1 /*
2  * Postcopy migration for RAM
3  *
4  * Copyright 2013-2015 Red Hat, Inc. and/or its affiliates
5  *
6  * Authors:
7  *  Dave Gilbert  <dgilbert@redhat.com>
8  *
9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
10  * See the COPYING file in the top-level directory.
11  *
12  */
13 
14 /*
15  * Postcopy is a migration technique where the execution flips from the
16  * source to the destination before all the data has been copied.
17  */
18 
19 #include "qemu/osdep.h"
20 #include "exec/target_page.h"
21 #include "migration.h"
22 #include "qemu-file.h"
23 #include "savevm.h"
24 #include "postcopy-ram.h"
25 #include "ram.h"
26 #include "qapi/error.h"
27 #include "qemu/notify.h"
28 #include "qemu/rcu.h"
29 #include "sysemu/sysemu.h"
30 #include "sysemu/balloon.h"
31 #include "qemu/error-report.h"
32 #include "trace.h"
33 #include "hw/boards.h"
34 
35 /* Arbitrary limit on size of each discard command,
36  * keeps them around ~200 bytes
37  */
38 #define MAX_DISCARDS_PER_COMMAND 12
39 
40 struct PostcopyDiscardState {
41     const char *ramblock_name;
42     uint16_t cur_entry;
43     /*
44      * Start and length of a discard range (bytes)
45      */
46     uint64_t start_list[MAX_DISCARDS_PER_COMMAND];
47     uint64_t length_list[MAX_DISCARDS_PER_COMMAND];
48     unsigned int nsentwords;
49     unsigned int nsentcmds;
50 };
51 
52 static NotifierWithReturnList postcopy_notifier_list;
53 
postcopy_infrastructure_init(void)54 void postcopy_infrastructure_init(void)
55 {
56     notifier_with_return_list_init(&postcopy_notifier_list);
57 }
58 
postcopy_add_notifier(NotifierWithReturn * nn)59 void postcopy_add_notifier(NotifierWithReturn *nn)
60 {
61     notifier_with_return_list_add(&postcopy_notifier_list, nn);
62 }
63 
postcopy_remove_notifier(NotifierWithReturn * n)64 void postcopy_remove_notifier(NotifierWithReturn *n)
65 {
66     notifier_with_return_remove(n);
67 }
68 
postcopy_notify(enum PostcopyNotifyReason reason,Error ** errp)69 int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp)
70 {
71     struct PostcopyNotifyData pnd;
72     pnd.reason = reason;
73     pnd.errp = errp;
74 
75     return notifier_with_return_list_notify(&postcopy_notifier_list,
76                                             &pnd);
77 }
78 
79 /* Postcopy needs to detect accesses to pages that haven't yet been copied
80  * across, and efficiently map new pages in, the techniques for doing this
81  * are target OS specific.
82  */
83 #if defined(__linux__)
84 
85 #include <poll.h>
86 #include <sys/ioctl.h>
87 #include <sys/syscall.h>
88 #include <asm/types.h> /* for __u64 */
89 #endif
90 
91 #if defined(__linux__) && defined(__NR_userfaultfd) && defined(CONFIG_EVENTFD)
92 #include <sys/eventfd.h>
93 #include <linux/userfaultfd.h>
94 
95 typedef struct PostcopyBlocktimeContext {
96     /* time when page fault initiated per vCPU */
97     uint32_t *page_fault_vcpu_time;
98     /* page address per vCPU */
99     uintptr_t *vcpu_addr;
100     uint32_t total_blocktime;
101     /* blocktime per vCPU */
102     uint32_t *vcpu_blocktime;
103     /* point in time when last page fault was initiated */
104     uint32_t last_begin;
105     /* number of vCPU are suspended */
106     int smp_cpus_down;
107     uint64_t start_time;
108 
109     /*
110      * Handler for exit event, necessary for
111      * releasing whole blocktime_ctx
112      */
113     Notifier exit_notifier;
114 } PostcopyBlocktimeContext;
115 
destroy_blocktime_context(struct PostcopyBlocktimeContext * ctx)116 static void destroy_blocktime_context(struct PostcopyBlocktimeContext *ctx)
117 {
118     g_free(ctx->page_fault_vcpu_time);
119     g_free(ctx->vcpu_addr);
120     g_free(ctx->vcpu_blocktime);
121     g_free(ctx);
122 }
123 
migration_exit_cb(Notifier * n,void * data)124 static void migration_exit_cb(Notifier *n, void *data)
125 {
126     PostcopyBlocktimeContext *ctx = container_of(n, PostcopyBlocktimeContext,
127                                                  exit_notifier);
128     destroy_blocktime_context(ctx);
129 }
130 
blocktime_context_new(void)131 static struct PostcopyBlocktimeContext *blocktime_context_new(void)
132 {
133     MachineState *ms = MACHINE(qdev_get_machine());
134     unsigned int smp_cpus = ms->smp.cpus;
135     PostcopyBlocktimeContext *ctx = g_new0(PostcopyBlocktimeContext, 1);
136     ctx->page_fault_vcpu_time = g_new0(uint32_t, smp_cpus);
137     ctx->vcpu_addr = g_new0(uintptr_t, smp_cpus);
138     ctx->vcpu_blocktime = g_new0(uint32_t, smp_cpus);
139 
140     ctx->exit_notifier.notify = migration_exit_cb;
141     ctx->start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
142     qemu_add_exit_notifier(&ctx->exit_notifier);
143     return ctx;
144 }
145 
get_vcpu_blocktime_list(PostcopyBlocktimeContext * ctx)146 static uint32List *get_vcpu_blocktime_list(PostcopyBlocktimeContext *ctx)
147 {
148     MachineState *ms = MACHINE(qdev_get_machine());
149     uint32List *list = NULL, *entry = NULL;
150     int i;
151 
152     for (i = ms->smp.cpus - 1; i >= 0; i--) {
153         entry = g_new0(uint32List, 1);
154         entry->value = ctx->vcpu_blocktime[i];
155         entry->next = list;
156         list = entry;
157     }
158 
159     return list;
160 }
161 
162 /*
163  * This function just populates MigrationInfo from postcopy's
164  * blocktime context. It will not populate MigrationInfo,
165  * unless postcopy-blocktime capability was set.
166  *
167  * @info: pointer to MigrationInfo to populate
168  */
fill_destination_postcopy_migration_info(MigrationInfo * info)169 void fill_destination_postcopy_migration_info(MigrationInfo *info)
170 {
171     MigrationIncomingState *mis = migration_incoming_get_current();
172     PostcopyBlocktimeContext *bc = mis->blocktime_ctx;
173 
174     if (!bc) {
175         return;
176     }
177 
178     info->has_postcopy_blocktime = true;
179     info->postcopy_blocktime = bc->total_blocktime;
180     info->has_postcopy_vcpu_blocktime = true;
181     info->postcopy_vcpu_blocktime = get_vcpu_blocktime_list(bc);
182 }
183 
get_postcopy_total_blocktime(void)184 static uint32_t get_postcopy_total_blocktime(void)
185 {
186     MigrationIncomingState *mis = migration_incoming_get_current();
187     PostcopyBlocktimeContext *bc = mis->blocktime_ctx;
188 
189     if (!bc) {
190         return 0;
191     }
192 
193     return bc->total_blocktime;
194 }
195 
196 /**
197  * receive_ufd_features: check userfault fd features, to request only supported
198  * features in the future.
