1 /****************************************************************************** 2 * balloon.c 3 * 4 * Xen balloon driver - enables returning/claiming memory to/from Xen. 5 * 6 * Copyright (c) 2003, B Dragovic 7 * Copyright (c) 2003-2004, M Williamson, K Fraser 8 * Copyright (c) 2005 Dan M. Smith, IBM Corporation 9 * 10 * This file may be distributed separately from the Linux kernel, or 11 * incorporated into other software packages, subject to the following license: 12 * 13 * Permission is hereby granted, free of charge, to any person obtaining a copy 14 * of this source file (the "Software"), to deal in the Software without 15 * restriction, including without limitation the rights to use, copy, modify, 16 * merge, publish, distribute, sublicense, and/or sell copies of the Software, 17 * and to permit persons to whom the Software is furnished to do so, subject to 18 * the following conditions: 19 * 20 * The above copyright notice and this permission notice shall be included in 21 * all copies or substantial portions of the Software. 22 * 23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 24 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 25 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 26 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 27 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 28 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 29 * IN THE SOFTWARE. 30 */ 31 32 #include <sys/cdefs.h> 33 #include <sys/param.h> 34 #include <sys/lock.h> 35 #include <sys/kernel.h> 36 #include <sys/kthread.h> 37 #include <sys/malloc.h> 38 #include <sys/mutex.h> 39 #include <sys/sysctl.h> 40 #include <sys/module.h> 41 42 #include <vm/vm.h> 43 #include <vm/vm_page.h> 44 45 #include <xen/xen-os.h> 46 #include <xen/hypervisor.h> 47 #include <xen/features.h> 48 #include <xen/xenstore/xenstorevar.h> 49 50 static MALLOC_DEFINE(M_BALLOON, "Balloon", "Xen Balloon Driver"); 51 52 /* Convert from KB (as fetched from xenstore) to number of PAGES */ 53 #define KB_TO_PAGE_SHIFT (PAGE_SHIFT - 10) 54 55 struct mtx balloon_mutex; 56 57 /* We increase/decrease in batches which fit in a page */ 58 static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)]; 59 60 struct balloon_stats { 61 /* We aim for 'current allocation' == 'target allocation'. */ 62 unsigned long current_pages; 63 unsigned long target_pages; 64 /* We may hit the hard limit in Xen. If we do then we remember it. */ 65 unsigned long hard_limit; 66 /* 67 * Drivers may alter the memory reservation independently, but they 68 * must inform the balloon driver so we avoid hitting the hard limit. 69 */ 70 unsigned long driver_pages; 71 /* Number of pages in high- and low-memory balloons. */ 72 unsigned long balloon_low; 73 unsigned long balloon_high; 74 }; 75 76 static struct balloon_stats balloon_stats; 77 #define bs balloon_stats 78 79 SYSCTL_DECL(_dev_xen); 80 static SYSCTL_NODE(_dev_xen, OID_AUTO, balloon, 81 CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 82 "Balloon"); 83 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, current, CTLFLAG_RD, 84 &bs.current_pages, 0, "Current allocation"); 85 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, target, CTLFLAG_RD, 86 &bs.target_pages, 0, "Target allocation"); 87 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, driver_pages, CTLFLAG_RD, 88 &bs.driver_pages, 0, "Driver pages"); 89 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, hard_limit, CTLFLAG_RD, 90 &bs.hard_limit, 0, "Xen hard limit"); 91 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, low_mem, CTLFLAG_RD, 92 &bs.balloon_low, 0, "Low-mem balloon"); 93 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, high_mem, CTLFLAG_RD, 94 &bs.balloon_high, 0, "High-mem balloon"); 95 96 /* List of ballooned pages, threaded through the mem_map array. */ 97 static TAILQ_HEAD(,vm_page) ballooned_pages; 98 99 /* Main work function, always executed in process context. */ 100 static void balloon_process(void *unused); 101 102 #define IPRINTK(fmt, args...) \ 103 printk(KERN_INFO "xen_mem: " fmt, ##args) 104 #define WPRINTK(fmt, args...) \ 105 printk(KERN_WARNING "xen_mem: " fmt, ##args) 