--- /dev/null
+/******************************************************************************
+ * balloon.c
+ *
+ * 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/sched.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/bootmem.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/mutex.h>
+#include <linux/highmem.h>
+#include <linux/list.h>
+#include <linux/sysdev.h>
+
+#include <asm/xen/hypervisor.h>
+#include <asm/page.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+#include <asm/uaccess.h>
+#include <asm/tlb.h>
+
+#include <xen/interface/memory.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 "memory"
+
+struct balloon_stats {
+ /* We aim for 'current allocation' == 'target allocation'. */
+ unsigned long current_pages;
+ unsigned long target_pages;
+ /* We may hit the hard limit in Xen. If we do then we remember it. */
+ unsigned long hard_limit;
+ /*
+ * Drivers may alter the memory reservation independently, but they
+ * must inform the balloon driver so we avoid hitting the hard limit.
+ */
+ unsigned long driver_pages;
+ /* Number of pages in high- and low-memory balloons. */
+ unsigned long balloon_low;
+ unsigned long balloon_high;
+};
+
+static DEFINE_MUTEX(balloon_mutex);
+
+static struct sys_device balloon_sysdev;
+
+static int register_balloon(struct sys_device *sysdev);
+
+/*
+ * Protects atomic reservation decrease/increase against concurrent increases.
+ * Also protects non-atomic updates of current_pages and driver_pages, and
+ * balloon lists.
+ */
+static DEFINE_SPINLOCK(balloon_lock);
+
+static struct balloon_stats balloon_stats;
+
+/* We increase/decrease in batches which fit in a page */
+static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
+
+/* VM /proc information for memory */
+extern unsigned long totalram_pages;
+
+#ifdef CONFIG_HIGHMEM
+extern unsigned long totalhigh_pages;
+#define inc_totalhigh_pages() (totalhigh_pages++)
+#define dec_totalhigh_pages() (totalhigh_pages--)
+#else
+#define inc_totalhigh_pages() do {} while(0)
+#define dec_totalhigh_pages() do {} while(0)
+#endif
+
+/* List of ballooned pages, threaded through the mem_map array. */
+static LIST_HEAD(ballooned_pages);
+
+/* Main work function, always executed in process context. */
+static void balloon_process(struct work_struct *work);
+static DECLARE_WORK(balloon_worker, balloon_process);
+static struct timer_list balloon_timer;
+
+/* When ballooning out (allocating memory to return to Xen) we don't really
+ want the kernel to try too hard since that can trigger the oom killer. */
+#define GFP_BALLOON \
+ (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
+
+static void scrub_page(struct page *page)
+{
+#ifdef CONFIG_XEN_SCRUB_PAGES
+ if (PageHighMem(page)) {
+ void *v = kmap(page);
+ clear_page(v);
+ kunmap(v);
+ } else {
+ void *v = page_address(page);
+ clear_page(v);
+ }
+#endif
+}
+
+/* balloon_append: add the given page to the balloon. */
+static void balloon_append(struct page *page)
+{
+ /* Lowmem is re-populated first, so highmem pages go at list tail. */
+ if (PageHighMem(page)) {
+ list_add_tail(&page->lru, &ballooned_pages);
+ balloon_stats.balloon_high++;
+ dec_totalhigh_pages();
+ } else {
+ list_add(&page->lru, &ballooned_pages);
+ balloon_stats.balloon_low++;
+ }
+}
+
+/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
+static struct page *balloon_retrieve(void)
+{
+ struct page *page;
+
+ if (list_empty(&ballooned_pages))
+ return NULL;
+
+ page = list_entry(ballooned_pages.next, struct page, lru);
+ list_del(&page->lru);
+
+ if (PageHighMem(page)) {
+ balloon_stats.balloon_high--;
+ inc_totalhigh_pages();
+ }
+ else
+ balloon_stats.balloon_low--;
+
+ return page;
+}
+
+static struct page *balloon_first_page(void)
+{
+ if (list_empty(&ballooned_pages))
+ return NULL;
+ return list_entry(ballooned_pages.next, struct page, lru);
