xen-balloon: Move core balloon functionality out of module

The basic functionality of ballooning pages is useful for Xen drivers in
general. Rather than require a dependency on the balloon module, split
the functionality that is reused into the core. The balloon module is
still required to follow ballooning requests from xenstore or to view
balloon statistics in sysfs.

Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 256 insertions, 0 deletions

diff --git a/drivers/xen/xen-balloon.c b/drivers/xen/xen-balloon.c
new file mode 100644
index 000000000000..a4ff225ee868
--- /dev/null
+++ b/drivers/xen/xen-balloon.c
@@ -0,0 +1,256 @@
+/******************************************************************************
+ * Xen balloon driver - enables returning/claiming memory to/from Xen.
+ *
+ * Copyright (c) 2003, B Dragovic
+ * Copyright (c) 2003-2004, M Williamson, K Fraser
+ * Copyright (c) 2005 Dan M. Smith, IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sysdev.h>
+#include <linux/capability.h>
+
+#include <xen/xen.h>
+#include <xen/interface/xen.h>
+#include <xen/balloon.h>
+#include <xen/xenbus.h>
+#include <xen/features.h>
+#include <xen/page.h>
+
+#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
+
+#define BALLOON_CLASS_NAME "xen_memory"
+
+static struct sys_device balloon_sysdev;
+
+static int register_balloon(struct sys_device *sysdev);
+
+static struct xenbus_watch target_watch =
+{
+        .node = "memory/target"
+};
+
+/* React to a change in the target key */
+static void watch_target(struct xenbus_watch *watch,
+                         const char **vec, unsigned int len)
+{
+        unsigned long long new_target;
+        int err;
+
+        err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
+        if (err != 1) {
+                /* This is ok (for domain0 at least) - so just return */
+                return;
+        }
+
+        /* The given memory/target value is in KiB, so it needs converting to
+         * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
+         */
+        balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
+}
+
+static int balloon_init_watcher(struct notifier_block *notifier,
+                                unsigned long event,
+                                void *data)
+{
+        int err;
+
+        err = register_xenbus_watch(&target_watch);
+        if (err)
+                printk(KERN_ERR "Failed to set balloon watcher\n");
+
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block xenstore_notifier;
+
+static int __init balloon_init(void)
+{
+        if (!xen_domain())
+                return -ENODEV;
+
+        pr_info("xen-balloon: Initialising balloon driver.\n");
+
+        register_balloon(&balloon_sysdev);
+
+        target_watch.callback = watch_target;
+        xenstore_notifier.notifier_call = balloon_init_watcher;
+
+        register_xenstore_notifier(&xenstore_notifier);
+
+        return 0;
+}
+subsys_initcall(balloon_init);
+
+static void balloon_exit(void)
+{
+    /* XXX - release balloon here */
+    return;
+}
+
+module_exit(balloon_exit);
+
+#define BALLOON_SHOW(name, format, args...)                             \
+        static ssize_t show_##name(struct sys_device *dev,              \
+                                   struct sysdev_attribute *attr,       \
+                                   char *buf)                           \
+        {                                                               \
+                return sprintf(buf, format, ##args);                    \
+        }                                                               \
+        static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
+
+BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
+BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
+BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
+
+static SYSDEV_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
+static SYSDEV_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
+static SYSDEV_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
+static SYSDEV_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
+
+static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
+                              char *buf)
+{
+        return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
+}
+
+static ssize_t store_target_kb(struct sys_device *dev,
+                               struct sysdev_attribute *attr,
+                               const char *buf,
+                               size_t count)
+{
+        char *endchar;
+        unsigned long long target_bytes;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
+
+        balloon_set_new_target(target_bytes >> PAGE_SHIFT);
+
+        return count;
+}
+
+static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
+                   show_target_kb, store_target_kb);
+
+
+static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr,
+                              char *buf)
+{
+        return sprintf(buf, "%llu\n",
+                       (unsigned long long)balloon_stats.target_pages
+                       << PAGE_SHIFT);
+}
+
+static ssize_t store_target(struct sys_device *dev,
+                            struct sysdev_attribute *attr,
+                            const char *buf,
+                            size_t count)
+{
+        char *endchar;
+        unsigned long long target_bytes;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        target_bytes = memparse(buf, &endchar);
+
+        balloon_set_new_target(target_bytes >> PAGE_SHIFT);
+
+        return count;
+}
+
+static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
+                   show_target, store_target);
+
+
+static struct sysdev_attribute *balloon_attrs[] = {
+        &attr_target_kb,
+        &attr_target,
+        &attr_schedule_delay.attr,
+        &attr_max_schedule_delay.attr,
+        &attr_retry_count.attr,
+        &attr_max_retry_count.attr
+};
+
+static struct attribute *balloon_info_attrs[] = {
+        &attr_current_kb.attr,
+        &attr_low_kb.attr,
+        &attr_high_kb.attr,
+        NULL
+};
+
+static struct attribute_group balloon_info_group = {
+        .name = "info",
+        .attrs = balloon_info_attrs
+};
+
+static struct sysdev_class balloon_sysdev_class = {
+        .name = BALLOON_CLASS_NAME
+};
+
+static int register_balloon(struct sys_device *sysdev)
+{
+        int i, error;
+
+        error = sysdev_class_register(&balloon_sysdev_class);
+        if (error)
+                return error;
+
+        sysdev->id = 0;
+        sysdev->cls = &balloon_sysdev_class;
+
+        error = sysdev_register(sysdev);
+        if (error) {
+                sysdev_class_unregister(&balloon_sysdev_class);
+                return error;
+        }
+
+        for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
+                error = sysdev_create_file(sysdev, balloon_attrs[i]);
+                if (error)
+                        goto fail;
+        }
+
+        error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
+        if (error)
+                goto fail;
+
+        return 0;
+
+ fail:
+        while (--i >= 0)
+                sysdev_remove_file(sysdev, balloon_attrs[i]);
+        sysdev_unregister(sysdev);
+        sysdev_class_unregister(&balloon_sysdev_class);
+        return error;
+}
+
+MODULE_LICENSE("GPL");