kvm guest balloon driver

Following patch introduces a KVM guest balloon driver. Communication to/from the host is performed via virtio.

Next patch implements the QEMU driver and handling.

Signed-off-by Marcelo Tosatti <[email protected]>

Index: linux-2.6-nv/drivers/virtio/Kconfig
===================================================================

drivers/virtio/Kconfig +9 -0

@@ -23,3 +23,12 @@ config VIRTIO_PCI
 
 	  If unsure, say M.
 
+config KVM_BALLOON
+	tristate "KVM balloon driver (EXPERIMENTAL)"
+	depends on VIRTIO_PCI
+	---help---
+	 This driver provides support for ballooning memory in/out of a
+	 KVM paravirt guest.	
+
+	 If unsure, say M.
+

Index: linux-2.6-nv/drivers/virtio/Makefile
===================================================================

drivers/virtio/Makefile +1 -0

@@ -1,3 +1,4 @@
 obj-$(CONFIG_VIRTIO) += virtio.o
 obj-$(CONFIG_VIRTIO_RING) += virtio_ring.o
 obj-$(CONFIG_VIRTIO_PCI) += virtio_pci.o
+obj-$(CONFIG_KVM_BALLOON) += kvm_balloon.o

Index: linux-2.6-nv/drivers/virtio/kvm_balloon.c
===================================================================

drivers/virtio/kvm_balloon.c new file +27 -0

@@ -0,0 +1,577 @@
+/*
+ * KVM guest balloon driver
+ *
+ * Copyright (C) 2007, Qumranet, Inc., Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/[email protected]>
+ * Copyright (C) 2007, Red Hat, Inc., Marcelo Tosatti <[email protected]>
+ * 
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#include <asm/uaccess.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/pci.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/wait.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+#include <linux/version.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_pci.h>
+#include <linux/preempt.h>

drivers/virtio/kvm_balloon.c new file +84 -0

+struct virtio_balloon_hdr {
+	uint8_t cmd;
+	uint8_t status;
+};
+
+#define BALLOON_DATA_SIZE 200
+
+struct balloon_buf {
+	struct virtio_balloon_hdr hdr;
+	u8 data[BALLOON_DATA_SIZE];
+};
+
+struct balloon_work {
+	struct balloon_buf *buf;
+	struct list_head list;
+};
+
+#define VIRTIO_MAX_SG 2
+
+struct virtballoon {
+	struct virtio_device *dev;
+	struct virtqueue *vq;
+	struct task_struct *balloon_thread;
+	wait_queue_head_t balloon_wait;
+	wait_queue_head_t rmmod_wait;
+	uint32_t target_nrpages;
+	atomic_t inflight_bufs;
+};
+
+struct balloon_page {
+	struct page *bpage;
+	struct list_head bp_list;
+};
+
+struct virtballoon virtballoon;
+
+struct balloon_buf *alloc_balloon_buf(void)
+{
+	struct balloon_buf *buf;
+
+	buf = kzalloc(sizeof(struct balloon_buf), GFP_KERNEL);
+	if (!buf)
+		printk(KERN_ERR "%s: allocation failed\n", __func__);
+
+	return buf;
+}
+
+static int send_balloon_buf(uint8_t cmd, struct balloon_buf *buf)
+{
+	struct scatterlist sg[VIRTIO_MAX_SG];
+	struct virtqueue *vq = virtballoon.vq;
+	int err = 0;
+
+	buf->hdr.cmd = cmd;
+
+	sg_init_table(sg, VIRTIO_MAX_SG);
+	sg_set_buf(&sg[0], &buf->hdr, sizeof(buf->hdr));
+	sg_set_buf(&sg[1], &buf->data, sizeof(buf->data));
+
+	spin_lock_irq(&balloon_queue_lock);
+	err = vq->vq_ops->add_buf(vq, sg, 0, 2, buf);
+	if (err) {
+		printk("%s: add_buf err\n", __func__);
+		goto out;
+	}
+	atomic_inc(&virtballoon.inflight_bufs);
+
+	/* TODO: kick several balloon buffers at once */
+	vq->vq_ops->kick(vq);
+out:
+	spin_unlock_irq(&balloon_queue_lock);
+	return err;
+}
+
+static int kvm_balloon_inflate(int32_t npages)
+{
+	LIST_HEAD(tmp_list);
+	struct balloon_page *node, *tmp;
+	struct balloon_buf *buf;
+	u32 *pfn;
+	int allocated = 0;
+	int i, r = -ENOMEM;
+
+	buf = alloc_balloon_buf();