+}
+
+static struct page *balloon_next_page(struct page *page)
+{
+ struct list_head *next = page->lru.next;
+ if (next == &ballooned_pages)
+ return NULL;
+ return list_entry(next, struct page, lru);
+}
+
+static void balloon_alarm(unsigned long unused)
+{
+ schedule_work(&balloon_worker);
+}
+
+static unsigned long current_target(void)
+{
+ unsigned long target = min(balloon_stats.target_pages, balloon_stats.hard_limit);
+
+ target = min(target,
+ balloon_stats.current_pages +
+ balloon_stats.balloon_low +
+ balloon_stats.balloon_high);
+
+ return target;
+}
+
+static int increase_reservation(unsigned long nr_pages)
+{
+ unsigned long pfn, i, flags;
+ struct page *page;
+ long rc;
+ struct xen_memory_reservation reservation = {
+ .address_bits = 0,
+ .extent_order = 0,
+ .domid = DOMID_SELF
+ };
+
+ if (nr_pages > ARRAY_SIZE(frame_list))
+ nr_pages = ARRAY_SIZE(frame_list);
+
+ spin_lock_irqsave(&balloon_lock, flags);
+
+ page = balloon_first_page();
+ for (i = 0; i < nr_pages; i++) {
+ BUG_ON(page == NULL);
+ frame_list[i] = page_to_pfn(page);;
+ page = balloon_next_page(page);
+ }
+
+ reservation.extent_start = (unsigned long)frame_list;
+ reservation.nr_extents = nr_pages;
+ rc = HYPERVISOR_memory_op(
+ XENMEM_populate_physmap, &reservation);
+ if (rc < nr_pages) {
+ if (rc > 0) {
+ int ret;
+
+ /* We hit the Xen hard limit: reprobe. */
+ reservation.nr_extents = rc;
+ ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
+ &reservation);
+ BUG_ON(ret != rc);
+ }
+ if (rc >= 0)
+ balloon_stats.hard_limit = (balloon_stats.current_pages + rc -
+ balloon_stats.driver_pages);
+ goto out;
+ }
+
+ for (i = 0; i < nr_pages; i++) {
+ page = balloon_retrieve();
+ BUG_ON(page == NULL);
+
+ pfn = page_to_pfn(page);
+ BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
+ phys_to_machine_mapping_valid(pfn));
+
+ set_phys_to_machine(pfn, frame_list[i]);
+
+ /* Link back into the page tables if not highmem. */
+ if (pfn < max_low_pfn) {
+ int ret;
+ ret = HYPERVISOR_update_va_mapping(
+ (unsigned long)__va(pfn << PAGE_SHIFT),
+ mfn_pte(frame_list[i], PAGE_KERNEL),
+ 0);
+ BUG_ON(ret);
+ }
+
+ /* Relinquish the page back to the allocator. */
+ ClearPageReserved(page);
+ init_page_count(page);
+ __free_page(page);
+ }
+
+ balloon_stats.current_pages += nr_pages;
+ totalram_pages = balloon_stats.current_pages;
+
+ out:
+ spin_unlock_irqrestore(&balloon_lock, flags);
+
+ return 0;
+}
+
+static int decrease_reservation(unsigned long nr_pages)
+{
+ unsigned long pfn, i, flags;
+ struct page *page;
+ int need_sleep = 0;
+ int ret;
+ struct xen_memory_reservation reservation = {
+ .address_bits = 0,
+ .extent_order = 0,
+ .domid = DOMID_SELF
+ };
+
+ if (nr_pages > ARRAY_SIZE(frame_list))
+ nr_pages = ARRAY_SIZE(frame_list);
+
+ for (i = 0; i < nr_pages; i++) {
+ if ((page = alloc_page(GFP_BALLOON)) == NULL) {
+ nr_pages = i;
+ need_sleep = 1;
+ break;
+ }
+
+ pfn = page_to_pfn(page);
+ frame_list[i] = pfn_to_mfn(pfn);
+
+ scrub_page(page);
+ }
+
+ /* Ensure that ballooned highmem pages don't have kmaps. */
+ kmap_flush_unused();
+ flush_tlb_all();
+
+ spin_lock_irqsave(&balloon_lock, flags);
+
+ /* No more mappings: invalidate P2M and add to balloon. */
+ for (i = 0; i < nr_pages; i++) {
+ pfn = mfn_to_pfn(frame_list[i]);
+ set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+ balloon_append(pfn_to_page(pfn));
+ }
+
+ reservation.extent_start = (unsigned long)frame_list;
+ reservation.nr_extents = nr_pages;
+ ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+ BUG_ON(ret != nr_pages);
+
+ balloon_stats.current_pages -= nr_pages;
+ totalram_pages = balloon_stats.current_pages;
+
+ spin_unlock_irqrestore(&balloon_lock, flags);
+
+ return need_sleep;
+}
+
+/*
+ * We avoid multiple worker processes conflicting via the balloon mutex.
