--- /dev/null
+/******************************************************************************
+ * 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
+ * Copyright (c) 2010 Daniel Kiper
+ *
+ * Memory hotplug support was written by Daniel Kiper. Work on
+ * it was sponsored by Google under Google Summer of Code 2010
+ * program. Jeremy Fitzhardinge from Citrix was the mentor for
+ * this project.
+ *
+ * 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) "xen:" KBUILD_MODNAME ": " fmt
+
+#include <linux/cpu.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/bootmem.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/gfp.h>
+#include <linux/notifier.h>
+#include <linux/memory.h>
+#include <linux/memory_hotplug.h>
+#include <linux/percpu-defs.h>
+
+#include <asm/page.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+#include <asm/tlb.h>
+
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+
+#include <xen/xen.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/memory.h>
+#include <xen/balloon.h>
+#include <xen/features.h>
+#include <xen/page.h>
+
+/*
+ * balloon_process() state:
+ *
+ * BP_DONE: done or nothing to do,
+ * BP_EAGAIN: error, go to sleep,
+ * BP_ECANCELED: error, balloon operation canceled.
+ */
+
+enum bp_state {
+ BP_DONE,
+ BP_EAGAIN,
+ BP_ECANCELED
+};
+
+
+static DEFINE_MUTEX(balloon_mutex);
+
+struct balloon_stats balloon_stats;
+EXPORT_SYMBOL_GPL(balloon_stats);
+
+/* We increase/decrease in batches which fit in a page */
+static xen_pfn_t frame_list[PAGE_SIZE / sizeof(unsigned long)];
+
+
+/* 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_DELAYED_WORK(balloon_worker, balloon_process);
+
+/* 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
+ clear_highpage(page);
+#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++;
+ } else {
+ list_add(&page->lru, &ballooned_pages);
+ balloon_stats.balloon_low++;
+ }
+}
+
+static void balloon_append(struct page *page)
+{
+ __balloon_append(page);
+ adjust_managed_page_count(page, -1);
+}
+
+/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
+static struct page *balloon_retrieve(bool prefer_highmem)
+{
+ struct page *page;
+
+ if (list_empty(&ballooned_pages))
+ return NULL;
+
+ if (prefer_highmem)
+ page = list_entry(ballooned_pages.prev, struct page, lru);
+ else
+ page = list_entry(ballooned_pages.next, struct page, lru);
+ list_del(&page->lru);
+
+ if (PageHighMem(page))
+ balloon_stats.balloon_high--;
+ else
+ balloon_stats.balloon_low--;
+
+ adjust_managed_page_count(page, 1);
+
+ return page;
+}
+
+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 enum bp_state update_schedule(enum bp_state state)
+{
+ if (state == BP_ECANCELED)
+ return BP_ECANCELED;
+
+ if (state == BP_DONE) {
+ balloon_stats.schedule_delay = 1;
+ balloon_stats.retry_count = 1;
+ return BP_DONE;
+ }
+
+ ++balloon_stats.retry_count;
+
+ if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
+ balloon_stats.retry_count > balloon_stats.max_retry_count) {
+ balloon_stats.schedule_delay = 1;
+ balloon_stats.retry_count = 1;
+ return BP_ECANCELED;
+ }
+
+ balloon_stats.schedule_delay <<= 1;
+
+ if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
+ balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
+
+ return BP_EAGAIN;
+}
+
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+static long current_credit(void)
+{
+ return balloon_stats.target_pages - balloon_stats.current_pages -
+ balloon_stats.hotplug_pages;
+}
+
+static bool balloon_is_inflated(void)
+{
+ if (balloon_stats.balloon_low || balloon_stats.balloon_high ||
+ balloon_stats.balloon_hotplug)
+ return true;
+ else
+ return false;
+}
+
+/*
+ * reserve_additional_memory() adds memory region of size >= credit above
+ * max_pfn. New region is section aligned and size is modified to be multiple
+ * of section size. Those features allow optimal use of address space and
+ * establish proper alignment when this function is called first time after
+ * boot (last section not fully populated at boot time contains unused memory
+ * pages with PG_reserved bit not set; online_pages_range() does not allow page
+ * onlining in whole range if first onlined page does not have PG_reserved
+ * bit set). Real size of added memory is established at page onlining stage.