drivers/virtio/kvm_balloon.c new file +33 -0

+		node->bpage = alloc_page(GFP_HIGHUSER | __GFP_NORETRY);
+		if (!node->bpage) {
+			kfree(node);
+			goto out_free;
+		}
+
+		list_add(&node->bp_list, &tmp_list);
+		allocated++;
+		*pfn = page_to_pfn(node->bpage);
+		pfn++;
+	}
+
+	r = send_balloon_buf(CMD_BALLOON_INFLATE, buf);
+	if (r)
+		goto out_free;
+
+	spin_lock(&balloon_plist_lock);
+	list_splice(&tmp_list, &balloon_plist);
+	balloon_size += allocated;
+	totalram_pages -= allocated;
+	dprintk("%s: current balloon size=%d\n", __FUNCTION__,
+	       balloon_size);
+	spin_unlock(&balloon_plist_lock);
+	return allocated;
+
+out_free:
+	list_for_each_entry_safe(node, tmp, &tmp_list, bp_list) {
+		__free_page(node->bpage);
+		list_del(&node->bp_list);
+		kfree(node);
+	}
+	return r;
+}

drivers/virtio/kvm_balloon.c new file +16 -0

+
+static int balloon_probe(struct virtio_device *vdev)
+{
+	struct virtio_pci_device *pvdev = to_vp_device(vdev);
+	int err = -EBUSY;
+
+	if (virtballoon.dev) { 
+		printk("kvm_ballon: error, already registered\n");
+		return -EBUSY;
+	}
+
+	virtballoon.vq = vdev->config->find_vq(vdev, 0, balloon_tx_done);
+	if (IS_ERR(virtballoon.vq)) {
+		printk("%s: error finding vq\n", __func__);
+		return -EINVAL;
+	}

drivers/virtio/kvm_balloon.c new file +67 -0

+
+	virtballoon.balloon_thread = kthread_run(balloon_thread,
+						 &virtballoon,
+						 "kvm_balloond");
+	printk("kvm_balloon: registered\n");
+
+	return 0;
+
+out_free_vq:
+	vdev->config->del_vq(virtballoon.vq);
+	virtballoon.dev = NULL;
+	return err;
+}
+
+static void balloon_remove(struct virtio_device *vdev)
+{
+	kthread_stop(virtballoon.balloon_thread);
+	vdev->config->del_vq(virtballoon.vq);
+}
+
+static struct virtio_driver virtio_balloon = {
+	.driver.name =  KBUILD_MODNAME,
+	.driver.owner = THIS_MODULE,
+	.id_table =     id_table,
+	.probe =        balloon_probe,
+	.remove =	__devexit_p(balloon_remove),
+};
+
+module_param(kvm_balloon_debug, int, 0);
+
+static int __init kvm_balloon_init(void)
+{
+	virtballoon.dev = NULL;
+
+	return register_virtio_driver(&virtio_balloon);
+}
+
+static void __exit kvm_balloon_exit(void)
+{
+	spin_lock(&balloon_plist_lock);
+	if (balloon_size) {
+		DEFINE_WAIT(wait);
+
+		virtballoon.target_nrpages += balloon_size;
+		spin_unlock(&balloon_plist_lock);
+		virtballoon.dev->config->set(virtballoon.dev, 0, 
+					   &virtballoon.target_nrpages,
+					   sizeof(virtballoon.target_nrpages));
+		wake_up(&virtballoon.balloon_wait);
+		prepare_to_wait(&virtballoon.rmmod_wait, &wait,
+				TASK_UNINTERRUPTIBLE);
+		schedule();
+		finish_wait(&virtballoon.rmmod_wait, &wait);
+		spin_lock(&balloon_plist_lock);
+	}
+
+	if (balloon_size)
+		printk(KERN_ERR "%s: exit while balloon not empty!\n",
+			__FUNCTION__);
+
+	spin_unlock(&balloon_plist_lock);
+
+	unregister_virtio_driver(&virtio_balloon);
+}
+
+module_init(kvm_balloon_init);
+module_exit(kvm_balloon_exit);

