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Szmigiero" , Fabiano Rosas , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= Subject: [PULL 18/42] migration: Add thread pool of optional load threads Date: Thu, 6 Mar 2025 15:13:54 +0100 Message-ID: <20250306141419.2015340-19-clg@redhat.com> In-Reply-To: <20250306141419.2015340-1-clg@redhat.com> References: <20250306141419.2015340-1-clg@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.133.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: "Maciej S. Szmigiero" Some drivers might want to make use of auxiliary helper threads during VM state loading, for example to make sure that their blocking (sync) I/O operations don't block the rest of the migration process. Add a migration core managed thread pool to facilitate this use case. The migration core will wait for these threads to finish before (re)starting the VM at destination. Reviewed-by: Fabiano Rosas Signed-off-by: Maciej S. Szmigiero Link: https://lore.kernel.org/qemu-devel/b09fd70369b6159c75847e69f235cb908b02570c.1741124640.git.maciej.szmigiero@oracle.com Signed-off-by: Cédric Le Goater --- include/migration/misc.h | 3 ++ include/qemu/typedefs.h | 2 + migration/migration.h | 5 +++ migration/savevm.h | 2 +- migration/migration.c | 2 +- migration/savevm.c | 95 +++++++++++++++++++++++++++++++++++++++- 6 files changed, 105 insertions(+), 4 deletions(-) diff --git a/include/migration/misc.h b/include/migration/misc.h index c660be80954abdd768e419d2ab892fc034c7349d..4c171f4e897e2bea9016a1559bef3e89c165b176 100644 --- a/include/migration/misc.h +++ b/include/migration/misc.h @@ -45,9 +45,12 @@ bool migrate_ram_is_ignored(RAMBlock *block); /* migration/block.c */ AnnounceParameters *migrate_announce_params(void); + /* migration/savevm.c */ void dump_vmstate_json_to_file(FILE *out_fp); +void qemu_loadvm_start_load_thread(MigrationLoadThread function, + void *opaque); /* migration/migration.c */ void migration_object_init(void); diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h index 3d84efcac47a2f1a34f177a1ed0df5aeae04fdb3..fd23ff7771b1bd6cd51f48bbc5be86aa57982307 100644 --- a/include/qemu/typedefs.h +++ b/include/qemu/typedefs.h @@ -131,5 +131,7 @@ typedef struct IRQState *qemu_irq; * Function types */ typedef void (*qemu_irq_handler)(void *opaque, int n, int level); +typedef bool (*MigrationLoadThread)(void *opaque, bool *should_quit, + Error **errp); #endif /* QEMU_TYPEDEFS_H */ diff --git a/migration/migration.h b/migration/migration.h index 7b4278e2a32b2044fad4cf7f7a5defd4435333ea..d53f7cad84d8e4a8bd8546f94d635c9733d71961 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -43,6 +43,7 @@ #define MIGRATION_THREAD_DST_PREEMPT "mig/dst/preempt" struct PostcopyBlocktimeContext; +typedef struct ThreadPool ThreadPool; #define MIGRATION_RESUME_ACK_VALUE (1) @@ -187,6 +188,10 @@ struct MigrationIncomingState { Coroutine *colo_incoming_co; QemuSemaphore colo_incoming_sem; + /* Optional load threads pool and its thread exit request flag */ + ThreadPool *load_threads; + bool load_threads_abort; + /* * PostcopyBlocktimeContext to keep information for postcopy * live migration, to calculate vCPU block time diff --git a/migration/savevm.h b/migration/savevm.h index cb58434a9437f7f9752ae7ae02981e9927d4ce85..138c39a7f9f97f69957eac63f338e4807bd7e8c5 100644 --- a/migration/savevm.h +++ b/migration/savevm.h @@ -64,7 +64,7 @@ void qemu_savevm_live_state(QEMUFile *f); int qemu_save_device_state(QEMUFile *f); int qemu_loadvm_state(QEMUFile *f); -void qemu_loadvm_state_cleanup(void); +void qemu_loadvm_state_cleanup(MigrationIncomingState *mis); int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis); int qemu_load_device_state(QEMUFile *f); int qemu_loadvm_approve_switchover(void); diff --git a/migration/migration.c b/migration/migration.c index 0bf70ea9717d73b0816f6ae52b99ae67924e8030..1833cfe3580cd6e587c6c7cb754458c34baf61e8 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -419,7 +419,7 @@ void migration_incoming_state_destroy(void) * BQL and retake unconditionally. */ assert(bql_locked()); - qemu_loadvm_state_cleanup(); + qemu_loadvm_state_cleanup(mis); if (mis->to_src_file) { /* Tell source