1 | /* $NetBSD: balloon.c,v 1.17 2016/07/07 06:55:40 msaitoh Exp $ */ |
2 | |
3 | /*- |
4 | * Copyright (c) 2010 The NetBSD Foundation, Inc. |
5 | * All rights reserved. |
6 | * |
7 | * This code is derived from software contributed to The NetBSD Foundation |
8 | * by Cherry G. Mathew <cherry@zyx.in> and |
9 | * Jean-Yves Migeon <jym@NetBSD.org> |
10 | * |
11 | * Redistribution and use in source and binary forms, with or without |
12 | * modification, are permitted provided that the following conditions |
13 | * are met: |
14 | * 1. Redistributions of source code must retain the above copyright |
15 | * notice, this list of conditions and the following disclaimer. |
16 | * 2. Redistributions in binary form must reproduce the above copyright |
17 | * notice, this list of conditions and the following disclaimer in the |
18 | * documentation and/or other materials provided with the distribution. |
19 | * |
20 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
21 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
22 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
23 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
24 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
25 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
26 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
27 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
28 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
29 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
30 | * POSSIBILITY OF SUCH DAMAGE. |
31 | */ |
32 | |
33 | /* |
34 | * The Xen balloon driver enables growing and shrinking PV domains |
35 | * memory on the fly, by allocating and freeing memory pages directly. |
36 | * This management needs domain cooperation to work properly, especially |
37 | * during balloon_inflate() operation where a domain gives back memory to |
38 | * the hypervisor. |
39 | * |
40 | * Shrinking memory on a live system is a difficult task, and may render |
41 | * it unstable or lead to crash. The driver takes a conservative approach |
42 | * there by doing memory operations in smal steps of a few MiB each time. It |
43 | * will also refuse to decrease reservation below a certain threshold |
44 | * (XEN_RESERVATION_MIN), so as to avoid a complete kernel memory exhaustion. |
45 | * |
46 | * The user can intervene at two different levels to manage the ballooning |
47 | * of a domain: |
48 | * - directly within the domain using a sysctl(9) interface. |
49 | * - through the Xentools, by modifying the memory/target entry associated |
50 | * to a domain. This is usually done in dom0. |
51 | * |
52 | * Modification of the reservation is signaled by writing inside the |
53 | * memory/target node in Xenstore. Writing new values will fire the xenbus |
54 | * watcher, and wakeup the balloon thread to inflate or deflate balloon. |
55 | * |
56 | * Both sysctl(9) nodes and memory/target entry assume that the values passed |
57 | * to them are in KiB. Internally, the driver will convert this value in |
58 | * pages (assuming a page is PAGE_SIZE bytes), and issue the correct hypercalls |
59 | * to decrease/increase domain's reservation accordingly. |
60 | * |
61 | * XXX Pages used by balloon are tracked through entries stored in a SLIST. |
62 | * This allows driver to conveniently add/remove wired pages from memory |
63 | * without the need to support these "memory gaps" inside uvm(9). Still, the |
64 | * driver does not currently "plug" new pages into uvm(9) when more memory |
65 | * is available than originally managed by balloon. For example, deflating |