106 107 static unsigned long 108 current_target(void) 109 { 110 unsigned long target = min(bs.target_pages, bs.hard_limit); 111 if (target > (bs.current_pages + bs.balloon_low + bs.balloon_high)) 112 target = bs.current_pages + bs.balloon_low + bs.balloon_high; 113 return (target); 114 } 115 116 static unsigned long 117 minimum_target(void) 118 { 119 unsigned long min_pages, curr_pages = current_target(); 120 121 #define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT)) 122 /* 123 * Simple continuous piecewiese linear function: 124 * max MiB -> min MiB gradient 125 * 0 0 126 * 16 16 127 * 32 24 128 * 128 72 (1/2) 129 * 512 168 (1/4) 130 * 2048 360 (1/8) 131 * 8192 552 (1/32) 132 * 32768 1320 133 * 131072 4392 134 */ 135 if (realmem < MB2PAGES(128)) 136 min_pages = MB2PAGES(8) + (realmem >> 1); 137 else if (realmem < MB2PAGES(512)) 138 min_pages = MB2PAGES(40) + (realmem >> 2); 139 else if (realmem < MB2PAGES(2048)) 140 min_pages = MB2PAGES(104) + (realmem >> 3); 141 else 142 min_pages = MB2PAGES(296) + (realmem >> 5); 143 #undef MB2PAGES 144 145 /* Don't enforce growth */ 146 return (min(min_pages, curr_pages)); 147 } 148 149 static int 150 increase_reservation(unsigned long nr_pages) 151 { 152 unsigned long i; 153 vm_page_t page; 154 long rc; 155 struct xen_memory_reservation reservation = { 156 .extent_order = 0, 157 .domid = DOMID_SELF 158 }; 159 160 mtx_assert(&balloon_mutex, MA_OWNED); 161 162 if (nr_pages > nitems(frame_list)) 163 nr_pages = nitems(frame_list); 164 165 for (page = TAILQ_FIRST(&ballooned_pages), i = 0; 166 i < nr_pages; i++, page = TAILQ_NEXT(page, plinks.q)) { 167 KASSERT(page != NULL, ("ballooned_pages list corrupt")); 168 frame_list[i] = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); 169 } 170 171 set_xen_guest_handle(reservation.extent_start, frame_list); 172 reservation.nr_extents = nr_pages; 173 rc = HYPERVISOR_memory_op( 174 XENMEM_populate_physmap, &reservation); 175 if (rc < nr_pages) { 176 if (rc > 0) { 177 int ret __diagused; 178 179 /* We hit the Xen hard limit: reprobe. */ 180 reservation.nr_extents = rc; 181 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, 182 &reservation); 183 KASSERT(ret == rc, ("HYPERVISOR_memory_op failed")); 184 } 185 if (rc >= 0) 186 bs.hard_limit = (bs.current_pages + rc - 187 bs.driver_pages); 188 goto out; 189 } 190 191 for (i = 0; i < nr_pages; i++) { 192 page = TAILQ_FIRST(&ballooned_pages); 193 KASSERT(page != NULL, ("Unable to get ballooned page")); 194 TAILQ_REMOVE(&ballooned_pages, page, plinks.q); 195 bs.balloon_low--; 196 197 KASSERT(xen_feature(XENFEAT_auto_translated_physmap), 198 ("auto translated physmap but mapping is valid")); 199 200 vm_page_free(page); 201 } 202 203 bs.current_pages += nr_pages; 204 205 out: 206 return (0); 207 } 208 209 static int 210 decrease_reservation(unsigned long nr_pages) 211 { 212 unsigned long i; 213 vm_page_t page; 214 int need_sleep = 0; 215 int ret __diagused; 216 struct xen_memory_reservation reservation = { 217 .extent_order = 0, 218 .domid = DOMID_SELF 219 }; 220 221 mtx_assert(&balloon_mutex, MA_OWNED); 222 223 if (nr_pages > nitems(frame_list)) 224 nr_pages = nitems(frame_list); 225 226 for (i = 0; i < nr_pages; i++) { 227 /* 228 * Zero the page, or else we might be leaking important data to 229 * other domains on the same host. Xen doesn't scrub ballooned 230 * out memory pages, the guest is in charge of making sure that 231 * no information is leaked. 232 */ 233 if ((page = vm_page_alloc_noobj(VM_ALLOC_ZERO)) == NULL) { 234 nr_pages = i; 235 need_sleep = 1; 236 break; 237 } 238 239 frame_list[i] = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); 240 241 TAILQ_INSERT_HEAD(&ballooned_pages, page, plinks.q); 242 bs.balloon_low++; 243 } 244 245 set_xen_guest_handle(reservation.extent_start, frame_list); 246 reservation.nr_extents = nr_pages; 247 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); 248 KASSERT(ret == nr_pages, ("HYPERVISOR_memory_op failed")); 249 250 bs.current_pages -= nr_pages; 251 252 return (need_sleep); 253 } 254 255 /* 256 * We avoid multiple worker processes conflicting via the balloon mutex. 