v4.19.13 snapshot.
diff --git a/drivers/xen/xen-balloon.c b/drivers/xen/xen-balloon.c
new file mode 100644
index 0000000..2acbfe1
--- /dev/null
+++ b/drivers/xen/xen-balloon.c
@@ -0,0 +1,261 @@
+/******************************************************************************
+ * 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.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/mm_types.h>
+#include <linux/init.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>
+#include <xen/mem-reservation.h>
+
+#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
+
+#define BALLOON_CLASS_NAME "xen_memory"
+
+static struct device balloon_dev;
+
+static int register_balloon(struct device *dev);
+
+/* React to a change in the target key */
+static void watch_target(struct xenbus_watch *watch,
+ const char *path, const char *token)
+{
+ unsigned long long new_target, static_max;
+ int err;
+ static bool watch_fired;
+ static long target_diff;
+
+ 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.
+ */
+ new_target >>= PAGE_SHIFT - 10;
+
+ if (!watch_fired) {
+ watch_fired = true;
+
+ if ((xenbus_scanf(XBT_NIL, "memory", "static-max",
+ "%llu", &static_max) == 1) ||
+ (xenbus_scanf(XBT_NIL, "memory", "memory_static_max",
+ "%llu", &static_max) == 1))
+ static_max >>= PAGE_SHIFT - 10;
+ else
+ static_max = new_target;
+
+ target_diff = (xen_pv_domain() || xen_initial_domain()) ? 0
+ : static_max - balloon_stats.target_pages;
+ }
+
+ balloon_set_new_target(new_target - target_diff);
+}
+static struct xenbus_watch target_watch = {
+ .node = "memory/target",
+ .callback = watch_target,
+};
+
+
+static int balloon_init_watcher(struct notifier_block *notifier,
+ unsigned long event,
+ void *data)
+{
+ int err;
+
+ err = register_xenbus_watch(&target_watch);
+ if (err)
+ pr_err("Failed to set balloon watcher\n");
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block xenstore_notifier = {
+ .notifier_call = balloon_init_watcher,
+};
+
+void xen_balloon_init(void)
+{
+ register_balloon(&balloon_dev);
+
+ register_xen_selfballooning(&balloon_dev);
+
+ register_xenstore_notifier(&xenstore_notifier);
+}
+EXPORT_SYMBOL_GPL(xen_balloon_init);
+
+#define BALLOON_SHOW(name, format, args...) \
+ static ssize_t show_##name(struct device *dev, \
+ struct device_attribute *attr, \
+ char *buf) \
+ { \
+ return sprintf(buf, format, ##args); \
+ } \
+ static DEVICE_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 DEVICE_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
+static DEVICE_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
+static DEVICE_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
+static DEVICE_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
+static DEVICE_BOOL_ATTR(scrub_pages, 0644, xen_scrub_pages);
+
+static ssize_t show_target_kb(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
+}
+
+static ssize_t store_target_kb(struct device *dev,
+ struct device_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 DEVICE_ATTR(target_kb, S_IRUGO | S_IWUSR,
+ show_target_kb, store_target_kb);
+
+
+static ssize_t show_target(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "%llu\n",
+ (unsigned long long)balloon_stats.target_pages
+ << PAGE_SHIFT);
+}
+
+static ssize_t store_target(struct device *dev,
+ struct device_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 DEVICE_ATTR(target, S_IRUGO | S_IWUSR,
+ show_target, store_target);
+
+
+static struct attribute *balloon_attrs[] = {
+ &dev_attr_target_kb.attr,
+ &dev_attr_target.attr,
+ &dev_attr_schedule_delay.attr.attr,
+ &dev_attr_max_schedule_delay.attr.attr,
+ &dev_attr_retry_count.attr.attr,
+ &dev_attr_max_retry_count.attr.attr,
+ &dev_attr_scrub_pages.attr.attr,
+ NULL
+};
+
+static const struct attribute_group balloon_group = {
+ .attrs = balloon_attrs
+};
+
+static struct attribute *balloon_info_attrs[] = {
+ &dev_attr_current_kb.attr,
+ &dev_attr_low_kb.attr,
+ &dev_attr_high_kb.attr,
+ NULL
+};
+
+static const struct attribute_group balloon_info_group = {
+ .name = "info",
+ .attrs = balloon_info_attrs
+};
+
+static const struct attribute_group *balloon_groups[] = {
+ &balloon_group,
+ &balloon_info_group,
+ NULL
+};
+
+static struct bus_type balloon_subsys = {
+ .name = BALLOON_CLASS_NAME,
+ .dev_name = BALLOON_CLASS_NAME,
+};
+
+static int register_balloon(struct device *dev)
+{
+ int error;
+
+ error = subsys_system_register(&balloon_subsys, NULL);
+ if (error)
+ return error;
+
+ dev->id = 0;
+ dev->bus = &balloon_subsys;
+ dev->groups = balloon_groups;
+
+ error = device_register(dev);
+ if (error) {
+ bus_unregister(&balloon_subsys);
+ return error;
+ }
+
+ return 0;
+}