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> 26 #include <linux/delay.h> 27 28 struct virtio_balloon 29 { 30 struct virtio_device *vdev; 31 struct virtqueue *inflate_vq, *deflate_vq, *stats_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 /* Memory statistics */ 54 int need_stats_update; 55 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; 56 }; 57 58 static struct virtio_device_id id_table[] = { 59 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 60 { 0 }, 61 }; 62 63 static u32 page_to_balloon_pfn(struct page *page) 64 { 65 unsigned long pfn = page_to_pfn(page); 66 67 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 68 /* Convert pfn from Linux page size to balloon page size. */ 69 return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT); 70 } 71 72 static void balloon_ack(struct virtqueue *vq) 73 { 74 struct virtio_balloon *vb; 75 unsigned int len; 76 77 vb = vq->vq_ops->get_buf(vq, &len); 78 if (vb) 79 complete(&vb->acked); 80 } 81 82 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 83 { 84 struct scatterlist sg; 85 86 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 87 88 init_completion(&vb->acked); 89 90 /* We should always be able to add one buffer to an empty queue. */ 91 if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0) 92 BUG(); 93 vq->vq_ops->kick(vq); 94 95 /* When host has read buffer, this completes via balloon_ack */ 96 wait_for_completion(&vb->acked); 97 } 98 99 static void fill_balloon(struct virtio_balloon *vb, size_t num) 100 { 101 /* We can only do one array worth at a time. */ 102 num = min(num, ARRAY_SIZE(vb->pfns)); 103 104 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 105 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY); 106 if (!page) { 107 if (printk_ratelimit()) 108 dev_printk(KERN_INFO, &vb->vdev->dev, 109 "Out of puff! Can't get %zu pages\n", 110 num); 111 /* Sleep for at least 1/5 of a second before retry. */ 112 msleep(200); 113 break; 114 } 115 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); 116 totalram_pages--; 117 vb->num_pages++; 118 list_add(&page->lru, &vb->pages); 119 } 120 121 /* Didn't get any? Oh well. */ 122 if (vb->num_pfns == 0) 123 return; 124 125 tell_host(vb, vb->inflate_vq); 126 } 127 128 static void release_pages_by_pfn(const u32 pfns[], unsigned int num) 129 { 130 unsigned int i; 131 132 for (i = 0; i < num; i++) { 133 __free_page(pfn_to_page(pfns[i])); 134 totalram_pages++; 135 } 136 } 137 138 static void leak_balloon(struct virtio_balloon *vb, size_t num) 139 { 140 struct page *page; 141 142 /* We can only do one array worth at a time. */ 143 num = min(num, ARRAY_SIZE(vb->pfns)); 144 145 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 146 page = list_first_entry(&vb->pages, struct page, lru); 147 list_del(&page->lru); 148 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); 149 vb->num_pages--; 150 } 151 152 if (vb->tell_host_first) { 153 tell_host(vb, vb->deflate_vq); 154 release_pages_by_pfn(vb->pfns, vb->num_pfns); 155 } else { 156 release_pages_by_pfn(vb->pfns, vb->num_pfns); 157 tell_host(vb, vb->deflate_vq); 158 } 159 } 160 161 static inline void update_stat(struct virtio_balloon *vb, int idx, 162 u16 tag, u64 val) 163 { 164 BUG_ON(idx >= VIRTIO_BALLOON_S_NR); 165 vb->stats[idx].tag = tag; 166 vb->stats[idx].val = val; 167 } 168 169 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) 170 171 static void update_balloon_stats(struct virtio_balloon *vb) 172 { 173 unsigned long events[NR_VM_EVENT_ITEMS]; 174 struct sysinfo i; 175 int idx = 0; 176 177 all_vm_events(events); 178 si_meminfo(&i); 179 180 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, 181 pages_to_bytes(events[PSWPIN])); 182 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, 183 pages_to_bytes(events[PSWPOUT])); 184 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); 185 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); 186 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, 187 pages_to_bytes(i.freeram)); 188 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, 189 pages_to_bytes(i.totalram)); 190 } 191 192 /* 193 * While most virtqueues communicate guest-initiated requests to the hypervisor, 194 * the stats queue operates in reverse. The driver initializes the virtqueue 195 * with a single buffer. From that point forward, all conversations consist of 196 * a hypervisor request (a call to this function) which directs us to refill 197 * the virtqueue with a fresh stats buffer. Since stats collection can sleep, 198 * we notify our kthread which does the actual work via stats_handle_request(). 