Index: linux-2.6-nv/drivers/virtio/virtio_pci.c
===================================================================

drivers/virtio/virtio_pci.c +1 -20

@@ -30,20 +30,6 @@ MODULE_DESCRIPTION("virtio-pci");
 MODULE_LICENSE("GPL");
 MODULE_VERSION("1");
 
-/* Our device structure */
-struct virtio_pci_device
-{
-	struct virtio_device vdev;
-	struct pci_dev *pci_dev;
-
-	/* the IO mapping for the PCI config space */
-	void *ioaddr;
-
-	/* a list of queues so we can dispatch IRQs */
-	spinlock_t lock;
-	struct list_head virtqueues;
-};
-
 struct virtio_pci_vq_info
 {
 	/* the actual virtqueue */

@@ -67,6 +53,7 @@ static struct pci_device_id virtio_pci_i
 	{ 0x1AF4, 0x1000, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 }, /* Dummy entry */
 	{ 0x1AF4, 0x1001, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 }, /* Dummy entry */
 	{ 0x1AF4, 0x1002, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 }, /* Dummy entry */
+	{ 0x1AF4, 0x1003, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 }, /* Balloon */
 	{ 0 },
 };
 

@@ -89,12 +76,6 @@ static struct device virtio_pci_root = {
 /* Unique numbering for devices under the kvm root */
 static unsigned int dev_index;
 
-/* Convert a generic virtio device to our structure */
-static struct virtio_pci_device *to_vp_device(struct virtio_device *vdev)
-{
-	return container_of(vdev, struct virtio_pci_device, vdev);
-}
-
 /* virtio config->feature() implementation */
 static bool vp_feature(struct virtio_device *vdev, unsigned bit)
 {

Index: linux-2.6-nv/include/linux/virtio_pci.h
===================================================================

include/linux/virtio_pci.h +11 -0

@@ -19,6 +19,26 @@
 
 #include <linux/virtio_config.h>
 
+/* Our device structure */
+struct virtio_pci_device
+{
+	struct virtio_device vdev;
+	struct pci_dev *pci_dev;
+
+	/* the IO mapping for the PCI config space */
+	void *ioaddr;
+
+	/* a list of queues so we can dispatch IRQs */
+	spinlock_t lock;

include/linux/virtio_pci.h +0 -1

 /* A 32-bit r/o bitmask of the features supported by the host */
 #define VIRTIO_PCI_HOST_FEATURES	0
 
 
-------------------------------------------------------------------------

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Quoted 3 lines · Marcelo Tosatti

Following patch introduces a KVM guest balloon driver. Communication to/from the host is performed via virtio.

Quoted 5 lines

drivers/virtio/kvm_balloon.c new file +5 -0

+	virtballoon.dev = vdev;
+	init_waitqueue_head(&virtballoon.balloon_wait);
+	init_waitqueue_head(&virtballoon.rmmod_wait);
+	atomic_set(&virtballoon.inflight_bufs, 0);
+

drivers/virtio/kvm_balloon.c line 510

Quoted 5 lines

drivers/virtio/kvm_balloon.c new file +4 -0

+	err = request_irq(pvdev->pci_dev->irq, balloon_irq, IRQF_SHARED,
+			  pvdev->vdev.dev.bus_id, &virtballoon);
+	if (err)
+		goto out_free_vq;

Why is it taking over the irq? This is very, very wrong. A virtio device cannot be dependent on being used on top of the virtio-pci backend.

Quoted 6 lines · Anthony Liguori

Quoted 4 lines · Marcelo Tosatti

Following patch introduces a KVM guest balloon driver. Communication to/from the host is performed via virtio.

I'll address the other comments.

Quoted 5 lines

Quoted 5 lines

drivers/virtio/kvm_balloon.c new file +5 -0

+	virtballoon.dev = vdev;
+	init_waitqueue_head(&virtballoon.balloon_wait);
+	init_waitqueue_head(&virtballoon.rmmod_wait);
+	atomic_set(&virtballoon.inflight_bufs, 0);
+

Quoted 9 lines

drivers/virtio/kvm_balloon.c line 510

Quoted 6 lines

drivers/virtio/kvm_balloon.c new file +4 -0

+	err = request_irq(pvdev->pci_dev->irq, balloon_irq, IRQF_SHARED,
+			  pvdev->vdev.dev.bus_id, &virtballoon);
+	if (err)
+		goto out_free_vq;

Why is it taking over the irq? This is very, very wrong. A virtio device cannot be dependent on being used on top of the virtio-pci backend.

