xenbus_comms.c revision 1.1
1 /****************************************************************************** 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 file may be distributed separately from the Linux kernel, or 9 * incorporated into other software packages, subject to the following license: 10 * 11 * Permission is hereby granted, free of charge, to any person obtaining a copy 12 * of this source file (the "Software"), to deal in the Software without 13 * restriction, including without limitation the rights to use, copy, modify, 14 * merge, publish, distribute, sublicense, and/or sell copies of the Software, 15 * and to permit persons to whom the Software is furnished to do so, subject to 16 * the following conditions: 17 * 18 * The above copyright notice and this permission notice shall be included in 19 * all copies or substantial portions of the Software. 20 * 21 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 22 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 23 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 24 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 25 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 26 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 27 * IN THE SOFTWARE. 28 */ 29 30 #include <asm/hypervisor.h> 31 #include <asm-xen/evtchn.h> 32 #include <linux/wait.h> 33 #include <linux/interrupt.h> 34 #include <linux/sched.h> 35 #include <linux/err.h> 36 #include <asm-xen/xenbus.h> 37 #include "xenbus_comms.h" 38 39 static int xenbus_irq; 40 41 extern void xenbus_probe(void *); 42 extern int xenstored_ready; 43 static DECLARE_WORK(probe_work, xenbus_probe, NULL); 44 45 DECLARE_WAIT_QUEUE_HEAD(xb_waitq); 46 47 static inline struct xenstore_domain_interface *xenstore_domain_interface(void) 48 { 49 return mfn_to_virt(xen_start_info->store_mfn); 50 } 51 52 static irqreturn_t wake_waiting(int irq, void *unused, struct pt_regs *regs) 53 { 54 if (unlikely(xenstored_ready == 0)) { 55 xenstored_ready = 1; 56 schedule_work(&probe_work); 57 } 58 59 wake_up(&xb_waitq); 60 return IRQ_HANDLED; 61 } 62 63 static int check_indexes(XENSTORE_RING_IDX cons, XENSTORE_RING_IDX prod) 64 { 65 return ((prod - cons) <= XENSTORE_RING_SIZE); 66 } 67 68 static void *get_output_chunk(XENSTORE_RING_IDX cons, 69 XENSTORE_RING_IDX prod, 70 char *buf, uint32_t *len) 71 { 72 *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod); 73 if ((XENSTORE_RING_SIZE - (prod - cons)) < *len) 74 *len = XENSTORE_RING_SIZE - (prod - cons); 75 return buf + MASK_XENSTORE_IDX(prod); 76 } 77 78 static const void *get_input_chunk(XENSTORE_RING_IDX cons, 79 XENSTORE_RING_IDX prod, 80 const char *buf, uint32_t *len) 81 { 82 *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(cons); 83 if ((prod - cons) < *len) 84 *len = prod - cons; 85 return buf + MASK_XENSTORE_IDX(cons); 86 } 87 88 int xb_write(const void *data, unsigned len) 89 { 90 struct xenstore_domain_interface *intf = xenstore_domain_interface(); 91 XENSTORE_RING_IDX cons, prod; 92 93 while (len != 0) { 94 void *dst; 95 unsigned int avail; 96 97 wait_event_interruptible(xb_waitq, 98 (intf->req_prod - intf->req_cons) != 99 XENSTORE_RING_SIZE); 100 101 /* Read indexes, then verify. */ 102 cons = intf->req_cons; 103 prod = intf->req_prod; 104 mb(); 105 if (!check_indexes(cons, prod)) 106 return -EIO; 107 108 dst = get_output_chunk(cons, prod, intf->req, &avail); 109 if (avail == 0) 110 continue; 111 if (avail > len) 112 avail = len; 113 114 memcpy(dst, data, avail); 115 data += avail; 116 len -= avail; 117 118 /* Other side must not see new header until data is there. */ 119 wmb(); 120 intf->req_prod += avail; 121 122 /* This implies mb() before other side sees interrupt. */ 123 notify_remote_via_evtchn(xen_start_info->store_evtchn); 124 } 125 126 return 0; 127 } 128 129 int xb_read(void *data, unsigned len) 130 { 131 struct xenstore_domain_interface *intf = xenstore_domain_interface(); 132 XENSTORE_RING_IDX cons, prod; 133 134 while (len != 0) { 135 unsigned int avail; 136 const char *src; 137 138 wait_event_interruptible(xb_waitq, 139 intf->rsp_cons != intf->rsp_prod); 140 141 /* Read indexes, then verify. */ 142 cons = intf->rsp_cons; 143 prod = intf->rsp_prod; 144 mb(); 145 if (!check_indexes(cons, prod)) 146 return -EIO; 147 148 src = get_input_chunk(cons, prod, intf->rsp, &avail); 149 if (avail == 0) 150 continue; 151 if (avail > len) 152 avail = len; 153 154 /* We must read header before we read data. */ 155 rmb(); 156 157 memcpy(data, src, avail); 158 data += avail; 159 len -= avail; 160 161 /* Other side must not see free space until we've copied out */ 162 mb(); 163 intf->rsp_cons += avail; 164 165 pr_debug("Finished read of %i bytes (%i to go)\n", avail, len); 166 167 /* Implies mb(): they will see new header. */ 168 notify_remote_via_evtchn(xen_start_info->store_evtchn); 169 } 170 171 return 0; 172 } 173 174 /* Set up interrupt handler off store event channel. */ 175 int xb_init_comms(void) 176 { 177 int err; 178 179 if (xenbus_irq) 180 unbind_from_irqhandler(xenbus_irq, &xb_waitq); 181 182 err = bind_evtchn_to_irqhandler( 183 xen_start_info->store_evtchn, wake_waiting, 184 0, "xenbus", &xb_waitq); 185 if (err <= 0) { 186 printk(KERN_ERR "XENBUS request irq failed %i\n", err); 187 return err; 188 } 189 190 xenbus_irq = err; 191 192 return 0; 193 } 194 195 /* 196 * Local variables: 197 * c-file-style: "linux" 198 * indent-tabs-mode: t 199 * c-indent-level: 8 200 * c-basic-offset: 8 201 * tab-width: 8 202 * End: 203 */ 204
Indexes created Tue Sep 23 02:09:52 GMT 2025