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qemu/migration/multifd.c
Fabiano Rosas 90e0eeb99b migration/multifd: Add a couple of asserts for p->iov 
Check that p->iov is indeed always allocated and freed by the
MultiFDMethods hooks.

Suggested-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2024-09-03 16:24:37 -03:00

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/*
* Multifd common code
*
* Copyright (c) 2019-2020 Red Hat Inc
*
* Authors:
* Juan Quintela <quintela@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qemu/cutils.h"
#include "qemu/rcu.h"
#include "exec/target_page.h"
#include "sysemu/sysemu.h"
#include "exec/ramblock.h"
#include "qemu/error-report.h"
#include "qapi/error.h"
#include "file.h"
#include "migration.h"
#include "migration-stats.h"
#include "socket.h"
#include "tls.h"
#include "qemu-file.h"
#include "trace.h"
#include "multifd.h"
#include "threadinfo.h"
#include "options.h"
#include "qemu/yank.h"
#include "io/channel-file.h"
#include "io/channel-socket.h"
#include "yank_functions.h"
/* Multiple fd's */
#define MULTIFD_MAGIC 0x11223344U
#define MULTIFD_VERSION 1
typedef struct {
uint32_t magic;
uint32_t version;
unsigned char uuid[16]; /* QemuUUID */
uint8_t id;
uint8_t unused1[7]; /* Reserved for future use */
uint64_t unused2[4]; /* Reserved for future use */
} __attribute__((packed)) MultiFDInit_t;
struct {
MultiFDSendParams *params;
/*
* Global number of generated multifd packets.
*
* Note that we used 'uintptr_t' because it'll naturally support atomic
* operations on both 32bit / 64 bits hosts. It means on 32bit systems
* multifd will overflow the packet_num easier, but that should be
* fine.
*
* Another option is to use QEMU's Stat64 then it'll be 64 bits on all
* hosts, however so far it does not support atomic fetch_add() yet.
* Make it easy for now.
*/
uintptr_t packet_num;
/*
* Synchronization point past which no more channels will be
* created.
*/
QemuSemaphore channels_created;
/* send channels ready */
QemuSemaphore channels_ready;
/*
* Have we already run terminate threads. There is a race when it
* happens that we got one error while we are exiting.
* We will use atomic operations. Only valid values are 0 and 1.
*/
int exiting;
/* multifd ops */
const MultiFDMethods *ops;
} *multifd_send_state;
struct {
MultiFDRecvParams *params;
MultiFDRecvData *data;
/* number of created threads */
int count;
/*
* This is always posted by the recv threads, the migration thread
* uses it to wait for recv threads to finish assigned tasks.
*/
QemuSemaphore sem_sync;
/* global number of generated multifd packets */
uint64_t packet_num;
int exiting;
/* multifd ops */
const MultiFDMethods *ops;
} *multifd_recv_state;
MultiFDSendData *multifd_send_data_alloc(void)
{
size_t max_payload_size, size_minus_payload;
/*
* MultiFDPages_t has a flexible array at the end, account for it
* when allocating MultiFDSendData. Use max() in case other types
* added to the union in the future are larger than
* (MultiFDPages_t + flex array).
*/
max_payload_size = MAX(multifd_ram_payload_size(), sizeof(MultiFDPayload));
/*
* Account for any holes the compiler might insert. We can't pack
* the structure because that misaligns the members and triggers
* Waddress-of-packed-member.