66 | * balloon with a total number of pages above physmem is not supported for |
67 | * now. See balloon_deflate() for more details. |
68 | * |
69 | */ |
70 | |
71 | #define BALLOONDEBUG 0 |
72 | |
73 | #include <sys/cdefs.h> |
74 | __KERNEL_RCSID(0, "$NetBSD: balloon.c,v 1.17 2016/07/07 06:55:40 msaitoh Exp $" ); |
75 | |
76 | #include <sys/inttypes.h> |
77 | #include <sys/device.h> |
78 | #include <sys/param.h> |
79 | |
80 | #include <sys/atomic.h> |
81 | #include <sys/condvar.h> |
82 | #include <sys/kernel.h> |
83 | #include <sys/kmem.h> |
84 | #include <sys/kthread.h> |
85 | #include <sys/mutex.h> |
86 | #include <sys/pool.h> |
87 | #include <sys/queue.h> |
88 | #include <sys/sysctl.h> |
89 | |
90 | #include <xen/xen.h> |
91 | #include <xen/xenbus.h> |
92 | #include <xen/balloon.h> |
93 | |
94 | #include <uvm/uvm.h> |
95 | #include <uvm/uvm.h> |
96 | #include <xen/xenpmap.h> |
97 | |
98 | #include "locators.h" |
99 | |
100 | /* |
101 | * Number of MFNs stored in the array passed back and forth between domain |
102 | * and balloon/hypervisor, during balloon_inflate() / balloon_deflate(). These |
103 | * should fit in a page, for performance reasons. |
104 | */ |
105 | #define BALLOON_DELTA (PAGE_SIZE / sizeof(xen_pfn_t)) |
106 | |
107 | /* |
108 | * Safeguard value. Refuse to go below this threshold, so that domain |
109 | * can keep some free pages for its own use. Value is arbitrary, and may |
110 | * evolve with time. |
111 | */ |
112 | #define BALLOON_BALLAST 256 /* In pages - 1MiB */ |
113 | #define XEN_RESERVATION_MIN (uvmexp.freemin + BALLOON_BALLAST) /* In pages */ |
114 | |
115 | /* KB <-> PAGEs */ |
116 | #define PAGE_SIZE_KB (PAGE_SIZE >> 10) /* page size in KB */ |
117 | #define BALLOON_PAGES_TO_KB(_pg) ((uint64_t)_pg * PAGE_SIZE_KB) |
118 | #define BALLOON_KB_TO_PAGES(_kb) (roundup(_kb, PAGE_SIZE_KB) / PAGE_SIZE_KB) |
119 | |
120 | /* |
121 | * A balloon page entry. Needed to track pages put/reclaimed from balloon |
122 | */ |
123 | struct balloon_page_entry { |
124 | struct vm_page *pg; |
125 | SLIST_ENTRY(balloon_page_entry) entry; |
126 | }; |
127 | |
128 | struct balloon_xenbus_softc { |
129 | device_t sc_dev; |
130 | struct sysctllog *sc_log; |
131 | |
132 | kmutex_t balloon_mtx; /* Protects condvar, target and res_min (below) */ |
133 | kcondvar_t balloon_cv; /* Condvar variable for target (below) */ |
134 | size_t balloon_target; /* Target domain reservation size in pages. */ |
135 | /* Minimum amount of memory reserved by domain, in KiB */ |
136 | uint64_t balloon_res_min; |
137 | |
138 | xen_pfn_t *sc_mfn_list; /* List of MFNs passed from/to balloon */ |
139 | pool_cache_t bpge_pool; /* pool cache for balloon page entries */ |
140 | /* linked list for tracking pages used by balloon */ |
141 | SLIST_HEAD(, balloon_page_entry) balloon_page_entries; |
142 | size_t balloon_num_page_entries; |
143 | }; |
144 | |
145 | static size_t xenmem_get_currentreservation(void); |
146 | static size_t xenmem_get_maxreservation(void); |
147 | |
148 | static int bpge_ctor(void *, void *, int); |
149 | static void bpge_dtor(void *, void *); |
150 | |
151 | static void balloon_thread(void *); |
152 | static size_t balloon_deflate(struct balloon_xenbus_softc*, size_t); |
153 | static size_t balloon_inflate(struct balloon_xenbus_softc*, size_t); |
154 | |
155 | static void sysctl_kern_xen_balloon_setup(struct balloon_xenbus_softc *); |
156 | static void balloon_xenbus_watcher(struct xenbus_watch *, const char **, |
157 | unsigned int); |
158 | |
159 | static int balloon_xenbus_match(device_t, cfdata_t, void *); |
