continue;
179 if (avail > len)
180 avail = len;
181
182 /* Must read data /after/ reading the producer index. */
183 rmb();
184
185 memcpy(data, src, avail);
186 data += avail;
187 len -= avail;
188
189 /* Other side must not see free space until we've copied out */
190 mb();
191 intf->rsp_cons += avail;
192
193 pr_debug("Finished read of %i bytes (%i to go)\n", avail, len);
194
195 /* Implies mb(): other side will see the updated consumer. */
196 notify_remote_via_evtchn(xen_store_evtchn);
197 }
198
199 return 0;
200}
201
202/**
203 * xb_init_comms - Set up interrupt handler off store event channel.
204 */
205int xb_init_comms(void)
206{
207 struct xenstore_domain_interface *intf = xen_store_interface;
Jeremy Fitzhardinge4bac07c2007-07-17 18:37:06 -0700208
209 if (intf->req_prod != intf->req_cons)
Joe Perches283c0972013-06-28 03:21:41 -0700210 pr_err("request ring is not quiescent (%08x:%08x)!\n",
211 intf->req_cons, intf->req_prod);
Jeremy Fitzhardinge4bac07c2007-07-17 18:37:06 -0700212
213 if (intf->rsp_prod != intf->rsp_cons) {
Joe Perches283c0972013-06-28 03:21:41 -0700214 pr_warn("response ring is not quiescent (%08x:%08x): fixing up\n",
215 intf->rsp_cons, intf->rsp_prod);
Olaf Hering116df6f2011-08-25 18:34:45 +0200216 /* breaks kdump */
217 if (!reset_devices)
218 intf->rsp_cons = intf->rsp_prod;
Jeremy Fitzhardinge4bac07c2007-07-17 18:37:06 -0700219 }
220
Jeremy Fitzhardinge7d88d322008-05-26 23:31:26 +0100221 if (xenbus_irq) {
222 /* Already have an irq; assume we're resuming */
223 rebind_evtchn_irq(xen_store_evtchn, xenbus_irq);
224 } else {
225 int err;
226 err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting,
227 0, "xenbus", &xb_waitq);
Stefano Stabelliniecc635f2012-09-14 12:13:12 +0100228 if (err < 0) {
Joe Perches283c0972013-06-28 03:21:41 -0700229 pr_err("request irq failed %i\n", err);
Jeremy Fitzhardinge7d88d322008-05-26 23:31:26 +0100230 return err;
231 }
Jeremy Fitzhardinge4bac07c2007-07-17 18:37:06 -0700232
Jeremy Fitzhardinge7d88d322008-05-26 23:31:26 +0100233 xenbus_irq = err;
Jeremy Fitzhardinge4bac07c2007-07-17 18:37:06 -0700234 }
235
Jeremy Fitzhardinge4bac07c2007-07-17 18:37:06 -0700236 return 0;
237}
Daniel De Graafd2fb4c52012-05-08 09:46:57 -0400238
239void xb_deinit_comms(void)
240{
241 unbind_from_irqhandler(xenbus_irq, &xb_waitq);
242 xenbus_irq = 0;
243}