*/
size_minus_payload = sizeof(MultiFDSendData) - sizeof(MultiFDPayload);
return g_malloc0(size_minus_payload + max_payload_size);
}
static bool multifd_use_packets(void)
{
return !migrate_mapped_ram();
}
void multifd_send_channel_created(void)
{
qemu_sem_post(&multifd_send_state->channels_created);
}
static const MultiFDMethods *multifd_ops[MULTIFD_COMPRESSION__MAX] = {};
void multifd_register_ops(int method, const MultiFDMethods *ops)
{
assert(0 <= method && method < MULTIFD_COMPRESSION__MAX);
assert(!multifd_ops[method]);
multifd_ops[method] = ops;
}
static int multifd_send_initial_packet(MultiFDSendParams *p, Error **errp)
{
MultiFDInit_t msg = {};
size_t size = sizeof(msg);
int ret;
msg.magic = cpu_to_be32(MULTIFD_MAGIC);
msg.version = cpu_to_be32(MULTIFD_VERSION);
msg.id = p->id;
memcpy(msg.uuid, &qemu_uuid.data, sizeof(msg.uuid));
ret = qio_channel_write_all(p->c, (char *)&msg, size, errp);
if (ret != 0) {
return -1;
}
stat64_add(&mig_stats.multifd_bytes, size);
return 0;
}
static int multifd_recv_initial_packet(QIOChannel *c, Error **errp)
{
MultiFDInit_t msg;
int ret;
ret = qio_channel_read_all(c, (char *)&msg, sizeof(msg), errp);
if (ret != 0) {
return -1;
}
msg.magic = be32_to_cpu(msg.magic);
msg.version = be32_to_cpu(msg.version);
if (msg.magic != MULTIFD_MAGIC) {
error_setg(errp, "multifd: received packet magic %x "
"expected %x", msg.magic, MULTIFD_MAGIC);
return -1;
}
if (msg.version != MULTIFD_VERSION) {
error_setg(errp, "multifd: received packet version %u "
"expected %u", msg.version, MULTIFD_VERSION);
return -1;
}
if (memcmp(msg.uuid, &qemu_uuid, sizeof(qemu_uuid))) {
char *uuid = qemu_uuid_unparse_strdup(&qemu_uuid);
char *msg_uuid = qemu_uuid_unparse_strdup((const QemuUUID *)msg.uuid);
error_setg(errp, "multifd: received uuid '%s' and expected "
"uuid '%s' for channel %hhd", msg_uuid, uuid, msg.id);
g_free(uuid);
g_free(msg_uuid);
return -1;
}
if (msg.id > migrate_multifd_channels()) {
error_setg(errp, "multifd: received channel id %u is greater than "
"number of channels %u", msg.id, migrate_multifd_channels());
return -1;
}
return msg.id;
}
void multifd_send_fill_packet(MultiFDSendParams *p)
{
MultiFDPacket_t *packet = p->packet;
uint64_t packet_num;
bool sync_packet = p->flags & MULTIFD_FLAG_SYNC;
memset(packet, 0, p->packet_len);
packet->magic = cpu_to_be32(MULTIFD_MAGIC);
packet->version = cpu_to_be32(MULTIFD_VERSION);
packet->flags = cpu_to_be32(p->flags);
packet->next_packet_size = cpu_to_be32(p->next_packet_size);
packet_num = qatomic_fetch_inc(&multifd_send_state->packet_num);
packet->packet_num = cpu_to_be64(packet_num);
p->packets_sent++;
if (!sync_packet) {
multifd_ram_fill_packet(p);
}
trace_multifd_send_fill(p->id, packet_num,
p->flags, p->next_packet_size);
}
static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
{
const MultiFDPacket_t *packet = p->packet;
uint32_t magic = be32_to_cpu(packet->magic);
uint32_t version = be32_to_cpu(packet->version);
int ret = 0;
if (magic != MULTIFD_MAGIC) {
error_setg(errp, "multifd: received packet magic %x, expected %x",
magic, MULTIFD_MAGIC);
return -1;
}
if (version != MULTIFD_VERSION) {
error_setg(errp, "multifd: received packet version %u, expected %u",
version, MULTIFD_VERSION);
return -1;
}
p->flags = be32_to_cpu(packet->flags);
p->next_packet_size = be32_to_cpu(packet->next_packet_size);
p->packet_num = be64_to_cpu(packet->packet_num);
p->packets_recved++;
if (!(p->flags & MULTIFD_FLAG_SYNC)) {
ret = multifd_ram_unfill_packet(p, errp);
}
trace_multifd_recv_unfill(p->id, p->packet_num, p->flags,
p->next_packet_size);
return ret;
}
static bool multifd_send_should_exit(void)
{
return qatomic_read(&multifd_send_state->exiting);
}
static bool multifd_recv_should_exit(void)
{
return qatomic_read(&multifd_recv_state->exiting);
}
/*
* The migration thread can wait on either of the two semaphores. This
* function can be used to kick the main thread out of waiting on either of
* them. Should mostly only be called when something wrong happened with
* the current multifd send thread.
*/
static void multifd_send_kick_main(MultiFDSendParams *p)
{
qemu_sem_post(&p->sem_sync);
qemu_sem_post(&multifd_send_state->channels_ready);
}
/*
* multifd_send() works by exchanging the MultiFDSendData object
* provided by the caller with an unused MultiFDSendData object from
* the next channel that is found to be idle.
*
* The channel owns the data until it finishes transmitting and the
* caller owns the empty object until it fills it with data and calls
* this function again. No locking necessary.
*
* Switching is safe because both the migration thread and the channel
* thread have barriers in place to serialize access.
