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qemu/qemu/049855b94de5559bc319293c998933d3b25bea8c/./migration/migration.c
blob: fab7949fe118f1019611c8db601ad826c1eb6921 [file]
/*
* QEMU live migration
*
* Copyright IBM, Corp. 2008
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
* Contributions after 2012-01-13 are licensed under the terms of the
* GNU GPL, version 2 or (at your option) any later version.
*/
#include "qemu/osdep.h"
#include "qemu/ctype.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"
#include "migration/blocker.h"
#include "exec.h"
#include "file.h"
#include "system/runstate.h"
#include "system/system.h"
#include "system/cpu-throttle.h"
#include "ram.h"
#include "migration/cpr.h"
#include "migration/global_state.h"
#include "migration/misc.h"
#include "migration.h"
#include "migration-stats.h"
#include "savevm.h"
#include "qemu-file.h"
#include "channel.h"
#include "migration/vmstate.h"
#include "block/block.h"
#include "qapi/error.h"
#include "qapi/clone-visitor.h"
#include "qapi/qapi-visit-migration.h"
#include "qapi/qapi-visit-sockets.h"
#include "qapi/qapi-commands-migration.h"
#include "qapi/qapi-events-migration.h"
#include "qapi/qmp/qerror.h"
#include "qobject/qnull.h"
#include "qemu/rcu.h"
#include "postcopy-ram.h"
#include "qemu/thread.h"
#include "trace.h"
#include "exec/target_page.h"
#include "io/channel-buffer.h"
#include "io/channel-tls.h"
#include "migration/colo.h"
#include "hw/core/boards.h"
#include "monitor/monitor.h"
#include "net/announce.h"
#include "qemu/queue.h"
#include "multifd.h"
#include "qemu/yank.h"
#include "system/cpus.h"
#include "yank_functions.h"
#include "system/qtest.h"
#include "options.h"
#include "system/dirtylimit.h"
#include "qemu/sockets.h"
#include "system/kvm.h"
#include "math.h"
#define NOTIFIER_ELEM_INIT(array, elem) \
[elem] = NOTIFIER_WITH_RETURN_LIST_INITIALIZER((array)[elem])
#define INMIGRATE_DEFAULT_EXIT_ON_ERROR true
static GSList *migration_state_notifiers[MIG_MODE__MAX];
/* Messages sent on the return path from destination to source */
enum mig_rp_message_type {
MIG_RP_MSG_INVALID = 0, /* Must be 0 */
MIG_RP_MSG_SHUT, /* sibling will not send any more RP messages */
MIG_RP_MSG_PONG, /* Response to a PING; data (seq: be32 ) */
MIG_RP_MSG_REQ_PAGES_ID, /* data (start: be64, len: be32, id: string) */
MIG_RP_MSG_REQ_PAGES, /* data (start: be64, len: be32) */
MIG_RP_MSG_RECV_BITMAP, /* send recved_bitmap back to source */
MIG_RP_MSG_RESUME_ACK, /* tell source that we are ready to resume */
MIG_RP_MSG_SWITCHOVER_ACK, /* Tell source it's OK to do switchover */
MIG_RP_MSG_MAX
};
/* When we add fault tolerance, we could have several
migrations at once. For now we don't need to add
dynamic creation of migration */
static MigrationState *current_migration;
static MigrationIncomingState *current_incoming;
static GSList *migration_blockers[MIG_MODE__MAX];
static bool migration_object_check(MigrationState *ms, Error **errp);
static bool migration_switchover_start(MigrationState *s, Error **errp);
static bool stop_return_path_thread_on_source(MigrationState *s);
static void migration_release_dst_files(MigrationState *ms);
static void migration_completion_end(MigrationState *s);
static void migration_downtime_start(MigrationState *s)
{
trace_vmstate_downtime_checkpoint("src-downtime-start");
s->downtime_start = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
}
/*
* This is unfortunate: incoming migration actually needs the outgoing
* migration state (MigrationState) to be there too, e.g. to query
* capabilities, parameters, using locks, setup errors, etc.
*
* NOTE: when calling this, making sure current_migration exists and not
* been freed yet! Otherwise trying to access the refcount is already
* an use-after-free itself..
*
* TODO: Move shared part of incoming / outgoing out into separate object.
* Then this is not needed.
*/
static void migrate_incoming_ref_outgoing_state(void)
{
object_ref(migrate_get_current());
}
static void migrate_incoming_unref_outgoing_state(void)
{
object_unref(migrate_get_current());
}
static void migration_downtime_end(MigrationState *s)
{
int64_t now = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
/*
* If downtime already set, should mean that postcopy already set it,
* then that should be the real downtime already.
*/
if (!s->downtime) {
s->downtime = now - s->downtime_start;
trace_vmstate_downtime_checkpoint("src-downtime-end");
}
}
static void precopy_notify_complete(void)
{
Error *local_err = NULL;
if (precopy_notify(PRECOPY_NOTIFY_COMPLETE, &local_err)) {
error_report_err(local_err);
}
trace_migration_precopy_complete();
}
static bool migration_needs_multiple_sockets(void)
{
return migrate_multifd() || migrate_postcopy_preempt();
}
static RunState migration_get_target_runstate(void)
{
/*
* When the global state is not migrated, it means we don't know the
* runstate of the src QEMU. We don't have much choice but assuming
* the VM is running. NOTE: this is pretty rare case, so far only Xen
* uses it.
*/
if (!global_state_received()) {
return RUN_STATE_RUNNING;
}
return global_state_get_runstate();
}
static bool transport_supports_multi_channels(MigrationAddress *addr)
{
if (addr->transport == MIGRATION_ADDRESS_TYPE_SOCKET) {
SocketAddress *saddr = &addr->u.socket;
return (saddr->type == SOCKET_ADDRESS_TYPE_INET ||
saddr->type == SOCKET_ADDRESS_TYPE_UNIX ||
saddr->type == SOCKET_ADDRESS_TYPE_VSOCK);
} else if (addr->transport == MIGRATION_ADDRESS_TYPE_FILE) {
return migrate_mapped_ram();
} else {
return false;
}
}
static bool migration_needs_seekable_channel(void)
{
return migrate_mapped_ram();
}
static bool migration_needs_extra_fds(void)
{
/*
* When doing direct-io, multifd requires two different,
* non-duplicated file descriptors so we can use one of them for
* unaligned IO.
*/
return migrate_multifd() && migrate_direct_io();
}
static bool transport_supports_seeking(MigrationAddress *addr)
{
if (addr->transport == MIGRATION_ADDRESS_TYPE_FILE) {
return true;
}
return false;
}
static bool transport_supports_extra_fds(MigrationAddress *addr)
{
/* file: works because QEMU can open it multiple times */
return addr->transport == MIGRATION_ADDRESS_TYPE_FILE;
}
static bool
migration_channels_and_transport_compatible(MigrationAddress *addr,
Error **errp)
{
if (migration_needs_seekable_channel() &&
!transport_supports_seeking(addr)) {
error_setg(errp, "Migration requires seekable transport (e.g. file)");
return false;
}
if (migration_needs_multiple_sockets() &&
!transport_supports_multi_channels(addr)) {
error_setg(errp, "Migration requires multi-channel URIs (e.g. tcp)");
return false;
}
if (migration_needs_extra_fds() &&
!transport_supports_extra_fds(addr)) {
error_setg(errp,
"Migration requires a transport that allows for extra fds (e.g. file)");
return false;
}
if (migrate_mode() == MIG_MODE_CPR_TRANSFER &&
addr->transport == MIGRATION_ADDRESS_TYPE_FILE) {
error_setg(errp, "Migration requires streamable transport (eg unix)");
return false;
}
return true;
}
static bool
migration_capabilities_and_transport_compatible(MigrationAddress *addr,
Error **errp)
{
if (addr->transport == MIGRATION_ADDRESS_TYPE_RDMA) {
return migrate_rdma_caps_check(migrate_get_current()->capabilities,
errp);
}
if (migrate_local() && migrate_mode() != MIG_MODE_CPR_EXEC &&
(addr->transport != MIGRATION_ADDRESS_TYPE_SOCKET ||
(addr->u.socket.type != SOCKET_ADDRESS_TYPE_UNIX &&
addr->u.socket.type != SOCKET_ADDRESS_TYPE_FD))) {
/*
* For SOCKET_ADDRESS_TYPE_FD we do check the fd itself later
* in migration_fd_valid().
*/
error_setg(errp,
"local migration requires a UNIX domain socket channel");
return false;
}
return true;
}
static bool migration_transport_compatible(MigrationAddress *addr, Error **errp)
{
return migration_channels_and_transport_compatible(addr, errp) &&
migration_capabilities_and_transport_compatible(addr, errp);
}
static gint page_request_addr_cmp(gconstpointer ap, gconstpointer bp)
{
uintptr_t a = (uintptr_t) ap, b = (uintptr_t) bp;
return (a > b) - (a < b);
}
static int migration_stop_vm(MigrationState *s, RunState state)
{
int ret;
migration_downtime_start(s);
s->vm_old_state = runstate_get();
global_state_store();
ret = vm_stop_force_state(state);
trace_vmstate_downtime_checkpoint("src-vm-stopped");
trace_migration_completion_vm_stop(ret);
return ret;
}
void migration_object_init(void)
{
/* This can only be called once. */
assert(!current_migration);
current_migration = MIGRATION(object_new(TYPE_MIGRATION));
/*
* Init the migrate incoming object as well no matter whether
* we'll use it or not.
*/
assert(!current_incoming);
current_incoming = g_new0(MigrationIncomingState, 1);
current_incoming->state = MIGRATION_STATUS_NONE;
current_incoming->postcopy_remote_fds =
g_array_new(FALSE, TRUE, sizeof(struct PostCopyFD));
qemu_mutex_init(&current_incoming->rp_mutex);
qemu_mutex_init(&current_incoming->postcopy_prio_thread_mutex);
qemu_event_init(&current_incoming->main_thread_load_event, false);
qemu_sem_init(&current_incoming->postcopy_pause_sem_dst, 0);
qemu_sem_init(&current_incoming->postcopy_pause_sem_fault, 0);
qemu_sem_init(&current_incoming->postcopy_pause_sem_fast_load, 0);
qemu_sem_init(&current_incoming->postcopy_qemufile_dst_done, 0);
qemu_mutex_init(&current_incoming->page_request_mutex);
qemu_cond_init(&current_incoming->page_request_cond);
current_incoming->page_requested = g_tree_new(page_request_addr_cmp);
current_incoming->exit_on_error = INMIGRATE_DEFAULT_EXIT_ON_ERROR;
migration_object_check(current_migration, &error_fatal);
ram_mig_init();
dirty_bitmap_mig_init();
cpr_exec_init();
/* Initialize cpu throttle timers */
cpu_throttle_init();
}
typedef struct {
QEMUBH *bh;
QEMUBHFunc *cb;
void *opaque;
} MigrationBH;
static void migration_bh_dispatch_bh(void *opaque)
{
MigrationState *s = migrate_get_current();
MigrationBH *migbh = opaque;
/* cleanup this BH */
qemu_bh_delete(migbh->bh);
migbh->bh = NULL;
/* dispatch the other one */
migbh->cb(migbh->opaque);
object_unref(OBJECT(s));
g_free(migbh);
}
void migration_bh_schedule(QEMUBHFunc *cb, void *opaque)
{
MigrationState *s = migrate_get_current();
MigrationBH *migbh = g_new0(MigrationBH, 1);
QEMUBH *bh = qemu_bh_new(migration_bh_dispatch_bh, migbh);
/* Store these to dispatch when the BH runs */
migbh->bh = bh;
migbh->cb = cb;
migbh->opaque = opaque;
/*
* Ref the state for bh, because it may be called when
* there're already no other refs
*/
object_ref(OBJECT(s));
qemu_bh_schedule(bh);
}
void migration_shutdown(void)
{
/*
* When the QEMU main thread exit, the COLO thread
* may wait a semaphore. So, we should wakeup the
* COLO thread before migration shutdown.
*/
colo_shutdown();
/*
* Cancel the current migration - that will (eventually)
* stop the migration using this structure
*/
migration_cancel();
object_unref(OBJECT(current_migration));
/*
* Cancel outgoing migration of dirty bitmaps. It should
* at least unref used block nodes.
*/
dirty_bitmap_mig_cancel_outgoing();
/*
* Cancel incoming migration of dirty bitmaps. Dirty bitmaps
* are non-critical data, and their loss never considered as
* something serious.
*/
dirty_bitmap_mig_cancel_incoming();
}
/* For outgoing */
MigrationState *migrate_get_current(void)
{
/* This can only be called after the object created. */
assert(current_migration);
return current_migration;
}
MigrationIncomingState *migration_incoming_get_current(void)
{
assert(current_incoming);
return current_incoming;
}
void migration_incoming_transport_cleanup(MigrationIncomingState *mis)
{
if (mis->socket_address_list) {
qapi_free_SocketAddressList(mis->socket_address_list);
mis->socket_address_list = NULL;
}
if (mis->transport_cleanup) {
mis->transport_cleanup(mis->transport_data);
mis->transport_data = mis->transport_cleanup = NULL;
}
}
void migration_incoming_state_destroy(void)
{
MigrationIncomingState *mis = migration_incoming_get_current();
PostcopyState ps = postcopy_state_get();
multifd_recv_cleanup();
if (ps != POSTCOPY_INCOMING_NONE) {
postcopy_incoming_cleanup(mis);
}
/*
* RAM state cleanup needs to happen after multifd cleanup, because
* multifd threads can use some of its states (receivedmap).
* The VFIO load_cleanup() implementation is BQL-sensitive. It requires
* BQL must NOT be taken when recycling load threads, so that it won't
* block the load threads from making progress on address space
* modification operations.
*
* To make it work, we could try to not take BQL for all load_cleanup(),
* or conditionally unlock BQL only if bql_locked() in VFIO.
*
* Since most existing call sites take BQL for load_cleanup(), make
* it simple by taking BQL always as the rule, so that VFIO can unlock
* BQL and retake unconditionally.
*/
assert(bql_locked());
if (migrate_colo()) {
colo_release_ram_cache();
}
qemu_loadvm_state_cleanup(mis);
if (mis->to_src_file) {
/* Tell source that we are done */
migrate_send_rp_shut(mis, qemu_file_get_error(mis->from_src_file) != 0);
qemu_fclose(mis->to_src_file);
mis->to_src_file = NULL;
}
if (mis->from_src_file) {
migration_ioc_unregister_yank_from_file(mis->from_src_file);
qemu_fclose(mis->from_src_file);
mis->from_src_file = NULL;
}
if (mis->postcopy_remote_fds) {
g_array_free(mis->postcopy_remote_fds, TRUE);
mis->postcopy_remote_fds = NULL;
}
migration_incoming_transport_cleanup(mis);
qemu_event_reset(&mis->main_thread_load_event);
if (mis->page_requested) {
g_tree_destroy(mis->page_requested);
mis->page_requested = NULL;
}
if (mis->postcopy_qemufile_dst) {
migration_ioc_unregister_yank_from_file(mis->postcopy_qemufile_dst);
qemu_fclose(mis->postcopy_qemufile_dst);
mis->postcopy_qemufile_dst = NULL;
}
cpr_set_incoming_mode(MIG_MODE_NONE);
yank_unregister_instance(MIGRATION_YANK_INSTANCE);
}
static void migrate_generate_event(MigrationStatus new_state)
{
if (migrate_events()) {
qapi_event_send_migration(new_state);
}
}
/*
* Send a message on the return channel back to the source
* of the migration.
