Rusty Russell | 6b35e40 | 2008-02-04 23:50:12 -0500 | [diff] [blame] | 1 | /* Virtio balloon implementation, inspired by Dor Loar and Marcelo |
| 2 | * Tosatti's implementations. |
| 3 | * |
| 4 | * Copyright 2008 Rusty Russell IBM Corporation |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License as published by |
| 8 | * the Free Software Foundation; either version 2 of the License, or |
| 9 | * (at your option) any later version. |
| 10 | * |
| 11 | * This program is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | * GNU General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License |
| 17 | * along with this program; if not, write to the Free Software |
| 18 | * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| 19 | */ |
| 20 | //#define DEBUG |
| 21 | #include <linux/virtio.h> |
| 22 | #include <linux/virtio_balloon.h> |
| 23 | #include <linux/swap.h> |
| 24 | #include <linux/kthread.h> |
| 25 | #include <linux/freezer.h> |
Johann Felix Soden | 6659a0f | 2008-02-06 01:40:22 -0800 | [diff] [blame] | 26 | #include <linux/delay.h> |
Rusty Russell | 6b35e40 | 2008-02-04 23:50:12 -0500 | [diff] [blame] | 27 | |
| 28 | struct virtio_balloon |
| 29 | { |
| 30 | struct virtio_device *vdev; |
| 31 | struct virtqueue *inflate_vq, *deflate_vq; |
| 32 | |
| 33 | /* Where the ballooning thread waits for config to change. */ |
| 34 | wait_queue_head_t config_change; |
| 35 | |
| 36 | /* The thread servicing the balloon. */ |
| 37 | struct task_struct *thread; |
| 38 | |
| 39 | /* Waiting for host to ack the pages we released. */ |
| 40 | struct completion acked; |
| 41 | |
| 42 | /* Do we have to tell Host *before* we reuse pages? */ |
| 43 | bool tell_host_first; |
| 44 | |
| 45 | /* The pages we've told the Host we're not using. */ |
| 46 | unsigned int num_pages; |
| 47 | struct list_head pages; |
| 48 | |
| 49 | /* The array of pfns we tell the Host about. */ |
| 50 | unsigned int num_pfns; |
| 51 | u32 pfns[256]; |
| 52 | }; |
| 53 | |
| 54 | static struct virtio_device_id id_table[] = { |
| 55 | { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, |
| 56 | { 0 }, |
| 57 | }; |
| 58 | |
| 59 | static void balloon_ack(struct virtqueue *vq) |
| 60 | { |
| 61 | struct virtio_balloon *vb; |
| 62 | unsigned int len; |
| 63 | |
| 64 | vb = vq->vq_ops->get_buf(vq, &len); |
| 65 | if (vb) |
| 66 | complete(&vb->acked); |
| 67 | } |
| 68 | |
| 69 | static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) |
| 70 | { |
| 71 | struct scatterlist sg; |
| 72 | |
| 73 | sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); |
| 74 | |
| 75 | init_completion(&vb->acked); |
| 76 | |
| 77 | /* We should always be able to add one buffer to an empty queue. */ |
| 78 | if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0) |
| 79 | BUG(); |
| 80 | vq->vq_ops->kick(vq); |
| 81 | |
| 82 | /* When host has read buffer, this completes via balloon_ack */ |
| 83 | wait_for_completion(&vb->acked); |
| 84 | } |
| 85 | |
| 86 | static void fill_balloon(struct virtio_balloon *vb, size_t num) |
| 87 | { |
| 88 | /* We can only do one array worth at a time. */ |
| 89 | num = min(num, ARRAY_SIZE(vb->pfns)); |
| 90 | |
| 91 | for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { |
| 92 | struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY); |
| 93 | if (!page) { |
| 94 | if (printk_ratelimit()) |
| 95 | dev_printk(KERN_INFO, &vb->vdev->dev, |