*
* Returns true if succeed, false otherwise.
*/
bool multifd_send(MultiFDSendData **send_data)
{
int i;
static int next_channel;
MultiFDSendParams *p = NULL; /* make happy gcc */
MultiFDSendData *tmp;
if (multifd_send_should_exit()) {
return false;
}
/* We wait here, until at least one channel is ready */
qemu_sem_wait(&multifd_send_state->channels_ready);
/*
* next_channel can remain from a previous migration that was
* using more channels, so ensure it doesn't overflow if the
* limit is lower now.
*/
next_channel %= migrate_multifd_channels();
for (i = next_channel;; i = (i + 1) % migrate_multifd_channels()) {
if (multifd_send_should_exit()) {
return false;
}
p = &multifd_send_state->params[i];
/*
* Lockless read to p->pending_job is safe, because only multifd
* sender thread can clear it.
*/
if (qatomic_read(&p->pending_job) == false) {
next_channel = (i + 1) % migrate_multifd_channels();
break;
}
}
/*
* Make sure we read p->pending_job before all the rest. Pairs with
* qatomic_store_release() in multifd_send_thread().
*/
smp_mb_acquire();
assert(multifd_payload_empty(p->data));
/*
* Swap the pointers. The channel gets the client data for
* transferring and the client gets back an unused data slot.
*/
tmp = *send_data;
*send_data = p->data;
p->data = tmp;
/*
* Making sure p->data is setup before marking pending_job=true. Pairs
* with the qatomic_load_acquire() in multifd_send_thread().
*/
qatomic_store_release(&p->pending_job, true);
qemu_sem_post(&p->sem);
return true;
}
/* Multifd send side hit an error; remember it and prepare to quit */
static void multifd_send_set_error(Error *err)
{
/*
* We don't want to exit each threads twice. Depending on where
* we get the error, or if there are two independent errors in two
* threads at the same time, we can end calling this function
* twice.
*/
if (qatomic_xchg(&multifd_send_state->exiting, 1)) {
return;
}
if (err) {
MigrationState *s = migrate_get_current();
migrate_set_error(s, err);
if (s->state == MIGRATION_STATUS_SETUP ||
s->state == MIGRATION_STATUS_PRE_SWITCHOVER ||
s->state == MIGRATION_STATUS_DEVICE ||
s->state == MIGRATION_STATUS_ACTIVE) {
migrate_set_state(&s->state, s->state,
MIGRATION_STATUS_FAILED);
}
}
}
static void multifd_send_terminate_threads(void)
{
int i;
trace_multifd_send_terminate_threads();
/*
* Tell everyone we're quitting. No xchg() needed here; we simply
* always set it.
*/
qatomic_set(&multifd_send_state->exiting, 1);
/*
* Firstly, kick all threads out; no matter whether they are just idle,
* or blocked in an IO system call.
*/
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
qemu_sem_post(&p->sem);
if (p->c) {
qio_channel_shutdown(p->c, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
}
}
/*
* Finally recycle all the threads.
*/
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
if (p->tls_thread_created) {
qemu_thread_join(&p->tls_thread);
}
if (p->thread_created) {
qemu_thread_join(&p->thread);
}
}
}
static bool multifd_send_cleanup_channel(MultiFDSendParams *p, Error **errp)
{
if (p->c) {
migration_ioc_unregister_yank(p->c);
/*
* The object_unref() cannot guarantee the fd will always be
* released because finalize() of the iochannel is only
* triggered on the last reference and it's not guaranteed
* that we always hold the last refcount when reaching here.
*
* Closing the fd explicitly has the benefit that if there is any
* registered I/O handler callbacks on such fd, that will get a
* POLLNVAL event and will further trigger the cleanup to finally
* release the IOC.
*
* FIXME: It should logically be guaranteed that all multifd
* channels have no I/O handler callback registered when reaching
* here, because migration thread will wait for all multifd channel
* establishments to complete during setup. Since
* migrate_fd_cleanup() will be scheduled in main thread too, all
* previous callbacks should guarantee to be completed when
* reaching here. See multifd_send_state.channels_created and its
* usage. In the future, we could replace this with an assert
* making sure we're the last reference, or simply drop it if above
* is more clear to be justified.