A notification is necessary whenever the host changes the target value in the config space. So right now this notification is sharing the same IRQ as the main PCI device.

Do you have any suggestion on how to retrieve the IRQ of the virtio device, or some other notification mechanism?

BTW, I don't think the target should be a config value. You don't gain anything from it being in the config space and it's somewhat unnatural for a virtio device. It makes more sense as a message to the guest.

Quoted 5 lines · Anthony Liguori

BTW, I don't think the target should be a config value. You don't gain anything from it being in the config space and it's somewhat unnatural for a virtio device. It makes more sense as a message to the guest.

I disagree. The target is state, not an individual item that needs to be acted on. Having it as a single variable means that multiple changes are collapsed automatically, and that the the setting survives module reload.

It's like a volume control, it doesn't send messages when you turn it, it just sets a value.

(maybe a thermostat knob is a better analogy, with the driver being the circuitry around the knob that tries to control the temperature to match the setting)

I believe state-like controls will be useful for other settings, like ethernet link state.

Quoted 2 lines · Anthony Liguori

BTW, I don't think the target should be a config value. You don't gain anything from it being in the config space and it's somewhat unnatural for a virtio device. It makes more sense as a message to the guest.

I disagree. The target is state, not an individual item that needs to be acted on. Having it as a single variable means that multiple changes are collapsed automatically, and that the the setting survives module reload.

It's like a volume control, it doesn't send messages when you turn it, it just sets a value.

(maybe a thermostat knob is a better analogy, with the driver being the circuitry around the knob that tries to control the temperature to match the setting)

I believe state-like controls will be useful for other settings, like ethernet link state.

BTW, I don't think the target should be a config value. You don't gain anything from it being in the config space and it's somewhat unnatural for a virtio device. It makes more sense as a message to the guest.

Quoted 6 lines · Anthony Liguori

Quoted 4 lines · Marcelo Tosatti

Following patch introduces a KVM guest balloon driver. Communication to/from the host is performed via virtio.

I'll address the other comments.

Quoted 4 lines

Quoted 4 lines

drivers/virtio/kvm_balloon.c new file +4 -0

+	virtballoon.dev = vdev;
+	init_waitqueue_head(&virtballoon.balloon_wait);
+	init_waitqueue_head(&virtballoon.rmmod_wait);
+	atomic_set(&virtballoon.inflight_bufs, 0);

Quoted 9 lines

drivers/virtio/kvm_balloon.c line 510

Quoted 7 lines

drivers/virtio/kvm_balloon.c new file +5 -0

+
+	err = request_irq(pvdev->pci_dev->irq, balloon_irq, IRQF_SHARED,
+			  pvdev->vdev.dev.bus_id, &virtballoon);
+	if (err)
+		goto out_free_vq;

Why is it taking over the irq? This is very, very wrong. A virtio device cannot be dependent on being used on top of the virtio-pci backend.

A notification is necessary whenever the host changes the target value in the config space. So right now this notification is sharing the same IRQ as the main PCI device.

Do you have any suggestion on how to retrieve the IRQ of the virtio device, or some other notification mechanism?

Quoted 3 lines

Why is it taking over the irq? This is very, very wrong. A virtio device cannot be dependent on being used on top of the virtio-pci backend.

A notification is necessary whenever the host changes the target value in the config space. So right now this notification is sharing the same IRQ as the main PCI device.

Do you have any suggestion on how to retrieve the IRQ of the virtio device, or some other notification mechanism?

Quoted 2 lines · Marcelo Tosatti

Do you have any suggestion on how to retrieve the IRQ of the virtio device, or some other notification mechanism?

One way would be to send a "look at config" queue message, but it seems that it is a fairly generic operation. Maybe virtio can add support for it, with a new callback.

Quoted 2 lines · Marcelo Tosatti

Do you have any suggestion on how to retrieve the IRQ of the virtio device, or some other notification mechanism?

One way would be to send a "look at config" queue message, but it seems that it is a fairly generic operation. Maybe virtio can add support for it, with a new callback.

