On Mon, Oct 27, 2025 at 04:41:09PM +0100, Juraj Marcin wrote: > From: Juraj Marcin <[email protected]> > > This patch addresses a TODO about moving postcopy_ram_listen_thread() to > postcopy file. Furthermore, this patch adds a pair of functions, > postcopy_incoming_setup() and postcopy_incoming_cleanup(), which sets up > and cleans the postcopy_ram_incoming state and the listen thread.
It would be great to separate code movements and changes. Meanwhile, this patch won't apply cleanly on top of the staging branch that I kept.. it'll be great if you could rebase this series to the branch when repost: https://gitlab.com/peterx/qemu/-/commits/staging > > Signed-off-by: Juraj Marcin <[email protected]> > --- > migration/migration.c | 2 +- > migration/postcopy-ram.c | 144 +++++++++++++++++++++++++++++++++++++++ > migration/postcopy-ram.h | 3 + > migration/savevm.c | 131 +---------------------------------- > 4 files changed, 150 insertions(+), 130 deletions(-) > > diff --git a/migration/migration.c b/migration/migration.c > index e9acd0f63b..8827884a15 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -892,7 +892,7 @@ process_incoming_migration_co(void *opaque) > * but managed to complete within the precopy period, we can use > * the normal exit. > */ > - postcopy_ram_incoming_cleanup(mis); > + postcopy_incoming_cleanup(mis); > } else if (ret >= 0) { > /* > * Postcopy was started, cleanup should happen at the end of the > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > index 5471efb4f0..dbbb2dfb78 100644 > --- a/migration/postcopy-ram.c > +++ b/migration/postcopy-ram.c > @@ -2077,3 +2077,147 @@ bool postcopy_is_paused(MigrationStatus status) > return status == MIGRATION_STATUS_POSTCOPY_PAUSED || > status == MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP; > } > + > +/* > + * Triggered by a postcopy_listen command; this thread takes over reading > + * the input stream, leaving the main thread free to carry on loading the > rest > + * of the device state (from RAM). > + */ > +static void *postcopy_listen_thread(void *opaque) > +{ > + MigrationIncomingState *mis = migration_incoming_get_current(); > + QEMUFile *f = mis->from_src_file; > + int load_res; > + MigrationState *migr = migrate_get_current(); > + Error *local_err = NULL; > + > + object_ref(OBJECT(migr)); > + > + migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE, > + MIGRATION_STATUS_POSTCOPY_ACTIVE); > + qemu_event_set(&mis->thread_sync_event); > + trace_postcopy_ram_listen_thread_start(); > + > + rcu_register_thread(); > + /* > + * Because we're a thread and not a coroutine we can't yield > + * in qemu_file, and thus we must be blocking now. > + */ > + qemu_file_set_blocking(f, true, &error_fatal); > + > + /* TODO: sanity check that only postcopiable data will be loaded here */ > + load_res = qemu_loadvm_state_main(f, mis, &local_err); > + > + /* > + * This is tricky, but, mis->from_src_file can change after it > + * returns, when postcopy recovery happened. In the future, we may > + * want a wrapper for the QEMUFile handle. > + */ > + f = mis->from_src_file; > + > + /* And non-blocking again so we don't block in any cleanup */ > + qemu_file_set_blocking(f, false, &error_fatal); > + > + trace_postcopy_ram_listen_thread_exit(); > + if (load_res < 0) { > + qemu_file_set_error(f, load_res); > + dirty_bitmap_mig_cancel_incoming(); > + if (postcopy_state_get() == POSTCOPY_INCOMING_RUNNING && > + !migrate_postcopy_ram() && migrate_dirty_bitmaps()) > + { > + error_report("%s: loadvm failed during postcopy: %d. All states " > + "are migrated except dirty bitmaps. Some dirty " > + "bitmaps may be lost, and present migrated dirty " > + "bitmaps are correctly migrated and valid.", > + __func__, load_res); > + load_res = 0; /* prevent further exit() */ > + } else { > + error_prepend(&local_err, > + "loadvm failed during postcopy: %d: ", load_res); > + migrate_set_error(migr, local_err); > + error_report_err(local_err); > + migrate_set_state(&mis->state, MIGRATION_STATUS_POSTCOPY_ACTIVE, > + MIGRATION_STATUS_FAILED); > + } > + } > + if (load_res >= 0) { > + /* > + * This looks good, but it's possible