199  *
200  * Returns: true on success
201  *
202  * __NR_userfaultfd - should be checked before
203  *  @features: out parameter will contain uffdio_api.features provided by kernel
204  *              in case of success
205  */
receive_ufd_features(uint64_t * features)206 static bool receive_ufd_features(uint64_t *features)
207 {
208     struct uffdio_api api_struct = {0};
209     int ufd;
210     bool ret = true;
211 
212     /* if we are here __NR_userfaultfd should exists */
213     ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
214     if (ufd == -1) {
215         error_report("%s: syscall __NR_userfaultfd failed: %s", __func__,
216                      strerror(errno));
217         return false;
218     }
219 
220     /* ask features */
221     api_struct.api = UFFD_API;
222     api_struct.features = 0;
223     if (ioctl(ufd, UFFDIO_API, &api_struct)) {
224         error_report("%s: UFFDIO_API failed: %s", __func__,
225                      strerror(errno));
226         ret = false;
227         goto release_ufd;
228     }
229 
230     *features = api_struct.features;
231 
232 release_ufd:
233     close(ufd);
234     return ret;
235 }
236 
237 /**
238  * request_ufd_features: this function should be called only once on a newly
239  * opened ufd, subsequent calls will lead to error.
240  *
241  * Returns: true on succes
242  *
243  * @ufd: fd obtained from userfaultfd syscall
244  * @features: bit mask see UFFD_API_FEATURES
245  */
request_ufd_features(int ufd,uint64_t features)246 static bool request_ufd_features(int ufd, uint64_t features)
247 {
248     struct uffdio_api api_struct = {0};
249     uint64_t ioctl_mask;
250 
251     api_struct.api = UFFD_API;
252     api_struct.features = features;
253     if (ioctl(ufd, UFFDIO_API, &api_struct)) {
254         error_report("%s failed: UFFDIO_API failed: %s", __func__,
255                      strerror(errno));
256         return false;
257     }
258 
259     ioctl_mask = (__u64)1 << _UFFDIO_REGISTER |
260                  (__u64)1 << _UFFDIO_UNREGISTER;
261     if ((api_struct.ioctls & ioctl_mask) != ioctl_mask) {
262         error_report("Missing userfault features: %" PRIx64,
263                      (uint64_t)(~api_struct.ioctls & ioctl_mask));
264         return false;
265     }
266 
267     return true;
268 }
269 
ufd_check_and_apply(int ufd,MigrationIncomingState * mis)270 static bool ufd_check_and_apply(int ufd, MigrationIncomingState *mis)
271 {
272     uint64_t asked_features = 0;
273     static uint64_t supported_features;
274 
275     /*
276      * it's not possible to
277      * request UFFD_API twice per one fd
278      * userfault fd features is persistent
279      */
280     if (!supported_features) {
281         if (!receive_ufd_features(&supported_features)) {
282             error_report("%s failed", __func__);
283             return false;
284         }
285     }
286 
287 #ifdef UFFD_FEATURE_THREAD_ID
288     if (migrate_postcopy_blocktime() && mis &&
289         UFFD_FEATURE_THREAD_ID & supported_features) {
290         /* kernel supports that feature */
291         /* don't create blocktime_context if it exists */
292         if (!mis->blocktime_ctx) {
293             mis->blocktime_ctx = blocktime_context_new();
294         }
295 
296         asked_features |= UFFD_FEATURE_THREAD_ID;
297     }
298 #endif
299 
300     /*
301      * request features, even if asked_features is 0, due to
302      * kernel expects UFFD_API before UFFDIO_REGISTER, per
303      * userfault file descriptor
304      */
305     if (!request_ufd_features(ufd, asked_features)) {
306         error_report("%s failed: features %" PRIu64, __func__,
307                      asked_features);
308         return false;
309     }
310 
311     if (qemu_real_host_page_size != ram_pagesize_summary()) {
312         bool have_hp = false;
313         /* We've got a huge page */
314 #ifdef UFFD_FEATURE_MISSING_HUGETLBFS
315         have_hp = supported_features & UFFD_FEATURE_MISSING_HUGETLBFS;
316 #endif
317         if (!have_hp) {
318             error_report("Userfault on this host does not support huge pages");
319             return false;
320         }
321     }
322     return true;
323 }
324 
325 /* Callback from postcopy_ram_supported_by_host block iterator.
326  */
test_ramblock_postcopiable(RAMBlock * rb,void * opaque)327 static int test_ramblock_postcopiable(RAMBlock *rb, void *opaque)
328 {
329     const char *block_name = qemu_ram_get_idstr(rb);
330     ram_addr_t length = qemu_ram_get_used_length(rb);
331     size_t pagesize = qemu_ram_pagesize(rb);
332 
333     if (length % pagesize) {
334         error_report("Postcopy requires RAM blocks to be a page size multiple,"
335                      " block %s is 0x" RAM_ADDR_FMT " bytes with a "
336                      "page size of 0x%zx", block_name, length, pagesize);
337         return 1;
338     }
339     return 0;
340 }
341 
342 /*
343  * Note: This has the side effect of munlock'ing all of RAM, that's
344  * normally fine since if the postcopy succeeds it gets turned back on at the
345  * end.
346  */
postcopy_ram_supported_by_host(MigrationIncomingState * mis)347 bool postcopy_ram_supported_by_host(MigrationIncomingState *mis)
348 {
349     long pagesize = qemu_real_host_page_size;
350     int ufd = -1;
351     bool ret = false; /* Error unless we change it */
352     void *testarea = NULL;
353     struct uffdio_register reg_struct;
354     struct uffdio_range range_struct;
355     uint64_t feature_mask;
356     Error *local_err = NULL;
357 
358     if (qemu_target_page_size() > pagesize) {
359         error_report("Target page size bigger than host page size");
360         goto out;
361     }
362 
363     ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
364     if (ufd == -1) {
365         error_report("%s: userfaultfd not available: %s", __func__,
366                      strerror(errno));
367         goto out;
368     }
369 
370     /* Give devices a chance to object */
371     if (postcopy_notify(POSTCOPY_NOTIFY_PROBE, &local_err)) {
372         error_report_err(local_err);
373         goto out;
374     }
375 
376     /* Version and features check */
377     if (!ufd_check_and_apply(ufd, mis)) {
378         goto out;
379     }
380 
381     /* We don't support postcopy with shared RAM yet */
382     if (foreach_not_ignored_block(test_ramblock_postcopiable, NULL)) {
383         goto out;
384     }
385 
386     /*
387      * userfault and mlock don't go together; we'll put it back later if
388      * it was enabled.
389      */
390     if (munlockall()) {
391         error_report("%s: munlockall: %s", __func__,  strerror(errno));
392         return -1;
393     }
394 
395     /*
396      *  We need to check that the ops we need are supported on anon memory
397      *  To do that we need to register a chunk and see the flags that
398      *  are returned.
