1 /****************************************************************************** 2 * Talks to Xen Store to figure out what devices we have (backend half). 3 * 4 * Copyright (C) 2005 Rusty Russell, IBM Corporation 5 * Copyright (C) 2005 Mike Wray, Hewlett-Packard 6 * Copyright (C) 2005, 2006 XenSource Ltd 7 * Copyright (C) 2007 Solarflare Communications, Inc. 8 * 9 * This program is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU General Public License version 2 11 * as published by the Free Software Foundation; or, when distributed 12 * separately from the Linux kernel or incorporated into other 13 * software packages, subject to the following license: 14 * 15 * Permission is hereby granted, free of charge, to any person obtaining a copy 16 * of this source file (the "Software"), to deal in the Software without 17 * restriction, including without limitation the rights to use, copy, modify, 18 * merge, publish, distribute, sublicense, and/or sell copies of the Software, 19 * and to permit persons to whom the Software is furnished to do so, subject to 20 * the following conditions: 21 * 22 * The above copyright notice and this permission notice shall be included in 23 * all copies or substantial portions of the Software. 24 * 25 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 26 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 27 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 28 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 29 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 30 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 31 * IN THE SOFTWARE. 32 */ 33 34 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 35 36 #define DPRINTK(fmt, ...) \ 37 pr_debug("(%s:%d) " fmt "\n", \ 38 __func__, __LINE__, ##__VA_ARGS__) 39 40 #include <linux/kernel.h> 41 #include <linux/err.h> 42 #include <linux/string.h> 43 #include <linux/ctype.h> 44 #include <linux/fcntl.h> 45 #include <linux/mm.h> 46 #include <linux/notifier.h> 47 #include <linux/export.h> 48 #include <linux/semaphore.h> 49 50 #include <asm/page.h> 51 #include <asm/pgtable.h> 52 #include <asm/xen/hypervisor.h> 53 #include <asm/hypervisor.h> 54 #include <xen/xenbus.h> 55 #include <xen/features.h> 56 57 #include "xenbus.h" 58 59 /* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */ 60 static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename) 61 { 62 int domid, err; 63 const char *devid, *type, *frontend; 64 unsigned int typelen; 65 66 type = strchr(nodename, '/'); 67 if (!type) 68 return -EINVAL; 69 type++; 70 typelen = strcspn(type, "/"); 71 if (!typelen || type[typelen] != '/') 72 return -EINVAL; 73 74 devid = strrchr(nodename, '/') + 1; 75 76 err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid, 77 "frontend", NULL, &frontend, 78 NULL); 79 if (err) 80 return err; 81 if (strlen(frontend) == 0) 82 err = -ERANGE; 83 if (!err && !xenbus_exists(XBT_NIL, frontend, "")) 84 err = -ENOENT; 85 kfree(frontend); 86 87 if (err) 88 return err; 89 90 if (snprintf(bus_id, XEN_BUS_ID_SIZE, "%.*s-%i-%s", 91 typelen, type, domid, devid) >= XEN_BUS_ID_SIZE) 92 return -ENOSPC; 93 return 0; 94 } 95 96 static int xenbus_uevent_backend(struct device *dev, 97 struct kobj_uevent_env *env) 98 { 99 struct xenbus_device *xdev; 100 struct xenbus_driver *drv; 101 struct xen_bus_type *bus; 102 103 DPRINTK(""); 104 105 if (dev == NULL) 106 return -ENODEV; 107 108 xdev = to_xenbus_device(dev); 109 bus = container_of(xdev->dev.bus, struct xen_bus_type, bus); 110 111 if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype)) 112 return -ENOMEM; 113 114 /* stuff we want to pass to /sbin/hotplug */ 115 if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype)) 116 return -ENOMEM; 117 118 if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename)) 119 return -ENOMEM; 120 121 if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root)) 122 return -ENOMEM; 123 124 if (dev->driver) { 125 drv = to_xenbus_driver(dev->driver); 126 if (drv && drv->uevent) 127 return drv->uevent(xdev, env); 128 } 129 130 return 0; 131 } 132 133 /* backend/<typename>/<frontend-uuid>/<name> */ 134 static int xenbus_probe_backend_unit(struct xen_bus_type *bus, 135 const char *dir, 136 const char *type, 137 const char *name) 138 { 139 char *nodename; 140 int err; 141 142 nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name); 143 if (!nodename) 144 return -ENOMEM; 145 146 DPRINTK("%s\n", nodename); 147 148 err = xenbus_probe_node(bus, type, nodename); 149 kfree(nodename); 150 return err; 151 } 152 153 /* backend/<typename>/<frontend-domid> */ 154 static int xenbus_probe_backend(struct xen_bus_type *bus, const char *type, 155 const char *domid) 156 { 157 char *nodename; 158 int err = 0; 159 char **dir; 160 unsigned int i, dir_n = 0; 161 162 DPRINTK(""); 163 164 nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid); 165 if (!nodename) 166 return -ENOMEM; 167 168 dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n); 169 if (IS_ERR(dir)) { 170 kfree(nodename); 171 return PTR_ERR(dir); 172 } 173 174 for (i = 0; i < dir_n; i++) { 175 err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]); 176 if (err) 177 break; 178 } 179 kfree(dir); 180 kfree(nodename); 181 return err; 182 } 183 184 static void frontend_changed(struct xenbus_watch *watch, 185 const char *path, const char *token) 186 { 187 xenbus_otherend_changed(watch, path, token, 0); 188 } 189 190 static struct xen_bus_type xenbus_backend = { 191 .root = "backend", 192 .levels = 3, /* backend/type/<frontend>/<id> */ 193 .get_bus_id = backend_bus_id, 194 .probe = xenbus_probe_backend, 195 .otherend_changed = frontend_changed, 196 .bus = { 197 .name = "xen-backend", 198 .match = xenbus_match, 199 .uevent = xenbus_uevent_backend, 200 .probe = xenbus_dev_probe, 201 .remove = xenbus_dev_remove, 202 .dev_groups = xenbus_dev_groups, 203 }, 204 }; 205 206 static void backend_changed(struct xenbus_watch *watch, 207 const char *path, const char *token) 208 { 209 DPRINTK(""); 210 211 xenbus_dev_changed(path, &xenbus_backend); 212 } 213 214 static struct xenbus_watch be_watch = { 215 .node = "backend", 216 .callback = backend_changed, 217 }; 218 219 static int read_frontend_details(struct xenbus_device *xendev) 220 { 221 return xenbus_read_otherend_details(xendev, "frontend-id", "frontend"); 222 } 223 224 int xenbus_dev_is_online(struct xenbus_device *dev) 225 { 226 return !!xenbus_read_unsigned(dev->nodename, "online", 0); 227 } 228 EXPORT_SYMBOL_GPL(xenbus_dev_is_online); 229 230 int __xenbus_register_backend(struct xenbus_driver *drv, struct module *owner, 231 const char *mod_name) 232 { 233 drv->read_otherend_details = read_frontend_details; 234 235 return xenbus_register_driver_common(drv, &xenbus_backend, 236 owner, mod_name); 237 } 238 EXPORT_SYMBOL_GPL(__xenbus_register_backend); 239 240 static int backend_probe_and_watch(struct notifier_block *notifier, 241 unsigned long event, 242 void *data) 243 { 244 /* Enumerate devices in xenstore and watch for changes. */ 245 xenbus_probe_devices(&xenbus_backend); 246 register_xenbus_watch(&be_watch); 247 248 return NOTIFY_DONE; 249 } 250 251 static int backend_reclaim_memory(struct device *dev, void *data) 252 { 253 const struct xenbus_driver *drv; 254 struct xenbus_device *xdev; 255 256 if (!dev->driver) 257 return 0; 258 drv = to_xenbus_driver(dev->driver); 259 if (drv && drv->reclaim_memory) { 260 xdev = to_xenbus_device(dev); 261 if (down_trylock(&xdev->reclaim_sem)) 262 return 0; 263 drv->reclaim_memory(xdev); 264 up(&xdev->reclaim_sem); 265 } 266 return 0; 267 } 268 269 /* 270 * Returns 0 always because we are using shrinker to only detect memory 271 * pressure. 272 */ 273 static unsigned long backend_shrink_memory_count(struct shrinker *shrinker, 274 struct shrink_control *sc) 275 { 276 bus_for_each_dev(&xenbus_backend.bus, NULL, NULL, 277 backend_reclaim_memory); 278 return 0; 279 } 280 281 static struct shrinker backend_memory_shrinker = { 282 .count_objects = backend_shrink_memory_count, 283 .seeks = DEFAULT_SEEKS, 284 }; 285 286 static int __init xenbus_probe_backend_init(void) 287 { 288 static struct notifier_block xenstore_notifier = { 289 .notifier_call = backend_probe_and_watch 290 }; 291 int err; 292 293 DPRINTK(""); 294 295 /* Register ourselves with the kernel bus subsystem */ 296 err = bus_register(&xenbus_backend.bus); 297 if (err) 298 return err; 299 300 register_xenstore_notifier(&xenstore_notifier); 301 302 if (register_shrinker(&backend_memory_shrinker)) 303 pr_warn("shrinker registration failed\n"); 304 305 return 0; 306 } 307 subsys_initcall(xenbus_probe_backend_init); 308