160 | static void balloon_xenbus_attach(device_t, device_t, void *); |
161 | |
162 | CFATTACH_DECL_NEW(balloon, sizeof(struct balloon_xenbus_softc), |
163 | balloon_xenbus_match, balloon_xenbus_attach, NULL, NULL); |
164 | |
165 | static struct xenbus_watch balloon_xenbus_watch = { |
166 | .node = __UNCONST("memory/target" ), |
167 | .xbw_callback = balloon_xenbus_watcher, |
168 | }; |
169 | |
170 | static struct balloon_xenbus_softc *balloon_sc; |
171 | |
172 | static int |
173 | balloon_xenbus_match(device_t parent, cfdata_t match, void *aux) |
174 | { |
175 | struct xenbusdev_attach_args *xa = aux; |
176 | |
177 | if (strcmp(xa->xa_type, "balloon" ) != 0) |
178 | return 0; |
179 | |
180 | if (match->cf_loc[XENBUSCF_ID] != XENBUSCF_ID_DEFAULT && |
181 | match->cf_loc[XENBUSCF_ID] != xa->xa_id) |
182 | return 0; |
183 | |
184 | return 1; |
185 | } |
186 | |
187 | static void |
188 | balloon_xenbus_attach(device_t parent, device_t self, void *aux) |
189 | { |
190 | xen_pfn_t *mfn_list; |
191 | size_t currentpages; |
192 | struct balloon_xenbus_softc *sc = balloon_sc = device_private(self); |
193 | |
194 | aprint_normal(": Xen Balloon driver\n" ); |
195 | sc->sc_dev = self; |
196 | |
197 | /* Initialize target mutex and condvar */ |
198 | mutex_init(&sc->balloon_mtx, MUTEX_DEFAULT, IPL_NONE); |
199 | cv_init(&sc->balloon_cv, "xen_balloon" ); |
200 | |
201 | SLIST_INIT(&sc->balloon_page_entries); |
202 | sc->balloon_num_page_entries = 0; |
203 | |
204 | /* Get current number of pages */ |
205 | currentpages = xenmem_get_currentreservation(); |
206 | |
207 | KASSERT(currentpages > 0); |
208 | |
209 | /* Update initial target value - no need to lock for initialization */ |
210 | sc->balloon_target = currentpages; |
211 | |
212 | /* Set the values used by sysctl */ |
213 | sc->balloon_res_min = |
214 | BALLOON_PAGES_TO_KB(XEN_RESERVATION_MIN); |
215 | |
216 | aprint_normal_dev(self, "current reservation: %" PRIu64" KiB\n" , |
217 | BALLOON_PAGES_TO_KB(currentpages)); |
218 | #if BALLOONDEBUG |
219 | aprint_normal_dev(self, "min reservation: %" PRIu64" KiB\n" , |
220 | sc->balloon_res_min); |
221 | aprint_normal_dev(self, "max reservation: %" PRIu64" KiB\n" , |
222 | BALLOON_PAGES_TO_KB(xenmem_get_maxreservation())); |
223 | #endif |
224 | |
225 | sc->bpge_pool = pool_cache_init(sizeof(struct balloon_page_entry), |
226 | 0, 0, 0, "xen_bpge" , NULL, IPL_NONE, bpge_ctor, bpge_dtor, NULL); |
227 | |
228 | sysctl_kern_xen_balloon_setup(sc); |
229 | |
230 | /* List of MFNs passed from/to balloon for inflating/deflating */ |
231 | mfn_list = kmem_alloc(BALLOON_DELTA * sizeof(*mfn_list), KM_SLEEP); |
232 | sc->sc_mfn_list = mfn_list; |
233 | |
234 | /* Setup xenbus node watch callback */ |
235 | if (register_xenbus_watch(&balloon_xenbus_watch)) { |
236 | aprint_error_dev(self, "unable to watch memory/target\n" ); |
237 | goto error; |
238 | } |
239 | |
240 | /* Setup kernel thread to asynchronously (in/de)-flate the balloon */ |
241 | if (kthread_create(PRI_NONE, KTHREAD_MPSAFE, NULL, balloon_thread, |
242 | sc, NULL, "xen_balloon" )) { |
243 | aprint_error_dev(self, "unable to create balloon thread\n" ); |
244 | unregister_xenbus_watch(&balloon_xenbus_watch); |
245 | goto error; |
246 | } |
247 | |
248 | if (!pmf_device_register(self, NULL, NULL)) |
249 | aprint_error_dev(self, "couldn't establish power handler\n" ); |
250 | |
251 | return; |
252 | |
253 | error: |
254 | sysctl_teardown(&sc->sc_log); |
255 | cv_destroy(&sc->balloon_cv); |
256 | mutex_destroy(&sc->balloon_mtx); |
257 | return; |
258 | |
259 | } |
260 | |
261 | /* |
262 | * Returns maximum memory reservation available to current domain. In Xen |
