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qemu/migration/multifd.c
Peter Xu 488c84acb4 migration/multifd: Optimize sender side to be lockless 
When reviewing my attempt to refactor send_prepare(), Fabiano suggested we
try out with dropping the mutex in multifd code [1].

I thought about that before but I never tried to change the code.  Now
maybe it's time to give it a stab.  This only optimizes the sender side.

The trick here is multifd has a clear provider/consumer model, that the
migration main thread publishes requests (either pending_job/pending_sync),
while the multifd sender threads are consumers.  Here we don't have a lot
of complicated data sharing, and the jobs can logically be submitted
lockless.

Arm the code with atomic weapons.  Two things worth mentioning:

  - For multifd_send_pages(): we can use qatomic_load_acquire() when trying
  to find a free channel, but that's expensive if we attach one ACQUIRE per
  channel.  Instead, keep the qatomic_read() on reading the pending_job
  flag as we do already, meanwhile use one smp_mb_acquire() after the loop
  to guarantee the memory ordering.

  - For pending_sync: it doesn't have any extra data required since now
  p->flags are never touched, it should be safe to not use memory barrier.
  That's different from pending_job.

Provide rich comments for all the lockless operations to state how they are
paired.  With that, we can remove the mutex.

[1] https://lore.kernel.org/r/87o7d1jlu5.fsf@suse.de

Suggested-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240202102857.110210-24-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2024-02-06 11:05:49 +08:00

