1 files changed, 446 insertions, 0 deletions
diff --git a/sys/dev/xen/balloon/balloon.c b/sys/dev/xen/balloon/balloon.c
new file mode 100644
index 0000000..fa49196
--- /dev/null
+++ b/sys/dev/xen/balloon/balloon.c
@@ -0,0 +1,446 @@
+/******************************************************************************
+ * 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 file may be 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 <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
+
+#include <machine/hypervisor-ifs.h>
+#include <machine/xen-os.h>
+#include <machine/xenbus.h>
+
+/*
+ * Protects atomic reservation decrease/increase against concurrent increases.
+ * Also protects non-atomic updates of current_pages and driver_pages, and
+ * balloon lists.
+ */
+struct mtx balloon_lock;
+#ifdef notyet
+
+/* We aim for 'current allocation' == 'target allocation'. */
+static unsigned long current_pages;
+static unsigned long target_pages;
+
+/* VM /proc information for memory */
+extern unsigned long totalram_pages;
+
+/* We may hit the hard limit in Xen. If we do then we remember it. */
+static unsigned long hard_limit;
+
+/*
+ * Drivers may alter the memory reservation independently, but they must
+ * inform the balloon driver so that we can avoid hitting the hard limit.
+ */
+static unsigned long driver_pages;
+
+struct balloon_entry {
+	vm_page_t page;
+	STAILQ_ENTRY(balloon_entry) list;
+};
+
+/* List of ballooned pages, threaded through the mem_map array. */
+static STAILQ_HEAD(,balloon_entry) ballooned_pages;
+
+static unsigned long balloon_low, balloon_high;
+
+
+/* Main work function, always executed in process context. */
+static void balloon_process(void *unused);
+
+#define IPRINTK(fmt, args...) \
+	printk(KERN_INFO "xen_mem: " fmt, ##args)
+#define WPRINTK(fmt, args...) \
+	printk(KERN_WARNING "xen_mem: " fmt, ##args)
+
+/* balloon_append: add the given page to the balloon. */
+static void 
+balloon_append(vm_page_t page)
+{
+	struct balloon_entry *entry;
+
+	entry = malloc(sizeof(struct balloon_entry), M_WAITOK);
+
+	STAILQ_INSERT_HEAD(&ballooned_pages, entry, list);
+	balloon_low++;
+}
+
+/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
+static vm_page_t
+balloon_retrieve(void)
+{
+	vm_page_t page;
+	struct balloon_entry *entry;
+
+	if (STAILQ_EMPTY(&ballooned_pages))
+		return NULL;
+
+	entry = STAILQ_FIRST(&ballooned_pages);
+	STAILQ_REMOVE_HEAD(&ballooned_pages, list);
+
+	page = entry->page;
+	free(entry, M_DEVBUF);
+	
+	balloon_low--;
+
+	return page;
+}
+
+static void 
+balloon_alarm(unsigned long unused)
+{
+	wakeup(balloon_process);
+}
+
+static unsigned long 
+current_target(void)
+{
+	unsigned long target = min(target_pages, hard_limit);
+	if (target > (current_pages + balloon_low + balloon_high))
+		target = current_pages + balloon_low + balloon_high;
+	return target;
+}
+
+static int 
+increase_reservation(unsigned long nr_pages)
+{
+	unsigned long *mfn_list, 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 > (PAGE_SIZE / sizeof(unsigned long)))
+		nr_pages = PAGE_SIZE / sizeof(unsigned long);
+
+	mfn_list = (unsigned long *)malloc(PAGE_SIZE, M_DEVBUF, M_NOWAIT);
+	if (mfn_list == NULL)
+		return ENOMEM;
+
+
+	reservation.extent_start = mfn_list;
+	reservation.nr_extents   = nr_pages;
+	rc = HYPERVISOR_memory_op(
+		XENMEM_increase_reservation, &reservation);
+	if (rc < nr_pages) {
+		int ret;
+		/* We hit the Xen hard limit: reprobe. */
+		reservation.extent_start = mfn_list;
+		reservation.nr_extents   = rc;
+		ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
+				&reservation);
+		PANIC_IF(ret != rc);
+		hard_limit = current_pages + rc - driver_pages;
+		goto out;
+	}
+
+	for (i = 0; i < nr_pages; i++) {
+		page = balloon_retrieve();
+		PANIC_IF(page == NULL);
+
+		pfn = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT);
+		PANIC_IF(phys_to_machine_mapping_valid(pfn));
+
+		/* Update P->M and M->P tables. */
+		PFNTOMFN(pfn) = mfn_list[i];
+		xen_machphys_update(mfn_list[i], pfn);
+            
+		/* Relinquish the page back to the allocator. */
+		ClearPageReserved(page);
+		set_page_count(page, 1);
+		vm_page_free(page);
+	}
+
+	current_pages += nr_pages;
+	totalram_pages = current_pages;
+
+ out:
+	balloon_unlock(flags);
+
+	free((mfn_list);
+
+	return 0;
+}
+
+static int 
+decrease_reservation(unsigned long nr_pages)
+{
+	unsigned long *mfn_list, pfn, i, flags;
+	struct page   *page;
+	void          *v;
+	int            need_sleep = 0;
+	int ret;
+	struct xen_memory_reservation reservation = {
+		.address_bits = 0,
+		.extent_order = 0,
