/* * Postcopy migration for RAM * * Copyright 2013-2015 Red Hat, Inc. and/or its affiliates * * Authors: * Dave Gilbert * * This work is licensed under the terms of the GNU GPL, version 2 or later. * See the COPYING file in the top-level directory. * */ /* * Postcopy is a migration technique where the execution flips from the * source to the destination before all the data has been copied. */ #include "qemu/osdep.h" #include "qemu/madvise.h" #include "exec/target_page.h" #include "migration.h" #include "qemu-file.h" #include "savevm.h" #include "postcopy-ram.h" #include "ram.h" #include "qapi/error.h" #include "qemu/notify.h" #include "qemu/rcu.h" #include "system/system.h" #include "qemu/error-report.h" #include "trace.h" #include "hw/boards.h" #include "system/ramblock.h" #include "socket.h" #include "yank_functions.h" #include "tls.h" #include "qemu/userfaultfd.h" #include "qemu/mmap-alloc.h" #include "options.h" /* Arbitrary limit on size of each discard command, * keeps them around ~200 bytes */ #define MAX_DISCARDS_PER_COMMAND 12 typedef struct PostcopyDiscardState { const char *ramblock_name; uint16_t cur_entry; /* * Start and length of a discard range (bytes) */ uint64_t start_list[MAX_DISCARDS_PER_COMMAND]; uint64_t length_list[MAX_DISCARDS_PER_COMMAND]; unsigned int nsentwords; unsigned int nsentcmds; } PostcopyDiscardState; static NotifierWithReturnList postcopy_notifier_list; void postcopy_infrastructure_init(void) { notifier_with_return_list_init(&postcopy_notifier_list); } void postcopy_add_notifier(NotifierWithReturn *nn) { notifier_with_return_list_add(&postcopy_notifier_list, nn); } void postcopy_remove_notifier(NotifierWithReturn *n) { notifier_with_return_remove(n); } int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp) { struct PostcopyNotifyData pnd; pnd.reason = reason; return notifier_with_return_list_notify(&postcopy_notifier_list, &pnd, errp); } /* * NOTE: this routine is not thread safe, we can't call it concurrently. But it * should be good enough for migration's purposes. */ void postcopy_thread_create(MigrationIncomingState *mis, QemuThread *thread, const char *name, void *(*fn)(void *), int joinable) { qemu_event_init(&mis->thread_sync_event, false); qemu_thread_create(thread, name, fn, mis, joinable); qemu_event_wait(&mis->thread_sync_event); qemu_event_destroy(&mis->thread_sync_event); } /* Postcopy needs to detect accesses to pages that haven't yet been copied * across, and efficiently map new pages in, the techniques for doing this * are target OS specific. */ #if defined(__linux__) #include #include #include #endif #if defined(__linux__) && defined(__NR_userfaultfd) && defined(CONFIG_EVENTFD) #include #include /* * Here we use 24 buckets, which means the last bucket will cover [2^24 us, * 2^25 us) ~= [16, 32) seconds. It should be far enough to record even * extreme (perf-wise broken) 1G pages moving over, which can sometimes * take a few seconds due to various reasons. Anything more than that * might be unsensible to account anymore. */ #define BLOCKTIME_LATENCY_BUCKET_N (24) /* All the time records are in unit of nanoseconds */ typedef struct PostcopyBlocktimeContext { /* blocktime per vCPU */ uint64_t *vcpu_blocktime_total; /* count of faults per vCPU */ uint64_t *vcpu_faults_count; /* * count of currently blocked faults per vCPU. * * NOTE: Normally there should only be one fault in-progress per vCPU * thread, so logically it _seems_ vcpu_faults_count[] for any vCPU * should be either zero or one. However, there can be reasons we see * >1 faults on the same vCPU thread. * * CASE (1): since the process to resolve faults (ioctl(UFFDIO_COPY), * for example) is done before taking the mutex that protects the * blocktime context, it can happen that we read more than one faulted * addresses per vCPU. * * One example when we can see >1 faulted addresses for one vCPU: * * vcpu1 thread fault thread resolve thread * ============ ============ ============== * * faulted on addr1 * read uffd msg (addr1) * MUTEX_LOCK * add entry (cpu1, addr1) * MUTEX_UNLOCK * request remote fault (addr1) * resolve fault (addr1) * addr1 resolved, continue.. * faulted on addr2 * read uffd msg (addr2) * MUTEX_LOCK * add entry (cpu1, addr2) <--------------- [A] * MUTEX_UNLOCK * MUTEX_LOCK * remove entry (cpu1, addr1) * MUTEX_UNLOCK * * In above case, we may see (cpu1, addr1) and (cpu1, addr2) entries to * appear together at [A], when it gets the lock before the resolve * thread. Use this counter to maintain such case, and only when it * reaches zero we know the vCPU is not blocked anymore. * * CASE (2): theoretically (the author admit to not have verified * this..), one vCPU thread can also generate more than one userfaultfd * message on the same address. It can happen e.g. for whatever reason * the fault got retried before a resolution arrives. In that extremely * rare case, we could also see two (cpu1, addr1) entries. * * In all cases, be prepared with such re-entrancies with this array. * * Using uint8_t should be far enough for now. For example, when * there're only one resolve thread (postcopy ram listening thread), * the max (concurrent fault entries) should be two. */ uint8_t *vcpu_faults_current; /* * The hash that contains addr1->[(cpu1,ts1),(cpu2,ts2) ...] mappings. * Each of the entry is a tuple of (CPU index, fault timestamp) showing * that a fault was requested. */ GHashTable *vcpu_addr_hash; /* * Each bucket stores the count of faults that were resolved within the * bucket window [2^N us, 2^(N+1) us). */ uint64_t latency_buckets[BLOCKTIME_LATENCY_BUCKET_N]; /* total blocktime when all vCPUs are stopped */ uint64_t total_blocktime; /* point in time when last page fault was initiated */ uint64_t last_begin; /* number of vCPU are suspended */ int smp_cpus_down; /* * Fast path for looking up vcpu_index from tid. NOTE: this result * only reflects the vcpu setup when postcopy is running. It may not * always match with the current vcpu setup because vcpus can be hot * attached/detached after migration completes. However this should be * stable when blocktime is using the structure. */ GHashTable *tid_to_vcpu_hash; /* Count of non-vCPU faults. This is only for debugging purpose. */ uint64_t non_vcpu_faults; /* total blocktime when a non-vCPU thread is stopped */ uint64_t non_vcpu_blocktime_total; /* * Handler for exit event, necessary for * releasing whole blocktime_ctx */ Notifier exit_notifier; } PostcopyBlocktimeContext; typedef struct { /* The time the fault was triggered */ uint64_t fault_time; /* * The vCPU index that was blocked, when cpu==-1, it means it's a * fault from non-vCPU threads. */ int cpu; } BlocktimeVCPUEntry; /* Alloc an entry to record a vCPU fault */ static BlocktimeVCPUEntry * blocktime_vcpu_entry_alloc(int cpu, uint64_t fault_time) { BlocktimeVCPUEntry *entry = g_new(BlocktimeVCPUEntry, 1); entry->fault_time = fault_time; entry->cpu = cpu; return entry; } /* Free a @GList of @BlocktimeVCPUEntry */ static void blocktime_vcpu_list_free(gpointer data) { g_list_free_full(data, g_free); } static void destroy_blocktime_context(struct PostcopyBlocktimeContext *ctx) { g_hash_table_destroy(ctx->tid_to_vcpu_hash); g_hash_table_destroy(ctx->vcpu_addr_hash); g_free(ctx->vcpu_blocktime_total); g_free(ctx->vcpu_faults_count); g_free(ctx->vcpu_faults_current); g_free(ctx); } static void migration_exit_cb(Notifier *n, void *data) { PostcopyBlocktimeContext *ctx = container_of(n, PostcopyBlocktimeContext, exit_notifier); destroy_blocktime_context(ctx); } static GHashTable *blocktime_init_tid_to_vcpu_hash(void) { /* * TID as an unsigned int can be directly used as the key. However, * CPU index can NOT be directly used as value, because CPU index can * be 0, which means NULL. Then when lookup we can never know whether * it's 0 or "not found". Hence use an indirection for CPU index. */ GHashTable *table = g_hash_table_new_full(g_direct_hash, g_direct_equal, NULL, g_free); CPUState *cpu; /* * Initialize the tid->cpu_id mapping for lookups. The caller needs to * make sure when reaching here the CPU topology is frozen and will be * stable for the whole blocktime trapping period. */ CPU_FOREACH(cpu) { int *value = g_new(int, 1); *value = cpu->cpu_index; g_hash_table_insert(table, GUINT_TO_POINTER((uint32_t)cpu->thread_id), value); trace_postcopy_blocktime_tid_cpu_map(cpu->cpu_index, cpu->thread_id); } return table; } static struct PostcopyBlocktimeContext *blocktime_context_new(void) { MachineState *ms = MACHINE(qdev_get_machine()); unsigned int smp_cpus = ms->smp.cpus; PostcopyBlocktimeContext *ctx = g_new0(PostcopyBlocktimeContext, 1); /* Initialize all counters to be zeros */ memset(ctx->latency_buckets, 0, sizeof(ctx->latency_buckets)); ctx->vcpu_blocktime_total = g_new0(uint64_t, smp_cpus); ctx->vcpu_faults_count = g_new0(uint64_t, smp_cpus); ctx->vcpu_faults_current = g_new0(uint8_t, smp_cpus); ctx->tid_to_vcpu_hash = blocktime_init_tid_to_vcpu_hash(); /* * The key (host virtual addresses) will always be gpointer-sized on * either 32bits or 64bits systems, so it'll fit as a direct key. * * The value will be a list of BlocktimeVCPUEntry entries. */ ctx->vcpu_addr_hash = g_hash_table_new_full(g_direct_hash, g_direct_equal, NULL, blocktime_vcpu_list_free); ctx->exit_notifier.notify = migration_exit_cb; qemu_add_exit_notifier(&ctx->exit_notifier); return ctx; } /* * This function just populates MigrationInfo from postcopy's * blocktime context. It will not populate MigrationInfo, * unless postcopy-blocktime capability was set. * * @info: pointer to MigrationInfo to populate */ void fill_destination_postcopy_migration_info(MigrationInfo *info) { MigrationIncomingState *mis = migration_incoming_get_current(); PostcopyBlocktimeContext *bc = mis->blocktime_ctx; MachineState *ms = MACHINE(qdev_get_machine()); uint64_t latency_total = 0, faults = 0; uint32List *list_blocktime = NULL; uint64List *list_latency = NULL; uint64List *latency_buckets = NULL; int i; if (!bc) { return; } for (i = ms->smp.cpus - 1; i >= 0; i--) { uint64_t latency, total, count; /* Convert ns -> ms */ QAPI_LIST_PREPEND(list_blocktime, (uint32_t)(bc->vcpu_blocktime_total[i] / SCALE_MS)); /* The rest in nanoseconds */ total = bc->vcpu_blocktime_total[i]; latency_total += total; count = bc->vcpu_faults_count[i]; faults += count; if (count) { latency = total / count; } else { /* No fault detected */ latency = 0; } QAPI_LIST_PREPEND(list_latency, latency); } for (i = BLOCKTIME_LATENCY_BUCKET_N - 1; i >= 0; i--) { QAPI_LIST_PREPEND(latency_buckets, bc->latency_buckets[i]); } latency_total += bc->non_vcpu_blocktime_total; faults += bc->non_vcpu_faults; info->has_postcopy_non_vcpu_latency = true; info->postcopy_non_vcpu_latency = bc->non_vcpu_faults ? (bc->non_vcpu_blocktime_total / bc->non_vcpu_faults) : 0; info->has_postcopy_blocktime = true; /* Convert ns -> ms */ info->postcopy_blocktime = (uint32_t)(bc->total_blocktime / SCALE_MS); info->has_postcopy_vcpu_blocktime = true; info->postcopy_vcpu_blocktime = list_blocktime; info->has_postcopy_latency = true; info->postcopy_latency = faults ? (latency_total / faults) : 0; info->has_postcopy_vcpu_latency = true; info->postcopy_vcpu_latency = list_latency; info->has_postcopy_latency_dist = true; info->postcopy_latency_dist = latency_buckets; } static uint64_t get_postcopy_total_blocktime(void) { MigrationIncomingState *mis = migration_incoming_get_current(); PostcopyBlocktimeContext *bc = mis->blocktime_ctx; if (!bc) { return 0; } return bc->total_blocktime; } /** * receive_ufd_features: check userfault fd features, to request only supported * features in the future. * * Returns: true on success * * __NR_userfaultfd - should be checked before * @features: out parameter will contain uffdio_api.features provided by kernel * in case of success */ static bool receive_ufd_features(uint64_t *features) { struct uffdio_api api_struct = {0}; int ufd; bool ret = true; ufd = uffd_open(O_CLOEXEC); if (ufd == -1) { error_report("%s: uffd_open() failed: %s", __func__, strerror(errno)); return false; } /* ask features */ api_struct.api = UFFD_API; api_struct.features = 0; if (ioctl(ufd, UFFDIO_API, &api_struct)) { error_report("%s: UFFDIO_API failed: %s", __func__, strerror(errno)); ret = false; goto release_ufd; } *features = api_struct.features; release_ufd: close(ufd); return ret; } /** * request_ufd_features: this function should be called only once on a newly * opened ufd, subsequent calls will lead to error. * * Returns: true on success * * @ufd: fd obtained from userfaultfd syscall * @features: bit mask see UFFD_API_FEATURES */ static bool request_ufd_features(int ufd, uint64_t features) { struct uffdio_api api_struct = {0}; uint64_t ioctl_mask; api_struct.api = UFFD_API; api_struct.features = features; if (ioctl(ufd, UFFDIO_API, &api_struct)) { error_report("%s failed: UFFDIO_API failed: %s", __func__, strerror(errno)); return false; } ioctl_mask = 1ULL << _UFFDIO_REGISTER | 1ULL << _UFFDIO_UNREGISTER; if ((api_struct.ioctls & ioctl_mask) != ioctl_mask) { error_report("Missing userfault features: %" PRIx64, (uint64_t)(~api_struct.ioctls & ioctl_mask)); return false; } return true; } static bool ufd_check_and_apply(int ufd, MigrationIncomingState *mis, Error **errp) { ERRP_GUARD(); uint64_t asked_features = 0; static uint64_t supported_features; /* * it's not possible to * request UFFD_API twice per one fd * userfault fd features is persistent */ if (!supported_features) { if (!receive_ufd_features(&supported_features)) { error_setg(errp, "Userfault feature detection failed"); return false; } } #ifdef UFFD_FEATURE_THREAD_ID /* * Postcopy blocktime conditionally needs THREAD_ID feature (introduced * to Linux in 2017). Always try to enable it when QEMU is compiled * with such environment. */ if (UFFD_FEATURE_THREAD_ID & supported_features) { asked_features |= UFFD_FEATURE_THREAD_ID; } #endif /* * request features, even if asked_features is 0, due to * kernel expects UFFD_API before UFFDIO_REGISTER, per * userfault file descriptor */ if (!request_ufd_features(ufd, asked_features)) { error_setg(errp, "Failed features %" PRIu64, asked_features); return false; } if (qemu_real_host_page_size() != ram_pagesize_summary()) { bool have_hp = false; /* We've got a huge page */ #ifdef UFFD_FEATURE_MISSING_HUGETLBFS have_hp = supported_features & UFFD_FEATURE_MISSING_HUGETLBFS; #endif if (!have_hp) { error_setg(errp, "Userfault on this host does not support huge pages"); return false; } } return true; } /* Callback from postcopy_ram_supported_by_host block iterator. */ static int test_ramblock_postcopiable(RAMBlock *rb, Error **errp) { const char *block_name = qemu_ram_get_idstr(rb); ram_addr_t length = qemu_ram_get_used_length(rb); size_t pagesize = qemu_ram_pagesize(rb); QemuFsType fs; if (length % pagesize) { error_setg(errp, "Postcopy requires RAM blocks to be a page size multiple," " block %s is 0x" RAM_ADDR_FMT " bytes with a " "page size of 0x%zx", block_name, length, pagesize); return 1; } if (rb->fd >= 0) { fs = qemu_fd_getfs(rb->fd); if (fs != QEMU_FS_TYPE_TMPFS && fs != QEMU_FS_TYPE_HUGETLBFS) { error_setg(errp, "Host backend files need to be TMPFS or HUGETLBFS only"); return 1; } } return 0; } /* * Note: This has the side effect of munlock'ing all of RAM, that's * normally fine since if the postcopy succeeds it gets turned back on at the * end. */ bool postcopy_ram_supported_by_host(MigrationIncomingState *mis, Error **errp) { ERRP_GUARD(); long pagesize = qemu_real_host_page_size(); int ufd = -1; bool ret = false; /* Error unless we change it */ void *testarea = NULL; struct uffdio_register reg_struct; struct uffdio_range range_struct; uint64_t feature_mask; RAMBlock *block; if (qemu_target_page_size() > pagesize) { error_setg(errp, "Target page size bigger than host page size"); goto out; } ufd = uffd_open(O_CLOEXEC); if (ufd == -1) { error_setg(errp, "Userfaultfd not available: %s", strerror(errno)); goto out; } /* Give devices a chance to object */ if (postcopy_notify(POSTCOPY_NOTIFY_PROBE, errp)) { goto out; } /* Version and features check */ if (!ufd_check_and_apply(ufd, mis, errp)) { goto out; } /* * We don't support postcopy with some type of ramblocks. * * NOTE: we explicitly ignored migrate_ram_is_ignored() instead we checked * all possible ramblocks. This is because this function can be called * when creating the migration object, during the phase RAM_MIGRATABLE * is not even properly set for all the ramblocks. * * A side effect of this is we'll also check against RAM_SHARED * ramblocks even if migrate_ignore_shared() is set (in which case * we'll never migrate RAM_SHARED at all), but normally this shouldn't * affect in reality, or we can revisit. */ RAMBLOCK_FOREACH(block) { if (test_ramblock_postcopiable(block, errp)) { goto out; } } /* * userfault and mlock don't go together; we'll put it back later if * it was enabled. */ if (munlockall()) { error_setg(errp, "munlockall() failed: %s", strerror(errno)); goto out; } /* * We need to check that the ops we need are supported on anon memory * To do that we need to register a chunk and see the flags that * are returned. */ testarea = mmap(NULL, pagesize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (testarea == MAP_FAILED) { error_setg(errp, "Failed to map test area: %s", strerror(errno)); goto out; } g_assert(QEMU_PTR_IS_ALIGNED(testarea, pagesize)); reg_struct.range.start = (uintptr_t)testarea; reg_struct.range.len = pagesize; reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING; if (ioctl(ufd, UFFDIO_REGISTER, ®_struct)) { error_setg(errp, "UFFDIO_REGISTER failed: %s", strerror(errno)); goto out; } range_struct.start = (uintptr_t)testarea; range_struct.len = pagesize; if (ioctl(ufd, UFFDIO_UNREGISTER, &range_struct)) { error_setg(errp, "UFFDIO_UNREGISTER failed: %s", strerror(errno)); goto out; } feature_mask = 1ULL << _UFFDIO_WAKE | 1ULL << _UFFDIO_COPY | 1ULL << _UFFDIO_ZEROPAGE; if ((reg_struct.ioctls & feature_mask) != feature_mask) { error_setg(errp, "Missing userfault map features: %" PRIx64, (uint64_t)(~reg_struct.ioctls & feature_mask)); goto out; } /* Success! */ ret = true; out: if (testarea) { munmap(testarea, pagesize); } if (ufd != -1) { close(ufd); } return ret; } /* * Setup an area of RAM so that it *can* be used for postcopy later; this * must be done right at the start prior to pre-copy. * opaque should be the MIS. */ static int init_range(RAMBlock *rb, void *opaque) { const char *block_name = qemu_ram_get_idstr(rb); void *host_addr = qemu_ram_get_host_addr(rb); ram_addr_t offset = qemu_ram_get_offset(rb); ram_addr_t length = qemu_ram_get_used_length(rb); trace_postcopy_init_range(block_name, host_addr, offset, length); /* * Save the used_length before running the guest. In case we have to * resize RAM blocks when syncing RAM block sizes from the source during * precopy, we'll update it manually via the ram block notifier. */ rb->postcopy_length = length; /* * We need the whole of RAM to be truly empty for postcopy, so things * like ROMs and any data tables built during init must be zero'd * - we're going to get the copy from the source anyway. * (Precopy will just overwrite this data, so doesn't need the discard) */ if (ram_discard_range(block_name, 0, length)) { return -1; } return 0; } /* * At the end of migration, undo the effects of init_range * opaque should be the MIS. */ static int cleanup_range(RAMBlock *rb, void *opaque) { const char *block_name = qemu_ram_get_idstr(rb); void *host_addr = qemu_ram_get_host_addr(rb); ram_addr_t offset = qemu_ram_get_offset(rb); ram_addr_t length = rb->postcopy_length; MigrationIncomingState *mis = opaque; struct uffdio_range range_struct; trace_postcopy_cleanup_range(block_name, host_addr, offset, length); /* * We turned off hugepage for the precopy stage with postcopy enabled * we can turn it back on now. */ qemu_madvise(host_addr, length, QEMU_MADV_HUGEPAGE); /* * We can also turn off userfault now since we should have all the * pages. It can be useful to leave it on to debug postcopy * if you're not sure it's always getting every page. */ range_struct.start = (uintptr_t)host_addr; range_struct.len = length; if (ioctl(mis->userfault_fd, UFFDIO_UNREGISTER, &range_struct)) { error_report("%s: userfault unregister %s", __func__, strerror(errno)); return -1; } return 0; } /* * Initialise postcopy-ram, setting the RAM to a state where we can go into * postcopy later; must be called prior to any precopy. * called from arch_init's similarly named ram_postcopy_incoming_init */ int postcopy_ram_incoming_init(MigrationIncomingState *mis) { if (foreach_not_ignored_block(init_range, NULL)) { return -1; } return 0; } static void postcopy_temp_pages_cleanup(MigrationIncomingState *mis) { int i; if (mis->postcopy_tmp_pages) { for (i = 0; i < mis->postcopy_channels; i++) { if (mis->postcopy_tmp_pages[i].tmp_huge_page) { munmap(mis->postcopy_tmp_pages[i].tmp_huge_page, mis->largest_page_size); mis->postcopy_tmp_pages[i].tmp_huge_page = NULL; } } g_free(mis->postcopy_tmp_pages); mis->postcopy_tmp_pages = NULL; } if (mis->postcopy_tmp_zero_page) { munmap(mis->postcopy_tmp_zero_page, mis->largest_page_size); mis->postcopy_tmp_zero_page = NULL; } } /* * At the end of a migration where postcopy_ram_incoming_init was called. */ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis) { trace_postcopy_ram_incoming_cleanup_entry(); if (mis->preempt_thread_status == PREEMPT_THREAD_CREATED) { /* Notify the fast load thread to quit */ mis->preempt_thread_status = PREEMPT_THREAD_QUIT; /* * Update preempt_thread_status before reading count. Note: mutex * lock only provide ACQUIRE semantic, and it doesn't stops this * write to be reordered after reading the count. */ smp_mb(); /* * It's possible that the preempt thread is still handling the last * pages to arrive which were requested by guest page faults. * Making sure nothing is left behind by waiting on the condvar if * that unlikely case happened. */ WITH_QEMU_LOCK_GUARD(&mis->page_request_mutex) { if (qatomic_read(&mis->page_requested_count)) { /* * It is guaranteed to receive a signal later, because the * count>0 now, so it's destined to be decreased to zero * very soon by the preempt thread. */ qemu_cond_wait(&mis->page_request_cond, &mis->page_request_mutex); } } /* Notify the fast load thread to quit */ if (mis->postcopy_qemufile_dst) { qemu_file_shutdown(mis->postcopy_qemufile_dst); } qemu_thread_join(&mis->postcopy_prio_thread); mis->preempt_thread_status = PREEMPT_THREAD_NONE; } if (mis->have_fault_thread) { Error *local_err = NULL; /* Let the fault thread quit */ qatomic_set(&mis->fault_thread_quit, 1); postcopy_fault_thread_notify(mis); trace_postcopy_ram_incoming_cleanup_join(); qemu_thread_join(&mis->fault_thread); if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_END, &local_err)) { error_report_err(local_err); return -1; } if (foreach_not_ignored_block(cleanup_range, mis)) { return -1; } trace_postcopy_ram_incoming_cleanup_closeuf(); close(mis->userfault_fd); close(mis->userfault_event_fd); mis->have_fault_thread = false; } if (should_mlock(mlock_state)) { if (os_mlock(is_mlock_on_fault(mlock_state)) < 0) { error_report("mlock: %s", strerror(errno)); /* * It doesn't feel right to fail at this point, we have a valid * VM state. */ } } postcopy_temp_pages_cleanup(mis); trace_postcopy_ram_incoming_cleanup_blocktime( get_postcopy_total_blocktime()); trace_postcopy_ram_incoming_cleanup_exit(); return 0; } /* * Disable huge pages on an area */ static int nhp_range(RAMBlock *rb, void *opaque) { const char *block_name = qemu_ram_get_idstr(rb); void *host_addr = qemu_ram_get_host_addr(rb); ram_addr_t offset = qemu_ram_get_offset(rb); ram_addr_t length = rb->postcopy_length; trace_postcopy_nhp_range(block_name, host_addr, offset, length); /* * Before we do discards we need to ensure those discards really * do delete areas of the page, even if THP thinks a hugepage would * be a good idea, so force hugepages off. */ qemu_madvise(host_addr, length, QEMU_MADV_NOHUGEPAGE); return 0; } /* * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard * however leaving it until after precopy means that most of the precopy * data is still THPd */ int postcopy_ram_prepare_discard(MigrationIncomingState *mis) { if (foreach_not_ignored_block(nhp_range, mis)) { return -1; } postcopy_state_set(POSTCOPY_INCOMING_DISCARD); return 0; } /* * Mark the given area of RAM as requiring notification to unwritten areas * Used as a callback on foreach_not_ignored_block. * host_addr: Base of area to mark * offset: Offset in the whole ram arena * length: Length of the section * opaque: MigrationIncomingState pointer * Returns 0 on success */ static int ram_block_enable_notify(RAMBlock *rb, void *opaque) { MigrationIncomingState *mis = opaque; struct uffdio_register reg_struct; reg_struct.range.start = (uintptr_t)qemu_ram_get_host_addr(rb); reg_struct.range.len = rb->postcopy_length; reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING; /* Now tell our userfault_fd that it's responsible for this area */ if (ioctl(mis->userfault_fd, UFFDIO_REGISTER, ®_struct)) { error_report("%s userfault register: %s", __func__, strerror(errno)); return -1; } if (!(reg_struct.ioctls & (1ULL << _UFFDIO_COPY))) { error_report("%s userfault: Region doesn't support COPY", __func__); return -1; } if (reg_struct.ioctls & (1ULL << _UFFDIO_ZEROPAGE)) { qemu_ram_set_uf_zeroable(rb); } return 0; } int postcopy_wake_shared(struct PostCopyFD *pcfd, uint64_t client_addr, RAMBlock *rb) { size_t pagesize = qemu_ram_pagesize(rb); trace_postcopy_wake_shared(client_addr, qemu_ram_get_idstr(rb)); return uffd_wakeup(pcfd->fd, (void *)(uintptr_t)ROUND_DOWN(client_addr, pagesize), pagesize); } /* * NOTE: @tid is only used when postcopy-blocktime feature is enabled, and * also optional: when zero is provided, the fault accounting will be ignored. */ static int postcopy_request_page(MigrationIncomingState *mis, RAMBlock *rb, ram_addr_t start, uint64_t haddr, uint32_t tid) { void *aligned = (void *)(uintptr_t)ROUND_DOWN(haddr, qemu_ram_pagesize(rb)); /* * Discarded pages (via RamDiscardManager) are never migrated. On unlikely * access, place a zeropage, which will also set the relevant bits in the * recv_bitmap accordingly, so we won't try placing a zeropage twice. * * Checking a single bit is sufficient to handle pagesize > TPS as either * all relevant bits are set or not. */ assert(QEMU_IS_ALIGNED(start, qemu_ram_pagesize(rb))); if (ramblock_page_is_discarded(rb, start)) { bool received = ramblock_recv_bitmap_test_byte_offset(rb, start); return received ? 0 : postcopy_place_page_zero(mis, aligned, rb); } return migrate_send_rp_req_pages(mis, rb, start, haddr, tid); } /* * Callback from shared fault handlers to ask for a page, * the page must be specified by a RAMBlock and an offset in that rb * Note: Only for use by shared fault handlers (in fault thread) */ int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb, uint64_t client_addr, uint64_t rb_offset) { uint64_t aligned_rbo = ROUND_DOWN(rb_offset, qemu_ram_pagesize(rb)); MigrationIncomingState *mis = migration_incoming_get_current(); trace_postcopy_request_shared_page(pcfd->idstr, qemu_ram_get_idstr(rb), rb_offset); if (ramblock_recv_bitmap_test_byte_offset(rb, aligned_rbo)) { trace_postcopy_request_shared_page_present(pcfd->idstr, qemu_ram_get_idstr(rb), rb_offset); return postcopy_wake_shared(pcfd, client_addr, rb); } /* TODO: support blocktime tracking */ postcopy_request_page(mis, rb, aligned_rbo, client_addr, 0); return 0; } static int blocktime_get_vcpu(PostcopyBlocktimeContext *ctx, uint32_t tid) { int *found; found = g_hash_table_lookup(ctx->tid_to_vcpu_hash, GUINT_TO_POINTER(tid)); if (!found) { /* * NOTE: this is possible, because