*/
static int migrate_send_rp_message(MigrationIncomingState *mis,
enum mig_rp_message_type message_type,
uint16_t len, void *data)
{
int ret = 0;
trace_migrate_send_rp_message((int)message_type, len);
QEMU_LOCK_GUARD(&mis->rp_mutex);
/*
* It's possible that the file handle got lost due to network
* failures.
*/
if (!mis->to_src_file) {
ret = -EIO;
return ret;
}
qemu_put_be16(mis->to_src_file, (unsigned int)message_type);
qemu_put_be16(mis->to_src_file, len);
qemu_put_buffer(mis->to_src_file, data, len);
return qemu_fflush(mis->to_src_file);
}
/* Request one page from the source VM at the given start address.
* rb: the RAMBlock to request the page in
* Start: Address offset within the RB
* Len: Length in bytes required - must be a multiple of pagesize
*/
int migrate_send_rp_message_req_pages(MigrationIncomingState *mis,
RAMBlock *rb, ram_addr_t start)
{
uint8_t bufc[12 + 1 + 255]; /* start (8), len (4), rbname up to 256 */
size_t msglen = 12; /* start + len */
size_t len = qemu_ram_pagesize(rb);
enum mig_rp_message_type msg_type;
const char *rbname;
int rbname_len;
*(uint64_t *)bufc = cpu_to_be64((uint64_t)start);
*(uint32_t *)(bufc + 8) = cpu_to_be32((uint32_t)len);
/*
* We maintain the last ramblock that we requested for page. Note that we
* don't need locking because this function will only be called within the
* postcopy ram fault thread.
*/
if (rb != mis->last_rb) {
mis->last_rb = rb;
rbname = qemu_ram_get_idstr(rb);
rbname_len = strlen(rbname);
assert(rbname_len < 256);
bufc[msglen++] = rbname_len;
memcpy(bufc + msglen, rbname, rbname_len);
msglen += rbname_len;
msg_type = MIG_RP_MSG_REQ_PAGES_ID;
} else {
msg_type = MIG_RP_MSG_REQ_PAGES;
}
return migrate_send_rp_message(mis, msg_type, msglen, bufc);
}
int migrate_send_rp_req_pages(MigrationIncomingState *mis,
RAMBlock *rb, ram_addr_t start, uint64_t haddr,
uint32_t tid)
{
/*
* If not able to mark page for blocktime it must already be present.
* If the page is there, skip sending the message. We don't even need the
* lock because as long as the page arrived, it'll be there forever.
*/
if (!try_mark_postcopy_blocktime_begin(mis, rb, start, haddr, tid)) {
return 0;
}
return migrate_send_rp_message_req_pages(mis, rb, start);
}
void migrate_add_address(SocketAddress *address)
{
MigrationIncomingState *mis = migration_incoming_get_current();
QAPI_LIST_PREPEND(mis->socket_address_list,
QAPI_CLONE(SocketAddress, address));
}
bool migrate_is_uri(const char *uri)
{
while (*uri && *uri != ':') {
if (!qemu_isalpha(*uri++)) {
return false;
}
}
return *uri == ':';
}
static bool
migration_incoming_state_setup(MigrationIncomingState *mis, Error **errp)
{
MigrationStatus current = mis->state;
if (current == MIGRATION_STATUS_POSTCOPY_PAUSED) {
/*
* Incoming postcopy migration will stay in PAUSED state even if
* reconnection happened.
*/
return true;
}
if (current != MIGRATION_STATUS_NONE) {
error_setg(errp, "Illegal migration incoming state: %s",
MigrationStatus_str(current));
return false;
}
migrate_set_state(&mis->state, current, MIGRATION_STATUS_SETUP);
return true;
}
static void qemu_setup_incoming_migration(const char *uri, bool has_channels,
MigrationChannelList *channels,
Error **errp)
{
g_autoptr(MigrationChannel) main_ch = NULL;
MigrationIncomingState *mis = migration_incoming_get_current();
if (!migration_channel_parse_input(uri, channels, &main_ch, NULL, errp)) {
return;
}
/* transport mechanism not suitable for migration? */
if (!migration_transport_compatible(main_ch->addr, errp)) {
return;
}
if (!migration_incoming_state_setup(mis, errp)) {
return;
}
migration_connect_incoming(main_ch->addr, errp);
/* Close cpr socket to tell source that we are listening */
cpr_state_close();
}
static void process_incoming_migration_bh(void *opaque)
{
MigrationIncomingState *mis = opaque;
trace_vmstate_downtime_checkpoint("dst-precopy-bh-enter");
/*
* This must happen after all error conditions are dealt with and
* we're sure the VM is going to be running on this host.
*/
qemu_announce_self(&mis->announce_timer, migrate_announce_params());
trace_vmstate_downtime_checkpoint("dst-precopy-bh-announced");
multifd_recv_shutdown();
dirty_bitmap_mig_before_vm_start();
if (runstate_is_live(migration_get_target_runstate())) {
if (autostart) {
/*
* Block activation is always delayed until VM starts, either
* here (which means we need to start the dest VM right now..),
* or until qmp_cont() later.
*
* We used to have cap 'late-block-activate' but now we do this
* unconditionally, as it has no harm but only benefit. E.g.,
* it's not part of migration ABI on the time of disk activation.
*
* Make sure all file formats throw away their mutable
* metadata. If error, don't restart the VM yet.
*/
if (migration_block_activate(NULL)) {
vm_start();
}
} else {
runstate_set(RUN_STATE_PAUSED);
}
} else if (migrate_colo()) {
vm_start();
} else {
runstate_set(global_state_get_runstate());
}
trace_vmstate_downtime_checkpoint("dst-precopy-bh-vm-started");
/*
* This must happen after any state changes since as soon as an external
* observer sees this event they might start to prod at the VM assuming
* it's ready to use.
*/
migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
MIGRATION_STATUS_COMPLETED);
migration_incoming_state_destroy();
}
static bool migration_incoming_has_postcopy_thread(MigrationIncomingState *mis)
{
return mis->have_listen_thread || mis->have_eager_load_thread;
}
static void coroutine_fn
process_incoming_migration_co(void *opaque)
{
MigrationState *s = migrate_get_current();
MigrationIncomingState *mis = migration_incoming_get_current();
int ret;
Error *local_err = NULL;
assert(mis->from_src_file);
if (migrate_colo()) {
if (ram_block_discard_disable(true)) {
error_setg(&local_err, "COLO: cannot disable RAM discard");
goto fail;
}
ret = colo_init_ram_cache(&local_err);
if (ret) {
error_prepend(&local_err, "failed to init colo RAM cache: %d: ",
ret);
goto fail;
}
}
mis->largest_page_size = qemu_ram_pagesize_largest();
postcopy_state_set(POSTCOPY_INCOMING_NONE);
migrate_set_state(&mis->state, MIGRATION_STATUS_SETUP,
MIGRATION_STATUS_ACTIVE);
/*
* When loading snapshot with postcopy enabled, setup the postcopy
* infrastructure before loading the major part of device states.
* It's required because qemu_loadvm_state() may access guest memory
* while loading device states, which can cause page faults already.
*/
if (migrate_postcopy_ram() && migrate_mapped_ram()) {
migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
MIGRATION_STATUS_POSTCOPY_DEVICE);
if (ram_postcopy_incoming_init(mis, &local_err)) {
goto fail;
}
postcopy_state_set(POSTCOPY_INCOMING_LISTENING);
if (postcopy_ram_incoming_setup(mis, &local_err)) {
goto fail;
}
}
mis->loadvm_co = qemu_coroutine_self();
ret = qemu_loadvm_state(mis->from_src_file, &local_err);
mis->loadvm_co = NULL;
if (ret < 0) {
goto fail;
}
if (migrate_postcopy_ram() && migrate_mapped_ram()) {
qemu_loadvm_run_fast_snapshot_load(mis->from_src_file, mis);
}
trace_vmstate_downtime_checkpoint("dst-precopy-loadvm-completed");
trace_process_incoming_migration_co_end(ret);
if (migration_incoming_has_postcopy_thread(mis)) {
/*
* Postcopy was started, cleanup should happen at the end of the
* postcopy listen thread or eager load thread.
*/
trace_process_incoming_migration_co_postcopy_end_main();
goto out;
}
if (ret < 0) {
error_prepend(&local_err, "load of migration failed: %s: ",
strerror(-ret));
goto fail;
}
if (migrate_colo()) {
/* yield until COLO exit */
colo_incoming_co();
}
migration_bh_schedule(process_incoming_migration_bh, mis);
goto out;
fail:
migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
MIGRATION_STATUS_FAILED);
migrate_error_propagate(s, local_err);
migration_incoming_state_destroy();
if (mis->exit_on_error) {
WITH_QEMU_LOCK_GUARD(&s->error_mutex) {
error_report_err(s->error);
s->error = NULL;
}
exit(EXIT_FAILURE);
}
out:
/* Pairs with the refcount taken in qmp_migrate_incoming() */
migrate_incoming_unref_outgoing_state();
}
/*
* Returns whether all the necessary channels to proceed with the
* incoming migration have been established without error.
*/
bool migration_incoming_setup(QIOChannel *ioc, uint8_t channel, Error **errp)
{
MigrationIncomingState *mis = migration_incoming_get_current();
QEMUFile *f;
if (multifd_recv_setup(errp) != 0) {
return false;
}
switch (channel) {
case CH_MAIN:
f = qemu_file_new_input(ioc);
assert(!mis->from_src_file);
mis->from_src_file = f;
qemu_file_set_blocking(f, false, &error_abort);
break;
case CH_MULTIFD:
if (!multifd_recv_new_channel(ioc, errp)) {
return false;
}
break;
case CH_POSTCOPY:
assert(!mis->postcopy_qemufile_dst);
f = qemu_file_new_input(ioc);
postcopy_preempt_new_channel(mis, f);
return false;
default:
g_assert_not_reached();
}
return migration_has_main_and_multifd_channels();
}
void migration_outgoing_setup(QIOChannel *ioc)
{
MigrationState *s = migrate_get_current();
QEMUFile *f = qemu_file_new_output(ioc);
qemu_mutex_lock(&s->qemu_file_lock);
s->to_dst_file = f;
qemu_mutex_unlock(&s->qemu_file_lock);
}
/* Returns true if recovered from a paused migration, otherwise false */
static bool postcopy_try_recover(void)
{
MigrationIncomingState *mis = migration_incoming_get_current();
if (mis->state == MIGRATION_STATUS_POSTCOPY_PAUSED) {
/* Resumed from a paused postcopy migration */
/* This should be set already in migration_incoming_setup() */
assert(mis->from_src_file);
/* Postcopy has standalone thread to do vm load */
qemu_file_set_blocking(mis->from_src_file, true, &error_abort);
/* Re-configure the return path */
mis->to_src_file = qemu_file_get_return_path(mis->from_src_file);
migrate_set_state(&mis->state, MIGRATION_STATUS_POSTCOPY_PAUSED,
MIGRATION_STATUS_POSTCOPY_RECOVER);
/*
* Here, we only wake up the main loading thread (while the
* rest threads will still be waiting), so that we can receive
* commands from source now, and answer it if needed. The
* rest threads will be woken up afterwards until we are sure
* that source is ready to reply to page requests.
*/
qemu_sem_post(&mis->postcopy_pause_sem_dst);
return true;
}
return false;
}
void migration_start_incoming(void)
{
if (postcopy_try_recover()) {
return;
}
Coroutine *co = qemu_coroutine_create(process_incoming_migration_co, NULL);
qemu_coroutine_enter(co);
/*
* This doesn't return right away. The coroutine will run
* unimpeded until its first yield, which may happen as late as
* the force yield at ram_load_precopy().
*/
}
int migrate_send_rp_switchover_ack(MigrationIncomingState *mis)
{
return migrate_send_rp_message(mis, MIG_RP_MSG_SWITCHOVER_ACK, 0, NULL);
}
/*
* Send a 'SHUT' message on the return channel with the given value
* to indicate that we've finished with the RP. Non-0 value indicates
* error.
*/
void migrate_send_rp_shut(MigrationIncomingState *mis,
uint32_t value)
{
uint32_t buf;
buf = cpu_to_be32(value);
migrate_send_rp_message(mis, MIG_RP_MSG_SHUT, sizeof(buf), &buf);
}
/*
* Send a 'PONG' message on the return channel with the given value
* (normally in response to a 'PING')
*/
void migrate_send_rp_pong(MigrationIncomingState *mis,
uint32_t value)
{
uint32_t buf;
buf = cpu_to_be32(value);
migrate_send_rp_message(mis, MIG_RP_MSG_PONG, sizeof(buf), &buf);
}
void migrate_send_rp_recv_bitmap(MigrationIncomingState *mis,
char *block_name)
{
char buf[512];
int len;
int64_t res;
/*
* First, we send the header part. It contains only the len of
* idstr, and the idstr itself.
*/
len = strlen(block_name);
buf[0] = len;
memcpy(buf + 1, block_name, len);
if (mis->state != MIGRATION_STATUS_POSTCOPY_RECOVER) {
error_report("%s: MSG_RP_RECV_BITMAP only used for recovery",
__func__);
return;
}
migrate_send_rp_message(mis, MIG_RP_MSG_RECV_BITMAP, len + 1, buf);
/*
* Next, we dump the received bitmap to the stream.
*
* TODO: currently we are safe since we are the only one that is
* using the to_src_file handle (fault thread is still paused),
* and it's ok even not taking the mutex. However the best way is
* to take the lock before sending the message header, and release
* the lock after sending the bitmap.
