1 files changed, 712 insertions, 0 deletions

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
new file mode 100644
index 000000000000..ab25ba6cbbb9
--- /dev/null
+++ b/drivers/xen/balloon.c
@@ -0,0 +1,712 @@
+/******************************************************************************
+ * 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");