+ * We may of course race updates of the target counts (which are protected
+ * by the balloon lock), or with changes to the Xen hard limit, but we will
+ * recover from these in time.
+ */
+static void balloon_process(struct work_struct *work)
+{
+ int need_sleep = 0;
+ long credit;
+
+ mutex_lock(&balloon_mutex);
+
+ do {
+ credit = current_target() - balloon_stats.current_pages;
+ if (credit > 0)
+ need_sleep = (increase_reservation(credit) != 0);
+ if (credit < 0)
+ need_sleep = (decrease_reservation(-credit) != 0);
+
+#ifndef CONFIG_PREEMPT
+ if (need_resched())
+ schedule();
+#endif
+ } while ((credit != 0) && !need_sleep);
+
+ /* Schedule more work if there is some still to be done. */
+ if (current_target() != balloon_stats.current_pages)
+ mod_timer(&balloon_timer, jiffies + HZ);
+
+ mutex_unlock(&balloon_mutex);
+}
+
+/* Resets the Xen limit, sets new target, and kicks off processing. */
+void balloon_set_new_target(unsigned long target)
+{
+ /* No need for lock. Not read-modify-write updates. */
+ balloon_stats.hard_limit = ~0UL;
+ balloon_stats.target_pages = target;
+ schedule_work(&balloon_worker);
+}
+
+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)
+{
+ unsigned long pfn;
+ struct page *page;
+
+ if (!is_running_on_xen())
+ return -ENODEV;
+
+ pr_info("xen_balloon: Initialising balloon driver.\n");
+
+ balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
+ totalram_pages = balloon_stats.current_pages;
+ balloon_stats.target_pages = balloon_stats.current_pages;
+ balloon_stats.balloon_low = 0;
+ balloon_stats.balloon_high = 0;
+ balloon_stats.driver_pages = 0UL;
+ balloon_stats.hard_limit = ~0UL;
+
+ init_timer(&balloon_timer);
+ balloon_timer.data = 0;
+ balloon_timer.function = balloon_alarm;
+
+ register_balloon(&balloon_sysdev);
+
+ /* Initialise the balloon with excess memory space. */
+ for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
+ page = pfn_to_page(pfn);
+ if (!PageReserved(page))
+ balloon_append(page);
+ }
+
+ 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);
+
+static void balloon_update_driver_allowance(long delta)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&balloon_lock, flags);
+ balloon_stats.driver_pages += delta;
+ spin_unlock_irqrestore(&balloon_lock, flags);
+}
+
+static int dealloc_pte_fn(
+ pte_t *pte, struct page *pmd_page, unsigned long addr, void *data)
+{
+ unsigned long mfn = pte_mfn(*pte);
+ int ret;
+ struct xen_memory_reservation reservation = {
+ .nr_extents = 1,
+ .extent_order = 0,
+ .domid = DOMID_SELF
+ };
+ reservation.extent_start = (unsigned long)&mfn;
+ set_pte_at(&init_mm, addr, pte, __pte_ma(0ull));
+ set_phys_to_machine(__pa(addr) >> PAGE_SHIFT, INVALID_P2M_ENTRY);
+ ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+ BUG_ON(ret != 1);
+ return 0;
+}
+
+static struct page **alloc_empty_pages_and_pagevec(int nr_pages)
+{
+ unsigned long vaddr, flags;
+ struct page *page, **pagevec;
+ int i, ret;
+
+ pagevec = kmalloc(sizeof(page) * nr_pages, GFP_KERNEL);
+ if (pagevec == NULL)
+ return NULL;
+
+ for (i = 0; i < nr_pages; i++) {
+ page = pagevec[i] = alloc_page(GFP_KERNEL);
+ if (page == NULL)
+ goto err;
+
+ vaddr = (unsigned long)page_address(page);
+
+ scrub_page(page);
+
+ spin_lock_irqsave(&balloon_lock, flags);
+
+ if (xen_feature(XENFEAT_auto_translated_physmap)) {