| 96 | "Out of puff! Can't get %zu pages\n", |
| 97 | num); |
| 98 | /* Sleep for at least 1/5 of a second before retry. */ |
| 99 | msleep(200); |
| 100 | break; |
| 101 | } |
| 102 | vb->pfns[vb->num_pfns] = page_to_pfn(page); |
| 103 | totalram_pages--; |
| 104 | vb->num_pages++; |
| 105 | list_add(&page->lru, &vb->pages); |
| 106 | } |
| 107 | |
| 108 | /* Didn't get any? Oh well. */ |
| 109 | if (vb->num_pfns == 0) |
| 110 | return; |
| 111 | |
| 112 | tell_host(vb, vb->inflate_vq); |
| 113 | } |
| 114 | |
| 115 | static void release_pages_by_pfn(const u32 pfns[], unsigned int num) |
| 116 | { |
| 117 | unsigned int i; |
| 118 | |
| 119 | for (i = 0; i < num; i++) { |
| 120 | __free_page(pfn_to_page(pfns[i])); |
| 121 | totalram_pages++; |
| 122 | } |
| 123 | } |
| 124 | |
| 125 | static void leak_balloon(struct virtio_balloon *vb, size_t num) |
| 126 | { |
| 127 | struct page *page; |
| 128 | |
| 129 | /* We can only do one array worth at a time. */ |
| 130 | num = min(num, ARRAY_SIZE(vb->pfns)); |
| 131 | |
| 132 | for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { |
| 133 | page = list_first_entry(&vb->pages, struct page, lru); |
| 134 | list_del(&page->lru); |
| 135 | vb->pfns[vb->num_pfns] = page_to_pfn(page); |
| 136 | vb->num_pages--; |
| 137 | } |
| 138 | |
| 139 | if (vb->tell_host_first) { |
| 140 | tell_host(vb, vb->deflate_vq); |
| 141 | release_pages_by_pfn(vb->pfns, vb->num_pfns); |
| 142 | } else { |
| 143 | release_pages_by_pfn(vb->pfns, vb->num_pfns); |
| 144 | tell_host(vb, vb->deflate_vq); |
| 145 | } |
| 146 | } |
| 147 | |
| 148 | static void virtballoon_changed(struct virtio_device *vdev) |
| 149 | { |
| 150 | struct virtio_balloon *vb = vdev->priv; |
| 151 | |
| 152 | wake_up(&vb->config_change); |
| 153 | } |
| 154 | |
Rusty Russell | bdc1681 | 2008-03-17 22:58:15 -0500 | [diff] [blame] | 155 | static inline s64 towards_target(struct virtio_balloon *vb) |
Rusty Russell | 6b35e40 | 2008-02-04 23:50:12 -0500 | [diff] [blame] | 156 | { |
| 157 | u32 v; |
Rusty Russell | 72e61eb | 2008-05-02 21:50:49 -0500 | [diff] [blame] | 158 | vb->vdev->config->get(vb->vdev, |
| 159 | offsetof(struct virtio_balloon_config, num_pages), |
| 160 | &v, sizeof(v)); |
Rusty Russell | 6b35e40 | 2008-02-04 23:50:12 -0500 | [diff] [blame] | 161 | return v - vb->num_pages; |
| 162 | } |
| 163 | |
| 164 | static void update_balloon_size(struct virtio_balloon *vb) |
| 165 | { |
| 166 | __le32 actual = cpu_to_le32(vb->num_pages); |
| 167 | |
| 168 | vb->vdev->config->set(vb->vdev, |
| 169 | offsetof(struct virtio_balloon_config, actual), |
| 170 | &actual, sizeof(actual)); |
| 171 | } |
| 172 | |
| 173 | static int balloon(void *_vballoon) |
| 174 | { |
| 175 | struct virtio_balloon *vb = _vballoon; |
| 176 | |
| 177 | set_freezable(); |
| 178 | while (!kthread_should_stop()) { |
Rusty Russell | bdc1681 | 2008-03-17 22:58:15 -0500 | [diff] [blame] | 179 | s64 diff; |
Rusty Russell | 6b35e40 | 2008-02-04 23:50:12 -0500 | [diff] [blame] | 180 | |
| 181 | try_to_freeze(); |
| 182 | wait_event_interruptible(vb->config_change, |
| 183 | (diff = towards_target(vb)) != 0 |
| 184 | || kthread_should_stop()); |
| 185 | if (diff > 0) |
| 186 | fill_balloon(vb, diff); |
| 187 | else if (diff < 0) |
| 188 | leak_balloon(vb, -diff); |
| 189 | update_balloon_size(vb); |
| 190 | } |
| 191 | return 0; |
| 192 | } |
| 193 | |
| 194 | static int virtballoon_probe(struct virtio_device *vdev) |