that the device loading in the > + * main thread hasn't finished yet, and so we might not be in 'RUN' > + * state yet; wait for the end of the main thread. > + */ > + qemu_event_wait(&mis->main_thread_load_event); > + } > + postcopy_incoming_cleanup(mis); Here I did notice that this replaced the old postcopy_ram_incoming_cleanup(). I'm just curious: is it needed to check postcopy-ram=on once more? The two callers of postcopy_incoming_cleanup() should always have postcopy-ram enabled, right? > + > + if (load_res < 0) { > + /* > + * If something went wrong then we have a bad state so exit; > + * depending how far we got it might be possible at this point > + * to leave the guest running and fire MCEs for pages that never > + * arrived as a desperate recovery step. > + */ > + rcu_unregister_thread(); > + exit(EXIT_FAILURE); > + } > + > + migrate_set_state(&mis->state, MIGRATION_STATUS_POSTCOPY_ACTIVE, > + MIGRATION_STATUS_COMPLETED); > + /* > + * If everything has worked fine, then the main thread has waited > + * for us to start, and we're the last use of the mis. > + * (If something broke then qemu will have to exit anyway since it's > + * got a bad migration state). > + */ > + bql_lock(); > + migration_incoming_state_destroy(); > + bql_unlock(); > + > + rcu_unregister_thread(); > + mis->have_listen_thread = false; > + postcopy_state_set(POSTCOPY_INCOMING_END); > + > + object_unref(OBJECT(migr)); > + > + return NULL; > +} > + > +int postcopy_incoming_setup(MigrationIncomingState *mis, Error **errp) > +{ > + /* > + * Sensitise RAM - can now generate requests for blocks that don't exist > + * However, at this point the CPU shouldn't be running, and the IO > + * shouldn't be doing anything yet so don't actually expect requests > + */ > + if (migrate_postcopy_ram()) { > + if (postcopy_ram_incoming_setup(mis)) { > + postcopy_ram_incoming_cleanup(mis); > + error_setg(errp, "Failed to setup incoming postcopy RAM blocks"); > + return -1; > + } > + } > + > + trace_loadvm_postcopy_handle_listen("after uffd"); > + > + if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_LISTEN, errp)) { > + return -1; > + } > + > + mis->have_listen_thread = true; > + postcopy_thread_create(mis, &mis->listen_thread, > + MIGRATION_THREAD_DST_LISTEN, > + postcopy_listen_thread, QEMU_THREAD_DETACHED); > + > + return 0; > +} > + > +int postcopy_incoming_cleanup(MigrationIncomingState *mis) > +{ > + int rc = 0; > + > + if (migrate_postcopy_ram()) { > + rc = postcopy_ram_incoming_cleanup(mis); > + } > + > + return rc; > +} > diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h > index ca19433b24..a080dd65a7 100644 > --- a/migration/postcopy-ram.h > +++ b/migration/postcopy-ram.h > @@ -199,4 +199,7 @@ bool postcopy_is_paused(MigrationStatus status); > void mark_postcopy_blocktime_begin(uintptr_t addr, uint32_t ptid, > RAMBlock *rb); > > +int postcopy_incoming_setup(MigrationIncomingState *mis, Error **errp); > +int postcopy_incoming_cleanup(MigrationIncomingState *mis); > + > #endif > diff --git a/migration/savevm.c b/migration/savevm.c > index 7b35ec4dd0..96a2699ca7 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -2087,112 +2087,6 @@ static int > loadvm_postcopy_ram_handle_discard(MigrationIncomingState *mis, > return 0; > } > > -/* > - * Triggered by a postcopy_listen command; this thread takes over reading > - * the input stream, leaving the main thread free to carry on loading the > rest > - * of the device state (from RAM). > - * (TODO:This could do with being in a postcopy file - but there again it's > - * just another input loop, not that postcopy specific) > - */ > -static void *postcopy_ram_listen_thread(void *opaque) > -{ > - MigrationIncomingState *mis = migration_incoming_get_current(); > - QEMUFile *f = mis->from_src_file; > - int load_res; > - MigrationState *migr = migrate_get_current(); > - Error *local_err = NULL; > - > - object_ref(OBJECT(migr)); > - > - migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE, > - MIGRATION_STATUS_POSTCOPY_ACTIVE); > - qemu_event_set(&mis->thread_sync_event); > - trace_postcopy_ram_listen_thread_start(); > - > - rcu_register_thread(); > - /* > - * Because