*/
qio_channel_close(p->c, &error_abort);
object_unref(OBJECT(p->c));
p->c = NULL;
}
qemu_sem_destroy(&p->sem);
qemu_sem_destroy(&p->sem_sync);
g_free(p->name);
p->name = NULL;
g_free(p->data);
p->data = NULL;
p->packet_len = 0;
g_free(p->packet);
p->packet = NULL;
multifd_send_state->ops->send_cleanup(p, errp);
assert(!p->iov);
return *errp == NULL;
}
static void multifd_send_cleanup_state(void)
{
file_cleanup_outgoing_migration();
socket_cleanup_outgoing_migration();
qemu_sem_destroy(&multifd_send_state->channels_created);
qemu_sem_destroy(&multifd_send_state->channels_ready);
g_free(multifd_send_state->params);
multifd_send_state->params = NULL;
g_free(multifd_send_state);
multifd_send_state = NULL;
}
void multifd_send_shutdown(void)
{
int i;
if (!migrate_multifd()) {
return;
}
multifd_send_terminate_threads();
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
Error *local_err = NULL;
if (!multifd_send_cleanup_channel(p, &local_err)) {
migrate_set_error(migrate_get_current(), local_err);
error_free(local_err);
}
}
multifd_send_cleanup_state();
}
static int multifd_zero_copy_flush(QIOChannel *c)
{
int ret;
Error *err = NULL;
ret = qio_channel_flush(c, &err);
if (ret < 0) {
error_report_err(err);
return -1;
}
if (ret == 1) {
stat64_add(&mig_stats.dirty_sync_missed_zero_copy, 1);
}
return ret;
}
int multifd_send_sync_main(void)
{
int i;
bool flush_zero_copy;
flush_zero_copy = migrate_zero_copy_send();
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
if (multifd_send_should_exit()) {
return -1;
}
trace_multifd_send_sync_main_signal(p->id);
/*
* We should be the only user so far, so not possible to be set by
* others concurrently.
*/
assert(qatomic_read(&p->pending_sync) == false);
qatomic_set(&p->pending_sync, true);
qemu_sem_post(&p->sem);
}
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
if (multifd_send_should_exit()) {
return -1;
}
qemu_sem_wait(&multifd_send_state->channels_ready);
trace_multifd_send_sync_main_wait(p->id);
qemu_sem_wait(&p->sem_sync);
if (flush_zero_copy && p->c && (multifd_zero_copy_flush(p->c) < 0)) {
return -1;
}
}
trace_multifd_send_sync_main(multifd_send_state->packet_num);
return 0;
}
static void *multifd_send_thread(void *opaque)
{
MultiFDSendParams *p = opaque;
MigrationThread *thread = NULL;
Error *local_err = NULL;
int ret = 0;
bool use_packets = multifd_use_packets();
thread = migration_threads_add(p->name, qemu_get_thread_id());
trace_multifd_send_thread_start(p->id);
rcu_register_thread();
if (use_packets) {
if (multifd_send_initial_packet(p, &local_err) < 0) {
ret = -1;
goto out;
}
}
while (true) {
qemu_sem_post(&multifd_send_state->channels_ready);
qemu_sem_wait(&p->sem);
if (multifd_send_should_exit()) {
break;
}
/*
* Read pending_job flag before p->data. Pairs with the
* qatomic_store_release() in multifd_send().
*/
if (qatomic_load_acquire(&p->pending_job)) {
p->iovs_num = 0;
assert(!multifd_payload_empty(p->data));
ret = multifd_send_state->ops->send_prepare(p, &local_err);
if (ret != 0) {
break;
}
if (migrate_mapped_ram()) {
ret = file_write_ramblock_iov(p->c, p->iov, p->iovs_num,
&p->data->u.ram, &local_err);
} else {
ret = qio_channel_writev_full_all(p->c, p->iov, p->iovs_num,
NULL, 0, p->write_flags,
&local_err);
}
if (ret != 0) {
break;
}
stat64_add(&mig_stats.multifd_bytes,
p->next_packet_size + p->packet_len);
p->next_packet_size = 0;
multifd_set_payload_type(p->data, MULTIFD_PAYLOAD_NONE);
/*
* Making sure p->data is published before saying "we're
* free". Pairs with the smp_mb_acquire() in
* multifd_send().
*/
qatomic_store_release(&p->pending_job, false);
} else {
/*
* If not a normal job, must be a sync request. Note that
* pending_sync is a standalone flag (unlike pending_job), so
* it doesn't require explicit memory barriers.