263 | * with DOMID_SELF, this hypercall never fails: return value should be |
264 | * interpreted as unsigned. |
265 | * |
266 | */ |
267 | static size_t |
268 | xenmem_get_maxreservation(void) |
269 | { |
270 | int s; |
271 | unsigned int ret; |
272 | |
273 | s = splvm(); |
274 | ret = HYPERVISOR_memory_op(XENMEM_maximum_reservation, |
275 | & (domid_t) { DOMID_SELF }); |
276 | |
277 | splx(s); |
278 | |
279 | if (ret == 0) { |
280 | /* well, a maximum reservation of 0 is really bogus */ |
281 | panic("%s failed, maximum reservation returned 0" , __func__); |
282 | } |
283 | |
284 | return ret; |
285 | } |
286 | |
287 | /* Returns current reservation, in pages */ |
288 | static size_t |
289 | xenmem_get_currentreservation(void) |
290 | { |
291 | int s, ret; |
292 | |
293 | s = splvm(); |
294 | ret = HYPERVISOR_memory_op(XENMEM_current_reservation, |
295 | & (domid_t) { DOMID_SELF }); |
296 | splx(s); |
297 | |
298 | if (ret < 0) { |
299 | panic("%s failed: %d" , __func__, ret); |
300 | } |
301 | |
302 | return ret; |
303 | } |
304 | |
305 | /* |
306 | * Get value (in KiB) of memory/target in XenStore for current domain |
307 | * A return value of 0 can be considered as bogus or absent. |
308 | */ |
309 | static unsigned long long |
310 | balloon_xenbus_read_target(void) |
311 | { |
312 | unsigned long long new_target; |
313 | int err = xenbus_read_ull(NULL, "memory" , "target" , &new_target, 0); |
314 | |
315 | switch(err) { |
316 | case 0: |
317 | return new_target; |
318 | case ENOENT: |
319 | break; |
320 | default: |
321 | device_printf(balloon_sc->sc_dev, |
322 | "error %d, couldn't read xenbus target node\n" , err); |
323 | break; |
324 | } |
325 | |
326 | return 0; |
327 | } |
328 | |
329 | /* Set memory/target value (in KiB) in XenStore for current domain */ |
330 | static void |
331 | balloon_xenbus_write_target(unsigned long long new_target) |
332 | { |
333 | int err = xenbus_printf(NULL, "memory" , "target" , "%llu" , new_target); |
334 | |
335 | if (err != 0) { |
336 | device_printf(balloon_sc->sc_dev, |
337 | "error %d, couldn't write xenbus target node\n" , err); |
338 | } |
339 | |
340 | return; |
341 | } |
342 | |
343 | static int |
344 | bpge_ctor(void *arg, void *obj, int flags) |
345 | { |
346 | struct balloon_page_entry *bpge = obj; |
347 | |
348 | bpge->pg = uvm_pagealloc(NULL, 0, NULL, UVM_PGA_ZERO); |
349 | if (bpge->pg == NULL) |
350 | return ENOMEM; |
351 | |
352 | return 0; |
353 | |
354 | } |
355 | |
356 | static void |
357 | bpge_dtor(void *arg, void *obj) |
358 | { |
359 | struct balloon_page_entry *bpge = obj; |
360 | |
361 | uvm_pagefree(bpge->pg); |
362 | } |
363 | |
364 | /* |
365 | * Inflate balloon. Pages are moved out of domain's memory towards balloon. |
366 | */ |
367 | static size_t |
368 | balloon_inflate(struct balloon_xenbus_softc *sc, size_t tpages) |
369 | { |
370 | int rpages, s, ret; |
371 | paddr_t pa; |
372 | struct balloon_page_entry *bpg_entry; |
373 | xen_pfn_t *mfn_list = sc->sc_mfn_list; |
374 | |
375 | struct xen_memory_reservation reservation = { |
376 | .address_bits = 0, |
377 | .extent_order = 0, |
378 | .domid = DOMID_SELF |
379 | }; |
380 | |
381 | KASSERT(tpages > 0); |
382 | KASSERT(tpages <= BALLOON_DELTA); |
383 | |
384 | memset(mfn_list, 0, BALLOON_DELTA * sizeof(*mfn_list)); |
385 | |
386 | /* allocate pages that will be given to Hypervisor */ |
387 | for (rpages = 0; rpages < tpages; rpages++) { |
388 | |
389 | bpg_entry = pool_cache_get(sc->bpge_pool, PR_WAITOK); |
390 | if (bpg_entry == NULL) { |
391 | /* failed reserving a page for balloon */ |