199 */ 200 static void stats_request(struct virtqueue *vq) 201 { 202 struct virtio_balloon *vb; 203 unsigned int len; 204 205 vb = vq->vq_ops->get_buf(vq, &len); 206 if (!vb) 207 return; 208 vb->need_stats_update = 1; 209 wake_up(&vb->config_change); 210 } 211 212 static void stats_handle_request(struct virtio_balloon *vb) 213 { 214 struct virtqueue *vq; 215 struct scatterlist sg; 216 217 vb->need_stats_update = 0; 218 update_balloon_stats(vb); 219 220 vq = vb->stats_vq; 221 sg_init_one(&sg, vb->stats, sizeof(vb->stats)); 222 if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0) 223 BUG(); 224 vq->vq_ops->kick(vq); 225 } 226 227 static void virtballoon_changed(struct virtio_device *vdev) 228 { 229 struct virtio_balloon *vb = vdev->priv; 230 231 wake_up(&vb->config_change); 232 } 233 234 static inline s64 towards_target(struct virtio_balloon *vb) 235 { 236 u32 v; 237 vb->vdev->config->get(vb->vdev, 238 offsetof(struct virtio_balloon_config, num_pages), 239 &v, sizeof(v)); 240 return (s64)v - vb->num_pages; 241 } 242 243 static void update_balloon_size(struct virtio_balloon *vb) 244 { 245 __le32 actual = cpu_to_le32(vb->num_pages); 246 247 vb->vdev->config->set(vb->vdev, 248 offsetof(struct virtio_balloon_config, actual), 249 &actual, sizeof(actual)); 250 } 251 252 static int balloon(void *_vballoon) 253 { 254 struct virtio_balloon *vb = _vballoon; 255 256 set_freezable(); 257 while (!kthread_should_stop()) { 258 s64 diff; 259 260 try_to_freeze(); 261 wait_event_interruptible(vb->config_change, 262 (diff = towards_target(vb)) != 0 263 || vb->need_stats_update 264 || kthread_should_stop() 265 || freezing(current)); 266 if (vb->need_stats_update) 267 stats_handle_request(vb); 268 if (diff > 0) 269 fill_balloon(vb, diff); 270 else if (diff < 0) 271 leak_balloon(vb, -diff); 272 update_balloon_size(vb); 273 } 274 return 0; 275 } 276 277 static int virtballoon_probe(struct virtio_device *vdev) 278 { 279 struct virtio_balloon *vb; 280 struct virtqueue *vqs[3]; 281 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request }; 282 const char *names[] = { "inflate", "deflate", "stats" }; 283 int err, nvqs; 284 285 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); 286 if (!vb) { 287 err = -ENOMEM; 288 goto out; 289 } 290 291 INIT_LIST_HEAD(&vb->pages); 292 vb->num_pages = 0; 293 init_waitqueue_head(&vb->config_change); 294 vb->vdev = vdev; 295 vb->need_stats_update = 0; 296 297 /* We expect two virtqueues: inflate and deflate, 298 * and optionally stat. */ 299 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2; 300 err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names); 301 if (err) 302 goto out_free_vb; 303 304 vb->inflate_vq = vqs[0]; 305 vb->deflate_vq = vqs[1]; 306 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 307 struct scatterlist sg; 308 vb->stats_vq = vqs[2]; 309 310 /* 311 * Prime this virtqueue with one buffer so the hypervisor can 312 * use it to signal us later. 313 */ 314 sg_init_one(&sg, vb->stats, sizeof vb->stats); 315 if (vb->stats_vq->vq_ops->add_buf(vb->stats_vq, 316 &sg, 1, 0, vb) < 0) 317 BUG(); 318 vb->stats_vq->vq_ops->kick(vb->stats_vq); 319 } 320 321 vb->thread = kthread_run(balloon, vb, "vballoon"); 322 if (IS_ERR(vb->thread)) { 323 err = PTR_ERR(vb->thread); 324 goto out_del_vqs; 325 } 326 327 vb->tell_host_first 328 = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 329 330 return 0; 331 332 out_del_vqs: 333 vdev->config->del_vqs(vdev); 334 out_free_vb: 335 kfree(vb); 336 out: 337 return err; 338 } 339 340 static void __devexit virtballoon_remove(struct virtio_device *vdev) 341 { 342 struct virtio_balloon *vb = vdev->priv; 343 344 kthread_stop(vb->thread); 345 346 /* There might be pages left in the balloon: free them. */ 347 while (vb->num_pages) 348 leak_balloon(vb, vb->num_pages); 349 350 /* Now we reset the device so we can clean up the queues. */ 351 vdev->config->reset(vdev); 352 353 vdev->config->del_vqs(vdev); 354 kfree(vb); 355 } 356 357 static unsigned int features[] = { 358 VIRTIO_BALLOON_F_MUST_TELL_HOST, 359 VIRTIO_BALLOON_F_STATS_VQ, 360 }; 361 362 static struct virtio_driver virtio_balloon_driver = { 363 .feature_table = features, 364 .feature_table_size = ARRAY_SIZE(features), 365 .driver.name = KBUILD_MODNAME, 366 .driver.owner = THIS_MODULE, 367 .id_table = id_table, 368 .probe = virtballoon_probe, 369 .remove = __devexit_p(virtballoon_remove), 370 .config_changed = virtballoon_changed, 371 }; 372 373 static int __init init(void) 374 { 375 return register_virtio_driver(&virtio_balloon_driver); 376 } 377 378 static void __exit fini(void) 379 { 380 unregister_virtio_driver(&virtio_balloon_driver); 381 } 382 module_init(init); 383 module_exit(fini); 384 385 MODULE_DEVICE_TABLE(virtio, id_table); 386 MODULE_DESCRIPTION("Virtio balloon driver"); 387 MODULE_LICENSE("GPL"); 388