xref: /openbmc/linux/drivers/xen/xen-balloon.c (revision ba61bb17)
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 		err = xenbus_scanf(XBT_NIL, "memory", "static-max", "%llu",
79 				   &static_max);
80 		if (err != 1)
81 			static_max = new_target;
82 		else
83 			static_max >>= PAGE_SHIFT - 10;
84 		target_diff = xen_pv_domain() ? 0
85 				: static_max - balloon_stats.target_pages;
86 	}
87 
88 	balloon_set_new_target(new_target - target_diff);
89 }
90 static struct xenbus_watch target_watch = {
91 	.node = "memory/target",
92 	.callback = watch_target,
93 };
94 
95 
96 static int balloon_init_watcher(struct notifier_block *notifier,
97 				unsigned long event,
98 				void *data)
99 {
100 	int err;
101 
102 	err = register_xenbus_watch(&target_watch);
103 	if (err)
104 		pr_err("Failed to set balloon watcher\n");
105 
106 	return NOTIFY_DONE;
107 }
108 
109 static struct notifier_block xenstore_notifier = {
110 	.notifier_call = balloon_init_watcher,
111 };
112 
113 void xen_balloon_init(void)
114 {
115 	register_balloon(&balloon_dev);
116 
117 	register_xen_selfballooning(&balloon_dev);
118 
119 	register_xenstore_notifier(&xenstore_notifier);
120 }
121 EXPORT_SYMBOL_GPL(xen_balloon_init);
122 
123 #define BALLOON_SHOW(name, format, args...)				\
124 	static ssize_t show_##name(struct device *dev,			\
125 				   struct device_attribute *attr,	\
126 				   char *buf)				\
127 	{								\
128 		return sprintf(buf, format, ##args);			\
129 	}								\
130 	static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
131 
132 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
133 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
134 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
135 
136 static DEVICE_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
137 static DEVICE_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
138 static DEVICE_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
139 static DEVICE_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
140 
141 static ssize_t show_target_kb(struct device *dev, struct device_attribute *attr,
142 			      char *buf)
143 {
144 	return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
145 }
146 
147 static ssize_t store_target_kb(struct device *dev,
148 			       struct device_attribute *attr,
149 			       const char *buf,
150 			       size_t count)
151 {
152 	char *endchar;
153 	unsigned long long target_bytes;
154 
155 	if (!capable(CAP_SYS_ADMIN))
156 		return -EPERM;
157 
158 	target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
159 
160 	balloon_set_new_target(target_bytes >> PAGE_SHIFT);
161 
162 	return count;
163 }
164 
165 static DEVICE_ATTR(target_kb, S_IRUGO | S_IWUSR,
166 		   show_target_kb, store_target_kb);
167 
168 
169 static ssize_t show_target(struct device *dev, struct device_attribute *attr,
170 			      char *buf)
171 {
172 	return sprintf(buf, "%llu\n",
173 		       (unsigned long long)balloon_stats.target_pages
174 		       << PAGE_SHIFT);
175 }
176 
177 static ssize_t store_target(struct device *dev,
178 			    struct device_attribute *attr,
179 			    const char *buf,
180 			    size_t count)
181 {
182 	char *endchar;
183 	unsigned long long target_bytes;
184 
185 	if (!capable(CAP_SYS_ADMIN))
186 		return -EPERM;
187 
188 	target_bytes = memparse(buf, &endchar);
189 
190 	balloon_set_new_target(target_bytes >> PAGE_SHIFT);
191 
192 	return count;
193 }
194 
195 static DEVICE_ATTR(target, S_IRUGO | S_IWUSR,
196 		   show_target, store_target);
197 
198 
199 static struct attribute *balloon_attrs[] = {
200 	&dev_attr_target_kb.attr,
201 	&dev_attr_target.attr,
202 	&dev_attr_schedule_delay.attr.attr,
203 	&dev_attr_max_schedule_delay.attr.attr,
204 	&dev_attr_retry_count.attr.attr,
205 	&dev_attr_max_retry_count.attr.attr,
206 	NULL
207 };
208 
209 static const struct attribute_group balloon_group = {
210 	.attrs = balloon_attrs
211 };
212 
213 static struct attribute *balloon_info_attrs[] = {
214 	&dev_attr_current_kb.attr,
215 	&dev_attr_low_kb.attr,
216 	&dev_attr_high_kb.attr,
217 	NULL
218 };
219 
220 static const struct attribute_group balloon_info_group = {
221 	.name = "info",
222 	.attrs = balloon_info_attrs
223 };
224 
225 static const struct attribute_group *balloon_groups[] = {
226 	&balloon_group,
227 	&balloon_info_group,
228 	NULL
229 };
230 
231 static struct bus_type balloon_subsys = {
232 	.name = BALLOON_CLASS_NAME,
233 	.dev_name = BALLOON_CLASS_NAME,
234 };
235 
236 static int register_balloon(struct device *dev)
237 {
238 	int error;
239 
240 	error = subsys_system_register(&balloon_subsys, NULL);
241 	if (error)
242 		return error;
243 
244 	dev->id = 0;
245 	dev->bus = &balloon_subsys;
246 	dev->groups = balloon_groups;
247 
248 	error = device_register(dev);
249 	if (error) {
250 		bus_unregister(&balloon_subsys);
251 		return error;
252 	}
253 
254 	return 0;
255 }
256