we're a thread and not a coroutine we can't yield > - * in qemu_file, and thus we must be blocking now. > - */ > - qemu_file_set_blocking(f, true, &error_fatal); > - > - /* TODO: sanity check that only postcopiable data will be loaded here */ > - load_res = qemu_loadvm_state_main(f, mis, &local_err); > - > - /* > - * This is tricky, but, mis->from_src_file can change after it > - * returns, when postcopy recovery happened. In the future, we may > - * want a wrapper for the QEMUFile handle. > - */ > - f = mis->from_src_file; > - > - /* And non-blocking again so we don't block in any cleanup */ > - qemu_file_set_blocking(f, false, &error_fatal); > - > - trace_postcopy_ram_listen_thread_exit(); > - if (load_res < 0) { > - qemu_file_set_error(f, load_res); > - dirty_bitmap_mig_cancel_incoming(); > - if (postcopy_state_get() == POSTCOPY_INCOMING_RUNNING && > - !migrate_postcopy_ram() && migrate_dirty_bitmaps()) > - { > - error_report("%s: loadvm failed during postcopy: %d. All states " > - "are migrated except dirty bitmaps. Some dirty " > - "bitmaps may be lost, and present migrated dirty " > - "bitmaps are correctly migrated and valid.", > - __func__, load_res); > - load_res = 0; /* prevent further exit() */ > - } else { > - error_prepend(&local_err, > - "loadvm failed during postcopy: %d: ", load_res); > - migrate_set_error(migr, local_err); > - error_report_err(local_err); > - migrate_set_state(&mis->state, MIGRATION_STATUS_POSTCOPY_ACTIVE, > - MIGRATION_STATUS_FAILED); > - } > - } > - if (load_res >= 0) { > - /* > - * This looks good, but it's possible that the device loading in the > - * main thread hasn't finished yet, and so we might not be in 'RUN' > - * state yet; wait for the end of the main thread. > - */ > - qemu_event_wait(&mis->main_thread_load_event); > - } > - postcopy_ram_incoming_cleanup(mis); > - > - if (load_res < 0) { > - /* > - * If something went wrong then we have a bad state so exit; > - * depending how far we got it might be possible at this point > - * to leave the guest running and fire MCEs for pages that never > - * arrived as a desperate recovery step. > - */ > - rcu_unregister_thread(); > - exit(EXIT_FAILURE); > - } > - > - migrate_set_state(&mis->state, MIGRATION_STATUS_POSTCOPY_ACTIVE, > - MIGRATION_STATUS_COMPLETED); > - /* > - * If everything has worked fine, then the main thread has waited > - * for us to start, and we're the last use of the mis. > - * (If something broke then qemu will have to exit anyway since it's > - * got a bad migration state). > - */ > - bql_lock(); > - migration_incoming_state_destroy(); > - bql_unlock(); > - > - rcu_unregister_thread(); > - mis->have_listen_thread = false; > - postcopy_state_set(POSTCOPY_INCOMING_END); > - > - object_unref(OBJECT(migr)); > - > - return NULL; > -} > - > /* After this message we must be able to immediately receive postcopy data */ > static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis, > Error **errp) > @@ -2218,32 +2112,11 @@ static int > loadvm_postcopy_handle_listen(MigrationIncomingState *mis, > > trace_loadvm_postcopy_handle_listen("after discard"); > > - /* > - * Sensitise RAM - can now generate requests for blocks that don't exist > - * However, at this point the CPU shouldn't be running, and the IO > - * shouldn't be doing anything yet so don't actually expect requests > - */ > - if (migrate_postcopy_ram()) { > - if (postcopy_ram_incoming_setup(mis)) { > - postcopy_ram_incoming_cleanup(mis); > - error_setg(errp, "Failed to setup incoming postcopy RAM blocks"); > - return -1; > - } > - } > + int rc = postcopy_incoming_setup(mis, errp); > > - trace_loadvm_postcopy_handle_listen("after uffd"); > - > - if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_LISTEN, errp)) { > - return -1; > - } > - > - mis->have_listen_thread = true; > - postcopy_thread_create(mis, &mis->listen_thread, > - MIGRATION_THREAD_DST_LISTEN, > - postcopy_ram_listen_thread, QEMU_THREAD_DETACHED); > trace_loadvm_postcopy_handle_listen("return"); > > - return 0; > + return rc; > } > > static void loadvm_postcopy_handle_run_bh(void *opaque) > -- > 2.51.0 > -- Peter Xu