that we are done */ diff --git a/migration/savevm.c b/migration/savevm.c index 3e86b572cfa82c201b1bf935080a2e0ca651be0e..1abc365570e324dd85f8a95adeb1a95f57b73264 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -54,6 +54,7 @@ #include "qemu/job.h" #include "qemu/main-loop.h" #include "block/snapshot.h" +#include "block/thread-pool.h" #include "qemu/cutils.h" #include "io/channel-buffer.h" #include "io/channel-file.h" @@ -131,6 +132,35 @@ static struct mig_cmd_args { * generic extendable format with an exception for two old entities. */ +/***********************************************************/ +/* Optional load threads pool support */ + +static void qemu_loadvm_thread_pool_create(MigrationIncomingState *mis) +{ + assert(!mis->load_threads); + mis->load_threads = thread_pool_new(); + mis->load_threads_abort = false; +} + +static void qemu_loadvm_thread_pool_destroy(MigrationIncomingState *mis) +{ + qatomic_set(&mis->load_threads_abort, true); + + bql_unlock(); /* Load threads might be waiting for BQL */ + g_clear_pointer(&mis->load_threads, thread_pool_free); + bql_lock(); +} + +static bool qemu_loadvm_thread_pool_wait(MigrationState *s, + MigrationIncomingState *mis) +{ + bql_unlock(); /* Let load threads do work requiring BQL */ + thread_pool_wait(mis->load_threads); + bql_lock(); + + return !migrate_has_error(s); +} + /***********************************************************/ /* savevm/loadvm support */ @@ -2783,16 +2813,68 @@ static int qemu_loadvm_state_setup(QEMUFile *f, Error **errp) return 0; } -void qemu_loadvm_state_cleanup(void) +struct LoadThreadData { + MigrationLoadThread function; + void *opaque; +}; + +static int qemu_loadvm_load_thread(void *thread_opaque) +{ + struct LoadThreadData *data = thread_opaque; + MigrationIncomingState *mis = migration_incoming_get_current(); + g_autoptr(Error) local_err = NULL; + + if (!data->function(data->opaque, &mis->load_threads_abort, &local_err)) { + MigrationState *s = migrate_get_current(); + + /* + * Can't set load_threads_abort here since processing of main migration + * channel data could still be happening, resulting in launching of new + * load threads. + */ + + assert(local_err); + + /* + * In case of multiple load threads failing which thread error + * return we end setting is purely arbitrary. + */ + migrate_set_error(s, local_err); + } + + return 0; +} + +void qemu_loadvm_start_load_thread(MigrationLoadThread function, + void *opaque) +{ + MigrationIncomingState *mis = migration_incoming_get_current(); + struct LoadThreadData *data; + + /* We only set it from this thread so it's okay to read it directly */ + assert(!mis->load_threads_abort); + + data = g_new(struct LoadThreadData, 1); + data->function = function; + data->opaque = opaque; + + thread_pool_submit_immediate(mis->load_threads, qemu_loadvm_load_thread, + data, g_free); +} + +void qemu_loadvm_state_cleanup(MigrationIncomingState *mis) { SaveStateEntry *se; trace_loadvm_state_cleanup(); + QTAILQ_FOREACH(se, &savevm_state.handlers, entry) { if (se->ops && se->ops->load_cleanup) { se->ops->load_cleanup(se->opaque); } } + + qemu_loadvm_thread_pool_destroy(mis); } /* Return true if we should continue the migration, or false. */ @@ -2943,6 +3025,7 @@ out: int qemu_loadvm_state(QEMUFile *f) { + MigrationState *s = migrate_get_current(); MigrationIncomingState *mis = migration_incoming_get_current(); Error *local_err = NULL; int ret; @@ -2952,6 +3035,8 @@ int qemu_loadvm_state(QEMUFile *f) return -EINVAL; } + qemu_loadvm_thread_pool_create(mis); + ret = qemu_loadvm_state_header(f); if (ret) { return ret; @@ -2983,12 +3068,18 @@ int qemu_loadvm_state(QEMUFile *f) /* When reaching here, it must be precopy */ if (ret == 0) { - if (migrate_has_error(migrate_get_current())) { + if (migrate_has_error(migrate_get_current()) || + !qemu_loadvm_thread_pool_wait(s, mis)) { ret = -EINVAL; } else { ret = qemu_file_get_error(f); } } + /* + * Set this flag unconditionally so we'll catch further attempts to + * start additional threads via an appropriate assert() + */ + qatomic_set(&mis->load_threads_abort, true); /* * Try to read in the VMDESC section as well, so that dumping tools that -- 2.48.1