*/
assert(qatomic_read(&p->pending_sync));
if (use_packets) {
p->flags = MULTIFD_FLAG_SYNC;
multifd_send_fill_packet(p);
ret = qio_channel_write_all(p->c, (void *)p->packet,
p->packet_len, &local_err);
if (ret != 0) {
break;
}
/* p->next_packet_size will always be zero for a SYNC packet */
stat64_add(&mig_stats.multifd_bytes, p->packet_len);
p->flags = 0;
}
qatomic_set(&p->pending_sync, false);
qemu_sem_post(&p->sem_sync);
}
}
out:
if (ret) {
assert(local_err);
trace_multifd_send_error(p->id);
multifd_send_set_error(local_err);
multifd_send_kick_main(p);
error_free(local_err);
}
rcu_unregister_thread();
migration_threads_remove(thread);
trace_multifd_send_thread_end(p->id, p->packets_sent);
return NULL;
}
static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque);
typedef struct {
MultiFDSendParams *p;
QIOChannelTLS *tioc;
} MultiFDTLSThreadArgs;
static void *multifd_tls_handshake_thread(void *opaque)
{
MultiFDTLSThreadArgs *args = opaque;
qio_channel_tls_handshake(args->tioc,
multifd_new_send_channel_async,
args->p,
NULL,
NULL);
g_free(args);
return NULL;
}
static bool multifd_tls_channel_connect(MultiFDSendParams *p,
QIOChannel *ioc,
Error **errp)
{
MigrationState *s = migrate_get_current();
const char *hostname = s->hostname;
MultiFDTLSThreadArgs *args;
QIOChannelTLS *tioc;
tioc = migration_tls_client_create(ioc, hostname, errp);
if (!tioc) {
return false;
}
/*
* Ownership of the socket channel now transfers to the newly
* created TLS channel, which has already taken a reference.
*/
object_unref(OBJECT(ioc));
trace_multifd_tls_outgoing_handshake_start(ioc, tioc, hostname);
qio_channel_set_name(QIO_CHANNEL(tioc), "multifd-tls-outgoing");
args = g_new0(MultiFDTLSThreadArgs, 1);
args->tioc = tioc;
args->p = p;
p->tls_thread_created = true;
qemu_thread_create(&p->tls_thread, "mig/src/tls",
multifd_tls_handshake_thread, args,
QEMU_THREAD_JOINABLE);
return true;
}
void multifd_channel_connect(MultiFDSendParams *p, QIOChannel *ioc)
{
qio_channel_set_delay(ioc, false);
migration_ioc_register_yank(ioc);
/* Setup p->c only if the channel is completely setup */
p->c = ioc;
p->thread_created = true;
qemu_thread_create(&p->thread, p->name, multifd_send_thread, p,
QEMU_THREAD_JOINABLE);
}
/*
* When TLS is enabled this function is called once to establish the
* TLS connection and a second time after the TLS handshake to create
* the multifd channel. Without TLS it goes straight into the channel
* creation.
*/
static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque)
{
MultiFDSendParams *p = opaque;
QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task));
Error *local_err = NULL;
bool ret;
trace_multifd_new_send_channel_async(p->id);
if (qio_task_propagate_error(task, &local_err)) {
ret = false;
goto out;
}
trace_multifd_set_outgoing_channel(ioc, object_get_typename(OBJECT(ioc)),
migrate_get_current()->hostname);
if (migrate_channel_requires_tls_upgrade(ioc)) {
ret = multifd_tls_channel_connect(p, ioc, &local_err);
if (ret) {
return;
}
} else {
multifd_channel_connect(p, ioc);
ret = true;
}
out:
/*
* Here we're not interested whether creation succeeded, only that
* it happened at all.
*/
multifd_send_channel_created();
if (ret) {
return;
}
trace_multifd_new_send_channel_async_error(p->id, local_err);
multifd_send_set_error(local_err);
/*
* For error cases (TLS or non-TLS), IO channel is always freed here
* rather than when cleanup multifd: since p->c is not set, multifd
* cleanup code doesn't even know its existence.
