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