+ */
+
+static enum bp_state reserve_additional_memory(long credit)
+{
+ int nid, rc;
+ u64 hotplug_start_paddr;
+ unsigned long balloon_hotplug = credit;
+
+ hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn));
+ balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
+ nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+ /*
+ * add_memory() will build page tables for the new memory so
+ * the p2m must contain invalid entries so the correct
+ * non-present PTEs will be written.
+ *
+ * If a failure occurs, the original (identity) p2m entries
+ * are not restored since this region is now known not to
+ * conflict with any devices.
+ */
+ if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+ unsigned long pfn, i;
+
+ pfn = PFN_DOWN(hotplug_start_paddr);
+ for (i = 0; i < balloon_hotplug; i++) {
+ if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
+ pr_warn("set_phys_to_machine() failed, no memory added\n");
+ return BP_ECANCELED;
+ }
+ }
+ }
+#endif
+
+ rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);
+
+ if (rc) {
+ pr_warn("Cannot add additional memory (%i)\n", rc);
+ return BP_ECANCELED;
+ }
+
+ balloon_hotplug -= credit;
+
+ balloon_stats.hotplug_pages += credit;
+ balloon_stats.balloon_hotplug = balloon_hotplug;
+
+ return BP_DONE;
+}
+
+static void xen_online_page(struct page *page)
+{
+ __online_page_set_limits(page);
+
+ mutex_lock(&balloon_mutex);
+
+ __balloon_append(page);
+
+ if (balloon_stats.hotplug_pages)
+ --balloon_stats.hotplug_pages;
+ else
+ --balloon_stats.balloon_hotplug;
+
+ mutex_unlock(&balloon_mutex);
+}
+
+static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
+{
+ if (val == MEM_ONLINE)
+ schedule_delayed_work(&balloon_worker, 0);
+
+ return NOTIFY_OK;
+}
+
+static struct notifier_block xen_memory_nb = {
+ .notifier_call = xen_memory_notifier,
+ .priority = 0
+};
+#else
+static long current_credit(void)
+{
+ unsigned long target = balloon_stats.target_pages;
+
+ target = min(target,
+ balloon_stats.current_pages +
+ balloon_stats.balloon_low +
+ balloon_stats.balloon_high);
+
+ return target - balloon_stats.current_pages;
+}
+
+static bool balloon_is_inflated(void)
+{
+ if (balloon_stats.balloon_low || balloon_stats.balloon_high)
+ return true;
+ else
+ return false;
+}
+
+static enum bp_state reserve_additional_memory(long credit)
+{
+ balloon_stats.target_pages = balloon_stats.current_pages;
+ return BP_DONE;
+}
+#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
+
+static enum bp_state increase_reservation(unsigned long nr_pages)
+{
+ int rc;
+ unsigned long pfn, i;
+ struct page *page;
+ struct xen_memory_reservation reservation = {
+ .address_bits = 0,
+ .extent_order = 0,
+ .domid = DOMID_SELF
+ };
+
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+ if (!balloon_stats.balloon_low && !balloon_stats.balloon_high) {
+ nr_pages = min(nr_pages, balloon_stats.balloon_hotplug);
+ balloon_stats.hotplug_pages += nr_pages;
+ balloon_stats.balloon_hotplug -= nr_pages;
+ return BP_DONE;
+ }
+#endif
+
+ if (nr_pages > ARRAY_SIZE(frame_list))
+ nr_pages = ARRAY_SIZE(frame_list);
+
+ page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
+ for (i = 0; i < nr_pages; i++) {
+ if (!page) {
+ nr_pages = i;
+ break;
+ }
+ frame_list[i] = page_to_pfn(page);
+ page = balloon_next_page(page);
+ }
+
+ set_xen_guest_handle(reservation.extent_start, frame_list);