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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/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 "ram.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-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;
/* array of pages to sent */
MultiFDPages_t *pages;
/*
* 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;
/* 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 */
MultiFDMethods *ops;
} *multifd_send_state;
/* Multifd without compression */
/**
* nocomp_send_setup: setup send side
*
* @p: Params for the channel that we are using
* @errp: pointer to an error
*/
static int nocomp_send_setup(MultiFDSendParams *p, Error **errp)
{
if (migrate_zero_copy_send()) {
p->write_flags |= QIO_CHANNEL_WRITE_FLAG_ZERO_COPY;
}
return 0;
}
/**
* nocomp_send_cleanup: cleanup send side
*
* For no compression this function does nothing.
*
* @p: Params for the channel that we are using
* @errp: pointer to an error
*/
static void nocomp_send_cleanup(MultiFDSendParams *p, Error **errp)
{
return;
}
/**
* nocomp_send_prepare: prepare date to be able to send
*
* For no compression we just have to calculate the size of the
* packet.
*
* Returns 0 for success or -1 for error
*
* @p: Params for the channel that we are using
* @errp: pointer to an error
*/
static int nocomp_send_prepare(MultiFDSendParams *p, Error **errp)
{
bool use_zero_copy_send = migrate_zero_copy_send();
MultiFDPages_t *pages = p->pages;
int ret;
if (!use_zero_copy_send) {
/*
* Only !zerocopy needs the header in IOV; zerocopy will
* send it separately.
*/
multifd_send_prepare_header(p);
}
for (int i = 0; i < pages->num; i++) {
p->iov[p->iovs_num].iov_base = pages->block->host + pages->offset[i];
p->iov[p->iovs_num].iov_len = p->page_size;
p->iovs_num++;
}
p->next_packet_size = pages->num * p->page_size;
p->flags |= MULTIFD_FLAG_NOCOMP;
multifd_send_fill_packet(p);
if (use_zero_copy_send) {
/* Send header first, without zerocopy */
ret = qio_channel_write_all(p->c, (void *)p->packet,
p->packet_len, errp);
if (ret != 0) {
return -1;
}
}
return 0;
}
/**
* nocomp_recv_setup: setup receive side
*
* For no compression this function does nothing.
*
* Returns 0 for success or -1 for error
*
* @p: Params for the channel that we are using
* @errp: pointer to an error
*/
static int nocomp_recv_setup(MultiFDRecvParams *p, Error **errp)
{
return 0;
}
/**
* nocomp_recv_cleanup: setup receive side
*
* For no compression this function does nothing.
*
* @p: Params for the channel that we are using
*/
static void nocomp_recv_cleanup(MultiFDRecvParams *p)
{
}
/**
* nocomp_recv_pages: read the data from the channel into actual pages
*
* For no compression we just need to read things into the correct place.
*
* Returns 0 for success or -1 for error
*
* @p: Params for the channel that we are using
* @errp: pointer to an error
*/
static int nocomp_recv_pages(MultiFDRecvParams *p, Error **errp)
{
uint32_t flags = p->flags & MULTIFD_FLAG_COMPRESSION_MASK;
if (flags != MULTIFD_FLAG_NOCOMP) {
error_setg(errp, "multifd %u: flags received %x flags expected %x",
p->id, flags, MULTIFD_FLAG_NOCOMP);
return -1;
}
for (int i = 0; i < p->normal_num; i++) {
p->iov[i].iov_base = p->host + p->normal[i];
p->iov[i].iov_len = p->page_size;
}
return qio_channel_readv_all(p->c, p->iov, p->normal_num, errp);
}
static MultiFDMethods multifd_nocomp_ops = {
.send_setup = nocomp_send_setup,
.send_cleanup = nocomp_send_cleanup,
.send_prepare = nocomp_send_prepare,
.recv_setup = nocomp_recv_setup,
.recv_cleanup = nocomp_recv_cleanup,
.recv_pages = nocomp_recv_pages
};
static MultiFDMethods *multifd_ops[MULTIFD_COMPRESSION__MAX] = {
[MULTIFD_COMPRESSION_NONE] = &multifd_nocomp_ops,
};
void multifd_register_ops(int method, MultiFDMethods *ops)
{
assert(0 < method && method < MULTIFD_COMPRESSION__MAX);
multifd_ops[method] = ops;
}
/* Reset a MultiFDPages_t* object for the next use */
static void multifd_pages_reset(MultiFDPages_t *pages)
{
/*
* We don't need to touch offset[] array, because it will be
* overwritten later when reused.
*/
pages->num = 0;
pages->block = NULL;
}
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;
}
static MultiFDPages_t *multifd_pages_init(uint32_t n)
{
MultiFDPages_t *pages = g_new0(MultiFDPages_t, 1);
pages->allocated = n;
pages->offset = g_new0(ram_addr_t, n);
return pages;
}
static void multifd_pages_clear(MultiFDPages_t *pages)
{
multifd_pages_reset(pages);
pages->allocated = 0;
g_free(pages->offset);
pages->offset = NULL;
g_free(pages);
}
void multifd_send_fill_packet(MultiFDSendParams *p)
{
MultiFDPacket_t *packet = p->packet;
MultiFDPages_t *pages = p->pages;
uint64_t packet_num;
int i;
packet->flags = cpu_to_be32(p->flags);
packet->pages_alloc = cpu_to_be32(p->pages->allocated);