399      */
400     testarea = mmap(NULL, pagesize, PROT_READ | PROT_WRITE, MAP_PRIVATE |
401                                     MAP_ANONYMOUS, -1, 0);
402     if (testarea == MAP_FAILED) {
403         error_report("%s: Failed to map test area: %s", __func__,
404                      strerror(errno));
405         goto out;
406     }
407     g_assert(((size_t)testarea & (pagesize-1)) == 0);
408 
409     reg_struct.range.start = (uintptr_t)testarea;
410     reg_struct.range.len = pagesize;
411     reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
412 
413     if (ioctl(ufd, UFFDIO_REGISTER, &reg_struct)) {
414         error_report("%s userfault register: %s", __func__, strerror(errno));
415         goto out;
416     }
417 
418     range_struct.start = (uintptr_t)testarea;
419     range_struct.len = pagesize;
420     if (ioctl(ufd, UFFDIO_UNREGISTER, &range_struct)) {
421         error_report("%s userfault unregister: %s", __func__, strerror(errno));
422         goto out;
423     }
424 
425     feature_mask = (__u64)1 << _UFFDIO_WAKE |
426                    (__u64)1 << _UFFDIO_COPY |
427                    (__u64)1 << _UFFDIO_ZEROPAGE;
428     if ((reg_struct.ioctls & feature_mask) != feature_mask) {
429         error_report("Missing userfault map features: %" PRIx64,
430                      (uint64_t)(~reg_struct.ioctls & feature_mask));
431         goto out;
432     }
433 
434     /* Success! */
435     ret = true;
436 out:
437     if (testarea) {
438         munmap(testarea, pagesize);
439     }
440     if (ufd != -1) {
441         close(ufd);
442     }
443     return ret;
444 }
445 
446 /*
447  * Setup an area of RAM so that it *can* be used for postcopy later; this
448  * must be done right at the start prior to pre-copy.
449  * opaque should be the MIS.
450  */
init_range(RAMBlock * rb,void * opaque)451 static int init_range(RAMBlock *rb, void *opaque)
452 {
453     const char *block_name = qemu_ram_get_idstr(rb);
454     void *host_addr = qemu_ram_get_host_addr(rb);
455     ram_addr_t offset = qemu_ram_get_offset(rb);
456     ram_addr_t length = qemu_ram_get_used_length(rb);
457     trace_postcopy_init_range(block_name, host_addr, offset, length);
458 
459     /*
460      * We need the whole of RAM to be truly empty for postcopy, so things
461      * like ROMs and any data tables built during init must be zero'd
462      * - we're going to get the copy from the source anyway.
463      * (Precopy will just overwrite this data, so doesn't need the discard)
464      */
465     if (ram_discard_range(block_name, 0, length)) {
466         return -1;
467     }
468 
469     return 0;
470 }
471 
472 /*
473  * At the end of migration, undo the effects of init_range
474  * opaque should be the MIS.
475  */
cleanup_range(RAMBlock * rb,void * opaque)476 static int cleanup_range(RAMBlock *rb, void *opaque)
477 {
478     const char *block_name = qemu_ram_get_idstr(rb);
479     void *host_addr = qemu_ram_get_host_addr(rb);
480     ram_addr_t offset = qemu_ram_get_offset(rb);
481     ram_addr_t length = qemu_ram_get_used_length(rb);
482     MigrationIncomingState *mis = opaque;
483     struct uffdio_range range_struct;
484     trace_postcopy_cleanup_range(block_name, host_addr, offset, length);
485 
486     /*
487      * We turned off hugepage for the precopy stage with postcopy enabled
488      * we can turn it back on now.
489      */
490     qemu_madvise(host_addr, length, QEMU_MADV_HUGEPAGE);
491 
492     /*
493      * We can also turn off userfault now since we should have all the
494      * pages.   It can be useful to leave it on to debug postcopy
495      * if you're not sure it's always getting every page.
496      */
497     range_struct.start = (uintptr_t)host_addr;
498     range_struct.len = length;
499 
500     if (ioctl(mis->userfault_fd, UFFDIO_UNREGISTER, &range_struct)) {
501         error_report("%s: userfault unregister %s", __func__, strerror(errno));
502 
503         return -1;
504     }
505 
506     return 0;
507 }
508 
509 /*
510  * Initialise postcopy-ram, setting the RAM to a state where we can go into
511  * postcopy later; must be called prior to any precopy.
512  * called from arch_init's similarly named ram_postcopy_incoming_init
513  */
postcopy_ram_incoming_init(MigrationIncomingState * mis)514 int postcopy_ram_incoming_init(MigrationIncomingState *mis)
515 {
516     if (foreach_not_ignored_block(init_range, NULL)) {
517         return -1;
518     }
519 
520     return 0;
521 }
522 
523 /*
524  * Manage a single vote to the QEMU balloon inhibitor for all postcopy usage,
525  * last caller wins.
526  */
postcopy_balloon_inhibit(bool state)527 static void postcopy_balloon_inhibit(bool state)
528 {
529     static bool cur_state = false;
530 
531     if (state != cur_state) {
532         qemu_balloon_inhibit(state);
533         cur_state = state;
534     }
535 }
536 
537 /*
538  * At the end of a migration where postcopy_ram_incoming_init was called.
539  */
postcopy_ram_incoming_cleanup(MigrationIncomingState * mis)540 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
541 {
542     trace_postcopy_ram_incoming_cleanup_entry();
543 
544     if (mis->have_fault_thread) {
545         Error *local_err = NULL;
546 
547         /* Let the fault thread quit */
548         atomic_set(&mis->fault_thread_quit, 1);
549         postcopy_fault_thread_notify(mis);
550         trace_postcopy_ram_incoming_cleanup_join();
551         qemu_thread_join(&mis->fault_thread);
552 
553         if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_END, &local_err)) {
554             error_report_err(local_err);
555             return -1;
556         }
557 
558         if (foreach_not_ignored_block(cleanup_range, mis)) {
559             return -1;
560         }
561 
562         trace_postcopy_ram_incoming_cleanup_closeuf();
563         close(mis->userfault_fd);
564         close(mis->userfault_event_fd);
565         mis->have_fault_thread = false;
566     }
567 
568     postcopy_balloon_inhibit(false);
569 
570     if (enable_mlock) {
571         if (os_mlock() < 0) {
572             error_report("mlock: %s", strerror(errno));
573             /*
574              * It doesn't feel right to fail at this point, we have a valid
575              * VM state.
