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 #include <linux/slab.h> 28 #include <linux/module.h> 29 30 struct virtio_balloon 31 { 32 struct virtio_device *vdev; 33 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq; 34 35 /* Where the ballooning thread waits for config to change. */ 36 wait_queue_head_t config_change; 37 38 /* The thread servicing the balloon. */ 39 struct task_struct *thread; 40 41 /* Waiting for host to ack the pages we released. */ 42 struct completion acked; 43 44 /* The pages we've told the Host we're not using. */ 45 unsigned int num_pages; 46 struct list_head pages; 47 48 /* The array of pfns we tell the Host about. */ 49 unsigned int num_pfns; 50 u32 pfns[256]; 51 52 /* Memory statistics */ 53 int need_stats_update; 54 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; 55 }; 56 57 static struct virtio_device_id id_table[] = { 58 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 59 { 0 }, 60 }; 61 62 static u32 page_to_balloon_pfn(struct page *page) 63 { 64 unsigned long pfn = page_to_pfn(page); 65 66 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 67 /* Convert pfn from Linux page size to balloon page size. */ 68 return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT); 69 } 70 71 static void balloon_ack(struct virtqueue *vq) 72 { 73 struct virtio_balloon *vb; 74 unsigned int len; 75 76 vb = virtqueue_get_buf(vq, &len); 77 if (vb) 78 complete(&vb->acked); 79 } 80 81 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 82 { 83 struct scatterlist sg; 84 85 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 86 87 init_completion(&vb->acked); 88 89 /* We should always be able to add one buffer to an empty queue. */ 90 if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0) 91 BUG(); 92 virtqueue_kick(vq); 93 94 /* When host has read buffer, this completes via balloon_ack */ 95 wait_for_completion(&vb->acked); 96 } 97 98 static void fill_balloon(struct virtio_balloon *vb, size_t num) 99 { 100 /* We can only do one array worth at a time. */ 101 num = min(num, ARRAY_SIZE(vb->pfns)); 102 103 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 104 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY | 105 __GFP_NOMEMALLOC | __GFP_NOWARN); 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 } 151 152 153 /* 154 * Note that if 155 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 156 * is true, we *have* to do it in this order 157 */ 158 tell_host(vb, vb->deflate_vq); 159 release_pages_by_pfn(vb->pfns, vb->num_pfns); 160 } 161 162 static inline void update_stat(struct virtio_balloon *vb, int idx, 163 u16 tag, u64 val) 164 { 165 BUG_ON(idx >= VIRTIO_BALLOON_S_NR); 166 vb->stats[idx].tag = tag; 167 vb->stats[idx].val = val; 168 } 169 170 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) 171 172 static void update_balloon_stats(struct virtio_balloon *vb) 173 { 174 unsigned long events[NR_VM_EVENT_ITEMS]; 175 struct sysinfo i; 176 int idx = 0; 177 178 all_vm_events(events); 179 si_meminfo(&i); 180 181 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, 182 pages_to_bytes(events[PSWPIN])); 183 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, 184 pages_to_bytes(events[PSWPOUT])); 185 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); 186 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); 187 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, 188 pages_to_bytes(i.freeram)); 189 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, 190 pages_to_bytes(i.totalram)); 191 } 192 193 /* 194 * While most virtqueues communicate guest-initiated requests to the hypervisor, 195 * the stats queue operates in reverse. The driver initializes the virtqueue 196 * with a single buffer. From that point forward, all conversations consist of 197 * a hypervisor request (a call to this function) which directs us to refill 198 * the virtqueue with a fresh stats buffer. Since stats collection can sleep, 199 * we notify our kthread which does the actual work via stats_handle_request(). 