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; 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 u32 page_to_balloon_pfn(struct page *page) 60 { 61 unsigned long pfn = page_to_pfn(page); 62 63 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 64 /* Convert pfn from Linux page size to balloon page size. */ 65 return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT); 66 } 67 68 static void balloon_ack(struct virtqueue *vq) 69 { 70 struct virtio_balloon *vb; 71 unsigned int len; 72 73 vb = vq->vq_ops->get_buf(vq, &len); 74 if (vb) 75 complete(&vb->acked); 76 } 77 78 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 79 { 80 struct scatterlist sg; 81 82 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 83 84 init_completion(&vb->acked); 85 86 /* We should always be able to add one buffer to an empty queue. */ 87 if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0) 88 BUG(); 89 vq->vq_ops->kick(vq); 90 91 /* When host has read buffer, this completes via balloon_ack */ 92 wait_for_completion(&vb->acked); 93 } 94 95 static void fill_balloon(struct virtio_balloon *vb, size_t num) 96 { 97 /* We can only do one array worth at a time. */ 98 num = min(num, ARRAY_SIZE(vb->pfns)); 99 100 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 101 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY); 102 if (!page) { 103 if (printk_ratelimit()) 104 dev_printk(KERN_INFO, &vb->vdev->dev, 105 "Out of puff! Can't get %zu pages\n", 106 num); 107 /* Sleep for at least 1/5 of a second before retry. */ 108 msleep(200); 109 break; 110 } 111 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); 112 totalram_pages--; 113 vb->num_pages++; 114 list_add(&page->lru, &vb->pages); 115 } 116 117 /* Didn't get any? Oh well. */ 118 if (vb->num_pfns == 0) 119 return; 120 121 tell_host(vb, vb->inflate_vq); 122 } 123 124 static void release_pages_by_pfn(const u32 pfns[], unsigned int num) 125 { 126 unsigned int i; 127 128 for (i = 0; i < num; i++) { 129 __free_page(pfn_to_page(pfns[i])); 130 totalram_pages++; 131 } 132 } 133 134 static void leak_balloon(struct virtio_balloon *vb, size_t num) 135 { 136 struct page *page; 137 138 /* We can only do one array worth at a time. */ 139 num = min(num, ARRAY_SIZE(vb->pfns)); 140 141 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 142 page = list_first_entry(&vb->pages, struct page, lru); 143 list_del(&page->lru); 144 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); 145 vb->num_pages--; 146 } 147 148 if (vb->tell_host_first) { 149 tell_host(vb, vb->deflate_vq); 150 release_pages_by_pfn(vb->pfns, vb->num_pfns); 151 } else { 152 release_pages_by_pfn(vb->pfns, vb->num_pfns); 153 tell_host(vb, vb->deflate_vq); 154 } 155 } 156 157 static void virtballoon_changed(struct virtio_device *vdev) 158 { 159 struct virtio_balloon *vb = vdev->priv; 160 161 wake_up(&vb->config_change); 162 } 163 164 static inline s64 towards_target(struct virtio_balloon *vb) 165 { 166 u32 v; 167 vb->vdev->config->get(vb->vdev, 168 offsetof(struct virtio_balloon_config, num_pages), 169 &v, sizeof(v)); 170 return (s64)v - vb->num_pages; 171 } 172 173 static void update_balloon_size(struct virtio_balloon *vb) 174 { 175 __le32 actual = cpu_to_le32(vb->num_pages); 176 177 vb->vdev->config->set(vb->vdev, 178 offsetof(struct virtio_balloon_config, actual), 179 &actual, sizeof(actual)); 180 } 181 182 static int balloon(void *_vballoon) 183 { 184 struct virtio_balloon *vb = _vballoon; 185 186 set_freezable(); 187 while (!kthread_should_stop()) { 188 s64 diff; 189 190 try_to_freeze(); 191 wait_event_interruptible(vb->config_change, 192 (diff = towards_target(vb)) != 0 193 || kthread_should_stop() 194 || freezing(current)); 195 if (diff > 0) 196 fill_balloon(vb, diff); 197 else if (diff < 0) 198 leak_balloon(vb, -diff); 199 update_balloon_size(vb); 200 } 201 return 0; 202 } 203 204 static int virtballoon_probe(struct virtio_device *vdev) 205 { 206 struct virtio_balloon *vb; 207 struct virtqueue *vqs[2]; 208 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack }; 209 const char *names[] = { "inflate", "deflate" }; 210 int err; 211 212 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); 213 if (!vb) { 214 err = -ENOMEM; 215 goto out; 216 } 217 218 INIT_LIST_HEAD(&vb->pages); 219 vb->num_pages = 0; 220 init_waitqueue_head(&vb->config_change); 221 vb->vdev = vdev; 222 223 /* We expect two virtqueues. */ 224 err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names); 225 if (err) 226 goto out_free_vb; 227 228 vb->inflate_vq = vqs[0]; 229 vb->deflate_vq = vqs[1]; 230 231 vb->thread = kthread_run(balloon, vb, "vballoon"); 232 if (IS_ERR(vb->thread)) { 233 err = PTR_ERR(vb->thread); 234 goto out_del_vqs; 235 } 236 237 vb->tell_host_first 238 = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 239 240 return 0; 241 242 out_del_vqs: 243 vdev->config->del_vqs(vdev); 244 out_free_vb: 245 kfree(vb); 246 out: 247 return err; 248 } 249 250 static void virtballoon_remove(struct virtio_device *vdev) 251 { 252 struct virtio_balloon *vb = vdev->priv; 253 254 kthread_stop(vb->thread); 255 256 /* There might be pages left in the balloon: free them. */ 257 while (vb->num_pages) 258 leak_balloon(vb, vb->num_pages); 259 260 /* Now we reset the device so we can clean up the queues. */ 261 vdev->config->reset(vdev); 262 263 vdev->config->del_vqs(vdev); 264 kfree(vb); 265 } 266 267 static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST }; 268 269 static struct virtio_driver virtio_balloon = { 270 .feature_table = features, 271 .feature_table_size = ARRAY_SIZE(features), 272 .driver.name = KBUILD_MODNAME, 273 .driver.owner = THIS_MODULE, 274 .id_table = id_table, 275 .probe = virtballoon_probe, 276 .remove = __devexit_p(virtballoon_remove), 277 .config_changed = virtballoon_changed, 278 }; 279 280 static int __init init(void) 281 { 282 return register_virtio_driver(&virtio_balloon); 283 } 284 285 static void __exit fini(void) 286 { 287 unregister_virtio_driver(&virtio_balloon); 288 } 289 module_init(init); 290 module_exit(fini); 291 292 MODULE_DEVICE_TABLE(virtio, id_table); 293 MODULE_DESCRIPTION("Virtio balloon driver"); 294 MODULE_LICENSE("GPL"); 295