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