*/
qemu_mutex_lock(&mis->rp_mutex);
res = ramblock_recv_bitmap_send(mis->to_src_file, block_name);
qemu_mutex_unlock(&mis->rp_mutex);
trace_migrate_send_rp_recv_bitmap(block_name, res);
}
void migrate_send_rp_resume_ack(MigrationIncomingState *mis, uint32_t value)
{
uint32_t buf;
buf = cpu_to_be32(value);
migrate_send_rp_message(mis, MIG_RP_MSG_RESUME_ACK, sizeof(buf), &buf);
}
/*
* Returns the estimated switchover bandwidth (unit: bytes / seconds)
*/
static double migration_get_switchover_bw(MigrationState *s)
{
uint64_t switchover_bw = migrate_avail_switchover_bandwidth();
if (switchover_bw) {
/* If user specified, prioritize this value and don't estimate */
return (double)switchover_bw;
}
return s->mbps / 8 * 1000 * 1000;
}
bool migration_is_running(void)
{
MigrationState *s = current_migration;
if (!s) {
return false;
}
switch (s->state) {
case MIGRATION_STATUS_ACTIVE:
case MIGRATION_STATUS_POSTCOPY_DEVICE:
case MIGRATION_STATUS_POSTCOPY_ACTIVE:
case MIGRATION_STATUS_POSTCOPY_PAUSED:
case MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP:
case MIGRATION_STATUS_POSTCOPY_RECOVER:
case MIGRATION_STATUS_SETUP:
case MIGRATION_STATUS_PRE_SWITCHOVER:
case MIGRATION_STATUS_DEVICE:
case MIGRATION_STATUS_WAIT_UNPLUG:
case MIGRATION_STATUS_CANCELLING:
case MIGRATION_STATUS_FAILING:
case MIGRATION_STATUS_COLO:
return true;
default:
return false;
}
}
static bool migration_is_active(void)
{
MigrationState *s = migrate_get_current();
return (s->state == MIGRATION_STATUS_ACTIVE ||
s->state == MIGRATION_STATUS_POSTCOPY_DEVICE ||
s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);
}
static bool migrate_show_downtime(MigrationState *s)
{
return (s->state == MIGRATION_STATUS_COMPLETED) || migration_in_postcopy();
}
/* Return expected downtime (unit: milliseconds) */
int64_t migration_downtime_calc_expected(MigrationState *s)
{
double expected_ms;
if (mig_stats.dirty_sync_count <= 1) {
return migrate_downtime_limit();
}
expected_ms = mig_stats.dirty_bytes_last_sync /
migration_get_switchover_bw(s) * 1000;
/*
* If we haven't been able to transfer any data, the result here could
* be NaN (for 0 / 0) or infinity (something else / 0).
*
* Return INT64_MAX as our best approximation to "this will take
* forever to complete". If the problem is transient (e.g. we just
* haven't started to transfer yet) we'll recalculate to a more
* accurate figure later.
*/
if (isnan(expected_ms) || expected_ms >= (double)INT64_MAX) {
return INT64_MAX;
}
return (int64_t) expected_ms;
}
static void populate_time_info(MigrationInfo *info, MigrationState *s)
{
info->has_status = true;
info->has_setup_time = true;
info->setup_time = s->setup_time;
if (s->state == MIGRATION_STATUS_COMPLETED) {
info->has_total_time = true;
info->total_time = s->total_time;
} else {
info->has_total_time = true;
info->total_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) -
s->start_time;
}
if (migrate_show_downtime(s)) {
info->has_downtime = true;
info->downtime = s->downtime;
} else {
info->has_expected_downtime = true;
info->expected_downtime = migration_downtime_calc_expected(s);
}
}
static void populate_global_info(MigrationInfo *info, MigrationState *s)
{
info->has_remaining = true;
info->remaining = qatomic_read(&mig_stats.dirty_bytes_total);
}
static void populate_ram_info(MigrationInfo *info, MigrationState *s)
{
size_t page_size = qemu_target_page_size();
info->ram = g_malloc0(sizeof(*info->ram));
info->ram->transferred = migration_transferred_bytes();
info->ram->total = ram_bytes_total();
info->ram->duplicate = qatomic_read(&mig_stats.zero_pages);
info->ram->normal = qatomic_read(&mig_stats.normal_pages);
info->ram->normal_bytes = info->ram->normal * page_size;
info->ram->mbps = s->mbps;
info->ram->dirty_sync_count =
qatomic_read(&mig_stats.dirty_sync_count);
info->ram->dirty_sync_missed_zero_copy =
qatomic_read(&mig_stats.dirty_sync_missed_zero_copy);
info->ram->postcopy_requests =
qatomic_read(&mig_stats.postcopy_requests);
info->ram->page_size = page_size;
info->ram->multifd_bytes = qatomic_read(&mig_stats.multifd_bytes);
info->ram->pages_per_second = s->pages_per_second;
info->ram->precopy_bytes = qatomic_read(&mig_stats.precopy_bytes);
info->ram->downtime_bytes = qatomic_read(&mig_stats.downtime_bytes);
info->ram->postcopy_bytes = qatomic_read(&mig_stats.postcopy_bytes);
if (migrate_xbzrle()) {
info->xbzrle_cache = g_malloc0(sizeof(*info->xbzrle_cache));
info->xbzrle_cache->cache_size = migrate_xbzrle_cache_size();
info->xbzrle_cache->bytes = xbzrle_counters.bytes;
info->xbzrle_cache->pages = xbzrle_counters.pages;
info->xbzrle_cache->cache_miss = xbzrle_counters.cache_miss;
info->xbzrle_cache->cache_miss_rate = xbzrle_counters.cache_miss_rate;
info->xbzrle_cache->encoding_rate = xbzrle_counters.encoding_rate;
info->xbzrle_cache->overflow = xbzrle_counters.overflow;
}
if (cpu_throttle_active()) {
info->has_cpu_throttle_percentage = true;
info->cpu_throttle_percentage = cpu_throttle_get_percentage();
}
if (s->state != MIGRATION_STATUS_COMPLETED) {
info->ram->remaining = ram_bytes_remaining();
info->ram->dirty_pages_rate =
qatomic_read(&mig_stats.dirty_pages_rate);
}
if (migrate_dirty_limit() && dirtylimit_in_service()) {
info->has_dirty_limit_throttle_time_per_round = true;
info->dirty_limit_throttle_time_per_round =
dirtylimit_throttle_time_per_round();
info->has_dirty_limit_ring_full_time = true;
info->dirty_limit_ring_full_time = dirtylimit_ring_full_time();
}
}
static void fill_source_migration_info(MigrationInfo *info)
{
MigrationState *s = migrate_get_current();
int state = qatomic_read(&s->state);
GSList *cur_blocker = migration_blockers[migrate_mode()];
info->blocked_reasons = NULL;
/*
* There are two types of reasons a migration might be blocked;
* a) devices marked in VMState as non-migratable, and
* b) Explicit migration blockers
* We need to add both of them here.
*/
qemu_savevm_non_migratable_list(&info->blocked_reasons);
while (cur_blocker) {
QAPI_LIST_PREPEND(info->blocked_reasons,
g_strdup(error_get_pretty(cur_blocker->data)));
cur_blocker = g_slist_next(cur_blocker);
}
info->has_blocked_reasons = info->blocked_reasons != NULL;
switch (state) {
case MIGRATION_STATUS_NONE:
/* no migration has happened ever */
/* do not overwrite destination migration status */
return;
case MIGRATION_STATUS_SETUP:
info->has_status = true;
info->has_total_time = false;
break;
case MIGRATION_STATUS_ACTIVE:
case MIGRATION_STATUS_CANCELLING:
case MIGRATION_STATUS_POSTCOPY_DEVICE:
case MIGRATION_STATUS_POSTCOPY_ACTIVE:
case MIGRATION_STATUS_PRE_SWITCHOVER:
case MIGRATION_STATUS_DEVICE:
case MIGRATION_STATUS_POSTCOPY_PAUSED:
case MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP:
case MIGRATION_STATUS_POSTCOPY_RECOVER:
case MIGRATION_STATUS_FAILING:
/* TODO add some postcopy stats */
populate_time_info(info, s);
populate_ram_info(info, s);
populate_global_info(info, s);
migration_populate_vfio_info(info);
break;
case MIGRATION_STATUS_COLO:
info->has_status = true;
/* TODO: display COLO specific information (checkpoint info etc.) */
break;
case MIGRATION_STATUS_COMPLETED:
populate_time_info(info, s);
populate_ram_info(info, s);
migration_populate_vfio_info(info);
break;
case MIGRATION_STATUS_FAILED:
info->has_status = true;
break;
case MIGRATION_STATUS_CANCELLED:
info->has_status = true;
break;
case MIGRATION_STATUS_WAIT_UNPLUG:
info->has_status = true;
break;
}
info->status = state;
QEMU_LOCK_GUARD(&s->error_mutex);
if (s->error) {
info->error_desc = g_strdup(error_get_pretty(s->error));
}
}
static void fill_destination_migration_info(MigrationInfo *info)
{
MigrationIncomingState *mis = migration_incoming_get_current();
if (mis->socket_address_list) {
info->has_socket_address = true;
info->socket_address =
QAPI_CLONE(SocketAddressList, mis->socket_address_list);
}
switch (mis->state) {
case MIGRATION_STATUS_SETUP:
case MIGRATION_STATUS_CANCELLING:
case MIGRATION_STATUS_CANCELLED:
case MIGRATION_STATUS_ACTIVE:
case MIGRATION_STATUS_POSTCOPY_DEVICE:
case MIGRATION_STATUS_POSTCOPY_ACTIVE:
case MIGRATION_STATUS_POSTCOPY_PAUSED:
case MIGRATION_STATUS_POSTCOPY_RECOVER:
case MIGRATION_STATUS_FAILED:
case MIGRATION_STATUS_FAILING:
case MIGRATION_STATUS_COLO:
info->has_status = true;
break;
case MIGRATION_STATUS_COMPLETED:
info->has_status = true;
fill_destination_postcopy_migration_info(info);
break;
default:
return;
}
info->status = mis->state;
if (!info->error_desc) {
MigrationState *s = migrate_get_current();
QEMU_LOCK_GUARD(&s->error_mutex);
if (s->error) {
info->error_desc = g_strdup(error_get_pretty(s->error));
}
}
}
MigrationInfo *qmp_query_migrate(Error **errp)
{
MigrationInfo *info = g_malloc0(sizeof(*info));
fill_destination_migration_info(info);
fill_source_migration_info(info);
return info;
}
void qmp_migrate_start_postcopy(Error **errp)
{
MigrationState *s = migrate_get_current();
if (!migrate_postcopy()) {
error_setg(errp, "Enable postcopy with migrate_set_capability before"
" the start of migration");
return;
}
if (s->state == MIGRATION_STATUS_NONE) {
error_setg(errp, "Postcopy must be started after migration has been"
" started");
return;
}
/*
* we don't error if migration has finished since that would be racy
* with issuing this command.
*/
qatomic_set(&s->start_postcopy, true);
}
/* shared migration helpers */
void migrate_set_state(MigrationStatus *state, MigrationStatus old_state,
MigrationStatus new_state)
{
assert(new_state < MIGRATION_STATUS__MAX);
if (qatomic_cmpxchg(state, old_state, new_state) == old_state) {
trace_migrate_set_state(MigrationStatus_str(new_state));
migrate_generate_event(new_state);
}
}
void migration_cleanup_json_writer(MigrationState *s)
{
g_clear_pointer(&s->vmdesc, json_writer_free);
}
static void migration_cleanup(MigrationState *s)
{
QEMUFile *tmp = NULL;
trace_migration_cleanup();
migration_cleanup_json_writer(s);
g_free(s->hostname);
s->hostname = NULL;
qemu_savevm_state_cleanup();
cpr_state_close();
cpr_transfer_source_destroy(s);
stop_return_path_thread_on_source(s);
migration_release_dst_files(s);
if (s->migration_thread_running) {
bql_unlock();
qemu_thread_join(&s->thread);
s->migration_thread_running = false;
bql_lock();
}
WITH_QEMU_LOCK_GUARD(&s->qemu_file_lock) {
/*
* Close the file handle without the lock to make sure the critical
* section won't block for long.
*/
tmp = s->to_dst_file;
s->to_dst_file = NULL;
}
if (tmp) {
/*
* We only need to shutdown multifd if tmp!=NULL, because if
* tmp==NULL, it means the main channel isn't established, while
* multifd is only setup after that (in migration_thread()).
*/
multifd_send_shutdown();
migration_ioc_unregister_yank_from_file(tmp);
qemu_fclose(tmp);
}
assert(!migration_is_active());
if (s->state == MIGRATION_STATUS_CANCELLING) {
migrate_set_state(&s->state, MIGRATION_STATUS_CANCELLING,
MIGRATION_STATUS_CANCELLED);
} else if (s->state == MIGRATION_STATUS_FAILING) {
migrate_set_state(&s->state, MIGRATION_STATUS_FAILING,
MIGRATION_STATUS_FAILED);
}
/*
* FAILED notification should have already happened. Notify DONE if
* migration completed successfully.
*/
if (!migration_has_failed(s)) {
migration_call_notifiers(MIG_EVENT_DONE, NULL);
}
yank_unregister_instance(MIGRATION_YANK_INSTANCE);
}
static void migration_cleanup_bh(void *opaque)
{
MigrationState *s = opaque;
migration_cleanup(s);
if (s->error) {
error_report_err(error_copy(s->error));
}
}
/*
* Propagate the Error* object to migration core. The caller mustn't
* reference the error pointer after the function returned, because the
* Error* object might be freed.
*/
void migrate_error_propagate(MigrationState *s, Error *error)
{
QEMU_LOCK_GUARD(&s->error_mutex);
trace_migrate_error(error_get_pretty(error));
error_propagate(&s->error, error);
}
bool migrate_has_error(MigrationState *s)
{
/* The lock is not helpful here, but still follow the rule */
QEMU_LOCK_GUARD(&s->error_mutex);
return qatomic_read(&s->error);
}
static void migrate_error_free(MigrationState *s)
{
QEMU_LOCK_GUARD(&s->error_mutex);
error_free(s->error);
s->error = NULL;
}
void migration_connect_error_propagate(MigrationState *s, Error *error)
{
MigrationStatus current = s->state;
MigrationStatus next = MIGRATION_STATUS_NONE;
bool resume = false;
switch (current) {
case MIGRATION_STATUS_SETUP:
next = MIGRATION_STATUS_FAILING;
break;
case MIGRATION_STATUS_POSTCOPY_PAUSED:
resume = true;
break;
case MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP:
/* Never fail a postcopy migration; switch back to PAUSED instead */
next = MIGRATION_STATUS_POSTCOPY_PAUSED;
resume = true;
break;
case MIGRATION_STATUS_CANCELLING:
case MIGRATION_STATUS_FAILING:
/*
* Keep the current state, next transition is to be done
* in migration_cleanup().
*/
break;
default:
/*
* This really shouldn't happen. Just be careful to not crash a VM
* just for this. Instead, dump something.
