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