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 __FBSDID("$FreeBSD$"); 34 35 #include <sys/param.h> 36 #include <sys/lock.h> 37 #include <sys/kernel.h> 38 #include <sys/kthread.h> 39 #include <sys/malloc.h> 40 #include <sys/mutex.h> 41 #include <sys/sysctl.h> 42 #include <sys/module.h> 43 44 #include <vm/vm.h> 45 #include <vm/vm_page.h> 46 47 #include <xen/xen-os.h> 48 #include <xen/hypervisor.h> 49 #include <xen/features.h> 50 #include <xen/xenstore/xenstorevar.h> 51 52 static MALLOC_DEFINE(M_BALLOON, "Balloon", "Xen Balloon Driver"); 53 54 /* Convert from KB (as fetched from xenstore) to number of PAGES */ 55 #define KB_TO_PAGE_SHIFT (PAGE_SHIFT - 10) 56 57 struct mtx balloon_mutex; 58 59 /* We increase/decrease in batches which fit in a page */ 60 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)]; 61 62 struct balloon_stats { 63 /* We aim for 'current allocation' == 'target allocation'. */ 64 unsigned long current_pages; 65 unsigned long target_pages; 66 /* We may hit the hard limit in Xen. If we do then we remember it. */ 67 unsigned long hard_limit; 68 /* 69 * Drivers may alter the memory reservation independently, but they 70 * must inform the balloon driver so we avoid hitting the hard limit. 71 */ 72 unsigned long driver_pages; 73 /* Number of pages in high- and low-memory balloons. */ 74 unsigned long balloon_low; 75 unsigned long balloon_high; 76 }; 77 78 static struct balloon_stats balloon_stats; 79 #define bs balloon_stats 80 81 SYSCTL_DECL(_dev_xen); 82 static SYSCTL_NODE(_dev_xen, OID_AUTO, balloon, CTLFLAG_RD, NULL, "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 pfn, i; 153 vm_page_t page; 154 long rc; 155 struct xen_memory_reservation reservation = { 156 .address_bits = 0, 157 .extent_order = 0, 158 .domid = DOMID_SELF 159 }; 160 161 mtx_assert(&balloon_mutex, MA_OWNED); 162 163 if (nr_pages > nitems(frame_list)) 164 nr_pages = nitems(frame_list); 165 166 for (page = TAILQ_FIRST(&ballooned_pages), i = 0; 167 i < nr_pages; i++, page = TAILQ_NEXT(page, plinks.q)) { 168 KASSERT(page != NULL, ("ballooned_pages list corrupt")); 169 frame_list[i] = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); 170 } 171 172 set_xen_guest_handle(reservation.extent_start, frame_list); 173 reservation.nr_extents = nr_pages; 174 rc = HYPERVISOR_memory_op( 175 XENMEM_populate_physmap, &reservation); 176 if (rc < nr_pages) { 177 if (rc > 0) { 178 int ret; 179 180 /* We hit the Xen hard limit: reprobe. */ 181 reservation.nr_extents = rc; 182 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, 183 &reservation); 184 KASSERT(ret == rc, ("HYPERVISOR_memory_op failed")); 185 } 186 if (rc >= 0) 187 bs.hard_limit = (bs.current_pages + rc - 188 bs.driver_pages); 189 goto out; 190 } 191 192 for (i = 0; i < nr_pages; i++) { 193 page = TAILQ_FIRST(&ballooned_pages); 194 KASSERT(page != NULL, ("Unable to get ballooned page")); 195 TAILQ_REMOVE(&ballooned_pages, page, plinks.q); 196 bs.balloon_low--; 197 198 pfn = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); 199 KASSERT(xen_feature(XENFEAT_auto_translated_physmap), 200 ("auto translated physmap but mapping is valid")); 201 202 vm_page_free(page); 203 } 204 205 bs.current_pages += nr_pages; 206 207 out: 208 return (0); 209 } 210 211 static int 212 decrease_reservation(unsigned long nr_pages) 213 { 214 unsigned long pfn, i; 215 vm_page_t page; 216 int need_sleep = 0; 217 int ret; 218 struct xen_memory_reservation reservation = { 219 .address_bits = 0, 220 .extent_order = 0, 221 .domid = DOMID_SELF 222 }; 223 224 mtx_assert(&balloon_mutex, MA_OWNED); 225 226 if (nr_pages > nitems(frame_list)) 227 nr_pages = nitems(frame_list); 228 229 for (i = 0; i < nr_pages; i++) { 230 if ((page = vm_page_alloc(NULL, 0, 231 VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ | 232 VM_ALLOC_ZERO)) == NULL) { 233 nr_pages = i; 234 need_sleep = 1; 235 break; 236 } 237 238 if ((page->flags & PG_ZERO) == 0) { 239 /* 240 * Zero the page, or else we might be leaking 241 * important data to other domains on the same 242 * host. Xen doesn't scrub ballooned out memory 243 * pages, the guest is in charge of making 244 * sure that no information is leaked. 245 */ 246 pmap_zero_page(page); 247 } 248 249 pfn = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); 250 frame_list[i] = pfn; 251 252 TAILQ_INSERT_HEAD(&ballooned_pages, page, plinks.q); 253 bs.balloon_low++; 254 } 255 256 set_xen_guest_handle(reservation.extent_start, frame_list); 257 reservation.nr_extents = nr_pages; 258 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); 259 KASSERT(ret == nr_pages, ("HYPERVISOR_memory_op failed")); 260 261 bs.current_pages -= nr_pages; 262 263 return (need_sleep); 264 } 265 266 /* 267 * We avoid multiple worker processes conflicting via the balloon mutex. 