*/
error_report("%s: Illegal migration status (%s) detected",
__func__, MigrationStatus_str(current));
return;
}
if (next) {
migrate_set_state(&s->state, current, next);
}
migrate_error_propagate(s, error);
if (!resume) {
migration_cleanup(s);
}
}
void migration_cancel(void)
{
MigrationState *s = migrate_get_current();
int old_state ;
bool setup = (s->state == MIGRATION_STATUS_SETUP);
trace_migration_cancel();
if (migrate_dirty_limit()) {
qmp_cancel_vcpu_dirty_limit(false, -1, NULL);
}
WITH_QEMU_LOCK_GUARD(&s->qemu_file_lock) {
if (s->rp_state.from_dst_file) {
/* shutdown the rp socket, so causing the rp thread to shutdown */
qemu_file_shutdown(s->rp_state.from_dst_file);
}
}
do {
old_state = s->state;
if (!migration_is_running()) {
break;
}
/* If the migration is paused, kick it out of the pause */
if (old_state == MIGRATION_STATUS_PRE_SWITCHOVER) {
qemu_event_set(&s->pause_event);
}
migrate_set_state(&s->state, old_state, MIGRATION_STATUS_CANCELLING);
} while (s->state != MIGRATION_STATUS_CANCELLING);
/*
* If we're unlucky the migration code might be stuck somewhere in a
* send/write while the network has failed and is waiting to timeout;
* if we've got shutdown(2) available then we can force it to quit.
*/
if (s->state == MIGRATION_STATUS_CANCELLING) {
WITH_QEMU_LOCK_GUARD(&s->qemu_file_lock) {
if (s->to_dst_file) {
qemu_file_shutdown(s->to_dst_file);
}
}
}
/*
* This is cpr-transfer specific processing.
*
* If this is true, it means cpr-transfer migration is waiting for the
* destination to send HUP event on CPR channel to continue the next
* phase. If so, do the cleanup proactively to avoid get stuck in
* CANCELLING state.
*/
if (cpr_transfer_source_active(s)) {
assert(migrate_mode() == MIG_MODE_CPR_TRANSFER);
assert(setup && !s->to_dst_file);
migration_cleanup(s);
/* Now all things should have been released */
assert(!cpr_transfer_source_active(s));
}
}
static void add_notifiers(NotifierWithReturn *notify, unsigned modes)
{
for (MigMode mode = 0; mode < MIG_MODE__MAX; mode++) {
if (modes & BIT(mode)) {
migration_state_notifiers[mode] =
g_slist_prepend(migration_state_notifiers[mode], notify);
}
}
}
void migration_add_notifier_modes(NotifierWithReturn *notify,
MigrationNotifyFunc func, unsigned modes)
{
notify->notify = (NotifierWithReturnFunc)func;
add_notifiers(notify, modes);
}
void migration_add_notifier_mode(NotifierWithReturn *notify,
MigrationNotifyFunc func, MigMode mode)
{
migration_add_notifier_modes(notify, func, BIT(mode));
}
void migration_add_notifier(NotifierWithReturn *notify,
MigrationNotifyFunc func)
{
migration_add_notifier_mode(notify, func, MIG_MODE_NORMAL);
}
void migration_remove_notifier(NotifierWithReturn *notify)
{
if (notify->notify) {
for (MigMode mode = 0; mode < MIG_MODE__MAX; mode++) {
migration_state_notifiers[mode] =
g_slist_remove(migration_state_notifiers[mode], notify);
}
notify->notify = NULL;
}
}
int migration_call_notifiers(MigrationEventType type, Error **errp)
{
MigMode mode = migrate_mode();
MigrationEvent e;
NotifierWithReturn *notifier;
GSList *elem, *next;
int ret;
trace_migration_call_notifiers(type);
e.type = type;
for (elem = migration_state_notifiers[mode]; elem; elem = next) {
next = elem->next;
notifier = (NotifierWithReturn *)elem->data;
ret = notifier->notify(notifier, &e, errp);
if (ret) {
assert(type == MIG_EVENT_SETUP);
return ret;
}
}
return 0;
}
bool migration_has_failed(MigrationState *s)
{
return (s->state == MIGRATION_STATUS_CANCELLING ||
s->state == MIGRATION_STATUS_CANCELLED ||
s->state == MIGRATION_STATUS_FAILING ||
s->state == MIGRATION_STATUS_FAILED);
}
bool migration_in_postcopy(void)
{
MigrationState *s = migrate_get_current();
switch (s->state) {
case MIGRATION_STATUS_POSTCOPY_DEVICE:
case MIGRATION_STATUS_POSTCOPY_ACTIVE:
case MIGRATION_STATUS_POSTCOPY_PAUSED:
case MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP:
case MIGRATION_STATUS_POSTCOPY_RECOVER:
return true;
default:
return false;
}
}
bool migration_postcopy_is_alive(MigrationStatus state)
{
switch (state) {
case MIGRATION_STATUS_POSTCOPY_ACTIVE:
case MIGRATION_STATUS_POSTCOPY_RECOVER:
return true;
default:
return false;
}
}
bool migration_in_incoming_postcopy(void)
{
PostcopyState ps = postcopy_state_get();
return ps >= POSTCOPY_INCOMING_DISCARD && ps < POSTCOPY_INCOMING_END;
}
bool migration_guest_ram_loading(void)
{
return runstate_check(RUN_STATE_INMIGRATE) ||
migration_in_incoming_postcopy();
}
bool migration_incoming_postcopy_advised(void)
{
PostcopyState ps = postcopy_state_get();
return ps >= POSTCOPY_INCOMING_ADVISE && ps < POSTCOPY_INCOMING_END;
}
bool migration_in_bg_snapshot(void)
{
return migrate_background_snapshot() && migration_is_running();
}
bool migration_thread_is_self(void)
{
MigrationState *s = migrate_get_current();
return qemu_thread_is_self(&s->thread);
}
bool migrate_mode_is_cpr(void)
{
MigMode mode = migrate_mode();
return mode == MIG_MODE_CPR_REBOOT ||
mode == MIG_MODE_CPR_TRANSFER ||
mode == MIG_MODE_CPR_EXEC;
}
int migrate_init(MigrationState *s, Error **errp)
{
int ret;
ret = qemu_savevm_state_prepare(errp);
if (ret) {
return ret;
}
/*
* Reinitialise all migration state, except
* parameters/capabilities that the user set, and
* locks.
*/
s->to_dst_file = NULL;
s->state = MIGRATION_STATUS_NONE;
s->rp_state.from_dst_file = NULL;
s->mbps = 0.0;
s->pages_per_second = 0.0;
s->downtime = 0;
s->setup_time = 0;
s->start_postcopy = false;
s->migration_thread_running = false;
migrate_error_free(s);
if (should_send_vmdesc()) {
s->vmdesc = json_writer_new(false);
}
migrate_set_state(&s->state, MIGRATION_STATUS_NONE, MIGRATION_STATUS_SETUP);
s->start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
s->total_time = 0;
s->vm_old_state = -1;
s->iteration_initial_bytes = 0;
s->threshold_size = 0;
/* Legacy switchover-ack sends a single ACK for all devices */
qatomic_set(&s->switchover_ack_pending_num,
migrate_switchover_ack_legacy() ? 1 : 0);
s->rdma_migration = false;
/*
* set mig_stats memory to zero for a new migration.. except the
* iteration counter, which we want to make sure it returns 1 for the
* first iteration.
*/
memset(&mig_stats, 0, sizeof(mig_stats));
mig_stats.dirty_sync_count = 1;
migration_reset_vfio_bytes_transferred();
s->postcopy_package_loaded = false;
return 0;
}
static bool is_busy(Error **reasonp, Error **errp)
{
ERRP_GUARD();
/* Snapshots are similar to migrations, so check RUN_STATE_SAVE_VM too. */
if (runstate_check(RUN_STATE_SAVE_VM) || migration_is_running()) {
error_propagate_prepend(errp, *reasonp,
"disallowing migration blocker "
"(migration/snapshot in progress) for: ");
*reasonp = NULL;
return true;
}
return false;
}
static bool is_only_migratable(Error **reasonp, unsigned modes, Error **errp)
{
ERRP_GUARD();
if (only_migratable && (modes & BIT(MIG_MODE_NORMAL))) {
error_propagate_prepend(errp, *reasonp,
"disallowing migration blocker "
"(--only-migratable) for: ");
*reasonp = NULL;
return true;
}
return false;
}
static int add_blockers(Error **reasonp, unsigned modes, Error **errp)
{
for (MigMode mode = 0; mode < MIG_MODE__MAX; mode++) {
if (modes & BIT(mode)) {
assert(g_slist_index(migration_blockers[mode],
*reasonp) == -1);
migration_blockers[mode] = g_slist_prepend(migration_blockers[mode],
*reasonp);
}
}
return 0;
}
int migrate_add_blocker(Error **reasonp, Error **errp)
{
return migrate_add_blocker_modes(reasonp, -1u, errp);
}
int migrate_add_blocker_normal(Error **reasonp, Error **errp)
{
return migrate_add_blocker_modes(reasonp, BIT(MIG_MODE_NORMAL), errp);
}
int migrate_add_blocker_modes(Error **reasonp, unsigned modes, Error **errp)
{
if (is_only_migratable(reasonp, modes, errp)) {
return -EACCES;
} else if (is_busy(reasonp, errp)) {
return -EBUSY;
}
return add_blockers(reasonp, modes, errp);
}
int migrate_add_blocker_internal(Error **reasonp, Error **errp)
{
unsigned modes = BIT(MIG_MODE__MAX) - 1;
if (is_busy(reasonp, errp)) {
return -EBUSY;
}
return add_blockers(reasonp, modes, errp);
}
void migrate_del_blocker(Error **reasonp)
{
if (*reasonp) {
for (MigMode mode = 0; mode < MIG_MODE__MAX; mode++) {
migration_blockers[mode] = g_slist_remove(migration_blockers[mode],
*reasonp);
}
error_free(*reasonp);
*reasonp = NULL;
}
}
void qmp_migrate_incoming(const char *uri, bool has_channels,
MigrationChannelList *channels,
bool has_exit_on_error, bool exit_on_error,
Error **errp)
{
Error *local_err = NULL;
static bool once = true;
MigrationIncomingState *mis = migration_incoming_get_current();
if (!once) {
error_setg(errp, "The incoming migration has already been started");
return;
}
if (!runstate_check(RUN_STATE_INMIGRATE)) {
error_setg(errp, "'-incoming' was not specified on the command line");
return;
}
if (!yank_register_instance(MIGRATION_YANK_INSTANCE, errp)) {
return;
}
mis->exit_on_error =
has_exit_on_error ? exit_on_error : INMIGRATE_DEFAULT_EXIT_ON_ERROR;
qemu_setup_incoming_migration(uri, has_channels, channels, &local_err);
if (local_err) {
yank_unregister_instance(MIGRATION_YANK_INSTANCE);
error_propagate(errp, local_err);
return;
}
/*
* Making sure MigrationState is available until incoming migration
* completes.
*
* NOTE: QEMU _might_ leak this refcount in some failure paths, but
* that's OK. This is the minimum change we need to at least making
* sure success case is clean on the refcount. We can try harder to
* make it accurate for any kind of failures, but it might be an
* overkill and doesn't bring us much benefit.
*/
migrate_incoming_ref_outgoing_state();
once = false;
}
void qmp_migrate_recover(const char *uri, Error **errp)
{
MigrationIncomingState *mis = migration_incoming_get_current();
/*
* Don't even bother to use ERRP_GUARD() as it _must_ always be set by
* callers (no one should ignore a recover failure); if there is, it's a
* programming error.
*/
assert(errp);
if (mis->state != MIGRATION_STATUS_POSTCOPY_PAUSED) {
error_setg(errp, "Migrate recover can only be run "
"when postcopy is paused.");
return;
}
/* If there's an existing transport, release it */
migration_incoming_transport_cleanup(mis);
/*
* Note that this call will never start a real migration; it will
* only re-setup the migration stream and poke existing migration
* to continue using that newly established channel.
*/
qemu_setup_incoming_migration(uri, false, NULL, errp);
}
void qmp_migrate_pause(Error **errp)
{
MigrationState *ms = migrate_get_current();
MigrationIncomingState *mis = migration_incoming_get_current();
int ret = 0;
if (migration_postcopy_is_alive(ms->state)) {
/* Source side, during postcopy */
Error *error = NULL;
/* Tell the core migration that we're pausing */
error_setg(&error, "Postcopy migration is paused by the user");
migrate_error_propagate(ms, error);
qemu_mutex_lock(&ms->qemu_file_lock);
if (ms->to_dst_file) {
ret = qemu_file_shutdown(ms->to_dst_file);
}
qemu_mutex_unlock(&ms->qemu_file_lock);
if (ret) {
error_setg(errp, "Failed to pause source migration");
}
/*
* Kick the migration thread out of any waiting windows (on behalf
* of the rp thread).
*/
migration_rp_kick(ms);
return;
}
if (migration_postcopy_is_alive(mis->state)) {
ret = qemu_file_shutdown(mis->from_src_file);
if (ret) {
error_setg(errp, "Failed to pause destination migration");
}
return;
}
error_setg(errp, "migrate-pause is currently only supported "
"during postcopy-active or postcopy-recover state");
}
bool migration_is_blocked(Error **errp)
{
GSList *blockers = migration_blockers[migrate_mode()];
if (qemu_savevm_state_blocked(errp)) {
return true;
}
if (blockers) {
error_propagate(errp, error_copy(blockers->data));
return true;
}
return false;
}
/* Returns true if continue to migrate, or false if error detected */
static bool migrate_prepare(MigrationState *s, bool resume, Error **errp)
{
if (resume) {
if (s->state != MIGRATION_STATUS_POSTCOPY_PAUSED) {
error_setg(errp, "Cannot resume if there is no "
"paused migration");
return false;
}
/*
* Postcopy recovery won't work well with release-ram
* capability since release-ram will drop the page buffer as
* long as the page is put into the send buffer. So if there
* is a network failure happened, any page buffers that have
* not yet reached the destination VM but have already been
* sent from the source VM will be lost forever. Let's refuse
* the client from resuming such a postcopy migration.
* Luckily release-ram was designed to only be used when src
* and destination VMs are on the same host, so it should be
* fine.
*/
if (migrate_release_ram()) {
error_setg(errp, "Postcopy recovery cannot work "
"when release-ram capability is set");
return false;
}
migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_PAUSED,
MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP);
/*
* If there's a previous error, free it and prepare for
* another one. For the non-resume case, this happens at
* migrate_init() below.