*/
object_unref(OBJECT(ioc));
error_free(local_err);
}
static bool multifd_new_send_channel_create(gpointer opaque, Error **errp)
{
if (!multifd_use_packets()) {
return file_send_channel_create(opaque, errp);
}
socket_send_channel_create(multifd_new_send_channel_async, opaque);
return true;
}
bool multifd_send_setup(void)
{
MigrationState *s = migrate_get_current();
int thread_count, ret = 0;
uint32_t page_count = multifd_ram_page_count();
bool use_packets = multifd_use_packets();
uint8_t i;
if (!migrate_multifd()) {
return true;
}
thread_count = migrate_multifd_channels();
multifd_send_state = g_malloc0(sizeof(*multifd_send_state));
multifd_send_state->params = g_new0(MultiFDSendParams, thread_count);
qemu_sem_init(&multifd_send_state->channels_created, 0);
qemu_sem_init(&multifd_send_state->channels_ready, 0);
qatomic_set(&multifd_send_state->exiting, 0);
multifd_send_state->ops = multifd_ops[migrate_multifd_compression()];
for (i = 0; i < thread_count; i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
Error *local_err = NULL;
qemu_sem_init(&p->sem, 0);
qemu_sem_init(&p->sem_sync, 0);
p->id = i;
p->data = multifd_send_data_alloc();
if (use_packets) {
p->packet_len = sizeof(MultiFDPacket_t)
+ sizeof(uint64_t) * page_count;
p->packet = g_malloc0(p->packet_len);
}
p->name = g_strdup_printf("mig/src/send_%d", i);
p->write_flags = 0;
if (!multifd_new_send_channel_create(p, &local_err)) {
migrate_set_error(s, local_err);
ret = -1;
}
}
/*
* Wait until channel creation has started for all channels. The
* creation can still fail, but no more channels will be created
* past this point.
*/
for (i = 0; i < thread_count; i++) {
qemu_sem_wait(&multifd_send_state->channels_created);
}
if (ret) {
goto err;
}
for (i = 0; i < thread_count; i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
Error *local_err = NULL;
ret = multifd_send_state->ops->send_setup(p, &local_err);
if (ret) {
migrate_set_error(s, local_err);
goto err;
}
assert(p->iov);
}
return true;
err:
migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
MIGRATION_STATUS_FAILED);
return false;
}
bool multifd_recv(void)
{
int i;
static int next_recv_channel;
MultiFDRecvParams *p = NULL;
MultiFDRecvData *data = multifd_recv_state->data;
/*
* next_channel can remain from a previous migration that was
* using more channels, so ensure it doesn't overflow if the
* limit is lower now.
*/
next_recv_channel %= migrate_multifd_channels();
for (i = next_recv_channel;; i = (i + 1) % migrate_multifd_channels()) {
if (multifd_recv_should_exit()) {
return false;
}
p = &multifd_recv_state->params[i];
if (qatomic_read(&p->pending_job) == false) {
next_recv_channel = (i + 1) % migrate_multifd_channels();
break;
}
}
/*
* Order pending_job read before manipulating p->data below. Pairs
* with qatomic_store_release() at multifd_recv_thread().
*/
smp_mb_acquire();
assert(!p->data->size);
multifd_recv_state->data = p->data;
p->data = data;
/*
* Order p->data update before setting pending_job. Pairs with
* qatomic_load_acquire() at multifd_recv_thread().
*/
qatomic_store_release(&p->pending_job, true);
qemu_sem_post(&p->sem);
return true;
}
MultiFDRecvData *multifd_get_recv_data(void)
{
return multifd_recv_state->data;
}
static void multifd_recv_terminate_threads(Error *err)
{
int i;
trace_multifd_recv_terminate_threads(err != NULL);
if (qatomic_xchg(&multifd_recv_state->exiting, 1)) {
return;
}
if (err) {
MigrationState *s = migrate_get_current();
migrate_set_error(s, err);
if (s->state == MIGRATION_STATUS_SETUP ||
s->state == MIGRATION_STATUS_ACTIVE) {
migrate_set_state(&s->state, s->state,
MIGRATION_STATUS_FAILED);
}
}
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDRecvParams *p = &multifd_recv_state->params[i];
/*
* The migration thread and channels interact differently
* depending on the presence of packets.
*/
if (multifd_use_packets()) {
/*
* The channel receives as long as there are packets. When
* packets end (i.e. MULTIFD_FLAG_SYNC is reached), the
* channel waits for the migration thread to sync. If the
* sync never happens, do it here.
*/
qemu_sem_post(&p->sem_sync);
} else {
/*
* The channel waits for the migration thread to give it
* work. When the migration thread runs out of work, it
* releases the channel and waits for any pending work to
* finish. If we reach here (e.g. due to error) before the
* work runs out, release the channel.