576              */
577         }
578     }
579 
580     if (mis->postcopy_tmp_page) {
581         munmap(mis->postcopy_tmp_page, mis->largest_page_size);
582         mis->postcopy_tmp_page = NULL;
583     }
584     if (mis->postcopy_tmp_zero_page) {
585         munmap(mis->postcopy_tmp_zero_page, mis->largest_page_size);
586         mis->postcopy_tmp_zero_page = NULL;
587     }
588     trace_postcopy_ram_incoming_cleanup_blocktime(
589             get_postcopy_total_blocktime());
590 
591     trace_postcopy_ram_incoming_cleanup_exit();
592     return 0;
593 }
594 
595 /*
596  * Disable huge pages on an area
597  */
nhp_range(RAMBlock * rb,void * opaque)598 static int nhp_range(RAMBlock *rb, void *opaque)
599 {
600     const char *block_name = qemu_ram_get_idstr(rb);
601     void *host_addr = qemu_ram_get_host_addr(rb);
602     ram_addr_t offset = qemu_ram_get_offset(rb);
603     ram_addr_t length = qemu_ram_get_used_length(rb);
604     trace_postcopy_nhp_range(block_name, host_addr, offset, length);
605 
606     /*
607      * Before we do discards we need to ensure those discards really
608      * do delete areas of the page, even if THP thinks a hugepage would
609      * be a good idea, so force hugepages off.
610      */
611     qemu_madvise(host_addr, length, QEMU_MADV_NOHUGEPAGE);
612 
613     return 0;
614 }
615 
616 /*
617  * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
618  * however leaving it until after precopy means that most of the precopy
619  * data is still THPd
620  */
postcopy_ram_prepare_discard(MigrationIncomingState * mis)621 int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
622 {
623     if (foreach_not_ignored_block(nhp_range, mis)) {
624         return -1;
625     }
626 
627     postcopy_state_set(POSTCOPY_INCOMING_DISCARD);
628 
629     return 0;
630 }
631 
632 /*
633  * Mark the given area of RAM as requiring notification to unwritten areas
634  * Used as a  callback on foreach_not_ignored_block.
635  *   host_addr: Base of area to mark
636  *   offset: Offset in the whole ram arena
637  *   length: Length of the section
638  *   opaque: MigrationIncomingState pointer
639  * Returns 0 on success
640  */
ram_block_enable_notify(RAMBlock * rb,void * opaque)641 static int ram_block_enable_notify(RAMBlock *rb, void *opaque)
642 {
643     MigrationIncomingState *mis = opaque;
644     struct uffdio_register reg_struct;
645 
646     reg_struct.range.start = (uintptr_t)qemu_ram_get_host_addr(rb);
647     reg_struct.range.len = qemu_ram_get_used_length(rb);
648     reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
649 
650     /* Now tell our userfault_fd that it's responsible for this area */
651     if (ioctl(mis->userfault_fd, UFFDIO_REGISTER, &reg_struct)) {
652         error_report("%s userfault register: %s", __func__, strerror(errno));
653         return -1;
654     }
655     if (!(reg_struct.ioctls & ((__u64)1 << _UFFDIO_COPY))) {
656         error_report("%s userfault: Region doesn't support COPY", __func__);
657         return -1;
658     }
659     if (reg_struct.ioctls & ((__u64)1 << _UFFDIO_ZEROPAGE)) {
660         qemu_ram_set_uf_zeroable(rb);
661     }
662 
663     return 0;
664 }
665 
postcopy_wake_shared(struct PostCopyFD * pcfd,uint64_t client_addr,RAMBlock * rb)666 int postcopy_wake_shared(struct PostCopyFD *pcfd,
667                          uint64_t client_addr,
668                          RAMBlock *rb)
669 {
670     size_t pagesize = qemu_ram_pagesize(rb);
671     struct uffdio_range range;
672     int ret;
673     trace_postcopy_wake_shared(client_addr, qemu_ram_get_idstr(rb));
674     range.start = client_addr & ~(pagesize - 1);
675     range.len = pagesize;
676     ret = ioctl(pcfd->fd, UFFDIO_WAKE, &range);
677     if (ret) {
678         error_report("%s: Failed to wake: %zx in %s (%s)",
679                      __func__, (size_t)client_addr, qemu_ram_get_idstr(rb),
680                      strerror(errno));
681     }
682     return ret;
683 }
684 
685 /*
686  * Callback from shared fault handlers to ask for a page,
687  * the page must be specified by a RAMBlock and an offset in that rb
688  * Note: Only for use by shared fault handlers (in fault thread)
689  */
postcopy_request_shared_page(struct PostCopyFD * pcfd,RAMBlock * rb,uint64_t client_addr,uint64_t rb_offset)690 int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
691                                  uint64_t client_addr, uint64_t rb_offset)
692 {
693     size_t pagesize = qemu_ram_pagesize(rb);
694     uint64_t aligned_rbo = rb_offset & ~(pagesize - 1);
695     MigrationIncomingState *mis = migration_incoming_get_current();
696 
697     trace_postcopy_request_shared_page(pcfd->idstr, qemu_ram_get_idstr(rb),
698                                        rb_offset);
699     if (ramblock_recv_bitmap_test_byte_offset(rb, aligned_rbo)) {
700         trace_postcopy_request_shared_page_present(pcfd->idstr,
701                                         qemu_ram_get_idstr(rb), rb_offset);
702         return postcopy_wake_shared(pcfd, client_addr, rb);
703     }
704     if (rb != mis->last_rb) {
705         mis->last_rb = rb;
706         migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb),
707                                   aligned_rbo, pagesize);
708     } else {
709         /* Save some space */
710         migrate_send_rp_req_pages(mis, NULL, aligned_rbo, pagesize);
711     }
712     return 0;
713 }
714 
get_mem_fault_cpu_index(uint32_t pid)715 static int get_mem_fault_cpu_index(uint32_t pid)
716 {
717     CPUState *cpu_iter;
718 
719     CPU_FOREACH(cpu_iter) {
720         if (cpu_iter->thread_id == pid) {
721             trace_get_mem_fault_cpu_index(cpu_iter->cpu_index, pid);
722             return cpu_iter->cpu_index;
723         }
724     }
725     trace_get_mem_fault_cpu_index(-1, pid);
726     return -1;
727 }
728 
get_low_time_offset(PostcopyBlocktimeContext * dc)729 static uint32_t get_low_time_offset(PostcopyBlocktimeContext *dc)
730 {
731     int64_t start_time_offset = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) -
732                                     dc->start_time;
733     return start_time_offset < 1 ? 1 : start_time_offset & UINT32_MAX;
734 }
735 
736 /*
737  * This function is being called when pagefault occurs. It
738  * tracks down vCPU blocking time.
739  *
740  * @addr: faulted host virtual address
741  * @ptid: faulted process thread id
742  * @rb: ramblock appropriate to addr
743  */
mark_postcopy_blocktime_begin(uintptr_t addr,uint32_t ptid,RAMBlock * rb)744 static void mark_postcopy_blocktime_begin(uintptr_t addr, uint32_t ptid,
745                                           RAMBlock *rb)
746 {
747     int cpu, already_received;
748     MigrationIncomingState *mis = migration_incoming_get_current();
749     PostcopyBlocktimeContext *dc = mis->blocktime_ctx;
750     uint32_t low_time_offset;
751 
752     if (!dc || ptid == 0) {
753         return;
754     }
755     cpu = get_mem_fault_cpu_index(ptid);
756     if (cpu < 0) {
757         return;
758     }
759 
760     low_time_offset = get_low_time_offset(dc);
761     if (dc->vcpu_addr[cpu] == 0) {
762         atomic_inc(&dc->smp_cpus_down);
763     }
764 
765     atomic_xchg(&dc->last_begin, low_time_offset);
766     atomic_xchg(&dc->page_fault_vcpu_time[cpu], low_time_offset);
767     atomic_xchg(&dc->vcpu_addr[cpu], addr);
768 
769     /*
770      * check it here, not at the beginning of the function,
771      * due to, check could occur early than bitmap_set in
772      * qemu_ufd_copy_ioctl
773      */
774     already_received = ramblock_recv_bitmap_test(rb, (void *)addr);
775     if (already_received) {
776         atomic_xchg(&dc->vcpu_addr[cpu], 0);
777         atomic_xchg(&dc->page_fault_vcpu_time[cpu], 0);
778         atomic_dec(&dc->smp_cpus_down);
779     }
780     trace_mark_postcopy_blocktime_begin(addr, dc, dc->page_fault_vcpu_time[cpu],
781                                         cpu, already_received);
782 }
783 
784 /*
785  *  This function just provide calculated blocktime per cpu and trace it.
