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 #include <linux/memory_hotplug.h>
  41
  42 #include <xen/xen.h>
  43 #include <xen/interface/xen.h>
  44 #include <xen/balloon.h>
  45 #include <xen/xenbus.h>
  46 #include <xen/features.h>
  47 #include <xen/page.h>
  48 #include <xen/mem-reservation.h>
  49
  50 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
  51
  52 #define BALLOON_CLASS_NAME "xen_memory"
  53
  54 #ifdef CONFIG_MEMORY_HOTPLUG
  55 u64 xen_saved_max_mem_size = 0;
  56 #endif
  57
  58 static struct device balloon_dev;
  59
  60 static int register_balloon(struct device *dev);
  61
  62 /* React to a change in the target key */
  63 static void watch_target(struct xenbus_watch *watch,
  64                          const char *path, const char *token)
  65 {
  66         unsigned long long new_target, static_max;
  67         int err;
  68         static bool watch_fired;
  69         static long target_diff;
  70
  71 #ifdef CONFIG_MEMORY_HOTPLUG
  72         /* The balloon driver will take care of adding memory now. */
  73         if (xen_saved_max_mem_size)
  74                 max_mem_size = xen_saved_max_mem_size;
  75 #endif
  76
  77         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
  78         if (err != 1) {
  79                 /* This is ok (for domain0 at least) - so just return */
  80                 return;
  81         }
  82
  83         /* The given memory/target value is in KiB, so it needs converting to
  84          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
  85          */
  86         new_target >>= PAGE_SHIFT - 10;
  87
  88         if (!watch_fired) {
  89                 watch_fired = true;
  90
  91                 if ((xenbus_scanf(XBT_NIL, "memory", "static-max",
  92                                   "%llu", &static_max) == 1) ||
  93                     (xenbus_scanf(XBT_NIL, "memory", "memory_static_max",
  94                                   "%llu", &static_max) == 1))
  95                         static_max >>= PAGE_SHIFT - 10;
  96                 else
  97                         static_max = balloon_stats.current_pages;
  98
  99                 target_diff = (xen_pv_domain() || xen_initial_domain()) ? 0
 100                                 : static_max - balloon_stats.target_pages;
 101         }
 102
 103         balloon_set_new_target(new_target - target_diff);
 104 }
 105 static struct xenbus_watch target_watch = {
 106         .node = "memory/target",
 107         .callback = watch_target,
 108 };
 109
 110
 111 static int balloon_init_watcher(struct notifier_block *notifier,
 112                                 unsigned long event,
 113                                 void *data)
 114 {
 115         int err;
 116
 117         err = register_xenbus_watch(&target_watch);
 118         if (err)
 119                 pr_err("Failed to set balloon watcher\n");
 120
 121         return NOTIFY_DONE;
 122 }
 123
 124 static struct notifier_block xenstore_notifier = {
 125         .notifier_call = balloon_init_watcher,
 126 };
 127
 128 void xen_balloon_init(void)
 129 {
 130         register_balloon(&balloon_dev);
 131
 132         register_xenstore_notifier(&xenstore_notifier);
 133 }
 134 EXPORT_SYMBOL_GPL(xen_balloon_init);
 135
 136 #define BALLOON_SHOW(name, format, args...)                             \
 137         static ssize_t name##_show(struct device *dev,                  \
 138                                    struct device_attribute *attr,       \
 139                                    char *buf)                           \
 140         {                                                               \
 141                 return sprintf(buf, format, ##args);                    \
 142         }                                                               \
 143         static DEVICE_ATTR_RO(name)
 144
 145 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
 146 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
 147 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
 148
 149 static DEVICE_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
 150 static DEVICE_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
 151 static DEVICE_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
 152 static DEVICE_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
 153 static DEVICE_BOOL_ATTR(scrub_pages, 0644, xen_scrub_pages);
 154
 155 static ssize_t target_kb_show(struct device *dev, struct device_attribute *attr,
 156                               char *buf)
 157 {
 158         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
 159 }
 160
 161 static ssize_t target_kb_store(struct device *dev,
 162                                struct device_attribute *attr,
 163                                const char *buf, size_t count)
 164 {
 165         char *endchar;
 166         unsigned long long target_bytes;
 167
 168         if (!capable(CAP_SYS_ADMIN))
 169                 return -EPERM;
 170
 171         target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
 172
 173         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 174
 175         return count;
 176 }
 177
 178 static DEVICE_ATTR_RW(target_kb);
 179
 180 static ssize_t target_show(struct device *dev, struct device_attribute *attr,
 181                            char *buf)
 182 {
 183         return sprintf(buf, "%llu\n",
 184                        (unsigned long long)balloon_stats.target_pages
 185                        << PAGE_SHIFT);
 186 }
 187
 188 static ssize_t target_store(struct device *dev,
 189                             struct device_attribute *attr,
 190                             const char *buf, size_t count)
 191 {
 192         char *endchar;
 193         unsigned long long target_bytes;
 194
 195         if (!capable(CAP_SYS_ADMIN))
 196                 return -EPERM;
 197
 198         target_bytes = memparse(buf, &endchar);
 199
 200         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 201
 202         return count;
 203 }
 204
 205 static DEVICE_ATTR_RW(target);
 206
 207 static struct attribute *balloon_attrs[] = {
 208         &dev_attr_target_kb.attr,
 209         &dev_attr_target.attr,
 210         &dev_attr_schedule_delay.attr.attr,
 211         &dev_attr_max_schedule_delay.attr.attr,
 212         &dev_attr_retry_count.attr.attr,
 213         &dev_attr_max_retry_count.attr.attr,
 214         &dev_attr_scrub_pages.attr.attr,
 215         NULL
 216 };
 217
 218 static const struct attribute_group balloon_group = {
 219         .attrs = balloon_attrs
 220 };
 221
 222 static struct attribute *balloon_info_attrs[] = {
 223         &dev_attr_current_kb.attr,
 224         &dev_attr_low_kb.attr,
 225         &dev_attr_high_kb.attr,
 226         NULL
 227 };
 228
 229 static const struct attribute_group balloon_info_group = {
 230         .name = "info",
 231         .attrs = balloon_info_attrs
 232 };
 233
 234 static const struct attribute_group *balloon_groups[] = {
 235         &balloon_group,
 236         &balloon_info_group,
 237         NULL
 238 };
 239
 240 static struct bus_type balloon_subsys = {
 241         .name = BALLOON_CLASS_NAME,
 242         .dev_name = BALLOON_CLASS_NAME,
 243 };
 244
 245 static int register_balloon(struct device *dev)
 246 {
 247         int error;
 248
 249         error = subsys_system_register(&balloon_subsys, NULL);
 250         if (error)
 251                 return error;
 252
 253         dev->id = 0;
 254         dev->bus = &balloon_subsys;
 255         dev->groups = balloon_groups;
 256
 257         error = device_register(dev);
 258         if (error) {
 259                 bus_unregister(&balloon_subsys);
 260                 return error;
 261         }
 262
 263         return 0;
 264 }