392 | break; |
393 | } |
394 | |
395 | pa = VM_PAGE_TO_PHYS(bpg_entry->pg); |
396 | |
397 | mfn_list[rpages] = xpmap_ptom(pa) >> PAGE_SHIFT; |
398 | |
399 | s = splvm(); |
400 | /* Invalidate pg */ |
401 | xpmap_ptom_unmap(pa); |
402 | splx(s); |
403 | |
404 | SLIST_INSERT_HEAD(&balloon_sc->balloon_page_entries, |
405 | bpg_entry, entry); |
406 | balloon_sc->balloon_num_page_entries++; |
407 | } |
408 | |
409 | /* Hand over pages to Hypervisor */ |
410 | set_xen_guest_handle(reservation.extent_start, mfn_list); |
411 | reservation.nr_extents = rpages; |
412 | |
413 | s = splvm(); |
414 | ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, |
415 | &reservation); |
416 | splx(s); |
417 | |
418 | if (ret != rpages) { |
419 | /* |
420 | * we are in bad shape: the operation failed for certain |
421 | * MFNs. As the API does not allow us to know which frame |
422 | * numbers were erroneous, we cannot really recover safely. |
423 | */ |
424 | panic("%s: decrease reservation failed: was %d, " |
425 | "returned %d" , device_xname(sc->sc_dev), rpages, ret); |
426 | } |
427 | |
428 | #if BALLOONDEBUG |
429 | device_printf(sc->sc_dev, "inflate %zu => inflated by %d\n" , |
430 | tpages, rpages); |
431 | #endif |
432 | return rpages; |
433 | } |
434 | |
435 | /* |
436 | * Deflate balloon. Pages are given back to domain's memory. |
437 | */ |
438 | static size_t |
439 | balloon_deflate(struct balloon_xenbus_softc *sc, size_t tpages) |
440 | { |
441 | int rpages, s, ret; |
442 | paddr_t pa; |
443 | struct balloon_page_entry *bpg_entry; |
444 | xen_pfn_t *mfn_list = sc->sc_mfn_list; |
445 | |
446 | struct xen_memory_reservation reservation = { |
447 | .address_bits = 0, |
448 | .extent_order = 0, |
449 | .domid = DOMID_SELF |
450 | }; |
451 | |
452 | KASSERT(tpages > 0); |
453 | KASSERT(tpages <= BALLOON_DELTA); |
454 | |
455 | memset(mfn_list, 0, BALLOON_DELTA * sizeof(*mfn_list)); |
456 | |
457 | /* |
458 | * If the list is empty, we are deflating balloon beyond empty. This |
459 | * is currently unsupported as this would require to dynamically add |
460 | * new memory pages inside uvm(9) and instruct pmap(9) on how to |
461 | * handle them. For now, we clip reservation up to the point we |
462 | * can manage them, eg. the remaining bpg entries in the SLIST. |
463 | * XXX find a way to hotplug memory through uvm(9)/pmap(9). |
464 | */ |
465 | if (tpages > sc->balloon_num_page_entries) { |
466 | device_printf(sc->sc_dev, |
467 | "memory 'hot-plug' unsupported - clipping " |
468 | "reservation %zu => %zu pages.\n" , |
469 | tpages, sc->balloon_num_page_entries); |
470 | tpages = sc->balloon_num_page_entries; |
471 | } |
472 | |
473 | /* reclaim pages from balloon */ |
474 | set_xen_guest_handle(reservation.extent_start, mfn_list); |
475 | reservation.nr_extents = tpages; |
476 | |
477 | s = splvm(); |
478 | ret = HYPERVISOR_memory_op(XENMEM_increase_reservation, &reservation); |
479 | splx(s); |
480 | |
481 | if (ret < 0) { |
482 | panic("%s: increase reservation failed, ret %d" , |
483 | device_xname(sc->sc_dev), ret); |
484 | } |
485 | |
486 | if (ret != tpages) { |
487 | device_printf(sc->sc_dev, |
488 | "increase reservation incomplete: was %zu, " |
489 | "returned %d\n" , tpages, ret); |
490 | } |
491 | |
492 | /* plug pages back into memory through bpge entries */ |
493 | for (rpages = 0; rpages < ret; rpages++) { |
494 | |
495 | #ifdef noyet |
496 | if (sc->balloon_num_page_entries == 0) { |
497 | /* |
498 | * XXX This is the case where extra "hot-plug" |
499 | * mem w.r.t boot comes in |
500 | */ |
501 | device_printf(sc->sc_dev, |
