diff options
| -rw-r--r-- | drivers/virtio/Kconfig | 10 | ||||
| -rw-r--r-- | drivers/virtio/Makefile | 1 | ||||
| -rw-r--r-- | drivers/virtio/virtio_balloon.c | 284 | ||||
| -rw-r--r-- | include/linux/virtio_balloon.h | 18 |
4 files changed, 313 insertions, 0 deletions
diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig index 833db2f36e9..3dd6294d10b 100644 --- a/drivers/virtio/Kconfig +++ b/drivers/virtio/Kconfig @@ -23,3 +23,13 @@ config VIRTIO_PCI If unsure, say M. +config VIRTIO_BALLOON + tristate "Virtio balloon driver (EXPERIMENTAL)" + select VIRTIO + select VIRTIO_RING + ---help--- + This driver supports increasing and decreasing the amount + of memory within a KVM guest. + + If unsure, say M. + diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile index cc84999f305..6738c446c19 100644 --- a/drivers/virtio/Makefile +++ b/drivers/virtio/Makefile @@ -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_VIRTIO_BALLOON) += virtio_balloon.o diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c new file mode 100644 index 00000000000..622aece1acc --- /dev/null +++ b/drivers/virtio/virtio_balloon.c @@ -0,0 +1,284 @@ +/* Virtio balloon implementation, inspired by Dor Loar and Marcelo + * Tosatti's implementations. + * + * Copyright 2008 Rusty Russell IBM Corporation + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + */ +//#define DEBUG +#include <linux/virtio.h> +#include <linux/virtio_balloon.h> +#include <linux/swap.h> +#include <linux/kthread.h> +#include <linux/freezer.h> + +struct virtio_balloon +{ + struct virtio_device *vdev; + struct virtqueue *inflate_vq, *deflate_vq; + + /* Where the ballooning thread waits for config to change. */ + wait_queue_head_t config_change; + + /* The thread servicing the balloon. */ + struct task_struct *thread; + + /* Waiting for host to ack the pages we released. */ + struct completion acked; + + /* Do we have to tell Host *before* we reuse pages? */ + bool tell_host_first; + + /* The pages we've told the Host we're not using. */ + unsigned int num_pages; + struct list_head pages; + + /* The array of pfns we tell the Host about. */ + unsigned int num_pfns; + u32 pfns[256]; +}; + +static struct virtio_device_id id_table[] = { + { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, + { 0 }, +}; + +static void balloon_ack(struct virtqueue *vq) +{ + struct virtio_balloon *vb; + unsigned int len; + + vb = vq->vq_ops->get_buf(vq, &len); + if (vb) + complete(&vb->acked); +} + +static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) +{ + struct scatterlist sg; + + sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); + + init_completion(&vb->acked); + + /* We should always be able to add one buffer to an empty queue. */ + if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0) + BUG(); + vq->vq_ops->kick(vq); + + /* When host has read buffer, this completes via balloon_ack */ + wait_for_completion(&vb->acked); +} + +static void fill_balloon(struct virtio_balloon *vb, size_t num) +{ + /* We can only do one array worth at a time. */ + num = min(num, ARRAY_SIZE(vb->pfns)); + + for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { + struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY); + if (!page) { + if (printk_ratelimit()) + dev_printk(KERN_INFO, &vb->vdev->dev, + "Out of puff! Can't get %zu pages\n", + num); + /* Sleep for at least 1/5 of a second before retry. */ + msleep(200); + break; + } + vb->pfns[vb->num_pfns] = page_to_pfn(page); + totalram_pages--; + vb->num_pages++; + list_add(&page->lru, &vb->pages); + } + + /* Didn't get any? Oh well. */ + if (vb->num_pfns == 0) + return; + + tell_host(vb, vb->inflate_vq); +} + +static void release_pages_by_pfn(const u32 pfns[], unsigned int num) +{ + unsigned int i; + + for (i = 0; i < num; i++) { + __free_page(pfn_to_page(pfns[i])); + totalram_pages++; + } +} + +static void leak_balloon(struct virtio_balloon *vb, size_t num) +{ + struct page *page; + + /* We can only do one array worth at a time. */ + num = min(num, ARRAY_SIZE(vb->pfns)); + + for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { + page = list_first_entry(&vb->pages, struct