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 29struct virtio_balloon 30{ 31 struct virtio_device *vdev; 32 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq; 33 34 /* Where the ballooning thread waits for config to change. */ 35 wait_queue_head_t config_change; 36 37 /* The thread servicing the balloon. */ 38 struct task_struct *thread; 39 40 /* Waiting for host to ack the pages we released. */ 41 struct completion acked; 42 43 /* Do we have to tell Host *before* we reuse pages? */ 44 bool tell_host_first; 45 46 /* The pages we've told the Host we're not using. */ 47 unsigned int num_pages; 48 struct list_head pages; 49 50 /* The array of pfns we tell the Host about. */ 51 unsigned int num_pfns; 52 u32 pfns[256]; 53 54 /* Memory statistics */ 55 int need_stats_update; 56 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; 57}; 58 59static struct virtio_device_id id_table[] = { 60 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 61 { 0 }, 62}; 63 64static u32 page_to_balloon_pfn(struct page *page) 65{ 66 unsigned long pfn = page_to_pfn(page); 67 68 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 69 /* Convert pfn from Linux page size to balloon page size. */ 70 return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT); 71} 72 73static void balloon_ack(struct virtqueue *vq) 74{ 75 struct virtio_balloon *vb; 76 unsigned int len; 77 78 vb = virtqueue_get_buf(vq, &len); 79 if (vb) 80 complete(&vb->acked); 81} 82 83static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 84{ 85 struct scatterlist sg; 86 87 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 88 89 init_completion(&vb->acked); 90 91 /* We should always be able to add one buffer to an empty queue. */ 92 if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0) 93 BUG(); 94 virtqueue_kick(vq); 95 96 /* When host has read buffer, this completes via balloon_ack */ 97 wait_for_completion(&vb->acked); 98} 99 100static void fill_balloon(struct virtio_balloon *vb, size_t num) 101{ 102 /* We can only do one array worth at a time. */ 103 num = min(num, ARRAY_SIZE(vb->pfns)); 104 105 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 106 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY | 107 __GFP_NOMEMALLOC | __GFP_NOWARN); 108 if (!page) { 109 if (printk_ratelimit()) 110 dev_printk(KERN_INFO, &vb->vdev->dev, 111 "Out of puff! Can't get %zu pages\n", 112 num); 113 /* Sleep for at least 1/5 of a second before retry. */ 114 msleep(200); 115 break; 116 } 117 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); 118 totalram_pages--; 119 vb->num_pages++; 120 list_add(&page->lru, &vb->pages); 121 } 122 123 /* Didn't get any? Oh well. */ 124 if (vb->num_pfns == 0) 125 return; 126 127 tell_host(vb, vb->inflate_vq); 128} 129 130static void release_pages_by_pfn(const u32 pfns[], unsigned int num) 131{ 132 unsigned int i; 133 134 for (i = 0; i < num; i++) { 135 __free_page(pfn_to_page(pfns[i])); 136 totalram_pages++; 137 } 138} 139 140static void leak_balloon(struct virtio_balloon *vb, size_t num) 141{ 142 struct page *page; 143 144 /* We can only do one array worth at a time. */ 145 num = min(num, ARRAY_SIZE(vb->pfns)); 146 147 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 148 page = list_first_entry(&vb->pages, struct page, lru); 149 list_del(&page->lru); 150 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); 151 vb->num_pages--; 152 } 153 154 if (vb->tell_host_first) { 155 tell_host(vb, vb->deflate_vq); 156 release_pages_by_pfn(vb->pfns, vb->num_pfns); 157 } else { 158 release_pages_by_pfn(vb->pfns, vb->num_pfns); 159 tell_host(vb, vb->deflate_vq); 160 } 161} 162 163static inline void update_stat(struct virtio_balloon *vb, int idx, 164 u16 tag, u64 val) 165{ 166 BUG_ON(idx >= VIRTIO_BALLOON_S_NR); 167 vb->stats[idx].tag = tag; 168 vb->stats[idx].val = val; 169} 170 171#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) 172 173static void update_balloon_stats(struct virtio_balloon *vb) 174{ 175 unsigned long events[NR_VM_EVENT_ITEMS]; 176 struct sysinfo i; 177 int idx = 0; 178 179 all_vm_events(events); 180 si_meminfo(&i); 181 182 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, 183 pages_to_bytes(events[PSWPIN])); 184 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, 185 pages_to_bytes(events[PSWPOUT])); 186 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); 187 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); 188 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, 189 pages_to_bytes(i.freeram)); 190 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, 191 pages_to_bytes(i.totalram)); 192} 193 194/* 195 * While most virtqueues communicate guest-initiated requests to the hypervisor, 196 * the stats queue operates in reverse. The driver initializes the virtqueue 197 * with a single buffer. From that point forward, all conversations consist of 198 * a hypervisor request (a call to this function) which directs us to refill 199 * the virtqueue with a fresh stats buffer. Since stats collection can sleep, 200 * we notify our kthread which does the actual work via stats_handle_request(). 