502 | "List empty. Cannot be collapsed further!\n" ); |
503 | break; |
504 | } |
505 | #endif |
506 | |
507 | bpg_entry = SLIST_FIRST(&balloon_sc->balloon_page_entries); |
508 | SLIST_REMOVE_HEAD(&balloon_sc->balloon_page_entries, entry); |
509 | balloon_sc->balloon_num_page_entries--; |
510 | |
511 | /* Update P->M */ |
512 | pa = VM_PAGE_TO_PHYS(bpg_entry->pg); |
513 | |
514 | s = splvm(); |
515 | |
516 | xpmap_ptom_map(pa, ptoa(mfn_list[rpages])); |
517 | xpq_queue_machphys_update(ptoa(mfn_list[rpages]), pa); |
518 | |
519 | splx(s); |
520 | |
521 | pool_cache_put(sc->bpge_pool, bpg_entry); |
522 | } |
523 | |
524 | xpq_flush_queue(); |
525 | |
526 | #if BALLOONDEBUG |
527 | device_printf(sc->sc_dev, "deflate %zu => deflated by %d\n" , |
528 | tpages, rpages); |
529 | #endif |
530 | return rpages; |
531 | } |
532 | |
533 | /* |
534 | * The balloon thread is responsible for handling inflate/deflate balloon |
535 | * requests for the current domain given the new "target" value. |
536 | */ |
537 | static void |
538 | balloon_thread(void *cookie) |
539 | { |
540 | int ret; |
541 | size_t current, diff, target; |
542 | struct balloon_xenbus_softc *sc = cookie; |
543 | |
544 | for/*ever*/ (;;) { |
545 | current = xenmem_get_currentreservation(); |
546 | |
547 | /* |
548 | * We assume that balloon_xenbus_watcher() and |
549 | * sysctl(9) handlers checked the sanity of the |
550 | * new target value. |
551 | */ |
552 | mutex_enter(&sc->balloon_mtx); |
553 | target = sc->balloon_target; |
554 | if (current != target) { |
555 | /* |
556 | * There is work to do. Inflate/deflate in |
557 | * increments of BALLOON_DELTA pages at maximum. The |
558 | * risk of integer wrapping is mitigated by |
559 | * BALLOON_DELTA, which is the upper bound. |
560 | */ |
561 | mutex_exit(&sc->balloon_mtx); |
562 | diff = MIN(target - current, BALLOON_DELTA); |
563 | if (current < target) |
564 | ret = balloon_deflate(sc, diff); |
565 | else |
566 | ret = balloon_inflate(sc, diff); |
567 | |
568 | if (ret != diff) { |
569 | /* |
570 | * Something went wrong during operation. |
571 | * Log error then feedback current value in |
572 | * target so that thread gets back to waiting |
573 | * for the next iteration |
574 | */ |
575 | device_printf(sc->sc_dev, |
576 | "WARNING: balloon could not reach target " |
577 | "%zu (current %zu)\n" , |
578 | target, current); |
579 | current = xenmem_get_currentreservation(); |
580 | mutex_enter(&sc->balloon_mtx); |
581 | sc->balloon_target = current; |
582 | mutex_exit(&sc->balloon_mtx); |
583 | } |
584 | } else { |
585 | /* no need for change -- wait for a signal */ |
586 | cv_wait(&sc->balloon_cv, &sc->balloon_mtx); |
587 | mutex_exit(&sc->balloon_mtx); |
588 | } |
589 | } |
590 | } |
591 | |
592 | /* |
593 | * Handler called when memory/target value changes inside Xenstore. |
594 | * All sanity checks must also happen in this handler, as it is the common |
595 | * entry point where controller domain schedules balloon operations. |
596 | */ |
597 | static void |
598 | balloon_xenbus_watcher(struct xenbus_watch *watch, const char **vec, |
599 | unsigned int len) |
600 | { |
601 | size_t new_target; |
602 | uint64_t target_kb, target_max, target_min; |
603 | |
604 | target_kb = balloon_xenbus_read_target(); |
605 | if (target_kb == 0) { |
606 | /* bogus -- just return */ |
607 | return; |
608 | } |
609 | |
610 | mutex_enter(&balloon_sc->balloon_mtx); |
611 | target_min = balloon_sc->balloon_res_min; |
612 | mutex_exit(&balloon_sc->balloon_mtx); |
613 | if (target_kb < target_min) { |
614 | device_printf(balloon_sc->sc_dev, |