786  *  Total blocktime is calculated in mark_postcopy_blocktime_end.
787  *
788  *
789  * Assume we have 3 CPU
790  *
791  *      S1        E1           S1               E1
792  * -----***********------------xxx***************------------------------> CPU1
793  *
794  *             S2                E2
795  * ------------****************xxx---------------------------------------> CPU2
796  *
797  *                         S3            E3
798  * ------------------------****xxx********-------------------------------> CPU3
799  *
800  * We have sequence S1,S2,E1,S3,S1,E2,E3,E1
801  * S2,E1 - doesn't match condition due to sequence S1,S2,E1 doesn't include CPU3
802  * S3,S1,E2 - sequence includes all CPUs, in this case overlap will be S1,E2 -
803  *            it's a part of total blocktime.
804  * S1 - here is last_begin
805  * Legend of the picture is following:
806  *              * - means blocktime per vCPU
807  *              x - means overlapped blocktime (total blocktime)
808  *
809  * @addr: host virtual address
810  */
mark_postcopy_blocktime_end(uintptr_t addr)811 static void mark_postcopy_blocktime_end(uintptr_t addr)
812 {
813     MigrationIncomingState *mis = migration_incoming_get_current();
814     PostcopyBlocktimeContext *dc = mis->blocktime_ctx;
815     MachineState *ms = MACHINE(qdev_get_machine());
816     unsigned int smp_cpus = ms->smp.cpus;
817     int i, affected_cpu = 0;
818     bool vcpu_total_blocktime = false;
819     uint32_t read_vcpu_time, low_time_offset;
820 
821     if (!dc) {
822         return;
823     }
824 
825     low_time_offset = get_low_time_offset(dc);
826     /* lookup cpu, to clear it,
827      * that algorithm looks straighforward, but it's not
828      * optimal, more optimal algorithm is keeping tree or hash
829      * where key is address value is a list of  */
830     for (i = 0; i < smp_cpus; i++) {
831         uint32_t vcpu_blocktime = 0;
832 
833         read_vcpu_time = atomic_fetch_add(&dc->page_fault_vcpu_time[i], 0);
834         if (atomic_fetch_add(&dc->vcpu_addr[i], 0) != addr ||
835             read_vcpu_time == 0) {
836             continue;
837         }
838         atomic_xchg(&dc->vcpu_addr[i], 0);
839         vcpu_blocktime = low_time_offset - read_vcpu_time;
840         affected_cpu += 1;
841         /* we need to know is that mark_postcopy_end was due to
842          * faulted page, another possible case it's prefetched
843          * page and in that case we shouldn't be here */
844         if (!vcpu_total_blocktime &&
845             atomic_fetch_add(&dc->smp_cpus_down, 0) == smp_cpus) {
846             vcpu_total_blocktime = true;
847         }
848         /* continue cycle, due to one page could affect several vCPUs */
849         dc->vcpu_blocktime[i] += vcpu_blocktime;
850     }
851 
852     atomic_sub(&dc->smp_cpus_down, affected_cpu);
853     if (vcpu_total_blocktime) {
854         dc->total_blocktime += low_time_offset - atomic_fetch_add(
855                 &dc->last_begin, 0);
856     }
857     trace_mark_postcopy_blocktime_end(addr, dc, dc->total_blocktime,
858                                       affected_cpu);
859 }
860 
postcopy_pause_fault_thread(MigrationIncomingState * mis)861 static bool postcopy_pause_fault_thread(MigrationIncomingState *mis)
862 {
863     trace_postcopy_pause_fault_thread();
864 
865     qemu_sem_wait(&mis->postcopy_pause_sem_fault);
866 
867     trace_postcopy_pause_fault_thread_continued();
868 
869     return true;
870 }
871 
872 /*
873  * Handle faults detected by the USERFAULT markings
874  */
postcopy_ram_fault_thread(void * opaque)875 static void *postcopy_ram_fault_thread(void *opaque)
876 {
877     MigrationIncomingState *mis = opaque;
878     struct uffd_msg msg;
879     int ret;
880     size_t index;
881     RAMBlock *rb = NULL;
882 
883     trace_postcopy_ram_fault_thread_entry();
884     rcu_register_thread();
885     mis->last_rb = NULL; /* last RAMBlock we sent part of */
886     qemu_sem_post(&mis->fault_thread_sem);
887 
888     struct pollfd *pfd;
889     size_t pfd_len = 2 + mis->postcopy_remote_fds->len;
890 
891     pfd = g_new0(struct pollfd, pfd_len);
892 
893     pfd[0].fd = mis->userfault_fd;
894     pfd[0].events = POLLIN;
895     pfd[1].fd = mis->userfault_event_fd;
896     pfd[1].events = POLLIN; /* Waiting for eventfd to go positive */
897     trace_postcopy_ram_fault_thread_fds_core(pfd[0].fd, pfd[1].fd);
898     for (index = 0; index < mis->postcopy_remote_fds->len; index++) {
899         struct PostCopyFD *pcfd = &g_array_index(mis->postcopy_remote_fds,
900                                                  struct PostCopyFD, index);
901         pfd[2 + index].fd = pcfd->fd;
902         pfd[2 + index].events = POLLIN;
903         trace_postcopy_ram_fault_thread_fds_extra(2 + index, pcfd->idstr,
904                                                   pcfd->fd);
905     }
906 
907     while (true) {
908         ram_addr_t rb_offset;
909         int poll_result;
910 
911         /*
912          * We're mainly waiting for the kernel to give us a faulting HVA,
913          * however we can be told to quit via userfault_quit_fd which is
914          * an eventfd
915          */
916 
917         poll_result = poll(pfd, pfd_len, -1 /* Wait forever */);
918         if (poll_result == -1) {
919             error_report("%s: userfault poll: %s", __func__, strerror(errno));
920             break;
921         }
922 
923         if (!mis->to_src_file) {
924             /*
925              * Possibly someone tells us that the return path is
926              * broken already using the event. We should hold until
927              * the channel is rebuilt.