*/
qemu_sem_post(&p->sem);
}
/*
* We could arrive here for two reasons:
* - normal quit, i.e. everything went fine, just finished
* - error quit: We close the channels so the channel threads
* finish the qio_channel_read_all_eof()
*/
if (p->c) {
qio_channel_shutdown(p->c, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
}
}
}
void multifd_recv_shutdown(void)
{
if (migrate_multifd()) {
multifd_recv_terminate_threads(NULL);
}
}
static void multifd_recv_cleanup_channel(MultiFDRecvParams *p)
{
migration_ioc_unregister_yank(p->c);
object_unref(OBJECT(p->c));
p->c = NULL;
qemu_mutex_destroy(&p->mutex);
qemu_sem_destroy(&p->sem_sync);
qemu_sem_destroy(&p->sem);
g_free(p->data);
p->data = NULL;
g_free(p->name);
p->name = NULL;
p->packet_len = 0;
g_free(p->packet);
p->packet = NULL;
g_free(p->normal);
p->normal = NULL;
g_free(p->zero);
p->zero = NULL;
multifd_recv_state->ops->recv_cleanup(p);
}
static void multifd_recv_cleanup_state(void)
{
qemu_sem_destroy(&multifd_recv_state->sem_sync);
g_free(multifd_recv_state->params);
multifd_recv_state->params = NULL;
g_free(multifd_recv_state->data);
multifd_recv_state->data = NULL;
g_free(multifd_recv_state);
multifd_recv_state = NULL;
}
void multifd_recv_cleanup(void)
{
int i;
if (!migrate_multifd()) {
return;
}
multifd_recv_terminate_threads(NULL);
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDRecvParams *p = &multifd_recv_state->params[i];
if (p->thread_created) {
qemu_thread_join(&p->thread);
}
}
for (i = 0; i < migrate_multifd_channels(); i++) {
multifd_recv_cleanup_channel(&multifd_recv_state->params[i]);
}
multifd_recv_cleanup_state();
}
void multifd_recv_sync_main(void)
{
int thread_count = migrate_multifd_channels();
bool file_based = !multifd_use_packets();
int i;
if (!migrate_multifd()) {
return;
}
/*
* File-based channels don't use packets and therefore need to
* wait for more work. Release them to start the sync.
*/
if (file_based) {
for (i = 0; i < thread_count; i++) {
MultiFDRecvParams *p = &multifd_recv_state->params[i];
trace_multifd_recv_sync_main_signal(p->id);
qemu_sem_post(&p->sem);
}
}
/*
* Initiate the synchronization by waiting for all channels.
*
* For socket-based migration this means each channel has received
* the SYNC packet on the stream.
*
* For file-based migration this means each channel is done with
* the work (pending_job=false).
*/
for (i = 0; i < thread_count; i++) {
trace_multifd_recv_sync_main_wait(i);
qemu_sem_wait(&multifd_recv_state->sem_sync);
}
if (file_based) {
/*
* For file-based loading is done in one iteration. We're
* done.
*/
return;
}
/*
* Sync done. Release the channels for the next iteration.
*/
for (i = 0; i < thread_count; i++) {
MultiFDRecvParams *p = &multifd_recv_state->params[i];
WITH_QEMU_LOCK_GUARD(&p->mutex) {
if (multifd_recv_state->packet_num < p->packet_num) {
multifd_recv_state->packet_num = p->packet_num;
}
}
trace_multifd_recv_sync_main_signal(p->id);
qemu_sem_post(&p->sem_sync);
}
trace_multifd_recv_sync_main(multifd_recv_state->packet_num);
}
static void *multifd_recv_thread(void *opaque)
{
MultiFDRecvParams *p = opaque;
Error *local_err = NULL;
bool use_packets = multifd_use_packets();
int ret;
trace_multifd_recv_thread_start(p->id);
rcu_register_thread();
while (true) {
uint32_t flags = 0;
bool has_data = false;
p->normal_num = 0;
if (use_packets) {
if (multifd_recv_should_exit()) {
break;
}
ret = qio_channel_read_all_eof(p->c, (void *)p->packet,
p->packet_len, &local_err);
if (ret == 0 || ret == -1) { /* 0: EOF -1: Error */
break;
}
qemu_mutex_lock(&p->mutex);
ret = multifd_recv_unfill_packet(p, &local_err);
if (ret) {
qemu_mutex_unlock(&p->mutex);
break;
}
flags = p->flags;
/* recv methods don't know how to handle the SYNC flag */
p->flags &= ~MULTIFD_FLAG_SYNC;
if (!(flags & MULTIFD_FLAG_SYNC)) {
has_data = p->normal_num || p->zero_num;
}
qemu_mutex_unlock(&p->mutex);
} else {
/*
* No packets, so we need to wait for the vmstate code to
* give us work.
*/
qemu_sem_wait(&p->sem);
if (multifd_recv_should_exit()) {
break;
}
/* pairs with qatomic_store_release() at multifd_recv() */
if (!qatomic_load_acquire(&p->pending_job)) {
/*
* Migration thread did not send work, this is
* equivalent to pending_sync on the sending
* side. Post sem_sync to notify we reached this
* point.