+		.domid        = DOMID_SELF
+	};
+
+	if (nr_pages > (PAGE_SIZE / sizeof(unsigned long)))
+		nr_pages = PAGE_SIZE / sizeof(unsigned long);
+
+	mfn_list = (unsigned long *)malloc(PAGE_SIZE, M_DEVBUF, M_NOWAIT);
+	if (mfn_list == NULL)
+		return ENOMEM;
+
+	for (i = 0; i < nr_pages; i++) {
+		int color = 0;
+		if ((page = vm_page_alloc(NULL, color++, 
+					  VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ | 
+					  VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL) {
+			nr_pages = i;
+			need_sleep = 1;
+			break;
+		}
+		pfn = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT);
+		mfn_list[i] = PFNTOMFN(pfn);
+	}
+
+	balloon_lock(flags);
+
+	/* No more mappings: invalidate P2M and add to balloon. */
+	for (i = 0; i < nr_pages; i++) {
+		pfn = MFNTOPFN(mfn_list[i]);
+		PFNTOMFN(pfn) = INVALID_P2M_ENTRY;
+		balloon_append(PHYS_TO_VM_PAGE(pfn << PAGE_SHIFT));
+	}
+
+	reservation.extent_start = mfn_list;
+	reservation.nr_extents   = nr_pages;
+	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+	PANIC_IF(ret != nr_pages);
+
+	current_pages -= nr_pages;
+	totalram_pages = current_pages;
+
+	balloon_unlock(flags);
+
+	free(mfn_list, M_DEVBUF);
+
+	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(void *unused)
+{
+	int need_sleep = 0;
+	long credit;
+	
+	for (;;) {
+		do {
+			credit = current_target() - 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() != current_pages)
+			timeout(balloon_alarm, NULL, ticks + HZ);
+
+			msleep(balloon_process, balloon_lock, 0, "balloon", -1);
+	}
+
+}
+
+/* Resets the Xen limit, sets new target, and kicks off processing. */
+static void 
+set_new_target(unsigned long target)
+{
+	/* No need for lock. Not read-modify-write updates. */
+	hard_limit   = ~0UL;
+	target_pages = target;
+	wakeup(balloon_process);
+}
+
+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(NULL, "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.
+	*/
+	set_new_target(new_target >> (PAGE_SHIFT - 10));
+    
+}
+
+static void 
+balloon_init_watcher(void *)
+{
+	int err;
+
+	err = register_xenbus_watch(&target_watch);
+	if (err)
+		printf("Failed to set balloon watcher\n");
+
+}
+
+static void 
+balloon_init(void *)
+{
+	unsigned long pfn;
+	struct page *page;
+
+	IPRINTK("Initialising balloon driver.\n");
+
+	if (xen_init() < 0)
+		return -1;
+
+	current_pages = min(xen_start_info->nr_pages, max_pfn);
+	target_pages  = current_pages;
+	balloon_low   = 0;
+	balloon_high  = 0;
+	driver_pages  = 0UL;
+	hard_limit    = ~0UL;
+
+	init_timer(&balloon_timer);
+	balloon_timer.data = 0;
+	balloon_timer.function = balloon_alarm;
+    
+	/* Initialise the balloon with excess memory space. */
+	for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
+		page = PHYS_TO_VM_PAGE(pfn << PAGE_SHIFT);
+		balloon_append(page);
+	}
+
+	target_watch.callback = watch_target;
+    
+	return 0;
+}
+
+void 
+balloon_update_driver_allowance(long delta)
+{
+	unsigned long flags;
+
+	balloon_lock(flags);
+	driver_pages += delta;
+	balloon_unlock(flags);
+}
+
+#if 0
+static int dealloc_pte_fn(
+	pte_t *pte, struct page *pte_page, unsigned long addr, void *data)
+{
+	unsigned long mfn = pte_mfn(*pte);
+	int ret;
+	struct xen_memory_reservation reservation = {
+		.extent_start = &mfn,
+		.nr_extents   = 1,
+		.extent_order = 0,
+		.domid        = DOMID_SELF
+	};
+	set_pte_at(&init_mm, addr, pte, __pte_ma(0));
+	set_phys_to_machine(__pa(addr) >> PAGE_SHIFT, INVALID_P2M_ENTRY);
+	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+	PANIC_IF(ret != 1);
+	return 0;
+}
+
+#endif
+vm_page_t
+balloon_alloc_empty_page_range(unsigned long nr_pages)
+{
+	unsigned long flags;
+	vm_page_t pages;
+	int i;
+	unsigned long *mfn_list;
+	struct xen_memory_reservation reservation = {
+		.address_bits = 0,
+		.extent_order = 0,
+		.domid        = DOMID_SELF
+	};
+
+	pages = vm_page_alloc_contig(nr_pages, 0, -1, 4, 4)
+	if (pages == NULL)
+		return NULL;
+	
+	mfn_list = malloc(nr_pages*sizeof(unsigned long), M_DEVBUF, M_WAITOK);
+	
+	for (i = 0; i < nr_pages; i++) {
+		mfn_list[i] = PFNTOMFN(VM_PAGE_TO_PHYS(pages[i]) >> PAGE_SHIFT);
+		PFNTOMFN(i) = INVALID_P2M_ENTRY;
+		reservation.extent_start = mfn_list;
+		reservation.nr_extents = nr_pages;
+		PANIC_IF(HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation) != nr_pages);
+	}
+
+	current_pages -= nr_pages;
+
+	wakeup(balloon_process);
+
+	return pages;
+}
+
+void 
+balloon_dealloc_empty_page_range(vm_page_t page, unsigned long nr_pages)
+{
+	unsigned long i, flags;
+
+	for (i = 0; i < nr_pages; i++)
+		balloon_append(page + i);
+
+	wakeup(balloon_process);
+}
+
+#endif