xref: /openbmc/linux/drivers/xen/xen-balloon.c (revision 20600617)
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