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 *path, const char *token)
  59 {
  60         unsigned long long new_target;
  61         int err;
  62         static bool watch_fired;
  63         static long target_diff;
  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         new_target >>= PAGE_SHIFT - 10;
  75         if (watch_fired) {
  76                 balloon_set_new_target(new_target - target_diff);
  77                 return;
  78         }
  79
  80         watch_fired = true;
  81         target_diff = new_target - balloon_stats.target_pages;
  82 }
  83 static struct xenbus_watch target_watch = {
  84         .node = "memory/target",
  85         .callback = watch_target,
  86 };
  87
  88
  89 static int balloon_init_watcher(struct notifier_block *notifier,
  90                                 unsigned long event,
  91                                 void *data)
  92 {
  93         int err;
  94
  95         err = register_xenbus_watch(&target_watch);
  96         if (err)
  97                 pr_err("Failed to set balloon watcher\n");
  98
  99         return NOTIFY_DONE;
 100 }
 101
 102 static struct notifier_block xenstore_notifier = {
 103         .notifier_call = balloon_init_watcher,
 104 };
 105
 106 void xen_balloon_init(void)
 107 {
 108         register_balloon(&balloon_dev);
 109
 110         register_xen_selfballooning(&balloon_dev);
 111
 112         register_xenstore_notifier(&xenstore_notifier);
 113 }
 114 EXPORT_SYMBOL_GPL(xen_balloon_init);
 115
 116 #define BALLOON_SHOW(name, format, args...)                             \
 117         static ssize_t show_##name(struct device *dev,                  \
 118                                    struct device_attribute *attr,       \
 119                                    char *buf)                           \
 120         {                                                               \
 121                 return sprintf(buf, format, ##args);                    \
 122         }                                                               \
 123         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 124
 125 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
 126 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
 127 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
 128
 129 static DEVICE_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
 130 static DEVICE_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
 131 static DEVICE_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
 132 static DEVICE_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
 133
 134 static ssize_t show_target_kb(struct device *dev, struct device_attribute *attr,
 135                               char *buf)
 136 {
 137         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
 138 }
 139
 140 static ssize_t store_target_kb(struct device *dev,
 141                                struct device_attribute *attr,
 142                                const char *buf,
 143                                size_t count)
 144 {
 145         char *endchar;
 146         unsigned long long target_bytes;
 147
 148         if (!capable(CAP_SYS_ADMIN))
 149                 return -EPERM;
 150
 151         target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
 152
 153         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 154
 155         return count;
 156 }
 157
 158 static DEVICE_ATTR(target_kb, S_IRUGO | S_IWUSR,
 159                    show_target_kb, store_target_kb);
 160
 161
 162 static ssize_t show_target(struct device *dev, struct device_attribute *attr,
 163                               char *buf)
 164 {
 165         return sprintf(buf, "%llu\n",
 166                        (unsigned long long)balloon_stats.target_pages
 167                        << PAGE_SHIFT);
 168 }
 169
 170 static ssize_t store_target(struct device *dev,
 171                             struct device_attribute *attr,
 172                             const char *buf,
 173                             size_t count)
 174 {
 175         char *endchar;
 176         unsigned long long target_bytes;
 177
 178         if (!capable(CAP_SYS_ADMIN))
 179                 return -EPERM;
 180
 181         target_bytes = memparse(buf, &endchar);
 182
 183         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 184
 185         return count;
 186 }
 187
 188 static DEVICE_ATTR(target, S_IRUGO | S_IWUSR,
 189                    show_target, store_target);
 190
 191
 192 static struct attribute *balloon_attrs[] = {
 193         &dev_attr_target_kb.attr,
 194         &dev_attr_target.attr,
 195         &dev_attr_schedule_delay.attr.attr,
 196         &dev_attr_max_schedule_delay.attr.attr,
 197         &dev_attr_retry_count.attr.attr,
 198         &dev_attr_max_retry_count.attr.attr,
 199         NULL
 200 };
 201
 202 static const struct attribute_group balloon_group = {
 203         .attrs = balloon_attrs
 204 };
 205
 206 static struct attribute *balloon_info_attrs[] = {
 207         &dev_attr_current_kb.attr,
 208         &dev_attr_low_kb.attr,
 209         &dev_attr_high_kb.attr,
 210         NULL
 211 };
 212
 213 static const struct attribute_group balloon_info_group = {
 214         .name = "info",
 215         .attrs = balloon_info_attrs
 216 };
 217
 218 static const struct attribute_group *balloon_groups[] = {
 219         &balloon_group,
 220         &balloon_info_group,
 221         NULL
 222 };
 223
 224 static struct bus_type balloon_subsys = {
 225         .name = BALLOON_CLASS_NAME,
 226         .dev_name = BALLOON_CLASS_NAME,
 227 };
 228
 229 static int register_balloon(struct device *dev)
 230 {
 231         int error;
 232
 233         error = subsys_system_register(&balloon_subsys, NULL);
 234         if (error)
 235                 return error;
 236
 237         dev->id = 0;
 238         dev->bus = &balloon_subsys;
 239         dev->groups = balloon_groups;
 240
 241         error = device_register(dev);
 242         if (error) {
 243                 bus_unregister(&balloon_subsys);
 244                 return error;
 245         }
 246
 247         return 0;
 248 }