| 195 | { |
| 196 | struct virtio_balloon *vb; |
| 197 | int err; |
| 198 | |
| 199 | vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); |
| 200 | if (!vb) { |
| 201 | err = -ENOMEM; |
| 202 | goto out; |
| 203 | } |
| 204 | |
| 205 | INIT_LIST_HEAD(&vb->pages); |
| 206 | vb->num_pages = 0; |
| 207 | init_waitqueue_head(&vb->config_change); |
| 208 | vb->vdev = vdev; |
| 209 | |
| 210 | /* We expect two virtqueues. */ |
| 211 | vb->inflate_vq = vdev->config->find_vq(vdev, 0, balloon_ack); |
| 212 | if (IS_ERR(vb->inflate_vq)) { |
| 213 | err = PTR_ERR(vb->inflate_vq); |
| 214 | goto out_free_vb; |
| 215 | } |
| 216 | |
| 217 | vb->deflate_vq = vdev->config->find_vq(vdev, 1, balloon_ack); |
| 218 | if (IS_ERR(vb->deflate_vq)) { |
| 219 | err = PTR_ERR(vb->deflate_vq); |
| 220 | goto out_del_inflate_vq; |
| 221 | } |
| 222 | |
| 223 | vb->thread = kthread_run(balloon, vb, "vballoon"); |
| 224 | if (IS_ERR(vb->thread)) { |
| 225 | err = PTR_ERR(vb->thread); |
| 226 | goto out_del_deflate_vq; |
| 227 | } |
| 228 | |
| 229 | vb->tell_host_first |
Rusty Russell | c45a681 | 2008-05-02 21:50:50 -0500 | [diff] [blame] | 230 | = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); |
Rusty Russell | 6b35e40 | 2008-02-04 23:50:12 -0500 | [diff] [blame] | 231 | |
| 232 | return 0; |
| 233 | |
| 234 | out_del_deflate_vq: |
| 235 | vdev->config->del_vq(vb->deflate_vq); |
| 236 | out_del_inflate_vq: |
| 237 | vdev->config->del_vq(vb->inflate_vq); |
| 238 | out_free_vb: |
| 239 | kfree(vb); |
| 240 | out: |
| 241 | return err; |
| 242 | } |
| 243 | |
| 244 | static void virtballoon_remove(struct virtio_device *vdev) |
| 245 | { |
| 246 | struct virtio_balloon *vb = vdev->priv; |
| 247 | |
| 248 | kthread_stop(vb->thread); |
| 249 | |
| 250 | /* There might be pages left in the balloon: free them. */ |
| 251 | while (vb->num_pages) |
| 252 | leak_balloon(vb, vb->num_pages); |
| 253 | |
| 254 | /* Now we reset the device so we can clean up the queues. */ |
| 255 | vdev->config->reset(vdev); |
| 256 | |
| 257 | vdev->config->del_vq(vb->deflate_vq); |
| 258 | vdev->config->del_vq(vb->inflate_vq); |
| 259 | kfree(vb); |
| 260 | } |
| 261 | |
Rusty Russell | c45a681 | 2008-05-02 21:50:50 -0500 | [diff] [blame] | 262 | static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST }; |
| 263 | |
Rusty Russell | 6b35e40 | 2008-02-04 23:50:12 -0500 | [diff] [blame] | 264 | static struct virtio_driver virtio_balloon = { |
Rusty Russell | c45a681 | 2008-05-02 21:50:50 -0500 | [diff] [blame] | 265 | .feature_table = features, |
| 266 | .feature_table_size = ARRAY_SIZE(features), |
Rusty Russell | 6b35e40 | 2008-02-04 23:50:12 -0500 | [diff] [blame] | 267 | .driver.name = KBUILD_MODNAME, |
| 268 | .driver.owner = THIS_MODULE, |
| 269 | .id_table = id_table, |
| 270 | .probe = virtballoon_probe, |
| 271 | .remove = __devexit_p(virtballoon_remove), |
| 272 | .config_changed = virtballoon_changed, |
| 273 | }; |
| 274 | |
| 275 | static int __init init(void) |
| 276 | { |
| 277 | return register_virtio_driver(&virtio_balloon); |
| 278 | } |
| 279 | |
| 280 | static void __exit fini(void) |
| 281 | { |
| 282 | unregister_virtio_driver(&virtio_balloon); |
| 283 | } |
| 284 | module_init(init); |
| 285 | module_exit(fini); |
| 286 | |
| 287 | MODULE_DEVICE_TABLE(virtio, id_table); |
| 288 | MODULE_DESCRIPTION("Virtio balloon driver"); |
| 289 | MODULE_LICENSE("GPL"); |