928              */
929             if (postcopy_pause_fault_thread(mis)) {
930                 mis->last_rb = NULL;
931                 /* Continue to read the userfaultfd */
932             } else {
933                 error_report("%s: paused but don't allow to continue",
934                              __func__);
935                 break;
936             }
937         }
938 
939         if (pfd[1].revents) {
940             uint64_t tmp64 = 0;
941 
942             /* Consume the signal */
943             if (read(mis->userfault_event_fd, &tmp64, 8) != 8) {
944                 /* Nothing obviously nicer than posting this error. */
945                 error_report("%s: read() failed", __func__);
946             }
947 
948             if (atomic_read(&mis->fault_thread_quit)) {
949                 trace_postcopy_ram_fault_thread_quit();
950                 break;
951             }
952         }
953 
954         if (pfd[0].revents) {
955             poll_result--;
956             ret = read(mis->userfault_fd, &msg, sizeof(msg));
957             if (ret != sizeof(msg)) {
958                 if (errno == EAGAIN) {
959                     /*
960                      * if a wake up happens on the other thread just after
961                      * the poll, there is nothing to read.
962                      */
963                     continue;
964                 }
965                 if (ret < 0) {
966                     error_report("%s: Failed to read full userfault "
967                                  "message: %s",
968                                  __func__, strerror(errno));
969                     break;
970                 } else {
971                     error_report("%s: Read %d bytes from userfaultfd "
972                                  "expected %zd",
973                                  __func__, ret, sizeof(msg));
974                     break; /* Lost alignment, don't know what we'd read next */
975                 }
976             }
977             if (msg.event != UFFD_EVENT_PAGEFAULT) {
978                 error_report("%s: Read unexpected event %ud from userfaultfd",
979                              __func__, msg.event);
980                 continue; /* It's not a page fault, shouldn't happen */
981             }
982 
983             rb = qemu_ram_block_from_host(
984                      (void *)(uintptr_t)msg.arg.pagefault.address,
985                      true, &rb_offset);
986             if (!rb) {
987                 error_report("postcopy_ram_fault_thread: Fault outside guest: %"
988                              PRIx64, (uint64_t)msg.arg.pagefault.address);
989                 break;
990             }
991 
992             rb_offset &= ~(qemu_ram_pagesize(rb) - 1);
993             trace_postcopy_ram_fault_thread_request(msg.arg.pagefault.address,
994                                                 qemu_ram_get_idstr(rb),
995                                                 rb_offset,
996                                                 msg.arg.pagefault.feat.ptid);
997             mark_postcopy_blocktime_begin(
998                     (uintptr_t)(msg.arg.pagefault.address),
999                                 msg.arg.pagefault.feat.ptid, rb);
1000 
1001 retry:
1002             /*
1003              * Send the request to the source - we want to request one
1004              * of our host page sizes (which is >= TPS)
1005              */
1006             if (rb != mis->last_rb) {
1007                 mis->last_rb = rb;
1008                 ret = migrate_send_rp_req_pages(mis,
1009                                                 qemu_ram_get_idstr(rb),
1010                                                 rb_offset,
1011                                                 qemu_ram_pagesize(rb));
1012             } else {
1013                 /* Save some space */
1014                 ret = migrate_send_rp_req_pages(mis,
1015                                                 NULL,
1016                                                 rb_offset,
1017                                                 qemu_ram_pagesize(rb));
1018             }
1019 
1020             if (ret) {
1021                 /* May be network failure, try to wait for recovery */
1022                 if (ret == -EIO && postcopy_pause_fault_thread(mis)) {
1023                     /* We got reconnected somehow, try to continue */
1024                     mis->last_rb = NULL;
1025                     goto retry;
1026                 } else {
1027                     /* This is a unavoidable fault */
1028                     error_report("%s: migrate_send_rp_req_pages() get %d",
1029                                  __func__, ret);
1030                     break;
1031                 }
1032             }
1033         }
1034 
1035         /* Now handle any requests from external processes on shared memory */
1036         /* TODO: May need to handle devices deregistering during postcopy */
1037         for (index = 2; index < pfd_len && poll_result; index++) {
1038             if (pfd[index].revents) {
1039                 struct PostCopyFD *pcfd =
1040                     &g_array_index(mis->postcopy_remote_fds,
1041                                    struct PostCopyFD, index - 2);
1042 
1043                 poll_result--;
1044                 if (pfd[index].revents & POLLERR) {
1045                     error_report("%s: POLLERR on poll %zd fd=%d",
1046                                  __func__, index, pcfd->fd);
1047                     pfd[index].events = 0;
1048                     continue;
1049                 }
1050 
1051                 ret = read(pcfd->fd, &msg, sizeof(msg));
1052                 if (ret != sizeof(msg)) {
1053                     if (errno == EAGAIN) {
1054                         /*
1055                          * if a wake up happens on the other thread just after
1056                          * the poll, there is nothing to read.
1057                          */
1058                         continue;
1059                     }
1060                     if (ret < 0) {
1061                         error_report("%s: Failed to read full userfault "
1062                                      "message: %s (shared) revents=%d",
1063                                      __func__, strerror(errno),
1064                                      pfd[index].revents);
1065                         /*TODO: Could just disable this sharer */
1066                         break;
1067                     } else {
1068                         error_report("%s: Read %d bytes from userfaultfd "
1069                                      "expected %zd (shared)",
1070                                      __func__, ret, sizeof(msg));
1071                         /*TODO: Could just disable this sharer */
1072                         break; /*Lost alignment,don't know what we'd read next*/
1073                     }
1074                 }
1075                 if (msg.event != UFFD_EVENT_PAGEFAULT) {
1076                     error_report("%s: Read unexpected event %ud "
1077                                  "from userfaultfd (shared)",
1078                                  __func__, msg.event);
1079                     continue; /* It's not a page fault, shouldn't happen */
1080                 }
1081                 /* Call the device handler registered with us */
1082                 ret = pcfd->handler(pcfd, &msg);
1083                 if (ret) {
1084                     error_report("%s: Failed to resolve shared fault on %zd/%s",
1085                                  __func__, index, pcfd->idstr);
1086                     /* TODO: Fail? Disable this sharer? */
1087                 }
1088             }
1089         }
1090     }
1091     rcu_unregister_thread();
1092     trace_postcopy_ram_fault_thread_exit();
1093     g_free(pfd);
1094     return NULL;
1095 }
1096 
postcopy_ram_incoming_setup(MigrationIncomingState * mis)1097 int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
1098 {
1099     /* Open the fd for the kernel to give us userfaults */
1100     mis->userfault_fd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
1101     if (mis->userfault_fd == -1) {
1102         error_report("%s: Failed to open userfault fd: %s", __func__,
1103                      strerror(errno));
1104         return -1;
1105     }
1106 
1107     /*
1108      * Although the host check already tested the API, we need to
1109      * do the check again as an ABI handshake on the new fd.