*/
migrate_error_free(s);
/* This is a resume, skip init status */
return true;
}
if (migration_is_running()) {
error_setg(errp, "There's a migration process in progress");
return false;
}
if (runstate_check(RUN_STATE_INMIGRATE)) {
error_setg(errp, "Guest is waiting for an incoming migration");
return false;
}
if (runstate_check(RUN_STATE_POSTMIGRATE)) {
error_setg(errp, "Can't migrate the vm that was paused due to "
"previous migration");
return false;
}
if (kvm_hwpoisoned_mem()) {
error_setg(errp, "Can't migrate this vm with hardware poisoned memory, "
"please reboot the vm and try again");
return false;
}
if (migrate_mode() == MIG_MODE_CPR_EXEC &&
!s->parameters.cpr_exec_command) {
error_setg(errp, "cpr-exec mode requires setting cpr-exec-command");
return false;
}
if (migration_is_blocked(errp)) {
return false;
}
if (migrate_mapped_ram()) {
if (migrate_tls()) {
error_setg(errp, "Cannot use TLS with mapped-ram");
return false;
}
if (migrate_multifd_compression()) {
error_setg(errp, "Cannot use compression with mapped-ram");
return false;
}
if (migrate_postcopy_ram()) {
error_setg(errp, "Cannot migrate with fast snapshot load "
"enabled(mapped-ram + postcopy-ram)");
return false;
}
}
if (migrate_mode_is_cpr()) {
const char *conflict = NULL;
if (migrate_postcopy()) {
conflict = "postcopy";
} else if (migrate_background_snapshot()) {
conflict = "background snapshot";
} else if (migrate_colo()) {
conflict = "COLO";
}
if (conflict) {
error_setg(errp, "Cannot use %s with CPR", conflict);
return false;
}
if (s->parameters.mode == MIG_MODE_CPR_EXEC &&
!s->parameters.cpr_exec_command) {
error_setg(errp, "Parameter 'cpr-exec-command' required for cpr-exec");
return false;
}
}
if (migrate_init(s, errp)) {
return false;
}
yank_register_instance(MIGRATION_YANK_INSTANCE, &error_abort);
return true;
}
static gboolean migration_connect_outgoing_cb(QIOChannel *channel,
GIOCondition cond, void *opaque)
{
MigrationState *s = migrate_get_current();
Error *local_err = NULL;
/*
* Detach and release the GSource right after use. We rely on this to
* detect this small cpr-transfer window of "waiting for HUP event".
*/
cpr_transfer_source_destroy(s);
migration_connect_outgoing(s, opaque, &local_err);
if (local_err) {
migration_connect_error_propagate(s, local_err);
}
/*
* This is redundant as we do cpr_transfer_source_destroy() at the
* entry, but it's benign; glib will just skip the detach.
*/
return G_SOURCE_REMOVE;
}
void qmp_migrate(const char *uri, bool has_channels,
MigrationChannelList *channels,
bool has_resume, bool resume, Error **errp)
{
MigrationState *s = migrate_get_current();
g_autoptr(MigrationChannel) main_ch = NULL;
g_autoptr(MigrationChannel) cpr_ch = NULL;
if (!migration_channel_parse_input(uri, channels, &main_ch, &cpr_ch,
errp)) {
return;
}
/* transport mechanism not suitable for migration? */
if (!migration_transport_compatible(main_ch->addr, errp)) {
return;
}
if (!migrate_prepare(s, has_resume && resume, errp)) {
/* Error detected, put into errp */
return;
}
/*
* The migrate_prepare() above calls migrate_init(). From this
* point on, until the end of migration, make sure any failures
* eventually result in a call to migration_cleanup().
*/
Error *local_err = NULL;
if (!cpr_state_save(cpr_ch, &local_err)) {
goto out;
}
/*
* For cpr-transfer, the target may not be listening yet on the migration
* channel, because first it must finish cpr_load_state. The target tells
* us it is listening by closing the cpr-state socket. Wait for that HUP
* event before connecting in migration_connect_outgoing.
*
* The HUP could occur because the target fails while reading CPR state,
* in which case the target will not listen for the incoming migration
* connection, so migration_connect_outgoing will fail to connect,
* and then recover.
*/
if (migrate_mode() == MIG_MODE_CPR_TRANSFER) {
cpr_transfer_add_hup_watch(s, migration_connect_outgoing_cb,
main_ch->addr);
} else {
migration_connect_outgoing(s, main_ch->addr, &local_err);
}
out:
if (local_err) {
migration_connect_error_propagate(s, error_copy(local_err));
error_propagate(errp, local_err);
}
}
void qmp_migrate_cancel(Error **errp)
{
/*
* After postcopy migration has started, the source machine is not
* recoverable in case of a migration error. This also means the
* cancel command cannot be used as cancel should allow the
* machine to continue operation.
*/
if (migration_in_postcopy()) {
error_setg(errp, "Postcopy migration in progress, cannot cancel.");
return;
}
migration_cancel();
}
void qmp_migrate_continue(MigrationStatus state, Error **errp)
{
MigrationState *s = migrate_get_current();
if (s->state != state) {
error_setg(errp, "Migration not in expected state: %s",
MigrationStatus_str(s->state));
return;
}
qemu_event_set(&s->pause_event);
}
int migration_rp_wait(MigrationState *s)
{
/* If migration has failure already, ignore the wait */
if (migrate_has_error(s)) {
return -1;
}
qemu_sem_wait(&s->rp_state.rp_sem);
/* After wait, double check that there's no failure */
if (migrate_has_error(s)) {
return -1;
}
return 0;
}
void migration_rp_kick(MigrationState *s)
{
qemu_sem_post(&s->rp_state.rp_sem);
}
/* This is called only on destination side */
void migration_request_switchover_ack_legacy(const char *requester)
{
MigrationIncomingState *mis = migration_incoming_get_current();
if (!migrate_switchover_ack() || !migrate_switchover_ack_legacy()) {
return;
}
mis->switchover_ack_pending_num_legacy++;
trace_migration_request_switchover_ack_legacy(
requester, mis->switchover_ack_pending_num_legacy);
}
static struct rp_cmd_args {
ssize_t len; /* -1 = variable */
const char *name;
} rp_cmd_args[] = {
[MIG_RP_MSG_INVALID] = { .len = -1, .name = "INVALID" },
[MIG_RP_MSG_SHUT] = { .len = 4, .name = "SHUT" },
[MIG_RP_MSG_PONG] = { .len = 4, .name = "PONG" },
[MIG_RP_MSG_REQ_PAGES] = { .len = 12, .name = "REQ_PAGES" },
[MIG_RP_MSG_REQ_PAGES_ID] = { .len = -1, .name = "REQ_PAGES_ID" },
[MIG_RP_MSG_RECV_BITMAP] = { .len = -1, .name = "RECV_BITMAP" },
[MIG_RP_MSG_RESUME_ACK] = { .len = 4, .name = "RESUME_ACK" },
[MIG_RP_MSG_SWITCHOVER_ACK] = { .len = 0, .name = "SWITCHOVER_ACK" },
[MIG_RP_MSG_MAX] = { .len = -1, .name = "MAX" },
};
/*
* Process a request for pages received on the return path,
* We're allowed to send more than requested (e.g. to round to our page size)
* and we don't need to send pages that have already been sent.
*/
static void
migrate_handle_rp_req_pages(MigrationState *ms, const char* rbname,
ram_addr_t start, size_t len, Error **errp)
{
long our_host_ps = qemu_real_host_page_size();
trace_migrate_handle_rp_req_pages(rbname, start, len);
/*
* Since we currently insist on matching page sizes, just sanity check
* we're being asked for whole host pages.
*/
if (!QEMU_IS_ALIGNED(start, our_host_ps) ||
!QEMU_IS_ALIGNED(len, our_host_ps)) {
error_setg(errp, "MIG_RP_MSG_REQ_PAGES: Misaligned page request, start:"
RAM_ADDR_FMT " len: %zd", start, len);
return;
}
ram_save_queue_pages(rbname, start, len, errp);
}
static bool migrate_handle_rp_recv_bitmap(MigrationState *s, char *block_name,
Error **errp)
{
RAMBlock *block = qemu_ram_block_by_name(block_name);
if (!block) {
error_setg(errp, "MIG_RP_MSG_RECV_BITMAP has invalid block name '%s'",
block_name);
return false;
}
/* Fetch the received bitmap and refresh the dirty bitmap */
return ram_dirty_bitmap_reload(s, block, errp);
}
static bool migrate_handle_rp_resume_ack(MigrationState *s,
uint32_t value, Error **errp)
{
trace_source_return_path_thread_resume_ack(value);
if (value != MIGRATION_RESUME_ACK_VALUE) {
error_setg(errp, "illegal resume_ack value %"PRIu32, value);
return false;
}
/* Now both sides are active. */
migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_RECOVER,
MIGRATION_STATUS_POSTCOPY_ACTIVE);
/* Notify send thread that time to continue send pages */
migration_rp_kick(s);
return true;
}
/*
* Release ms->rp_state.from_dst_file (and postcopy_qemufile_src if
* existed) in a safe way.
*/
static void migration_release_dst_files(MigrationState *ms)
{
QEMUFile *file = NULL;
WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) {
/*
* Reset the from_dst_file pointer first before releasing it, as we
* can't block within lock section
*/
file = ms->rp_state.from_dst_file;
ms->rp_state.from_dst_file = NULL;
}
/*
* Do the same to postcopy fast path socket too if there is. No
* locking needed because this qemufile should only be managed by
* return path thread.
*/
assert(!ms->rp_state.rp_thread_created);
if (ms->postcopy_qemufile_src) {
migration_ioc_unregister_yank_from_file(ms->postcopy_qemufile_src);
qemu_file_shutdown(ms->postcopy_qemufile_src);
qemu_fclose(ms->postcopy_qemufile_src);
ms->postcopy_qemufile_src = NULL;
}
if (file) {
qemu_fclose(file);
}
}
/*
* Handles messages sent on the return path towards the source VM
*
*/
static void *source_return_path_thread(void *opaque)
{
MigrationState *ms = opaque;
QEMUFile *rp = ms->rp_state.from_dst_file;
uint16_t header_len, header_type;
uint8_t buf[512];
uint32_t tmp32, sibling_error;
ram_addr_t start = 0; /* =0 to silence warning */
size_t len = 0, expected_len;
Error *err = NULL;
int res;
trace_source_return_path_thread_entry();
rcu_register_thread();
while (migration_is_running()) {
trace_source_return_path_thread_loop_top();
header_type = qemu_get_be16(rp);
header_len = qemu_get_be16(rp);
if (qemu_file_get_error(rp)) {
qemu_file_get_error_obj(rp, &err);
goto out;
}
if (header_type >= MIG_RP_MSG_MAX ||
header_type == MIG_RP_MSG_INVALID) {
error_setg(&err, "Received invalid message 0x%04x length 0x%04x",
header_type, header_len);
goto out;
}
if ((rp_cmd_args[header_type].len != -1 &&
header_len != rp_cmd_args[header_type].len) ||
header_len > sizeof(buf)) {
error_setg(&err, "Received '%s' message (0x%04x) with"
"incorrect length %d expecting %zu",
rp_cmd_args[header_type].name, header_type, header_len,
(size_t)rp_cmd_args[header_type].len);
goto out;
}
/* We know we've got a valid header by this point */
res = qemu_get_buffer(rp, buf, header_len);
if (res != header_len) {
error_setg(&err, "Failed reading data for message 0x%04x"
" read %d expected %d",
header_type, res, header_len);
goto out;
}
/* OK, we have the message and the data */
switch (header_type) {
case MIG_RP_MSG_SHUT:
sibling_error = ldl_be_p(buf);
trace_source_return_path_thread_shut(sibling_error);
if (sibling_error) {
error_setg(&err, "Sibling indicated error %d", sibling_error);
}
/*
* We'll let the main thread deal with closing the RP
* we could do a shutdown(2) on it, but we're the only user
* anyway, so there's nothing gained.
*/
goto out;
case MIG_RP_MSG_PONG:
tmp32 = ldl_be_p(buf);
trace_source_return_path_thread_pong(tmp32);
qemu_sem_post(&ms->rp_state.rp_pong_acks);
if (tmp32 == QEMU_VM_PING_PACKAGED_LOADED) {
trace_source_return_path_thread_postcopy_package_loaded();
ms->postcopy_package_loaded = true;
migration_rp_kick(ms);
}
break;
case MIG_RP_MSG_REQ_PAGES:
start = ldq_be_p(buf);
len = ldl_be_p(buf + 8);
migrate_handle_rp_req_pages(ms, NULL, start, len, &err);
if (err) {
goto out;
}
break;
case MIG_RP_MSG_REQ_PAGES_ID:
expected_len = 12 + 1; /* header + termination */
if (header_len >= expected_len) {
start = ldq_be_p(buf);
len = ldl_be_p(buf + 8);
/* Now we expect an idstr */
tmp32 = buf[12]; /* Length of the following idstr */
buf[13 + tmp32] = '\0';
expected_len += tmp32;
}
if (header_len != expected_len) {
error_setg(&err, "Req_Page_id with length %d expecting %zd",
header_len, expected_len);
goto out;
}
migrate_handle_rp_req_pages(ms, (char *)&buf[13], start, len,
&err);
if (err) {
goto out;
}
break;
case MIG_RP_MSG_RECV_BITMAP:
if (header_len < 1) {
error_setg(&err, "MIG_RP_MSG_RECV_BITMAP missing block name");
goto out;
}
/* Format: len (1B) + idstr (<255B). This ends the idstr. */
buf[buf[0] + 1] = '\0';
if (!migrate_handle_rp_recv_bitmap(ms, (char *)(buf + 1), &err)) {
goto out;
}
break;
case MIG_RP_MSG_RESUME_ACK:
tmp32 = ldl_be_p(buf);
if (!migrate_handle_rp_resume_ack(ms, tmp32, &err)) {
goto out;
}
break;
case MIG_RP_MSG_SWITCHOVER_ACK:
{
uint32_t pending_num;
pending_num = qatomic_dec_fetch(&ms->switchover_ack_pending_num);
trace_source_return_path_thread_switchover_acked(pending_num);
if (pending_num == UINT32_MAX) {
error_setg(&err, "Switchover ack pending num underflowed");
goto out;
}
break;
}
default:
break;
}
}
out:
if (err) {
migrate_error_propagate(ms, err);
trace_source_return_path_thread_bad_end();
}
if (ms->state == MIGRATION_STATUS_POSTCOPY_RECOVER ||
ms->state == MIGRATION_STATUS_POSTCOPY_DEVICE) {
/*
* The migration thread can get stuck waiting for rp_sem if the
* return path fails to sync with the destination. This handles
* two specific cases:
*
* POSTCOPY_RECOVER: A failure occurs during a recovery attempt.
* We kick the migration thread back to PAUSED so the admin can
* retry.
*
* POSTCOPY_DEVICE: The MIG_RP_MSG_PONG is lost due to a
* network failure or destination crash. We kick the migration
* thread out of its wait so it can fail the migration and safely
* resume the VM on the source.
*/
migration_rp_kick(ms);
}
trace_source_return_path_thread_end();
rcu_unregister_thread();
return NULL;
}
static void open_return_path_on_source(MigrationState *ms)
{
ms->rp_state.from_dst_file = qemu_file_get_return_path(ms->to_dst_file);
trace_open_return_path_on_source();
qemu_thread_create(&ms->rp_state.rp_thread, MIGRATION_THREAD_SRC_RETURN,
source_return_path_thread, ms, QEMU_THREAD_JOINABLE);
ms->rp_state.rp_thread_created = true;
trace_open_return_path_on_source_continue();
}
/* Return true if error detected, or false otherwise */
static bool stop_return_path_thread_on_source(MigrationState *ms)
{
if (!ms->rp_state.rp_thread_created) {
return false;
}
trace_migration_return_path_end_before();
/*
* If this is a normal exit then the destination will send a SHUT
* and the rp_thread will exit, however if there's an error we
* need to cause it to exit. shutdown(2), if we have it, will
* cause it to unblock if it's stuck waiting for the destination.