packet->normal_pages = cpu_to_be32(pages->num);
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);
if (pages->block) {
strncpy(packet->ramblock, pages->block->idstr, 256);
}
for (i = 0; i < pages->num; i++) {
/* there are architectures where ram_addr_t is 32 bit */
uint64_t temp = pages->offset[i];
packet->offset[i] = cpu_to_be64(temp);
}
p->packets_sent++;
p->total_normal_pages += pages->num;
trace_multifd_send(p->id, packet_num, pages->num, p->flags,
p->next_packet_size);
}
static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
{
MultiFDPacket_t *packet = p->packet;
int i;
packet->magic = be32_to_cpu(packet->magic);
if (packet->magic != MULTIFD_MAGIC) {
error_setg(errp, "multifd: received packet "
"magic %x and expected magic %x",
packet->magic, MULTIFD_MAGIC);
return -1;
}
packet->version = be32_to_cpu(packet->version);
if (packet->version != MULTIFD_VERSION) {
error_setg(errp, "multifd: received packet "
"version %u and expected version %u",
packet->version, MULTIFD_VERSION);
return -1;
}
p->flags = be32_to_cpu(packet->flags);
packet->pages_alloc = be32_to_cpu(packet->pages_alloc);
/*
* If we received a packet that is 100 times bigger than expected
* just stop migration. It is a magic number.
*/
if (packet->pages_alloc > p->page_count) {
error_setg(errp, "multifd: received packet "
"with size %u and expected a size of %u",
packet->pages_alloc, p->page_count) ;
return -1;
}
p->normal_num = be32_to_cpu(packet->normal_pages);
if (p->normal_num > packet->pages_alloc) {
error_setg(errp, "multifd: received packet "
"with %u pages and expected maximum pages are %u",
p->normal_num, packet->pages_alloc) ;
return -1;
}
p->next_packet_size = be32_to_cpu(packet->next_packet_size);
p->packet_num = be64_to_cpu(packet->packet_num);
p->packets_recved++;
p->total_normal_pages += p->normal_num;
trace_multifd_recv(p->id, p->packet_num, p->normal_num, p->flags,
p->next_packet_size);
if (p->normal_num == 0) {
return 0;
}
/* make sure that ramblock is 0 terminated */
packet->ramblock[255] = 0;
p->block = qemu_ram_block_by_name(packet->ramblock);
if (!p->block) {
error_setg(errp, "multifd: unknown ram block %s",
packet->ramblock);
return -1;
}
p->host = p->block->host;
for (i = 0; i < p->normal_num; i++) {
uint64_t offset = be64_to_cpu(packet->offset[i]);
if (offset > (p->block->used_length - p->page_size)) {
error_setg(errp, "multifd: offset too long %" PRIu64
" (max " RAM_ADDR_FMT ")",
offset, p->block->used_length);
return -1;
}
p->normal[i] = offset;
}
return 0;
}
static bool multifd_send_should_exit(void)
{
return qatomic_read(&multifd_send_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);
}
/*
* How we use multifd_send_state->pages and channel->pages?
*
* We create a pages for each channel, and a main one. Each time that
* we need to send a batch of pages we interchange the ones between
* multifd_send_state and the channel that is sending it. There are
* two reasons for that:
* - to not have to do so many mallocs during migration
* - to make easier to know what to free at the end of migration
*
* This way we always know who is the owner of each "pages" struct,
* and we don't need any locking. It belongs to the migration thread
* or to the channel thread. Switching is safe because the migration
* thread is using the channel mutex when changing it, and the channel
* have to had finish with its own, otherwise pending_job can't be
* false.
*
* Returns true if succeed, false otherwise.
*/
static bool multifd_send_pages(void)
{
int i;
static int next_channel;
MultiFDSendParams *p = NULL; /* make happy gcc */
MultiFDPages_t *pages = multifd_send_state->pages;
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(!p->pages->num);
multifd_send_state->pages = p->pages;
p->pages = pages;
/*
* Making sure p->pages 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;
}
static inline bool multifd_queue_empty(MultiFDPages_t *pages)
{
return pages->num == 0;
}
static inline bool multifd_queue_full(MultiFDPages_t *pages)
{
return pages->num == pages->allocated;
}
static inline void multifd_enqueue(MultiFDPages_t *pages, ram_addr_t offset)
{
pages->offset[pages->num++] = offset;
}
/* Returns true if enqueue successful, false otherwise */
bool multifd_queue_page(RAMBlock *block, ram_addr_t offset)
{
MultiFDPages_t *pages;
retry:
pages = multifd_send_state->pages;
/* If the queue is empty, we can already enqueue now */
if (multifd_queue_empty(pages)) {
pages->block = block;
multifd_enqueue(pages, offset);
return true;
}
/*
* Not empty, meanwhile we need a flush. It can because of either:
*
* (1) The page is not on the same ramblock of previous ones, or,
* (2) The queue is full.
*
* After flush, always retry.
*/
if (pages->block != block || multifd_queue_full(pages)) {