*/
qemu_sem_post(&multifd_recv_state->sem_sync);
continue;
}
has_data = !!p->data->size;
}
if (has_data) {
ret = multifd_recv_state->ops->recv(p, &local_err);
if (ret != 0) {
break;
}
}
if (use_packets) {
if (flags & MULTIFD_FLAG_SYNC) {
qemu_sem_post(&multifd_recv_state->sem_sync);
qemu_sem_wait(&p->sem_sync);
}
} else {
p->data->size = 0;
/*
* Order data->size update before clearing
* pending_job. Pairs with smp_mb_acquire() at
* multifd_recv().
*/
qatomic_store_release(&p->pending_job, false);
}
}
if (local_err) {
multifd_recv_terminate_threads(local_err);
error_free(local_err);
}
rcu_unregister_thread();
trace_multifd_recv_thread_end(p->id, p->packets_recved);
return NULL;
}
int multifd_recv_setup(Error **errp)
{
int thread_count;
uint32_t page_count = multifd_ram_page_count();
bool use_packets = multifd_use_packets();
uint8_t i;
/*
* Return successfully if multiFD recv state is already initialised
* or multiFD is not enabled.
*/
if (multifd_recv_state || !migrate_multifd()) {
return 0;
}
thread_count = migrate_multifd_channels();
multifd_recv_state = g_malloc0(sizeof(*multifd_recv_state));
multifd_recv_state->params = g_new0(MultiFDRecvParams, thread_count);
multifd_recv_state->data = g_new0(MultiFDRecvData, 1);
multifd_recv_state->data->size = 0;
qatomic_set(&multifd_recv_state->count, 0);
qatomic_set(&multifd_recv_state->exiting, 0);
qemu_sem_init(&multifd_recv_state->sem_sync, 0);
multifd_recv_state->ops = multifd_ops[migrate_multifd_compression()];
for (i = 0; i < thread_count; i++) {
MultiFDRecvParams *p = &multifd_recv_state->params[i];
qemu_mutex_init(&p->mutex);
qemu_sem_init(&p->sem_sync, 0);
qemu_sem_init(&p->sem, 0);
p->pending_job = false;
p->id = i;
p->data = g_new0(MultiFDRecvData, 1);
p->data->size = 0;
if (use_packets) {
p->packet_len = sizeof(MultiFDPacket_t)
+ sizeof(uint64_t) * page_count;
p->packet = g_malloc0(p->packet_len);
}
p->name = g_strdup_printf("mig/dst/recv_%d", i);
p->normal = g_new0(ram_addr_t, page_count);
p->zero = g_new0(ram_addr_t, page_count);
}
for (i = 0; i < thread_count; i++) {
MultiFDRecvParams *p = &multifd_recv_state->params[i];
int ret;
ret = multifd_recv_state->ops->recv_setup(p, errp);
if (ret) {
return ret;
}
}
return 0;
}
bool multifd_recv_all_channels_created(void)
{
int thread_count = migrate_multifd_channels();
if (!migrate_multifd()) {
return true;
}
if (!multifd_recv_state) {
/* Called before any connections created */
return false;
}
return thread_count == qatomic_read(&multifd_recv_state->count);
}
/*
* Try to receive all multifd channels to get ready for the migration.
* Sets @errp when failing to receive the current channel.
*/
void multifd_recv_new_channel(QIOChannel *ioc, Error **errp)
{
MultiFDRecvParams *p;
Error *local_err = NULL;
bool use_packets = multifd_use_packets();
int id;
if (use_packets) {
id = multifd_recv_initial_packet(ioc, &local_err);
if (id < 0) {
multifd_recv_terminate_threads(local_err);
error_propagate_prepend(errp, local_err,
"failed to receive packet"
" via multifd channel %d: ",
qatomic_read(&multifd_recv_state->count));
return;
}
trace_multifd_recv_new_channel(id);
} else {
id = qatomic_read(&multifd_recv_state->count);
}
p = &multifd_recv_state->params[id];
if (p->c != NULL) {
error_setg(&local_err, "multifd: received id '%d' already setup'",
id);
multifd_recv_terminate_threads(local_err);
error_propagate(errp, local_err);
return;
}
p->c = ioc;
object_ref(OBJECT(ioc));
p->thread_created = true;
qemu_thread_create(&p->thread, p->name, multifd_recv_thread, p,
QEMU_THREAD_JOINABLE);
qatomic_inc(&multifd_recv_state->count);
}
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