257 * We may of course race updates of the target counts (which are protected 258 * by the balloon lock), or with changes to the Xen hard limit, but we will 259 * recover from these in time. 260 */ 261 static void 262 balloon_process(void *unused) 263 { 264 int need_sleep = 0; 265 long credit; 266 267 mtx_lock(&balloon_mutex); 268 for (;;) { 269 int sleep_time; 270 271 do { 272 credit = current_target() - bs.current_pages; 273 if (credit > 0) 274 need_sleep = (increase_reservation(credit) != 0); 275 if (credit < 0) 276 need_sleep = (decrease_reservation(-credit) != 0); 277 278 } while ((credit != 0) && !need_sleep); 279 280 /* Schedule more work if there is some still to be done. */ 281 if (current_target() != bs.current_pages) 282 sleep_time = hz; 283 else 284 sleep_time = 0; 285 286 msleep(balloon_process, &balloon_mutex, 0, "balloon", 287 sleep_time); 288 } 289 mtx_unlock(&balloon_mutex); 290 } 291 292 /* Resets the Xen limit, sets new target, and kicks off processing. */ 293 static void 294 set_new_target(unsigned long target) 295 { 296 /* No need for lock. Not read-modify-write updates. */ 297 bs.hard_limit = ~0UL; 298 bs.target_pages = max(target, minimum_target()); 299 wakeup(balloon_process); 300 } 301 302 static struct xs_watch target_watch = 303 { 304 .node = "memory/target", 305 .max_pending = 1, 306 }; 307 308 /* React to a change in the target key */ 309 static void 310 watch_target(struct xs_watch *watch, 311 const char **vec, unsigned int len) 312 { 313 unsigned long long new_target; 314 int err; 315 316 err = xs_scanf(XST_NIL, "memory", "target", NULL, 317 "%llu", &new_target); 318 if (err) { 319 /* This is ok (for domain0 at least) - so just return */ 320 return; 321 } 322 323 /* 324 * The given memory/target value is in KiB, so it needs converting to 325 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10. 326 */ 327 set_new_target(new_target >> KB_TO_PAGE_SHIFT); 328 } 329 330 /*------------------ Private Device Attachment Functions --------------------*/ 331 /** 332 * \brief Identify instances of this device type in the system. 333 * 334 * \param driver The driver performing this identify action. 335 * \param parent The NewBus parent device for any devices this method adds. 336 */ 337 static void 338 xenballoon_identify(driver_t *driver __unused, device_t parent) 339 { 340 /* 341 * A single device instance for our driver is always present 342 * in a system operating under Xen. 343 */ 344 BUS_ADD_CHILD(parent, 0, driver->name, 0); 345 } 346 347 /** 348 * \brief Probe for the existence of the Xen Balloon device 349 * 350 * \param dev NewBus device_t for this Xen control instance. 351 * 352 * \return Always returns 0 indicating success. 353 */ 354 static int 355 xenballoon_probe(device_t dev) 356 { 357 358 device_set_desc(dev, "Xen Balloon Device"); 359 return (0); 360 } 361 362 /** 363 * \brief Attach the Xen Balloon device. 364 * 365 * \param dev NewBus device_t for this Xen control instance. 366 * 367 * \return On success, 0. Otherwise an errno value indicating the 368 * type of failure. 369 */ 370 static int 371 xenballoon_attach(device_t dev) 372 { 373 int err; 374 375 mtx_init(&balloon_mutex, "balloon_mutex", NULL, MTX_DEF); 376 377 bs.current_pages = realmem; 378 bs.target_pages = bs.current_pages; 379 bs.balloon_low = 0; 380 bs.balloon_high = 0; 381 bs.driver_pages = 0UL; 382 bs.hard_limit = ~0UL; 383 384 kproc_create(balloon_process, NULL, NULL, 0, 0, "balloon"); 385 386 target_watch.callback = watch_target; 387 388 err = xs_register_watch(&target_watch); 389 if (err) 390 device_printf(dev, 391 "xenballon: failed to set balloon watcher\n"); 392 393 return (err); 394 } 395 396 /*-------------------- Private Device Attachment Data -----------------------*/ 397 static device_method_t xenballoon_methods[] = { 398 /* Device interface */ 399 DEVMETHOD(device_identify, xenballoon_identify), 400 DEVMETHOD(device_probe, xenballoon_probe), 401 DEVMETHOD(device_attach, xenballoon_attach), 402 403 DEVMETHOD_END 404 }; 405 406 DEFINE_CLASS_0(xenballoon, xenballoon_driver, xenballoon_methods, 0); 407 408 DRIVER_MODULE(xenballoon, xenstore, xenballoon_driver, NULL, NULL); 409