1110      */
1111     if (!ufd_check_and_apply(mis->userfault_fd, mis)) {
1112         return -1;
1113     }
1114 
1115     /* Now an eventfd we use to tell the fault-thread to quit */
1116     mis->userfault_event_fd = eventfd(0, EFD_CLOEXEC);
1117     if (mis->userfault_event_fd == -1) {
1118         error_report("%s: Opening userfault_event_fd: %s", __func__,
1119                      strerror(errno));
1120         close(mis->userfault_fd);
1121         return -1;
1122     }
1123 
1124     qemu_sem_init(&mis->fault_thread_sem, 0);
1125     qemu_thread_create(&mis->fault_thread, "postcopy/fault",
1126                        postcopy_ram_fault_thread, mis, QEMU_THREAD_JOINABLE);
1127     qemu_sem_wait(&mis->fault_thread_sem);
1128     qemu_sem_destroy(&mis->fault_thread_sem);
1129     mis->have_fault_thread = true;
1130 
1131     /* Mark so that we get notified of accesses to unwritten areas */
1132     if (foreach_not_ignored_block(ram_block_enable_notify, mis)) {
1133         error_report("ram_block_enable_notify failed");
1134         return -1;
1135     }
1136 
1137     mis->postcopy_tmp_page = mmap(NULL, mis->largest_page_size,
1138                                   PROT_READ | PROT_WRITE, MAP_PRIVATE |
1139                                   MAP_ANONYMOUS, -1, 0);
1140     if (mis->postcopy_tmp_page == MAP_FAILED) {
1141         mis->postcopy_tmp_page = NULL;
1142         error_report("%s: Failed to map postcopy_tmp_page %s",
1143                      __func__, strerror(errno));
1144         return -1;
1145     }
1146 
1147     /*
1148      * Map large zero page when kernel can't use UFFDIO_ZEROPAGE for hugepages
1149      */
1150     mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size,
1151                                        PROT_READ | PROT_WRITE,
1152                                        MAP_PRIVATE | MAP_ANONYMOUS,
1153                                        -1, 0);
1154     if (mis->postcopy_tmp_zero_page == MAP_FAILED) {
1155         int e = errno;
1156         mis->postcopy_tmp_zero_page = NULL;
1157         error_report("%s: Failed to map large zero page %s",
1158                      __func__, strerror(e));
1159         return -e;
1160     }
1161     memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size);
1162 
1163     /*
1164      * Ballooning can mark pages as absent while we're postcopying
1165      * that would cause false userfaults.
1166      */
1167     postcopy_balloon_inhibit(true);
1168 
1169     trace_postcopy_ram_enable_notify();
1170 
1171     return 0;
1172 }
1173 
qemu_ufd_copy_ioctl(int userfault_fd,void * host_addr,void * from_addr,uint64_t pagesize,RAMBlock * rb)1174 static int qemu_ufd_copy_ioctl(int userfault_fd, void *host_addr,
1175                                void *from_addr, uint64_t pagesize, RAMBlock *rb)
1176 {
1177     int ret;
1178     if (from_addr) {
1179         struct uffdio_copy copy_struct;
1180         copy_struct.dst = (uint64_t)(uintptr_t)host_addr;
1181         copy_struct.src = (uint64_t)(uintptr_t)from_addr;
1182         copy_struct.len = pagesize;
1183         copy_struct.mode = 0;
1184         ret = ioctl(userfault_fd, UFFDIO_COPY, &copy_struct);
1185     } else {
1186         struct uffdio_zeropage zero_struct;
1187         zero_struct.range.start = (uint64_t)(uintptr_t)host_addr;
1188         zero_struct.range.len = pagesize;
1189         zero_struct.mode = 0;
1190         ret = ioctl(userfault_fd, UFFDIO_ZEROPAGE, &zero_struct);
1191     }
1192     if (!ret) {
1193         ramblock_recv_bitmap_set_range(rb, host_addr,
1194                                        pagesize / qemu_target_page_size());
1195         mark_postcopy_blocktime_end((uintptr_t)host_addr);
1196 
1197     }
1198     return ret;
1199 }
1200 
postcopy_notify_shared_wake(RAMBlock * rb,uint64_t offset)1201 int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset)
1202 {
1203     int i;
1204     MigrationIncomingState *mis = migration_incoming_get_current();
1205     GArray *pcrfds = mis->postcopy_remote_fds;
1206 
1207     for (i = 0; i < pcrfds->len; i++) {
1208         struct PostCopyFD *cur = &g_array_index(pcrfds, struct PostCopyFD, i);
1209         int ret = cur->waker(cur, rb, offset);
1210         if (ret) {
1211             return ret;
1212         }
1213     }
1214     return 0;
1215 }
1216 
1217 /*
1218  * Place a host page (from) at (host) atomically
1219  * returns 0 on success
1220  */
postcopy_place_page(MigrationIncomingState * mis,void * host,void * from,RAMBlock * rb)1221 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
1222                         RAMBlock *rb)
1223 {
1224     size_t pagesize = qemu_ram_pagesize(rb);
1225 
1226     /* copy also acks to the kernel waking the stalled thread up
1227      * TODO: We can inhibit that ack and only do it if it was requested
1228      * which would be slightly cheaper, but we'd have to be careful
1229      * of the order of updating our page state.
1230      */
1231     if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, from, pagesize, rb)) {
1232         int e = errno;
1233         error_report("%s: %s copy host: %p from: %p (size: %zd)",
1234                      __func__, strerror(e), host, from, pagesize);
1235 
1236         return -e;
1237     }
1238 
1239     trace_postcopy_place_page(host);
1240     return postcopy_notify_shared_wake(rb,
1241                                        qemu_ram_block_host_offset(rb, host));
1242 }
1243 
1244 /*
1245  * Place a zero page at (host) atomically
1246  * returns 0 on success
1247  */
postcopy_place_page_zero(MigrationIncomingState * mis,void * host,RAMBlock * rb)1248 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
1249                              RAMBlock *rb)
1250 {
1251     size_t pagesize = qemu_ram_pagesize(rb);
1252     trace_postcopy_place_page_zero(host);
1253 
1254     /* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE
1255      * but it's not available for everything (e.g. hugetlbpages)
1256      */
1257     if (qemu_ram_is_uf_zeroable(rb)) {
1258         if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, pagesize, rb)) {
1259             int e = errno;
1260             error_report("%s: %s zero host: %p",
1261                          __func__, strerror(e), host);
1262 
1263             return -e;
1264         }
1265         return postcopy_notify_shared_wake(rb,
1266                                            qemu_ram_block_host_offset(rb,
1267                                                                       host));
1268     } else {
1269         return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page, rb);
1270     }
1271 }
1272 
1273 #else
1274 /* No target OS support, stubs just fail */
fill_destination_postcopy_migration_info(MigrationInfo * info)1275 void fill_destination_postcopy_migration_info(MigrationInfo *info)
1276 {
1277 }
1278 
postcopy_ram_supported_by_host(MigrationIncomingState * mis)1279 bool postcopy_ram_supported_by_host(MigrationIncomingState *mis)
1280 {
1281     error_report("%s: No OS support", __func__);
1282     return false;
1283 }
1284 
postcopy_ram_incoming_init(MigrationIncomingState * mis)1285 int postcopy_ram_incoming_init(MigrationIncomingState *mis)
1286 {
1287     error_report("postcopy_ram_incoming_init: No OS support");