QEMU's non-vCPU threads can * also access a missing page. Or, when KVM async pf is enabled, a * fault can even happen from a kworker.. */ return -1; } return *found; } static uint64_t get_current_ns(void) { return (uint64_t)qemu_clock_get_ns(QEMU_CLOCK_REALTIME); } /* * Inject an (cpu, fault_time) entry into the database, using addr as key. * When cpu==-1, it means it's a non-vCPU fault. */ static void blocktime_fault_inject(PostcopyBlocktimeContext *ctx, uintptr_t addr, int cpu, uint64_t time) { BlocktimeVCPUEntry *entry = blocktime_vcpu_entry_alloc(cpu, time); GHashTable *table = ctx->vcpu_addr_hash; gpointer key = (gpointer)addr; GList *head, *list; gboolean result; head = g_hash_table_lookup(table, key); if (head) { /* * If existed, steal the @head for list operation rather than * freeing it, making sure steal succeeded. */ result = g_hash_table_steal(table, key); assert(result == TRUE); } /* * Now the key is guaranteed to be absent. Two cases: * * (1) There's no existing entry, list contains the only one. Insert. * (2) There're existing entries, after stealing we own it, prepend the * result and re-insert. */ list = g_list_prepend(head, entry); g_hash_table_insert(table, key, list); trace_postcopy_blocktime_begin(addr, time, cpu, !!head); } /* * This function is being called when pagefault occurs. It tracks down vCPU * blocking time. It's protected by @page_request_mutex. * * @addr: faulted host virtual address * @ptid: faulted process thread id * @rb: ramblock appropriate to addr */ void mark_postcopy_blocktime_begin(uintptr_t addr, uint32_t ptid, RAMBlock *rb) { int cpu; MigrationIncomingState *mis = migration_incoming_get_current(); PostcopyBlocktimeContext *dc = mis->blocktime_ctx; uint64_t current; if (!dc || ptid == 0) { return; } /* * The caller should only inject a blocktime entry when the page is * yet missing. */ assert(!ramblock_recv_bitmap_test(rb, (void *)addr)); current = get_current_ns(); cpu = blocktime_get_vcpu(dc, ptid); if (cpu >= 0) { /* How many faults on this vCPU in total? */ dc->vcpu_faults_count[cpu]++; /* * Account how many concurrent faults on this vCPU we trapped. See * comments above vcpu_faults_current[] on why it can be more than one. */ if (dc->vcpu_faults_current[cpu]++ == 0) { dc->smp_cpus_down++; /* * We use last_begin to cover (1) the 1st fault on this specific * vCPU, but meanwhile (2) the last vCPU that got blocked. It's * only used to calculate system-wide blocktime. */ dc->last_begin = current; } /* Making sure it won't overflow - it really should never! */ assert(dc->vcpu_faults_current[cpu] <= 255); } else { /* * For non-vCPU thread faults, we don't care about tid or cpu index * or time the thread is blocked (e.g., a kworker trying to help * KVM when async_pf=on is OK to be blocked and not affect guest * responsiveness), but we care about latency. Track it with * cpu=-1. * * Note that this will NOT affect blocktime reports on vCPU being * blocked, but only about system-wide latency reports. */ dc->non_vcpu_faults++; } blocktime_fault_inject(dc, addr, cpu, current); } static void blocktime_latency_account(PostcopyBlocktimeContext *ctx, uint64_t time_us) { /* * Convert time (in us) to bucket index it belongs. Take extra caution * of time_us==0 even if normally rare - when happens put into bucket 0. */ int index = time_us ? (63 - clz64(time_us)) : 0; assert(index >= 0); /* If it's too large, put into top bucket */ if (index >= BLOCKTIME_LATENCY_BUCKET_N) { index = BLOCKTIME_LATENCY_BUCKET_N - 1; } ctx->latency_buckets[index]++; } typedef struct { PostcopyBlocktimeContext *ctx; uint64_t current; int affected_cpus; int affected_non_cpus; } BlockTimeVCPUIter; static void blocktime_cpu_list_iter_fn(gpointer data, gpointer user_data) { BlockTimeVCPUIter *iter = user_data; PostcopyBlocktimeContext *ctx = iter->ctx; BlocktimeVCPUEntry *entry = data; uint64_t time_passed; int cpu = entry->cpu; /* * Time should never go back.. so when the fault is resolved it must be * later than when it was faulted. */ assert(iter->current >= entry->fault_time); time_passed = iter->current - entry->fault_time; /* Latency buckets are in microseconds */ blocktime_latency_account(ctx, time_passed / SCALE_US); if (cpu >= 0) { /* * If we resolved all pending faults on one vCPU due to this page * resolution, take a note. */ if (--ctx->vcpu_faults_current[cpu] == 0) { ctx->vcpu_blocktime_total[cpu] += time_passed; iter->affected_cpus += 1; } trace_postcopy_blocktime_end_one(cpu, ctx->vcpu_faults_current[cpu]); } else { iter->affected_non_cpus++; ctx->non_vcpu_blocktime_total += time_passed; /* * We do not maintain how many pending non-vCPU faults because we * do not care about blocktime, only latency. */ trace_postcopy_blocktime_end_one(-1, 0); } } /* * This function just provide calculated blocktime per cpu and trace it. * Total blocktime is calculated in mark_postcopy_blocktime_end. It's * protected by @page_request_mutex. * * Assume we have 3 CPU * * S1 E1 S1 E1 * -----***********------------xxx***************------------------------> CPU1 * * S2 E2 * ------------****************xxx---------------------------------------> CPU2 * * S3 E3 * ------------------------****xxx********-------------------------------> CPU3 * * We have sequence S1,S2,E1,S3,S1,E2,E3,E1 * S2,E1 - doesn't match condition due to sequence S1,S2,E1 doesn't include CPU3 * S3,S1,E2 - sequence includes all CPUs, in this case overlap will be S1,E2 - * it's a part of total blocktime. * S1 - here is last_begin * Legend of the picture is following: * * - means blocktime per vCPU * x - means overlapped blocktime (total blocktime) * * @addr: host virtual address */ static void mark_postcopy_blocktime_end(uintptr_t addr) { MigrationIncomingState *mis = migration_incoming_get_current(); PostcopyBlocktimeContext *dc = mis->blocktime_ctx; MachineState *ms = MACHINE(qdev_get_machine()); unsigned int smp_cpus = ms->smp.cpus; BlockTimeVCPUIter iter = { .current = get_current_ns(), .affected_cpus = 0, .affected_non_cpus = 0, .ctx = dc, }; gpointer key = (gpointer)addr; GHashTable *table; GList *list; if (!dc) { return; } table = dc->vcpu_addr_hash; /* the address wasn't tracked at all? */ list = g_hash_table_lookup(table, key); if (!list) { return; } /* * Loop over the set of vCPUs that got blocked on this addr, do the * blocktime accounting. After that, remove the whole list. */ g_list_foreach(list, blocktime_cpu_list_iter_fn, &iter); g_hash_table_remove(table, key); /* * If all vCPUs used to be down, and copying this page would free some * vCPUs, then the system-level blocktime ends here. */ if (dc->smp_cpus_down == smp_cpus && iter.affected_cpus) { dc->total_blocktime += iter.current - dc->last_begin; } dc->smp_cpus_down -= iter.affected_cpus; trace_postcopy_blocktime_end(addr, iter.current, iter.affected_cpus, iter.affected_non_cpus); } static void postcopy_pause_fault_thread(MigrationIncomingState *mis) { trace_postcopy_pause_fault_thread(); qemu_sem_wait(&mis->postcopy_pause_sem_fault); trace_postcopy_pause_fault_thread_continued(); } /* * Handle faults detected by the USERFAULT markings */ static void *postcopy_ram_fault_thread(void *opaque) { MigrationIncomingState *mis = opaque; struct uffd_msg msg; int ret; size_t index; RAMBlock *rb = NULL; trace_postcopy_ram_fault_thread_entry(); rcu_register_thread(); mis->last_rb = NULL; /* last RAMBlock we sent part of */ qemu_event_set(&mis->thread_sync_event); struct pollfd *pfd; size_t pfd_len = 2 + mis->postcopy_remote_fds->len; pfd = g_new0(struct pollfd, pfd_len); pfd[0].fd = mis->userfault_fd; pfd[0].events = POLLIN; pfd[1].fd = mis->userfault_event_fd; pfd[1].events = POLLIN; /* Waiting for eventfd to go positive */ trace_postcopy_ram_fault_thread_fds_core(pfd[0].fd, pfd[1].fd); for (index = 0; index < mis->postcopy_remote_fds->len; index++) { struct PostCopyFD *pcfd = &g_array_index(mis->postcopy_remote_fds, struct PostCopyFD, index); pfd[2 + index].fd = pcfd->fd; pfd[2 + index].events = POLLIN; trace_postcopy_ram_fault_thread_fds_extra(2 + index, pcfd->idstr, pcfd->fd); } while (true) { ram_addr_t rb_offset; int poll_result; /* * We're mainly waiting for the kernel to give us a faulting HVA, * however we can be told to quit via userfault_quit_fd which is * an eventfd */ poll_result = poll(pfd, pfd_len, -1 /* Wait forever */); if (poll_result == -1) { error_report("%s: userfault poll: %s", __func__, strerror(errno)); break; } if (!mis->to_src_file) { /* * Possibly someone tells us that the return path is * broken already using the event. We should hold until * the channel is rebuilt. */ postcopy_pause_fault_thread(mis); } if (pfd[1].revents) { uint64_t tmp64 = 0; /* Consume the signal */ if (read(mis->userfault_event_fd, &tmp64, 8) != 8) { /* Nothing obviously nicer than posting this error. */ error_report("%s: read() failed", __func__); } if (qatomic_read(&mis->fault_thread_quit)) { trace_postcopy_ram_fault_thread_quit(); break; } } if (pfd[0].revents) { poll_result--; ret = read(mis->userfault_fd, &msg, sizeof(msg)); if (ret != sizeof(msg)) { if (errno == EAGAIN) { /* * if a wake up happens on the other thread just after * the poll, there is nothing to read. */ continue; } if (ret < 0) { error_report("%s: Failed to read full userfault " "message: %s", __func__, strerror(errno)); break; } else { error_report("%s: Read %d bytes from userfaultfd " "expected %zd", __func__, ret, sizeof(msg)); break; /* Lost alignment, don't know what we'd read next */ } } if (msg.event != UFFD_EVENT_PAGEFAULT) { error_report("%s: Read unexpected event %ud from userfaultfd", __func__, msg.event); continue; /* It's not a page fault, shouldn't happen */ } rb = qemu_ram_block_from_host( (void *)(uintptr_t)msg.arg.pagefault.address, true, &rb_offset); if (!rb) { error_report("postcopy_ram_fault_thread: Fault outside guest: %" PRIx64, (uint64_t)msg.arg.pagefault.address); break; } rb_offset = ROUND_DOWN(rb_offset, qemu_ram_pagesize(rb)); trace_postcopy_ram_fault_thread_request(msg.arg.pagefault.address, qemu_ram_get_idstr(rb), rb_offset, msg.arg.pagefault.feat.ptid); retry: /* * Send the request to the source - we want to request one * of our host page sizes (which is >= TPS) */ ret = postcopy_request_page(mis, rb, rb_offset, msg.arg.pagefault.address, msg.arg.pagefault.feat.ptid); if (ret) { /* May be network failure, try to wait for recovery */ postcopy_pause_fault_thread(mis); goto retry; } } /* Now handle any requests from external processes on shared memory */ /* TODO: May need to handle devices deregistering during postcopy */ for (index = 2; index < pfd_len && poll_result; index++) { if (pfd[index].revents) { struct PostCopyFD *pcfd = &g_array_index(mis->postcopy_remote_fds, struct PostCopyFD, index - 2); poll_result--; if (pfd[index].revents & POLLERR) { error_report("%s: POLLERR on poll %zd fd=%d", __func__, index, pcfd->fd); pfd[index].events = 0; continue; } ret = read(pcfd->fd, &msg, sizeof(msg)); if (ret != sizeof(msg)) { if (errno == EAGAIN) { /* * if a wake up happens on the other thread just after * the poll, there is nothing to read. */ continue; } if (ret < 0) { error_report("%s: Failed to read full userfault " "message: %s (shared) revents=%d", __func__, strerror(errno), pfd[index].revents); /*TODO: Could just disable this sharer */ break; } else { error_report("%s: Read %d bytes from userfaultfd " "expected %zd (shared)", __func__, ret, sizeof(msg)); /*TODO: Could just disable this sharer */ break; /*Lost alignment,don't know what we'd read next*/ } } if (msg.event != UFFD_EVENT_PAGEFAULT) { error_report("%s: Read unexpected event %ud " "from userfaultfd (shared)", __func__, msg.event); continue; /* It's not a page fault, shouldn't happen */ } /* Call the device handler registered with us */ ret = pcfd->handler(pcfd, &msg); if (ret) { error_report("%s: Failed to resolve shared fault on %zd/%s", __func__, index, pcfd->idstr); /* TODO: Fail? Disable this sharer? */ } } } } rcu_unregister_thread(); trace_postcopy_ram_fault_thread_exit(); g_free(pfd); return NULL; } static int postcopy_temp_pages_setup(MigrationIncomingState *mis) { PostcopyTmpPage *tmp_page; int err, i, channels; void *temp_page; if (migrate_postcopy_preempt()) { /* If preemption enabled, need extra channel for urgent requests */ mis->postcopy_channels = RAM_CHANNEL_MAX; } else { /* Both precopy/postcopy on the same channel */ mis->postcopy_channels = 1; } channels = mis->postcopy_channels; mis->postcopy_tmp_pages = g_malloc0_n(sizeof(PostcopyTmpPage), channels); for (i = 0; i < channels; i++) { tmp_page = &mis->postcopy_tmp_pages[i]; temp_page = mmap(NULL, mis->largest_page_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (temp_page == MAP_FAILED) { err = errno; error_report("%s: Failed to map postcopy_tmp_pages[%d]: %s", __func__, i, strerror(err)); /* Clean up will be done later */ return -err; } tmp_page->tmp_huge_page = temp_page; /* Initialize default states for each tmp page */ postcopy_temp_page_reset(tmp_page); } /* * Map large zero page when kernel can't use UFFDIO_ZEROPAGE for hugepages */ mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (mis->postcopy_tmp_zero_page == MAP_FAILED) { err = errno; mis->postcopy_tmp_zero_page = NULL; error_report("%s: Failed to map large zero page %s", __func__, strerror(err)); return -err; } memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size); return 0; } int postcopy_ram_incoming_setup(MigrationIncomingState *mis) { Error *local_err = NULL; /* Open the fd for the kernel to give us userfaults */ mis->userfault_fd = uffd_open(O_CLOEXEC | O_NONBLOCK); if (mis->userfault_fd == -1) { error_report("%s: Failed to open userfault fd: %s", __func__, strerror(errno)); return -1; } /* * Although the host check already tested the API, we need to * do the check again as an ABI handshake on the new fd. */ if (!ufd_check_and_apply(mis->userfault_fd, mis, &local_err)) { error_report_err(local_err); return -1; } if (migrate_postcopy_blocktime()) { assert(mis->blocktime_ctx == NULL); mis->blocktime_ctx = blocktime_context_new(); } /* Now an eventfd we use to tell the fault-thread to quit */ mis->userfault_event_fd = eventfd(0, EFD_CLOEXEC); if (mis->userfault_event_fd == -1) { error_report("%s: Opening userfault_event_fd: %s", __func__, strerror(errno)); close(mis->userfault_fd); return -1; } postcopy_thread_create(mis, &mis->fault_thread, MIGRATION_THREAD_DST_FAULT, postcopy_ram_fault_thread, QEMU_THREAD_JOINABLE); mis->have_fault_thread = true; /* Mark so that we get notified of accesses to unwritten areas */ if (foreach_not_ignored_block(ram_block_enable_notify, mis)) { error_report("ram_block_enable_notify failed"); return -1; } if (postcopy_temp_pages_setup(mis)) { /* Error dumped in the sub-function */ return -1; } if (migrate_postcopy_preempt()) { /* * This thread needs to be created after the temp pages because * it'll fetch RAM_CHANNEL_POSTCOPY PostcopyTmpPage immediately. */ postcopy_thread_create(mis, &mis->postcopy_prio_thread, MIGRATION_THREAD_DST_PREEMPT, postcopy_preempt_thread, QEMU_THREAD_JOINABLE); mis->preempt_thread_status = PREEMPT_THREAD_CREATED; } trace_postcopy_ram_enable_notify(); return 0; } static int qemu_ufd_copy_ioctl(MigrationIncomingState *mis, void *host_addr, void *from_addr, uint64_t pagesize, RAMBlock *rb) { int userfault_fd = mis->userfault_fd; int ret; if (from_addr) { ret = uffd_copy_page(userfault_fd, host_addr, from_addr, pagesize, false); } else { ret = uffd_zero_page(userfault_fd, host_addr, pagesize, false); } if (!ret) { qemu_mutex_lock(&mis->page_request_mutex); ramblock_recv_bitmap_set_range(rb, host_addr, pagesize / qemu_target_page_size()); /* * If this page resolves a page fault for a previous recorded faulted * address, take a special note to maintain the requested page list. */ if (g_tree_lookup(mis->page_requested, host_addr)) { g_tree_remove(mis->page_requested, host_addr); int left_pages = qatomic_dec_fetch(&mis->page_requested_count); trace_postcopy_page_req_del(host_addr, mis->page_requested_count); /* Order the update of count and read of preempt status */ smp_mb(); if (mis->preempt_thread_status == PREEMPT_THREAD_QUIT && left_pages == 0) { /* * This probably means the main thread is waiting for us. * Notify that we've finished receiving the last requested * page. */ qemu_cond_signal(&mis->page_request_cond); } } mark_postcopy_blocktime_end((uintptr_t)host_addr); qemu_mutex_unlock(&mis->page_request_mutex); } return ret; } int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset) { int i; MigrationIncomingState *mis = migration_incoming_get_current(); GArray *pcrfds = mis->postcopy_remote_fds; for (i = 0; i < pcrfds->len; i++) { struct PostCopyFD *cur = &g_array_index(pcrfds, struct PostCopyFD, i); int ret = cur->waker(cur, rb, offset); if (ret) { return ret; } } return 0; } /* * Place a host page (from) at (host) atomically * returns 0 on success */ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, RAMBlock *rb) { size_t pagesize = qemu_ram_pagesize(rb); int e; /* copy also acks to the kernel waking the stalled thread up * TODO: We can inhibit that ack and only do it if it was requested * which would be slightly cheaper, but we'd have to be careful * of the order of updating our page state. */ e = qemu_ufd_copy_ioctl(mis, host, from, pagesize, rb); if (e) { return e; } trace_postcopy_place_page(host); return postcopy_notify_shared_wake(rb, qemu_ram_block_host_offset(rb, host)); } /* * Place a zero page at (host) atomically * returns 0 on success */ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, RAMBlock *rb) { size_t pagesize = qemu_ram_pagesize(rb); trace_postcopy_place_page_zero(host); /* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE * but it's not available for everything (e.g. hugetlbpages) */ if (qemu_ram_is_uf_zeroable(rb)) { int e; e = qemu_ufd_copy_ioctl(mis, host, NULL, pagesize, rb); if (e) { return e; } return postcopy_notify_shared_wake(rb, qemu_ram_block_host_offset(rb, host)); } else { return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page, rb); } } #else /* No target OS support, stubs just fail */ void fill_destination_postcopy_migration_info(MigrationInfo *info) { } bool postcopy_ram_supported_by_host(MigrationIncomingState *mis, Error **errp) { error_report("%s: No OS support", __func__); return false; } int postcopy_ram_incoming_init(MigrationIncomingState *mis) { error_report("postcopy_ram_incoming_init: No OS support"); return -1; } int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis) { g_assert_not_reached(); } int postcopy_ram_prepare_discard(MigrationIncomingState *mis) { g_assert_not_reached(); } int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb, uint64_t client_addr, uint64_t rb_offset) { g_assert_not_reached(); } int postcopy_ram_incoming_setup(MigrationIncomingState *mis) { g_assert_not_reached(); } int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, RAMBlock *rb) { g_assert_not_reached(); } int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, RAMBlock *rb) { g_assert_not_reached(); } int postcopy_wake_shared(struct PostCopyFD *pcfd, uint64_t client_addr, RAMBlock *rb) { g_assert_not_reached(); } void mark_postcopy_blocktime_begin(uintptr_t addr, uint32_t ptid, RAMBlock *rb) { } #endif /* ------------------------------------------------------------------------- */ void postcopy_temp_page_reset(PostcopyTmpPage *tmp_page) { tmp_page->target_pages = 0; tmp_page->host_addr = NULL; /* * This is set to true when reset, and cleared as long as we received any * of the non-zero small page within this huge page. */ tmp_page->all_zero = true; } void postcopy_fault_thread_notify(MigrationIncomingState *mis) { uint64_t tmp64 = 1; /* * Wakeup the fault_thread. It's an eventfd that should currently * be at 0, we're going to increment it to 1 */ if (write(mis->userfault_event_fd, &tmp64, 8) != 8) { /* Not much we can do here, but may as well report it */ error_report("%s: incrementing failed: %s", __func__, strerror(errno)); } } /** * postcopy_discard_send_init: Called at the start of each RAMBlock before * asking to discard individual ranges. * * @ms: The current migration state. * @offset: the bitmap offset of the named RAMBlock in the migration bitmap. * @name: RAMBlock that discards will operate on. */ static PostcopyDiscardState pds = {0}; void postcopy_discard_send_init(MigrationState *ms, const char *name) { pds.ramblock_name = name; pds.cur_entry = 0; pds.nsentwords = 0; pds.nsentcmds = 0; } /** * postcopy_discard_send_range: Called by the bitmap code for each chunk to * discard. May send a discard message, may just leave it queued to * be sent later. * * @ms: Current migration state. * @start,@length: a range of pages in the migration bitmap in the * RAM block passed to postcopy_discard_send_init() (length=1 is one page) */ void