*/
WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) {
if (migrate_has_error(ms) && ms->rp_state.from_dst_file) {
qemu_file_shutdown(ms->rp_state.from_dst_file);
}
}
qemu_thread_join(&ms->rp_state.rp_thread);
ms->rp_state.rp_thread_created = false;
trace_migration_return_path_end_after();
/* Return path will persist the error in MigrationState when quit */
return migrate_has_error(ms);
}
static inline void
migration_wait_main_channel(MigrationState *ms)
{
/* Wait until one PONG message received */
qemu_sem_wait(&ms->rp_state.rp_pong_acks);
}
/*
* Switch from normal iteration to postcopy
* Returns non-0 on error
*/
static int postcopy_start(MigrationState *ms, Error **errp)
{
int ret;
QIOChannelBuffer *bioc;
QEMUFile *fb;
/*
* Now we're 100% sure to switch to postcopy, so JSON writer won't be
* useful anymore. Free the resources early if it is there. Clearing
* the vmdesc also means any follow up vmstate_save()s will start to
* skip all JSON operations, which can shrink postcopy downtime.
*/
migration_cleanup_json_writer(ms);
if (migrate_postcopy_preempt()) {
migration_wait_main_channel(ms);
if (postcopy_preempt_establish_channel(ms)) {
if (ms->state != MIGRATION_STATUS_CANCELLING) {
migrate_set_state(&ms->state, ms->state,
MIGRATION_STATUS_FAILING);
}
error_setg(errp, "%s: Failed to establish preempt channel",
__func__);
return -1;
}
}
if (!qemu_savevm_state_postcopy_prepare(ms->to_dst_file, errp)) {
return -1;
}
trace_postcopy_start();
bql_lock();
trace_postcopy_start_set_run();
ret = migration_stop_vm(ms, RUN_STATE_FINISH_MIGRATE);
if (ret < 0) {
error_setg_errno(errp, -ret, "%s: Failed to stop the VM", __func__);
goto fail;
}
if (!migration_switchover_start(ms, errp)) {
goto fail;
}
/*
* Cause any non-postcopiable, but iterative devices to
* send out their final data.
*/
ret = qemu_savevm_state_complete_precopy_iterable(ms->to_dst_file, true);
if (ret) {
error_setg(errp, "Postcopy save non-postcopiable iterables failed");
goto fail;
}
/*
* in Finish migrate and with the io-lock held everything should
* be quiet, but we've potentially still got dirty pages and we
* need to tell the destination to throw any pages it's already received
* that are dirty
*/
if (migrate_postcopy_ram()) {
ram_postcopy_send_discard_bitmap(ms);
}
if (migrate_postcopy_ram()) {
/* Ping just for debugging, helps line traces up */
qemu_savevm_send_ping(ms->to_dst_file, 2);
}
/*
* While loading the device state we may trigger page transfer
* requests and the fd must be free to process those, and thus
* the destination must read the whole device state off the fd before
* it starts processing it. Unfortunately the ad-hoc migration format
* doesn't allow the destination to know the size to read without fully
* parsing it through each devices load-state code (especially the open
* coded devices that use get/put).
* So we wrap the device state up in a package with a length at the start;
* to do this we use a qemu_buf to hold the whole of the device state.
*/
bioc = qio_channel_buffer_new(4096);
qio_channel_set_name(QIO_CHANNEL(bioc), "migration-postcopy-buffer");
fb = qemu_file_new_output(QIO_CHANNEL(bioc));
object_unref(OBJECT(bioc));
/*
* Make sure the receiver can get incoming pages before we send the rest
* of the state
*/
qemu_savevm_send_postcopy_listen(fb);
if (!qemu_savevm_state_non_iterable(fb, errp)) {
error_prepend(errp, "Postcopy save non-iterable states failed: ");
goto fail_closefb;
}
if (migrate_postcopy_ram()) {
qemu_savevm_send_ping(fb, 3);
}
if (ms->rp_state.rp_thread_created) {
/*
* This ping will tell us that all non-postcopiable device state has been
* successfully loaded and the destination is about to start. When
* response is received, it will trigger transition from POSTCOPY_DEVICE
* to POSTCOPY_ACTIVE state.
*/
qemu_savevm_send_ping(fb, QEMU_VM_PING_PACKAGED_LOADED);
}
qemu_savevm_send_postcopy_run(fb);
/* <><> end of stuff going into the package */
/* Last point of recovery; as soon as we send the package the destination
* can open devices and potentially start running.
* Lets just check again we've not got any errors.
*/
ret = qemu_file_get_error(ms->to_dst_file);
if (ret) {
error_setg(errp, "postcopy_start: Migration stream errored (pre package)");
goto fail_closefb;
}
/* Now send that blob */
if (qemu_savevm_send_packaged(ms->to_dst_file, bioc->data, bioc->usage)) {
error_setg(errp, "%s: Failed to send packaged data", __func__);
goto fail_closefb;
}
qemu_fclose(fb);
/* Send a notify to give a chance for anything that needs to happen
* at the transition to postcopy and after the device state; in particular
* spice needs to trigger a transition now
*/
migration_call_notifiers(MIG_EVENT_POSTCOPY_START, NULL);
migration_downtime_end(ms);
if (migrate_postcopy_ram()) {
/*
* Although this ping is just for debug, it could potentially be
* used for getting a better measurement of downtime at the source.
*/
qemu_savevm_send_ping(ms->to_dst_file, 4);
}
if (migrate_release_ram()) {
ram_postcopy_migrated_memory_release(ms);
}
ret = qemu_file_get_error(ms->to_dst_file);
if (ret) {
error_setg_errno(errp, -ret, "postcopy_start: Migration stream error");
goto fail;
}
trace_postcopy_preempt_enabled(migrate_postcopy_preempt());
/*
* Now postcopy officially started, switch to postcopy bandwidth that
* user specified.
*/
migration_rate_set(migrate_max_postcopy_bandwidth());
/*
* Now, switchover looks all fine, switching to POSTCOPY_DEVICE, or
* directly to POSTCOPY_ACTIVE if there is no return path.
*/
migrate_set_state(&ms->state, MIGRATION_STATUS_DEVICE,
ms->rp_state.rp_thread_created ?
MIGRATION_STATUS_POSTCOPY_DEVICE :
MIGRATION_STATUS_POSTCOPY_ACTIVE);
bql_unlock();
return ret;
fail_closefb:
qemu_fclose(fb);
fail:
if (ms->state != MIGRATION_STATUS_CANCELLING) {
migrate_set_state(&ms->state, ms->state, MIGRATION_STATUS_FAILING);
}
bql_unlock();
return -1;
}
/**
* @migration_switchover_prepare: Start VM switchover procedure
*
* @s: The migration state object pointer
*
* Prepares for the switchover, depending on "pause-before-switchover"
* capability.
*
* If cap set, state machine goes like:
* [postcopy-]active -> pre-switchover -> device
*
* If cap not set:
* [postcopy-]active -> device
*
* Returns: true on success, false on interruptions.
*/
static bool migration_switchover_prepare(MigrationState *s)
{
/* Concurrent cancellation? Quit */
if (s->state == MIGRATION_STATUS_CANCELLING) {
return false;
}
/*
* No matter precopy or postcopy, since we still hold BQL it must not
* change concurrently to CANCELLING, so it must be either ACTIVE or
* POSTCOPY_ACTIVE.
*/
assert(migration_is_active());
/* If the pre stage not requested, directly switch to DEVICE */
if (!migrate_pause_before_switchover()) {
migrate_set_state(&s->state, s->state, MIGRATION_STATUS_DEVICE);
return true;
}
/*
* Since leaving this state is not atomic with setting the event
* it's possible that someone could have issued multiple migrate_continue
* and the event is incorrectly set at this point so reset it.
*/
qemu_event_reset(&s->pause_event);
/* Update [POSTCOPY_]ACTIVE to PRE_SWITCHOVER */
migrate_set_state(&s->state, s->state, MIGRATION_STATUS_PRE_SWITCHOVER);
bql_unlock();
qemu_event_wait(&s->pause_event);
bql_lock();
/*
* After BQL released and retaken, the state can be CANCELLING if it
* happened during sem_wait().. Only change the state if it's still
* pre-switchover.
*/
migrate_set_state(&s->state, MIGRATION_STATUS_PRE_SWITCHOVER,
MIGRATION_STATUS_DEVICE);
return s->state == MIGRATION_STATUS_DEVICE;
}
static bool migration_switchover_start(MigrationState *s, Error **errp)
{
ERRP_GUARD();
MigPendingData pending = {};
if (!migration_switchover_prepare(s)) {
error_setg(errp, "Switchover is interrupted");
return false;
}
/*
* The final query to the whole system on dirty data to make sure we
* collect the latest status of the VM. For precopy, source QEMU will
* dump all the dirty data during switchover. For postcopy, this will
* properly update all the dirty bitmaps to finally generate the
* correct discard bitmaps; see ram_postcopy_send_discard_bitmap().
*/
if (!qemu_savevm_query_pending_final(s, &pending, errp)) {
return false;
}
/* Inactivate disks except in COLO */
if (!migrate_colo()) {
/*
* Inactivate before sending QEMU_VM_EOF so that the
* bdrv_activate_all() on the other end won't fail.
*/
if (!migration_block_inactivate()) {
error_setg(errp, "Block inactivate failed during switchover");
return false;
}
}
migration_rate_set(RATE_LIMIT_DISABLED);
precopy_notify_complete();
qemu_savevm_maybe_send_switchover_start(s->to_dst_file);
return true;
}
static bool migration_completion_precopy(MigrationState *s, Error **errp)
{
bool ret = false;
bql_lock();
if (!migrate_mode_is_cpr()) {
int r = migration_stop_vm(s, RUN_STATE_FINISH_MIGRATE);
if (r < 0) {
error_setg_errno(errp, -r, "Failed to stop the VM");
goto out_unlock;
}
}
if (!migration_switchover_start(s, errp)) {
goto out_unlock;
}
ret = qemu_savevm_state_complete_precopy(s, errp);
out_unlock:
bql_unlock();
return ret;
}
static void migration_completion_postcopy(MigrationState *s)
{
trace_migration_completion_postcopy_end();
bql_lock();
qemu_savevm_state_complete_postcopy(s->to_dst_file);
bql_unlock();
/*
* Shutdown the postcopy fast path thread. This is only needed when dest
* QEMU binary is old (7.1/7.2). QEMU 8.0+ doesn't need this.
*/
if (migrate_postcopy_preempt() && s->preempt_pre_7_2) {
postcopy_preempt_shutdown_file(s);
}
trace_migration_completion_postcopy_end_after_complete();
}
/**
* migration_completion: Used by migration_thread when there's not much left.
* The caller 'breaks' the loop when this returns.
*
* @s: Current migration state
*/
static void migration_completion(MigrationState *s)
{
Error *local_err = NULL;
if (s->state == MIGRATION_STATUS_ACTIVE) {
if (!migration_completion_precopy(s, &local_err)) {
goto fail;
}
} else if (s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
migration_completion_postcopy(s);
} else {
error_setg(&local_err, "Unexpected migration completion status %s",
MigrationStatus_str(s->state));
goto fail;
}
if (stop_return_path_thread_on_source(s)) {
goto fail;
}
if (qemu_file_get_error(s->to_dst_file)) {
trace_migration_completion_file_err();
goto fail;
}
if (migrate_colo() && s->state == MIGRATION_STATUS_DEVICE) {
/* COLO does not support postcopy */
migrate_set_state(&s->state, MIGRATION_STATUS_DEVICE,
MIGRATION_STATUS_COLO);
} else {
migration_completion_end(s);
}
return;
fail:
if (local_err || qemu_file_get_error_obj(s->to_dst_file, &local_err)) {
migrate_error_propagate(s, local_err);
}
if (s->state != MIGRATION_STATUS_CANCELLING) {
migrate_set_state(&s->state, s->state, MIGRATION_STATUS_FAILING);
}
}
/**
* bg_migration_completion: Used by bg_migration_thread when after all the
* RAM has been saved. The caller 'breaks' the loop when this returns.
*
* @s: Current migration state
*/
static void bg_migration_completion(MigrationState *s)
{
int current_active_state = s->state;
if (s->state == MIGRATION_STATUS_ACTIVE) {
/*
* By this moment we have RAM content saved into the migration stream.
* The next step is to flush the non-RAM content (device state)
* right after the ram content. The device state has been stored into
* the temporary buffer before RAM saving started.
*/
qemu_put_buffer(s->to_dst_file, s->bioc->data, s->bioc->usage);
qemu_fflush(s->to_dst_file);
} else if (s->state == MIGRATION_STATUS_CANCELLING) {
return;
}
if (qemu_file_get_error(s->to_dst_file)) {
trace_migration_completion_file_err();
goto fail;
}
migration_completion_end(s);
return;
fail:
migrate_set_state(&s->state, current_active_state,
MIGRATION_STATUS_FAILING);
}
typedef enum MigThrError {
/* No error detected */
MIG_THR_ERR_NONE = 0,
/* Detected error, but resumed successfully */
MIG_THR_ERR_RECOVERED = 1,
/* Detected fatal error, need to exit */
MIG_THR_ERR_FATAL = 2,
} MigThrError;
static int postcopy_resume_handshake(MigrationState *s)
{
qemu_savevm_send_postcopy_resume(s->to_dst_file);
while (s->state == MIGRATION_STATUS_POSTCOPY_RECOVER) {
if (migration_rp_wait(s)) {
return -1;
}
}
if (s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
return 0;
}
return -1;
}
/* Return zero if success, or <0 for error */
static int postcopy_do_resume(MigrationState *s)
{
int ret;
/*
* Call all the resume_prepare() hooks, so that modules can be
* ready for the migration resume.
*/
ret = qemu_savevm_state_resume_prepare(s);
if (ret) {
error_report("%s: resume_prepare() failure detected: %d",
__func__, ret);
return ret;
}
/*
* If preempt is enabled, re-establish the preempt channel. Note that
* we do it after resume prepare to make sure the main channel will be
* created before the preempt channel. E.g. with weak network, the
* dest QEMU may get messed up with the preempt and main channels on
* the order of connection setup. This guarantees the correct order.
*/
ret = postcopy_preempt_establish_channel(s);
if (ret) {
error_report("%s: postcopy_preempt_establish_channel(): %d",
__func__, ret);
return ret;
}
/*
* Last handshake with destination on the resume (destination will
* switch to postcopy-active afterwards)
*/
ret = postcopy_resume_handshake(s);
if (ret) {
error_report("%s: handshake failed: %d", __func__, ret);
return ret;
}
return 0;
}
/*
* We don't return until we are in a safe state to continue current
* postcopy migration. Returns MIG_THR_ERR_RECOVERED if recovered, or
* MIG_THR_ERR_FATAL if unrecovery failure happened.
