xref: /openbmc/linux/drivers/xen/xen-balloon.c (revision 52c291a3)
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 }
249