Quoted 2 lines

Why is it taking over the irq? This is very, very wrong. A virtio device cannot be dependent on being used on top of the virtio-pci backend.

A notification is necessary whenever the host changes the target value in the config space. So right now this notification is sharing the same IRQ as the main PCI device.

Do you have any suggestion on how to retrieve the IRQ of the virtio device, or some other notification mechanism?

Instead of allocating a node for each page, you could use page->private

Quoted 1 line · Anthony Liguori

Instead of allocating a node for each page, you could use page->private

page->lru is probably better for this so splice still works etc... (the struct page isn't visible to the guest VM so it's free to use)

Quoted 1 line · Anthony Liguori

Instead of allocating a node for each page, you could use page->private

page->lru is probably better for this so splice still works etc... (the struct page isn't visible to the guest VM so it's free to use)

Quoted 3 lines · Marcelo Tosatti

Following patch introduces a KVM guest balloon driver. Communication to/from the host is performed via virtio.

Quoted 5 lines

drivers/virtio/kvm_balloon.c new file +5 -0

+	virtballoon.dev = vdev;
+	init_waitqueue_head(&virtballoon.balloon_wait);
+	init_waitqueue_head(&virtballoon.rmmod_wait);
+	atomic_set(&virtballoon.inflight_bufs, 0);
+

drivers/virtio/kvm_balloon.c line 510

Quoted 5 lines

drivers/virtio/kvm_balloon.c new file +4 -0

+	err = request_irq(pvdev->pci_dev->irq, balloon_irq, IRQF_SHARED,
+			  pvdev->vdev.dev.bus_id, &virtballoon);
+	if (err)
+		goto out_free_vq;

Why is it taking over the irq? This is very, very wrong. A virtio device cannot be dependent on being used on top of the virtio-pci backend.

Instead of allocating a node for each page, you could use page->private

Following patch introduces a KVM guest balloon driver. Communication to/from the host is performed via virtio.

Next patch implements the QEMU driver and handling.

Signed-off-by Marcelo Tosatti <[email protected]>

Index: linux-2.6-nv/drivers/virtio/Kconfig
===================================================================

drivers/virtio/Kconfig +9 -0

@@ -23,3 +23,12 @@ config VIRTIO_PCI
 
 	  If unsure, say M.
 
+config KVM_BALLOON
+	tristate "KVM balloon driver (EXPERIMENTAL)"
+	depends on VIRTIO_PCI
+	---help---
+	 This driver provides support for ballooning memory in/out of a
+	 KVM paravirt guest.	
+
+	 If unsure, say M.
+

Index: linux-2.6-nv/drivers/virtio/Makefile
===================================================================

drivers/virtio/Makefile +1 -0

@@ -1,3 +1,4 @@
 obj-$(CONFIG_VIRTIO) += virtio.o
 obj-$(CONFIG_VIRTIO_RING) += virtio_ring.o
 obj-$(CONFIG_VIRTIO_PCI) += virtio_pci.o
+obj-$(CONFIG_KVM_BALLOON) += kvm_balloon.o

Index: linux-2.6-nv/drivers/virtio/kvm_balloon.c
===================================================================

drivers/virtio/kvm_balloon.c new file +27 -0

@@ -0,0 +1,577 @@
+/*
+ * KVM guest balloon driver
+ *
+ * Copyright (C) 2007, Qumranet, Inc., Dor Laor <[email protected]>
+ * Copyright (C) 2007, Red Hat, Inc., Marcelo Tosatti <[email protected]>
+ * 
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#include <asm/uaccess.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/pci.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/wait.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+#include <linux/version.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_pci.h>
+#include <linux/preempt.h>

