drivers/xen/xen-balloon.c

   1 /******************************************************************************
   2  * Xen balloon driver - enables returning/claiming memory to/from Xen.
   3  *
   4  * Copyright (c) 2003, B Dragovic
   5  * Copyright (c) 2003-2004, M Williamson, K Fraser
   6  * Copyright (c) 2005 Dan M. Smith, 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
  33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  34
  35 #include <linux/kernel.h>
  36 #include <linux/module.h>
  37 #include <linux/capability.h>
  38
  39 #include <xen/xen.h>
  40 #include <xen/interface/xen.h>
  41 #include <xen/balloon.h>
  42 #include <xen/xenbus.h>
  43 #include <xen/features.h>
  44 #include <xen/page.h>
  45
  46 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
  47
  48 #define BALLOON_CLASS_NAME "xen_memory"
  49
  50 static struct device balloon_dev;
  51
  52 static int register_balloon(struct device *dev);
  53
  54 /* React to a change in the target key */
  55 static void watch_target(struct xenbus_watch *watch,
  56                          const char **vec, unsigned int len)
  57 {
  58         unsigned long long new_target;
  59         int err;
  60
  61         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
  62         if (err != 1) {
  63                 /* This is ok (for domain0 at least) - so just return */
  64                 return;
  65         }
  66
  67         /* The given memory/target value is in KiB, so it needs converting to
  68          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
  69          */
  70         balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
  71 }
  72 static struct xenbus_watch target_watch = {
  73         .node = "memory/target",
  74         .callback = watch_target,
  75 };
  76
  77
  78 static int balloon_init_watcher(struct notifier_block *notifier,
  79                                 unsigned long event,
  80                                 void *data)
  81 {
  82         int err;
  83
  84         err = register_xenbus_watch(&target_watch);
  85         if (err)
  86                 pr_err("Failed to set balloon watcher\n");
  87
  88         return NOTIFY_DONE;
  89 }
  90
  91 static struct notifier_block xenstore_notifier = {
  92         .notifier_call = balloon_init_watcher,
  93 };
  94
  95 static int __init balloon_init(void)
  96 {
  97         if (!xen_domain())
  98                 return -ENODEV;
  99
 100         pr_info("Initialising balloon driver\n");
 101
 102         register_balloon(&balloon_dev);
 103
 104         register_xen_selfballooning(&balloon_dev);
 105
 106         register_xenstore_notifier(&xenstore_notifier);
 107
 108         return 0;
 109 }
 110 subsys_initcall(balloon_init);
 111
 112 static void balloon_exit(void)
 113 {
 114     /* XXX - release balloon here */
 115     return;
 116 }
 117
 118 module_exit(balloon_exit);
 119
 120 #define BALLOON_SHOW(name, format, args...)                             \
 121         static ssize_t show_##name(struct device *dev,                  \
 122                                    struct device_attribute *attr,       \
 123                                    char *buf)                           \
 124         {                                                               \
 125                 return sprintf(buf, format, ##args);                    \
 126         }                                                               \
 127         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 128
 129 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
 130 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
 131 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
 132
 133 static DEVICE_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
 134 static DEVICE_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
 135 static DEVICE_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
 136 static DEVICE_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
 137
 138 static ssize_t show_target_kb(struct device *dev, struct device_attribute *attr,
 139                               char *buf)
 140 {
 141         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
 142 }
 143
 144 static ssize_t store_target_kb(struct device *dev,
 145                                struct device_attribute *attr,
 146                                const char *buf,
 147                                size_t count)
 148 {
 149         char *endchar;
 150         unsigned long long target_bytes;
 151
 152         if (!capable(CAP_SYS_ADMIN))
 153                 return -EPERM;
 154
 155         target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
 156
 157         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 158
 159         return count;
 160 }
 161
 162 static DEVICE_ATTR(target_kb, S_IRUGO | S_IWUSR,
 163                    show_target_kb, store_target_kb);
 164
 165
 166 static ssize_t show_target(struct device *dev, struct device_attribute *attr,
 167                               char *buf)
 168 {
 169         return sprintf(buf, "%llu\n",
 170                        (unsigned long long)balloon_stats.target_pages
 171                        << PAGE_SHIFT);
 172 }
 173
 174 static ssize_t store_target(struct device *dev,
 175                             struct device_attribute *attr,
 176                             const char *buf,
 177                             size_t count)
 178 {
 179         char *endchar;
 180         unsigned long long target_bytes;
 181
 182         if (!capable(CAP_SYS_ADMIN))
 183                 return -EPERM;
 184
 185         target_bytes = memparse(buf, &endchar);
 186
 187         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 188
 189         return count;
 190 }
 191
 192 static DEVICE_ATTR(target, S_IRUGO | S_IWUSR,
 193                    show_target, store_target);
 194
 195
 196 static struct device_attribute *balloon_attrs[] = {
 197         &dev_attr_target_kb,
 198         &dev_attr_target,
 199         &dev_attr_schedule_delay.attr,
 200         &dev_attr_max_schedule_delay.attr,
 201         &dev_attr_retry_count.attr,
 202         &dev_attr_max_retry_count.attr
 203 };
 204
 205 static struct attribute *balloon_info_attrs[] = {
 206         &dev_attr_current_kb.attr,
 207         &dev_attr_low_kb.attr,
 208         &dev_attr_high_kb.attr,
 209         NULL
 210 };
 211
 212 static const struct attribute_group balloon_info_group = {
 213         .name = "info",
 214         .attrs = balloon_info_attrs
 215 };
 216
 217 static struct bus_type balloon_subsys = {
 218         .name = BALLOON_CLASS_NAME,
 219         .dev_name = BALLOON_CLASS_NAME,
 220 };
 221
 222 static int register_balloon(struct device *dev)
 223 {
 224         int i, error;
 225
 226         error = subsys_system_register(&balloon_subsys, NULL);
 227         if (error)
 228                 return error;
 229
 230         dev->id = 0;
 231         dev->bus = &balloon_subsys;
 232
 233         error = device_register(dev);
 234         if (error) {
 235                 bus_unregister(&balloon_subsys);
 236                 return error;
 237         }
 238
 239         for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
 240                 error = device_create_file(dev, balloon_attrs[i]);
 241                 if (error)
 242                         goto fail;
 243         }
 244
 245         error = sysfs_create_group(&dev->kobj, &balloon_info_group);
 246         if (error)
 247                 goto fail;
 248
 249         return 0;
 250
 251  fail:
 252         while (--i >= 0)
 253                 device_remove_file(dev, balloon_attrs[i]);
 254         device_unregister(dev);
 255         bus_unregister(&balloon_subsys);
 256         return error;
 257 }
 258
 259 MODULE_LICENSE("GPL");