+ reservation.nr_extents = nr_pages;
+ rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
+ if (rc <= 0)
+ return BP_EAGAIN;
+
+ for (i = 0; i < rc; i++) {
+ page = balloon_retrieve(false);
+ BUG_ON(page == NULL);
+
+ pfn = page_to_pfn(page);
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+ if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+ set_phys_to_machine(pfn, frame_list[i]);
+
+ /* Link back into the page tables if not highmem. */
+ if (!PageHighMem(page)) {
+ int ret;
+ ret = HYPERVISOR_update_va_mapping(
+ (unsigned long)__va(pfn << PAGE_SHIFT),
+ mfn_pte(frame_list[i], PAGE_KERNEL),
+ 0);
+ BUG_ON(ret);
+ }
+ }
+#endif
+
+ /* Relinquish the page back to the allocator. */
+ __free_reserved_page(page);
+ }
+
+ balloon_stats.current_pages += rc;
+
+ return BP_DONE;
+}
+
+static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
+{
+ enum bp_state state = BP_DONE;
+ unsigned long pfn, i;
+ struct page *page;
+ int ret;
+ struct xen_memory_reservation reservation = {
+ .address_bits = 0,
+ .extent_order = 0,
+ .domid = DOMID_SELF
+ };
+
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+ if (balloon_stats.hotplug_pages) {
+ nr_pages = min(nr_pages, balloon_stats.hotplug_pages);
+ balloon_stats.hotplug_pages -= nr_pages;
+ balloon_stats.balloon_hotplug += nr_pages;
+ return BP_DONE;
+ }
+#endif
+
+ if (nr_pages > ARRAY_SIZE(frame_list))
+ nr_pages = ARRAY_SIZE(frame_list);
+
+ for (i = 0; i < nr_pages; i++) {
+ page = alloc_page(gfp);
+ if (page == NULL) {
+ nr_pages = i;
+ state = BP_EAGAIN;
+ break;
+ }
+ scrub_page(page);
+
+ frame_list[i] = page_to_pfn(page);
+ }
+
+ /*
+ * Ensure that ballooned highmem pages don't have kmaps.
+ *
+ * Do this before changing the p2m as kmap_flush_unused()
+ * reads PTEs to obtain pages (and hence needs the original
+ * p2m entry).
+ */
+ kmap_flush_unused();
+
+ /* Update direct mapping, invalidate P2M, and add to balloon. */
+ for (i = 0; i < nr_pages; i++) {
+ pfn = frame_list[i];
+ frame_list[i] = pfn_to_mfn(pfn);
+ page = pfn_to_page(pfn);
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+ if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+ if (!PageHighMem(page)) {
+ ret = HYPERVISOR_update_va_mapping(
+ (unsigned long)__va(pfn << PAGE_SHIFT),
+ __pte_ma(0), 0);
+ BUG_ON(ret);
+ }
+ __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+ }
+#endif
+
+ balloon_append(page);
+ }
+
+ flush_tlb_all();
+
+ set_xen_guest_handle(reservation.extent_start, 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;
+
+ return state;
+}
+
+/*
+ * 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)
+{
+ enum bp_state state = BP_DONE;
+ long credit;
+
+ mutex_lock(&balloon_mutex);
+
+ do {
+ credit = current_credit();
+
+ if (credit > 0) {
+ if (balloon_is_inflated())
+ state = increase_reservation(credit);
+ else
+ state = reserve_additional_memory(credit);
+ }
+
+ if (credit < 0)
+ state = decrease_reservation(-credit, GFP_BALLOON);
+
+ state = update_schedule(state);
+
+#ifndef CONFIG_PREEMPT
+ if (need_resched())
+ schedule();
+#endif
+ } while (credit && state == BP_DONE);
+
+ /* Schedule more work if there is some still to be done. */
+ if (state == BP_EAGAIN)
+ schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * 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.target_pages = target;
+ schedule_delayed_work(&balloon_worker, 0);
