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 */
watch_target(struct xenbus_watch * watch,const char * path,const char * token)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
balloon_init_watcher(struct notifier_block * notifier,unsigned long event,void * data)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
xen_balloon_init(void)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
target_kb_show(struct device * dev,struct device_attribute * attr,char * buf)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
target_kb_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)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
target_show(struct device * dev,struct device_attribute * attr,char * buf)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
target_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)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
register_balloon(struct device * dev)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 }
265