*/
static MigThrError postcopy_pause(MigrationState *s)
{
assert(s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);
while (true) {
QEMUFile *file;
/*
* We're already pausing, so ignore any errors on the return
* path and just wait for the thread to finish. It will be
* re-created when we resume.
*/
stop_return_path_thread_on_source(s);
migration_release_dst_files(s);
/*
* Current channel is possibly broken. Release it. Note that this is
* guaranteed even without lock because to_dst_file should only be
* modified by the migration thread. That also guarantees that the
* unregister of yank is safe too without the lock. It should be safe
* even to be within the qemu_file_lock, but we didn't do that to avoid
* taking more mutex (yank_lock) within qemu_file_lock. TL;DR: we make
* the qemu_file_lock critical section as small as possible.
*/
assert(s->to_dst_file);
migration_ioc_unregister_yank_from_file(s->to_dst_file);
qemu_mutex_lock(&s->qemu_file_lock);
file = s->to_dst_file;
s->to_dst_file = NULL;
qemu_mutex_unlock(&s->qemu_file_lock);
qemu_file_shutdown(file);
qemu_fclose(file);
migrate_set_state(&s->state, s->state,
MIGRATION_STATUS_POSTCOPY_PAUSED);
error_report("Detected IO failure for postcopy. "
"Migration paused.");
/*
* We wait until things fixed up. Then someone will setup the
* status back for us.
*/
do {
qemu_sem_wait(&s->postcopy_pause_sem);
} while (postcopy_is_paused(s->state));
if (s->state == MIGRATION_STATUS_POSTCOPY_RECOVER) {
/* Woken up by a recover procedure. Give it a shot */
/* Do the resume logic */
if (postcopy_do_resume(s) == 0) {
/* Let's continue! */
trace_postcopy_pause_continued();
return MIG_THR_ERR_RECOVERED;
} else {
/*
* Something wrong happened during the recovery, let's
* pause again. Pause is always better than throwing
* data away.
*/
continue;
}
} else {
/* This is not right... Time to quit. */
return MIG_THR_ERR_FATAL;
}
}
}
void migration_file_set_error(int ret, Error *err)
{
MigrationState *s = migrate_get_current();
WITH_QEMU_LOCK_GUARD(&s->qemu_file_lock) {
if (s->to_dst_file) {
qemu_file_set_error_obj(s->to_dst_file, ret, err);
} else if (err) {
error_report_err(err);
}
}
}
static MigThrError migration_detect_error(MigrationState *s)
{
int ret;
int state = s->state;
Error *local_error = NULL;
if (state == MIGRATION_STATUS_CANCELLING ||
state == MIGRATION_STATUS_CANCELLED) {
/* End the migration, but don't set the state to failed */
return MIG_THR_ERR_FATAL;
}
/*
* Try to detect any file errors. Note that postcopy_qemufile_src will
* be NULL when postcopy preempt is not enabled.
*/
ret = qemu_file_get_error_obj_any(s->to_dst_file,
s->postcopy_qemufile_src,
&local_error);
if (!ret) {
/* Everything is fine */
assert(!local_error);
return MIG_THR_ERR_NONE;
}
if (local_error) {
migrate_error_propagate(s, local_error);
}
if (state == MIGRATION_STATUS_POSTCOPY_ACTIVE && ret) {
/*
* For postcopy, we allow the network to be down for a
* while. After that, it can be continued by a
* recovery phase.
*/
return postcopy_pause(s);
} else {
/*
* For precopy (or postcopy with error outside IO, or before dest
* starts), we fail with no time.
*/
migrate_set_state(&s->state, state, MIGRATION_STATUS_FAILING);
trace_migration_thread_file_err();
/* Time to stop the migration, now. */
return MIG_THR_ERR_FATAL;
}
}
static void migration_completion_end(MigrationState *s)
{
uint64_t bytes = migration_transferred_bytes();
int64_t end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
int64_t transfer_time;
/*
* Take the BQL here so that query-migrate on the QMP thread sees:
* - atomic update of s->total_time and s->mbps;
* - correct ordering of s->mbps update vs. s->state;
*/
bql_lock();
migration_downtime_end(s);
s->total_time = end_time - s->start_time;
transfer_time = s->total_time - s->setup_time;
if (transfer_time) {
s->mbps = ((double) bytes * 8.0) / transfer_time / 1000;
}
migrate_set_state(&s->state, s->state,
MIGRATION_STATUS_COMPLETED);
bql_unlock();
}
static void update_iteration_initial_status(MigrationState *s)
{
/*
* Update these three fields at the same time to avoid mismatch info lead
* wrong speed calculation.
*/
s->iteration_start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
s->iteration_initial_bytes = migration_transferred_bytes();
s->iteration_initial_pages = ram_get_total_transferred_pages();
}
static void migration_update_counters(MigrationState *s,
int64_t current_time)
{
uint64_t transferred, transferred_pages, time_spent;
uint64_t current_bytes; /* bytes transferred since the beginning */
double switchover_bw_per_ms;
if (current_time < s->iteration_start_time + BUFFER_DELAY) {
return;
}
current_bytes = migration_transferred_bytes();
transferred = current_bytes - s->iteration_initial_bytes;
time_spent = current_time - s->iteration_start_time;
s->mbps = (((double) transferred * 8.0) /
((double) time_spent / 1000.0)) / 1000.0 / 1000.0;
/* NOTE: only update this after bandwidth (s->mbps) updated */
switchover_bw_per_ms = migration_get_switchover_bw(s) / 1000;
s->threshold_size = switchover_bw_per_ms * migrate_downtime_limit();
transferred_pages = ram_get_total_transferred_pages() -
s->iteration_initial_pages;
s->pages_per_second = (double) transferred_pages /
(((double) time_spent / 1000.0));
migration_rate_reset();
update_iteration_initial_status(s);
trace_migrate_transferred(transferred, time_spent,
/* Both in unit bytes/ms */
(uint64_t)s->mbps,
(uint64_t)switchover_bw_per_ms,
s->threshold_size);
}
static bool migration_can_switchover(MigrationState *s)
{
if (!migrate_switchover_ack()) {
return true;
}
/* No reason to wait for switchover ACK if VM is stopped */
if (!runstate_is_running()) {
return true;
}
return qatomic_read(&s->switchover_ack_pending_num) == 0;
}
/* Migration thread iteration status */
typedef enum {
MIG_ITERATE_RESUME, /* Resume current iteration */
MIG_ITERATE_SKIP, /* Skip current iteration */
MIG_ITERATE_BREAK, /* Break the loop */
} MigIterateState;
/* Are we ready to move to the next iteration phase? */
static bool migration_iteration_next_ready(MigrationState *s,
MigPendingData *pending)
{
/*
* If the estimated values already suggest us to switch over, mark this
* iteration finished, time to do a slow sync.
*/
if (pending->total_bytes <= s->threshold_size) {
return true;
}
/*
* Since we may have modules reporting stop-only data, we also want to
* re-query with slow mode if all precopy data is moved over. This
* will also mark the current iteration done.
*
* This could happen when e.g. a module (like, VFIO) reports stopcopy
* size too large so it will never yet satisfy the downtime with the
* current setup (above check). Here, slow version of re-query helps
* because we keep trying the best to move whatever we have.
*/
if (pending->precopy_bytes == 0) {
return true;
}
return false;
}
static void migration_iteration_go_next(MigrationState *s,
MigPendingData *pending)
{
/*
* Do a slow sync first before boosting the iteration count.
*/
qemu_savevm_query_pending_iter(s, pending, true);
/*
* Update the dirty information for the whole system for this
* iteration. This value is used to calculate expected downtime.
*/
qatomic_set(&mig_stats.dirty_bytes_last_sync, pending->total_bytes);
/*
* Boost dirty sync count to reflect we finished one iteration.
*
* NOTE: we need to make sure when this happens (together with the
* event sent below) all modules have slow-synced the pending data
* above and updated corresponding fields (e.g. dirty_bytes_last_sync).
*
* It's because a mgmt could wait on the iteration event to query again
* on pending data for policy changes (e.g. downtime adjustments). The
* ordering will make sure the query will fetch the latest results from
* all the modules on everything.
*/
qatomic_add(&mig_stats.dirty_sync_count, 1);
if (migrate_events()) {
qapi_event_send_migration_pass(mig_stats.dirty_sync_count);
}
}
static bool postcopy_should_start(MigrationState *s, MigPendingData *pending)
{
/* If postcopy's switchver will violate user specified downtime, stop */
if (pending->precopy_bytes + pending->stopcopy_bytes > s->threshold_size) {
return false;
}
return qatomic_read(&s->start_postcopy);
}
/*
* Return true if continue to the next iteration directly, false
* otherwise.
*/
static MigIterateState migration_iteration_run(MigrationState *s)
{
Error *local_err = NULL;
bool in_postcopy = (s->state == MIGRATION_STATUS_POSTCOPY_DEVICE ||
s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);
bool can_switchover;
MigPendingData pending = { };
bool complete_ready;
/* Fast path - get the estimated amount of pending data */
qemu_savevm_query_pending_iter(s, &pending, false);
if (in_postcopy) {
/*
* Iterate in postcopy until all pending data flushed. Note that
* postcopy completion doesn't rely on can_switchover, because when
* POSTCOPY_ACTIVE it means switchover already happened.
*/
complete_ready = !pending.total_bytes;
if (s->state == MIGRATION_STATUS_POSTCOPY_DEVICE &&
(s->postcopy_package_loaded || complete_ready)) {
/*
* We will immediately transition to POSTCOPY_ACTIVE.
* If we are ready for completion, we need to wait for
* destination to load the postcopy package before actually
* completing.
*/
while (!s->postcopy_package_loaded) {
if (migration_rp_wait(s)) {
/*
* Error happened. Migration thread was stuck waiting in
* POSTCOPY_DEVICE for rp_sem which was never set.
*/
migrate_set_state(&s->state,
MIGRATION_STATUS_POSTCOPY_DEVICE,
MIGRATION_STATUS_FAILING);
return MIG_ITERATE_BREAK;
}
}
/* Acknowledgement received from the destination */
migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_DEVICE,
MIGRATION_STATUS_POSTCOPY_ACTIVE);
}
} else {
/*
* Exact pending reporting is only needed for precopy. Taking RAM
* as example, there'll be no extra dirty information after
* postcopy started, so ESTIMATE should always match with EXACT
* during postcopy phase.
*/
if (migration_iteration_next_ready(s, &pending)) {
migration_iteration_go_next(s, &pending);
}
/* Check if we can switch over after qemu_savevm_query_pending() */
can_switchover = migration_can_switchover(s);
/* Should we switch to postcopy now? */
if (can_switchover && postcopy_should_start(s, &pending)) {
if (postcopy_start(s, &local_err)) {
migrate_error_propagate(s, error_copy(local_err));
error_report_err(local_err);
}
return MIG_ITERATE_SKIP;
}
/*
* For precopy, migration can complete only if:
*
* (1) Switchover is acknowledged by destination
* (2) Pending size is no more than the threshold specified
* (which was calculated from expected downtime)
*/
complete_ready = can_switchover &&
(pending.total_bytes <= s->threshold_size);
}
if (complete_ready) {
trace_migration_thread_low_pending(pending.total_bytes);
migration_completion(s);
return MIG_ITERATE_BREAK;
}
/* Just another iteration step */
qemu_savevm_state_iterate(s->to_dst_file, in_postcopy);
return MIG_ITERATE_RESUME;
}
static void migration_iteration_finish(MigrationState *s)
{
Error *local_err = NULL;
bql_lock();
/*
* If we enabled cpu throttling for auto-converge, turn it off.
* Stopping CPU throttle should be serialized by BQL to avoid
* racing for the throttle_dirty_sync_timer.
*/
if (migrate_auto_converge()) {
cpu_throttle_stop();
}
switch (s->state) {
case MIGRATION_STATUS_COMPLETED:
runstate_set(RUN_STATE_POSTMIGRATE);
break;
case MIGRATION_STATUS_COLO:
assert(migrate_colo());
migrate_start_colo_process(s);
s->vm_old_state = RUN_STATE_RUNNING;
/* Fallthrough */
case MIGRATION_STATUS_FAILING:
case MIGRATION_STATUS_CANCELLED:
case MIGRATION_STATUS_CANCELLING:
if (!migration_block_activate(&local_err)) {
/*
* Re-activate the block drives if they're inactivated.
*
* If it fails (e.g. in case of a split brain, where dest QEMU
* might have taken some of the drive locks and running!), do
* not start VM, instead wait for mgmt to decide the next step.
*
* If dest already started, it means dest QEMU should contain
* all the data it needs and it properly owns all the drive
* locks. Then even if src QEMU got a FAILED in migration, it
* normally should mean we should treat the migration as
* COMPLETED.
*
* NOTE: it's not safe anymore to start VM on src now even if
* dest would release the drive locks. It's because as long as
* dest started running then only dest QEMU's RAM is consistent
* with the shared storage.
*/
error_free(local_err);
break;
}
/*
* Notify FAILED before starting VM, so that devices can invoke
* necessary fallbacks before vCPUs run again.
*/
migration_call_notifiers(MIG_EVENT_FAILED, NULL);
if (runstate_is_live(s->vm_old_state)) {
if (!runstate_check(RUN_STATE_SHUTDOWN)) {
vm_start();
}
} else {
if (runstate_check(RUN_STATE_FINISH_MIGRATE)) {
runstate_set(s->vm_old_state);
}
}
break;
default:
/* Should not reach here, but if so, forgive the VM. */
error_report("%s: Unknown ending state %d", __func__, s->state);
break;
}
migration_bh_schedule(migration_cleanup_bh, s);
bql_unlock();
}
static void bg_migration_iteration_finish(MigrationState *s)
{
/*
* Stop tracking RAM writes - un-protect memory, un-register UFFD
* memory ranges, flush kernel wait queues and wake up threads
* waiting for write fault to be resolved.
*/
ram_write_tracking_stop();
bql_lock();
switch (s->state) {
case MIGRATION_STATUS_COMPLETED:
case MIGRATION_STATUS_ACTIVE:
case MIGRATION_STATUS_FAILING:
case MIGRATION_STATUS_CANCELLED:
case MIGRATION_STATUS_CANCELLING:
break;
default:
/* Should not reach here, but if so, forgive the VM. */
error_report("%s: Unknown ending state %d", __func__, s->state);
break;
}
migration_bh_schedule(migration_cleanup_bh, s);
bql_unlock();
}
/*
* Return true if continue to the next iteration directly, false
* otherwise.
