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 #include <xen/mem-reservation.h>
  48
  49 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
  50
  51 #define BALLOON_CLASS_NAME "xen_memory"
  52
  53 static struct device balloon_dev;
  54
  55 static int register_balloon(struct device *dev);
  56
  57 /* React to a change in the target key */
  58 static void watch_target(struct xenbus_watch *watch,
  59                          const char *path, const char *token)
  60 {
  61         unsigned long long new_target, static_max;
  62         int err;
  63         static bool watch_fired;
  64         static long target_diff;
  65
  66         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
  67         if (err != 1) {
  68                 /* This is ok (for domain0 at least) - so just return */
  69                 return;
  70         }
  71
  72         /* The given memory/target value is in KiB, so it needs converting to
  73          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
  74          */
  75         new_target >>= PAGE_SHIFT - 10;
  76
  77         if (!watch_fired) {
  78                 watch_fired = true;
  79
  80                 if ((xenbus_scanf(XBT_NIL, "memory", "static-max",
  81                                   "%llu", &static_max) == 1) ||
  82                     (xenbus_scanf(XBT_NIL, "memory", "memory_static_max",
  83                                   "%llu", &static_max) == 1))
  84                         static_max >>= PAGE_SHIFT - 10;
  85                 else
  86                         static_max = balloon_stats.current_pages;
  87
  88                 target_diff = (xen_pv_domain() || xen_initial_domain()) ? 0
  89                                 : static_max - balloon_stats.target_pages;
  90         }
  91
  92         balloon_set_new_target(new_target - target_diff);
  93 }
  94 static struct xenbus_watch target_watch = {
  95         .node = "memory/target",
  96         .callback = watch_target,
  97 };
  98
  99
 100 static int balloon_init_watcher(struct notifier_block *notifier,
 101                                 unsigned long event,
 102                                 void *data)
 103 {
 104         int err;
 105
 106         err = register_xenbus_watch(&target_watch);
 107         if (err)
 108                 pr_err("Failed to set balloon watcher\n");
 109
 110         return NOTIFY_DONE;
 111 }
 112
 113 static struct notifier_block xenstore_notifier = {
 114         .notifier_call = balloon_init_watcher,
 115 };
 116
 117 void xen_balloon_init(void)
 118 {
 119         register_balloon(&balloon_dev);
 120
 121         register_xen_selfballooning(&balloon_dev);
 122
 123         register_xenstore_notifier(&xenstore_notifier);
 124 }
 125 EXPORT_SYMBOL_GPL(xen_balloon_init);
 126
 127 #define BALLOON_SHOW(name, format, args...)                             \
 128         static ssize_t show_##name(struct device *dev,                  \
 129                                    struct device_attribute *attr,       \
 130                                    char *buf)                           \
 131         {                                                               \
 132                 return sprintf(buf, format, ##args);                    \
 133         }                                                               \
 134         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 135
 136 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
 137 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
 138 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
 139
 140 static DEVICE_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
 141 static DEVICE_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
 142 static DEVICE_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
 143 static DEVICE_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
 144 static DEVICE_BOOL_ATTR(scrub_pages, 0644, xen_scrub_pages);
 145
 146 static ssize_t show_target_kb(struct device *dev, struct device_attribute *attr,
 147                               char *buf)
 148 {
 149         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
 150 }
 151
 152 static ssize_t store_target_kb(struct device *dev,
 153                                struct device_attribute *attr,
 154                                const char *buf,
 155                                size_t count)
 156 {
 157         char *endchar;
 158         unsigned long long target_bytes;
 159
 160         if (!capable(CAP_SYS_ADMIN))
 161                 return -EPERM;
 162
 163         target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
 164
 165         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 166
 167         return count;
 168 }
 169
 170 static DEVICE_ATTR(target_kb, S_IRUGO | S_IWUSR,
 171                    show_target_kb, store_target_kb);
 172
 173
 174 static ssize_t show_target(struct device *dev, struct device_attribute *attr,
 175                               char *buf)
 176 {
 177         return sprintf(buf, "%llu\n",
 178                        (unsigned long long)balloon_stats.target_pages
 179                        << PAGE_SHIFT);
 180 }
 181
 182 static ssize_t store_target(struct device *dev,
 183                             struct device_attribute *attr,
 184                             const char *buf,
 185                             size_t count)
 186 {
 187         char *endchar;
 188         unsigned long long target_bytes;
 189
 190         if (!capable(CAP_SYS_ADMIN))
 191                 return -EPERM;
 192
 193         target_bytes = memparse(buf, &endchar);
 194
 195         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 196
 197         return count;
 198 }
 199
 200 static DEVICE_ATTR(target, S_IRUGO | S_IWUSR,
 201                    show_target, store_target);
 202
 203
 204 static struct attribute *balloon_attrs[] = {
 205         &dev_attr_target_kb.attr,
 206         &dev_attr_target.attr,
 207         &dev_attr_schedule_delay.attr.attr,
 208         &dev_attr_max_schedule_delay.attr.attr,
 209         &dev_attr_retry_count.attr.attr,
 210         &dev_attr_max_retry_count.attr.attr,
 211         &dev_attr_scrub_pages.attr.attr,
 212         NULL
 213 };
 214
 215 static const struct attribute_group balloon_group = {
 216         .attrs = balloon_attrs
 217 };
 218
 219 static struct attribute *balloon_info_attrs[] = {
 220         &dev_attr_current_kb.attr,
 221         &dev_attr_low_kb.attr,
 222         &dev_attr_high_kb.attr,
 223         NULL
 224 };
 225
 226 static const struct attribute_group balloon_info_group = {
 227         .name = "info",
 228         .attrs = balloon_info_attrs
 229 };
 230
 231 static const struct attribute_group *balloon_groups[] = {
 232         &balloon_group,
 233         &balloon_info_group,
 234         NULL
 235 };
 236
 237 static struct bus_type balloon_subsys = {
 238         .name = BALLOON_CLASS_NAME,
 239         .dev_name = BALLOON_CLASS_NAME,
 240 };
 241
 242 static int register_balloon(struct device *dev)
 243 {
 244         int error;
 245
 246         error = subsys_system_register(&balloon_subsys, NULL);
 247         if (error)
 248                 return error;
 249
 250         dev->id = 0;
 251         dev->bus = &balloon_subsys;
 252         dev->groups = balloon_groups;
 253
 254         error = device_register(dev);
 255         if (error) {
 256                 bus_unregister(&balloon_subsys);
 257                 return error;
 258         }
 259
 260         return 0;
 261 }