postcopy_discard_send_range(MigrationState *ms, unsigned long start, unsigned long length) { size_t tp_size = qemu_target_page_size(); /* Convert to byte offsets within the RAM block */ pds.start_list[pds.cur_entry] = start * tp_size; pds.length_list[pds.cur_entry] = length * tp_size; trace_postcopy_discard_send_range(pds.ramblock_name, start, length); pds.cur_entry++; pds.nsentwords++; if (pds.cur_entry == MAX_DISCARDS_PER_COMMAND) { /* Full set, ship it! */ qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file, pds.ramblock_name, pds.cur_entry, pds.start_list, pds.length_list); pds.nsentcmds++; pds.cur_entry = 0; } } /** * postcopy_discard_send_finish: Called at the end of each RAMBlock by the * bitmap code. Sends any outstanding discard messages, frees the PDS * * @ms: Current migration state. */ void postcopy_discard_send_finish(MigrationState *ms) { /* Anything unsent? */ if (pds.cur_entry) { qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file, pds.ramblock_name, pds.cur_entry, pds.start_list, pds.length_list); pds.nsentcmds++; } trace_postcopy_discard_send_finish(pds.ramblock_name, pds.nsentwords, pds.nsentcmds); } /* * Current state of incoming postcopy; note this is not part of * MigrationIncomingState since it's state is used during cleanup * at the end as MIS is being freed. */ static PostcopyState incoming_postcopy_state; PostcopyState postcopy_state_get(void) { return qatomic_load_acquire(&incoming_postcopy_state); } /* Set the state and return the old state */ PostcopyState postcopy_state_set(PostcopyState new_state) { return qatomic_xchg(&incoming_postcopy_state, new_state); } /* Register a handler for external shared memory postcopy * called on the destination. */ void postcopy_register_shared_ufd(struct PostCopyFD *pcfd) { MigrationIncomingState *mis = migration_incoming_get_current(); mis->postcopy_remote_fds = g_array_append_val(mis->postcopy_remote_fds, *pcfd); } /* Unregister a handler for external shared memory postcopy */ void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd) { guint i; MigrationIncomingState *mis = migration_incoming_get_current(); GArray *pcrfds = mis->postcopy_remote_fds; if (!pcrfds) { /* migration has already finished and freed the array */ return; } for (i = 0; i < pcrfds->len; i++) { struct PostCopyFD *cur = &g_array_index(pcrfds, struct PostCopyFD, i); if (cur->fd == pcfd->fd) { mis->postcopy_remote_fds = g_array_remove_index(pcrfds, i); return; } } } void postcopy_preempt_new_channel(MigrationIncomingState *mis, QEMUFile *file) { /* * The new loading channel has its own threads, so it needs to be * blocked too. It's by default true, just be explicit. */ qemu_file_set_blocking(file, true); mis->postcopy_qemufile_dst = file; qemu_sem_post(&mis->postcopy_qemufile_dst_done); trace_postcopy_preempt_new_channel(); } /* * Setup the postcopy preempt channel with the IOC. If ERROR is specified, * setup the error instead. This helper will free the ERROR if specified. */ static void postcopy_preempt_send_channel_done(MigrationState *s, QIOChannel *ioc, Error *local_err) { if (local_err) { migrate_set_error(s, local_err); error_free(local_err); } else { migration_ioc_register_yank(ioc); s->postcopy_qemufile_src = qemu_file_new_output(ioc); trace_postcopy_preempt_new_channel(); } /* * Kick the waiter in all cases. The waiter should check upon * postcopy_qemufile_src to know whether it failed or not. */ qemu_sem_post(&s->postcopy_qemufile_src_sem); } static void postcopy_preempt_tls_handshake(QIOTask *task, gpointer opaque) { g_autoptr(QIOChannel) ioc = QIO_CHANNEL(qio_task_get_source(task)); MigrationState *s = opaque; Error *local_err = NULL; qio_task_propagate_error(task, &local_err); postcopy_preempt_send_channel_done(s, ioc, local_err); } static void postcopy_preempt_send_channel_new(QIOTask *task, gpointer opaque) { g_autoptr(QIOChannel) ioc = QIO_CHANNEL(qio_task_get_source(task)); MigrationState *s = opaque; QIOChannelTLS *tioc; Error *local_err = NULL; if (qio_task_propagate_error(task, &local_err)) { goto out; } if (migrate_channel_requires_tls_upgrade(ioc)) { tioc = migration_tls_client_create(ioc, s->hostname, &local_err); if (!tioc) { goto out; } trace_postcopy_preempt_tls_handshake(); qio_channel_set_name(QIO_CHANNEL(tioc), "migration-tls-preempt"); qio_channel_tls_handshake(tioc, postcopy_preempt_tls_handshake, s, NULL, NULL); /* Setup the channel until TLS handshake finished */ return; } out: /* This handles both good and error cases */ postcopy_preempt_send_channel_done(s, ioc, local_err); } /* * This function will kick off an async task to establish the preempt * channel, and wait until the connection setup completed. Returns 0 if * channel established, -1 for error. */ int postcopy_preempt_establish_channel(MigrationState *s) { /* If preempt not enabled, no need to wait */ if (!migrate_postcopy_preempt()) { return 0; } /* * Kick off async task to establish preempt channel. Only do so with * 8.0+ machines, because 7.1/7.2 require the channel to be created in * setup phase of migration (even if racy in an unreliable network). */ if (!s->preempt_pre_7_2) { postcopy_preempt_setup(s); } /* * We need the postcopy preempt channel to be established before * starting doing anything. */ qemu_sem_wait(&s->postcopy_qemufile_src_sem); return s->postcopy_qemufile_src ? 0 : -1; } void postcopy_preempt_setup(MigrationState *s) { /* Kick an async task to connect */ socket_send_channel_create(postcopy_preempt_send_channel_new, s); } static void postcopy_pause_ram_fast_load(MigrationIncomingState *mis) { trace_postcopy_pause_fast_load(); qemu_mutex_unlock(&mis->postcopy_prio_thread_mutex); qemu_sem_wait(&mis->postcopy_pause_sem_fast_load); qemu_mutex_lock(&mis->postcopy_prio_thread_mutex); trace_postcopy_pause_fast_load_continued(); } static bool preempt_thread_should_run(MigrationIncomingState *mis) { return mis->preempt_thread_status != PREEMPT_THREAD_QUIT; } void *postcopy_preempt_thread(void *opaque) { MigrationIncomingState *mis = opaque; int ret; trace_postcopy_preempt_thread_entry(); rcu_register_thread(); qemu_event_set(&mis->thread_sync_event); /* * The preempt channel is established in asynchronous way. Wait * for its completion. */ qemu_sem_wait(&mis->postcopy_qemufile_dst_done); /* Sending RAM_SAVE_FLAG_EOS to terminate this thread */ qemu_mutex_lock(&mis->postcopy_prio_thread_mutex); while (preempt_thread_should_run(mis)) { ret = ram_load_postcopy(mis->postcopy_qemufile_dst, RAM_CHANNEL_POSTCOPY); /* If error happened, go into recovery routine */ if (ret && preempt_thread_should_run(mis)) { postcopy_pause_ram_fast_load(mis); } else { /* We're done */ break; } } qemu_mutex_unlock(&mis->postcopy_prio_thread_mutex); rcu_unregister_thread(); trace_postcopy_preempt_thread_exit(); return NULL; } bool postcopy_is_paused(MigrationStatus status) { return status == MIGRATION_STATUS_POSTCOPY_PAUSED || status == MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP; }