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 /* React to a change in the target key */
  54 static void watch_target(struct xenbus_watch *watch,
  55                          const char **vec, unsigned int len)
  56 {
  57         unsigned long long new_target;
  58         int err;
  59
  60         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
  61         if (err != 1) {
  62                 /* This is ok (for domain0 at least) - so just return */
  63                 return;
  64         }
  65
  66         /* The given memory/target value is in KiB, so it needs converting to
  67          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
  68          */
  69         balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
  70 }
  71 static struct xenbus_watch target_watch = {
  72         .node = "memory/target",
  73         .callback = watch_target,
  74 };
  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         .notifier_call = balloon_init_watcher,
  92 };
  93
  94 static int __init balloon_init(void)
  95 {
  96         if (!xen_domain())
  97                 return -ENODEV;
  98
  99         pr_info("xen-balloon: Initialising balloon driver.\n");
 100
 101         register_balloon(&balloon_sysdev);
 102
 103         register_xen_selfballooning(&balloon_sysdev);
 104
 105         register_xenstore_notifier(&xenstore_notifier);
 106
 107         return 0;
 108 }
 109 subsys_initcall(balloon_init);
 110
 111 static void balloon_exit(void)
 112 {
 113     /* XXX - release balloon here */
 114     return;
 115 }
 116
 117 module_exit(balloon_exit);
 118
 119 #define BALLOON_SHOW(name, format, args...)                             \
 120         static ssize_t show_##name(struct sys_device *dev,              \
 121                                    struct sysdev_attribute *attr,       \
 122                                    char *buf)                           \
 123         {                                                               \
 124                 return sprintf(buf, format, ##args);                    \
 125         }                                                               \
 126         static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
 127
 128 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
 129 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
 130 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
 131
 132 static SYSDEV_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
 133 static SYSDEV_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
 134 static SYSDEV_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
 135 static SYSDEV_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
 136
 137 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
 138                               char *buf)
 139 {
 140         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
 141 }
 142
 143 static ssize_t store_target_kb(struct sys_device *dev,
 144                                struct sysdev_attribute *attr,
 145                                const char *buf,
 146                                size_t count)
 147 {
 148         char *endchar;
 149         unsigned long long target_bytes;
 150
 151         if (!capable(CAP_SYS_ADMIN))
 152                 return -EPERM;
 153
 154         target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
 155
 156         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 157
 158         return count;
 159 }
 160
 161 static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
 162                    show_target_kb, store_target_kb);
 163
 164
 165 static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr,
 166                               char *buf)
 167 {
 168         return sprintf(buf, "%llu\n",
 169                        (unsigned long long)balloon_stats.target_pages
 170                        << PAGE_SHIFT);
 171 }
 172
 173 static ssize_t store_target(struct sys_device *dev,
 174                             struct sysdev_attribute *attr,
 175                             const char *buf,
 176                             size_t count)
 177 {
 178         char *endchar;
 179         unsigned long long target_bytes;
 180
 181         if (!capable(CAP_SYS_ADMIN))
 182                 return -EPERM;
 183
 184         target_bytes = memparse(buf, &endchar);
 185
 186         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 187
 188         return count;
 189 }
 190
 191 static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
 192                    show_target, store_target);
 193
 194
 195 static struct sysdev_attribute *balloon_attrs[] = {
 196         &attr_target_kb,
 197         &attr_target,
 198         &attr_schedule_delay.attr,
 199         &attr_max_schedule_delay.attr,
 200         &attr_retry_count.attr,
 201         &attr_max_retry_count.attr
 202 };
 203
 204 static struct attribute *balloon_info_attrs[] = {
 205         &attr_current_kb.attr,
 206         &attr_low_kb.attr,
 207         &attr_high_kb.attr,
 208         NULL
 209 };
 210
 211 static struct attribute_group balloon_info_group = {
 212         .name = "info",
 213         .attrs = balloon_info_attrs
 214 };
 215
 216 static struct sysdev_class balloon_sysdev_class = {
 217         .name = BALLOON_CLASS_NAME
 218 };
 219
 220 static int register_balloon(struct sys_device *sysdev)
 221 {
 222         int i, error;
 223
 224         error = sysdev_class_register(&balloon_sysdev_class);
 225         if (error)
 226                 return error;
 227
 228         sysdev->id = 0;
 229         sysdev->cls = &balloon_sysdev_class;
 230
 231         error = sysdev_register(sysdev);
 232         if (error) {
 233                 sysdev_class_unregister(&balloon_sysdev_class);
 234                 return error;
 235         }
 236
 237         for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
 238                 error = sysdev_create_file(sysdev, balloon_attrs[i]);
 239                 if (error)
 240                         goto fail;
 241         }
 242
 243         error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
 244         if (error)
 245                 goto fail;
 246
 247         return 0;
 248
 249  fail:
 250         while (--i >= 0)
 251                 sysdev_remove_file(sysdev, balloon_attrs[i]);
 252         sysdev_unregister(sysdev);
 253         sysdev_class_unregister(&balloon_sysdev_class);
 254         return error;
 255 }
 256
 257 MODULE_LICENSE("GPL");