if (!multifd_send_pages()) {
return false;
}
goto retry;
}
/* Not empty, and we still have space, do it! */
multifd_enqueue(pages, offset);
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.
*
* TODO: p->running is still buggy, e.g. we can reach here without the
* corresponding multifd_new_send_channel_async() get invoked yet,
* then a new thread can even be created after this function returns.
*/
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
if (p->running) {
qemu_thread_join(&p->thread);
}
}
}
static int multifd_send_channel_destroy(QIOChannel *send)
{
return socket_send_channel_destroy(send);
}
static bool multifd_send_cleanup_channel(MultiFDSendParams *p, Error **errp)
{
if (p->registered_yank) {
migration_ioc_unregister_yank(p->c);
}
multifd_send_channel_destroy(p->c);
p->c = NULL;
qemu_sem_destroy(&p->sem);
qemu_sem_destroy(&p->sem_sync);
g_free(p->name);
p->name = NULL;
multifd_pages_clear(p->pages);
p->pages = NULL;
p->packet_len = 0;
g_free(p->packet);
p->packet = NULL;
g_free(p->iov);
p->iov = NULL;
multifd_send_state->ops->send_cleanup(p, errp);
return *errp == NULL;
}
static void multifd_send_cleanup_state(void)
{
qemu_sem_destroy(&multifd_send_state->channels_ready);
g_free(multifd_send_state->params);
multifd_send_state->params = NULL;
multifd_pages_clear(multifd_send_state->pages);
multifd_send_state->pages = 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;
if (!migrate_multifd()) {
return 0;
}
if (multifd_send_state->pages->num) {
if (!multifd_send_pages()) {
error_report("%s: multifd_send_pages fail", __func__);
return -1;
}
}
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;
thread = migration_threads_add(p->name, qemu_get_thread_id());
trace_multifd_send_thread_start(p->id);
rcu_register_thread();
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->pages. Pairs with the
* qatomic_store_release() in multifd_send_pages().
*/
if (qatomic_load_acquire(&p->pending_job)) {
MultiFDPages_t *pages = p->pages;
p->iovs_num = 0;
assert(pages->num);
ret = multifd_send_state->ops->send_prepare(p, &local_err);
if (ret != 0) {
break;
}
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);
multifd_pages_reset(p->pages);
p->next_packet_size = 0;
/*
* Making sure p->pages is published before saying "we're
* free". Pairs with the smp_mb_acquire() in
* multifd_send_pages().
*/
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));
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);
}
p->running = false;
rcu_unregister_thread();
migration_threads_remove(thread);
trace_multifd_send_thread_end(p->id, p->packets_sent, p->total_normal_pages);
return NULL;
}
static bool multifd_channel_connect(MultiFDSendParams *p,
QIOChannel *ioc,
Error **errp);
static void multifd_tls_outgoing_handshake(QIOTask *task,
gpointer opaque)
{
MultiFDSendParams *p = opaque;
QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task));
Error *err = NULL;
if (!qio_task_propagate_error(task, &err)) {
trace_multifd_tls_outgoing_handshake_complete(ioc);
if (multifd_channel_connect(p, ioc, &err)) {
return;
}
}
trace_multifd_tls_outgoing_handshake_error(ioc, error_get_pretty(err));
multifd_send_set_error(err);
multifd_send_kick_main(p);
error_free(err);
}
static void *multifd_tls_handshake_thread(void *opaque)
{
MultiFDSendParams *p = opaque;
QIOChannelTLS *tioc = QIO_CHANNEL_TLS(p->c);
qio_channel_tls_handshake(tioc,
multifd_tls_outgoing_handshake,
p,
NULL,
NULL);
return NULL;
}
static bool multifd_tls_channel_connect(MultiFDSendParams *p,
QIOChannel *ioc,
Error **errp)
{
MigrationState *s = migrate_get_current();
const char *hostname = s->hostname;
QIOChannelTLS *tioc;
tioc = migration_tls_client_create(ioc, hostname, errp);
if (!tioc) {
return false;
}
object_unref(OBJECT(ioc));
trace_multifd_tls_outgoing_handshake_start(ioc, tioc, hostname);
qio_channel_set_name(QIO_CHANNEL(tioc), "multifd-tls-outgoing");
p->c = QIO_CHANNEL(tioc);
qemu_thread_create(&p->thread, "multifd-tls-handshake-worker",
multifd_tls_handshake_thread, p,
QEMU_THREAD_JOINABLE);
return true;
}
static bool multifd_channel_connect(MultiFDSendParams *p,
QIOChannel *ioc,
Error **errp)
{
trace_multifd_set_outgoing_channel(
ioc, object_get_typename(OBJECT(ioc)),
migrate_get_current()->hostname);
if (migrate_channel_requires_tls_upgrade(ioc)) {
/*
* tls_channel_connect will call back to this
* function after the TLS handshake,
* so we mustn't call multifd_send_thread until then
*/
return multifd_tls_channel_connect(p, ioc, errp);
}
migration_ioc_register_yank(ioc);
p->registered_yank = true;
p->c = ioc;
qemu_thread_create(&p->thread, p->name, multifd_send_thread, p,
QEMU_THREAD_JOINABLE);
return true;
}
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;
trace_multifd_new_send_channel_async(p->id);