615 | "new target %" PRIu64" is below min %" PRIu64"\n" , |
616 | target_kb, target_min); |
617 | return; |
618 | } |
619 | |
620 | target_max = BALLOON_PAGES_TO_KB(xenmem_get_maxreservation()); |
621 | if (target_kb > target_max) { |
622 | /* |
623 | * Should not happen. Hypervisor should block balloon |
624 | * requests above mem-max. |
625 | */ |
626 | device_printf(balloon_sc->sc_dev, |
627 | "new target %" PRIu64" is above max %" PRIu64"\n" , |
628 | target_kb, target_max); |
629 | return; |
630 | } |
631 | |
632 | new_target = BALLOON_KB_TO_PAGES(target_kb); |
633 | |
634 | device_printf(balloon_sc->sc_dev, |
635 | "current reservation: %zu pages => target: %zu pages\n" , |
636 | xenmem_get_currentreservation(), new_target); |
637 | |
638 | /* Only update target if its value changes */ |
639 | mutex_enter(&balloon_sc->balloon_mtx); |
640 | if (balloon_sc->balloon_target != new_target) { |
641 | balloon_sc->balloon_target = new_target; |
642 | cv_signal(&balloon_sc->balloon_cv); |
643 | } |
644 | mutex_exit(&balloon_sc->balloon_mtx); |
645 | |
646 | return; |
647 | } |
648 | |
649 | /* |
650 | * sysctl(9) stuff |
651 | */ |
652 | |
653 | /* routine to control the minimum memory reserved for the domain */ |
654 | static int |
655 | sysctl_kern_xen_balloon_min(SYSCTLFN_ARGS) |
656 | { |
657 | struct sysctlnode node; |
658 | u_quad_t newval; |
659 | int error; |
660 | |
661 | node = *rnode; |
662 | node.sysctl_data = &newval; |
663 | |
664 | mutex_enter(&balloon_sc->balloon_mtx); |
665 | newval = balloon_sc->balloon_res_min; |
666 | mutex_exit(&balloon_sc->balloon_mtx); |
667 | |
668 | error = sysctl_lookup(SYSCTLFN_CALL(&node)); |
669 | if (error || newp == NULL) |
670 | return error; |
671 | |
672 | /* Safeguard value: refuse to go below. */ |
673 | if (newval < XEN_RESERVATION_MIN) { |
674 | device_printf(balloon_sc->sc_dev, |
675 | "cannot set min below minimum safe value (%d)\n" , |
676 | XEN_RESERVATION_MIN); |
677 | return EPERM; |
678 | } |
679 | |
680 | mutex_enter(&balloon_sc->balloon_mtx); |
681 | if (balloon_sc->balloon_res_min != newval) |
682 | balloon_sc->balloon_res_min = newval; |
683 | mutex_exit(&balloon_sc->balloon_mtx); |
684 | |
685 | return 0; |
686 | } |
687 | |
688 | /* Returns the maximum memory reservation of the domain */ |
689 | static int |
690 | sysctl_kern_xen_balloon_max(SYSCTLFN_ARGS) |
691 | { |
692 | struct sysctlnode node; |
693 | u_quad_t node_val; |
694 | |
695 | node = *rnode; |
696 | |
697 | node_val = BALLOON_PAGES_TO_KB(xenmem_get_maxreservation()); |
698 | node.sysctl_data = &node_val; |
699 | return sysctl_lookup(SYSCTLFN_CALL(&node)); |
700 | } |
701 | |
702 | /* Returns the current memory reservation of the domain */ |
703 | static int |
704 | sysctl_kern_xen_balloon_current(SYSCTLFN_ARGS) |
705 | { |
706 | struct sysctlnode node; |
707 | u_quad_t node_val; |
708 | |
709 | node = *rnode; |
710 | |
711 | node_val = BALLOON_PAGES_TO_KB(xenmem_get_currentreservation()); |
712 | node.sysctl_data = &node_val; |
713 | return sysctl_lookup(SYSCTLFN_CALL(&node)); |
714 | } |
715 | |
716 | /* |
717 | * Returns the target memory reservation of the domain |
718 | * When reading, this sysctl will return the value of the balloon_target |
719 | * variable, converted into KiB |
720 | * When used for writing, it will update the new memory/target value |
721 | * in XenStore, but will not update the balloon_target variable directly. |
722 | * This will be done by the Xenbus watch handler, balloon_xenbus_watcher(). |
723 | */ |
724 | static int |
725 | sysctl_kern_xen_balloon_target(SYSCTLFN_ARGS) |