drivers/virtio/kvm_balloon.c new file +84 -0

+struct virtio_balloon_hdr {
+	uint8_t cmd;
+	uint8_t status;
+};
+
+#define BALLOON_DATA_SIZE 200
+
+struct balloon_buf {
+	struct virtio_balloon_hdr hdr;
+	u8 data[BALLOON_DATA_SIZE];
+};
+
+struct balloon_work {
+	struct balloon_buf *buf;
+	struct list_head list;
+};
+
+#define VIRTIO_MAX_SG 2
+
+struct virtballoon {
+	struct virtio_device *dev;
+	struct virtqueue *vq;
+	struct task_struct *balloon_thread;
+	wait_queue_head_t balloon_wait;
+	wait_queue_head_t rmmod_wait;
+	uint32_t target_nrpages;
+	atomic_t inflight_bufs;
+};
+
+struct balloon_page {
+	struct page *bpage;
+	struct list_head bp_list;
+};
+
+struct virtballoon virtballoon;
+
+struct balloon_buf *alloc_balloon_buf(void)
+{
+	struct balloon_buf *buf;
+
+	buf = kzalloc(sizeof(struct balloon_buf), GFP_KERNEL);
+	if (!buf)
+		printk(KERN_ERR "%s: allocation failed\n", __func__);
+
+	return buf;
+}
+
+static int send_balloon_buf(uint8_t cmd, struct balloon_buf *buf)
+{
+	struct scatterlist sg[VIRTIO_MAX_SG];
+	struct virtqueue *vq = virtballoon.vq;
+	int err = 0;
+
+	buf->hdr.cmd = cmd;
+
+	sg_init_table(sg, VIRTIO_MAX_SG);
+	sg_set_buf(&sg[0], &buf->hdr, sizeof(buf->hdr));
+	sg_set_buf(&sg[1], &buf->data, sizeof(buf->data));
+
+	spin_lock_irq(&balloon_queue_lock);
+	err = vq->vq_ops->add_buf(vq, sg, 0, 2, buf);
+	if (err) {
+		printk("%s: add_buf err\n", __func__);
+		goto out;
+	}
+	atomic_inc(&virtballoon.inflight_bufs);
+
+	/* TODO: kick several balloon buffers at once */
+	vq->vq_ops->kick(vq);
+out:
+	spin_unlock_irq(&balloon_queue_lock);
+	return err;
+}
+
+static int kvm_balloon_inflate(int32_t npages)
+{
+	LIST_HEAD(tmp_list);
+	struct balloon_page *node, *tmp;
+	struct balloon_buf *buf;
+	u32 *pfn;
+	int allocated = 0;
+	int i, r = -ENOMEM;
+
+	buf = alloc_balloon_buf();

drivers/virtio/kvm_balloon.c new file +33 -0

+		node->bpage = alloc_page(GFP_HIGHUSER | __GFP_NORETRY);
+		if (!node->bpage) {
+			kfree(node);
+			goto out_free;
+		}
+
+		list_add(&node->bp_list, &tmp_list);
+		allocated++;
+		*pfn = page_to_pfn(node->bpage);
+		pfn++;
+	}
+
+	r = send_balloon_buf(CMD_BALLOON_INFLATE, buf);
+	if (r)
+		goto out_free;
+
+	spin_lock(&balloon_plist_lock);
+	list_splice(&tmp_list, &balloon_plist);
+	balloon_size += allocated;
+	totalram_pages -= allocated;
+	dprintk("%s: current balloon size=%d\n", __FUNCTION__,
+	       balloon_size);
+	spin_unlock(&balloon_plist_lock);
+	return allocated;
+
+out_free:
+	list_for_each_entry_safe(node, tmp, &tmp_list, bp_list) {
+		__free_page(node->bpage);
+		list_del(&node->bp_list);
+		kfree(node);
+	}
+	return r;
+}

drivers/virtio/kvm_balloon.c new file +16 -0

+
+static int balloon_probe(struct virtio_device *vdev)
+{
+	struct virtio_pci_device *pvdev = to_vp_device(vdev);
+	int err = -EBUSY;
+
+	if (virtballoon.dev) { 
+		printk("kvm_ballon: error, already registered\n");
+		return -EBUSY;
+	}
+
+	virtballoon.vq = vdev->config->find_vq(vdev, 0, balloon_tx_done);
+	if (IS_ERR(virtballoon.vq)) {
+		printk("%s: error finding vq\n", __func__);
+		return -EINVAL;
+	}