if (!qio_task_propagate_error(task, &local_err)) {
qio_channel_set_delay(ioc, false);
p->running = true;
if (multifd_channel_connect(p, ioc, &local_err)) {
return;
}
}
trace_multifd_new_send_channel_async_error(p->id, local_err);
multifd_send_set_error(local_err);
multifd_send_kick_main(p);
object_unref(OBJECT(ioc));
error_free(local_err);
}
static void multifd_new_send_channel_create(gpointer opaque)
{
socket_send_channel_create(multifd_new_send_channel_async, opaque);
}
int multifd_send_setup(Error **errp)
{
int thread_count;
uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
uint8_t i;
if (!migrate_multifd()) {
return 0;
}
thread_count = migrate_multifd_channels();
multifd_send_state = g_malloc0(sizeof(*multifd_send_state));
multifd_send_state->params = g_new0(MultiFDSendParams, thread_count);
multifd_send_state->pages = multifd_pages_init(page_count);
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];
qemu_sem_init(&p->sem, 0);
qemu_sem_init(&p->sem_sync, 0);
p->id = i;
p->pages = multifd_pages_init(page_count);
p->packet_len = sizeof(MultiFDPacket_t)
+ sizeof(uint64_t) * page_count;
p->packet = g_malloc0(p->packet_len);
p->packet->magic = cpu_to_be32(MULTIFD_MAGIC);
p->packet->version = cpu_to_be32(MULTIFD_VERSION);
p->name = g_strdup_printf("multifdsend_%d", i);
/* We need one extra place for the packet header */
p->iov = g_new0(struct iovec, page_count + 1);
p->page_size = qemu_target_page_size();
p->page_count = page_count;
p->write_flags = 0;
multifd_new_send_channel_create(p);
}
for (i = 0; i < thread_count; i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
int ret;
ret = multifd_send_state->ops->send_setup(p, errp);
if (ret) {
return ret;
}
}
return 0;
}
struct {
MultiFDRecvParams *params;
/* number of created threads */
int count;
/* syncs main thread and channels */
QemuSemaphore sem_sync;
/* global number of generated multifd packets */
uint64_t packet_num;
/* multifd ops */
MultiFDMethods *ops;
} *multifd_recv_state;
static void multifd_recv_terminate_threads(Error *err)
{
int i;
trace_multifd_recv_terminate_threads(err != NULL);
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];
qemu_mutex_lock(&p->mutex);
p->quit = true;
/*
* 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);
}
qemu_mutex_unlock(&p->mutex);
}
}
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);
g_free(p->name);
p->name = NULL;
p->packet_len = 0;
g_free(p->packet);
p->packet = NULL;
g_free(p->iov);
p->iov = NULL;
g_free(p->normal);
p->normal = 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);
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->running) {
/*
* multifd_recv_thread may hung at MULTIFD_FLAG_SYNC handle code,
* however try to wakeup it without harm in cleanup phase.
*/
qemu_sem_post(&p->sem_sync);
}
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 i;
if (!migrate_multifd()) {
return;
}
for (i = 0; i < migrate_multifd_channels(); i++) {
MultiFDRecvParams *p = &multifd_recv_state->params[i];
trace_multifd_recv_sync_main_wait(p->id);
qemu_sem_wait(&multifd_recv_state->sem_sync);
}
for (i = 0; i < migrate_multifd_channels(); 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;
int ret;
trace_multifd_recv_thread_start(p->id);
rcu_register_thread();
while (true) {
uint32_t flags;
if (p->quit) {
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;
qemu_mutex_unlock(&p->mutex);
if (p->normal_num) {
ret = multifd_recv_state->ops->recv_pages(p, &local_err);
if (ret != 0) {
break;
}
}
if (flags & MULTIFD_FLAG_SYNC) {
qemu_sem_post(&multifd_recv_state->sem_sync);
qemu_sem_wait(&p->sem_sync);
}
}
if (local_err) {
multifd_recv_terminate_threads(local_err);
error_free(local_err);
}
qemu_mutex_lock(&p->mutex);
p->running = false;
qemu_mutex_unlock(&p->mutex);
rcu_unregister_thread();
trace_multifd_recv_thread_end(p->id, p->packets_recved, p->total_normal_pages);
return NULL;
}
int multifd_recv_setup(Error **errp)
{
int thread_count;
uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
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);
qatomic_set(&multifd_recv_state->count, 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);
p->quit = false;
p->id = i;
p->packet_len = sizeof(MultiFDPacket_t)
+ sizeof(uint64_t) * page_count;
p->packet = g_malloc0(p->packet_len);
p->name = g_strdup_printf("multifdrecv_%d", i);
p->iov = g_new0(struct iovec, page_count);
p->normal = g_new0(ram_addr_t, page_count);
p->page_count = page_count;
p->page_size = qemu_target_page_size();
}
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;
int id;
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);
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->running = 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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