268 * We may of course race updates of the target counts (which are protected 269 * by the balloon lock), or with changes to the Xen hard limit, but we will 270 * recover from these in time. 271 */ 272 static void 273 balloon_process(void *unused) 274 { 275 int need_sleep = 0; 276 long credit; 277 278 mtx_lock(&balloon_mutex); 279 for (;;) { 280 int sleep_time; 281 282 do { 283 credit = current_target() - bs.current_pages; 284 if (credit > 0) 285 need_sleep = (increase_reservation(credit) != 0); 286 if (credit < 0) 287 need_sleep = (decrease_reservation(-credit) != 0); 288 289 } while ((credit != 0) && !need_sleep); 290 291 /* Schedule more work if there is some still to be done. */ 292 if (current_target() != bs.current_pages) 293 sleep_time = hz; 294 else 295 sleep_time = 0; 296 297 msleep(balloon_process, &balloon_mutex, 0, "balloon", 298 sleep_time); 299 } 300 mtx_unlock(&balloon_mutex); 301 } 302 303 /* Resets the Xen limit, sets new target, and kicks off processing. */ 304 static void 305 set_new_target(unsigned long target) 306 { 307 /* No need for lock. Not read-modify-write updates. */ 308 bs.hard_limit = ~0UL; 309 bs.target_pages = max(target, minimum_target()); 310 wakeup(balloon_process); 311 } 312 313 static struct xs_watch target_watch = 314 { 315 .node = "memory/target" 316 }; 317 318 /* React to a change in the target key */ 319 static void 320 watch_target(struct xs_watch *watch, 321 const char **vec, unsigned int len) 322 { 323 unsigned long long new_target; 324 int err; 325 326 err = xs_scanf(XST_NIL, "memory", "target", NULL, 327 "%llu", &new_target); 328 if (err) { 329 /* This is ok (for domain0 at least) - so just return */ 330 return; 331 } 332 333 /* 334 * The given memory/target value is in KiB, so it needs converting to 335 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10. 336 */ 337 set_new_target(new_target >> KB_TO_PAGE_SHIFT); 338 } 339 340 /*------------------ Private Device Attachment Functions --------------------*/ 341 /** 342 * \brief Identify instances of this device type in the system. 343 * 344 * \param driver The driver performing this identify action. 345 * \param parent The NewBus parent device for any devices this method adds. 346 */ 347 static void 348 xenballoon_identify(driver_t *driver __unused, device_t parent) 349 { 350 /* 351 * A single device instance for our driver is always present 352 * in a system operating under Xen. 353 */ 354 BUS_ADD_CHILD(parent, 0, driver->name, 0); 355 } 356 357 /** 358 * \brief Probe for the existance of the Xen Balloon device 359 * 360 * \param dev NewBus device_t for this Xen control instance. 361 * 362 * \return Always returns 0 indicating success. 363 */ 364 static int 365 xenballoon_probe(device_t dev) 366 { 367 368 device_set_desc(dev, "Xen Balloon Device"); 369 return (0); 370 } 371 372 /** 373 * \brief Attach the Xen Balloon device. 374 * 375 * \param dev NewBus device_t for this Xen control instance. 376 * 377 * \return On success, 0. Otherwise an errno value indicating the 378 * type of failure. 379 */ 380 static int 381 xenballoon_attach(device_t dev) 382 { 383 int err; 384 385 mtx_init(&balloon_mutex, "balloon_mutex", NULL, MTX_DEF); 386 387 bs.current_pages = xen_pv_domain() ? 388 HYPERVISOR_start_info->nr_pages : realmem; 389 bs.target_pages = bs.current_pages; 390 bs.balloon_low = 0; 391 bs.balloon_high = 0; 392 bs.driver_pages = 0UL; 393 bs.hard_limit = ~0UL; 394 395 kproc_create(balloon_process, NULL, NULL, 0, 0, "balloon"); 396 397 target_watch.callback = watch_target; 398 399 err = xs_register_watch(&target_watch); 400 if (err) 401 device_printf(dev, 402 "xenballon: failed to set balloon watcher\n"); 403 404 return (err); 405 } 406 407 /*-------------------- Private Device Attachment Data -----------------------*/ 408 static device_method_t xenballoon_methods[] = { 409 /* Device interface */ 410 DEVMETHOD(device_identify, xenballoon_identify), 411 DEVMETHOD(device_probe, xenballoon_probe), 412 DEVMETHOD(device_attach, xenballoon_attach), 413 414 DEVMETHOD_END 415 }; 416 417 DEFINE_CLASS_0(xenballoon, xenballoon_driver, xenballoon_methods, 0); 418 devclass_t xenballoon_devclass; 419 420 DRIVER_MODULE(xenballoon, xenstore, xenballoon_driver, xenballoon_devclass, 421 NULL, NULL); 422