1288     return -1;
1289 }
1290 
postcopy_ram_incoming_cleanup(MigrationIncomingState * mis)1291 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
1292 {
1293     assert(0);
1294     return -1;
1295 }
1296 
postcopy_ram_prepare_discard(MigrationIncomingState * mis)1297 int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
1298 {
1299     assert(0);
1300     return -1;
1301 }
1302 
postcopy_request_shared_page(struct PostCopyFD * pcfd,RAMBlock * rb,uint64_t client_addr,uint64_t rb_offset)1303 int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
1304                                  uint64_t client_addr, uint64_t rb_offset)
1305 {
1306     assert(0);
1307     return -1;
1308 }
1309 
postcopy_ram_incoming_setup(MigrationIncomingState * mis)1310 int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
1311 {
1312     assert(0);
1313     return -1;
1314 }
1315 
postcopy_place_page(MigrationIncomingState * mis,void * host,void * from,RAMBlock * rb)1316 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
1317                         RAMBlock *rb)
1318 {
1319     assert(0);
1320     return -1;
1321 }
1322 
postcopy_place_page_zero(MigrationIncomingState * mis,void * host,RAMBlock * rb)1323 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
1324                         RAMBlock *rb)
1325 {
1326     assert(0);
1327     return -1;
1328 }
1329 
postcopy_wake_shared(struct PostCopyFD * pcfd,uint64_t client_addr,RAMBlock * rb)1330 int postcopy_wake_shared(struct PostCopyFD *pcfd,
1331                          uint64_t client_addr,
1332                          RAMBlock *rb)
1333 {
1334     assert(0);
1335     return -1;
1336 }
1337 #endif
1338 
1339 /* ------------------------------------------------------------------------- */
1340 
postcopy_fault_thread_notify(MigrationIncomingState * mis)1341 void postcopy_fault_thread_notify(MigrationIncomingState *mis)
1342 {
1343     uint64_t tmp64 = 1;
1344 
1345     /*
1346      * Wakeup the fault_thread.  It's an eventfd that should currently
1347      * be at 0, we're going to increment it to 1
1348      */
1349     if (write(mis->userfault_event_fd, &tmp64, 8) != 8) {
1350         /* Not much we can do here, but may as well report it */
1351         error_report("%s: incrementing failed: %s", __func__,
1352                      strerror(errno));
1353     }
1354 }
1355 
1356 /**
1357  * postcopy_discard_send_init: Called at the start of each RAMBlock before
1358  *   asking to discard individual ranges.
1359  *
1360  * @ms: The current migration state.
1361  * @offset: the bitmap offset of the named RAMBlock in the migration bitmap.
1362  * @name: RAMBlock that discards will operate on.
1363  */
1364 static PostcopyDiscardState pds = {0};
postcopy_discard_send_init(MigrationState * ms,const char * name)1365 void postcopy_discard_send_init(MigrationState *ms, const char *name)
1366 {
1367     pds.ramblock_name = name;
1368     pds.cur_entry = 0;
1369     pds.nsentwords = 0;
1370     pds.nsentcmds = 0;
1371 }
1372 
1373 /**
1374  * postcopy_discard_send_range: Called by the bitmap code for each chunk to
1375  *   discard. May send a discard message, may just leave it queued to
1376  *   be sent later.
1377  *
1378  * @ms: Current migration state.
1379  * @start,@length: a range of pages in the migration bitmap in the
1380  *   RAM block passed to postcopy_discard_send_init() (length=1 is one page)
1381  */
postcopy_discard_send_range(MigrationState * ms,unsigned long start,unsigned long length)1382 void postcopy_discard_send_range(MigrationState *ms, unsigned long start,
1383                                  unsigned long length)
1384 {
1385     size_t tp_size = qemu_target_page_size();
1386     /* Convert to byte offsets within the RAM block */
1387     pds.start_list[pds.cur_entry] = start  * tp_size;
1388     pds.length_list[pds.cur_entry] = length * tp_size;
1389     trace_postcopy_discard_send_range(pds.ramblock_name, start, length);
1390     pds.cur_entry++;
1391     pds.nsentwords++;
1392 
1393     if (pds.cur_entry == MAX_DISCARDS_PER_COMMAND) {
1394         /* Full set, ship it! */
1395         qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
1396                                               pds.ramblock_name,
1397                                               pds.cur_entry,
1398                                               pds.start_list,
1399                                               pds.length_list);
1400         pds.nsentcmds++;
1401         pds.cur_entry = 0;
1402     }
1403 }
1404 
1405 /**
1406  * postcopy_discard_send_finish: Called at the end of each RAMBlock by the
1407  * bitmap code. Sends any outstanding discard messages, frees the PDS
1408  *
1409  * @ms: Current migration state.
1410  */
postcopy_discard_send_finish(MigrationState * ms)1411 void postcopy_discard_send_finish(MigrationState *ms)
1412 {
1413     /* Anything unsent? */
1414     if (pds.cur_entry) {
1415         qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
1416                                               pds.ramblock_name,
1417                                               pds.cur_entry,
1418                                               pds.start_list,
1419                                               pds.length_list);
1420         pds.nsentcmds++;
1421     }
1422 
1423     trace_postcopy_discard_send_finish(pds.ramblock_name, pds.nsentwords,
1424                                        pds.nsentcmds);
1425 }
1426 
1427 /*
1428  * Current state of incoming postcopy; note this is not part of
1429  * MigrationIncomingState since it's state is used during cleanup
1430  * at the end as MIS is being freed.
1431  */
1432 static PostcopyState incoming_postcopy_state;
1433 
postcopy_state_get(void)1434 PostcopyState  postcopy_state_get(void)
1435 {
1436     return atomic_mb_read(&incoming_postcopy_state);
1437 }
1438 
1439 /* Set the state and return the old state */
postcopy_state_set(PostcopyState new_state)1440 PostcopyState postcopy_state_set(PostcopyState new_state)
1441 {
1442     return atomic_xchg(&incoming_postcopy_state, new_state);
1443 }
1444 
1445 /* Register a handler for external shared memory postcopy
1446  * called on the destination.
1447  */
postcopy_register_shared_ufd(struct PostCopyFD * pcfd)1448 void postcopy_register_shared_ufd(struct PostCopyFD *pcfd)
1449 {
1450     MigrationIncomingState *mis = migration_incoming_get_current();
1451 
1452     mis->postcopy_remote_fds = g_array_append_val(mis->postcopy_remote_fds,
1453                                                   *pcfd);
1454 }
1455 
1456 /* Unregister a handler for external shared memory postcopy
1457  */
postcopy_unregister_shared_ufd(struct PostCopyFD * pcfd)1458 void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd)
1459 {
1460     guint i;
1461     MigrationIncomingState *mis = migration_incoming_get_current();
1462     GArray *pcrfds = mis->postcopy_remote_fds;
1463 
1464     for (i = 0; i < pcrfds->len; i++) {
1465         struct PostCopyFD *cur = &g_array_index(pcrfds, struct PostCopyFD, i);
1466         if (cur->fd == pcfd->fd) {
1467             mis->postcopy_remote_fds = g_array_remove_index(pcrfds, i);
1468             return;
1469         }
1470     }
1471 }
1472