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/sysdev.h>
  36 #include <linux/capability.h>
  37
  38 #include <xen/xen.h>
  39 #include <xen/interface/xen.h>
  40 #include <xen/balloon.h>
  41 #include <xen/xenbus.h>
  42 #include <xen/features.h>
  43 #include <xen/page.h>
  44
  45 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
  46
  47 #define BALLOON_CLASS_NAME "xen_memory"
  48
  49 static struct sys_device balloon_sysdev;
  50
  51 static int register_balloon(struct sys_device *sysdev);
  52
  53 static struct xenbus_watch target_watch =
  54 {
  55         .node = "memory/target"
  56 };
  57
  58 /* React to a change in the target key */
  59 static void watch_target(struct xenbus_watch *watch,
  60                          const char **vec, unsigned int len)
  61 {
  62         unsigned long long new_target;
  63         int err;
  64
  65         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
  66         if (err != 1) {
  67                 /* This is ok (for domain0 at least) - so just return */
  68                 return;
  69         }
  70
  71         /* The given memory/target value is in KiB, so it needs converting to
  72          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
  73          */
  74         balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
  75 }
  76
  77 static int balloon_init_watcher(struct notifier_block *notifier,
  78                                 unsigned long event,
  79                                 void *data)
  80 {
  81         int err;
  82
  83         err = register_xenbus_watch(&target_watch);
  84         if (err)
  85                 printk(KERN_ERR "Failed to set balloon watcher\n");
  86
  87         return NOTIFY_DONE;
  88 }
  89
  90 static struct notifier_block xenstore_notifier;
  91
  92 static int __init balloon_init(void)
  93 {
  94         if (!xen_domain())
  95                 return -ENODEV;
  96
  97         pr_info("xen-balloon: Initialising balloon driver.\n");
  98
  99         register_balloon(&balloon_sysdev);
 100
 101         target_watch.callback = watch_target;
 102         xenstore_notifier.notifier_call = balloon_init_watcher;
 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 sys_device *dev,              \
 120                                    struct sysdev_attribute *attr,       \
 121                                    char *buf)                           \
 122         {                                                               \
 123                 return sprintf(buf, format, ##args);                    \
 124         }                                                               \
 125         static SYSDEV_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 SYSDEV_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
 132 static SYSDEV_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
 133 static SYSDEV_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
 134 static SYSDEV_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
 135
 136 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_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 sys_device *dev,
 143                                struct sysdev_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 SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
 161                    show_target_kb, store_target_kb);
 162
 163
 164 static ssize_t show_target(struct sys_device *dev, struct sysdev_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 sys_device *dev,
 173                             struct sysdev_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 SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
 191                    show_target, store_target);
 192
 193
 194 static struct sysdev_attribute *balloon_attrs[] = {
 195         &attr_target_kb,
 196         &attr_target,
 197         &attr_schedule_delay.attr,
 198         &attr_max_schedule_delay.attr,
 199         &attr_retry_count.attr,
 200         &attr_max_retry_count.attr
 201 };
 202
 203 static struct attribute *balloon_info_attrs[] = {
 204         &attr_current_kb.attr,
 205         &attr_low_kb.attr,
 206         &attr_high_kb.attr,
 207         NULL
 208 };
 209
 210 static struct attribute_group balloon_info_group = {
 211         .name = "info",
 212         .attrs = balloon_info_attrs
 213 };
 214
 215 static struct sysdev_class balloon_sysdev_class = {
 216         .name = BALLOON_CLASS_NAME
 217 };
 218
 219 static int register_balloon(struct sys_device *sysdev)
 220 {
 221         int i, error;
 222
 223         error = sysdev_class_register(&balloon_sysdev_class);
 224         if (error)
 225                 return error;
 226
 227         sysdev->id = 0;
 228         sysdev->cls = &balloon_sysdev_class;
 229
 230         error = sysdev_register(sysdev);
 231         if (error) {
 232                 sysdev_class_unregister(&balloon_sysdev_class);
 233                 return error;
 234         }
 235
 236         for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
 237                 error = sysdev_create_file(sysdev, balloon_attrs[i]);
 238                 if (error)
 239                         goto fail;
 240         }
 241
 242         error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
 243         if (error)
 244                 goto fail;
 245
 246         return 0;
 247
 248  fail:
 249         while (--i >= 0)
 250                 sysdev_remove_file(sysdev, balloon_attrs[i]);
 251         sysdev_unregister(sysdev);
 252         sysdev_class_unregister(&balloon_sysdev_class);
 253         return error;
 254 }
 255
 256 MODULE_LICENSE("GPL");