726 | { |
727 | struct sysctlnode node; |
728 | u_quad_t newval, res_min, res_max; |
729 | int error; |
730 | |
731 | node = *rnode; |
732 | node.sysctl_data = &newval; |
733 | |
734 | mutex_enter(&balloon_sc->balloon_mtx); |
735 | newval = BALLOON_PAGES_TO_KB(balloon_sc->balloon_target); |
736 | res_min = balloon_sc->balloon_res_min; |
737 | mutex_exit(&balloon_sc->balloon_mtx); |
738 | |
739 | error = sysctl_lookup(SYSCTLFN_CALL(&node)); |
740 | if (newp == NULL || error != 0) { |
741 | return error; |
742 | } |
743 | |
744 | /* |
745 | * Sanity check new size |
746 | * We should not balloon below the minimum reservation |
747 | * set by the domain, nor above the maximum reservation set |
748 | * by domain controller. |
749 | * Note: domain is not supposed to receive balloon requests when |
750 | * they are above maximum reservation, but better be safe than |
751 | * sorry. |
752 | */ |
753 | res_max = BALLOON_PAGES_TO_KB(xenmem_get_maxreservation()); |
754 | if (newval < res_min || newval > res_max) { |
755 | #if BALLOONDEBUG |
756 | device_printf(balloon_sc->sc_dev, |
757 | "new value out of bounds: %" PRIu64"\n" , newval); |
758 | device_printf(balloon_sc->sc_dev, |
759 | "min %" PRIu64", max %" PRIu64"\n" , res_min, res_max); |
760 | #endif |
761 | return EPERM; |
762 | } |
763 | |
764 | /* |
765 | * Write new value inside Xenstore. This will fire the memory/target |
766 | * watch handler, balloon_xenbus_watcher(). |
767 | */ |
768 | balloon_xenbus_write_target(newval); |
769 | |
770 | return 0; |
771 | } |
772 | |
773 | /* sysctl(9) nodes creation */ |
774 | static void |
775 | sysctl_kern_xen_balloon_setup(struct balloon_xenbus_softc *sc) |
776 | { |
777 | const struct sysctlnode *node = NULL; |
778 | struct sysctllog **clog = &sc->sc_log; |
779 | |
780 | sysctl_createv(clog, 0, NULL, &node, |
781 | CTLFLAG_PERMANENT, |
782 | CTLTYPE_NODE, "machdep" , NULL, |
783 | NULL, 0, NULL, 0, |
784 | CTL_MACHDEP, CTL_EOL); |
785 | |
786 | sysctl_createv(clog, 0, &node, &node, |
787 | CTLFLAG_PERMANENT, |
788 | CTLTYPE_NODE, "xen" , |
789 | SYSCTL_DESCR("Xen top level node" ), |
790 | NULL, 0, NULL, 0, |
791 | CTL_CREATE, CTL_EOL); |
792 | |
793 | sysctl_createv(clog, 0, &node, &node, |
794 | CTLFLAG_PERMANENT, |
795 | CTLTYPE_NODE, "balloon" , |
796 | SYSCTL_DESCR("Balloon details" ), |
797 | NULL, 0, NULL, 0, |
798 | CTL_CREATE, CTL_EOL); |
799 | |
800 | sysctl_createv(clog, 0, &node, NULL, |
801 | CTLFLAG_PERMANENT | CTLFLAG_READONLY, |
802 | CTLTYPE_QUAD, "current" , |
803 | SYSCTL_DESCR("Domain's current memory reservation from " |
804 | "hypervisor, in KiB." ), |
805 | sysctl_kern_xen_balloon_current, 0, NULL, 0, |
806 | CTL_CREATE, CTL_EOL); |
807 | |
808 | sysctl_createv(clog, 0, &node, NULL, |
809 | CTLFLAG_PERMANENT | CTLFLAG_READWRITE, |
810 | CTLTYPE_QUAD, "target" , |
811 | SYSCTL_DESCR("Target memory reservation for domain, in KiB." ), |
812 | sysctl_kern_xen_balloon_target, 0, NULL, 0, |
813 | CTL_CREATE, CTL_EOL); |
814 | |
815 | sysctl_createv(clog, 0, &node, NULL, |
816 | CTLFLAG_PERMANENT | CTLFLAG_READWRITE, |
817 | CTLTYPE_QUAD, "min" , |
818 | SYSCTL_DESCR("Minimum amount of memory the domain " |
819 | "reserves, in KiB." ), |
820 | sysctl_kern_xen_balloon_min, 0, NULL, 0, |
821 | CTL_CREATE, CTL_EOL); |
822 | |
823 | sysctl_createv(clog, 0, &node, NULL, |
824 | CTLFLAG_PERMANENT | CTLFLAG_READONLY, |
825 | CTLTYPE_QUAD, "max" , |
826 | SYSCTL_DESCR("Maximum amount of memory the domain " |
827 | "can use, in KiB." ), |
828 | sysctl_kern_xen_balloon_max, 0, NULL, 0, |
829 | CTL_CREATE, CTL_EOL); |
830 | } |
831 | |