*/
static MigIterateState bg_migration_iteration_run(MigrationState *s)
{
int res;
res = qemu_savevm_state_iterate(s->to_dst_file, false);
if (res > 0) {
bg_migration_completion(s);
return MIG_ITERATE_BREAK;
}
return MIG_ITERATE_RESUME;
}
void migration_make_urgent_request(void)
{
qemu_sem_post(&migrate_get_current()->rate_limit_sem);
}
void migration_consume_urgent_request(void)
{
qemu_sem_wait(&migrate_get_current()->rate_limit_sem);
}
/* Returns true if the rate limiting was broken by an urgent request */
bool migration_rate_limit(void)
{
int64_t now = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
MigrationState *s = migrate_get_current();
bool urgent = false;
migration_update_counters(s, now);
if (migration_rate_exceeded(s->to_dst_file)) {
if (qemu_file_get_error(s->to_dst_file)) {
return false;
}
/*
* Wait for a delay to do rate limiting OR
* something urgent to post the semaphore.
*/
int ms = s->iteration_start_time + BUFFER_DELAY - now;
trace_migration_rate_limit_pre(ms);
if (qemu_sem_timedwait(&s->rate_limit_sem, ms) == 0) {
/*
* We were woken by one or more urgent things but
* the timedwait will have consumed one of them.
* The service routine for the urgent wake will dec
* the semaphore itself for each item it consumes,
* so add this one we just eat back.
*/
qemu_sem_post(&s->rate_limit_sem);
urgent = true;
}
trace_migration_rate_limit_post(urgent);
}
return urgent;
}
/*
* if failover devices are present, wait they are completely
* unplugged
*/
static void qemu_savevm_wait_unplug(MigrationState *s, int old_state,
int new_state)
{
if (qemu_savevm_state_guest_unplug_pending()) {
migrate_set_state(&s->state, old_state, MIGRATION_STATUS_WAIT_UNPLUG);
while (s->state == MIGRATION_STATUS_WAIT_UNPLUG &&
qemu_savevm_state_guest_unplug_pending()) {
qemu_sem_timedwait(&s->wait_unplug_sem, 250);
}
if (s->state != MIGRATION_STATUS_WAIT_UNPLUG) {
int timeout = 120; /* 30 seconds */
/*
* migration has been canceled
* but as we have started an unplug we must wait the end
* to be able to plug back the card
*/
while (timeout-- && qemu_savevm_state_guest_unplug_pending()) {
qemu_sem_timedwait(&s->wait_unplug_sem, 250);
}
if (qemu_savevm_state_guest_unplug_pending() &&
!qtest_enabled()) {
warn_report("migration: partially unplugged device on "
"failure");
}
}
migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG, new_state);
} else {
migrate_set_state(&s->state, old_state, new_state);
}
}
/*
* Master migration thread on the source VM.
* It drives the migration and pumps the data down the outgoing channel.
*/
static void *migration_thread(void *opaque)
{
MigrationState *s = opaque;
int64_t setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
MigThrError thr_error;
bool urgent = false;
Error *local_err = NULL;
int ret;
rcu_register_thread();
update_iteration_initial_status(s);
if (!multifd_send_setup()) {
goto out;
}
bql_lock();
qemu_savevm_state_header(s->to_dst_file);
bql_unlock();
/*
* If we opened the return path, we need to make sure dst has it
* opened as well.
*/
if (s->rp_state.rp_thread_created) {
/* Now tell the dest that it should open its end so it can reply */
qemu_savevm_send_open_return_path(s->to_dst_file);
/* And do a ping that will make stuff easier to debug */
qemu_savevm_send_ping(s->to_dst_file, 1);
}
if (migrate_postcopy()) {
/*
* Tell the destination that we *might* want to do postcopy later;
* if the other end can't do postcopy it should fail now, nice and
* early.
*/
qemu_savevm_send_postcopy_advise(s->to_dst_file);
}
if (migrate_auto_converge()) {
/* Start RAMBlock dirty bitmap sync timer */
cpu_throttle_dirty_sync_timer(true);
}
bql_lock();
ret = qemu_savevm_state_do_setup(s->to_dst_file, &local_err);
bql_unlock();
qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
MIGRATION_STATUS_ACTIVE);
/*
* Handle SETUP failures after waiting for virtio-net-failover
* devices to unplug. This to preserve migration state transitions.
*/
if (ret) {
migrate_error_propagate(s, local_err);
migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
MIGRATION_STATUS_FAILING);
goto out;
}
s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start;
trace_migration_thread_setup_complete();
while (migration_is_active()) {
if (urgent || !migration_rate_exceeded(s->to_dst_file)) {
MigIterateState iter_state = migration_iteration_run(s);
if (iter_state == MIG_ITERATE_SKIP) {
continue;
} else if (iter_state == MIG_ITERATE_BREAK) {
break;
}
}
/*
* Try to detect any kind of failures, and see whether we
* should stop the migration now.
*/
thr_error = migration_detect_error(s);
if (thr_error == MIG_THR_ERR_FATAL) {
/* Stop migration */
break;
} else if (thr_error == MIG_THR_ERR_RECOVERED) {
/*
* Just recovered from a e.g. network failure, reset all
* the local variables. This is important to avoid
* breaking transferred_bytes and bandwidth calculation
*/
update_iteration_initial_status(s);
}
urgent = migration_rate_limit();
}
out:
trace_migration_thread_after_loop();
migration_iteration_finish(s);
object_unref(OBJECT(s));
rcu_unregister_thread();
return NULL;
}
static void bg_migration_vm_start_bh(void *opaque)
{
MigrationState *s = opaque;
vm_resume(s->vm_old_state);
migration_downtime_end(s);
}
/**
* Background snapshot thread, based on live migration code.
* This is an alternative implementation of live migration mechanism
* introduced specifically to support background snapshots.
*
* It takes advantage of userfault_fd write protection mechanism introduced
* in v5.7 kernel. Compared to existing dirty page logging migration much
* lesser stream traffic is produced resulting in smaller snapshot images,
* simply cause of no page duplicates can get into the stream.
*
* Another key point is that generated vmstate stream reflects machine state
* 'frozen' at the beginning of snapshot creation compared to dirty page logging
* mechanism, which effectively results in that saved snapshot is the state of VM
* at the end of the process.
*/
static void *bg_migration_thread(void *opaque)
{
MigrationState *s = opaque;
int64_t setup_start;
MigThrError thr_error;
QEMUFile *fb;
Error *local_err = NULL;
int ret;
rcu_register_thread();
migration_rate_set(RATE_LIMIT_DISABLED);
setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
/*
* We want to save vmstate for the moment when migration has been
* initiated but also we want to save RAM content while VM is running.
* The RAM content should appear first in the vmstate. So, we first
* stash the non-RAM part of the vmstate to the temporary buffer,
* then write RAM part of the vmstate to the migration stream
* with vCPUs running and, finally, write stashed non-RAM part of
* the vmstate from the buffer to the migration stream.
*/
s->bioc = qio_channel_buffer_new(512 * 1024);
qio_channel_set_name(QIO_CHANNEL(s->bioc), "vmstate-buffer");
fb = qemu_file_new_output(QIO_CHANNEL(s->bioc));
object_unref(OBJECT(s->bioc));
update_iteration_initial_status(s);
/*
* Prepare for tracking memory writes with UFFD-WP - populate
* RAM pages before protecting.
*/
#ifdef __linux__
ram_write_tracking_prepare();
#endif
bql_lock();
qemu_savevm_state_header(s->to_dst_file);
ret = qemu_savevm_state_do_setup(s->to_dst_file, &local_err);
bql_unlock();
qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
MIGRATION_STATUS_ACTIVE);
/*
* Handle SETUP failures after waiting for virtio-net-failover
* devices to unplug. This to preserve migration state transitions.
*/
if (ret) {
goto fail;
}
s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start;
trace_migration_thread_setup_complete();
bql_lock();
if (migration_stop_vm(s, RUN_STATE_PAUSED)) {
error_setg(&local_err, "Failed to stop the VM");
goto fail_with_bql;
}
if (!qemu_savevm_state_non_iterable(fb, &local_err)) {
error_prepend(&local_err, "Failed to save non-iterable devices ");
goto fail_with_bql;
}
qemu_savevm_state_end_precopy(s, fb);
/*
* Since we are going to get non-iterable state data directly
* from s->bioc->data, explicit flush is needed here.
*/
qemu_fflush(fb);
/* Now initialize UFFD context and start tracking RAM writes */
if (ram_write_tracking_start()) {
error_setg(&local_err, "Failed to start write tracking");
goto fail_with_bql;
}
/*
* Start VM from BH handler to avoid write-fault lock here.
* UFFD-WP protection for the whole RAM is already enabled so
* calling VM state change notifiers from vm_start() would initiate
* writes to virtio VQs memory which is in write-protected region.
*/
migration_bh_schedule(bg_migration_vm_start_bh, s);
bql_unlock();
while (migration_is_active()) {
MigIterateState iter_state = bg_migration_iteration_run(s);
if (iter_state == MIG_ITERATE_BREAK) {
break;
}
/*
* Try to detect any kind of failures, and see whether we
* should stop the migration now.
*/
thr_error = migration_detect_error(s);
if (thr_error == MIG_THR_ERR_FATAL) {
/* Stop migration */
break;
}
migration_update_counters(s, qemu_clock_get_ms(QEMU_CLOCK_REALTIME));
}
trace_migration_thread_after_loop();
goto done;
fail_with_bql:
bql_unlock();
fail:
/* local_err is guaranteed to be set when reaching here */
migrate_error_propagate(s, local_err);
migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
MIGRATION_STATUS_FAILING);
done:
bg_migration_iteration_finish(s);
qemu_fclose(fb);
object_unref(OBJECT(s));
rcu_unregister_thread();
return NULL;
}
void migration_start_outgoing(MigrationState *s)
{
Error *local_err = NULL;
uint64_t rate_limit;
bool resume = (s->state == MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP);
int ret;
if (resume) {
/* This is a resumed migration */
rate_limit = migrate_max_postcopy_bandwidth();
} else {
/* This is a fresh new migration */
rate_limit = migrate_max_bandwidth();
/* Notify before starting migration thread */
if (migration_call_notifiers(MIG_EVENT_SETUP, &local_err)) {
goto fail;
}
}
migration_rate_set(rate_limit);
if (!qemu_file_set_blocking(s->to_dst_file, true, &local_err)) {
goto fail;
}
/*
* Open the return path. For postcopy, it is used exclusively. For
* precopy, only if user specified "return-path" capability would
* QEMU uses the return path.
*/
if (migrate_postcopy_ram() || migrate_return_path()) {
open_return_path_on_source(s);
}
/*
* This needs to be done before resuming a postcopy. Note: for newer
* QEMUs we will delay the channel creation until postcopy_start(), to
* avoid disorder of channel creations.
*/
if (migrate_postcopy_preempt() && s->preempt_pre_7_2) {
postcopy_preempt_setup(s);
}
if (resume) {
/* Wakeup the main migration thread to do the recovery */
migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP,
MIGRATION_STATUS_POSTCOPY_RECOVER);
qemu_sem_post(&s->postcopy_pause_sem);
return;
}
if (migrate_mode_is_cpr()) {
ret = migration_stop_vm(s, RUN_STATE_FINISH_MIGRATE);
if (ret < 0) {
error_setg(&local_err, "migration_stop_vm failed, error %d", -ret);
goto fail;
}
}
/*
* Take a refcount to make sure the migration object won't get freed by
* the main thread already in migration_shutdown().
*
* The refcount will be released at the end of the thread function.
*/
object_ref(OBJECT(s));
if (migrate_background_snapshot()) {
qemu_thread_create(&s->thread, MIGRATION_THREAD_SNAPSHOT,
bg_migration_thread, s, QEMU_THREAD_JOINABLE);
} else {
qemu_thread_create(&s->thread, MIGRATION_THREAD_SRC_MAIN,
migration_thread, s, QEMU_THREAD_JOINABLE);
}
s->migration_thread_running = true;
return;
fail:
migration_connect_error_propagate(s, local_err);
if (s->error) {
error_report_err(error_copy(s->error));
}
}
static void migration_class_init(ObjectClass *klass, const void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
dc->user_creatable = false;
device_class_set_props_n(dc, migration_properties,
migration_properties_count);
}
static void migration_instance_finalize(Object *obj)
{
MigrationState *ms = MIGRATION(obj);
migrate_params_free(&ms->parameters, NULL);
qemu_mutex_destroy(&ms->error_mutex);
qemu_mutex_destroy(&ms->qemu_file_lock);
qemu_sem_destroy(&ms->wait_unplug_sem);
qemu_sem_destroy(&ms->rate_limit_sem);
qemu_event_destroy(&ms->pause_event);
qemu_sem_destroy(&ms->postcopy_pause_sem);
qemu_sem_destroy(&ms->rp_state.rp_sem);
qemu_sem_destroy(&ms->rp_state.rp_pong_acks);
qemu_sem_destroy(&ms->postcopy_qemufile_src_sem);
error_free(ms->error);
}
static void migration_instance_init(Object *obj)
{
MigrationState *ms = MIGRATION(obj);
ms->state = MIGRATION_STATUS_NONE;
ms->mbps = -1;
ms->pages_per_second = -1;
qemu_event_init(&ms->pause_event, false);
qemu_mutex_init(&ms->error_mutex);
migrate_params_init(&ms->parameters);
qemu_sem_init(&ms->postcopy_pause_sem, 0);
qemu_sem_init(&ms->rp_state.rp_sem, 0);
qemu_sem_init(&ms->rp_state.rp_pong_acks, 0);
qemu_sem_init(&ms->rate_limit_sem, 0);
qemu_sem_init(&ms->wait_unplug_sem, 0);
qemu_sem_init(&ms->postcopy_qemufile_src_sem, 0);
qemu_mutex_init(&ms->qemu_file_lock);
}
/*
* Return true if check pass, false otherwise. Error will be put
* inside errp if provided.
*/
static bool migration_object_check(MigrationState *ms, Error **errp)
{
/* Assuming all off */
bool old_caps[MIGRATION_CAPABILITY__MAX] = { 0 };
if (!migrate_params_check(&ms->parameters, errp)) {
return false;
}
return migrate_caps_check(old_caps, ms->capabilities, errp);
}
static const TypeInfo migration_type = {
.name = TYPE_MIGRATION,
/*
* NOTE: TYPE_MIGRATION is not really a device, as the object is
* not created using qdev_new(), it is not attached to the qdev
* device tree, and it is never realized.
*
* TODO: Make this TYPE_OBJECT once QOM provides something like
* TYPE_DEVICE's "-global" properties.
*/
.parent = TYPE_DEVICE,
.class_init = migration_class_init,
.instance_size = sizeof(MigrationState),
.instance_init = migration_instance_init,
.instance_finalize = migration_instance_finalize,
};
static void register_migration_types(void)
{
type_register_static(&migration_type);
}
type_init(register_migration_types);