+ unsigned long gmfn = page_to_pfn(page);
+ struct xen_memory_reservation reservation = {
+ .nr_extents = 1,
+ .extent_order = 0,
+ .domid = DOMID_SELF
+ };
+ reservation.extent_start = (unsigned long)&gmfn;
+ ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
+ &reservation);
+ if (ret == 1)
+ ret = 0; /* success */
+ } else {
+ ret = apply_to_page_range(&init_mm, vaddr, PAGE_SIZE,
+ dealloc_pte_fn, NULL);
+ }
+
+ if (ret != 0) {
+ spin_unlock_irqrestore(&balloon_lock, flags);
+ __free_page(page);
+ goto err;
+ }
+
+ totalram_pages = --balloon_stats.current_pages;
+
+ spin_unlock_irqrestore(&balloon_lock, flags);
+ }
+
+ out:
+ schedule_work(&balloon_worker);
+ flush_tlb_all();
+ return pagevec;
+
+ err:
+ spin_lock_irqsave(&balloon_lock, flags);
+ while (--i >= 0)
+ balloon_append(pagevec[i]);
+ spin_unlock_irqrestore(&balloon_lock, flags);
+ kfree(pagevec);
+ pagevec = NULL;
+ goto out;
+}
+
+static void free_empty_pages_and_pagevec(struct page **pagevec, int nr_pages)
+{
+ unsigned long flags;
+ int i;
+
+ if (pagevec == NULL)
+ return;
+
+ spin_lock_irqsave(&balloon_lock, flags);
+ for (i = 0; i < nr_pages; i++) {
+ BUG_ON(page_count(pagevec[i]) != 1);
+ balloon_append(pagevec[i]);
+ }
+ spin_unlock_irqrestore(&balloon_lock, flags);
+
+ kfree(pagevec);
+
+ schedule_work(&balloon_worker);
+}
+
+static void balloon_release_driver_page(struct page *page)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&balloon_lock, flags);
+ balloon_append(page);
+ balloon_stats.driver_pages--;
+ spin_unlock_irqrestore(&balloon_lock, flags);
+
+ schedule_work(&balloon_worker);
+}
+
+
+#define BALLOON_SHOW(name, format, args...) \
+ static ssize_t show_##name(struct sys_device *dev, \
+ 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));
+BALLOON_SHOW(hard_limit_kb,
+ (balloon_stats.hard_limit!=~0UL) ? "%lu\n" : "???\n",
+ (balloon_stats.hard_limit!=~0UL) ? PAGES2KB(balloon_stats.hard_limit) : 0);
+BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
+
+static ssize_t show_target_kb(struct sys_device *dev, char *buf)
+{
+ return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
+}
+
+static ssize_t store_target_kb(struct sys_device *dev,
+ const char *buf,
+ size_t count)
+{
+ char memstring[64], *endchar;
+ unsigned long long target_bytes;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ if (count <= 1)
+ return -EBADMSG; /* runt */
+ if (count > sizeof(memstring))
+ return -EFBIG; /* too long */
+ strcpy(memstring, buf);
+
+ target_bytes = memparse(memstring, &endchar);
+ 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 struct sysdev_attribute *balloon_attrs[] = {
+ &attr_target_kb,
+};
+
+static struct attribute *balloon_info_attrs[] = {
+ &attr_current_kb.attr,
+ &attr_low_kb.attr,
+ &attr_high_kb.attr,
+ &attr_hard_limit_kb.attr,
+ &attr_driver_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;
+}
+
+static void unregister_balloon(struct sys_device *sysdev)
+{
+ int i;
+
+ sysfs_remove_group(&sysdev->kobj, &balloon_info_group);
+ for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++)
+ sysdev_remove_file(sysdev, balloon_attrs[i]);
+ sysdev_unregister(sysdev);
+ sysdev_class_unregister(&balloon_sysdev_class);
+}
+
+static void balloon_sysfs_exit(void)
+{
+ unregister_balloon(&balloon_sysdev);
+}
+
+MODULE_LICENSE("GPL");
projects / nvme.git / commitdiff