page, lru); + list_del(&page->lru); + vb->pfns[vb->num_pfns] = page_to_pfn(page); + vb->num_pages--; + } + + if (vb->tell_host_first) { + tell_host(vb, vb->deflate_vq); + release_pages_by_pfn(vb->pfns, vb->num_pfns); + } else { + release_pages_by_pfn(vb->pfns, vb->num_pfns); + tell_host(vb, vb->deflate_vq); + } +} + +static void virtballoon_changed(struct virtio_device *vdev) +{ + struct virtio_balloon *vb = vdev->priv; + + wake_up(&vb->config_change); +} + +static inline int towards_target(struct virtio_balloon *vb) +{ + u32 v; + __virtio_config_val(vb->vdev, + offsetof(struct virtio_balloon_config, num_pages), + &v); + return v - vb->num_pages; +} + +static void update_balloon_size(struct virtio_balloon *vb) +{ + __le32 actual = cpu_to_le32(vb->num_pages); + + vb->vdev->config->set(vb->vdev, + offsetof(struct virtio_balloon_config, actual), + &actual, sizeof(actual)); +} + +static int balloon(void *_vballoon) +{ + struct virtio_balloon *vb = _vballoon; + + set_freezable(); + while (!kthread_should_stop()) { + int diff; + + try_to_freeze(); + wait_event_interruptible(vb->config_change, + (diff = towards_target(vb)) != 0 + || kthread_should_stop()); + if (diff > 0) + fill_balloon(vb, diff); + else if (diff < 0) + leak_balloon(vb, -diff); + update_balloon_size(vb); + } + return 0; +} + +static int virtballoon_probe(struct virtio_device *vdev) +{ + struct virtio_balloon *vb; + int err; + + vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); + if (!vb) { + err = -ENOMEM; + goto out; + } + + INIT_LIST_HEAD(&vb->pages); + vb->num_pages = 0; + init_waitqueue_head(&vb->config_change); + vb->vdev = vdev; + + /* We expect two virtqueues. */ + vb->inflate_vq = vdev->config->find_vq(vdev, 0, balloon_ack); + if (IS_ERR(vb->inflate_vq)) { + err = PTR_ERR(vb->inflate_vq); + goto out_free_vb; + } + + vb->deflate_vq = vdev->config->find_vq(vdev, 1, balloon_ack); + if (IS_ERR(vb->deflate_vq)) { + err = PTR_ERR(vb->deflate_vq); + goto out_del_inflate_vq; + } + + vb->thread = kthread_run(balloon, vb, "vballoon"); + if (IS_ERR(vb->thread)) { + err = PTR_ERR(vb->thread); + goto out_del_deflate_vq; + } + + vb->tell_host_first + = vdev->config->feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); + + return 0; + +out_del_deflate_vq: + vdev->config->del_vq(vb->deflate_vq); +out_del_inflate_vq: + vdev->config->del_vq(vb->inflate_vq); +out_free_vb: + kfree(vb); +out: + return err; +} + +static void virtballoon_remove(struct virtio_device *vdev) +{ + struct virtio_balloon *vb = vdev->priv; + + kthread_stop(vb->thread); + + /* There might be pages left in the balloon: free them. */ + while (vb->num_pages) + leak_balloon(vb, vb->num_pages); + + /* Now we reset the device so we can clean up the queues. */ + vdev->config->reset(vdev); + + vdev->config->del_vq(vb->deflate_vq); + vdev->config->del_vq(vb->inflate_vq); + kfree(vb); +} + +static struct virtio_driver virtio_balloon = { + .driver.name = KBUILD_MODNAME, + .driver.owner = THIS_MODULE, + .id_table = id_table, + .probe = virtballoon_probe, + .remove = __devexit_p(virtballoon_remove), + .config_changed = virtballoon_changed, +}; + +static int __init init(void) +{ + return register_virtio_driver(&virtio_balloon); +} + +static void __exit fini(void) +{ + unregister_virtio_driver(&virtio_balloon); +} +module_init(init); +module_exit(fini); + +MODULE_DEVICE_TABLE(virtio, id_table); +MODULE_DESCRIPTION("Virtio balloon driver"); +MODULE_LICENSE("GPL"); diff --git a/include/linux/virtio_balloon.h b/include/linux/virtio_balloon.h new file mode 100644 index 00000000000..979524ee75b --- /dev/null +++ b/include/linux/virtio_balloon.h @@ -0,0 +1,18 @@ +#ifndef _LINUX_VIRTIO_BALLOON_H +#define _LINUX_VIRTIO_BALLOON_H +#include <linux/virtio_config.h> + +/* The ID for virtio_balloon */ +#define VIRTIO_ID_BALLOON 5 + +/* The feature bitmap for virtio balloon */ +#define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */ + +struct virtio_balloon_config +{ + /* Number of pages host wants Guest to give up. */ + __le32 num_pages; + /* Number of pages we've actually got in balloon. */ + __le32 actual; +}; +#endif /* _LINUX_VIRTIO_BALLOON_H */ |