drivers/virtio/kvm_balloon.c new file +67 -0

+
+	virtballoon.balloon_thread = kthread_run(balloon_thread,
+						 &virtballoon,
+						 "kvm_balloond");
+	printk("kvm_balloon: registered\n");
+
+	return 0;
+
+out_free_vq:
+	vdev->config->del_vq(virtballoon.vq);
+	virtballoon.dev = NULL;
+	return err;
+}
+
+static void balloon_remove(struct virtio_device *vdev)
+{
+	kthread_stop(virtballoon.balloon_thread);
+	vdev->config->del_vq(virtballoon.vq);
+}
+
+static struct virtio_driver virtio_balloon = {
+	.driver.name =  KBUILD_MODNAME,
+	.driver.owner = THIS_MODULE,
+	.id_table =     id_table,
+	.probe =        balloon_probe,
+	.remove =	__devexit_p(balloon_remove),
+};
+
+module_param(kvm_balloon_debug, int, 0);
+
+static int __init kvm_balloon_init(void)
+{
+	virtballoon.dev = NULL;
+
+	return register_virtio_driver(&virtio_balloon);
+}
+
+static void __exit kvm_balloon_exit(void)
+{
+	spin_lock(&balloon_plist_lock);
+	if (balloon_size) {
+		DEFINE_WAIT(wait);
+
+		virtballoon.target_nrpages += balloon_size;
+		spin_unlock(&balloon_plist_lock);
+		virtballoon.dev->config->set(virtballoon.dev, 0, 
+					   &virtballoon.target_nrpages,
+					   sizeof(virtballoon.target_nrpages));
+		wake_up(&virtballoon.balloon_wait);
+		prepare_to_wait(&virtballoon.rmmod_wait, &wait,
+				TASK_UNINTERRUPTIBLE);
+		schedule();
+		finish_wait(&virtballoon.rmmod_wait, &wait);
+		spin_lock(&balloon_plist_lock);
+	}
+
+	if (balloon_size)
+		printk(KERN_ERR "%s: exit while balloon not empty!\n",
+			__FUNCTION__);
+
+	spin_unlock(&balloon_plist_lock);
+
+	unregister_virtio_driver(&virtio_balloon);
+}
+
+module_init(kvm_balloon_init);
+module_exit(kvm_balloon_exit);

Index: linux-2.6-nv/drivers/virtio/virtio_pci.c
===================================================================

drivers/virtio/virtio_pci.c +1 -20

@@ -30,20 +30,6 @@ MODULE_DESCRIPTION("virtio-pci");
 MODULE_LICENSE("GPL");
 MODULE_VERSION("1");
 
-/* Our device structure */
-struct virtio_pci_device
-{
-	struct virtio_device vdev;
-	struct pci_dev *pci_dev;
-
-	/* the IO mapping for the PCI config space */
-	void *ioaddr;
-
-	/* a list of queues so we can dispatch IRQs */
-	spinlock_t lock;
-	struct list_head virtqueues;
-};
-
 struct virtio_pci_vq_info
 {
 	/* the actual virtqueue */

@@ -67,6 +53,7 @@ static struct pci_device_id virtio_pci_i
 	{ 0x1AF4, 0x1000, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 }, /* Dummy entry */
 	{ 0x1AF4, 0x1001, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 }, /* Dummy entry */
 	{ 0x1AF4, 0x1002, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 }, /* Dummy entry */
+	{ 0x1AF4, 0x1003, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 }, /* Balloon */
 	{ 0 },
 };
 

@@ -89,12 +76,6 @@ static struct device virtio_pci_root = {
 /* Unique numbering for devices under the kvm root */
 static unsigned int dev_index;
 
-/* Convert a generic virtio device to our structure */
-static struct virtio_pci_device *to_vp_device(struct virtio_device *vdev)
-{
-	return container_of(vdev, struct virtio_pci_device, vdev);
-}
-
 /* virtio config->feature() implementation */
 static bool vp_feature(struct virtio_device *vdev, unsigned bit)
 {

Index: linux-2.6-nv/include/linux/virtio_pci.h
===================================================================

include/linux/virtio_pci.h +11 -0

@@ -19,6 +19,26 @@
 
 #include <linux/virtio_config.h>
 
+/* Our device structure */
+struct virtio_pci_device
+{
+	struct virtio_device vdev;
+	struct pci_dev *pci_dev;
+
+	/* the IO mapping for the PCI config space */
+	void *ioaddr;
+
+	/* a list of queues so we can dispatch IRQs */
+	spinlock_t lock;

include/linux/virtio_pci.h +0 -1

 /* A 32-bit r/o bitmask of the features supported by the host */
 #define VIRTIO_PCI_HOST_FEATURES	0
 
 
-------------------------------------------------------------------------

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