201 */ 202static void stats_request(struct virtqueue *vq) 203{ 204 struct virtio_balloon *vb; 205 unsigned int len; 206 207 vb = virtqueue_get_buf(vq, &len); 208 if (!vb) 209 return; 210 vb->need_stats_update = 1; 211 wake_up(&vb->config_change); 212} 213 214static void stats_handle_request(struct virtio_balloon *vb) 215{ 216 struct virtqueue *vq; 217 struct scatterlist sg; 218 219 vb->need_stats_update = 0; 220 update_balloon_stats(vb); 221 222 vq = vb->stats_vq; 223 sg_init_one(&sg, vb->stats, sizeof(vb->stats)); 224 if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0) 225 BUG(); 226 virtqueue_kick(vq); 227} 228 229static void virtballoon_changed(struct virtio_device *vdev) 230{ 231 struct virtio_balloon *vb = vdev->priv; 232 233 wake_up(&vb->config_change); 234} 235 236static inline s64 towards_target(struct virtio_balloon *vb) 237{ 238 u32 v; 239 vb->vdev->config->get(vb->vdev, 240 offsetof(struct virtio_balloon_config, num_pages), 241 &v, sizeof(v)); 242 return (s64)v - vb->num_pages; 243} 244 245static void update_balloon_size(struct virtio_balloon *vb) 246{ 247 __le32 actual = cpu_to_le32(vb->num_pages); 248 249 vb->vdev->config->set(vb->vdev, 250 offsetof(struct virtio_balloon_config, actual), 251 &actual, sizeof(actual)); 252} 253 254static int balloon(void *_vballoon) 255{ 256 struct virtio_balloon *vb = _vballoon; 257 258 set_freezable(); 259 while (!kthread_should_stop()) { 260 s64 diff; 261 262 try_to_freeze(); 263 wait_event_interruptible(vb->config_change, 264 (diff = towards_target(vb)) != 0 265 || vb->need_stats_update 266 || kthread_should_stop() 267 || freezing(current)); 268 if (vb->need_stats_update) 269 stats_handle_request(vb); 270 if (diff > 0) 271 fill_balloon(vb, diff); 272 else if (diff < 0) 273 leak_balloon(vb, -diff); 274 update_balloon_size(vb); 275 } 276 return 0; 277} 278 279static int virtballoon_probe(struct virtio_device *vdev) 280{ 281 struct virtio_balloon *vb; 282 struct virtqueue *vqs[3]; 283 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request }; 284 const char *names[] = { "inflate", "deflate", "stats" }; 285 int err, nvqs; 286 287 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); 288 if (!vb) { 289 err = -ENOMEM; 290 goto out; 291 } 292 293 INIT_LIST_HEAD(&vb->pages); 294 vb->num_pages = 0; 295 init_waitqueue_head(&vb->config_change); 296 vb->vdev = vdev; 297 vb->need_stats_update = 0; 298 299 /* We expect two virtqueues: inflate and deflate, 300 * and optionally stat. */ 301 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2; 302 err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names); 303 if (err) 304 goto out_free_vb; 305 306 vb->inflate_vq = vqs[0]; 307 vb->deflate_vq = vqs[1]; 308 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 309 struct scatterlist sg; 310 vb->stats_vq = vqs[2]; 311 312 /* 313 * Prime this virtqueue with one buffer so the hypervisor can 314 * use it to signal us later. 315 */ 316 sg_init_one(&sg, vb->stats, sizeof vb->stats); 317 if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb) < 0) 318 BUG(); 319 virtqueue_kick(vb->stats_vq); 320 } 321 322 vb->thread = kthread_run(balloon, vb, "vballoon"); 323 if (IS_ERR(vb->thread)) { 324 err = PTR_ERR(vb->thread); 325 goto out_del_vqs; 326 } 327 328 vb->tell_host_first 329 = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 330 331 return 0; 332 333out_del_vqs: 334 vdev->config->del_vqs(vdev); 335out_free_vb: 336 kfree(vb); 337out: 338 return err; 339} 340 341static void __devexit virtballoon_remove(struct virtio_device *vdev) 342{ 343 struct virtio_balloon *vb = vdev->priv; 344 345 kthread_stop(vb->thread); 346 347 /* There might be pages left in the balloon: free them. */ 348 while (vb->num_pages) 349 leak_balloon(vb, vb->num_pages); 350 351 /* Now we reset the device so we can clean up the queues. */ 352 vdev->config->reset(vdev); 353 354 vdev->config->del_vqs(vdev); 355 kfree(vb); 356} 357 358static unsigned int features[] = { 359 VIRTIO_BALLOON_F_MUST_TELL_HOST, 360 VIRTIO_BALLOON_F_STATS_VQ, 361}; 362 363static struct virtio_driver virtio_balloon_driver = { 364 .feature_table = features, 365 .feature_table_size = ARRAY_SIZE(features), 366 .driver.name = KBUILD_MODNAME, 367 .driver.owner = THIS_MODULE, 368 .id_table = id_table, 369 .probe = virtballoon_probe, 370 .remove = __devexit_p(virtballoon_remove), 371 .config_changed = virtballoon_changed, 372}; 373 374static int __init init(void) 375{ 376 return register_virtio_driver(&virtio_balloon_driver); 377} 378 379static void __exit fini(void) 380{ 381 unregister_virtio_driver(&virtio_balloon_driver); 382} 383module_init(init); 384module_exit(fini); 385 386MODULE_DEVICE_TABLE(virtio, id_table); 387MODULE_DESCRIPTION("Virtio balloon driver"); 388MODULE_LICENSE("GPL"); 389