200 */ 201 static void stats_request(struct virtqueue *vq) 202 { 203 struct virtio_balloon *vb; 204 unsigned int len; 205 206 vb = virtqueue_get_buf(vq, &len); 207 if (!vb) 208 return; 209 vb->need_stats_update = 1; 210 wake_up(&vb->config_change); 211 } 212 213 static void stats_handle_request(struct virtio_balloon *vb) 214 { 215 struct virtqueue *vq; 216 struct scatterlist sg; 217 218 vb->need_stats_update = 0; 219 update_balloon_stats(vb); 220 221 vq = vb->stats_vq; 222 sg_init_one(&sg, vb->stats, sizeof(vb->stats)); 223 if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0) 224 BUG(); 225 virtqueue_kick(vq); 226 } 227 228 static void virtballoon_changed(struct virtio_device *vdev) 229 { 230 struct virtio_balloon *vb = vdev->priv; 231 232 wake_up(&vb->config_change); 233 } 234 235 static inline s64 towards_target(struct virtio_balloon *vb) 236 { 237 u32 v; 238 vb->vdev->config->get(vb->vdev, 239 offsetof(struct virtio_balloon_config, num_pages), 240 &v, sizeof(v)); 241 return (s64)v - vb->num_pages; 242 } 243 244 static void update_balloon_size(struct virtio_balloon *vb) 245 { 246 __le32 actual = cpu_to_le32(vb->num_pages); 247 248 vb->vdev->config->set(vb->vdev, 249 offsetof(struct virtio_balloon_config, actual), 250 &actual, sizeof(actual)); 251 } 252 253 static int balloon(void *_vballoon) 254 { 255 struct virtio_balloon *vb = _vballoon; 256 257 set_freezable(); 258 while (!kthread_should_stop()) { 259 s64 diff; 260 261 try_to_freeze(); 262 wait_event_interruptible(vb->config_change, 263 (diff = towards_target(vb)) != 0 264 || vb->need_stats_update 265 || kthread_should_stop() 266 || freezing(current)); 267 if (vb->need_stats_update) 268 stats_handle_request(vb); 269 if (diff > 0) 270 fill_balloon(vb, diff); 271 else if (diff < 0) 272 leak_balloon(vb, -diff); 273 update_balloon_size(vb); 274 } 275 return 0; 276 } 277 278 static int virtballoon_probe(struct virtio_device *vdev) 279 { 280 struct virtio_balloon *vb; 281 struct virtqueue *vqs[3]; 282 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request }; 283 const char *names[] = { "inflate", "deflate", "stats" }; 284 int err, nvqs; 285 286 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); 287 if (!vb) { 288 err = -ENOMEM; 289 goto out; 290 } 291 292 INIT_LIST_HEAD(&vb->pages); 293 vb->num_pages = 0; 294 init_waitqueue_head(&vb->config_change); 295 vb->vdev = vdev; 296 vb->need_stats_update = 0; 297 298 /* We expect two virtqueues: inflate and deflate, 299 * and optionally stat. */ 300 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2; 301 err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names); 302 if (err) 303 goto out_free_vb; 304 305 vb->inflate_vq = vqs[0]; 306 vb->deflate_vq = vqs[1]; 307 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 308 struct scatterlist sg; 309 vb->stats_vq = vqs[2]; 310 311 /* 312 * Prime this virtqueue with one buffer so the hypervisor can 313 * use it to signal us later. 314 */ 315 sg_init_one(&sg, vb->stats, sizeof vb->stats); 316 if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb) < 0) 317 BUG(); 318 virtqueue_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 return 0; 328 329 out_del_vqs: 330 vdev->config->del_vqs(vdev); 331 out_free_vb: 332 kfree(vb); 333 out: 334 return err; 335 } 336 337 static void __devexit virtballoon_remove(struct virtio_device *vdev) 338 { 339 struct virtio_balloon *vb = vdev->priv; 340 341 kthread_stop(vb->thread); 342 343 /* There might be pages left in the balloon: free them. */ 344 while (vb->num_pages) 345 leak_balloon(vb, vb->num_pages); 346 347 /* Now we reset the device so we can clean up the queues. */ 348 vdev->config->reset(vdev); 349 350 vdev->config->del_vqs(vdev); 351 kfree(vb); 352 } 353 354 static unsigned int features[] = { 355 VIRTIO_BALLOON_F_MUST_TELL_HOST, 356 VIRTIO_BALLOON_F_STATS_VQ, 357 }; 358 359 static struct virtio_driver virtio_balloon_driver = { 360 .feature_table = features, 361 .feature_table_size = ARRAY_SIZE(features), 362 .driver.name = KBUILD_MODNAME, 363 .driver.owner = THIS_MODULE, 364 .id_table = id_table, 365 .probe = virtballoon_probe, 366 .remove = __devexit_p(virtballoon_remove), 367 .config_changed = virtballoon_changed, 368 }; 369 370 static int __init init(void) 371 { 372 return register_virtio_driver(&virtio_balloon_driver); 373 } 374 375 static void __exit fini(void) 376 { 377 unregister_virtio_driver(&virtio_balloon_driver); 378 } 379 module_init(init); 380 module_exit(fini); 381 382 MODULE_DEVICE_TABLE(virtio, id_table); 383 MODULE_DESCRIPTION("Virtio balloon driver"); 384 MODULE_LICENSE("GPL"); 385