+}
+EXPORT_SYMBOL_GPL(balloon_set_new_target);
+
+/**
+ * alloc_xenballooned_pages - get pages that have been ballooned out
+ * @nr_pages: Number of pages to get
+ * @pages: pages returned
+ * @highmem: allow highmem pages
+ * @return 0 on success, error otherwise
+ */
+int alloc_xenballooned_pages(int nr_pages, struct page **pages, bool highmem)
+{
+ int pgno = 0;
+ struct page *page;
+ mutex_lock(&balloon_mutex);
+ while (pgno < nr_pages) {
+ page = balloon_retrieve(highmem);
+ if (page && (highmem || !PageHighMem(page))) {
+ pages[pgno++] = page;
+ } else {
+ enum bp_state st;
+ if (page)
+ balloon_append(page);
+ st = decrease_reservation(nr_pages - pgno,
+ highmem ? GFP_HIGHUSER : GFP_USER);
+ if (st != BP_DONE)
+ goto out_undo;
+ }
+ }
+ mutex_unlock(&balloon_mutex);
+ return 0;
+ out_undo:
+ while (pgno)
+ balloon_append(pages[--pgno]);
+ /* Free the memory back to the kernel soon */
+ schedule_delayed_work(&balloon_worker, 0);
+ mutex_unlock(&balloon_mutex);
+ return -ENOMEM;
+}
+EXPORT_SYMBOL(alloc_xenballooned_pages);
+
+/**
+ * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
+ * @nr_pages: Number of pages
+ * @pages: pages to return
+ */
+void free_xenballooned_pages(int nr_pages, struct page **pages)
+{
+ int i;
+
+ mutex_lock(&balloon_mutex);
+
+ for (i = 0; i < nr_pages; i++) {
+ if (pages[i])
+ balloon_append(pages[i]);
+ }
+
+ /* The balloon may be too large now. Shrink it if needed. */
+ if (current_credit())
+ schedule_delayed_work(&balloon_worker, 0);
+
+ mutex_unlock(&balloon_mutex);
+}
+EXPORT_SYMBOL(free_xenballooned_pages);
+
+static void __init balloon_add_region(unsigned long start_pfn,
+ unsigned long pages)
+{
+ unsigned long pfn, extra_pfn_end;
+ struct page *page;
+
+ /*
+ * If the amount of usable memory has been limited (e.g., with
+ * the 'mem' command line parameter), don't add pages beyond
+ * this limit.
+ */
+ extra_pfn_end = min(max_pfn, start_pfn + pages);
+
+ for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
+ page = pfn_to_page(pfn);
+ /* totalram_pages and totalhigh_pages do not
+ include the boot-time balloon extension, so
+ don't subtract from it. */
+ __balloon_append(page);
+ }
+}
+
+static int __init balloon_init(void)
+{
+ int i;
+
+ if (!xen_domain())
+ return -ENODEV;
+
+ pr_info("Initialising balloon driver\n");
+
+ balloon_stats.current_pages = xen_pv_domain()
+ ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
+ : get_num_physpages();
+ balloon_stats.target_pages = balloon_stats.current_pages;
+ balloon_stats.balloon_low = 0;
+ balloon_stats.balloon_high = 0;
+
+ balloon_stats.schedule_delay = 1;
+ balloon_stats.max_schedule_delay = 32;
+ balloon_stats.retry_count = 1;
+ balloon_stats.max_retry_count = RETRY_UNLIMITED;
+
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+ balloon_stats.hotplug_pages = 0;
+ balloon_stats.balloon_hotplug = 0;
+
+ set_online_page_callback(&xen_online_page);
+ register_memory_notifier(&xen_memory_nb);
+#endif
+
+ /*
+ * Initialize the balloon with pages from the extra memory
+ * regions (see arch/x86/xen/setup.c).
+ */
+ for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
+ if (xen_extra_mem[i].size)
+ balloon_add_region(PFN_UP(xen_extra_mem[i].start),
+ PFN_DOWN(xen_extra_mem[i].size));
+
+ return 0;
+}
+
+subsys_initcall(balloon_init);
+
+MODULE_LICENSE("GPL");
Code Review / kvmfornfv.git / blobdiff