1 /******************************************************************************
4 * Low level code to talks to Xen Store: ringbuffer and event channel.
6 * Copyright (C) 2005 Rusty Russell, IBM Corporation
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:
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:
21 * The above copyright notice and this permission notice shall be included in
22 * all copies or substantial portions of the Software.
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
33 #include <asm/hypervisor.h>
34 #include <xen/evtchn.h>
35 #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 "xenbus_comms.h"
42 static int xenbus_irq;
44 extern void xenbus_probe(void *);
45 extern int xenstored_ready;
46 static DECLARE_WORK(probe_work, xenbus_probe, NULL);
48 DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
50 static inline struct xenstore_domain_interface *xenstore_domain_interface(void)
52 return mfn_to_virt(xen_start_info->store_mfn);
55 static irqreturn_t wake_waiting(int irq, void *unused, struct pt_regs *regs)
57 if (unlikely(xenstored_ready == 0)) {
59 schedule_work(&probe_work);
66 static int check_indexes(XENSTORE_RING_IDX cons, XENSTORE_RING_IDX prod)
68 return ((prod - cons) <= XENSTORE_RING_SIZE);
71 static void *get_output_chunk(XENSTORE_RING_IDX cons,
72 XENSTORE_RING_IDX prod,
73 char *buf, uint32_t *len)
75 *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod);
76 if ((XENSTORE_RING_SIZE - (prod - cons)) < *len)
77 *len = XENSTORE_RING_SIZE - (prod - cons);
78 return buf + MASK_XENSTORE_IDX(prod);
81 static const void *get_input_chunk(XENSTORE_RING_IDX cons,
82 XENSTORE_RING_IDX prod,
83 const char *buf, uint32_t *len)
85 *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(cons);
86 if ((prod - cons) < *len)
88 return buf + MASK_XENSTORE_IDX(cons);
91 int xb_write(const void *data, unsigned len)
93 struct xenstore_domain_interface *intf = xenstore_domain_interface();
94 XENSTORE_RING_IDX cons, prod;
101 rc = wait_event_interruptible(
103 (intf->req_prod - intf->req_cons) !=
108 /* Read indexes, then verify. */
109 cons = intf->req_cons;
110 prod = intf->req_prod;
112 if (!check_indexes(cons, prod)) {
113 intf->req_cons = intf->req_prod = 0;
117 dst = get_output_chunk(cons, prod, intf->req, &avail);
123 memcpy(dst, data, avail);
127 /* Other side must not see new header until data is there. */
129 intf->req_prod += avail;
131 /* This implies mb() before other side sees interrupt. */
132 notify_remote_via_evtchn(xen_start_info->store_evtchn);
138 int xb_read(void *data, unsigned len)
140 struct xenstore_domain_interface *intf = xenstore_domain_interface();
141 XENSTORE_RING_IDX cons, prod;
148 rc = wait_event_interruptible(
150 intf->rsp_cons != intf->rsp_prod);
154 /* Read indexes, then verify. */
155 cons = intf->rsp_cons;
156 prod = intf->rsp_prod;
158 if (!check_indexes(cons, prod)) {
159 intf->rsp_cons = intf->rsp_prod = 0;
163 src = get_input_chunk(cons, prod, intf->rsp, &avail);
169 /* We must read header before we read data. */
172 memcpy(data, src, avail);
176 /* Other side must not see free space until we've copied out */
178 intf->rsp_cons += avail;
180 pr_debug("Finished read of %i bytes (%i to go)\n", avail, len);
182 /* Implies mb(): they will see new header. */
183 notify_remote_via_evtchn(xen_start_info->store_evtchn);
189 /* Set up interrupt handler off store event channel. */
190 int xb_init_comms(void)
195 unbind_from_irqhandler(xenbus_irq, &xb_waitq);
197 err = bind_evtchn_to_irqhandler(
198 xen_start_info->store_evtchn, wake_waiting,
199 0, "xenbus", &xb_waitq);
201 printk(KERN_ERR "XENBUS request irq failed %i\n", err);